Spare Tire Carrier bushing dimenions
 

Hi all,

I'm posting this as a reference in case it is useful to anyone.

I removed the upper plastic bushing from the lower hinge for a 2nd generation external spare tire carrier. I used this one as figured it would be less worn than the lower one. It is GM pn 12546658. link: (https://nemigaparts.com/cat_spares/e...t/07/ts07-515/)

The hole into which the bearing is inserted has an ID of about 0.764" +/- 0.005"
The OD of the pin is 0.619"+/-0.001"

These are the dimensions of the bushing as measured in inches, mm and the approximate nominal fractions of an inch.

https://cimg5.ibsrv.net/gimg/blazerf...b98be4545e.jpg

ID: 0.632"+/-0.004" (16.05 mm+/-0.10 mm) ~5/8"
OD: 0.775"+/-0.001" (19.69 mm+/-0.03 mm) ~3/4"
L: 0.569:+/-0.003" (14.45 mm+/-0.08 mm) ~ 9/16"
FD: 1.245"+/-0.004" (31.62 mm+/-0.10 mm) ~1 1/4"
FT: 0.057"+/-0.002" (1.45 mm+/-0.05 mm) ~1/16

Edit: When both bushings are in place, their bottoms meet just about touching in the hole for the hinge pin with a gap much smaller than 1 mm.

I wander how an 3D printed ABS bushing would hold up...

Probably not well as a 3D print is not known for it's strength lol

hmmm...

Very cool, thank you!

The bushing itself is plastic but a very hard and non-flexible one. I don't know much about the structural properties of 3D-printed items. The lateral loads on the bushing are pretty large. What ever it is made out of would have to be non-deformable.

The factory bushing is an injection molded piece that is likely fiber reinforced. I doubt that it would be nylon, rather a different more rigid thermoplastic, but nylon could be used. There are 3D printers that can print nylon, however nylon requires hot end temperatures over 240C which knocks out any printer that has a PTFE liner in the heat break or bowden tube that extends through the heat break to the back side of the nozzle. PTFE will start to swell at these temperatures leading to inconsistent extrusion. Having said that, a printed component will not be as strong as an injection molded part of the same dimensions. There are just too many opportunities for voids between the extrusion passes in a printed part. I'm not saying that it wouldn't work, but Nylon, ABS, or even PETG would be a step down in terms of service life from the factory piece. I wouldn't consider PLA for any kind of automotive or outdoor use as its service temperatures are just too low.

Given the dimensions Christine posted above, it should be relatively easy and not too expensive to get these machined out of brass or bronze at the shop of your choosing. I doubt that it is very important to align bore the frame as the whole thing isn't all that rigid to begin with and flex during use will twist/pull at the mount points anyway. Having things aligned perfectly would improve the life expectancy of the bushings, but moving to brass/bronze is a significant jump in wear resistance & load handling over plastics.

*EDIT* - A quick search on Amazon came up with these choices:

1. 5/8" ID // 3/4" OD // 5/8" L flange bushing
   5/8" ID // 3/4" OD // 5/8" L flange bushing
2. 5/8" ID // 3/4" OD // 1" L flange bushing
   5/8" ID // 3/4" OD // 1" L flange bushing

Both have 1/8" flange width which would likely need to be reduced to meet the 1/16" dimension from Christine's measurements and the 1" long bearing would need to be cut down in overall length as well. Both of these are PTFE impregnated sintered powdered metal pieces so they aren't going to be as strong as solid brass/bronze, but they're certainly cheap enough. If the 5/8" long ones were to be used and simply sanded down to fit properly, this could be a DIY fix.

Wow, that is great info on the 3D printing process and the likely materials used in the stock bushings. :icon_worthy:

As for modifying the off-the-shelf bushings; that is what I was thinking too. Having not installed my tire carrier yet, this would be easy to try before installation.

Thanks!

One thing worth noting, if the dimensions are as measured, a cheap bushing that is stated to have a 3/4" OD will likely be that or slightly under. Given that you measured 0.775" OD, this may result in a loose fit. If this is the case, a light coating of JB weld on the OD of the bushing with a higher amount under the flange may tighten things up enough to make it work.

Man, swartllk dropping some knowledge!

Thanks for all the info... This is something I've been contemplating fixing as well.

As always, another very helpful thread on BF.