265/35R18 on a cutlass

marcar1993

marcar1993

G-Body Guru
Aug 31, 2007
662
149
28
New Jersey
#1
I am ordering a set of 18x8 4.5" backspace wheels to go all the way around on my car. What is the widest tire I can fit in the wheelwell all the way around with that backspace without rolling the fender lip?
I'd like to fit a 265/35r18 which is 25.3" tall (is that too short?) and 10.7" section width. If I can get away with it, even a 275/35r18 which is 25.6" tall (closer to stock diameter I think) with a 10.9" section width. I also realize the widths might be a touch bigger since I'm putting them on an 8" rim instead of a 9.5" as measured.
The car will be about 2" lower when all is said and done, and I plan to run the same size on all 4 corners.

Please let me know if I'm absolutely nuts and there is no way I'll be able to turn with these tires and a ~2" drop. I was thinking the 265/35 being a touch shorter than stock might help, but will it look ridiculous and too small?
Thanks!
 
UNGN

UNGN

Comic Book Super Hero
Sep 6, 2016
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Southlake, TX
#2
4.5" BS on an 8" rim is going to be very close to the frame in back with any tire more than 255 wide. The fender Lip likely won't be the problem. With 4.5" BS, a 9" rim would work better in back, then 275's should fit with the fender lip rolled. 265's and 4.5" BS on an 8" rim, I can see .250" wheel spacers needed in back, but it will allow tire rotation.

Running the same offset, wide wheel all around is problematic on a Gbody. The ideal offset varies about 3/4" from front to back (the front wants more positive offset (wheel in), the rear more negative offset (wheel out)), especially if you see big brakes in your future.

For an 18" wheel, the ideal offset in front is +.25" with stock brakes and +.60 with big brakes. In back, the ideal offset is -.25 to -.4" for frame clearance, without too much that the fender lip becomes a problem. On a small fendered car like a cutlass, you stay towards the lower end in back.
 
marcar1993

marcar1993

G-Body Guru
Aug 31, 2007
662
149
28
New Jersey
#3
Thank you!
So you think the 265 will fit all the way around with a .25 spacer in the back? What do you think of a slip on spacer with extended lugs for racing and cornering, is it safe?
Also, what do you think of the tire height?
 
UNGN

UNGN

Comic Book Super Hero
Sep 6, 2016
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#4
Longer studs, spacers are fine to about 3/8", as long as they are flat and kept tight.

Any more than 3/8' I would jump to 1.3" or larger and wheel adapters (and wheels with 1" more BS).

Taller street tires are better for launching without wheelspin, but 25" will be fine, if a little rough riding. 265/40's are 26.3 and are closer to the stock size.

Though the 4.5" BS in front puts the tire pretty close to where it needs to be, on a lowered car, 265 wide in front is going to need 1) stiff springs, 2) tall balljoints and 3) inner fender surgery to work without banging the fender on every bump.
 
marcar1993

marcar1993

G-Body Guru
Aug 31, 2007
662
149
28
New Jersey
#5
So stick with 255s?
A 255/40 is 26" and 255/35 is 25", 245/40 is 25.7 which is what my current 245/45r17 measure to, but it isn't lowered yet.
 
UNGN

UNGN

Comic Book Super Hero
Sep 6, 2016
2,595
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Southlake, TX
#6
I'm putting 255/40R18's on my Jaguar 8" rims. The tire mfg's don't recommend 255/40's on an 8" rim, but that is actually the factory Jaguar size in 1998.

I think I'm going to try the Firestone Indy 500 tires, since its going to be a "Daily Driver" I don't need $200/per tire tires that wear out in 15K miles. The Indy 500's are cheap and have good reviews at Tirerack.com.
 
marcar1993

marcar1993

G-Body Guru
Aug 31, 2007
662
149
28
New Jersey
#7
Those are the tires I'm probably going to buy as well. My friend has them on his 4th gen f body, and they are a great tire that is street driveable and still low treadwear and sticky.
I'l probably order tires tomorrow then. Any suggestion on a good place to buy from other than tirerack?
 
UNGN

UNGN

Comic Book Super Hero
Sep 6, 2016
2,595
1,967
113
Southlake, TX
#8
Those are the tires I'm probably going to buy as well. My friend has them on his 4th gen f body, and they are a great tire that is street driveable and still low treadwear and sticky.
I'l probably order tires tomorrow then. Any suggestion on a good place to buy from other than tirerack?
If you order from tirerack, you have to "have a guy" to mount/balance them or its cheaper to buy from Discount. Some tires only tirerack carries, (like Rivals) so I "have a guy" for those tires. I always check with my local discount to see what they will do before ordering from Tirerack. I don't go to NTB or Firestone anymore (even for Firestone tires). I trust Walmart/Sams for batteries, but they lock up on me when you aren't putting OEM size wheels/tires back on car, so I gave up on them.
 
marcar1993

marcar1993

G-Body Guru
Aug 31, 2007
662
149
28
New Jersey
#9
Ill look up discount tire, but i dont think i have one near me though.
I have a few options for mounting. If I can get to the local high school during school hours, I'm friends with the teacher so I can just mount and balance myself. (I'd prefer to do that with brand new rims!) Otherwise I do have a guy who can mount and balance for me and they couldn't care less what I bring them to mount!

Thanks for all the help!
 
UNGN

UNGN

Comic Book Super Hero
Sep 6, 2016
2,595
1,967
113
Southlake, TX
#10
I try to avoid the "chains" for my own stuff because they have corporate rules they have to follow. They frown on 275 wide tires on 7" rims or 45 series tires on 15X8" rims.. At my tire place, the owner does my stuff. He comes out of his office and sends his monkeys off to sweep the shop/pick up trash in the parking lot/go "on break". I get the impression they have screwed up nice rims in the past.
 

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