33 replies to this topic

[LarryKing]

To clarify, I would never run rotors that are anywhere near the minimum thickness. They can overheat and break.

As far as the "snug fit" - I wonder if thats a 1.8 issue? I've heard others complain of that but I've never experienced that on my 1st gen Miata.

[Jim Drago]

To clarify, I would never run rotors that are anywhere near the minimum thickness. They can overheat and break.

As far as the "snug fit" - I wonder if thats a 1.8 issue? I've heard others complain of that but I've never experienced that on my 1st gen Miata.

Every car I have ever raced starts with used rotors turned to min thickness, rotating weight. I would rather buy used factory rotors and pay to have them turned to the minimum than run $15 Chinese rotors for free. The new $15 rotors are 5x more likely to crack IMO, I have never cracked a used rotor turned to minimum. I get a season out of them easily.
I also feel that 30-50k of street driving tempers the rotors a bit, I may be completely wrong, but that is my belief, I also get a pretty good deal on used rotors

[Keith Novak]

As far as the "snug fit" - I wonder if thats a 1.8 issue? I've heard others complain of that but I've never experienced that on my 1st gen Miata.

Could be. I had the issue with different brands of pads.

I was concerned that running them at the min would cause issues too but apparently not. As cheap as rotors are (even good new ones) one set for a season is a drop in the bucket compared to other costs. I doubt I'd ever buy another set of cheap $15 rotors either. I took off my Brembo rotors to bed pads on a set of generics so I'd always have rotors ready to go and I started seeing cracks in the rotors, odd pad wear and cracks in the pads and the pads are MUCH more expensive than the rotors.

[Ron Alan]

Every car I have ever raced starts with used rotors turned to min thickness, rotating weight. I would rather buy used factory rotors and pay to have them turned to the minimum than run $15 Chinese rotors for free. The new $15 rotors are 5x more likely to crack IMO, I have never cracked a used rotor turned to minimum. I get a season out of them easily.
I also feel that 30-50k of street driving tempers the rotors a bit, I may be completely wrong, but that is my belief, I also get a pretty good deal on used rotors

My thinking exactly...just had never heard anyone talk about this. Thanks for the conformation...I knew there was a reason I saved all those OEM rotors off those junked cars


Anyone have an answer to the caliper question?? Jimmy??

[SaulSpeedwell]

After you dis-able the parking brake... I'll sell you some magical brake fluid worth another 2 h.p.

How much is it?

I would never run with the e-brake hardware though.. I don't see an upside.

Yeah, but how much would you two pay if I sent you a caliper adjuster that was demonstrated to cost 2HP (and falling) for 1/4 second (and counting) following a full brake application on the dyno?

I mean, it's just a piston riding on a steep-helix ACME thread with a "bearing/follower" comprised of an as-cast wheel cunningly slop-fit into the piston with no "bearing" to speak of and a stack of Belleville washers dragging along the face every time it moves in and out, all of it submerged in not-very-lubricious brake fluid (and, about 10% of the time, some sand left over by the remanufacturer), with nothing to retract it but a little rubber piston seal and a few thousandths rotor caliper runout ... you know ... not exactly "rocket science"

[SaulSpeedwell]

FWIW, min thickness rotors are fine unless something else is wrong ... or unless it is the front of a 1.6 at certain tracks with certain pad combos.

Used factory rotors are worth turning. No better rotor in the world than one that has had a zillion heat cycles on the street - they will wear better, resist cracking better, and stay together longer once they DO start cracking. Hell on the brake lathe tooling, though.

[Jim Drago]

Saul Speedwell

[Bruce Wilson]

Saul Speedwell

Hmm wonder who that might be??? quick somebody hit the quote button

[Bench Racer]

Do we also throw the original JD under the buss for suggesting that the rear pad to rotor clearance be checked & adjusted hot to reduce drag? IIRC checking clearance was before pulling the E brake caliper guts came on site.

[Bruce Wilson]

Not sure removing adjuster was legal then.

[Jim Drago]

I don't think there is a need to throw anyone under the bus? The rule never changed... A certain Brake Engineer from Elyria OH read the rules carefully, examined the calipers carefully and determined that gutting the rear calipers was within the existing rules and provided an advantage over those with rear e brake hardware. If your calipers are not gutted, you should absolutely check the clearance hot after every session IMO.

[Tom Hampton]

FWIW (not much?), when time is short between sessions, I've resorted to tap on the upper rear pad "ear" after each session. I can do that through the wheel spokes...even when hot. I run without the springs and clips. So, f it rattles I figure my clearance is adequate to prevent drag.

Once you set the adjuster properly, you can quickly get a sense of the right amount of "rattle" (60 thou vs. 30 thou, vs 15 vs 0).

[Jim Drago]

That is exactly what I used to do as well

[SaulSpeedwell]

Do we also throw the original JD under the buss for suggesting that the rear pad to rotor clearance be checked & adjusted hot to reduce drag? IIRC checking clearance was before pulling the E brake caliper guts came on site.

Many deserve some room under the bus on that one - but, if we're going to put JD 1.0 under there, we might as well ask him to align the rear end with a telescoping pointer while he is under there.

Fun experiment for you that still have e-brake guts installed - back off the adjuster to some big-ish number - say two nickel thicknesses, 0.090", something like that. Now install the access bolt with copper washer. Remeasure. Now take the copper washer out and reinstall the bolt. Remeasure. Report back.

The bottom line is the "running clearance" you set is temporary and meaningless unless you are lucky and your adjuster is broken or sticky. My first car was "lucky" in this way, which led to years of incorrect belief as to how the aduster mechanism worked. The clearance is set by the design of the adjuster.