Question of mass & physics
 

Need more information...
What is the recommended maximum weight for the wheelset?
What is your weight?
What style/conditions do you ride in?

Wider tires generally weigh more then narrower ones (all other things the same) so, yes, "weight distribution" does change. It moves more to the outer part of the wheel where the wider tire is. But I don't think that is really what you ask about.

Wider tires will better protect any rim from impacts. They tend to smoothen out the ride by better absorbing shock. But the load the rim sees is still the same, so to for the spokes.

In my ideal world riders use tires that are size/grade/design agreeable with the rider's needs/expectations, independent of the rim/wheel . Of course both have to be compatible with each other.

Don't expect wider tires to extend wheel life of make a too fragile wheel survive an overloaded situation. Andy

I'd be worried about spoke count. Fatter tires will protect the rims more.

No. For most of us light weight components are a waste of money. When we get down to 6% body fat then we can worry about component weight.

Having a wider tire or larger air volume will not increase maximum weight limit of the wheels.


-Tim-

Answer of engineering
Free body analysis: The distance between axles will not change, thus the weight distribution will not change.
Force path analysis: The rider's weight must be borne by the axles, bearings, hub shells, spokes, and rims regardless of tires.

A fatter tire will reduce peak impacts when hitting curbs, pot holes etc.
IF you rims are rated for a 200 lb. rider, a 215 lb. rider on SMOOTH pavement shouldn't be an issue.

A wider tire at lower pressure may well reduce shock (dynamic load/impact acceleration) on the components, which would be greater than the static load on the components.

Thus, there would be reason to believe that if one is very borderline, that it may tip one over the edge towards potentially being OK.

Also be careful with your riding. Watch the bumps.

But, as above, there might be benefits of building slightly stronger wheels.

I am very impressed with the technical answers and as usual we have many others that vary. I think I will just diet some more as weight is weight and I do not want to die on the road as I squeeze into my lycra just to have wheel failure...
The uber lightness is alluring when compared to the Mavic Askiums

No diet needed. Just go on long rides, and eat what you would normally eat, had you not ridden that day. This will create a caloric deficit, and the weight will drop off slowly and naturally.

That's how I did it anyway, your health situation and mileage may vary.

23 to 28 is insignificant to this scheme of yours..

buy wheels with a greater spoke count... for a better sense of security..

I'm a heavier 200+ lb rider myself. For reasons of safety I prefer larger tires. Larger tires = more rubber and, are generally more resistant to flats. It's one thing to get a flat tire when you're a 150 lb teenage boy. It's quite a different matter when you're a 220lb 63 year old man. One of my current favorite tires is the Michelin Pro-Tek series. They're a littler bigger than other bike tires. And, so far so good. No bad flats yet.

Having gone from 200 lb to 165 lb last year, I would like to encourage you. The first 10 lb was noticeable when climbing.

Don't listen to too many people. You know what to do. Good luck and please post your progress.


-Tim-

Looking at it purely from a "mass and physics" point of view for your specific question, as mentioned it's more mass at the circumference so yes the "distribution" changes in that regard. That will add some small amount of stress on the rear spokes and rim as you accelerate (I'd say insignificant compared to extant stresses). On the front wheel, a lesser effect on the wheel itself.

Regarding the increased tire volume, not mass. It will increase the duration of time where peak forces are applied to the wheel (decreasing impulse) so I believe that it DOES help the wheel withstand a greater rider weight. It that's enough to give the lightweight wheels greater longevity, that remains to be seen.

This. A heavier rider will put more stress on the rims and spokes than a light rider and a tire won't change that significantly. Fatter tires will reduce the effect of strong bumps, preventing the tire from bottoming out and damaging the rime (also, the impulse force wphamilton mentions could collapse the rim I think) in the road for any size rider but the stress of the bump will be added to the stress caused by weight. Further, we don't know the tire size used by the mfr in setting the weight limit. That limit may actually account for a wider tire for a heavier ride. So I fear you'll still exceed the wheels intended design limit. While there will be some safety factor in a manufacturer's stated limit, that limit does balance safety and likelihood of failure with the limiting sales by constraining the possible population of buyers. They don't put those limits on arbitrarily as a low limit also limits sales to some degree.

There's another issue. I weight 245#. I had a pair of Bontrager Race RLs on my bike. A good solid, strong, dependable pair of wheels with a good balance of stiffness and weight. I wanted to upgrade (lighter is better, right?) though, so I got a pair of Paradigm Elites off eBay. They were rated for my weight, but were lighter (and had lighter construction and fewer spokes). I went into my local Trek store, and Bill, a really experienced guy who was the mgr/head mechanic, told me "Given that you're a pretty big guy, I don't think you'll like the ride on those Elites as well as you like the RLs". Bill's usually right on bike issues (to a shocking degree*), and he was here. The Elites are great wheels, but for me the RLs work better. They're heavier with thicker spokes, so they tend not to flex as much. If only I could lose 40 lbs, those Elites would be sweet!

Upshot is that if a mfr suggests a weight limit, and you exceed it, there are two reasons you probably want to find a wheel that's a bit stouter: safety and performance. Your ride will be nicer and more efficient using wheels that match your avoirdupois. I found this to be true, anyway.

*I started working with bikes 45 years ago, and have a PhD in Engineering. So I think I know everything. Until I talk with Bill, who invariably throws out observations that indicate really deep knowledge, or a wrinkle I hadn't thought of. Humbling, but very helpful.