Vics86

after finishing front disc brake conversion i need to go from 14 to 15 inch rims.

So purchased us mag indy slotted rims two 15x7(3.75" backspace, -5mm offset) for the front, and two 15x8(4.5" backspace, +1mm offset) for the rear.

Anyone see any issues with cooper cobra gt size 235/60/15 for front, 9.1" wide tread, and 255/60/15 for rear, 10.2" wide tread ? That seems to be the recommended size consensus looking at past posts here.

I was considering perhaps 215 on front and 245 in rear. I just dont want tire rub in rear wheel well even though the car has air shocks for adjustment.

1972 olds cutlass s

Thanks!

69oldsguy

Tire sizes are very preferential as long as there are no rubbing issues. After that it all comes down to the look you like. I would do your 215 and 245 stagger. But that is MY preference. Find cars that you like the look and find out what size tires they're running. Good luck.

joe_padavano

Every 1972 Cutlass that left the factory with disc brakes came with 14" rims.

redoldsman

Do you think maybe he used aftermarket parts? He asked for advice in tires.

Vics86

true, i have less than 1/4" of space between new caliper and old 14" rim. i did not buy disc conversion with smaller rotor to fit 14's. so yes it looks like 14's would work but would be pretty tight. The conversion kits for still maintaining 14 inch rims have rotors that are smaller by a half inch in dia. . .

joe_padavano

One more time. The factory disc brakes were not the aftermarket ones with the tiny rotors, the were the 10.75" rotors (that most people round off to 11") and the large bore D52 calipers. 14" wheels clear just fine. Aftermarket kits that duplicate the factory parts also clear 14" disc brake wheels, despite what every brake kit vendor says. Those aftermarket kits with tiny rotors are a fabrication of some rocket scientist in the aftermarket and provide less braking force than the original drums.

Koda

As can be read, these are Cooper Cobras 225/70/14s on factory SSIIs on a car with factory disc. I like them, so far.

Cosmic Charlie

My 69 Cutlass Vert has the Cooper Cobras P255/60R15, now 2 years old on15-7 SSIIs -, no rubbing, no issues, I like them
They seem to ride best at 35 psi cold & 38 psi hot - go figure
I got all 4 the same size for full rotations and like the fronts with a beefy look as well - others seeing them agree
I had to change the M20 Speedo gear for correct readings
Last year they were about $50 cheaper per tire than the BF Goodrich - from Amazon - free shipping

Fun71

If you want staggered tires, I would agree with your choice of the 235-60 front and 255-60 rear. I had that setup on my car at one point back in the 80s or 90s; I chose that for the shorter front sidewall for handling (reduced sidewall flex). I have since opted for the same size all around for rotation purposes and have 245-60-15 (previously had 245-60-14). I tried 255-60-15 on front but they rubbed on full turns - that likely depends upon the vehicle’s front spring condition and height. At that time my car had 30year old original springs that were likely sagging a bit.

Vics86

I went with 235 60 15s in front and 255 60 15s in back but i bought some Mickey's instead of Coopers. Im going for the vintage look for back in the day my dad had this car running. I just upgraded to 15" slots instead of keeping the 14's he had that were pretty tarnished. I think the taller tires in rear may drop the gear ratio from 4.11 to about 3.90 so i hope that doesn't mess things up but i think they will gain me some rpms at 55 to 60mph.

The us mag slots added more bling than anticipated.


Getting closer to finally turning over the 400 E block my dad had Kirn Racing build back in the 70's. this thing is manual shift , B&M TH400, so hopefully i can find a decent shifter cause i dont want to be shifting through the column all the time like my dad did. I thought about putting an automatic valve body in transmission with the typical 3-2-1 shift pattern but i dont think i will because i want to keep the car as close to vintage as possible. So will keep the manual th400 with 1-2-3 shift pattern.

ben442

I also move to 15" wheels this past year. BFG black wall out- 225 70 15 up front and 275 60 15 out back.
As a result I needed to alter the tail pipes so not to rub,

RetroRanger

Nice72 That looks real good Vics86. Crazy what some paint and elbow grease ( and some new parts) will do.

one option for shifting could be the factory auto floor shifter w a console. A recently availible part for the factory shifter will allow it to be slap shifted when warrented. Ie start in first jam it to 2 where it hits a stop, jam it to 3 where it hits a stop, look back and see the opponent has stalled at the start line. The original gate on the factory shifter does not have the stop between gears and one could easily over shift to 3 or neutral by mistake.

you could probably find a decent console and shifter set up for 4-800 depending on location, condition, and seller. This would look original (assuming you have bucket seats) and allow for original (or repop) parts to be used.