Space Saver Spare for the Vixen

Background

One of the first things I noticed about my Vixen when I got it home was that I had to unbolt the hoop for the trunk lock in order to get the full sized spare out. Also I about sprained myself lifting that thing. Not a good. No wonder so many have spares mounted at the rear. but that limits access to check the oil and require rerouting the license plate and back up camera.

Early on I saw mention of people using a space saver tire from a Cadillac instead of the full sized spare but the issue to me was making sure a space saver could support the load. Checking proved that some caddys did use a T145/80Dx16 spare it is a smaller diameter (see below) but does have a 105 (2040 lb) load rating.

The spare can be found in RWD Caddys and RWD Buick Roadmasters of the '90s. The one I have has a wheel code of "RDM". The othe number appears to be a date code, 51st week 1992.

Rear Issue

The next issue I ran into was that while the space saver bolted onto the front with no problem, the rear proved to have interference with the brake drum. So much so that the stud did not even enter the wheel, about an inch in fact.

Perusing the web produced many spacers but mostly for Jeeps which asso has a 5 on 5 bolt pattern but a 71 mm hub center while GM had a 77mm hub. Did I mention that GM wheels/axles are hub centric ?

Hub centric means the wheel is supposed be located by the axle and just use the nuts to fasten them on. The GM spacers I found were either inexpensive and lacked hub centricity or expensive and had it.

The Fix

After looking I found a set that was hub centric on the axle but used the studs to locate the wheel. Since the cantilever forces are on the bub, I could live with that. They were also 1.25" thick (most are 1.5") but sold through eBay stores as a pair. Just be sure they a 5x5/5x5 and for a Caprice or C-10 and not a Jeep or Chrysler and come with lug nuts because now you need 10 for each wheel (and all need to be acorn style. If you have mag wheels with conical lug nuts you will need five more acorns.

So in the front, the spacer is not needed but is in the rear. It is not pretty but it works. Wheel studs are just barely long enough.

Can even put the skirt on afterwards.

Gotchas

Now there are a few elements you need to be aware of:
1) The Caddy space saver T145/80D16 has an adequate load rating (105) but is about 4" smaller diameter than the tire it is replacing (ok in front but will have one side of the diff turning faster than the other in the rear).
2) The rear of a typical Vixen is heavier than the front (mine was measured at 3000 lbs on the front, 3300 lbs on the rear).
3) The spare you are going to find in a junkyard may be from 10-20 years old. New replacements are hard to find.

Put these together and it is really better to change two tires for a rear flat than to use the adapter.

Even when new, most temporary spares have an "M" ( 81 MPH max) speed rating. You really do not want to go fast with one.

Final note, the temporary spares I have seen are marked for a 60 psi inflation. Make sure any TS is inflated properly before use.

A chart of temporary tire sizes is below: Note: stock 235x75x15 tire is 28.9" diameter
   T145/80D16 Service 105M Diameter 25.1408 (Caddy)
   T145/90D16 Service 106M Diameter 26.2834
   T155/90D16 Service 110M Diameter 26.9926

Jacks

The problem with a bottle jack is that while there is plenty of room for the jack then the tire is up, when flat there is not. Carrying a standard bottle jack is of little use. OTOH there are other options:

1) Cadillac jacks. It have been mentioned that a ratchet jack from a 90's Cadillac Eldorado will work but are $10-$15 from a "recycling center" & need to find one.

2) Small (18"x8"x5") 2 ton trolley jacks are available and inexpensive ($25-$35 in 2012). Lift pads are very small so I carry blocks to go on top. 18 lbs.

Examples are available from Harbor Freight and through Amazon

One has a carrying case, the other does not.

A small trolley jack can lift 8" which if lifting on suspension to change tire is plenty.

A base for the rollers (24x6x1/2" plywood or diamond plate) would be handy


Compact Jack, Diamond plate base, and bag.

"Compact aluminum racing jacks" (1.5 ton) are both larger (23x10) and heavier (27 lbs).

Note: these are very small units and have small bases while the Vixen is large. Be sure to "chock and lock" before using and place a jack stand appropriately before removing the tire.

Contents copyright(c) 2012 by Padgett Note: presented as information only for what has worked for me, proceed at your own risk. Notary Sojack.