245 or 255 tires for rear of 69

[Driftwood]

Have a 69 with Radial T/A 235/60's all around for a few months now. I've decided I want to get a tire with a larger diameter for the rear end to fill out the wheel well and to get the speedometer more accurate. I realize the 245 is a little small and the 255 is a little big compared to the original 215/70 diameter, so not sure which way to go. Any opinions one way or other-- will the 255 stick out from the wheel well or not have clearance? I like the look of a wide rear tire, but I don't want a tire that will stick out of the wheel well and look cheesy. Thanks for any info. Also, this may be a silly question, but will a taller rear tire get a car off the line a little bit faster because it covers more distance per rpm? Maybe this is similar to increasing your rear end ratio? I thought it was an interesting question so I'm asking. Thanks.

 

[69MyWay]

The 255 will work fine. Many people here on the site have done that swap.

When you increase the diameter of the tire, you actuall slow things down. In other words, the taller the tire, the longer it takes it to roll all the way around. This means that your engine lugs harder to start off from a dead start, but is able to travel up to a higher top end speed given the same RPM on two different tire sizes.

A smaller tire is easier to spin, and if sticky enough, can increase your acceleration to a lower overall top speed.

So, 0-60 mph could be a tad faster with a shorter tire because your engine can wind up faster and get you there quicker. 0-120 would be faster with a taller tire because after the initial struggle to accelerate the car from zero mph, it would allow it to stretch out and use the RPM longer.

Make sense?????

 

[SwaveDave]

I have BFG's 255x60's all the way around. They dont stick out of the wheel wells. I used to have BFG's TA's 235x70 ; the TA is a much harder tire . What i found is, for the street, id much rather have the non-TA BFG tires. The ride is softer. The steering response is improved also by going up to the 255's. Traction is better too.

Dave
1970 Coupe

 

[Driftwood]

Makes Sense

That makes sense-- for a quick start you need to overcome the inertia of the vehicle's mass to get to your rpm power band, so you would want to minimize the initial load on the system. A smaller tire decreases the load by requiring less work (i.e. distance) per rpm from the system. I imagine the limits to the beneift of a small tire are all physical-- traction, ground clearance, tread wear, excessive rpms at higher speeds, etc. My rear end is only a 3.08 anyway, so I don't expect to beat very many people off the line. I guess the trick is to get a high rear end ratio matched with a 5 speed with overdrive for quick starts and reasonable rpms at higher speeds.

Thanks for the info-- I think I'll go with the 255 tires.

 

[yakatak76]

i had the 255's/ 60's bfg ta on the back of mine and they did not stick out, but they did rub on the parking brake cable stop. i had non-stock wheels and the offset was about the same as stock, but i had the rubbing problem so went to a 225/60 and they fill the wheel well pretty good and i don't have the rubbing problem anymore.

 

[Driftwood]

255/60 clearance problems

I'm surprised you thought the 225/60 filled out the rear wheel well-- I guess everyone has different opinions on what looks "right". Thanks for the heads up-- I'll get under my car and see if I can measure if the additional (255-235)/2=10 mm to the inside will have proper clearance with the parking brake cable stop.

 

[igasper10]

I recently switched out my rear 225's to 255's on my 74'. They hit the pipes, so I had to cut about 1 inch out of my pipes. I haven't had any other problems since then. They don't stick out of the wells either.

Ian

 

[bossvette]

I have BFG 275-60 on the back and 255-60 on the front

wheels are American Racing torque thrusts 15x8

 

[SR7D1]

Bringing this back from the dead.

Tire discussion is a very popular topic in the Corvette forum. Maybe in the future we can create a FAQ with respects to specific year and size.

My question is posed to C3 owners of 70-72 or so. I own a 1971, SBC with a 4 speed. I posted my Ansen rims for sale in another thread. I have a set of stock corvette 15 X 8 rims (4 inch BS) I wish to install.

All I would like to know, is a 255/60-15 possible without rubbing.

(front or rear rubbing)

Several threads mention it is possible. Then again, several threads say they will rub in the front. (no mention of rubbing in the rear)

I can order 245's if the 255 are going to rub on a stock 71 with no mods. But the tire selection drops from 7 to 4 at tirerack.com.

So for the best selection, I would like to try the 255, but I seem to be reading mixed results when I use the search feature.

After answering the size question, I have a stupid question.

Why is there no hard set rule for what tire fits on a stock 1971 C3 with a stock rim? I apoligize for my ignorance and I have searched this ad nausim for about 2 weeks.

 

[Eden72Vet]

I have 255/60/15 Cooper Cobra’s all the way around on my 72 SBC with a 4 speed. The left front rubs just a little bit on mine when I make a sharp left hand turn. The inside of the wheel rubs the frame a little bit. I was looking at the spots where it is rubbing during the winter, and I don’t think it is doing anything major, so I am just going to try to lay off the really sharp left hand turns.

I really like the looks of the 255/60’s on the C3’s. It gives them a meaner look.

 

[SR7D1]

Thanks Eden72. I am happy to get some feedback about this. I too am waiting out the winter.

Kumho ECSTA STX is the brand I am leaning toward. But we will see.Anyone else have a thought?

 

[Koop]

The 245/60/15 Goodyear Eagle GTII rubbed just a tiny bit on the left front of my car on hard flat right hand corners. I ran that size for over 15 years. The front suspension is aging and the rub was becoming slightly more pronounced so now I run 235/60/15s Pilots all around (no more rub). The Pilots handle far better than the Eagles.

 

[bossvette]

Winter, what winter? side view of my 76

but to be fair, the 76 hasn't been driven since last November and will be going on the lift for brake lines this weekend, but the 97 is being driven daily and only sat for 2 weeks this winter.

 

[SR7D1]

Thanks Everyone! I am getting the rims back today (sandblasting) and will be putting tires on next week.

I am taking the plunge with 255's unless I hear otherwise. I have found a set of Dunlops at a local shop but he only has two. He is looking for 2 more.

I have also seen the BFG and Firestone tires. The Cooper tire is hard to find locally in that size but no cheaper than the BFG/500's.

The Dunlops I found are about $20 per tire cheaper. I was surprised.

 

[Crimson Thunder]

My 245 60's fit perfect.No rubbing at all.I think the 255's look a little to big.

 

[SR7D1]

My 245 60's fit perfect.No rubbing at all.I think the 255's look a little to big.

Too big? Hmmm. Does anyone have a picture of the 255's? I think the 275's posted from above are rather large but not too bad. (no offense)

The 245 limits my selection but if the 255's are sure to rub in the front, I can easily go for 245's.

Still no solid consensus, but it's good to know the facts before commiting to tires.

 

[bossvette]

None taken, if you look real close under the license plate you will see the car is a Male so it has a more aggressive stance :L

 

[winnipeg69]

I have alwalys been happy with my 245 60 15's . I run them on all four corners.

Mike

 

[pgtr]

Have a 69 with Radial T/A 235/60's all around for a few months now. I've decided I want to get a tire with a larger diameter for the rear end to fill out the wheel well and to get the speedometer more accurate. I realize the 245 is a little small and the 255 is a little big compared to the original 215/70 diameter, so not sure which way to go. Any opinions one way or other-- will the 255 stick out from the wheel well or not have clearance? I like the look of a wide rear tire, but I don't want a tire that will stick out of the wheel well and look cheesy. Thanks for any info.

225/70R15 is the tire size you want for your 69.

On pre '78 C3s, 255s may or may not rub up front. Collecting an opinion poll online as to whether or not 255s will fit a pre '78 is not going to be that helpfull in my opinion. It's simply a crap shoot. They may or may not rub the fiberglass but I can pretty much guarantee they will rub the inner fender area at full lock and come uncomfortably close to the fender edge w/o trimming (what the factory did from '78 on). The bottom line is that if you really set on 255s you have to try them for yourself. I suggest setting teh car back down and turning lock to lock and bouncing the car on it's suspension at each fully locked position to determine if it rubs. Many people that claim there is no rub in fact have rubbing they are not aware of (until they notice cracks in the paint...?)

There is only one decent tire in 255/60R15, the Pirelli zero - the rest are entry level non-performance highway radials offering little more than 'cosmetics' - they are posers, not performance tires. Beyond teh Pirelli, the 255/60 size has become a backwater in terms of tire technology and tire performance. Unfortunate for us but fact nevertheless.

Also, this may be a silly question, but will a taller rear tire get a car off the line a little bit faster because it covers more distance per rpm? Maybe this is similar to increasing your rear end ratio? I thought it was an interesting question so I'm asking. Thanks.

The difference is negligible. Far far FAR more important is the characterstics of the tire compound and construction. If you are interested in a quality tire that is a performance tire w/ excellent adhesion characteristics (which I think a C3 deserves) then don't waste your time chasing sizes and find a tire w/ A-temperature rating and a lower treadwear rating and speed rated at H or better. (The A-traction rating is a joke). There's several tires in the 225/70R15 size that have performance potential that will look good on your C3. A true 225/70R15 performance tire will plant itself on the road and leave in the dust a hard compound non-performance poser.

 

[pgtr]

The 245/60/15 Goodyear Eagle GTII rubbed just a tiny bit on the left front of my car on hard flat right hand corners. I ran that size for over 15 years. The front suspension is aging and the rub was becoming slightly more pronounced so now I run 235/60/15s Pilots all around (no more rub). The Pilots handle far better than the Eagles.

Koop nicely illustrates an excellent point here. The GTIIs are non-performance cosmetic posers. The Pilots are A-temperature rated, H-speed rated performance tires. Makes all the difference in the world!

The Pilots, as well as others like the FStone PV41s, General XP2Ks and GY Eagle RSAs etc are true performance tires. The older Cobra GTHs were good I think but last I checked it appears Cooper has since dropped their performance 225/70s in favor of a cheaper cosmetic only tire. Our selection of 15" performance tires for C3s has shrunk again.:ugh