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I purchased a Urtopia Carbon 1 Pro ebike. I didn't pay attention to its weight limit, which is 240 lbs. The bicycle net weight is 34 lbs. Unfortunately, I am 6'3" and weigh 316 lbs. The bike frame is a large for my height, but I'm concerned about the weight limit. I'm not an aggressive rider and would use it on the road. The bike comes with 700x40 tires on a 36 spoke rim. Would changing the tire width and adding a front suspension help any? (Will the suspension travel matter?) Do I also need to change the wheels?

Electric bicycle with seat tube that does not reach the bottom bracket
Source

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  • 11
    Is it too late to return it ?
    – Criggie
    Commented Jun 21 at 2:09
  • 3
    With your weight try to return it and get a bike from an established manufacturer! This company has no long term experience in bicycle manufacturing and markets their bikes as cutting edge. It's at the opposite end of the spectrum of your needs. Commented Jun 21 at 19:09
  • (OP) Yes unfortunately it is.
    – E.E
    Commented Jun 22 at 0:03
  • Sell it. You will get a much better price now when it's still unused (and was never overloaded).
    – Nobody
    Commented Jun 22 at 10:43

4 Answers 4

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Normally I say bike weight limits are conservative and more about liability and Lawyers than engineering and would have a large safety margin on published weight limits.

However, this frame design with the seat tube not extending to bottom bracket, while looking quite cool, is heavily relying on the inherent strength of carbon. It is very much a design prioritizing "form over function". Traditional two triangle frame designs with a full seat tube are an inherently stronger design.

I would be cautious about overloading it 150% of its stated max limit and expecting it to perform well for many years.

You could ask the manufacturer (keep in mind any answer is in context of lawyers and liability). If possible and practical, likely the best option is returning for a refund and going for a design based on the traditional 2 triangle frame. Something from a touring lineup will be designed to handle more weight.

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  • 3
    The loads on that upper structure worry me, especially if you don't unweight the saddle for every single jolt. You'd be hitting it pretty hard right near the middle. A classic steel frame overloaded this much wouldn't worry me much at all, in contrast
    – Chris H
    Commented Jun 21 at 6:33
  • They probably over-engineered this sub-optimal design. Any engineer looking at a design like that would intuitively be concerned.
    – Michael
    Commented Jun 21 at 7:00
  • @Michael there is some evidence that they've built up the area around the seatstay/chainstay join, but enough for a 50% overload (which would be achieved with a backpack full of shopping)?
    – Chris H
    Commented Jun 21 at 10:16
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    (OP) Appreciate all the wonderful input. No useful weight responses from vendor except that a different model (Fusion GT) would soon be available at 330Ibs max limit. Unfortunately too late to return this one and even still have it in the box untouched and unassembled. They however indicated that a 40/50mm travel suspension fork is what they in general recommend for the bike. Max tire size is 700x40 and can't go wider.
    – E.E
    Commented Jun 22 at 0:18
  • I agree that this frame design is inherently much weaker than a standard diamond, but I'm not sure it's fair to call it "form over function". I could certainly see that the missing tube and the S-bend add a nice amount of compliance, and if they got their FEM analysis and carbon layup right then it could still be strong enough. But yes, better be cautious with overloading it. Commented Jun 22 at 8:52
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~360 pounds (163kg) system weight is a lot and I wouldn’t risk it on a bike not explicitly designed for such heavy loads.

Especially if most of the weight is in the rider which makes a broken frame or fork much more likely. With a lighter rider and lots of luggage on a front and rear rack your biggest concern would be broken spokes which is far more benign.

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  • There is little market for 160+kg riders, the choice is quite limited
    – fraxinus
    Commented Jun 21 at 11:11
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    @fraxinus: There are quite a lot of eBikes rated for 150kg which – while still being below a true 160kg rating – would give me more confidence. Especially if it’s a MTB (possibly rated for DIN EN 17406 Class 3 or 4) but you are not going to do any crazy jumps or drops.
    – Michael
    Commented Jun 21 at 12:21
  • Tall and heavy is taxing on any frame. Riding regularly, sometimes across curbs, I started breaking frames (alu and steel) when I reached 170 lbs. I have seen bigger people with special frames (e.g. an additional double diagonal going all the way from the head tube to the chain or seat stays, as in this frame). Even if the frame holds out for a while it may not last very long. Commented Jun 22 at 14:16
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My thought is to talk with the bike maker. Here is what I would ask when (if) you are able to contact someone at Urtopia:

  • What does "limit" actually mean?

  • Does it mean that the bike it will snap if you put 241 pounds on it?

    This is unlikely.

  • Does it mean that the rider should be 240 pounds but there is room in the design for carrying baggage of some kind? If so, how much baggage weight is allowed?

    According to this page, they describe the limit as a "Load-bearing capacity". This feels more like some kind of total weight metric as opposed to rider weight only. They advertise the bike with front and rear bags:

    Photo with panniers on rear rack of bicycle

  • Is the weight limit a function of the frame or the wheels?

    Weight limit is determined first by frame construction and second by wheel construction. You can't make the frame any stronger. There is no sense putting stronger wheels on the bike (which may be cost prohibitive) if the weight limit is restricted by the frame.

Hopefully a conversation with a knowledgeable person at Urtopia will provide concrete answers.

My opinion is that weight limits are usually set very low. Given that you don't plan aggressive riding, I'd go out and enjoy the bike and not worry about it.
On the other hand, if you feel the carbon fiber frame flexing beneath you during normal riding, I'd find a stronger bike.

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  • There used to be interesting data supplied with Colnago carbon frames showing how the forces, when in motion, are multiplied (in various scenarios). The frame can withstand a huge static load. It has to, because the forces in a dynamic load are huge.
    – Noise
    Commented Jun 20 at 21:44
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    “On the other hand, if you feel the carbon fiber frame flexing beneath you during normal riding I'd find a stronger bike.” Isn’t this the whole point of the peculiar lack of seat-tube? Elastic deformation is not necessarily a bad sign. Even as a 67kg person I can definitely feel long carbon seatposts flexing under me. The new carbon road bike also feels noticeably stiffer during sprints (which implies that the old road bike flexed [more]).
    – Michael
    Commented Jun 21 at 7:05
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    Luggage of course loads pretty much directly onto the axles, while extra rider weight is on the missing seat tube
    – Chris H
    Commented Jun 21 at 10:17
  • @ChrisH I agree, the missing seat tube does interesting things to stress the frame. Are you saying that the weight limit does not include baggage, that the baggage does not add stress to the frame or something else?
    – David D
    Commented Jun 21 at 13:20
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    @DavidD panniers add less (static) stress to the frame than the same weight on the rider. I was thinking that the dynamic stress might be better as the rider can unweight the saddle, but of course a seat tube also helps in tension in that case
    – Chris H
    Commented Jun 21 at 14:22
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Aside from the legal speech, I fail to imagine a 160kg aggressive rider.

A reasonable rider, even somewhat heavier, may induce less strain than a 70kg sidewalk-jumper the-street-is-my-downhill my-girlfriend-is-not-heavy-anyway type.

In short, try.

Avoid offroad, be conservative and everything will be ok.

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    I do not agree. 316 lbs (which is rather 143 kg) is close to twice the rider design weight. In my experience, much lower rider weight breaks frames over time, especially large frames. Commented Jun 22 at 14:21
  • The above is what a bike shop that services the Carbon 1 pro said. They let me know I would be okay as long as I wasn't aggressive. They wanted to true up the spokes or probably add some larger spokes. I still haven't unpacked it. I'll probably have to put up for sale because I am so torn about it. I love the bike but don't want to put a $2500 investment down the drain.
    – E.E
    Commented Jun 23 at 16:53

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