can anyone help me out with finding the appropriate material to shim my brake pads?

 

Not exactally sure what you mean, but you can use old backing plates of spent pads.

 

Yeah, that is what I am looking for, so how do you glue or stick the old backing plate?

(tired mind/body == bad info and questions)

 

you don't glue them on.. just put a little grease on the back of the pads (to help with squeeking) and stick em on.. they aren't required ya know.. if you do need em i'd just run to a local junkyard and take em off of some pads there..

 

Greg,
I've never personaly done it, but I've seen it done. I'm not sure you'd really need glue or anything. I mean, it's not like they're going anywhere once it's in the caliper all bolted down. Get a wasted set of pads you can scrape/grind the excess material off. I actually even heard a few CRX guys this weekend at the IRDC race talking about it.

I guess I've never thought about it before, but is the purpose of adding a shim to simply set the pedal height with a 1/2 used set of pads?

 

It sounds to me that there is some confusion as to the terms being used.

An OE shim is the thin (0.0.25"-0.040") metal piece that is typically clipped onto the back of a brake pad. The backing plate is the actual metal (on H/A vehicles, 0.190" to 0.240", depending on the model) piece to which the brake pad material is attached. The brake friction compound and the metal backing plate, together, make up the completel brake pad.

Shims serve the purpose of noise reducing, and do not offer any increase in brake pad performance (other than noise reduction). On a race/track pad, it isnot necessary to use a shim, as they will make noise regardless.

-Andie

 

Nope. It's to maintain the effective pressure and operation of the piston. (I hope that sounds right)

The further the piston needs to extend in order to engage the pads, the greater the chance the piston will get sloppy and cause uneven pressure leading to uneven pad wear...

Greg ~ who's not that good at writing

Actually it may help maintian pedal height? or not?



[Modified by bulldog_RS20, 1:13 AM 10/8/2002]

 

I disagree with your assessment of the purpose of a shim, if we are talking about the same thing. If we are, then please explain how a 0.025" thick piece of metal will make a significant difference in the pedal travel, especially since the total pad thickness on an average H/A vehicle is 0.650"...with a backing plate thickness of 0.200", yielding a 0.450" average pad material thickness. If you do 8-10 hard braking manouveres from 60mph, you will wear away 0.025" of pad material, which is the typical shim thickness. If what you are saying makes sense, then would you be taking your pads out and reshimming them after ever stint of aggressive braking?

-Andie

 

No we are not talking about the same thing. John and I talked to some fellow racers this weekend who use old backing plates stacked behind their pads when the pad material gets down to 50% or so. They do this to reduce the chance of uneven pad wear.

We prolly got off-topic a bit but I wanted to correct johns statement / question...

 

uh, what andie and bojangs are talking about are the thin pieces of metal to suppress noise. what greg umbay wants to know is how to shim the brake pad in order to reduce the piston extension, (not really travel, that would be the same regardless), appreciably for perhaps better pedal feel. what john suggested is use old backing plates to accomplish this. although i think this is way too thick as is, prolly needs to be milled down.



[Modified by Tyson, 5:11 PM 10/7/2002]

 

Ah...I understand what you are talking about.

For all intensive purposes, with a race caliper system, it is NOT necessary to "shim" your brake pads as they wear. Let me explain. While the mechanics of what you are saying makes sense (it's pure mechanics after all), multiple piston, differentially bored race calipers tend to ensure even pad wear. Further, once you get a pad down to 50% of material, the wear rates accelerate geometrically, while means you're better off installing a new set of pads...I typically recommend never starting a race with less than 50% of pad material anyhow. The improvement in pedal feel from shimming a pad as it wears is not significant...and it is really more of an academic procedure, IMO.

Further, a piston does not fully retract, even if you pads are worn down 90%. Thus, all you really need to do is bleed your brakes to maintain consistency in pedal feel. If the pistons DID fully retract, even after the pads are worn, and thus significantly increase the piston travel upon brake pedal application (and thus significantly change the pedal feel/stroke), then we wouldn't ever have the discussion of "how do I push back the pistons" when changing pads.

JMO from experience... -Andie

 

With all due respect Andie, we're talking about IT cars with factory calipers.
While I'm still not 100% sure why these guys were doing it, but Greg's point about pad wear does seem to make some sense. It's either that, or just a "feel" thing.

 

Then I would recommend just bleeding your brakes. If you place an old backing plate behind the factory pad, which in MOST cases simply won't work, since most factory fitment inner pads have lugs protruding on the backside, you risk vibration and uneven pressure transfer to the pad. This is especially true for OE fitment calipers, due to the nature of how they work: the inner pad is PUSHED, and the outer pad is PULLED, into the rotor.

I've heard of this being done, and I have customers who have tried this...and none of them do it anymore, because it is purely academic, IMO, and does not in any way improve braking performance.

-Andie

 

I guess I am curious about what is trying to be accomplished by shimming the brake pad.

If you are concerned with the piston getting cocked in the caliper bore, I would not worry about this. Brake calipers are designed so that with the min pad thickness there is enough piston engagement into the bore so the piston will not ****.

If you are concerned with pedal feel, check your rear brakes if you have drums and adjust these slightly. On my 85 CRX if the shoes are not adjusted closely to the drums, I lose pedal feel.

I hope this helps

 

For some reason, on some Honda's and Integra's when the race pad wears you get a very "long" brake pedal. This happens on my ITA car. Nothing works to get the pedal back to normal except to put on new pads and rotors. I've tried new MC's calipers, bleeding, new caliper mounting pins .... everything. The shims supposedly help extend the usable life of the expensive race pads and reduce some of the excessive pedal travel. I have not been able to figure out the physics of why this happens nor why it only effects some cars.

 

Single sided piston sliding calipers yield uneven wear, especially with a single piston caliper. The pad "teeter-totters" on the single piston, resulting in faster wear on the leading edge of the pad, relative to the trailing edge of the pad. This is a defficiency of the caliper system itself, and not the pad material you are using; OE brake systems are not designed for racing, IOW...but that's the challenge of most amateur race series...to take an OE-spec car and drive it under race conditions.

-Andie

 

I've actually noticed this when it's worn thin. I always attributed it to more heat transfer to the caliper due to the lack of 'insulating' the pad material provides.. since there's less of it when the pad is worn down. When I feel it, I know it's time to change pads.

dale

 

So I am not the only one. That is why I posted the question.
gotta go here come the boss.
whapish back to work damn lazy software tester