A basic concept question from a beginner

[ned]

Are smaller wheels (15") favored for "rally" because you can fit a larger (proportionally more rubber) tire on them?

Is the increased amount of rubber being used as supplemental "shock absorber" capacity?

Or is it for some other reason?

Thanks

[FlatBlack]

Rally tires are usually offered in 15" sizes

Which reminds me, I need to get my R202s mounted...

[williaty]

Rally tires are offered in 15" because rally wheels are offered in 15".

Rally wheels are offered in 15" because rally tires are offered in 15".

See how that works? :lol:

That being said, for gravel events, 15" wheels do allow the use of tires with considerably more sidewall to absorb impact and deform over rocks to avoid punctures. With tarmac events, you'll see the international-level teams going to larger wheels and thinner tires since, generally, slicing up the tire isn't as likely.

[Rallycat66]

If I recall correctly, 15" gravel tires are mandated by the FIA rules. 18" for tarmac, 16" for snow. Hence the majority of the tires you find are those sizes.

Smaller tires are produced for older cars and other series. Occasionally you will see 16" gravel tires, but they are generally rare and made in very small batches for specific events/cars.

And yes, the 15" size was probably agreed upon because of the height of the sidewall and the extra protection it gives on rough terrain. They may have also done so to limit the size of the brakes that teams could stuff in there.

[ned]

Assuming that suspension, total tire diameter, tread pattern, etc are being kept equal, would a 15" wheel be an improvement (over say a stock 16" wheel) in terms of off-roading capability (specifically, the ability to absorb bumps/impacts on rough roads)?
My assumption is that it would be an improvement - simply by virtue of there being more rubber between the bump, and the less flexible parts of my car.
Is my logic sound? Are there any nuances that I am missing?

Thanks again