[mountainbiker24]

Ok, so I've been seeing this a lot lately, and I'm trying to figure out what I am missing. People tend to say something like "I'm 6'yada" and 225 pounds, so I'm riding an XL 29er...". What does body weight have to do with frame sizing? I sort of understand tire size and body weight, but wheel diameter? What am I missing here, or do people just like sharing their weight around here?

 

[jeremy3220]

It's not relevant and I'm 215 lbs.

 

[MarcusBrody]

I think in most cases, it's just part of them providing a full set of background info. I see the wheel size part less, but I often see "I'm 6'2, 185, on an XL frame". They aren't saying that they chose the frame size based on their weight, but more giving context to all the other things they've said. Some shocks/forks/suspension/frames work differently for different sizes, with the heaviest riders feeling the most flex for instance. I suspect that is the reason why weight is included, not to say that they chose the bike size based on their weight. It's just all part of a set of background info people can use when trying ti determine if a person's experience would be similar to their own.

 

[Cotharyus]

Body weight is not relevant to frame size, but I'm going to argue that it should be. Most manufacturers get a tune done for the suspension (shocks, forks) they put on a bike and use the same tune for all sizes of the bike. I think they should use mildly different tunes for different size bikes, because at 220lbs my needs on an XL frame for suspension are not the same as a 150lbs person on a medium frame. But that just means that Marcus may be correct with his answer above.

 

[mountainbiker24]

Good point about suspension tune.. What about tire size? Do heavier riders benefit more from wider tires and rims?

 

[knutso]

I would think generally heavier riders have less tendency/desire to stretch out, but body shapes and strengths vary so there definitely isn't a hard and fast rule.

More tire volume would let a heavier ride run less pressure without banging the rim up. I don't know how inertia, gravity, tire stiffness etc all work together to determine grip in a given corner, but I would imagine a bigger tire is better for heavier riders in the corners.