40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by dogman dan » Dec 04 2020 6:26am

Hmm, while you are having fun talking tires, I'm thinking some places commuting 40 mph on bicycles would be suicide, and other places no problem. It just depends on the route you will be riding, how likely cars are to turn into your path thinking a bike goes 15 mph, oops, your doing 40, whack.

Anyway, it could be a much better plan to commute 40 mph on a motorcycle, that would look like it goes 40, or slow to 25-30 mph so your brakes and turning ability can still save your ass.

It just depends on the actual road, what the actual hazards are, particularly how many driveways or parking lot entrances you pass along the route while doing 40 mph. Over the 5 years I commuted on e bikes, I slowed down rather than sped up. The faster I rode, the more cars got in my way pulling out of driveways and such. And that commute had long safe stretches too. But I learned to slow way down by that Mcdonalds driveway, for example. I still ride like that past that place, on a 120 mph bmw. Some intersections just never safe, unless you are in a cement truck.

Re suspension, I would lean towards full suspension, but also suggest a lengthening plate on the rear to improve higher speed feel. You'll need a robust torque arm anyway, so why not a bike that can bolt on a better dropout plate that lengthens the bike 3 inches or so.

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by MadRhino » Dec 04 2020 9:45am

Chalo wrote:
Dec 03 2020 8:43pm
MadRhino wrote:
Dec 03 2020 6:25pm
Tires are not making suspension, because they have no negative travel.
Tires have static sag just like any other suspension. The late Jobst Brandt used to recommend using sag to decide what tire pressure to use. I think he recommended 20% of the unloaded casing height, which is not too far off what you'd use for a mechanical suspension.
... and that would make a nice 5/8 of an inch of negative ‘tire suspension’ travel, that would bounce back about 1 inch at 30 mph right? :roll:

Tire ‘sag’ must be set for proper grip and vibration absorption. When a tire is inflated too hard it does bounce 3 times the height of a hit, and transmits a lot of vibrations to the frame. When too soft, it will distort aside of the wheel axis in cornering, or pinch against the rim on any square hit. Ideal tire pressure is making it do its tire job properly, by spreading its correct contact patch under the average riding weight.
Make it fool-proof, and I will make a better fool.
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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by JackFlorey » Dec 04 2020 12:47pm

fatty wrote:
Dec 04 2020 12:10am
When you hit a bump, the tire begins deflecting, therefore the volume begins to decrease, therefore the pressure begins to increase, until the increasing pressure prevents further deflection. If tires didn't work this way, every bump would result in the wheel bottoming out and a pinch flat . . .
?? No, not at all. If you had a pressure regulator in your tire (so the pressure never spiked) you'd see about the same performance.

It takes force to deform the tire. That force increases the more you deform it even if pressure stays constant. That's the #1 reason you don't bottom out - because there's a lot of force opposing the deformation.

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by Chalo » Dec 04 2020 1:22pm

There is no significant change in pressure, because there's no significant change in volume. The things that change are the contact patch size and the surface area of tire that's squished into a shape other than what it takes under air pressure alone.

Think of a bouncy castle as example. The pressure inside the air bladder doesn't change as kids pile in; it stays at whatever steady pressure the blower provides. What changes is the area of the inflated structure that's deflected from its normal inflated shape and placed under tension by being distorted. That's what a tire does. Locally, the surface is placed under elevated tension, but the pressure inside doesn't change in any meaningful way, because the enclosed volume hasn't changed much at all.
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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by fatty » Dec 04 2020 1:37pm

JackFlorey wrote:
Dec 04 2020 12:47pm
?? No, not at all. If you had a pressure regulator in your tire (so the pressure never spiked) you'd see about the same performance.

It takes force to deform the tire. That force increases the more you deform it even if pressure stays constant. That's the #1 reason you don't bottom out - because there's a lot of force opposing the deformation.
Tube and tire manufacturers endeavor to minimize the force required to deform their products: see latex tubes and tubeless tires. The "lot of force opposing the deformation" comes from pressure acting on surface area.

I'm running out of ways to illustrate this in lay terms, but why do you think tires blow out on big hits, even with tubes or tubular tires? The reduction in volume and concomitant increase in pressure exceeds the pressure capacity.
Don't take advice from:
there is no difference between a mean well CC/CV power supply and a device sold as a charger. they operate in EXACTLY the same way
Testing has demonstrated that ordinary rim brakes thermally outperformed all but the best disc brakes...You'll always add weight and cost, while not equalling the capabilities of comparable rim brakes, if you use discs

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by Chalo » Dec 04 2020 1:39pm

MadRhino wrote:
Dec 04 2020 9:45am
Chalo wrote:
Dec 03 2020 8:43pm
MadRhino wrote:
Dec 03 2020 6:25pm
Tires are not making suspension, because they have no negative travel.
Tires have static sag just like any other suspension.
... and that would make a nice 5/8 of an inch of negative ‘tire suspension’ travel, that would bounce back about 1 inch at 30 mph right? :roll:

Tire ‘sag’ must be set for proper grip and vibration absorption. When a tire is inflated too hard it does bounce 3 times the height of a hit, and transmits a lot of vibrations to the frame. When too soft, it will distort aside of the wheel axis in cornering, or pinch against the rim on any square hit. Ideal tire pressure is making it do its tire job properly, by spreading its correct contact patch under the average riding weight.
The most fundamental problem with pneumatic tires as suspension is that by design there isn't much damping (rubber hysteresis), and what damping there is can't change to match a different spring rate (air pressure). A tire's effectiveness as suspension is therefore comparable to mechanical suspension with springs only, no dampers. Some of us have spring-only suspension in our bicycle saddles, but our bodies serve as dampers in that case.
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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by Chalo » Dec 04 2020 1:44pm

fatty wrote:
Dec 04 2020 1:37pm
I'm running out of ways to illustrate this in lay terms, but why do you think tires blow out on big hits, even with tubes or tubular tires? The reduction in volume and concomitant increase in pressure exceeds the pressure capacity.
That's absolutely not true. When such things happen, it's the result of physical damage to the casing and/or separating the tire from the rim. The enclosed volume can't change much at all-- what freak occurrence would it take to reduce it by half and double the pressure?-- so the pressure hardly changes. It's localized tension in the casing, backed by constant pressure, that carries loads.
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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by fatty » Dec 04 2020 1:46pm

Anyway, moving on from tire mechanics, I thought it would be interesting to quantify this comparison.

While a zero-order approximation, the 2.35" tires are 60mm diameter, and using 90% of the tire "travel" to avoid bottoming out gives 54mm. Since both bikes take the same tire diameter, the 100mm suspension bike at the same 90% utilization gives 90mm + 54mm = 144mm total travel.

So what size tire would a hardtail need to approximate a 100mm travel suspension bike? 144m * (1/90%) = 160mm = 6.3in.
Such a tire and the requisite pressure would handle poorly, offer insufficient damping, and be too heavy.
Hence full suspension.
Don't take advice from:
there is no difference between a mean well CC/CV power supply and a device sold as a charger. they operate in EXACTLY the same way
Testing has demonstrated that ordinary rim brakes thermally outperformed all but the best disc brakes...You'll always add weight and cost, while not equalling the capabilities of comparable rim brakes, if you use discs

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by JackFlorey » Dec 04 2020 1:57pm

fatty wrote:
Dec 04 2020 1:37pm
Tube and tire manufacturers endeavor to minimize the force required to deform their products:
Right. That maximizes the ability of the compressed air to absorb shock and decreases rolling resistance.
I'm running out of ways to illustrate this in lay terms, but why do you think tires blow out on big hits, even with tubes or tubular tires? The reduction in volume and concomitant increase in pressure exceeds the pressure capacity.
That's silly. Try pumping up your tires to 20% over your usual pressure. See if they blow out. (They won't, unless you are running far above normal pressures.) Your volume changes by FAR FAR less than 20% when you take a big hit.

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by MadRhino » Dec 04 2020 4:20pm

For a DH rider, or street riders on fast ebikes, all of your arguments are jokes, wanting tires to be a suspension. It is an illusion, for those riding heavy and slow. Now we have a guy who wants to ride 40 mph on a hard tail hub motor bike, counting on ‘tire suspension’. Let me tell you that, the first bump he’s gonna hit in a turn will change his mind and make him slow down in fear that it does happen again. When building for speed, only delusional dreamers are bypassing safety concerns. I am done with this absurd discussion. Some can’t be told the truth, and need to learn with mistakes, or pain.
Make it fool-proof, and I will make a better fool.
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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by serious_sam » Dec 04 2020 6:44pm

MadRhino wrote:
Dec 04 2020 4:20pm
Some can’t be told the truth, and need to learn with mistakes, or pain.
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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by fatty » Dec 04 2020 6:50pm

MadRhino wrote:
Dec 04 2020 4:20pm
For a DH rider, or street riders on fast ebikes, all of your arguments are jokes, wanting tires to be a suspension. It is an illusion, for those riding heavy and slow. Now we have a guy who wants to ride 40 mph on a hard tail hub motor bike, counting on ‘tire suspension’. Let me tell you that, the first bump he’s gonna hit in a turn will change his mind and make him slow down in fear that it does happen again. When building for speed, only delusional dreamers are bypassing safety concerns. I am done with this absurd discussion. Some can’t be told the truth, and need to learn with mistakes, or pain.
Not sure who you are referring to -- I agree with you. See above.
Don't take advice from:
there is no difference between a mean well CC/CV power supply and a device sold as a charger. they operate in EXACTLY the same way
Testing has demonstrated that ordinary rim brakes thermally outperformed all but the best disc brakes...You'll always add weight and cost, while not equalling the capabilities of comparable rim brakes, if you use discs

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by Manbeer » Dec 04 2020 9:22pm

Not knowing how bad the roads are, I can point out the following without getting scientific

Going 25ish on a normal road bike or even much slower and hitting patches of gravel that washed out from a driveway etc can be scary.

I hated always being on the lookout so I got a gravel bike for the road

I ride on a rough shoulder on that and it beats me up pretty bad with 35mm semi slicks

The problem with ebikes is that they do not require the same level of engagement when riding the same or higher speeds. When you are hammering on a regular bike at 180 beats per minute hr you are in the zone and alert. I can go the same speeds on an e-bike and not be nearly as careful

Even in the zone, I managed to nail a wood post that fell in the road while night riding last spring and was nearly smashed to bits. I was probably doing about 20.

My daily driver ebike is a 26" hardtail with 4" of travel up front.
Would 29" be better? Yes
Would FS be better? Yes

Even with 2.5" hookworms, it doesn't feel unsafe, but I mean after not that long if you aren't actively pedaling your butt hurts.

On another note, when I ride normal bikes off road I held out on the 29er thing forever as I'm a retro grouch. All the guys I ride with have 29ers and when bombing down trails that are filled with roots and rocks, they just roll over things that slow me down a lot. I found in many cases, I had to pedal as hard as I could to keep up with them coasting. So I see the benefit in both.

I would lean towards a 29" fs if possible or 69er setup

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by markz » Dec 04 2020 10:45pm

Manbeer wrote:
Dec 04 2020 9:22pm
69er setup
I think the 69'er (26 in rear, 29 up front) would be great for rear hub motor setup but you could take it a step further, if you have disc brakes. Go 24 rear and 26 front, this gets you smaller diameter wheel for the hub, but the downfall is the 26 in front for rolling over things not as easier then 29, but maybe go 24 rear, 29 front and forget what it looks like thats other peoples problem. 24/29 might not level the bike out, your pedals might hit the ground more so install shorter ones.

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by goatman » Dec 04 2020 11:41pm

26x3.0 front 24x3.0 rear, 40mph commuter. no suspension, used to run 26" hookworms. the 24x3.0 made a night and day difference, really softened out the ride but like mentioned above, hit something hard at 40mph, itll wake you up

Image

put it on a fs mtb 26x2.35f and 24x2.80 r and its a whole new experience, dont feel anything

Image

the 24x2.80 mongoose tire

Image

but to commute any kind of distance the fs mtb is my last choice, feel stiff and walk funny like getting off a horse, great for 20km rips but 80km round trips are not good

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by fatty » Dec 05 2020 12:58am

Manbeer wrote:
Dec 04 2020 9:22pm
I would lean towards a 29" fs if possible or 69er setup
markz wrote:
Dec 04 2020 10:45pm
I think the 69'er (26 in rear, 29 up front) would be great for rear hub motor setup
Thanks. I'm thinking a R:26x2.35 / F:27.5x3.0 Vee Speedster would be a good compromise.
Don't take advice from:
there is no difference between a mean well CC/CV power supply and a device sold as a charger. they operate in EXACTLY the same way
Testing has demonstrated that ordinary rim brakes thermally outperformed all but the best disc brakes...You'll always add weight and cost, while not equalling the capabilities of comparable rim brakes, if you use discs

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by fatty » Dec 05 2020 1:16am

goatman wrote:
Dec 04 2020 11:41pm
26x3.0 front 24x3.0 rear, 40mph commuter. no suspension, used to run 26" hookworms. the 24x3.0 made a night and day difference, really softened out the ride but like mentioned above, hit something hard at 40mph, itll wake you up
Thanks for the input -- very cool bike. My initial plan was a relaxed, long wheelbase cruiser on a 26x3.5, but I couldn't find a cruiser frame in the US that wouldn't involve big compromises, and a 2.35 hardtail would not be preferable.
Which chopper frame is that, and how do you like it?
goatman wrote:
Dec 04 2020 11:41pm
but to commute any kind of distance the fs mtb is my last choice, feel stiff and walk funny like getting off a horse, great for 20km rips but 80km round trips are not good
Due to frame geometry/seating position?
Don't take advice from:
there is no difference between a mean well CC/CV power supply and a device sold as a charger. they operate in EXACTLY the same way
Testing has demonstrated that ordinary rim brakes thermally outperformed all but the best disc brakes...You'll always add weight and cost, while not equalling the capabilities of comparable rim brakes, if you use discs

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by goatman » Dec 05 2020 2:47am

yes, you sit too high on a mtb

the cruiser is a giant stiletto and can ride it all day with no problems. just not all year

my 40 mph commuter work truck is my trike, love it
viewtopic.php?f=6&t=103834

BUT im looking at doing a recumbent like Neptronix

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by markz » Dec 05 2020 6:06am

How many recumbents do you see while your riding around Surrey British Columbia?

goatman wrote:
Dec 05 2020 2:47am
yes, you sit too high on a mtb

the cruiser is a giant stiletto and can ride it all day with no problems. just not all year

my 40 mph commuter work truck is my trike, love it
viewtopic.php?f=6&t=103834

BUT im looking at doing a recumbent like Neptronix

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by dogman dan » Dec 05 2020 9:21am

This is where you start getting a welder, and building the frame you need by modifying a steel bike frame into what you need.

One of my builds would have been even sweeter, if I had made it with the rear end of a pit bike attached. This bike was very comfortable to ride, super stiff in the mid frame, but since it was built for 18 mph, it needed no rear shocks.

But with rear shocks, it could have been a very sweet ride. Nothing fancy, just a swing arm and two shocks from a pit bike.
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But as I started thinking about motorcycle like e bikes, I just said frock it and bought motorcycles. Just cheaper, and I'm a notoriously cheap bastard.

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by goatman » Dec 05 2020 12:38pm

markz wrote:
Dec 05 2020 6:06am
How many recumbents do you see while your riding around Surrey British Columbia?

goatman wrote:
Dec 05 2020 2:47am
yes, you sit too high on a mtb

the cruiser is a giant stiletto and can ride it all day with no problems. just not all year

my 40 mph commuter work truck is my trike, love it
viewtopic.php?f=6&t=103834

BUT im looking at doing a recumbent like Neptronix
i dont see any recumbents but when i was working on my boat in dry dock i did talk with a guy who has one and the last picture in the scorpion thread shows a concrete switchback ramp and he said he will fall over if he doesnt take his feet off the pedals when going through there. but if i can find one of these on craigslist id scoop it up quickly

http://www.recumbentriders.org/forums/threads/9170/


i agree with Dogman, when i look at my stiletto, i keep contemplating if i want to pull out the grinder and welder and add rear suspension

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by neptronix » Dec 05 2020 2:13pm

dogman dan wrote:
Dec 04 2020 6:26am
Hmm, while you are having fun talking tires, I'm thinking some places commuting 40 mph on bicycles would be suicide, and other places no problem. It just depends on the route you will be riding, how likely cars are to turn into your path thinking a bike goes 15 mph, oops, your doing 40, whack.
That's the one remaining problem i have had on my fast bikes. People assume a bike is going slow, and then want to pull right in front of me so that i crash into the rear of their car. It happens more often in the bike lane than the car lane.

It's happened so many times that i expect them to make this miscalculation as i ride.

Another issue is being honked at and people yelling that i should get out of the road when in the car lane.

I'm sure i exacerbate this by making every fast ebike i ride look as much like a bicycle as possible. And also ALWAYS having a super huge chainring so i can still pedal at high speeds.

I would bet that if you appeared more like a motorcycle then this wouldn't be a problem. But then you'd attract the attention of the lawmen. The only way to remedy that is to build a slow motorcycle on a motorcycle frame instead of a bike frame.

I like the freedom of being a bike sometimes and a motorcycle others though. So i chose to identify as a bike. :lol:
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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by donn » Dec 05 2020 2:23pm

goatman wrote:
Dec 05 2020 12:38pm
i dont see any recumbents but when i was working on my boat in dry dock i did talk with a guy who has one and the last picture in the scorpion thread shows a concrete switchback ramp and he said he will fall over if he doesnt take his feet off the pedals when going through there.
Yeah, that's challenging, and for me, it's worse with a motor. Now I have two propulsion systems to manage in the delicate balance of moving through a tight turn - one that's a little under powered for the heavier bicycle, the other is overpowered with a big dead area at the beginning of the control. It's a lot more fun once you're past walking speed.
but if i can find one of these on craigslist id scoop it up quickly
You know that Maxarya in a photo Neptronix posted earlier - Maxarya is in Canada. You might be able to pick up a used BikeE and that will be a whole lot cheaper, but I like the 20" front wheel on the Maxarya. Anything else, probably no suspension.

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by neptronix » Dec 05 2020 2:52pm

Manbeer wrote:
Dec 04 2020 9:22pm
I hated always being on the lookout so I got a gravel bike for the road

I ride on a rough shoulder on that and it beats me up pretty bad with 35mm semi slicks

The problem with ebikes is that they do not require the same level of engagement when riding the same or higher speeds. When you are hammering on a regular bike at 180 beats per minute hr you are in the zone and alert. I can go the same speeds on an e-bike and not be nearly as careful
Yup.

On a pedal bike, it's much easier to watch the road and micromanage where the wheels go so you can dart around every irregularity. This is fine between the 10-20mph. This starts to get exponentially more annoying and dangerous beyond that because it requires a better reaction time the faster you go. The danger is that having a motor DOES make you err in the direction of being less engaged, and miss a bump which your vehicle cannot handle. I've had MANY of these white knuckle moments on hardtails.

As i've built ebikes over the last 10 years, i've become less tolerant of feeling anxious while riding. So i've started to gradually build bikes less like a Mustant ( fast in a straight line ) and more like a BMW ( as much attention has been put into going fast as wheel grip, handling, weight balance, braking, etc. ). So my larger wheelbase semi recumbents are designed to ride like luxury sport cars. Not just for creature comfort but for safety.

You can be completely un-engaged and the bike is completely forgiving of your mistake. You can point the front wheel in the wrong direction and you will have ample time to correct that error, even. You can roll over a patch of goatheads and not worry about the tire going flat. The only thing you worry about is a big pothole, but you'd also be worrying about that in a car.

I recommend anyone building a fast bike to do the same. Build a machine that is confident and you will feel confident riding it :thumb:
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: 40mph commuter: slack hardtail on 29" tire or steep full-suspension on 26"?

Post by fatty » Dec 05 2020 7:23pm

goatman wrote:
Dec 05 2020 2:47am
yes, you sit too high on a mtb
Could this be addressed with a dropper seatpost, running the saddle all the way down on the top tube while using throttle, and extending it back up if needing to pedal?
Don't take advice from:
there is no difference between a mean well CC/CV power supply and a device sold as a charger. they operate in EXACTLY the same way
Testing has demonstrated that ordinary rim brakes thermally outperformed all but the best disc brakes...You'll always add weight and cost, while not equalling the capabilities of comparable rim brakes, if you use discs

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