New 19/20 wheels tcs problems help

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Jul 21, 2012 | 09:04 PM

BEERSNOB

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New 19/20 wheels tcs problems help

Hoping someone can help me out here.Car is an 08 z51 ,I just had a set of 19x8.5 and 20x11 o.z ultraleggeras put on with 255/35 fronts and 305/25 rears and after driving a few miles I started seing traction system active on the dic.What was particularly alarming was feeling the car apply the brakes on it's own.My temporary solution is turning all the nannies off .Can someone please tell me where I went wrong as far as sizes?

Jul 22, 2012 | 12:05 AM

TMyers

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From: Everett Wa

There needs to be approx 1.2 between front and rear wheels, stock is 25.7 front, 26.9 rear. You have 26 both front and rear. Shut off TC and you will be fine.

Jul 22, 2012 | 12:04 PM

BEERSNOB

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Thank you Tmyers for the reply.Are you fairly certain on that number and how much if any wiggle room is there ?I have seen different numbers and percentages thrown around but no definitive answer.

Jul 22, 2012 | 12:22 PM

TMyers

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From: Everett Wa

Probably about 10% either way. My race tires have a difference of .7 and at 98mph TC kicks in.

Jul 22, 2012 | 12:35 PM

BEERSNOB

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I have been driving with tcs off of course but not really a fan of that being a permanent fix.After finding a size calculator it looks like a 245/35 19 and 295 /30 20 have a difference of 1.21.Surely that will fly right ?

Jul 22, 2012 | 12:53 PM

TMyers

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From: Everett Wa

That would be fine.

On second look, no. 245/35 19 has a diameter of 25. 295/30 20 have a diameter of 27. That is a diff a 2 and that will not be good.

Last edited by TMyers; Jul 22, 2012 at 12:57 PM.

Jul 22, 2012 | 01:03 PM

Fly'n Family

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http://www.discounttire.com/dtcs/infoTireMath.dos

I use this when switching tires. Not every tire is exactly the same per size, but this will help give a good idea.

Jul 22, 2012 | 01:19 PM

BEERSNOB

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Ok guys again I really appreciate the input .The Discount Tire calculator and 1010tires.com calculator show the overall diameters to be 25.75 for a 245/35/19 and 26.96 or 26.97 for a 295/30/20 with the difference being 1.21 to 1.22. Am I missing something here ?
-

Section Width: 9.64 in 245 mm

Section Width: 11.61 in 295 mm
Rim Diameter: - -

Rim Diameter: 19 in 482.6 mm

Rim Diameter: 20 in 508 mm
Rim Width Range:

Rim Width Range: 8 - 9.5 in

Rim Width Range: 10 - 11 in
Overall Diameter: - -

Overall Diameter: 25.75 in 654.05 mm

Overall Diameter: 26.96 in 684.78 mm
Sidewall Height: - -

Sidewall Height: 3.37 in 85.598 mm

Sidewall Height: 3.48 in 88.392 mm
Radius: - -

Radius: 12.87 in 326.89 mm

Radius: 13.48 in 342.39 mm
Circumference: - -

Circumference: 80.89 in 2054.6 mm

Circumference: 84.69 in 2151.1 mm
Revs per Mile: -

Revs per Mile: 807.7

Revs per Mile: 771.5