7.75 too tight in '65 spare carrier

**Kenneth B.** · December 14, 2011, 06:37 PM

Re: 7.75 too tight in '65 spare carrier

Originally posted by Wayne Midkiff (3437)

This one's probably for Duke W.

I thought that all 7.75's were designed to give 760 revs per mile (w/o considering slippage/squirming or diameter growth at speed).

Pics are both 7.75 non-DOT tires; whitewall is US Royal 'Super Low Profile' 2-ply (4-ply rated). Nice fit in spare carrier.

Blackwall is BF Goodrich 'Custom Long Miler'; 4-ply. Noticeably taller resulting in a tight squeeze into the carrier. Need to wipe contact surfaces with "Armor All", Pressurized to 26 psi. Install with valve facing down, 'cause otherwise it's so tight it won't budge, and I have to deflate to ~20psi in order to pry it out, after (say) 4 months in place. A learned member told me in the past that the Long Miler was a truck tire, but still, it's a 7.75

.

GM made 2 screws for the tire carrier. The optional tires were fatter & needed a longer screw.
KEN

**Alan D.** · December 14, 2011, 07:19 PM

Re: 7.75 too tight in '65 spare carrier

Ken, my understanding is that the second screw was used with the KO only.
That was the one with the nut welded on like the 63 style.
However that would not affect the tight fit due to the diameter, correct.

**Duke W.** · December 14, 2011, 09:31 PM

Re: 7.75 too tight in '65 spare carrier

7.75-15s are speced at or very near 775 revs/mile. This is the actual measured LOADED revs/mile at low/moderate speed, not the "rigid body" revs per mile based on measured inflated OD/circumference.

Modern replacements for old bias sizes tend to run tall.

Take it to a tire shop with a shaving machine and have them shave off half the tread depth. That should provide enough clearance to fit okay.

Duke

**Ronald L.** · December 14, 2011, 09:46 PM

Re: 7.75 too tight in '65 spare carrier

Can't say for certain on 65 but in 66 you have two combinations:

There are two lock bolt lengths.

There are two tub bolt lengths.

KO's come into the mix but BSW WSW and Gold lines are in that as well.

**Dennis O.** · December 14, 2011, 10:05 PM

Re: 7.75 too tight in '65 spare carrier

Just for confirmation, I have the exact same problem with my '67. I was really happy to find a non-DOT 7.75, but it's too big around to fit the tire tub. Shaving the tread would probably do it, since it's so close, but I hate to do it to my nice tire I looked for so long.

**Steve B.** · December 15, 2011, 09:04 AM

Re: 7.75 too tight in '65 spare carrier

Wayne, I would like to know if a non dot 775 BFG silvertown 660 tire which was OEM for the 65/7 corvettes would have the same problem? I seem to remember that they were taller but the difference wasn't as noticeable as in the long miler?

**Kenneth B.** · December 15, 2011, 10:45 AM

Re: 7.75 too tight in '65 spare carrier

Originally posted by Alan Drake (43261)

Ken, my understanding is that the second screw was used with the KO only.
That was the one with the nut welded on like the 63 style.
However that would not affect the tight fit due to the diameter, correct.

The long screw was used in 66/67 for the goldline & redline tires which were wider at the side walls than the stock tire. I had to get the longer screw when I put a OEM redline in the spare tub.
KEN

**James W.** · December 15, 2011, 02:16 PM

Re: 7.75 too tight in '65 spare carrier

Originally posted by Kenneth Barry (7808)

The long screw was used in 66/67 for the goldline & redline tires which were wider at the side walls than the stock tire. I had to get the longer screw when I put a OEM redline in the spare tub.
KEN

Ken.

When you say "long screw" are you refering to the spare tire tub bolts or the lock bolt? I would assume a 1965 with knock-offs and goldlines would have the longer spare tire tub bolts and a longer lock bolt or did the longer lock bolt not appear until 1966?

Thanks,

James West

**Kenneth B.** · December 16, 2011, 10:40 AM

Re: 7.75 too tight in '65 spare carrier

Originally posted by James West (18379)

Ken.

When you say "long screw" are you refering to the spare tire tub bolts or the lock bolt? I would assume a 1965 with knock-offs and goldlines would have the longer spare tire tub bolts and a longer lock bolt or did the longer lock bolt not appear until 1966?

Thanks,

James West

JAMES
I am refering to the screw that holds the lid to the tub & has the lock on it.
PS. a bolt is a screw with a nut on it. If there is no nut it's a screw

**Wayne M.** · December 16, 2011, 02:48 PM

Re: 7.75 too tight in '65 spare carrier

Originally posted by Ronald Lovelace (50931)

Can't say for certain on 65 but in 66 you have two combinations:

There are two lock bolt lengths.
There are two tub bolt lengths.

KO's come into the mix but BSW WSW and Gold lines are in that as well.

Ron, others -- the way I figure it out, with the help of the good GM dwgs. in Nolan's Vol 2, and the '65 AIM, with a sideways glance at the '65 TIM&JG, there are 3 different tub bolts (the two forward hinge bolts); and 2 lock bolt lengths, to cover standard black wall, white wall and goldline tires, and steel rims or KO's. Not sure about the '67 redlines, so someone will have to report.

From late '63 thru 1967 (?) the standard hinge bolts were #3841463, 8_1/2" overall length (O.L.), and the standard lock bolt was #3831464, 6-5/8" from the groove under the bolt head to the threaded end.

In 1964, when KO's were added to the option lineup, the same lock bolt was used, but the hinge bolts were lengthened for the 6" wide aluminum rims, to 9_5/8" O.L. # 3833383 [welded nut used as stop]. No effect on type of factory rubber mounted.

In 1965, with the addition of the wider T01 Goldline tires in mid-year, both a new lock bolt #3872959, 7.5" from the groove under bolt head to threaded end, and new hinge bolts #3872958, 10_3/8" O.L. were used. These "Goldline" bolts were the same whether steel rims or KO's.

Comments welcome.