flyinlow said:You have to keep the circumference the same, otherwise your computer and ABS will complain.
Given the different speed of rotation between the different diameter tires, the ABS will think that the front tires are rotating at a different speed than the rear due to an imminent lockup situation. It will potentially put you in an abs stop mode during driving, if it does not set a code immediately. The traction control system may also think you are in a wheelspin situation and attempt to reduce engine power to counteract it. The only ways around this, short of running the right size tires front/rear, would be to build a frequency converter for the sensors to get them to read the replacement tire/wheel assembly rotational speed as it read the originals, or to have a new sensor ring with different spacing on the teeth to compensate. Neither is a cost effective solution for the average car owner, so the most logical alternative is to use the correct diameter tires.josephra said:I was wanting to do the same thing w/ 18's up front and 19's in the rear with the front tires circumference being about an 1.25 inches different.
Could you explain what you mean by complain?
245/45 x 17 would be 134"Frank said:I think what he means by complain is that your engine lights will start to come on. I think you can probably keep the same circumference with 17's and 18's. I don't know about 18's and 19's. Does anyone know if I ran a 245/45 on a 17 up front and a 245/40 on an 18 in the rear if it would have the same circumference? Thanks.
mlc said:245/45 x 17 would be 134"
245/40 x 18 would be 137.35"
But what's the purpose of running larger rims and then trying to keep the overall diameter the same by using shorter sidewalls? Doesn't make sense IMO.