removing the front brake backing plates
 

I want to remove the front brake backing plates that prevent debris from getting to the discs and pads. I already removed the caliper and dust cap (more like a frigging bullet proof chastity belt!).

My first question is: What is the minimum list of additional parts that I have to remove from the stub axle to remove the backing plate? This is the list and picture from Bentley:
1. Bearing lock nut
2. Thrust washer
3. Outer bearing
4. Inner race, outer bearing
5. Bearing hub
6. Inner race, inner bearing
7. Inner bearing
8. Grease seal

My second question is: How difficult a task will removing and reinstalling these parts be? Do I need any special tools?

This is for a 1985 3.2 Carrera if it matters.

http://forums.pelicanparts.com/uploa...1237147333.jpg


Bill Verburg agreed that "...requires taking the bearings off..." and posted the picture below. But I can't tell if this means all eight of the above parts or not.

http://forums.pelicanparts.com/uploa...1237147397.jpg

from: http://forums.pelicanparts.com/porsche-911-technical-forum/212323-do-i-need-my-brake-backing-plates.html?highlight=protective+plate

Pretty much have to remove all of it. Having said that, once you get # 1 & 2 off, just pull on the hub. The bearings can come out easily and should be cleaned, inspected and repacked. Once the hub and rotor are off there are 3 bolts to remove and the plate comes off. Once you put everything back together and have the wheel bearing at your desired 'snugness', drive it for a day or two and then re-check the washer tightness to make sure the bearing lock nut doesn't need to be snugged up another 1/4 turn.
Hardest part of the job is getting the dust cap off the end of the hub.

once 1 & 2 are off the whole hub just slides off the axle
http://forums.pelicanparts.com/uploa...1237154652.jpg

Tony G.,

Thanks for the response, the job sounds pretty doable relative to my skills.

Why does the bearing lock nut need to be snugged another 1/4 turn after driving for a couple of days? Does the lock nut lose the 11 ft-lb (Bentley) torque after driving?

Thanks Bill, that sounds easy.

So why do some of the threads here make the job sound more complicated? An example is this one:

http://forums.pelicanparts.com/porsche-911-technical-forum/278252-front-wheel-bearings.html?highlight=bearings

that says stuff like:

1. replace wheel seals since I'm likely to destroy them when I removed them
2. for re-assembly need to freeze the stub axle and heat the bearing hub
3. replace bearing races and freeze them
4. Drive the cold races into the warm hub (Use special bearing race driving tool)

Do these things only apply to pre Carrera 3.2s?

If you are r&ring the bearings from the hubs it's a much more complicated job.

As long as you are careful the seals will be ok and can be reused.

There are two actions with the lock nut for the bearing. It threads on the axle and then there is an allen wrench you need to lock it in place. The threaded nut is spun on, not wrench is used and no ft/lb of torque. The typical method is to snug it up and use a screw driver to move the washer both up and down or side to side so that it has medium resistance. Then you tighten the allen head bolt to hold the position. (maybe that's where the 11 ft/lbs comes in?) When you clean and repack the bearing, it is always a good idea, at least in my mind, to go back and check the washer for play. It is possible that just handling the parts and doing the R&R is enough to make it not seat exactly at the correct tension.

Bill, Thanks again!

Tony,

Thanks for the explanation. Now I understand why the 11 ft/lb (for the M8 allen head screw) does not directly set the amount of snugness that bearing lock nut gives in the bearing assembly stack.

Hi Art,
I have been following your posts. I started slipping down the DE slope a few years ago. While you have the front hubs and rotors off, now would be a great time to unbolt the rotor from the hub and install the hub deflector guards. This is a thin piece of metal that fills in the air gaps in the hub and makes the air flow through the vents of the rotor keeping it cooler. You should also buy a set of 993 air deflectors to increase the airflow. Sort of like the Visa commercial, $30 for the air deflectors, $70 for the hub deflectors, the satisfaction of not having brakes that overheat, priceless. Good luck,
Joe

Joe,

Thanks for the suggestions! I have the 993 deflectors ready to install. And I'm tempted to do the hub deflectors while I'm in there. But my DE budget is already seriously deficient, so the deflectors will probably have to wait until next season.

Do you go to the PCA DEs at NHMS?

Hi Art,
I hear you on the budget thing. It piles on pretty quick. Too many while you are in there's. I have not been to any PCA DE's at NHMS but I have been crew on my nephew's bike racing there though. We seem to gravitate toward Lime Rock and Watkins Glen. Two very different tracks but hard to pick one I like better. Unbelievable good times. Good luck and hope to see you out there some day.
Joe

Thanks Joe! I've heard from people that have driven Lime Rock, Watkins Glen, and NHMS that NHMS is their least favorite. It is relatively close to me though so it is the only place that I've gone so far. I DO want to get out to Lime Rock and Watkins Glen eventually though.

Good luck to you too.

I did the r&r and got the backing plates out. The job went exactly as you guys said and was easier than I expected. But now I have a follow-up question. Specifically, if the lock nut's original position gave the right bearing stack gap, shouldn't using that position after the reassembly NOT require the step of driving for two days then tightening 1/4 turn?

Before I did the r&r I checked the amount of force necessary to move the thrust washer around. And I was surprised at how difficult it was; much more force than the light force that Bentley recommends. But rocking the wheel about the longitudinal axis of the car felt like it had the desired tiny bit of play that I've read about. Plus the car only has 40k miles on it and probably only 1k of that put any serious lateral acceleration on the car.

So after I replaced the bearing parts, I set the lock nuts to the exact same positions that they were in originally. And on both wheels, the force to move the thrust washers and the free plays about the longitudinal axis felt the same as original.