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Increasing tyre sidewall height on 20" alloys - Printable Version

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Increasing tyre sidewall height on 20" alloys - benzina - 07-12-2011 01:46pm

If one was to fit a slightly bigger tyre, and increase the tyre sidewall height on the 20inch rims, would it affect the automatic gearing, ABS ,or traction control in any way?
We know it obviously affects the speedo, and for example....if the sidewall height is increased 15-20mm, an accurate speedo would read approximately 5% less then the actual speed being traveled.
So the question is...would this modest increase in sidewall height, create any short or long term technical running problems in any area of the car, other then the speedo reading?

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RE: Increasing tyre sidewall height on 20" alloys - RacingSnake - 07-12-2011 02:09pm

it would all still work... but the engagement of various features would operate at a different level to normal.
ie, tailgate will not open past 5mph instead of 3.5mph
HDC will decend at 15mph instead of 12.4mph
Front parking sensors will switch off at 12mph instead of 10mph
etc etc

(figures probably aren't correct but the theory is there).


RE: Increasing tyre sidewall height on 20" alloys - benzina - 08-12-2011 02:14am

Thanks for the answers RacingSnake.... got the theory.Thumbs Up

Just one more question....with the said marginal increase (15mm-20mm) in sidewall height and overall wheel diameter, do you think you would notice any difference in acceleration?.... as a larger diameter has a greater rotational inertia which requires more energy to accelerate. Or in other words: the bigger the wheel, the slower the acceleration.
I would think a marginal increase in sidewall height would NOT really be perceptable in real world feel (not sure about differences in acceleration figures).....would that be right?


RE: Increasing tyre sidewall height on 20" alloys - RacingSnake - 08-12-2011 11:18am

I dont think you would really notice any difference.
The inertia effect will be felt more with heavier (and larger) wheels rather than just tyre wall increase.
I went from 18" aluminium wheels on to 15" steels wheels on my old brabus roadster and the diffence was incredible.... It looked shit, but it flew like a rocket! Lol