Finding the "SUV" of Bikes

[EarthlyTulip]

Hi! I've ridden bikes throughout the years, and when I first tried electric bikes, it was absolutely amazing coming from acoustic bikes. However, now I'm a lot larger (500 pounds, a good majority of it is in my legs if that'll mean anything) so I have some questions.

How durable are steel and titanium bike frames? I remember reading in different places on here and in other places that its the wheels that you need to worry about the most because spokes break, and my bike shop made sure that I mainly got steel frames for the acoustic bikes I have (the important bikes I have are a 2009 black kona africa bike 3 and a 2014 green surly pugsley fat bike (i'm pretty sure those are the right years lol)).

I know bike parts break often the higher you go up in weight, and I dealt with that when I was much smaller. Is there anything that is extremely durable when it comes to bike parts (like chains, cassettes, chainrings, pedal cranks, etc)? Can any of them handle significantly more torque, or would I just have to buy what's out there and always have a spare for when it breaks? If I have to DIY it or get it custom, I wouldn't necessarily mind.

As for wheels, I talked to Grin last year via email and I stopped replying at the time because they didn't have their all-axle fat bike motor ready to fit on my older bike. They said they had wheels that have carried 900 pounds of stuff before, which made me feel like there was definitely a chance for me to get back into traveling via bike again. Any insight anyone has on wheels would also be appreciated, as the best I remember is that I want to get as many double-butted spokes as possible on a hub/rim.

Is there any suspension that would bring any benefit for me? Every popular piece of suspension I have looked at wouldn't've even worked when I was smaller and still on bikes. The weight limits would just make the suspension bottom out, and probably put more stress on the frame lol.

My use case is focused on commuting in all and any weather to get home. I've biked in -50F/-45C with headwind chill (without it, it was like -12F/-24C, which would have been wayyyyyyyy better). It was absoilutely insane but, if I was even more prepared than I thought I was for my hands to get cold with the gear I had, I would've been way better as I got home. I mainly did this at 20-25ish mi/h (32-40ish km/h), and I'd prefer to keep it around 20mi/hr. Base weight not including the bike will be 500 pounds, and I'd want as much headroom as possible (900 pounds on two wheels would be amazing, but I think 650 is more "reasonable") for weight limits because I'm not getting any smaller at this moment in time, and I love biking as exercise and want to do it again without the the inconvience of going to the gym.

I will probably take on a trail or two in the future, no crazy jumps, but just want to try it for fun without needing a specific mountain bike.

I'm not really worried about battery life because I already have a 1kw battery that lasted me about 35 miles per charge. I can get more batteries in the future.

I probably will eventually get a trailer for groceries, basically my goal is to kind of an absolute tank of an "SUV" of bikes.

 

[bananu7]

A quick search brings up Clydesdale BFG - 32 inch wheel bicycle or 36er bike and Bikes For Bigger People - those advertise as supporting 450lbs and 500lbs respectively.

It becomes a bit easier if you go for a trike: 550lbs Archives | ZIZE Bikes
Those look about perfect for your needs, and a trike kinda fits the "SUV" description. Adding an electric drive to those doesn't seem impossible, especially considering they already have a lot of space underneath the seat.

Edit: just realized that ZIZE also has an electrified version: 3 Wheel Electric Bike for Personal Activity | ZIZE Bikes
The price is a bit steep, but it's a pretty rare thing, I suppose. Alternatively getting the $1.1k trike from BFBP and adding an electric drive to it will surely be much cheaper.

Edit2: and this seems to be the same model: Personal Activity Vehicle PAV3-3CB LIGHTNING Electric

 

[rafalg]

@EarthlyTulip I think it matters if youre rather tall, or rather wide?
I'd check big BMX bikes, they've got really bombproof frames and wheels (even 29'), however there might be a problem with finding frame big enough.
And it will reduce strain on the chain and sprockets if you go bigger size chainring and rear sprockets - i think 2x10 Shimano Tiagra or 105 is nice if you're strong and do a lot of riding.
And I'd consider geared hub motor, maybe even in front wheel - this way propelling forces would be distributed between 2 wheels (if you include your own pedaling), which might make everything wear more evenly and help with the handling on trails.
PS i would skip suspension, go for bigger tires instead. And brakes... hydraulic MTB disk brakes are nice, but good road rim brakes work well too (shimano 105 etc - they got the stopping power, but have some limits regarding tire size).

 

[offGridDownUnder]

Maybe in your orbit?

https://greenspeed-trikes.com/trikes/magnum-xl/

For a trike like this, you can put a Grin All-Axle hub motor in both of the front wheels with minimal changes to the rest of the drive train.

 

[Chalo]

I've spent time as a daily cycle commuter over 400 pounds, and I can affirm you have a special technical challenge.

You should recoil from anything lightweight or fashionable like it's on fire. Think of your requirements in terms of pounds of bike per pounds of you. Your version of a 16 pounds, lean mean racing road bike would be 50 pounds. Most tandem bikes wouldn't be built to accommodate you.

Things you should have special concern about:

Cranks. Use tubular chromoly BMX cranks. I lost all my front teeth to a top-of-the-line mountain bike bottom bracket, and I got a pretty fat settlement from Shimano eventually. It wasn't worth it.

Handlebars and stem. Here BMX and freestyle stuff also shines.

Forks. Bigger diameter steer tube is better, steel is better, heavier is better. If you demand suspension, use a true downhill racing or dirt jumping fork rather than cosplay stuff.

Wheels. 48 spoke wheels are out of fashion, but still an excellent choice for you and me. Fatbike rims with double wall construction are a great choice if they fit in your intended frame, even if they're only 32 or 36 spoke. Rims marketed for cargo bikes or pedicabs are applicable too. Don't fool around with 9-10-11-12-13 speed nonsense. 5, 6, 7 or 8. You can get all the gear range you need without signing up for fast wearing, expensive to replace consumer nonsense.

If you want a ready made solution, consider buying a longtail cargo bike like Radwagon. It's designed to carry about as much weight as you alone, it isn't horrifyingly expensive or cheesy, and it has a decenttrack record. Also it does a great job of distributing your weight evenly between front and rear wheels.

Don't let anybody tell you to use a mid drive. That's a trail of tears for you. Just don't. A huge high torque hub motor in the rear, or a smaller one in each wheel. Don't accept the shabby build quality or grossly oversized spokes that come with pre-built hub motor wheels. You need massive rims, thin spokes, high spoke tension, and expert build quality.

 

[Chalo]

Maybe in your orbit?

https://greenspeed-trikes.com/trikes/magnum-xl/

I'd recommend something like that for a disabled person, but not for a heavy but fully abled person.

I even have a similar one waiting for me, for when my miseries increase past some inflection point.

 

[EarthlyTulip]

A quick search brings up Clydesdale BFG - 32 inch wheel bicycle or 36er bike and Bikes For Bigger People - those advertise as supporting 450lbs and 500lbs respectively. [...]

These seem decent and I remember coming across these. My biggest issue is that I'm right around treading the line with those weight limits or I'm breaking the bike (or at least, I'd be very terrified of breaking the bike at 20 mi/hr).

With Zize, waiting 3 months minimum after a $5K USD purchase is absolutely insane, and even at 3K I'd want it at least within the month. The trikes don't look bad, I'm just not a big fan of how these are more of the low riding style. I feel like I'd have to try this style before I rule it out completely or buy it, and I unfortunately didn't do that when I was smaller.

Workman and the BFG seems decent, but I'm still running into the weight issues as I'm right at that limit (or above the limit with the BFG). The PAV doesn't fit my use case, as I can definitely pedal at their recommended top speed of 10mi/hr with no issues. I'll probably keep them in mind as I look through more things if I can't do it on two wheels.

Also, why would Workman's drum brakes, and upgraded tires and tubes make the bike more durable (they're claiming that regular stuff is 275, but the upgrades make it up to 500)? It would make sense if they're changing out the spokes in the wheels, but then if I just need better wheels, why wouldn't I just upgrade my current bikes?

Is Workman and Zize sister companies, or something? I've seen them have some of the same images or the same bikes over time.

 

[EarthlyTulip]

I think it matters if youre rather tall, or rather wide?
I'd check big BMX bikes, they've got really bombproof frames and wheels (even 29'), however there might be a problem with finding frame big enough. [...]

I am both, 6 feet tall (~182cm) and my legs/butt are the biggest parts of my body. I'll search youtube for BMX bikes.

What would you say classifies as bombproof? Grin's website also claims the same thing about their wheels, so I'm wondering what would be the differences when I go with them wheel-wise?

I would have to look into the drivetrains as well. Biking was my only way of commuting for a while, so I probably still have a decent amount of muscle from that.

Wouldn't the direct drive motors also have the same benefit to the geared hub motors? Why would it be different based on the style of hub motor if it's in the same spot (front or rear)?

I'll probably end up skipping suspension if I can't find like a motorcycle rated one that holds like 700 pounds lol. It would be expensive, and my hardtails are fine. The wider/bigger tires are a very small benefit to have sudo suspension, its also another reason why I like fat bikes lol

Maybe in your orbit?

https://greenspeed-trikes.com/trikes/magnum-xl/

For a trike like this, you can put a Grin All-Axle hub motor in both of the front wheels with minimal changes to the rest of the drive train.

I can already tell that I will never, ever fit in that seat! LOL the seat is way too narrow, and the pictures they have up for display, my body would be rubbing against the handles like tomorrow never existed! The same issues I have with the weight limits and me not having tried a trike exist here as well.

 

[neptronix]

Some cargo bikes are known to handle mondo amounts of weight.

A custom frame is advisable though, very few rated for 500lbs.

 

[offGridDownUnder]

What would you say classifies as bombproof? Grin's website also claims the same thing about their wheels, so I'm wondering what would be the differences when I go with them wheel-wise?

Ask them. Maybe they'll warrantee it for your stated weight.

 

[EarthlyTulip]

I've spent time as a daily cycle commuter over 400 pounds, and I can affirm you have a special technical challenge.

You should recoil from anything lightweight or fashionable like it's on fire. Think of your requirements in terms of pounds of bike per pounds of you. Your version of a 16 pounds, lean mean racing road bike would be 50 pounds. Most tandem bikes wouldn't be built to accommodate you. [...]

I have definitely recoil-ed, especially when looking at all the carbon fiber and cargo bike stuff! Weeding through that mess hasn't been great, and this place has been the only good place of information I've really been able to find. I'm surprised that most tandems wouldn't hold me either, they're mainly built for two decently sized people, no? I haven't really looked into it though as I don't want a person with me on the same bike unless they're in a trailer behind me.

Losing your teeth like that sucks a lot, I'm sorry it happened but I'm glad Shimano paid you well at least.

I will definitely get BMX stuff then! I haven't looked into it yet but this is really helpful, thank you.

What would you say is a decent/bigger sized diameter steer tube?

How fast do the 9 through 13 speeds break? I know it breaks faster due to the weight and whatnot, but did you run through those like water because they're that easy to break? My old bike has a 10 speed, I don't mind changing it out, but I'm curious lol.

The Radwagons look decent, but my issue is that I know I'd at least need to get better wheels because their weight limits are severely low comparatively to my weight (the ones I found on their website were having max rider weights at the 300ish pound mark), and I'd be too scared to ride the thing. I don't mind DIYing and getting a setup from Grin for a fatbike/any bike, it's still expensive but I think I'd have a little more confidence in it working

I already had my issues with a mid drive when I was smaller, I definitely don't want them happening again LOL. It sucked a lot and it was a decent money sink that wasn't worth it.

Some cargo bikes are known to handle mondo amounts of weight.

A custom frame is advisable though, very few rated for 500lbs.

Do you have any frame builder recommendations?

 

[rafalg]

@EarthlyTulip I mentioned BMX because they have sturdy steel frames (not very lightweight) and strong wheels with denser spokes /double walled rims. The downside is that they're single speed, the system for attaching wheels is primitive, and they are usually short (wheelbase) - but maybe someone builds 'normal sized' frames this way.
There are some custom frame builders like Lairdframe | BMX Frames - maybe you can find someone close to you..

 

[neptronix]

Do you have any frame builder recommendations?

No, but this guy in Peru is highly recommended by Reddit and can likely build you a frame with very thick tubing and other things oversized (headtube, bb, seat post, etc ) to help handle the weight.
Probably want 48 spoke wheels too.

- MarinoBike

 

[marvin78]

The first thing which popped into my mind when reading this thread tittle was: Who in their right mind would want an 'SUV' kind of bike, aren't we on bikes to escape the SUV's?

Then I realized there is a reason you want the 'SUV' among bikes, and I felt pretty stupid.

I don't have anything to contribute other then that. I mean, the strongest cargo bikes on two wheels I've seen are those Surly cargo bikes, but I don't think they would do the trick for you.

Good luck in your endavour, I will gladly follow this thread to see what you end up with. I hope you will figure it out and be able to enjoy cycling for a long time to come.

 

[Chalo]

Schauff Sumo is another commercial model from Germany that's specifically designed for big ole hosses.

I wouldn't be too concerned about regular frames and forks, as long as you're picking from the heavy pile. I have had good luck with relatively flimsy '70s and '80s steel frames, as long as I fit them with BMX cranks, heavy duty wheels, and good strong handlebars and stem (usually BMX or old skool MTB, sometimes motocross or ATV). If you're of ordinary height or shorter, you could use a downhill, freeride, dirt jumping, or big wheel freestyle frame which should work great for a super heavyweight if you're not doing those things with it. But because I'm 6'8", I have to use frames that approximately fit me, and retrofit them as much as I can.

If you need more than a few inches of seatpost sticking out, you may need a special seatpost. I've made solid ones for myself when I had to use long extension. I've also used materials like thick walled chromoly tubing and 7075-T6 aluminum. Thomson Elite seatposts are the strongest commercial ones I've used, but at your weight, I would not stick them very far out of the frame.

Fork steer tubes come in diameters as small as 25mm (French), and in ascending order 1", 1.125", 1.25", 1.125" to 1.5" tapered, and 1.5" straight. There were a few oddballs like 1" to 1.25" tapered, and 1.5625", but those aren't around any more. There's also a 1.125" to 1.8" tapered size, but I don't think anybody should encourage those dingdongs by buying their silly stuff.

Some 1.125" forks were made for extreme foolhardy activities, and are built accordingly. But lately that's just the default size for basic bikes. 1.125" to 1.5" tapered has become the go-to standard for MTBs, and even forks with aluminum steer tubes in that size should be structurally adequate for you (though the suspension part may be nearly impossible to tune for your weight). 1.25" has some adoption among tandems, and tandem rated forks would pretty much all be appropriate for you. 1.5" straight, also called One Point Five, would be ideal, but there aren't many frames made to use them.

Tandems aren't all rated for your weight because sporting riders usually fall in the sub-200 lbs range, often very very sub-200. But because of the tandem long wheelbase that's resistant to tipping up, the forks need to be extra strong and will work for you. But other than tandem rated forks, frames, and wheels, other tandem components are designed to support one regular sized person.

The more speeds you have on the rear, the less area you have on each sprocket tooth and chain link to carry the load, so they wear out faster even though higher gear counts must be made of harder and more expensive materials. Also the sprockets become thinner and easier to bend.

If you use 7 speeds or fewer, you can benefit from decreased wheel dish and have a stronger rear wheel with the same components. 8-9-10 speeds use the same spacing and have the same dish. 11-12-13 use progressively wider cassettes and thus push wheel dish to the extreme. Tandem specific hubs usually have wider than normal axle spacing, so the left side can be offset similarly to the cassette side, to minimize dish.

There are good reasons for a heavy rider to use 7-speed cassettes on a 7-speed freehub body, but your available gearing range will be comparatively limited. For instance, 11-34t is a wide range for 7sp, but 8-speed cassettes are easy and cheap to find in 12-46t. Drop below 7 speed, and you'll be using freewheels rather than cassettes, most commonly only 14-28t overall. That's only a 2:1 range, so it diminishes the effectiveness of a single ring crank.

Halo SAS is a fantastic rim to consider if you want something of relatively normal width and not-extravagant weight. Those hold up in pedicab use where each wheel can carry 700 lbs or more. They're available in 48 hole versions, unlike most of today's strongest rims.

I think you should concern yourself more with actual structural integrity than with weight ratings, because you're so many standard deviations from the norm that weight ratings don't mean that much. Anybody who's rating bike stuff 500 lbs or more has probably arrived at the number by a wild guess rather than through testing.

 

[offGridDownUnder]

Tandem specific hubs usually have wider than normal axle spacing

May I recommend that you look over the range of adapters for the Grin All-Axle hub motor?

Specifically as they accommodate several much-larger-than-ordinary hub widths, which may be of use to you, and they have "Fat" versions of the motor. 190mm Quick-Release anyone?

 

[EarthlyTulip]

I mentioned BMX because they have sturdy steel frames (not very lightweight) and strong wheels with denser spokes /double walled rims. The downside is that they're single speed, the system for attaching wheels is primitive, and they are usually short (wheelbase) - but maybe someone builds 'normal sized' frames this way.
There are some custom frame builders like Lairdframe | BMX Frames - maybe you can find someone close to you..

That makes more sense, thank you for helping me understand more and thanks for the link! I definitely need way more than one gear though, the play I'm kinda thinking right now is to research how the bmx frames are made, and see if I can get a bike frame made with the same sturdiness, or see if there's already frames out there that can do the job. Depending on what happens, I might not necessarily need a custom frame, but everything's kinda up in the air right now.

Edit: Also if it is important, I forgot to mention while you were talking about brakes, that I've had no issues with any of the different types of breaks while riding that wasn't my own fault. At the time, it felt like they all would stop me with enough power for me to not be concerned about the types of brakes

No, but this guy in Peru is highly recommended by Reddit and can likely build you a frame with very thick tubing and other things oversized (headtube, bb, seat post, etc ) to help handle the weight.
Probably want 48 spoke wheels too.

- MarinoBike

Thanks for the link! I definitely want as many spokes as I can get! I'll probably have to ask grin if they can do a custom outer casing for more spokes.

The first thing which popped into my mind when reading this thread tittle was: Who in their right mind would want an 'SUV' kind of bike, aren't we on bikes to escape the SUV's? [...]

LOL Thanks! No reason to feel stupid!

I have a little bit of confidence in Surly's stuff, the pugsley held me up when I was in the 300 range. I could see myself getting a frame from them and building a bike, but it doesn't have to be specifically from them, I just know they use double butted steel.

My main goal is to figure this out by the end of the year (I'm learning a lot and every piece of information here has been helpful), hopefully by then I'll have pictures and/or information/specs of the bike I'll be using! I have a decent amount of confidence that I'll be able to ride again!

 

[amberwolf]

The first thing which popped into my mind when reading this thread tittle was: Who in their right mind would want an 'SUV' kind of bike, aren't we on bikes to escape the SUV's?

Yes, and no....for me: yes, I don't want anything like a giant metal cage...but, I regularly need to haul myself and big cargo (some of it wiggly), so my "SUV" trike the SB Cruiser makes sense for me.

My "SUV" bike, Crazybike2, also made sense (and it's replacement / successor that probably won't happen, the Cloudwalker Cargo Bike) for the same reasons.

Others have their own reasons for needing a bicycle or ebike version of an SUV; way bigger / more powerful than regular bikes or ebikes, but far far smaller than even a typical small car.

 

[EarthlyTulip]

Schauff Sumo is another commercial model from Germany that's specifically designed for big ole hosses.

I wouldn't be too concerned about regular frames and forks, as long as you're picking from the heavy pile. I have had good luck with relatively flimsy '70s and '80s steel frames, as long as I fit them with BMX cranks, heavy duty wheels, and good strong handlebars and stem (usually BMX or old skool MTB, sometimes motocross or ATV). If you're of ordinary height or shorter, you could use a downhill, freeride, dirt jumping, or big wheel freestyle frame which should work great for a super heavyweight if you're not doing those things with it. But because I'm 6'8", I have to use frames that approximately fit me, and retrofit them as much as I can.

If you need more than a few inches of seatpost sticking out, you may need a special seatpost. I've made solid ones for myself when I had to use long extension. I've also used materials like thick walled chromoly tubing and 7075-T6 aluminum. Thomson Elite seatposts are the strongest commercial ones I've used, but at your weight, I would not stick them very far out of the frame.

Fork steer tubes come in diameters as small as 25mm (French), and in ascending order 1", 1.125", 1.25", 1.125" to 1.5" tapered, and 1.5" straight. There were a few oddballs like 1" to 1.25" tapered, and 1.5625", but those aren't around any more. There's also a 1.125" to 1.8" tapered size, but I don't think anybody should encourage those dingdongs by buying their silly stuff.

Some 1.125" forks were made for extreme foolhardy activities, and are built accordingly. But lately that's just the default size for basic bikes. 1.125" to 1.5" tapered has become the go-to standard for MTBs, and even forks with aluminum steer tubes in that size should be structurally adequate for you (though the suspension part may be nearly impossible to tune for your weight). 1.25" has some adoption among tandems, and tandem rated forks would pretty much all be appropriate for you. 1.5" straight, also called One Point Five, would be ideal, but there aren't many frames made to use them.

Tandems aren't all rated for your weight because sporting riders usually fall in the sub-200 lbs range, often very very sub-200. But because of the tandem long wheelbase that's resistant to tipping up, the forks need to be extra strong and will work for you. But other than tandem rated forks, frames, and wheels, other tandem components are designed to support one regular sized person.

The more speeds you have on the rear, the less area you have on each sprocket tooth and chain link to carry the load, so they wear out faster even though higher gear counts must be made of harder and more expensive materials. Also the sprockets become thinner and easier to bend.

If you use 7 speeds or fewer, you can benefit from decreased wheel dish and have a stronger rear wheel with the same components. 8-9-10 speeds use the same spacing and have the same dish. 11-12-13 use progressively wider cassettes and thus push wheel dish to the extreme. Tandem specific hubs usually have wider than normal axle spacing, so the left side can be offset similarly to the cassette side, to minimize dish.

There are good reasons for a heavy rider to use 7-speed cassettes on a 7-speed freehub body, but your available gearing range will be comparatively limited. For instance, 11-34t is a wide range for 7sp, but 8-speed cassettes are easy and cheap to find in 12-46t. Drop below 7 speed, and you'll be using freewheels rather than cassettes, most commonly only 14-28t overall. That's only a 2:1 range, so it diminishes the effectiveness of a single ring crank.

Halo SAS is a fantastic rim to consider if you want something of relatively normal width and not-extravagant weight. Those hold up in pedicab use where each wheel can carry 700 lbs or more. They're available in 48 hole versions, unlike most of today's strongest rims.

I think you should concern yourself more with actual structural integrity than with weight ratings, because you're so many standard deviations from the norm that weight ratings don't mean that much. Anybody who's rating bike stuff 500 lbs or more has probably arrived at the number by a wild guess rather than through testing.

Their bikes look nice! I will keep that brand in mind

I'll do my best not to worry too much about the frame and fork. Getting a good steel frame and fitting it with good bmx parts does allow for way more options and would let me be able to use way more frames. I'm just terrified overall lol

It'd probably be better for safety measures to get a custom seatpost. Do I need to be concerned about the traditional saddle mounts (the two tiny bar things)? I definitely plan to get a much wider seat, I just didn't get that far with what I'd go with yet (and I assume it'll use the same mounting type).

This was really helpful, thanks again. I'll probably put the Halo SAS on the kona bike, that thing is way too heavy as a steel bike and I think I could do that and get another fat bike rolling (or use the current fat bike i have lol, undecided). The kona bike has an Shimano 3 speed IGH in it from "forever ago," do I need to worry about that breaking or messing up due to torque?

My brain tends to focus on the weight range because if I'm too heavy its out of warranty (I am too heavy though lol), and the heavier it's rated for, the more structurally sound I'd think or percieve it to be. Clearly I'm wrong, so I need to get out of my head. I'm gonna have to change things up on bikes to make it work for me anyways

 

[amberwolf]

My brain tends to focus on the weight range because if I'm too heavy its out of warranty (I am too heavy though lol), and the heavier it's rated for, the more structurally sound I'd think or percieve it to be. Clearly I'm wrong, so I need to get out of my head.

Keep in mind that many weight ratings for all sorts of things appear to be for a static load. Since that's not going to be the case unless the bike is parked with the load on it, the rated item could fail unexpectedly. For an item to have a useful weight rating, it has to provide the test conditions it was rated under, not just the weight itself, but the conditions--was it a static test, just sitting there increasing weight until it broke? Or was it tested under specific vertical accelerations, such as you really get while riding on a real road or path or sidewalk and go over bumps, etc? Was it tested with any sideways accelerations, as you will always have while pedalling, steering, etc? Was it tested with *both* things happening at the same time?

If it's just a static test...you'd have to derate it for reality, but by how much? Can't really know without...testing it.

(I've seen a lot of broken racks "rated" for way more than the weight actually put on them, because that rating was either made up or was tested only with a static vertical load...so I ended up building my own racks instead, that I could be certain wouldn't fail under any loading I would ever put them thru (which is...saying something, given the crap I've carried. ) Then I started building my own bikes/trikes/trailers because I was breaking them, too....

 

[marka-ee]

(I've seen a lot of broken racks "rated" for way more than the weight actually put on them, because that rating was either made up or was tested only with a static vertical load...

So true with these commercially available bike racks for their rear. They always look so good with those fat looking aluminum structural members, but they're actually more like soda straws and not really designed by an engineer. On a suspension mountain bike, I was using one of the racks that clamp onto the seat post to hold my battery and Those things are a joke. I finally ended up finding a 100% steel one and those are okay Aluminum just isn't right for all these tasks.

 

[rafalg]

I only paid attention to weight limit when buying carbon bikes, mostly because the number wasn't that far away from my weight. But the service guys told me this includes some abuse margin, quite wide in case of a MTB, so if i dont do jumps it will be fine even if my weight doubles.

 

[EarthlyTulip]

Keep in mind that many weight ratings for all sorts of things appear to be for a static load. Since that's not going to be the case unless the bike is parked with the load on it, the rated item could fail unexpectedly. For an item to have a useful weight rating, it has to provide the test conditions it was rated under, not just the weight itself, but the conditions--was it a static test, just sitting there increasing weight until it broke? Or was it tested under specific vertical accelerations, such as you really get while riding on a real road or path or sidewalk and go over bumps, etc? Was it tested with any sideways accelerations, as you will always have while pedalling, steering, etc? Was it tested with *both* things happening at the same time?

If it's just a static test...you'd have to derate it for reality, but by how much? Can't really know without...testing it.

(I've seen a lot of broken racks "rated" for way more than the weight actually put on them, because that rating was either made up or was tested only with a static vertical load...so I ended up building my own racks instead, that I could be certain wouldn't fail under any loading I would ever put them thru (which is...saying something, given the crap I've carried. ) Then I started building my own bikes/trikes/trailers because I was breaking them, too....

That kinda sucks... I thought it'd at least be a form of something like, "We tested this amount of weight in realistic conditions, and here's what we feel comfortable with warrantying." Contacting every manufacturer for how they conduct their weight limits would be horrible, especially considering how they can just corporate speak lie to people. I figured there was some type of standard testing methods but I was also wrong again...

To have broken racks rated higher than what was on them when they broke is insane. I would be so upset

Do you have a link where I can briefly look over some of your builds? I see your SB Cruiser but I was wondering what your other builds looked like and how much stuff they can hold

 

[amberwolf]

Do you have a link where I can briefly look over some of your builds? I see your SB Cruiser but I was wondering what your other builds looked like and how much stuff they can hold

Some links inline below. Feel free to ask any questions here or in those threads.


They're all built "from scratch", meaning using whatever junk and junk bike parts I had, and heavily modified over time based on results, failures, experiments, ideas, etc., until they did what I wanted.

For your purposes, the SB Cruiser is the only one I've actually built that I think could do it, with some modifications to the keel structure / rear-front interconnect. (which I haven't done because they'd be in my way, but are actually needed even for my usage). SBC can carry, in the cargo area, about 400lbs, plus my almost-200 on the seat in front of it. It can haul much more than that on a trailer (upright piano was probably the heaviest single thing so far), but that doesn't do you much good.



To do what you need it to, it needs to handle that on the seat itself, which I know the present keel design couldn't do. It would need a triangulated framework that feeds the loads from the keel into the rear frame, to handle both lateral and vertical bump and steer loading. A really good suspension would help a lot with that; I don't have suspension because it's too hard to come up with a good one I can build out of what I have that can be adjusted for the wide range of loading it would see (The front loading doesn't vary much on my usage, and I used to have a cheap susp fork but broke it in the only crash I've had with SBC so it's all unsuspended now). If your usage only really needs to carry you, then the load doesn't vary much and you can use a much more typical suspension design for the rear, and the front would work more like a regular suspension as well.


There's a MkII version I've worked out some ideas for, which will be adapted as much as possilbe using a customized versino of an ancient Schwinn trike here. I think that the larger-rear-wheel versions in these threads are a significant improvement over the small-wheel existing SBC, and the old Crazybike2.


CrazyBike2 evolved into something you might be able to adapt, as it became structurally stiff enough in the last version (would have had some further design work as the Cloudwalker Cargo Bike). Same suspension issues--you'd probably need it (I did too, but only had it in the front, same reasons as SBC). CB2 was, before SBC, my most-successful and most-used design. Like everything, it evolved thru breakage and failure into that. I'd guess that including my own weight, it could do maybe 300lbs on the back but 200 was the max I'd regularly carry back there; just not room for all that much (it used trailers for more); that was a significant part of why SBC got built, to give a bigger single-area cargo space. Doesn't seem to be that much a factor for your usage.


The Raine Trike was a side-build for my brother, but I don't know how well it would have worked because he never used it beyond the test rides.




There are other builds but none of them would do what you need; they're just "regular bikes" except for Delta Tripper, which was the failed precursor to SB Cruiser.

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[amberwolf]

That kinda sucks... I thought it'd at least be a form of something like, "We tested this amount of weight in realistic conditions, and here's what we feel comfortable with warrantying." Contacting every manufacturer for how they conduct their weight limits would be horrible, especially considering how they can just corporate speak lie to people. I figured there was some type of standard testing methods but I was also wrong again...

There *are* standard testing methods for these kinds of things...probably not specifically for racks and frames and whatnot, but simple engineering principles tests (no, I'm not an engineer, and I don't know specificaly what those would be), and all sorts of labs that do failure testing and analysis...but this stuff costs time and money, and it's apparently cheaper for them to replace the ones that do break, and pay off occasional lost lawsuits***, than to just design and test them properly in the first place. (failure analysis is one of my many "hobbies"; I'm no expert but I am fairly good at it for an armchair guy--I like doing it and I like reading / watching about others' analyses of various types of failures and chains of events leading up to them.)

The actual methods used for any test would have to be specified, as those could vary, but there are a number of basic tests that would have to be done to get useful results for realworld max loading ratings on structures.

If you assume specific methods used in construction and manufacture, you can calculate out all the max loads something can take, peak, and continuous, and under all sorts of conditions (there is even stress modelling software to help visualize it, some of it free), but that's normally only used for the original design, and not something you'd use the output of to put in your ads--it's probably not even available to the marketing department. You'd ideally use a realworld test to get the max ratings, but you could, if too cheap to do the testing, use the engineering numbers (if any were even ever generated...no guarantees on that) and reduce by some safety factor (say, by half) to ensure that anyone running near or at the max would still never ever have a problem. (the failures are never as simple as "oops exceeded that rating by 1PSI, bang it broke"...)

***for those that are actually in the US, or EU, etc., vs those in China/etc that are just going to ignore you or just plain disappear after a problem starts, etc., who don't have to even worry about either of those things.


If you poke around and look into it, you'll probably find that very few ratings of any kind on any device or thing have any basis in any testing at all--most of them appear to be made up by the ad copy writers because they had to put something there that makes it sell better. You'll also find "ratings" provided by "sales" and "support" departments that are also just made up, as those people dont usually actually know anything specific about what they're selling and supporting.


Some ratings have a basis in *a test* but not one with repeatable real-world conditions that are factored into the rating itself, or documented anywhere, such as some companies' battery-life "ratings" (for any battery powered device). Like that "2 weeks on a charge" you might see for some devices...sure, if you just charge it and let it sit there doing nothing until it's recharge light starts blinking--if you actually use it it lasts an hour or less. Or the "range" given for most ebikes (even of "reputable" brands!). Sure--the rating is "real" but since no conditions for the test were provided, you can't use that data to judge suitability for any purpose or usage.

To have broken racks rated higher than what was on them when they broke is insane. I would be so upset

Well, I never had anything new so there wasn't a warranty to worry about. :lol: I've discovered that virtually zero companies are interested in feedback to improve their products, so I don't bother doing that anymore. (might have back when I first broke racks if they'd been under some sort of warranty, but...).

Remember that any rating you see is almost certainly a static-load rating. So you can break things by using something well within that rating but applying a g-force to it that cuases the weight to far exceed that...but you didn't exceed the actual (static) rating. If there's no separate rating specifying

then there's the wiggle-rating, meaning what a rack would actually survive even without bumps if you wiggle it back and forth thousands of times...as will happen when you pedal, with every stroke. the farther to the rear the load is, the worse this problem is. The less-competently-designed the mounting and support framework is, the more likely it is that this will be a lower number of cycles.


EDIT: here's a link to the rack I built for a friend for his solid-tire bike that would really have beat up a regular one; it wasnt' finished yet and is just on one of my bikes to test the general fit before fully welding it up; i had ot wait till i had his bike to make the seatstay mounts. but it was "bulletproof". If I were to rate it like most ocmpanies do, i'd call it good for a hundred pounds or more. :lol: If it were made ot of good chromoly instead of crappy ex-retail-signage-fixtures, i'd double that.