Large Wheels uncomfortable - why ?

[Deleted User]

Could someone please explain to me - in simple terms - why larger diameter wheels should make a car ride more uncomfortable ?

I would have thought that "larger" wheels would make driving over bumps and cracks in the road - less of a chore - but the difference appears to be true

Why ?

macman

Larger wheels mean lower-profile tyres. The space in the wheel arches is fixed, so the tyre sidewall must be shallower to accommodate the larger wheels.
The wheel is rigid, so the only impact-absorbing part is the tyre, and the air it contains.

[Deleted User]

macman said:

Larger wheels mean lower-profile tyres. The space in the wheel arches is fixed, so the tyre sidewall must be shallower to accommodate the larger wheels.
The wheel is rigid, so the only impact-absorbing part is the tyre, and the air it contains.

Right - so it's down to the tyres rather than the diameter of the wheel ?

molerat

I went from 16/55 profile to 19/45 profile and I find the majority of potholes are smoother as the wheel does not go as deep into the hole as it did with the smaller wheel. The only thing I find worse is corrugated surfaces for some reason - on one local road you can see the ripples as you look along it, in the old car I never noticed it but this one it is very noticeable, maybe the 35 psi accentuates it.

AdrianC

molerat said:

I went from 16/55 profile to 19/45 profile

But that's also increasing the diameter of the overall wheel and tyre, which is rarely that straightforward, simply from the point of view of fouling on suspension and arches - even before taking speedo error into account.

Assuming a 205 width tyre on both...
205/55 16 = 113mm sidewall, 406mm diameter rim = 632mm overall diameter = 1985mm circumf.
205/45 19 = 92mm sidewall, 482mm diameter rim = 666mm overall diameter = 2019mm circumf = 5.5% speedo/odo error.

If you increase the treadwidth as well, then not only does that diameter increase (255/45 would be the same sidewall height as 205/55), but you massively increase that fouling risk - because the tyre size is increasing in two directions.

If you aren't talking about simply changing rims on the same car, but talking about different cars, then...

photome

Deleted_User said:

macman said:

Larger wheels mean lower-profile tyres. The space in the wheel arches is fixed, so the tyre sidewall must be shallower to accommodate the larger wheels.
The wheel is rigid, so the only impact-absorbing part is the tyre, and the air it contains.

Right - so it's down to the tyres rather than the diameter of the wheel ?

It’s down to the profile of the tyre which generally speaking will be lower the bigger the wheel. If you read reviews of cars , many new cars   have an option from new of different wheel sizes and the reviewer will often mention that the ride is better on the smaller wheel due to a higher profile tyre.

Flight3287462

In my opinion large wheels and low profile tyres are the spawn of the devil with the current state of British roads.

The wheels and tyres are more prone to damage and significantly more expensive to repair.

On nice well kept roads free of potholes then there would be no problem.

Large wheels on standard cars are an affectation.

Grumpy_chap

Also chose the option (from standard choices) that has the smallest wheel diameter and largest tyre diameter - it may not look "bling" but it will be the most comfortable and the most fuel efficient.

EssexExile

Grumpy_chap said:

Also chose the option (from standard choices) that has the smallest wheel diameter and largest tyre diameter - it may not look "bling" but it will be the most comfortable and the most fuel efficient.

People on the Volvo forum moan that their R Design XC whatevers on 22" wheels are uncomfortable, but they look nice. Why anyone would want a race tweaked 4x4 on thin tires I can't imagine. I love my (not R) XC on 19" wheels and big fat tyres, it can go anywhere and no fear of scuffing the pretty alloys on the kerb.

coffeehound

Grumpy_chap said:

 and the most fuel efficient.

Hmm, that goes against my expectation that a hard, inflexible tyre would give lowest rolling resistance?

Ditzy_Mitzy

Presumably, too, if there's less 'squish' in the tyre then more work needs to be done by the suspension.  Suspension is much harder than it used to be, in addition to wheels getting bigger, meaning that ride comfort has a tendency to decrease.