I'm so fat V2, I snapped my bike frame

[el_walto]

Infinity invader from Costco. Paid $299. 1 Year old, 3000km. My weight 205lb.

Now I'm going to try to put it back to stock configuration and bring it back even though all the original blade spokes broke within the first month of having it. Makes it look like i jumped it off a bridge.

 

[spinningmagnets]

Many people have no choice but to start out with a light-duty frame. I don't know if this would help, but perhaps if you install a sprung seat-post it will spread-out the impact of your bodies weight when hitting a bump? Is the frame aluminum or steel?

 

[morph999]

lol, I weigh 250 or somewhere around there. Sounds like a bad bike. I don't know if Infinity's are good or not. I'm not a bike expert.

 

[swbluto]

Honestly, 205 lbs. should be well within that bike's weight limit.

If a seat suspension could've prevented it, that tells me that the stock suspension sucks, because I believe it's supposed to dampen those kind of stresses including at the point at which it snapped. A seat suspension certainly wouldn't hurt, though. If it isn't the stock suspension that sucks, then it seems likely it's the frame's design that might be at fault - might be a cheap non-durable metal (Steel comes in a variety of strengths), the pipe might not be thick enough, whatever - it seems likely the frame just wasn't cut out for real world forces.

But talking about forces, the force exerted will depend on speed. What kind of speeds were you attaining on the bike? What kind of terrain was it on? If you hit a bump/depression at a great enough speed, you may bottom out the suspension which will basically then act like a non-suspended bike and have a spike in the force exerted which then would lead to snapping. It seems likely they only designed the bike for 20 mph on the flats kind of speeds and they may even have included tiny instructions to not run the bike off-road, as funny as that might sound.

If that bike uses air suspension, the bike's build quality is probably cheap judging by the price.

 

[el_walto]

It broke when i was riding it up hill. It is cheap aluminum. Infinity bikes are very cheap 300$ CAD for full dual suspension bike. I hope Costco will give me a refund.

I know someone else who bought the same bike and the spokes fell off his because they were not tight enough. The front forks are springs and have had tons of play since the day i bought them.

I ride the bike at up to 70km/h downhill(this just coasting and doesn't require the motor). I usually ride closer to 50km/h on my way home.

 

[philf]

Thanks for sharing that experience, el_walto!

I spent a bit of time rummaging for parts (or complete donor bikes for future projects) last year, and wound up buying a REALLY cheap full suspension bike at the end of last season which I knew was crap when I bought it, but hit all the right notes to be a potential e-bike. It isn't dissimilar to what you picture - the frame is aluminum, but the front forks and rear triangle are steel. At the time, this seemed like a GREAT mix for an e-bike, especially for cheap.

But...

First and foremost, most inexpensive full-suspension bikes suck for regular riding, unless you really use 'em for the terrain they're designed for (and even then, your mileage will vary). This is yet another of those friggin' marketing things that makes people of my age and experience crazy. There are bazillions of reasons why, but you only have to ride a decent "standard" bike (or, in fairness, a recent example of an up-scale full-suspension bike with the requisite tuning mechanism to counter "pedal bob" and "brake jack") to appreciate WHY. For the most part, cheap full suspension bikes sell on their looks to a public that perceives a technological advance from what they grew up with. "Extreme" sports haven't helped, in that the younger crowd is an easy hook. The average person won't question what the design really means. And it's ubiquitous - these bikes are to this generation what cheap all-steel road bikes were to mine back in the day, but with fewer real merits. But they can make fine e-bikes, if your target is a bike you don't intend to pedal much.

If you DO, though, then you really start to notice some things. That "sprung" rear triangle REALLY robs you of energy when pedaling unless you have something to combat the energy loss. And this is precisely why I elected to "take the spring out" of the donor bike I've been playing with, essentially turning it into a hard tail for all but the worst pot holes.

I can tell you that the bike is WAY more dynamic when pedaling with the rear triangle locked up, but looking at el_walto's post, I now see a more sinister problem. Without the spring, and the fact that it's necessary to extend the seatpost most of its useful length to accommodate my height, I'm a 220lb weight on the end of a big "pry bar". I'm wondering if it might not be fairly easy to snap this frame in the same way that el_walto describes.

Thanks for the wake-up call!

Edit: I've just revisited the picture that el_walto posted of his bike, and the seatpost/lever thing I describe really looks like a potential factor, here. *gulp*.

 

[dogman dan]

I'm not a big fan of that particular type of frame. the seatpost is cantilevered out, and no gussets there to help resist bending past the last bolt on the center support. Look around, even in the cheap bikes, there are better frame designs, and others designed more for looking cool. Look for more metal bracing around the obvious stress points on the next bike.

Stuff like the spokes breaking is because you have to tune a bike after riding awhile, especially the first few hundred miles. That is partly your fault.

 

[TPA]

I started out at 293 lbs. Every time I hit a bump, I cringe and wait for the snap that has not come. I don't have that cantilevered situation, but my bike is aluminum.

I'm 270 lb now and still feel for my poor ol' bike.

 

[el_walto]

Please note that i did put a slightly longer seat post on the bike than it originally it came with. I'm sure this didn't help the bikes situation.

 

[gogo]

I had several $79 bikes to choose from and I chose this bike because it had the strongest design in that area and is steel.

 

[morph999]

I got a non-suspension bike because I don't like replacing shock absorbers. HOw long do those shocks last? About as long as car's ?

 

[317537]

Yeah the new trend in our area with the kids is seat posts down to the frame. Their knees bowed out, like OMG they just seem to know nothing about correct adjustments Those big MTB's with the full suspension do loook awesome though. Almost like a space shuttle or a transformer. The best ride (non-ebike) I’ve rode was my racing tour bike and a very old cruiser with 700c rims. It used to fly along with ease.

Where that break occurred is interesting and the op mentioned the seat pole being set so high. You would think by the look of the thing it wouldn’t break in a million years.

Ebikes give the bigger boys more speed than they are capable in most situations. I guess with no motor the bike is limited by the riders abilities. The bumps are shocking and this thread has opened my eyes to the way that suspension works hitting at those areas. Just the wrong circumstances, like the riders sits as the right at the time the front wheel dives into a hole and snap. You would of thought the seat pole would of been the first to go though.


I always dreamed of putting a motor on a bicycle ever since I could ride one. There is so much more to it than what the new comer to the hobby would expect. Even unmotorised bikes are quite a feat of engineering the way all the need bits connect and work.

 

[dogman dan]

The 450 mxr pic is a good example of what I meant by , look for some bracing at the seatpost. I only weigh 180 and I hear my frame creak all the time.

 

[docnjoj]

I got a non-suspension bike because I don't like replacing shock absorbers. HOw long do those shocks last? About as long as car's ?

I'm afraid those "shocks" never really dampen anything, so they probably dont wear out much. The "real" shocks are a lot of money and have rebuild kits, Like Fox and Cane Creek.
otherDoc

 

[philf]

I'm afraid those "shocks" never really dampen anything, so they probably dont wear out much. The "real" shocks are a lot of money and have rebuild kits, Like Fox and Cane Creek.
otherDoc

Exactly. The Lion's share of of "affordable" full suspension bikes out there have a "shock" that is nothing more than a spring. You need something more than that to be able to dampen the spring action, otherwise you just "bob" along when pedaling. The perfect design absorbs shock while being able to keep the back tire on the ground - all at the same time as NOT robbing you of power when you're pedaling. The components that get close to being able to deliver this are EXPENSIVE and take some effort to tune properly.

 

[lesspedal]

Hardtail mtb with a good suspension seat post is the way to go.
Trev.

 

[dogman dan]

The cheap "shocks" have an easily replaceable spring. Cheap on ebay, get a strong one, since the weight of batteries etc make a 650 pound one too weak to begin with. You are going to just bend rims and break spokes with a hardtail, unless it's made for heavy use. Surly frame is what you need to go hardtail.

 

[el_walto]

FYI. Costco took the bike back in 2 minutes, no questions asked, even though it looked like it had been jumped off a bridge.

 

[317537]

FYI. Costco took the bike back in 2 minutes, no questions asked, even though it looked like it had been jumped off a bridge.

They probably were amazed that it broke. You got to think in any case the bike is going to get other damaged from a failure like that. Maybe they wernt thinking as this has never happened before.