Spare tire lock

[Rex T.]

I have 2 extra spare tire locks. How do I identify what year they are for?

Thanks,
Rex

[Gary B.]

Spare tire lock

Rex,

There are some easy ways to tell the locks apart. First of all, what is the diameter of the stainless steel bezel where the key inserts? There were only two sizes; a smaller diameter for 63-66 and a larger diameter starting in '67. The larger bezel has the lock release pin fully contained within the bezel area; the 63-66, smaller bezel has the lock release pin bisected by the bezel periphery. All 67-79 locks are basically the same except for keyway (B, D, K, and H). Early '63 locks did not have a weep hole; mid-63 thru 65 had a 1/4" weep hole; 66 had a 3/8" weep hole.

Gary

[Rex T.]

Re: Spare tire lock

Both have the larger bezel and a 3/8 weep hole. One has a GM K coded key in it and the other has a generic key (numbers B51 S1098D, probably from Wal Mart or Ace Hdwe). Just curious as to what the original application may have been.

Thanks,
Rex

[Jack H.]

Re: Spare tire lock

In 1967, locks on GM cars changed to increase the number of permutations to thwart the possibility of an owner of one car being able to accidentally enter another, similar car. I believe old Ralph Nader may have been an impetus for this change/improvement.

Anyway, the change consisted of adding a fifth wafer/tumbler geometry to the four that existed AND adding keyway encoding to the shaft. The keyway coding (A, B, C....stamped on the key) was changed each year with the sequence repeating in 4-year cycles.

So, to tell what you other lock with 'Wal Mart' key is a correct match for, you have to test it. If it's from '67 and later years (and is untampered with) the specific keyway code will tell you what sequence of years it fits.

Consider 1967, the keyway codes were A and B. In 1968, they were C and D. A good lock should accept on the style of key its coded for (a 'B' key for a '67 lock) and reject other codes. That means a 'B' key will fully enter the lock while other coded keys will only insert partially (maybe as far as 75% in).

So, you test the lock to determine which keyway coding it has. If it's a 'B' then it matches 1967, 1971, 1975, Etc. cars....

[Gary B.]

Spare tire lock keyways

Rex,

The K keyway is correct for '70, '74 and '78 spare tire locks. The B51 key has a D keyway and correct for '68, '72, and '76 spare tire locks.

Gary

[Rex T.]

Re: Spare tire lock keyways

Thanks Gary. I appreciate your help.

Rex