The Effects of Bigger Wheels

[Bordtea]

Hi all

Can't come to a conclusion on this one and after some brief research it seems there's a fair amount of confusion.

I'll start with a train of thought that bigger wheels = better MPG. Bigger wheels means a larger rolling radius which should mean less rolling resistance, therefore better MPG. However, when you bring in factors such as bigger wheels being heavier therefore more weight for the engine to move, bigger wheels also generally have wider tyres which would then increase rolling resistance, I'm tempted to say that larger wheels generally means less MPG?

What then about acceleration and top speed? I'm inclined to think that acceleration would be decreased as you're essentially making the gear ratios longer, but top speed will increase?

Handling should in theory be better, but the ride would be harsher?

Basically been thinking about changing from the 14" standard VTR alloys to some 15/16" alloys to close the wheel arch gap a bit (don't want to lower), but not sure on the effects it'll have on the car?

Discuss :panic:

[mlawlan69]

Christ on a bike, stop thinking so much.

The difference in the real world will be unnoticeable.

[Bordtea]

Christ on a bike, stop thinking so much.

The difference in the real world will be unnoticeable.
Yeh I know real life differences would be minimal, but it is interesting :cool:

[adamskiTNR]

Firstly "Christ on a bike, stop thinking so much.

The difference in the real world will be unnoticeable."

Is caveman talk.


The effects of wheel diameter, and more importantly mass, can be significant to vehicle dynamics. The trade off between diameter, tyre width, and unsprung mass is a compromise most of the time. On a road car the most notable will be the grip gained from increasing the contact patch. The unsprung mass will have an effect, but with such soft suspension and damping (both suspension and tyre), with a relatively heavy vehicle this is less important.
The subject is huge, you should go and read some more into it if you are interested. Beware, it will quickly end up just being pages of math.

[e8_pqck]

195/45/15 is more or less the same as 185/55/14. This is why citroen use both wheel sizes and the same speedo setup. Tyres tend to be heavier than wheel too so if you want to go really light, use some C5 Alloy steels.

[josh89vtr]

Just lower the thing 35mm. It won't b that noticeable but it will probably close the arch gap by the same amount as fitting 15"/16" alloys only without all the technicalities mentioned earlier

[GTuff]

Bigger wheels = bitches be going crazy? Pretty sure thats what the Internet taught me....

[ns9900]

IMO depends on th overall diameter. if its considerably smaller then OE(>3%), you get better acceleration but worst fuel eco at constant speed as there's a reduced internal momentum of th tyre n rim. speedo will read more then your actual speed and also, take this with a pinch of salt, large side wall = more flex = more body roll. larger sidewalls tend to accompany smaller rims if u maintain OE diameter

opposite can be said for going for large, pretty much entirely vice versa with with th added general benefit of better aesthetics but th potential to wear out bearings faster (extra weight and dimensions i think)

[stigsdump]

in the real world tho' larger wheels usually mean a reduced profile tyre is fitted that just about keeps the overall diameter as previous.

As stated the ride quality suffers and handling improves....but unless you're going from 80 to 40 profile only minor changes are hardly affected. You get to the point where its the compound and tyre construction that play a larger part in the handling than the actual tyre profile.

When i bought my car I went from OEM 15" to 17's with 205/40. The ride was notceably harsher and grip not improved to the point where you'd benefit from it in the real world of everyday driving. Asthetics apart, the 17's were actually lighter overall with tyres fitted than OEM, the down side being the 17s have a further overhang from the hub leaving the inner rim more prone to damage...its also worn the bearings too as the inner race was worn a notceable amount on the outer side of the bearing race on both rears that i've changed recently. The wear is only minimal tho in the bigger picture as both bearings are the originals and have done approx 50K

[LSOfreak]

Just lower the thing 35mm. It won't b that noticeable but it will probably close the arch gap by the same amount as fitting 15"/16" alloys only without all the technicalities mentioned earlier

but for some reason, fitting bigger wheels never closes the arch gap

always makes it look like a tractor

[stigsdump]

but for some reason, fitting bigger wheels never closes the arch gap

usually because the lower profile of the tyre on the larger rim keeps the overall diameter the same as before. Many wheel suppliers who do packages calculate the tyre spec in order to keep the rolling diameter the same and therefore keep speedo accuracy

[Prickle]

PM Ross.. he had big wheels on his 106 GTI.

17/18"? cant remember

[MartinObviously]

Hi all

Can't come to a conclusion on this one and after some brief research it seems there's a fair amount of confusion.

I'll start with a train of thought that bigger wheels = better MPG. Bigger wheels means a larger rolling radius which should mean less rolling resistance, therefore better MPG. However, when you bring in factors such as bigger wheels being heavier therefore more weight for the engine to move, bigger wheels also generally have wider tyres which would then increase rolling resistance, I'm tempted to say that larger wheels generally means less MPG?

What then about acceleration and top speed? I'm inclined to think that acceleration would be decreased as you're essentially making the gear ratios longer, but top speed will increase?

Handling should in theory be better, but the ride would be harsher?

Basically been thinking about changing from the 14" standard VTR alloys to some 15/16" alloys to close the wheel arch gap a bit (don't want to lower), but not sure on the effects it'll have on the car?

Discuss :panic:

the differences are noticeable.

I went frome 195/45/15 to 185/60/14 (an increase of only 4% on the rolling) and I now have a huge hole in my wheel arch liner. :y:

didn't affect mpg whatsoever because I don't commute on motorways.

Fit wheels which go with the car. you want larger sidewalls for better mpg as you'll get less tramlining as you do with low profile tyres.