Toyota Truck Calipers, Ventilated Brake Rotors, MM rear Disc Brakes

[Miles]

KTM

 

What master cylinder and booster are you using?

[Nigel]

Where is the pad coefficient in your calculations?  If you want to be picky, you also need to consider pad compound.  By adjusting pad compound you can change the bias.

I said in my post that you quoted that I was assuming equal pad coefficients of friction, and I clarified later that my calculation was based on the smaller SX rear caliper. Regardless, yes you can adjust bias with different pad compounds, and you may be able to get the V6 Toyota/later SX caliper combo to work ok with the right pad combination. The challenge is finding a published friction rating for a given pad so that you're not just swapping pads at random until you find a combination that works. Many pads have a 2 letter code printed on them that provides the friction range, but you can't get that until after you bought the pads.

 

For my own personal setup, which includes AZC Wilwood fronts and my own Jag/Lincoln rear design (http://forums.hybridz.org/topic/113199-yet-another-rear-drum-to-disk-conversion-option/), I started out with some EE code pads (0.25 to 0.35) in the back that I had left over. As I suspected, based on the math, even with full rear line pressure, I couldn't get the rears to lock. I then switched to EBC Yellow Stuff GG code pads (0.45 to 0.55), which the math indicated would be a better match, and sure enough, I've had to decrease rear pressure by three turns on my adjustable prop valve to achieve a slight front bias.

 

 

This all neglects pad area, which is a big contributor to overall braking...For a given piston diameter, the larger friction surface of the pad makes for not only more drag on the rotor, but also more heat absorption area. You can't convince me, nor will the mechanics show, that a 38mm piston with a 38mm circular pad area can apply just as much friction to the rotor as a 38mm piston with a pad with double the surface area, but the same top and bottom heights, such as an elongated kidney shape. Pad size does make a difference in braking capability of a given caliper, even if the piston sizes are the same.

I guess countless physicists and hundreds of years of experimental data must all be wrong then? The force of friction is due to the coefficient of friction between two objects and the force pushing them together. That's all. Surface area is effectively irrelevant. If you place a 50 pound block on one square inch, you have 50 lbs per square inch of force. But doubling the surface area to 2 square inches does not double the weight applied. You're still applying the same 50 lbs block, but now to two square inches, so in effect you're now only applying 25 lbs per each square inch. You've doubled the area, but halved the force. That's why surface area is irrelevant.

 

Nigel

[ktm]

I said in my post that you quoted that I was assuming equal pad coefficients of friction, and I clarified later that my calculation was based on the smaller SX rear caliper. Regardless, yes you can adjust bias with different pad compounds, and you may be able to get the V6 Toyota/later SX caliper combo to work ok with the right pad combination. The challenge is finding a published friction rating for a given pad so that you're not just swapping pads at random until you find a combination that works. Many pads have a 2 letter code printed on them that provides the friction range, but you can't get that until after you bought the pads.

 

For my own personal setup, which includes AZC Wilwood fronts and my own Jag/Lincoln rear design (http://forums.hybridz.org/topic/113199-yet-another-rear-drum-to-disk-conversion-option/), I started out with some EE code pads (0.25 to 0.35) in the back that I had left over. As I suspected, based on the math, even with full rear line pressure, I couldn't get the rears to lock. I then switched to EBC Yellow Stuff GG code pads (0.45 to 0.55), which the math indicated would be a better match, and sure enough, I've had to decrease rear pressure by three turns on my adjustable prop valve to achieve a slight front bias.

 

 

I was looking for your qualifying statement and missed it as I was reading too fast.  My apologies.

 

 

KTM

 

What master cylinder and booster are you using?

 

Miles, I believe you and I have disagreed with this setup in the past. I am not advocating this setup but merely offering a counterpoint that it can work.  When I bought this setup it was the only setup outside of Wilwood for our cars.

 

I have a 240z booster and a 1979 (if I remember correctly) 280zx 15/16 master cylinder.

[Miles]

KTM

 

No problem. I have been experimenting with different rear brake and master cylinder combinations.

[Miles]

DOT brake pad edge codes.  Codes are based on SAE Standard J 866.

 

See picture.

 

If you know your pad edge code it could be added to this thread.

Edited August 14, 2013 by Miles

[Leon]

Interestingly enough, it appears that the S12W (vented caliper with 43/34mm pistons) and the 240SX (38mm piston) using the 300ZX front and rear rotors (vented front rotor and solid 290mm rear rotor) has VERY SIMILAR brake bias to the Silvermine Motors kit...actually slightly more!

 

This all neglects pad area, which is a big contributor to overall braking...For a given piston diameter, the larger friction surface of the pad makes for not only more drag on the rotor, but also more heat absorption area. You can't convince me, nor will the mechanics show, that a 38mm piston with a 38mm circular pad area can apply just as much friction to the rotor as a 38mm piston with a pad with double the surface area, but the same top and bottom heights, such as an elongated kidney shape. Pad size does make a difference in braking capability of a given caliper, even if the piston sizes are the same.

 

Ok, let's just discard physics all together then...

 

I guess countless physicists and hundreds of years of experimental data must all be wrong then? The force of friction is due to the coefficient of friction between two objects and the force pushing them together. That's all. Surface area is effectively irrelevant. If you place a 50 pound block on one square inch, you have 50 lbs per square inch of force. But doubling the surface area to 2 square inches does not double the weight applied. You're still applying the same 50 lbs block, but now to two square inches, so in effect you're now only applying 25 lbs per each square inch. You've doubled the area, but halved the force. That's why surface area is irrelevant.

 

Nigel

 

Thanks for saving me the explanation, Nigel. Well said.

Edited August 14, 2013 by Leon