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Showing results for tags 'diameter difference'.
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A new owner of 02 996tt with a question about the tires and acceptable rolling diameter differences between the front and rears. I apologize for bringing this question again, did an extensive search here and on rennlist and I am finding a bit of a conflicting information. So far, looks I have come to conclusion that the front to rear tire diameter difference within 2% is predominantly acceptable by forum users that appear to be knowledgeable and factual. Some of them are actually stating to stay within 1% max. But, then I ran into a replay to similar post from a very reputable member who is claiming “as a rule of thumb difference up to 4% is acceptable”!!!. One of the explanations for 1% or less that I have found is that the original P-design setup was with 3 revolutions per mile difference (832 @ R and 829 @ F) which is 0.3 % diameter difference (616 mm (24 ¼”) R (~ 24 3/8” ) and 618 mm F) – almost identical rolling diameters between the axles. I did not have a chance to check for available information in P technical publications to find any design/engineering rational for such interpretation of the original set up. Now, if you allow for 2% diameter difference you are ending up with almost 7 times as much spin differential in the VC, not to mention 13 times as much at 4% diameter difference. 4% also sounds a bit large as the axle center would go up for almost a half inch with the tire diameter increased for 1 inch one over the other (4% at 25.5” reference diameter). I might be wrong on all of this, and I again I did not have a chance to check in P technical publications. I apologize on a long note and appreciate any clarifications and advice as my plan is to try to come up with some out-of-ordinary tire size combinations within the 18`OE rim constraints (strictly driven by limited choices I have here in Canada, plan to control my budget and idea to get started with a good ``starter`` street tire that is not Michelin PS2 :D and slowly to start learning the car - would like to go with Conti DW or Super Sports but struggling to figure out correct sizes ). Thanks.