So if you don't know already, I had to tow my FB home from DGRR this year. I had my right front wheel bearing (which I replaced not 2 years/5k miles ago) disintegrate and seize to my spindle. I replaced inner and outer wheel bearings, along with races, brake rotor, and inner dust seal about 2 years ago (~5k miles). On the drive down my nut somehow loosened, so I tightened it along the highway and everything was fine (checked it again during the Friday morning drive at DGRR that included the Skyway and the Dragon. still tight). What I'm wondering is this:

What would increase the life of a wheel bearing, and what would cause such a catastrophic failure? I haven't had a chance to disassemble everything (trying to source new parts before I dig into it), but I do know that the brake rotor is stuck currently. I am running:

S2 front spindles (small bearing)
15x7 Enkei 92's with a +7 offset
Potenza RE11 tires (180 treadwear rating).

Could it be the high-offset wheels? Small bearings not being as robust?

Thanks

-Jim

 

I would imagine a high offset wheel would cause a good bit of extra stress, being as a lot of the load is off the center line. And also like you said, the smaller bearing probably can't cope so well.

 

I would bet it was a culmination of events thats caused it. Running loose for awhile
could have overheated or warped some surfaces and or toasted some bearings.
Then tightening it down too tight on the side of the road or just tightening it to spec
may have then aggrevated the issue. Running 7 inch wide 15 inch wheels definitely
may have stressed the smaller wheel bearings. Then taking it on the NC mountain
roads which will maximize any stress already there and I think you had a recipe for
failure.

A tear down may reveal something but its hard to say. If the rotor is seized then
you can pretty much count on things having grenaded in there and making a mess.
So it may be local to that wheel but I would replace all the same parts on the
otherside as well. It could be just on the verge of doing the same thing. I always
do bearings and brakes on the whole axle for that reason. You can get away with
just doing fronts or just rears for whatever reasons but never fix just one side of the
axle because the other has seen the same usage and probably will fail shortly as well.

 

The rotor isn't seized per-se, it is stuck on the spindle though. The inner bearing hits the remnants of the outer bearing, keeping the rotor on. I have a set of big bearing front spindles lined up coming out of Ohio, so I'll tear everything down and post pictures once I get the time and inclination.

 

is everything the same from the small bearing to big bearing spindles except the bearing size? like the rotors, calipers etc?

 

I believe they are. You didn't get bigger/thicker rotors and different calipers unless you bumped to the -SE.

 

sweet, then i might swap the spindles from my other 85 and my 83. the 83 is turbo 12a in progress i have too many un running 7's haha

 

Another upside (since you're building a turbo 12a and need all the brakes you can get) with the big bearing front end you can get the bolt-in Re-Speed BBK (provided you can source a set of TII calipers and rotors, and have a spare set of 15" 5x114.3 wheels with the proper offset laying around)

 

When you tightened the nut, did you also repack the bearings?

Non-sealed bearings are supposed to last a while, provided they're repacked once in a while.

 

I did not re-pack the bearings, as I was along I-75 in a traffic jamb.

 

Another thing I'm curious about:

What's the stock offset for the FB '+' wheels?

 

Which is what I am doing. Have everything ready to go in but the 4 lug FC hubs. TII brakes on an FB will be crazy (in a good way).

I want to say offset for the 13'' 4 spoke wheels is +18. May have been 14, I have a lot of numbers running around in my head lately.

 

I got about 20 years total run time out of my first set of bearings (they were 10 years old when Igot them). Still on the second. I repack them everytime I change brake pads.

Setting pre-load accurately takes some doing - - it's way tighter than most people expect it to be.

 

I had a right front bearing issue also, although I made it home okay. I found that the inner grease seal (dust seal?) had fallen apart.

It can also be difficult to set the proper preload on the bearing during installation.

Use Lucas grease. And, if you have a grease gun, then I highly recommend the bearing packer that they sell at autozone. Works great.

 

+1, too loose will kill the bearings very quickly. i've got that t shirt!

 

What exactly is the pre-load recommendation/operation for the FB? I'm about to have to do mine. I have a manual, but it's not within reach and I am curious. Do you guys set it tighter than specified, or go by Mazda standards?

 

I go by FSM standards, which are plenty tight enough. I don't have FB numbers ( as I don't have an FB) but SA preload is 0.99-1.43 lbs force at the lug diameter required to begin rotation.

The book shows using a spring scale (like a fish scale) horizontally, but I use 1-lb dive weights vertically suspended by a wire from a lug bolt.

If you don't have either, you can also use the alternate method of tightening the hub nut till it binds completely, then back off 60 degrees (1/6 turn).

 

This is how it is outlined in the Haynes manual, however do NOT tighten it until it binds, but until it begins to bind, then back off a touch. When the rotor needs more then gentle persuasion to rotate it is starting to bind. If you tighten it to the point that it will not turn without some effort then it is way too tight. Ask me and my two junked spindles how we know. Basically there should be no side to side movement but it should rotate smoothly and freely. Drive it about 100miles and pull the wheels and check them.