Tire Sizes
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 47
Likes: 0
From: Hamilton Ontario
Tire Sizes
I have a 79 vette with the original 15x8 Rally rims with 255/60R15's. Love the Rally wheels, but am torn and confused about best tire size combo to replace the ones I have now. Here is what I know, 225/70R15 were stock, nice tires but are they too skinny when on the car? Original handling would probably be restored and wouldn't pick up the road rutts as bad. The 255/60R15's also were stock in '79, the beefy tires look nice, but I have heard of people with smaller size 60's on the front with the 255's on the back. I realize this is probably a personal choice kind of question, but I only know how the 255's all around feel and handle. They're ok, but I think there is some improvement to be had.
What are "you" running and why.
Thanks a million guys (and gals if any)
What are "you" running and why.
Thanks a million guys (and gals if any)
Race Director
Joined: Oct 2000
Posts: 12,652
Likes: 3,110
From: Shamong, NJ
The P225/70R15 tires were standard and the P255/60R15's were optional.
The original tire supplied in the 255/60R15 size was a Goodyear GT Radial, and later the Eagle GT. These were probably "state of the art" tires in the 78-82 period, but tire compounds have changed dramatically in the last 30 years. The original Goodyear's were a pretty hard tire, and there are plenty of softer, grippier tires on the market now.
To improve the handling, I would suggest going to a 16" or 17" rim and the equivalent 50 series tire to the 255/60. This would reduce the sidewall flex associated with taller tires, and improve your cornering grip. If you plan to stay with your stock rims, then I would find the stickiest tire compound available in 255/60's, or go to an equivalent 50 or 55 series tire. Of course, when you get into the softer compound tires on the market (such as the various P Zero's), tire wear goes to heck.
Unfortunately, the number of P255/69R15's on the market, is pretty limited.
Running a smaller tire on the front, will not likely improve the handling of the car.
The original tire supplied in the 255/60R15 size was a Goodyear GT Radial, and later the Eagle GT. These were probably "state of the art" tires in the 78-82 period, but tire compounds have changed dramatically in the last 30 years. The original Goodyear's were a pretty hard tire, and there are plenty of softer, grippier tires on the market now.
To improve the handling, I would suggest going to a 16" or 17" rim and the equivalent 50 series tire to the 255/60. This would reduce the sidewall flex associated with taller tires, and improve your cornering grip. If you plan to stay with your stock rims, then I would find the stickiest tire compound available in 255/60's, or go to an equivalent 50 or 55 series tire. Of course, when you get into the softer compound tires on the market (such as the various P Zero's), tire wear goes to heck.
Unfortunately, the number of P255/69R15's on the market, is pretty limited.
Running a smaller tire on the front, will not likely improve the handling of the car.
Racer
Joined: Nov 2009
Posts: 486
Likes: 1
I have 255-45-18 all the way around. Still has a nice side wall with out that big fat bulge from the original rims. I chose those wheels for a few reasons.
1.) Needed a Z+ rated tire (mine are y) to pass tech at the road races.
2.) Needed less tire sway in the corners
3.) 18's allowed for the steeroids kit to work since I changed from stock
4.) they had the right backspacing and offset to fit
I have seen some people have the staggering wheels on their c3's but if you are not going really wide in the rear.. there is no point IMO. C5's and C6's have that but it makes it where you can't rotate your from front to back... only side to side keeping the rotational direction the same.
1.) Needed a Z+ rated tire (mine are y) to pass tech at the road races.
2.) Needed less tire sway in the corners
3.) 18's allowed for the steeroids kit to work since I changed from stock
4.) they had the right backspacing and offset to fit
I have seen some people have the staggering wheels on their c3's but if you are not going really wide in the rear.. there is no point IMO. C5's and C6's have that but it makes it where you can't rotate your from front to back... only side to side keeping the rotational direction the same.
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 47
Likes: 0
From: Hamilton Ontario
The staggering wheels was something I was told about. Didn't expect improved handling, more esthetics I think. I really would like to keep it stock. It's the look I like so 16" or 17" are out of the question unfortunatly. True, limited in the rubber I can use or even get. Keep your thoughts coming. If you have a pic of the 70 series tires on rally wheels, I love to see them.
Racer
Joined: Nov 2009
Posts: 486
Likes: 1
Good website to visually see the size difference along with the numbers..
http://www.rimsntires.com/specs.jsp
http://www.rimsntires.com/specs.jsp
Drifting
Joined: Jan 2008
Posts: 1,962
Likes: 5
From: Schererville IN
Steel Rally rims are also made in 17" and 18" and larger. 
If you want better performance with the retro look, consider a set of the 18" steel rallys. Your tire options are very limited in 15" sizes.
Going to a 65 or 70 series 15" may help to reduce wander in ruts, but will hurt in cornering. As for the wandering you're feeling, have you had your steering components inspected. Worn steering parts can cause the same issues as wide tires on the front.
If you want better performance with the retro look, consider a set of the 18" steel rallys. Your tire options are very limited in 15" sizes.
Going to a 65 or 70 series 15" may help to reduce wander in ruts, but will hurt in cornering. As for the wandering you're feeling, have you had your steering components inspected. Worn steering parts can cause the same issues as wide tires on the front.
Burning Brakes
Joined: Mar 2003
Posts: 891
Likes: 165
From: Oswego IL
On the 74 I used to own I ran 255/60/15 on the rear and 235/60/15 on the front. The smaller size up front allowed a little more fender clearance with no rubbing problems to worry about and gave the car a nice look with the larger rubber in the back.
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Racer
Joined: Dec 2009
Posts: 415
Likes: 10
From: Richmond Va
245/60/15 BF Goodrich. I did not want to go for the staggered look and read some of the guys on here did have a little rubbing issue w/ the 255. The 245s are a little more expensive. I guess because it is not as popular for the muscle cars. I have no rubbing and love the stance w/ these tires. Got mine from Tire Rack. Good price too.
Pro
Joined: Oct 2000
Posts: 558
Likes: 22
From: Vancouver, B.C., Canada
255-15's (front) and 275-15's (rear). TA's on stock rallies. No rubbing issues at all. The 275's on the rear look great. I relocated the E brake bracket, from the side of the trailing arms to the top, to get them to fit. Very easy to do.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Darting around from ruts in roads is not due to the tires...its due to the alignment. Your front tires (probably back ones too) need to have just a slight bit of toe-IN, rather than be perfectly straight (toe-OUT would make them really dart around). About 1/16" for each tire, or 1/8" total) will do it.
I like 245R60-15's for your car; and I think the OD for that tire is about the same as what the stock tire measured...so speedo should be pretty close.
I like 245R60-15's for your car; and I think the OD for that tire is about the same as what the stock tire measured...so speedo should be pretty close.
Drifting
Joined: Oct 2010
Posts: 1,972
Likes: 6
From: Chester Virginia
255 x60r15's
the traction surface on the tires I run, above, is about 25% more rubber area on the road than the original. Since mine is a 30hp over original small block l48 it doesn't have the power to smoke tires at every shift but the grip on the road of these four cornering is extremely good based on my experience.
I've said it before: RoJo corners like an octupus with 16 arms. I don't believe the narrower oem tire sizes would be nearly as good.
I am running the stock 3:36 - 1.0 rear end also. My Trailblazer
SS has a stock 4:10 rear end combined with a four speed 0.7 to 1.0 fourth overdrive gear and runs at 70 mph at lower rpms than the 76 vette does with straight four speed.
If I want more zip in the '76 it's apparent to me that one thing I can do next time I'm in the differential is move up to a 3.73 - 1.0 rear end in it. No engine involvement at all and I don't drive it on 400 mile road trips so that would work if the spirit ever moves me.
Lance P.
I've said it before: RoJo corners like an octupus with 16 arms. I don't believe the narrower oem tire sizes would be nearly as good.
I am running the stock 3:36 - 1.0 rear end also. My Trailblazer
SS has a stock 4:10 rear end combined with a four speed 0.7 to 1.0 fourth overdrive gear and runs at 70 mph at lower rpms than the 76 vette does with straight four speed.
If I want more zip in the '76 it's apparent to me that one thing I can do next time I'm in the differential is move up to a 3.73 - 1.0 rear end in it. No engine involvement at all and I don't drive it on 400 mile road trips so that would work if the spirit ever moves me.
Lance P.
