Configure for Different Front & Rear wheel combination

[Hermie]

Looking for guidance on adjusting for different wheel combination.

Rear. 275/40 R18 Circum = 2125.8mm Rev 756 per mile - 470 per km

Front 245/40 R18 Circum = 2050.4mm Rev 785 per mile - 488 per km

What settings do I need to change to keep ABS and speedo happy.

 

[Hermie]

Help still need - 69 Mustang running BF XR 8 running gear, ABS and all wiring.

Don't want to mess up the ABS now that it all seems to be communicating with out fault codes

[Hermie]

Or maybe the better question is does anyone know what % difference before the ABS trips a code.

Above combination gives me a 3.7% speed error factor front to rear. 

If I change the rears to a 275/35 error factor would be 0.4%

Any advice would be great. Thanks

 

 

[scotty]

Can't remember if it was 3% or 5% that would cause issues.