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How Low On 18's


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Im looking to lower by 30-40mm on 18'' Aeros.

Has anyone had issues with wheels rubbing, or getting full lock with this drop in height on 18's.

would be great to hear from those who have done this already before I jump in.


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havent droped mine but i do get some rubbing when i do full lock steering to the right when reversing and this is on standard suspension and 18" Aero's so am not sure how the rubbing could be avoided when you drop it down 30 -40mm on 18's. maybe you might have to change to 17's which will give you more arch room for dropping!!

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yes correct ALL BELOW IS A GUIDE ONLY FOR EXAMPLES OK hope it helps all

If you need info p.m me ok happy To help when i can Tyres i love them :innocent::devil:

if you calculate rolling radius to tyre size using the usual formula will be 99.9% same if calculated with accuracy

So if you add 1 inch to diam of wheel eg 17 to 18inch add 20mm to tyre width and reduce/subtract aspect ratio by 10%

This gives you the calculated rolling radius for accurate readings on speedo and mileage

there is a formula for calculations

EG running 245-45-17 17inch x 9.5 wheels changing to 18inch wheels based on same width

wheel radius is half diam (17)so 8.5inch/215.9mm + side wall 45% in mm is 110.25mm

rolling rad is 215.9mm +110.25mm = 326.15mm

so 18inch x 9.5 wheel for example

245mm width as 9.5 inch wide (tyre is 245mmwide to start as 9inch rim)

radius is 9.5inch/241.3mm half diam

so to calculate we need a rolling radius of 326.15mm

so aspect ratio must be a % of 325.15mm we need for rolling radius - half wheel diam 241.3mm

so rolling required is 325.15mm - 241.3mm half wheel diam = 83.85mm

Calculate aspect ration from mm to % of 245 mm wide tyre which is done by

245mm tyre width calculate what % 83.85mm is of the tyre width which is (34.10%) = 35/40% aspect ratio

so all in the tyre can be 245-40-18 or 245-35-18 if wheel is wider this is based on 9.5inch/241.3mm wheel change figures for wider wheels on the above formula(or ask)

This should keep speedo and mileage accuratly in range for the change

:hohoho: ok

merry xmaS

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All this doesnt answer the ops question. if he drops his cars height 30-40mm will it rub on 18" wheels was the question?? we all know IS's can handle 17 and 18" wheels but will they hold when the cars height has been lowered?

Merry Christmas and hope we can win the lottery in 2013 for an LFA and GTR order :hocus-pokus:

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I run 18" and i have mine dropped about 80mm(Yes, it is pretty low), i only get rubbing on full steering lock, againsts the chassis. I have my arches rolled and pulled out abit. So dont know if you are gonna rub there.

But yes, you would be able to drop it 30mm without problems.

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  • 2 years later...

Yes, I have -40mm all around with 18x8 wheels and tyres 225/40 all around and there is so little rubbing only on full steering. When I had 215/35 on front it was everything OK.

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