C2 Tire Size for Tub

[Mark H.]

I am reinstalling my spare tire tub and am curious about tire size to fit in there correctly. I have a 205/75 R 15 and it seems too wide, so that there's a noticeable gap between the tub and the lid. The original tire size was 7.75 x 15. So, would a 195 be a better fit, given today's measuring standards? What about the aspect ratio? What do you you suppose the aspect ratio was on those original 7.75 x 15 tires? Thanks!

[Richard M.]

Re: C2 Tire Size for Tub

Mark, It's not uncommon if you go with the larger tire to be left with extra space between the tub cover and the tub. Here is a thread that has much info on the subject, which also references another thread regarding size concerns.

https://www.forums.ncrs.org/showthre...84350&uid=3829

I chose the 205/70R15 Pirelli P4000 for a '67 I had recently. The diameter is very close to the 7.75x15 stock tire. It is however wider. That size spare left about a inch or so extra space on the tub cover. Not really that noticeable unless you're looking for it.

Rich

[Jack H.]

Re: C2 Tire Size for Tub

Also, understand that you're quoting generic tire categories (7.75x15, P205-75R-15). These DO NOT fully specify the exact geometry of a given tire.

You'll find modest variations in specific tread width, max inner to outer sidewall width dimensions, Etc. across different mfgr/brand/model tires within the same general category...

The tire counterman should be able to crack open his spec book and quote you specific dimensions for you to make side by side comparisons with. That's one of the reasons for there being three different sized spare tire tub hinge pins in use at the factory for mid-year Corvette...

[Richard M.]

Re: C2 Tire Size for Tub

Also, understand that you're quoting generic tire categories (7.75x15, P205-75R-15). These DO NOT fully specify the exact geometry of a given tire.

You'll find modest variations in specific tread width, max inner to outer sidewall width dimensions, Etc. across different mfgr/brand/model tires within the same general category...

The tire counterman should be able to crack open his spec book and quote you specific dimensions for you to make side by side comparisons with. That's one of the reasons for there being three different sized spare tire tub hinge pins in use at the factory for mid-year Corvette...

For our '63 coupe with it's original size spare the tub was fine. When I bought five 205-75R15's for that one, I had to buy the 2 longer forward tub cover hanger bolts for the new radial spare to fit. The originals were too short to be able to close the cover. I recall I bought the extended ones for the later wider tires with the knock-off wheels.

Rich