Soloontario

Interested in what you guys run and if you have any differences between compounds for your front and rear pads.

My experience is that with a square set up i.e sig larger tires than stock up front, that the front brakes can handle a lot more braking force than the rears. I know the rear pads are smaller but I was wondering if some guys go to sig lower coefficient of friction rear pad out back to prevent triggering antilocks and allowing the fronts to do the extra work they are capable of.

BEZ06

Yes, many of us run different pads front and rear - not necessarily to get a different coefficient of friction, but mainly to have pads that will be operating in their proper temperature range. I run lower temp pads in the rears because it just doesn't get heated up as much as the fronts.

I looked in your profile and it looks like you have a C5. I don't know much about the C5, but I'm pretty sure it has a similar EBCM to the C6.

In the C6 the EBCM and BPMV have what's called DRP (Dynamic Rear Proportioning) on the earlier C6's, and in about 2009 they changed from a Delphi ABS to a Bosch system and started calling it EBD (Electronic Brake Distribution). In either case, the ABS system's EBCM will take care of front/rear bias for you and you will get the proper braking force regardless of the pads you're running.

If the fronts are doing more work than the rears, they will heat up more.

So......different pad compounds front and rear is usually so you have pads that will be operating in their designed heat range.

I usually run either Hawks or Carbotechs - Hawk DTC-70 front/DTC-60 rear; or Carbotech XP12 front/XP10 rear.

Bob

Soloontario

How does the EBCM modulate the force to the rear? Does it start to activate the antilocks? When a wheel does lock does the EBCM change the brake balance? If so then doesn't this become an issue with sometimes the front(s) locking and other time(s) the rear? Does it remember what happened on the previous brake application?

Sorry, I am clueless on how this works.

Also I believe the standard brake bias is set to the rear. If the rear is less likely to lock wouldn't it be helpful to have a predictable brake balance and never trigger the rear antilocks rather than having the EBCM change it constantly?

BTW I have run XP10s up front and XP 8s out back but have not been overly happy with this level of balance. OTOH maybe I'm not feeling the car right.

BEZ06

You're asking technical info that I can't answer - maybe some of the brake experts can, but most of what the EBCM does is PFM (Pure Friggin' Magic), and only the Delphi/Bosch/or Corvette brake design group engineers know what is really programmed into the thing!! And different years are probably a little different.

You talk about brakes "locking", but the ABS does not allow any locking to occur - unless it's not working properly, and you can read a couple recent threads where it allowed the driver to lock the wheels, or perhaps the ABS malfunctioned and locked the wheels.

You say standard bias is set to the rear, but I don't know the algorithm the EBCM uses to adjust the front/rear bias. The rear bias is dynamic - i.e., it's going to change to keep the rears from locking up. The fronts are doing a higher percentage of the braking.

I think you're worrying about a nonissue. The EBCM will generally adjust the front/rear bias automatically for you so you don't have to worry about the problem you seem to be concerned about.

Considering that the front brakes do more of the braking and heat up more than the rears, you can probably run a less aggressive pad in the rear and not over-temp it.

Good luck gaining a deeper understanding of the EBCM software, but it's PFM!!!

Bob

Soloontario

I believe that the base car setup is designed to do quite a bit of braking at the rear (obviously not as much as the front but enough that on dry pavement that the rears will lock up first which means the rear antilock pumps work first). My experience with this type of balance when designed well is that in slippery or wet conditions where there is less wgt transfer and more wgt stays on the rear axle, that the fronts lock first (or should I say the front antilock pumps work first).

You can check this out pretty easily on the street by pulling antilock fuses and try braking hard in different conditions.

Obviously everything changes with sticky tires and especially sticky, larger that stock, front tires.

I used to run a Camaro in a lot time attack events in the Mobil 1 Time-attack series here in Canada. Too much static rear brake bias was a huge issue. The best way to deal with it was to use race pads up front , street pads out back and put in a brake proportioning valve to decrease the rear brakes even more. This actually worked very well and I had to dial out even more rear brake at the track than on the street. OTOH in really cold wet conditions, street tires and even with just street pads on the front, the fronts would lock up too soon relative to the rears meaning I didn't have enough rear bias.

Wish I knew how "dynamic" brake biasing works differently than a standard 4 channel antilock system.

BEZ06

Read this StopTech technical bulletin - scroll down to the paragraph about "Electronic Proportioning: No Tampering Allowed":

http://www.stoptech.com/technical-su...tioning-valves


Here's another bulletin with more info on bias:

http://www.stoptech.com/technical-su...alance-matters


Here's a forum thread with info about bias. Many forum members recommend the DRM manually adjustable bias Proportioning valve. Also, you can read that several posts talk about trying to dial in the maximum rear bias you can get:

http://forums.corvetteforum.com/c6-z...rake-bias.html


Bob

Soloontario

Thanks for the links. Make for interesting reasoning.

First off, obviously I can't affect the pre programmed Dynamic Brake Balance and as Stoptech mentions, messing with this by using an external proportioning valve is likely not a great idea. OTOH the car is sig different from stock, and as mentioned in the second link, more wgt is on the front axles i.e more than the computer expects and the computuer is more likely to trigger the rear antilocks, which means the dynamic balance computer has to be tricked to some extent. I really think the best situation is to not have the antilocks trigger on the race track ever.

My guess is I need to go to a bigger front to rear pad stagger than I have been using. Interesting that a couple of guys who regularly beat me have much weaker rear pads than XP 8s but front pads that are the equals of XP 10s. I have ridden with them and they can be sig harder on the brakes without triggering anything.

JimbeauZ06

Many of us run less pad in the back. For example, DTC 70 front/DTC 60 rear, or DTC 60 front/HT 10 rear. One reason is to save a couple of bucks, but primarily because the back pads don't work as hard and you simply don't need/want that much bite in the rear. As you go faster into the braking zone, hard braking shifts more and more of the weight to the front increasing the likelihood of ABS engagement due to lack of weight/traction and smaller contact patch with the rear tires, and since anytime the ABS is active you're not slowing as quickly as you could this is not optimal. Less aggressive pads in the rear balance this out and save a couple bucks in the process.

Soloontario

I think my square setup means I need an even bigger stagger. I used XP10s up front and XP 8 in the rear but will likely back off even more out back.