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      07-01-2010, 05:09 PM   #48
ajd's Avatar
United Kingdom

Drives: BMW 340i Touring
Join Date: Apr 2007
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Originally Posted by 335diesel View Post
Why on earth would a car roll and wallow more on 17s than on 19s? The suspension is the same.
Higher profile tyres have sidewalls that are not as stiff relative to those on otherwise equivalent lower profile tyres - hence they will deform more. This is felt as roll and more movement (wallow) between the wheels and the road. Pretty obvious really, but then again I'm an engineer


Of course people will go out of their way to justify buying sodding expensive 19s over smaller wheels but really, it's about looks.
I don't know about others, but I don't feel I have to justify buying them. I like them, and they were cheap.

A couple of quotes from auto engineers:

A larger, heavier tire and wheel assembly will gain more kinetic energy
from each short bump it encounters, which the suspension then tries to absorb without passing on to the passenger cabin.
So smaller tires give a smoother ride.
When tires bounce, a given amount of suspension hardware can put them back in contact with the road quicker if they have low mass.
So smaller tires give better handling.


Larger diameter, wider wheels may raise your cred in the McDonald's drive-thru queue, but they'll also blunt your car's turn-in, knock the edge off the handling, spoil the ride and cost you a fortune in new tyres.
My 17" wheels were actually fractionally a larger diameter (1.2mm) than my 19"s - but for all practical purposes the 17, 18 and 19" wheel/tyre combos I've used have had identical diameters. I think you maybe getting confused about the differences in handling of wheel/tyre combos that have different rolling radii.

I have driven my car on 17, 18 and 19" wheels, and it does affect handling - I'm not making it up! Turn in is definately better with lower profile tyres - & best of all with RFTs.

I think you should buy those 18" 162s you are after - they are the best SE wheel and will look great on your car and will improve the way it handles. You will notice this. If you get non-RFTs the difference in ride will be hardly noticable over the 17"s.