tire fitment question

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Old 11-06-10, 10:00 PM
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tire fitment question

Audi A4 with 235/45R17 tires

Can I install new tires size 245/40R17 with no problem? Please tell me if you know of any problem this would cause or difference this would make. Including speedometer speed displayed vs actual. thanks
 
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Old 11-07-10, 04:27 AM
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I donít see any problems with the 245/40R17 in the front. In the rear however, you could have a problem. You may have to cut back the wheel wells, to keep the bottom of the well from hitting the top of the tire. This would be especially true with passengers in the rear seat and when going over bumps. In terms of Speedometer Calibration vs. tire size change, click on the link below.


Speedometer Calibration / Tire Size Change Calculator
 
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Old 11-07-10, 03:05 PM
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you are swapping to a tire size that is slightly wider and lower. 2nd number is height to width ratio(they just could not have it done in simple HEIGHT, it has to be some ratio). i did quick math, it's about 2 mm difference in height. from rim to the top of the tire. so, overall, from the ground to the uppermost tip of the mounted tire, it will be several mm-s lower.
with a lower tire, overall tire circumference is lesser than one for a taller tire. hence, at the same engine rpm, it will be covering less distance than a taller tire. your spedo is based on drive axle revolutions, for a front wheel drive vehicle. it will still think you are going XX mph, in reality, it will be slightly less.

i do not think with 10mm difference on the tire width you will hit tire well in tight turns, but that's dependent on how far your steering reaches. everything's possible.

btw, any tire shop and many online stores have charts for safe to use tire sizes. discountire, tirerack, and such.
 
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