Brake Caliper ?

[RACR_73s]

I am looking at a set of front brake calipers but need to educate myself first, so I came here for my "education." They are a set of Wilwood forged narrow Dynalights and one of them has a 1.0 piston and the other is a 2.0. According to the guy one is marked LF and one RF (I don't know which is marked what). My current rear brake setup has US Brake f88i calipers which are a staggered piston caliper with 1.88 & 1.62 pistons and I don't know which compound the pads are. Last year I had a Grt LF caliper and a Rayburn RF caliper and that is about all I can tell you about them other than the LF must have been braking much harder as it wore the rotor thin and the pads to nothing. It seemed like I could never tighten up entry even with all front brake (could this be a reason why?).

1) Which one of the Wilwood goes where and why?

2) Which brake pads should I use...Front? Rear?

3) Should I use these two different sets together?

4) How do different size pistons affect braking?

Any other info that might be helpful is also appreciated. Budget is a big consideration in the decision, but not the only. Running a limited class and payout is not that good so buying all new stuff is not an option.

~Thanks~

[Matt49]

A larger piston provides more pressure to the pad than a smaller piston provided the same amount of pressure pushing the piston. When you are applying the brake pedal, at any given point, there is an equal amount of pressure throughout the entire system. Pressure is measured in PSI which is directly related to area (square inches) so a larger piston size will get more pressure to the pad. (Note: we actually have too independent "systems" past the pedal on most late models but adjusting the front to back bias obviously doesn't change the pressure delivered to LF versus RF before the pistons.) You may want to measure your Forged Narrow Dynalites again. They only come in 3 piston sizes: 1.12, 1.38, and 1.75.
Different piston sizes on the front is not uncommon but the split you have is pretty extreme in my opinion. A common setup with Wilwoods is 1.75" on the LF and 1.38" on the RF.
The idea is to put the bigger pistons on the LF and it is supposed to help the car turn on entry (and it does).
On Having different piston sizes within the same caliper is supposed to be to prevent uneven pad wear and you would put the smaller piston closer to the leading edge of the brake pad. So if the caliper is behind the hub, the smaller piston is on the bottom. In my opinion, this concept is not necessary under most braking conditions. Maybe it come more into play on pavement but I haven't seen a lot of strange uneven pad wear issues on dirt cars that warrant this intra-caliper piston split.
Everybody has their own opinions on brakes but mine are these:
Use the same brand and style of calipers all the way around so you know they all physically react the same.
Use the smallest caliper that will effectively and safely slow the car.
A small amount of piston split in front is okay, too much is correcting for something. If you are relying on brakes to turn your car, your car is too tight.
USE BRAKE PRESSURE GAUGES to make sure you know where 50/50 is on your front to back bias.

[RACR_73s]

Matt, thanks for the reply. I find it very informative and helps explain why my car is doing what it is. My car has a 1.75 LF caliper and a 1" RF, I was never happy with the car on dry slick and was constantly putting all front brake in with no improvement as far as trying to keep the car under me.

Beside checking the piston sizes today I looked at the pads and these are the ones in the RF - BP-20 Smart Pad, Dynapro/NDL and I could not find a number on the LF pads anywhere. The rears have NRS 30YL's on them.

I have the original f88i LR caliper for this set which broke the exterior crossover line, and to band aid it, I moved the LF to the LR and put a different spindle on the LF in 2012 so I could use the bigger 5.25 bolt pattern caliper. Something later in 2012 took out the RF caliper and I robbed the RF caliper off my Rayburn in desperation. I used this all of 2013.

What brought this problem to my attention was the extreme wear on the LF rotor and pads.

[Sprint76]

The first thing you should do is get a matching set of pads. If you can't guarantee the pads are the same, throw them out and buy a complete matching set so you know where you're starting at. I run the smaller 1" pistons on the RF and don't have a problem tightening up the car for the slick, although we don't get many truly slick tracks where I run. Even buying a used set off of someone that matches would be fine if you have to.

Think of the smaller RF pistons as an intermediate step to a full RF shutoff.

You will get a ton of different opinions on compound, but we run Performance Friction 81s without any issue. Have had problems with Wilwood E's and B's in the past.

The staggered pistons within a caliper will help with even pad wear. I have seen as much as .125" toe on the pads caused by never flipping them in a caliper that doesn't have staggered pistons. I run standard pistons, because I pull my pads out every few weeks anyway, and when I reassemble, just install them the opposite of the direction I took them out.