Any problems using identical brakes front and rear?

[Guest JAMIE T]

Say for instance somebody had 13" rotors front and rear, and 4 piston calipers with 1.75" pucks front and rear as well. Could you just use a proportioning valve to adjust brake bias and get good results? This would be on a car with more rear weight bias if that matters.

[Modern Motorsports Ltd]

Say for instance somebody had 13" rotors front and rear, and 4 piston calipers with 1.75" pucks front and rear as well. Could you just use a proportioning valve to adjust brake bias and get good results? This would be on a car with more rear weight bias if that matters.

 

No! Not in a safe functional manner becoming of an upgrade or even OE replacement! Bias valves are for fine tuning ONLY, not gross adjustment. Their are many factors for balancing a brake system for appropriate function, all excluding bias valve. Some have done what you suggest and learned their lesson.

[blueovalz]

I'm one that used this set-up fairly successfully (on a race car) with some added notes though. In my situation, the rear tires were 2" wider than the front, and I had more weight in the back as well. The proportioning valve finally balanced out by adjusting it 90% toward reducing rear pressure, but it all did finally come together. Once I put the car into street trim, I found I needed to go with a smaller piston on the rear calipers (kept the same rotor), and then later (thought not necessary) larger rotors in the front. I attribute these changes to some suspension changes, added weight to the front, and a change in tire and wheel sizes.

[denny411]

How would it work if one wanted to use the stock front calipers on the rear[w/ solid rotors], and installed the four piston/vented rotor upgrade to the front?

Would an adjustable proportioning valve be able to compensate for the difference, or would they still be too close in size?

[j260z]

i've heard that the front brakes on cars do close to 70% of the braking due to not only the weight bias but also due to the weight transfer that occurs when braking. i would think that having rear brakes anywhere near the same size as the fronts would only be a detriment in terms of weight and adjustability.

[Guest JAMIE T]

Actually, That is what I thought as well. I was just offered four identical calipers, and was just checking before I bought them. Thanks.

[Tim240z]

You could always run larger ID brake lines to the rear......

 

Tim

[blueovalz]

[Tim240z]

Decreases the amount of pressure to the rear...

[katman]

Decreases the amount of pressure to the rear...

 

Nope.

[blueovalz]

Well, I was going to say the same thing but was wondering what I was missing or miss-read. All things being equal between the front brakes and the rear brakes, the caliper piston (bore) diameter differences will be the sole determinate of the pressure differential applied to the pads between the front and the rear brakes. Brake line size or length has no impact upon the pressure applied to the pads (unless they are kinked or broken). Then you start modifying this by changing rotor size (increasing or decreasing the leverage) or adding a proportioning valve (limiting max pressue to the rear). I don't even want to get into heat dissapation or pad compound, venting, etc.

[Guest iskone]

If the rotors are the same diamater but the rears are not as thick will this still be a problem?

What is are the key factors in balancing front and rear brakes?

[blueovalz]

I'm no expert at this, but what I consider key factors in chosing and matching parts between front and rear are diameter of rotor and piston cross section area. Then I go more deeply into the combinations and look at pad size, tire staggering, and weight distribution. If you were to use the same sized calipers (piston size), then I'd suggest a much larger rotor up front than in back. Or if using the same size rotor, a smaller caliper (piston) in back than in front. IMHO, thickness of the rotor on a street car is of much less importance than on a race car. This basically boils down to heat dissipation problems, which I've rarely encountered in street use.

[Guest iskone]

Thanks, I am looking at buying my parts off Juan and I was planning on using 12.19" x 1.25" w/ 1.75" calipers up front and 12.19" x .810" w/ 1.38" calipers in the back.

 

I called Presision Brakes and they said it would be fine.

[74_5.0L_Z]

I have Mike Gibson's(member name scca) Stage II brakes on the front:

 

11.75" x 0.081 Coleman machine vented rotors

Outlaw 2800 series 4 piston calipers (1.75" pistons)

Hawk HB237 HP-plus pads

 

On the rear, I have

1985 modified maxima rotors (10.75" x 0.81)

Outlaw 2800 series 4 piston calipers (1.38" pistons)

Hawk HB237 HP-plus pads

 

I also have a cockpit mounted brake proportioning valve (wilwood)

 

The proportioning valve is in the line to the rear of the car and is set at near full reduction in pressure(50% I believe). I have the same size tire at all four corners(245/45/16), 51% of the weight on the rear, and the brake balance is perfect.

 

I think that 1.38" pistons will be perfect if you are set up similar to me.

[Guest iskone]

I plan to run 245's all the way around, I could buy 1.25" calipers do you think that would be a better choice?

[ZR8ED]

Since this topic has popped up about same size brake systems. I read an interesting comment.

 

Quote:

How would it work if one wanted to use the stock front calipers on the rearwith stock solid rotors?

 

That was an interesting statement. I have not looked at my suspension in a long time, but could you modify or mount a front strut on the rear of the car, thus gaining the ability to run the front brake system on the back? It can't be that easy or someone would have already done it right?

 

The more I think about it, it couldn't work could it?

 

Anyways it would be cool if you could. Especially if you upgraded your front brake system to larger rotors and calipers.. you could just use your stock front stuff on the back. hmmm just make some sort of adapter to use the fronts on the back?

 

Stop me I think I'm talking crazy...I'm certainly no engineer, but anything is possible right?

[Guest Steve-Z]

About the question of using stock 240Z front calipers on the rear with larger front rotors and calipers, I remember seeing that setup on Frank Leary's 280z SCCA race car back in 1981. Frnak was the SCCA national champion in 1976 or 1977. He was using an aluminum rear brake caliper bracket to use the stock calipers with a solid rotor. I don't remember what front brake setup he used.

 

hope this helps Steve