spare tire question

There isn't an exact cross-match from letter designation tires to metric. I used to sell tires back in the '70s when the changeover took place and there was a lot of confusion in tire sizes, and the dimensions of say, a F70-15 may or may not be equal between a Firestone and a Goodyear, though the load range, or carrying ability was rated the same. The metric system standardized tire sizing and how they were measured.

An F70-15 roughly corresponds to a P215/70R-15 where an F78-15 would roughly correspond to a P205/75R-15. It gets confusing because the aspect ratios are not identical. One has to be concerned about overall tire height more than the actual size designation when making these comparisons.

Not all conversion charts agree either. This is definitely a can of worms.

Hi Guys, I haven't had a Vette for long, but surely the Tyre (sorry 'tire') compartment is made to fit a standard tyre/wheel! Even if you have a skinny emergency - where does the standard size flat tire go you've just taken off? - in the spare compartment? or am I being daft.

Dunno if that helps.
regards - Dave (Blue '77 with 5 same size tyres)

The car will accept a full size tire in the spare compartment, as long as it's a standard or optional size tire when the car was new.

From 78 and up you can only use the spacesaver spare,they made the gas tank 8 gallons larger,no room for a full size spare.my original space saver is still in there,still holds air,still has the factory nubs on it

I have done some research. I found the original F70-15 is just a tiny bit smaller than a 215/70-15, but larger than a 205/70-15. If it existed it would be about a 211/70. This is based on the tire diameters. The Tire Rack guy (and I)was wrong. The good news is the the 255/60-15 is within less than 0.1 inch. Almost perfect.

This morning I bought 255/60-15 Firestone Firehawk Indy 500 with raised white letter. Repainted rims and did the mount and balance myself at the college.
I have also just replaced the master cylinder, front brakes, calipers, machined rotors, replaced wheel bearings, rear rotors, and all flex lines. I just need to finish the rear and bleed them, and for the first time I will have good brakes, and good tires. Slowly coming together.

|UPDATED|7/8/2004 7:43:28 PM (AZT)|/UPDATED|

I have a BFG 235-60-15 TA for a spare and it fits without any problems in carrier, but I run 245 and 255-60's, the 255 barely fit in the bottom half but won't compress enough to get the rear bolt started, I made a longer rear bolt just long enough to get the lower half started and tight enough to get to a tire shop to fix or replace, didn't want to lower the front bolts because my car is low in rear and didn't want to drag the lower half on a bump