I Know: Another Tire Size Question
 

Have a 71 and tried 255/60/15 on the rear and they just clear the EB cable--which I can zip tie to the trailing arm--other then seems to be no clearance issues--but not much clearance. Height 27.1 inches==almost same as the 225/70/15 which would be today replacement tire for the original ones.

Question #1 is which front tire to go with: Choices are:
225/70/15---27.4 inches high
245/60/15---26.6 inches high---gain 1.3 inches intread width but loose height compared to 255/60 or 225/70--biggest issue is does it rub on frame on full wheel lock

Could also go with 245/60/15 all around--that way they could be rotated but lose height in rear/higher rpms no problem with and clearance in rear but still may rub on full wheel lock in front??

Could also go with 225/70/15 all around which is what I have now--but they are 20 years old. They look great but thought a little more tread width would help the traction/handling.

I'm not running the car in road races or the drag strip. Only drive the car from May to November 1 depending on weather and probably put less than 4k miles on the car a year.

I have be debating the tire size question for 6 months in my mind and still can't decide. Appreciate your input/opinions.

Why not 255/60/15 all around. Did you try them on the front ?

A pic of my 69 with 245/60r15's all the way around. No rubbing on the front. The outer tire edge sits inside the wheel arch lip. New spring in the rear that has yet to settle, no spare tire in the carrier and 1/2 tank of gas.


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Tim:

I have a new original spring in the rear--how much does it actually settle over time?

Do the 245/60/15 hit anything on full wheel lock?

Not doing 255/60/15 in front because I figured if 245'a sometimes hit the frame, etc the 255's were sure to hit something.

If you are not pulling g's in turns or trying to go under 13 seconds, the 225-70 may make the most sense. Guaranteed you will never turn a half shaft into a corkscrew.

Settling really depends on the spring you bought. The spring rate will vary from manufacturer to manufacturer and even within a manufacturers production run because of how they temper the leaves, quality control and the quality of steel they use. Also some springs are made to the later heavier C3 specs others are more towards the earlier models. I'm using a 9 leaf 6/3 progressive rate Eaton Detroit Spring from ZIP Corvette. In 200 miles the tire to wheel arch gap has settled from 5 1/2 to 3 3/4" with a full tank of gas and no spare tire. There will be some more drop as it settles but not a lot. Gap should end up being about correct for a stock tire but greater with the 245's smaller diameter and it being a radial tire.

There is no rubbing at full wheel lock.

Not sure about the 255's but I'd be more concerned about increasing stone damage to the fiberglass because of how far they will stick out. Tim

Maybe it's best to go with the 245/60/15's all around. My only worry is they're only 26.6 inches high and 225/70 are 27.4---I guess what's another .8 inches. I have a original 9 leaf spring in the rear and new coil springs in the front which were installed 10 years ago. I also have Bilstein shocks painted to look like originals so my rear height is about 30 in(greater than original specs). My spring has some bow in it--was told it should be straight across (spring has only been on car about 1 year and not driven)--Don't want to large of gap between top of tire and fender lip but on the other hand to want rock ships or bottoming out with the 255's. Probably worrying about nothing--everyone does what they want in terms of wheels anymore. Thought about the new coker RWL radial tires but the costs are $$$$$--crazy.

Thanks for your input.

I would say the 245/50s front and rear. The 255/60s in the front would probably rub. Look at a '78 Pace Car. The front of the front fender and the rear corner of the front fender are trimmed so the tires don't rub. I realize the fender lips are different because the rear opening has a flare but the bottom line is the fenders were trimmed for a reason.

Which tire: Mickey Thompson S/T or BF Goodrich T/A? MT are about $132/ tire and BFG is about $165/tire (245/60/15). I have been reading about BFG white lettering turning brown, having lots of problems with cracking, and same old tread design--not keeping up with other manufacturers. I have never owned MT tires but have had one set of BFG T/A. Don't care wich one I buy.

I have 255 / 60 / R15 on front and back of my 77, no rubbing. Lots of threads and lots of poster will say the same.....but I guess it is possible.

I have Goodrich Radial T/A tires, and the white letters turn brown after awhile, but just like the bugs on windshield, tires get dirty, you have to clean them. I have had none of the other problems you mentioned with these tires, and they go around Pennsylvania roads and turns quite nicely.

I run 245/60/15 BFGs in the front and they fit/look perfect....Looks like what C3s should have came with. On the rear I run 255/60s as they fit perfect and look good... I also now run 275/60s but I relocated the parking brake cable bracket to the top of the trailing arm.

For no mods, the 245/255 combo can't be beat...

No problem.

You will be hard pressed to see a .8 inch difference with a radial tire. Remember you are only talking .4 of an inch less to the top and bottom since its a .4 inch decrease in circumference of the circle.

Most of the tire gap issue will be spring related. You will need to drive the car to settle your spring. It will come down. How much will depend on the spring. Find a rough road to get it flexing and it will come down faster and it will continue to over time. Also make sure the clamp bolts were torqued with the car on the ground and full weight on the spring. Back them off and re torque if you are not sure and also make sure the shipping bands are removed as well.

As for reducing the gap if the spring doesn't cooperate. I'm using stock length spring to trailing arm bolts in the rear and will be close to what I want. If needed a visit to fastenal for a longer bolt will drop you down. An 8" GR 8 bolt gains about an inch of body drop. Pay attention to the end of the bolt if you use a longer bolt. You are lowering the spring end to decrease the arch. If the end of the bolt (or spring) is lower than the lip of the rim it will hit the ground when you have a flat and the amount of damage will increase with the longer the bolt (or further the spring) is below the rim. Make sure to cut off any excess thread and make sure to use grade 8 bolts and nuts.

As for your tire brand question wy car came with new BF Goodrich TA's and I like them. Pick what you want. They're all DOT approved and round.

:iagree:

I was running 245/60/15s all the way around with no problems. Went with the 275/60/15s out back with parking brake mod.

I'm going to buy four BF Goodrich 245/60/15's today. BFG has a sale and I will save $40. I want to thank all of you for your input and help. I is greatly appreciated. Thank You!!

FYI,on my 71 convertible I have 245/60/15s on the front and 255/60/15s on rear. top of the front fender wheel arch is 27.625 and rear is 28.375.

I am also running 255/60/15 in the front and 275/60/15 in the rear with no rubbing on my 73. No modifications either. I can get my thumb between the tire and the parking brake cable mount. The fit on each of these cars is different. Some will work and some won't. I had the tire shop mount up my bfg's and check it on the lift before I left the shop.


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