255/275 correct offset specifictions

professor · 10-04-2008, 04:23 AM

I am looking for the correct offset specifications for custom 18 inch wheels with a staggered 255/275 tire setup without fender rolling. I'd appreciate some advice please from those who have done this or are otherwise in the know.

mikeo · 10-04-2008, 07:23 AM

I haven't tried those sizes, mainly because I was having issues with 245/265 on Breyton GTS-Rs. I've learned that our cars do not like tall tire fitments if they are close to the fender lip. Some general observations based on my experience:

1. 8.5" wide fronts will likely be max width without fender work, and offsets of 38-41 are pretty close to optimal for that width. A 255x35 is 25" diameter compared to the OE 215x40 at 24.8", so that's pretty close in diameter. The problem in front is the fender/bumper cover mount bracket and you will surely need to dremel that for extra clearance but may be able to avoid any fender rolling if your car is not lowered. I'm pretty sure I can get 245x35 in front on 8.5" width with et43 even though it would be extremely close to the strut. With 255x35 I expect you will need camber plates to get around -3.0 deg. camber to help avoid the fender lip.

2. In the rear there is a lot more space in the fender well but it takes a lot of offset to use it. For 9" or 9.5" rear wheels the Berk Technology folks have said an offset of et60 would be just about optimal and I think they are probably on the right track. I would add that a 275x35 tire with a diameter of 25.6" may be more problematic than the slightly wider but shorter 285x30 with a 24.8" diameter.

Just my unverified opinions, so good luck and keep us posted.

professor · 10-04-2008, 07:48 AM

thank you for that useful information mikeo. i should have mentioned that i do intend to use camber plates and am not looking to lower my car much if at all. most importantly i am hoping to lower the tire width differential front to back in a non-staggered setup while going up a few sizes so i'd much prefer a 275 rear if the "PNP" type solution berk technology is suggesting works. but your heuristic about avoiding taller fitments is pertinent too. i wish there were some tasteful forgeline, hre or enkreuz solutions to this...

mikeo · 10-04-2008, 08:18 AM

You're welcome, and do keep us posted (and pics ;-)

WAY · 10-06-2008, 09:04 AM

At a negative camber of 3.0, you are looking at the bare min space between the strut and inner tyre with a OEM set up. Hence, I would be going for an offset of et33-35. For the rears, et60 is about right.

mikeo · 10-06-2008, 09:27 AM

Quote:

Originally Posted by WAY

At a negative camber of 3.0, you are looking at the bare min space between the strut and inner tyre with a OEM set up. Hence, I would be going for an offset of et33-35. For the rears, et60 is about right.

Way, I'm not clear on the meaning of that comment. The strut/spring and wheel/tire move as a unit with camber plates so tire-to-strut clearance should be nearly constant. Have you found that to be different?

WAY · 10-07-2008, 12:42 AM

Good question Mikeo. I don't know the answer, but unless the stock setup has 5mm between the strut and inner wheel, then I suspect tyre to strurt clearance isn't constant in our cars.

MINI135i · 10-07-2008, 07:38 AM

Weird....It seems they would both move together. The only variable should be the tire/rim width/offset when it comes to tire/strut spacing?

Camber is often limited by the spring or top hat hitting the inner fender well, however.

Car is still in transit so I'll have to wait to verify.

10-04-2008, 04:23 AM	#1
professor Major 46 Rep 1,473 Posts Drives: Z4 M40i Join Date: Mar 2008 iTrader: (0)	255/275 correct offset specifictions I am looking for the correct offset specifications for custom 18 inch wheels with a staggered 255/275 tire setup without fender rolling. I'd appreciate some advice please from those who have done this or are otherwise in the know.
	Appreciate 0 Tweet Quote

10-04-2008, 07:23 AM	#2
mikeo Santa Fe Concorso 103 Rep 2,984 Posts Drives: '11 M-sport 328i, '13 X1 28i Join Date: Jul 2007 Location: Santa Fe, NM iTrader: (3)	I haven't tried those sizes, mainly because I was having issues with 245/265 on Breyton GTS-Rs. I've learned that our cars do not like tall tire fitments if they are close to the fender lip. Some general observations based on my experience: 1. 8.5" wide fronts will likely be max width without fender work, and offsets of 38-41 are pretty close to optimal for that width. A 255x35 is 25" diameter compared to the OE 215x40 at 24.8", so that's pretty close in diameter. The problem in front is the fender/bumper cover mount bracket and you will surely need to dremel that for extra clearance but may be able to avoid any fender rolling if your car is not lowered. I'm pretty sure I can get 245x35 in front on 8.5" width with et43 even though it would be extremely close to the strut. With 255x35 I expect you will need camber plates to get around -3.0 deg. camber to help avoid the fender lip. 2. In the rear there is a lot more space in the fender well but it takes a lot of offset to use it. For 9" or 9.5" rear wheels the Berk Technology folks have said an offset of et60 would be just about optimal and I think they are probably on the right track. I would add that a 275x35 tire with a diameter of 25.6" may be more problematic than the slightly wider but shorter 285x30 with a 24.8" diameter. Just my unverified opinions, so good luck and keep us posted. __________________ Santa Fe Concorso - The Southwest's Premier Automotive Gathering.
	Appreciate 0 Quote

10-04-2008, 07:48 AM	#3
professor Major 46 Rep 1,473 Posts Drives: Z4 M40i Join Date: Mar 2008 iTrader: (0)	thank you for that useful information mikeo. i should have mentioned that i do intend to use camber plates and am not looking to lower my car much if at all. most importantly i am hoping to lower the tire width differential front to back in a non-staggered setup while going up a few sizes so i'd much prefer a 275 rear if the "PNP" type solution berk technology is suggesting works. but your heuristic about avoiding taller fitments is pertinent too. i wish there were some tasteful forgeline, hre or enkreuz solutions to this...
	Appreciate 0 Quote

10-04-2008, 08:18 AM	#4
mikeo Santa Fe Concorso 103 Rep 2,984 Posts Drives: '11 M-sport 328i, '13 X1 28i Join Date: Jul 2007 Location: Santa Fe, NM iTrader: (3)	You're welcome, and do keep us posted (and pics ;-) __________________ Santa Fe Concorso - The Southwest's Premier Automotive Gathering.
	Appreciate 0 Quote

10-06-2008, 09:04 AM	#5
WAY Brigadier General 458 Rep 4,822 Posts Drives: Fast ones Join Date: Jul 2007 Location: Melbourne, Australia iTrader: (0)	At a negative camber of 3.0, you are looking at the bare min space between the strut and inner tyre with a OEM set up. Hence, I would be going for an offset of et33-35. For the rears, et60 is about right.
	Appreciate 0 Quote

10-07-2008, 12:42 AM	#7
WAY Brigadier General 458 Rep 4,822 Posts Drives: Fast ones Join Date: Jul 2007 Location: Melbourne, Australia iTrader: (0)	Good question Mikeo. I don't know the answer, but unless the stock setup has 5mm between the strut and inner wheel, then I suspect tyre to strurt clearance isn't constant in our cars.
	Appreciate 0 Quote

10-07-2008, 07:38 AM	#8
MINI135i Second Lieutenant 139 Rep 268 Posts Drives: 2019 M2C and 2013 FR-S Join Date: Jun 2008 Location: Phoenix, AZ iTrader: (2)	Weird....It seems they would both move together. The only variable should be the tire/rim width/offset when it comes to tire/strut spacing? Camber is often limited by the spring or top hat hitting the inner fender well, however. Car is still in transit so I'll have to wait to verify.
	Appreciate 0 Quote