My 68 currently has 245/60/R14's, and I want to upgrade to 255/50/ZR16's.

The difference in diameter. circumference, and width are pretty minimal between these two sizes, so I'm hoping I wont have interference issues.

Has anyone done this? I am putting Wilwood discs on all four corners and need bigger wheels to accommodate them. Assuming I can find wheels with the correct offset and backspacing, do you see any issues with the bigger wheel/tire combo? I don't want to do any cutting or welding

Thanks for your help.

 

The 17" tire and wheel selection might be better. As far as BS, do a member search for Mr Nick, he has a 68 or 69..

 

I have 245-60-15's on my Cutlass. They are monsters in my opinion. They fit without any rubbing issues but I don't think anything wider will fit without rubbing on the front. Height wise you are good, not sure of the difference in width will cause an issue. If I were to do 16's I would probably go with 245-50-16. As long as backspacing is the same they should fit with no issues.

 

If you're running aftermarket suspension goodies like a Hotchkis front anti sway bar they will rub. I am running 245/60/15s and they hit the bar. No big deal. But they do rub. Stock sway bar, no rub. That is going to look great!

 

So, my "tire guy" is suggesting 255/45/17's on an 8" wide rim for the back, and 225/50/17's on a 7" wide rim for the front. I like the idea of a slightly smaller, skinnier tire on the front ( I know - no tire rotation ). With these sizes, the stance should be slightly tall in the back, but not much - it should actually look pretty level. What do you think?

 

Sounds like a plan.

 

255/60-15 BFGs on stock 15x7 SSII/III wheels fit and clear fine on these cars.

To put this in perspective:

245/60-14 = 25.6" OD
255/60-15 = 27.0" OD
255/50-16 = 26.0"OD

F70-14 = 26.2" OD

 

Do not spend money on 16" rims. They are a dead format like 14" rims.

 

Thanks all - I'll let you know what I end up with.

 

I agree, sizes in 16's are dying off fast. You're better off with a 17 and you can still run a tire with a decent sidewall to keep the classic looks. That said, if you don't drive the car a ton, a set of 16's may last you a good 5 years, and you may want to change things by then anyway.

What Wilwood kit are you running? Some of them require 17" wheels or greater, just an FYI.

 

Hi Mr. Nick - In the front I have kit 140-10510 which has 12.19" rotors and requires a minimum 15" wheel. In the back I have kit 140-13511 which also has 12.19" rotors and requires a minimum 15" wheel. They are both sitting in boxes in the trunk along with my new suspension from Dick Miller including tubular upper and lower control arms and coil overs from QA1. I plan to do all the upgrades at once - I think it will be easier that way - but until I have wheels and tires I can't do anything. To all - thanks for your replies. I appreciate the support. This is an area I simply do not have a lot of experience with, so your knowledge is a real life saver. BTW - As part of this upgrade project, Baker Engineering in Nunica, MI is rebuilding my 455 with a complete roller setup, Edelbrock aluminum heads (ported and polished by Baker), Wiseco +.040 forged pistons and a custom grind cam (also by Baker). The objective is to make around 500+HP/525ftlbs. (Cylinders cleaned up nicely at +040) She ought to be a real monster when complete.

 

I just finished a 4-wheel disc conversion on my 69 Cutlass. Just a couple things that may come up.... be prepared to possibly grind out the rear caliper brackets because the axle housing flares up to a bigger size at the end. Also i had to pull the axles and grind down the axle hub so the rotors would fit. You might not run into the axle hub problem depending on how big the rotors are and how the back side is designed. You will probably end up grinding brackets though. Just a warning lol. Good luck!

 

245 45 17's front and 275 40 17's rear .. Much bigger selection ..

 

Thanks for the heads up - I think.

 

Wow - I'd love to, but seems like I would need to do some sheet metal work ( at least ) to get 275's in the back - no?

 

MT ET street in rear 295 45 r17
MT ST Comp in front 245 45 r17


no mods needed

 

What width are your rims?

 

9.5" Rear
8" front

 

Are they zero offset?

 

Tire guy measured for offset.
Don't recall what it is.

 

Wilwood brakes bolted right up - no issues - no grinding. I ended up with 255/45/R17's on the back, and overall I'm pretty pleased. The rear wheels are 9" with 4.75" backspace, and while there is still a little room I am fairly sure that 275's would not have fit without rubbing issues.
[IMG]C:\Users\kstern\Documents\442\pics\IMG_453[/IMG]

 

Wilwoods front and rear. New engine. At first I was a little disappointed in the peak HP numbers, but this thing is making stupid torque. And on the street - torque matters. Some other improvements made for this winter project:

Tubular control arms from DMR.
QA1 double adjustable coil-overs front and rear.
Ceramic coated headers from DMR
Mini-starter from DMR
All new wiring from under dash to front light harness. All wiring replaced except rear harness.

Engine by Baker Engineering - thanks to T.J. Grimes

It's coming along nicely, and I think I'll be done by March.

 

Nice results! Shift that thing around 5,000-5,200 and that engine will live a long, low stress life.

For future reference, with the correct offset you should be able to get a 275-285 in the back no problem. I'm running 285/40/18 with no issues, and I believe the 68/69 cars have the same size wheel well opening.

 

What rims are these?

 

The wheels are American Racing Torquethrusts Model CL205 from Vintage Wheels in San Diego - thanks Bob Lacey

Fronts: 17 x 8 with 3.75 bs 225/50/R17
Rears: 17 x 9 with 4.75 bs 255/45/R17

I believe Mr. Nick is correct on the wider tires - I can see now there would be plenty of room in the rear, although a deeper backspace would likely be required as there is not much room on the fender side. I was really playing it safe with the 255's. There is lots of room on the frame side - not so much on the fender side with this combo. I'm just not sure how much deeper than the 4.75 I have now with 9" wide wheels would be safe/reasonable.

The wheels were a bit pricey, and I am already $$$$ deep into this project so it may be awhile before the wife allows budget for new ones. I'm actually pretty happy with the way this worked out.

 

Would you provide specifics on your rear wheel setup? Backspace? Thanks!