I have a low Audi S4.

I was gonna raise it a bit but still have it lowered.
I have 235/40 zr17 tyres on, if i change to 225/40 zr 18 wheels/tyres will i raise the car up by 1 inch???

At the mo it just about scrapes on speed humps , so am hoping 18's will help or am i being stupid?

Thanks
Nick

 

Well the tyre wall size is going to be a tiny bit lower (but only the same amount as wearing the tread on the old tyres really!) and the wheel will be half an inch bigger from the centre down (above that doesnt effect the height) so net effect will be to raise it about 1cm or so.

You will also make your speed read lower than it does now for the same speed.

 

the car will be raised by 8.7mm

 

Time for a new spring kit by the sounds of things.

 

edited cause i cant read

 

Can i query that Martin whats wrong with my calcs

17" =431.8mm 235 X .4 sidewall=94mm x2 = 619.8mm dia
18" =452.2mm 225 X .4 sidewall=90mm x2 = 632.2mm dia

Car is raised by half that 6.2mm

 

There is no point doing calcs to the nearest .1 of a mm when tyre treat depth goes from about 7mm down to 2mm normally anyway!

 

rod read the above edited post...try calculating it on a mobile phone and remembering all the figures! check your own sums for the 18" wheel size 18 x 25.4= 457.2!

 

Every point Chip thats the correct maths & maths rule everything.
Tyre wear would then be taken into account. I do this before every Topspeed run cos at 200mph it can make a 2/3 mph difference between new or worn tyres. .

ps. Dont help the lad asking the question though hes had 10 different answers so far .

 

[quote="MADRod
ps. Dont help the lad asking the question though hes had 10 different answers so far .[/quote]

yours wrong too, it seems!

nick... the car will be 8.7mm higher but as chip has mentioned worn tyres make the figures change. so if you put new 18's on the car and the original tyres are nearly worn out the figure the car gets raised by will be a little higher . cheapest way is to raise the car with another set of coil springs.

 

Thanks for the help martin

I will put the 18's on first as my tyres on the 17's are quite low and then see what happens.

Thanks
Nick

 

Why not use 235/40 18?

That would raise it another 4mm or so