[IHIeiniken]

Hey.

im really clueless to what offset i should go with when i purchase some 18-20"s for the CTS. and how offset is measured and so forth.

ive seen people on other threads get a 42mm offset for CTS application of STS wheels.

Basically the look im going for is to have a deep dish rims, and lower the car to have a lil bit of tire and maybe rim lip tucked inside the wheel well. i want to know if i should look for a different offset in order to have DeepDishes without it rubbing the inside of my fenders. im really into the tucked rim look though.

Thanks in Advance
- obviously a Junior Member for asking a dumb question like this...:cookoo:

 

[RobertCTS]

Hey.

im really clueless to what offset i should go with when i purchase some 18-20"s for the CTS. and how offset is measured and so forth.

ive seen people on other threads get a 42mm offset for CTS application of STS wheels.

Basically the look im going for is to have a deep dish rims, and lower the car to have a lil bit of tire and maybe rim lip tucked inside the wheel well. i want to know if i should look for a different offset in order to have DeepDishes without it rubbing the inside of my fenders. im really into the tucked rim look though.

Thanks in Advance
- obviously a Junior Member for asking a dumb question like this...:cookoo:

Dubbed Stealth had some extremely deep dished 20" and lowered. They may have been staggered too.

The ideal size is like the V. 245x45x18" x 8"

 

[Armaan]

I was also wondering about what the limit range is for the offset of after-market wheels. I have a 2006 CTS and was wondering if 40mm offset is ok.

 

[BishopRuger]

I remember someone saying that anything between 38mm-45mm offset should be ok depending on the width of the rim. should stay at or below 8.5, anything above 8.5 width and an offset higher or lower then that range of 38 - 45 could cause problems.

 

[RobertCTS]

245x45x18" x 8" with a 40mm offset.

 

[IHIeiniken]

thanks for the info. is his rims tucking inside the fender? i hope it doesnt rub when he hits bumps. the reason for me asking all this is because my friend bought some new racing HPs for his 97 M3 and the offset was just a bit off so it rubbed on the inside of his fender everytime he went over a bump. eventually had to sell em.

 

[RobertCTS]

thanks for the info. is his rims tucking inside the fender? i hope it doesnt rub when he hits bumps. the reason for me asking all this is because my friend bought some new racing HPs for his 97 M3 and the offset was just a bit off so it rubbed on the inside of his fender everytime he went over a bump. eventually had to sell em.

See..those BMW cats aren't smart enough to roll their fender lips. But you learn it here. Don't tell them!

 

[05CTS]

If you get 20's and drop it than you'll more than likely have to roll the fenders.

 

[odysseus]

Offset is the difference in measurement from the wheel centerline, and the lug mounting surface. A 6" wheel and a 8" wheel with the same offset, means that width is added on the 8" wheel equally on the inside and outside.

The traditional way was to specify 'backspacing' which was the inside of the wheel to the mounting surface. A 6" wheel and an 8" wheel with equal backspacing means that the 8" wheel has the added width only on the outside.

It gets somewhat confusing, but on the CTS, the issue (besides rubbing the fenders by sticking too far out) is the upper A-arm pinch bolt. It sits close to the tire. Stock, we have 51mm positive offset and 225mm wide tires. The V has 42mm positive offset and 245's. So the V added 10mm width to each of the inside and outside dimension but moved the offset out by 9mm. So mathematically, the V tire sits 1mm CLOSER to the upper A-arm pinch bolt.

The key is to not have the tires stick out past the fender lip and rub. 40mm positive offset on 8" wide rims is the common way to do this without damage or rubbing. The max is about 245's on the front, although some run 255's on the front and 275's on the rear. Any bigger and it simply will rub or worse, dent your fender over bumps. Rim diameter has nothing to do with setting offset. The key is tire diameter and width. The offset is the measurement as to how far out it all sits.

 

[Mark VerMurlen]

Great explanation! Thanks!


- Mark

 

[IHIeiniken]

Rims for Smarties!!! thanks for the explanation!

 

[doorknob]

Dubbed Stealth had some extremely deep dished 20" and lowered. They may have been staggered too.

The ideal size is like the V. 245x45x18" x 8"

RobertCTS:

Doesn't the 45 profile result in odometer and speedometer error? Using the Miata tire/wheel tool it looks like a 40 profile results in less than a 0.5% error? Did you have your odometer recalibrated?