JPCorvetteC3

Hello,

I'm looking for new tires for my '71 and I've decieded on the BFGoodrich Radial T/A's and will be putting the 225/70/R15's on. I currently have four Goodyear Eagle GT's and have determined that they are quite old and I have also determined that the spare is the original.

Today, I took the Goodyear off the right rear to see if it would fit in the tire carrier( the BFGoodrich's are the same size) and determined that the 225's are too wide for the carrier. So, I was thinking of getting four 225's for each corner and getting one 215 for the spare. Does my logic make sense or will the 215 be a bad idea in the event that the spare tire needs to be used?

Any help or ideas will be very helpful.

Thanks everybody, take care,
Jason

DUB

The two long bolts that are in your frame that the lower portion of your spare tire carrier hangs on when it is down.... can be adjusted to accommodate the wider tire.

BECAUSE..having your spare be a different size is one thing...BUT...how are your going to stow away the flat tire when you need to use the spare??? Because I have had them come in my shop with the flat tire in the passenger seat.

DUB

tracdogg2

Jason,
The spare tire tub is adjustable. Loosen the two long bolts at the front of the tub to adjust for tire width.
Mike

Dub beat me to it.

JPCorvetteC3

Thanks for responding. I had considered doing that, but I had myself convinced that the bolts had to be tight to the frame. Please forgive me, this is my first Vette, there's much to learn.

Cheers!

Alan 71

Hi JPC,
I believe you'll find that single bolt at the rear of the tub is adjustable too.
There's a threaded 'slug' that the bolt threads through. This 'slug' gives about 1 1/2" of adjustment.
The forward bolts are adjusted after loosening their lock nuts.
Good Luck!
Regards,
Alan

The rear bolt… as you tighten it up the extra length passes up into a opening in the rear crossmember.
The 'slug' looks like the end of a barrel in this picture. (Maybe it's called a 'barrel nut'?)


One of the 2 forward bolts showing the lock nut and some of the adjustment on the bolt.

JPCorvetteC3

Thanks Alan, good pictures. I'll try again tomorrow and see if I can make it work, as it appears that this will be a trail and error situation. I will update the post with my results.

Cheers!

rvazquez

I have a 1972, and my BFG radial T/A spare which is 225:70 R15 fits nicely in the spare tire tub, I'm sure you can get it to fit in there
Regards
Roy

7T1vette

F70-15 tires are equivalent width to a 215 radial tires, so 215's should easily fit in the tub. I have 235R60-15's all around on my '71 coupe and the outer diameter of that tire is the same as the F70-15's. I'm pretty sure the spare tire tub can handle 1 more inch of width with the adjustment it has. (My tire tub has ONLY held the [unused]factory original spare tire, however.)

P.S. I highly recommend going with 235R60-15's. That's as wide as the front wheelwells will accept without having some risk of rubbing during full-turns.

DUB

Not knowing what you had on the car BEFORE you put a new set on....if you are changing the tire size enough...mainly the circumference...it can throw off your speedometer.

Also...not knowing if the car has power steering or not....having a wider contact patch of thread can cause for some more effort in turning.....but as most people know who have manual steering. You get the car moving and then begin turning the steering wheel.

I did not want to comment on the size of the tire chosen is different to what the car originally had when converted as like '7T1vette' mentioned.

DUB

JPCorvetteC3

I got the Goodyear to fit after dropping all the bolts, but I really had to push up on the carrier and I really had to pull on the back bolt to get it all to work. Is this the way your spare tire fits?

The front bolts have 3/8" threaded into the frame, I dont want to take more out and the back bolt is threaded out as far as it can.

7T1, I'll look into those tires, but I like the way the 70 series fills the wheel well. Could you attach a picture so that I may see how it looks?

Thanks fellas!

JPCorvetteC3

Hi DUB,

The car came with the 225 Goodyear's and I was thinking of putting the 225 BFG's on as a replacement. The car has manual steering, so I understand your concern with a wider tire.

Does anybody know if there is an aftermarket front bolt with a longer thread?

DUB

It will not necessarily be longer threads....but the distance of the bolt from where the threads stop and the end of the bolts that touches the tire carrier.

I know many things....but the lengths of the front bolts for the spare tire carriers is something that I do not know right off the top of my head. SO...the length of it needs to be known...and you may have to get a few to see which one will work. You may have to go back the the 1963-1967 era and look at them.

Some of these tire carrier bolts go all the way in and stop...and others look like what 'Alan71' shown in his photo where you can see that the jamb nut can adjust the tire carrier bolt.

DUB

JPCorvetteC3

I read on another thread that the front bolts found on the later C3's was longer to compensate for the wider tires used in that era, I may look into that as an option. The bolts found on my car are the exact same depicted in the pictures Alan71 attached.

7T1vette

You must extend the two 'forward' tub retaining bolts to get the most depth out of that spare tub. You can't just get enough by extending adjustment on the rear bolt.

Here's a better photo of my car with 235R60-15's on it...

Iceaxe

245R60-15's also fit with no issues on early year C3's and is a BF Goodrich size.

Bally

I think you're on the right track with 225/70's, they look great on early C3's, and according to some of the posts above, it seems they will fit in the tub of the carrier.

Here are some overall diameter comparisons of the various tire sizes being used on early C3's nowadays:

235/60/15 26.1"
245/60/15 26.57"
255/60/15 27.05"
275/60/15 27.99" (have only seen these used on the rear)
215/70/15 26.85"
225/70/15 27.4"

Here are the dimensions of the original type F70-15:
(Goodyear Speedway Wide Tread)

overall diameter= 26.97"
section width= 8.95"
tread= 6.5"

235/60's are OK up front, but look a bit too small in the rear wheel wells of a C3 - they are actually almost an inch less in diameter than an original size F70-15.

Here is a tire size comparison calculator with all dimensions:
https://www.tacomaworld.com/tirecalc

Best of luck!

7T1vette

245 and larger width tires will fit into front wheelwells of SOME of the early C3's. 235's will fit into ALL of the early C3's.

Iceaxe

I've never met anyone that had issue's with BFG 245's, can't say the same for 255/60-15.

When I was in high school in the early 70's I worked in a tire shop and the most popular early C3 Corvette tire replacement was a G60-15, which is almost a direct replacement for a 246/60-15, and never had interference issues. We did hundreds of sets of tires.

G60-15 - 26.4 diameter 9.7 section
245/60-15 - 26.6 diameter 9.8 section

YMMV

DUB

Hopefully if you get the longer bolts it will correct your spare tire issue...which I believe it should.

DUB

JPCorvetteC3

I lowered the front bolts again and got the 225 Goodyear to fit! There wasn't much tthread threaded into the frame though, maybe a 1/4"? I tightened up the nut and lock nut, it seems fine. I was going to stop in at my local Corvette shop and see what they recomend on this issue. Eitherway, I can finally get some new rubber for the car.

Thanks for all of your help, it has not been wasted.