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YOUR RESEARCHRear tires on a C4S
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Run 40/35 setup
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Suggestion
I would love to be told I have the wrong information, as I would really like to run the 40/35 setup on my C4.
Leading evidence: 'Run 40/35 setup' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Run 40/35 setup' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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The rear tires on the C4S are 295/30 and the fronts are 225/40, so the side wall is a bit smaller. Can I get a tire with a higher side wall in the rear or would that cause problems?
With the suspension lowered with H&r lowering springs, it just seems like the back of the car is lower than the front visually. Not sure if it is or if it just looks that way because the tire wall is narrower.
suggestions?
You'll have to do some searching, but there are postings on the required sizes of tires for C4S. Specifically, due to the differentials, the front tires have to have a slightly larger circumference than the rear. They supposedly need to rotate slightly slower than the rear.
I also wanted to go one sidewall profile up (from 30 to 35) on my C4, but was told that could damage my drivetrain. IIRC, the side wall number is a percentage of side wall to tread width. My impression is that the stock 40/30 front to rear side wall differences (for the all wheel drive cars ONLY) was to keep the tire circumferences very close to each other so the REVS PER MILE (RPM) front and rear remained within a certain spec. For instance, a 225/40x18 and 295/30x18 set up has a front to rear difference in diameter of .1" (25.1" front and 25" rear) and an RPM difference of 826 and 829. A 225/40x18 and 285/35x18 set up has a front to rear difference in diameter of 1" (25.1" front and 26.1" rear) and an RPM difference of 828 and 795. I believe that the 40/35 setup difference is too much for the all wheel drive system to tolerate. I would love to be told I have the wrong information, as I would really like to run the 40/35 setup on my C4.
Note that different tire brands may have slightly different numbers.
They need to be within 3% of tire speed. Take a look at tire calculators online and compare sizes. If one of the tires is more than the specs you will put undue stress on you front diff. I have used this tire calculator from Tacomaworld.com.
https://www.tacomaworld.com/tirecalc
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