What is the maximum weight that “normal” racing wheels can withstand?

Question

I was recently in a bike-shop where the proprietor told me that the "normal" racing wheels of the more advanced bikes are normally only rated to carry 85kg. For example, he mentioned the Bianchi Maddux RX 5.1 as being unsuitable for a 95+kg person… you could ride on them, but within six months you would be unhappy.

I have never heard this before, and while it is obvious that the wheels will have a designed weight limit, I find 85kg really light.

I am over 6'4", so getting to 85kg renders me as a stick insect, and is unlikely to happen… So I would like to know whether I really need to splash out the extra to get custom made 36 spoke wheels.

So the direct question, for a normal 24 spoke wheel, what is the designed carry load for this wheel?

Edit: I ended up getting myself a pair of Mavic Ksyrium SR wheels. The general reviews seem to have them as being fairly strong...

Edit 2: Having ridden these wheels for a few thousand kms, I can say that they really are strong. I just had a front-on accident where the bike frame had the top pipe literally snapped , and the front wheel is only slightly off true, and with a relatively small dent... still enough to write the wheel off, but I was extraordinarily impressed!

Answer 1

As a sometime wheelbuilder, I'd say yes. Lightweight wheels definitely come with weight limits and you should respect them. It should be in the manual for the wheel, and ideally on the spec sheet as well.

That's not to say you need to obey them, just be aware that when you don't you're much more likely to have problems. But for a race where they matter, it can be worth it. You're likely to get away with them for flat time trial when a steep climb or criterium will see them fail in the first race. But for the TT, those wheels might shave the critical 5s off your time.

It's not just your weight on the saddle that matters. You're also stronger than a lighter rider, and more likely to have a huge amount of explosive power. Those are the things that actually cause wheels to fail because that's when you're side loading the wheel. Throwing the bike around in a sprint is especially bad because you're throwing your weight sideways at the bike on the down stroke.

I've had customers who can't even get a reasonable life out of standard 36 spoke wheels. All it takes is a 100kg guy who races criteriums or rides to work and likes jumping out of the lights, and their wheels start failing after a few Mm. The tricky ones are the 120kg+ riders who are overweight and are riding to lose it. Often we see them only after their first bike has fallen apart under them (and it's a combination of being heavy and poor technique - they don't lift off the saddle on bumps, so the rear wheel takes the full impact of every lip and pothole). Having to explain that no stock wheel will work can be hard - instead of a $500 bike they're going to need a heavy $600 steel MTB with $300 of custom wheels.

Answer 2

The ultimate limit of a wheel is not in terms of "weight", but in terms of force. I would guess you could statically load most bicycle wheels with about 1000 pounds of weight without causing a failure. It is dynamic loads that are the issue, and those are hard to predict.

When you hit a good-sized bump with a bike wheel (in a non-suspension frame) you apply a force equal to several times your weight to it, and the amount of force applied is going to depend, among other things, on how much shock-absorbing you supply with your arms and legs. Hitting a bump stiff-armed and with your rear on the saddle applies much more force than if your arms are bent and your legs flexed and supporting you above the saddle.

Weight limits that manufacturers list are at best a guess, based on the "average" rider perceived to be using that style of wheel. If you ride more aggressively, on rougher terrain, and/or with less shock-absorption provided by your arms and legs (or the bike) then you could be under the limit and still over-stress the wheel. If you're a "dainty" rider who sticks to smooth pavement, "glides" over RR tracks and the like, and never hops a curb, you weight could safely exceed the "guidelines" by a substantial amount.

Answer 3

Hmm. It turns out that he might be onto something. I found this on the Fulcrum Racing 7 manual page:

• If you weigh over 109kg/240lbs then we advise you not to use this product. Non-compliance with this warning can damage the product irreversibly.
• If you weigh 82kg/180lbs or more, you must be especially vigilant and have your bicycle inspected more frequently (than someone weighing less than 82kg/180lbs). Check with your mechanic to discuss whether the wheels that you have selected are suitable for your use, and to determine the frequency of inspections.

I cannot find a similar statement for the Maddux, but it is not improbable that they have something similar.

Answer 4

A common problem. I ran into 180lb weight limits on both wheels AND pedals when putting together my last bike. That seems to be the typical number, so those of us that are bigger than that need to be careful and just expect more frequent failures. Seems like everything bike related is designed for short skinny people. :-)

Answer 5

Mavic says 100kg limit for all their wheels. Maybe you should look at a different brand?