large wheels and skinny tyres -why ?

[jcb]

just got our 2004 (new shape) 3.2FSI SE Quatro Tip. came with standard 17" wheels and 225/50/17 tyres. first thing we noticed, compared to our old A6, was the increase in road noise/tyre noise. swapped the wheels for 16" one and 215/55/16 tyres (still got the old A6 so easy to swap them over). instantly improved the situation and road noise is better and ride better. why oh why oh why do people put big rims on ? i drove the new car like a loony yesterday (for testing purposes you understand :D) and not once did i think "i wish i had bigger wheels to improve the handling". the car handles exceptionally well due to it being a quattro. no need for bigger wheels. is it just a case of vanity and asthetics ?. the taller tyres give much better give/suspension and the narrower tyres reduce road noise. surely when you have an exec car you want and exec ride ?
the next task - how do i make ride softer as its much harder than our old SE ??

[dandam]

I think big wheels are more for vanity sake than anything else. A lot of professional road tests will often state about the improved ride you get with smaller wheels and a larger sidewall (needless to say I still have 16" wheels and balloon like tyres). Improvements to handling will always be minimal.

Having said that when you are running standard wheels I'm surprised there is so much difference

[jcb]

I think big wheels are more for vanity sake than anything else. A lot of professional road tests will often state about the improved ride you get with smaller wheels and a larger sidewall (needless to say I still have 16" wheels and balloon like tyres). Improvements to handling will always be minimal.

Having said that when you are running standard wheels I'm surprised there is so much difference

IF you put the wheels/tyres side by side there is a significant difference in tyre width - you would not think the differnece between 225 and 215 would be that much but the number is a ratio not an absolute measurement so the 225's are quite a lot wider. maybe also down to the fact that the 16" are continetals and 17's are mixed - two contis and two other brands. alwasy found contis work best on an A6.

[Nigelo]

Are you sure the difference in road noise is due to the different aspect ratio? I have an Italian GT with considerably lower profile tyres (245 40x18 front and 265 35x18 rear) that exhibits no tyre noise whatsoever despite its 1,600 kgs. It does tramline with cold tyres however.

More to the point my Avant 3.0 tdi S-line (2006) has 18" rims and the original Dunlops were tolerably noisy but completely let the A6 down for handling, feel and roadholding. A change to Contis completely transformed the car BUT road noise now depends on the pressure settings. Standard pressure for part load is very quiet and smooth whereas high pressure for full load/high speed is more noisy but with noticably more grip as one would expect.

My conclusion is that road noise is tyre and pressure dependant and little to do aspect ratio.

hope this helps

[jcb]

its a bit of a minefield really. too many variables. i have always had contis on my old A6 and they are quieter. i can only concluded they will be quieter on the new A6. i am sure wider tyres have to be noiser as there is more rubber in contact with the road. i am going to go ahead with 16" wheels and taller tyres as they do improve the ride over rough surfaces. i have sourced some wheels (new) for £220 for 4. tyres are more than the wheels !!! but i need 2 new tyres anyway as the existing tyres are down to their tread wear limiters (which might also be contributing tot eh road noise).

[Nigelo]

I do not see how the width of rubber will affect noise and indeed, my own experience shows this is not the case. If you increase the width of the contact patch, you have less load per cm2 assuming the weight of the car is unchanged. Different tread patterns and as previously stated, different pressure settings are a completely different matter.

Incidentally, when I referred to the junking the Dunlops, they were were almost new when I bought the car so a true like for like comparison.

hope this helps

[jcb]

dunno about the theory but in practice the 16" are less noisy than the 17"