brakes, backing plate, tone wheel

[eastwestboy]

The brakes on the Impreza 95 were in real bad shape. On one side only a bit of the backing plate was there, so these have to be replaced. To put the new backing plates on I have to remove the tone wheel and to remove that I think I have to remove the hub. Or maybe not? I loosened the tone wheel but it still stays, of course, behind the hub. I was not able to slide the backing plate in position that way. I once tried to remove the hub on a legacy. Unlock the soft metal in the nut opening, unscrew the axle nut, pull with a puller on the hub. I pulled so hard that I was afraid the puller arms could rip. I gave up on that. Would I have to increse the pulling force no matter what?

 

I have had already 2 rebuilt calipers installed. Both had too much play on the sliding pin. Both shops said that this is normally acceptable. I returned all of them. It’s difficult to test for the play if they are not mounted in position. There was also no Subaru dealer here around that could get brand new ones, except for Subaru of Mississauga (biggest in Canada and Headquarters) but it would have taken 2 weeks for them to get it. I orderd them in Buffalo NY and went over on the weekend to get them. Yep, Canada is always a problem for auto parts, if Canadian tire does not have it, trouble is looming. Don’t say Napa, that gives me the fit of laughing.

Thanks everybody

[Legacy777]

You're post is a little difficult to sift through.

 

When you're talking about backing plates, I'm assuming you're talking about the backing plate/piece where the brake caliper mounts to?

 

If so, why do you have to put new backing plates on?

 

To replace the backing plate, you have to remove the hub, which requires a puller, and you will need to replace the wheel bearings as well.

 

Where was the play on the calipers you had? Can you describe it a little more?

[eastwestboy]

Thanks for replying,

With the backing plate I mean the protection plate for the inner side of the rotors. It’s the diameter of the rotor and has an opening the size of the caliper. It’s right behind the rotors. They call it like that at the subaru dealer (which doesn’t mean very much). These thingies were totally rosted and a lot of material was missing. So I got new ones.

 

About the play. I mounted the calipers in position without installing the rotors/pads. Then I slided the “sliding half caliper” back and forth. This slide should be very smooth. In my cases, the sliding pin was a bit too small. Thus the sliding part not only traveled in the sliding direction but could also wiggle. This leads to uneven pad wear, I have had this before.

 

Why do I have to replace the bearings? I think they are still ok.

[nipper]

whats a tone wheel, thats new to me.

 

Basically if your going to go through all that labor, you should replace the bearing. Its likes replacing a timing belt and not replacing the water pump.

Murphies law will bite you in the but and the wheel bearing will go not long after doing all that work.

Laos since your car is a 95, it really wouldnt be a bad idea to change them anyway, as ten years ona wheel bearing is a respectable life.

 

nipper

[Legacy777]

The tone wheel is part of the ABS system. It's used to determine wheel speed and if it's slipping.

 

here's a chopped up one

http://www.surrealmirage.com/subaru/images/swap/06/DCP_3127.JPG

 

The bearings are held together by the hub and tension, etc. If you remove the tension, and between that and pulling the hub out, they tend to separate, and are not really the best to reuse.

[nipper]

ah i never knew thats what it was called. i just called it the abs signal generator aka thingy (since its not really a normally servicable part).

It used to be so much fun when i got to the name the parts in my old job.

 

 

nipper

[OB99W]

[...]It used to be so much fun when i got to the name the parts in my old job.

Maybe whoever decided to call it a tone wheel had some familiarity with old Hammond organs. See http://b3world.com/TechInfo/figure5_1.html .

[ferret]

Not just in automobiles, these have been used in all types of machinery and equipment since that were controlled by electrics and controllers.

I've seen 'tone wheels' in all types of equipment. They usually have emitters, pickups, hall effect sensors etc as a means of reading the cogged surfaces as they rotate. But the raw digital signal given out, if amplified, sounds like a musical note to our ears. As the speed changes, so does the note or put another way, it changes 'tone'.

 

Some car manufacturers used this same idea in their distrubutors for their first type of electronic ignitions. There were MANY types there from cogged wheels on the distributor shaft (yes a tone wheel), to open holes and clear lined disks some there done with optics. End of $.02 for this morning.

[OB99W]

There are two basic types of ABS wheel speed sensors. The variable-reluctance kind are just a coil of wire wrapped around a magnet, and output an analog (sine wave) signal whose frequency and amplitude (tone and volume ) change with wheel speed. The other type is magneto-resistive, includes some electronic circuitry, and outputs a digital signal that changes in frequency with wheel speed, but has a fixed amplitude.

 

Earlier ABS sensors tend to be of the variable-reluctance type (my own '99 OB has that). I don't know if Subaru has switched type in later model years. I guess we're now up to $.04 .