Definitive Transfer Case Tolerance?

[Blue By You]

I have read a lot about the TC and warranty issues and such. But nothing definitive regarding specific tolerances in rolling diameter discrepancies of wheels and tires.

The 21" OEM setup with 285/35R21 and 325/30R21 tires shows a difference of .7% between front and rear when calculated online. But I've seen people post that the tolerance is even less than .7%, which is obviously not possible.

The wheels and tires I am thinking about buying are the BC Forged 22" setup they have put on hundreds of our cars without any problems according to them. The rolling diameter discrepancy becomes 1.4% on that setup and they mentioned it being below 2% and it would be fine. So I just want to make sure of that.

Does anyone know the specific threshold in percentage difference between front and rear tires that the TC can handle before it suffers mechanical issues?

TIA

[Sophisticated Redneck]

Originally Posted by Blue By You

I have read a lot about the TC and warranty issues and such. But nothing definitive regarding specific tolerances in rolling diameter discrepancies of wheels and tires.

The 21" OEM setup with 285/35R21 and 325/30R21 tires shows a difference of .7% between front and rear when calculated online. But I've seen people post that the tolerance is even less than .7%, which is obviously not possible.

The wheels and tires I am thinking about buying are the BC Forged 22" setup they have put on hundreds of our cars without any problems according to them. The rolling diameter discrepancy becomes 1.4% on that setup and they mentioned it being below 2% and it would be fine. So I just want to make sure of that.

Does anyone know the specific threshold in percentage difference between front and rear tires that the TC can handle before it suffers mechanical issues?

TIA

2 percent does appear to be the real number. I ran a staggered setup that on paper was within one percent but in reality was 3.7 percent when the actual circumference was measured. This was caused by using two different tire manufacturers (Michelin front, Hankook in rear) as the Michelin's were dead on spec but the Hankooks we're actually smaller then they should have been, it appears the tire size is just a suggestion for Hankook. This caused transfer case errors to pop up and the "tugging" sensation when driving after about 5k miles. Recalibrating the transfer case would only fix it for short term. Eventually I went to all Michelins and no more issues

So as long as your tires are truly within the 2 percent spec you should be fine.

[Blue By You]

Originally Posted by Sophisticated Redneck

2 percent does appear to be the real number. I ran a staggered setup that on paper was within one percent but in reality was 3.7 percent when the actual circumference was measured. This was caused by using two different tire manufacturers (Michelin front, Hankook in rear) as the Michelin's were dead on spec but the Hankooks we're actually smaller then they should have been, it appears the tire size is just a suggestion for Hankook. This caused transfer case errors to pop up and the "tugging" sensation when driving after about 5k miles. Recalibrating the transfer case would only fix it for short term. Eventually I went to all Michelins and no more issues

So as long as your tires are truly within the 2 percent spec you should be fine.

Thank you for the info.

[slow_roll]

My Xmas wish this year is for Michelin to offer their Pilot Sport AS4 or equivalent in 21 or 22 varieties for our application.

[Blue By You]

Originally Posted by Sophisticated Redneck

2 percent does appear to be the real number. I ran a staggered setup that on paper was within one percent but in reality was 3.7 percent when the actual circumference was measured. This was caused by using two different tire manufacturers (Michelin front, Hankook in rear) as the Michelin's were dead on spec but the Hankooks we're actually smaller then they should have been, it appears the tire size is just a suggestion for Hankook. This caused transfer case errors to pop up and the "tugging" sensation when driving after about 5k miles. Recalibrating the transfer case would only fix it for short term. Eventually I went to all Michelins and no more issues

So as long as your tires are truly within the 2 percent spec you should be fine.

It's not just Hankook, my Pirelli Ice & Snow in OEM size are a hair taller and about 1/2-3/4" narrower than my OEM size MPSS.

Seems like using the same manufacturer is the key.