48 replies to this topic

[DrDomm]

Hmmm...interesting.

[svvs]

I used to keep the parking brake for trailer and stuff.  Then they dropped the 1.6 weight from 2300 to 2285.....well it was time to lose some weight.

 

I have had some times before I got rid of the adjusters where I felt the drag.

 

When I tap the brakes to make sure there are some there....if I feel the car slow I know I messed up.

 

At the end of the day, it's a relatively easy thing to do (1-800-order me some parts) so I did it.  I'm happy I did.

 

-Vick

[Bench Racer]

 

I get it if you're gonna go all out with every other possible mod to increase HP and decrease drag, friction, and rotating mass.  But as a stand alone mod for the average mid-pack car?

1/10 sec. + 1/10 sec. + 1/10 sec. off you lap time = you get the idea = a move forward from midpack. 

 

If you'd like a hydraulic/electrical schematic warning light system for brake pad kickback so there is no need to tap your brake pedal, it's available.

[DrDomm]

Ugh, I've got to do this, huh?  Ok.

[LarryKing]

Nobody 'has' to do anything.

[davew]

We won 5 majors last year among 3 drivers and finished second at the Runoffs with un-modified calipers.

 

You don't have to do anything.

 

Dave

[Bench Racer]

We won 5 majors last year among 3 drivers and finished second at the Runoffs with un-modified calipers.

 

You don't have to do anything.

 

Dave

Sorry Dave, other than continiously adjust the rear caliper to eliminate brake pad drag. 

[mvzante]

I used to keep the parking brake for trailer and stuff. Then they dropped the 1.6 weight from 2300 to 2285.....well it was time to lose some weight.

Where do you get 2285 from? I see 2300 on page 720 of GCR.

[davew]

Adds 2 minutes to my nightly brake inspection. Not a big deal to me or my crew.

[davew]

Where do you get 2285 from? I see 2300 on page 720 of GCR.

That weight was several years ago.

 

Dave

[Muda]

It's OK, you don't get weighed very often in a 1.6 these days. 

[mhiggins10]

OK- I'll bite.  What is this tapping of the brakes business?  If you don't slow the car AT ALL, how do you know they're there for you?

 

I definitely see the benefit of making SURE they are there before a big braking zone, but am trying to figure out how to really use this technique.

[Todd Lamb]

It's not about tapping the brakes to feel they are there - if you feel the brakes engage when you tap the pedal you've tapped too hard and slowed yourself down.

The goal is to close the gap back up between the pad and the rotor. The gap is caused by pad knockback - while going over apex and exit curbing (especially the aggressive type like at Road America) the pistons will get knocked back into the calipers by the vibration of the brake pads over the bumps. So a quick tap or two resets the pistons, pushing them back out and closing up the gap, so you have a solid pedal in the next brake zone.

[Muda]

After the first time you get that deeeep pedal after crashing the curbs in the previous turn you won't have to ask that question......ever again. 

[mhiggins10]

It's not about tapping the brakes to feel they are there - if you feel the brakes engage when you tap the pedal you've tapped too hard and slowed yourself down.

The goal is to close the gap back up between the pad and the rotor. The gap is caused by pad knockback - while going over apex and exit curbing (especially the aggressive type like at Road America) the pistons will get knocked back into the calipers by the vibration of the brake pads over the bumps. So a quick tap or two resets the pistons, pushing them back out and closing up the gap, so you have a solid pedal in the next brake zone.

Makes sense Todd- I guess I haven't banged over apex curbing hard enough to notice yet (or I just have old, sticky calipers that need the adjusters removed).  So this is really just a light breath on the pedal to firm things up?  Seems easy enough...

[James York]

Makes sense Todd- I guess I haven't banged over apex curbing hard enough to notice yet (or I just have old, sticky calipers that need the adjusters removed).  So this is really just a light breath on the pedal to firm things up?  Seems easy enough...

I typically give them a quick double tap as I approach the brake zone while still at WOT (note this is not a "press" on the brake).  I don't know what tracks you have run yet, but those around Houston don't really cause an issue with pad knock back.  But I have gotten into the habit of doing it from other tracks, so I tend to do it if I have any concerns.

 

You'll know it when it happens.  In my first visit to Road America for the Runoffs, I flew off turn 3 on a test day as the loss if pedal caught me by surprise.  The dragon teeth type apex/exit curbs there really put vibrations into the car.  If anything is lose, it is bound to fall of at RA.  

[mhiggins10]

It's been mostly just MSR Houston for now, and the curbs are pretty easy there.  I'm hoping to get to TWS and MSR Cresson this year, but I imagine they're pretty easy on curbs as well (I've run other cars at TWS, but never been to MSRC).

 

Either way, if it's a technique I should be working on for general betterment of the nut behind the wheel, it's probably better to be practicing now than when I realize I should be using it in a practice or qualifying session down the road.

[SaulSpeedwell]

I should invoke the Daniels Ten Foot Pole rule here, but what fun would that be? 

 

I don't do calipers anymore except for friends - probably 3 sets a year - and the reason is multi-fold:

1.  One of the suppliers (not Mazda) of rubber bits made or distributed some stuff that wasn't up to snuff and seals extruded past the pistons.  Not cool.  I was lucky in that only one of my customers experienced this issue.  Attempts to get to the bottom of it with the suppliers and caliper rebuilding "industry" were met with stonewalling (again not talking about Mazda here).  Even less cool.  Mazda's seals are great and the best, in my opinion, and everything else I treat with suspicion until the calipers have "proven themselves".  Unfortunately, Mazda's seals are expensive.  If your calipers are not leaking and your seals are pliable, I would leave them be.  Replace your scorched dust boots, bloated grease boots, sloppy caliper brackets, scuffed pins, replace rear pins preventively according to experience, etc., but if the piston, body, and seal are happy - leave them be.  Especially if you have already seen the inside and verified a nice smooth shiny piston and a body with no sand or other weirdness inside. 

 

2.  MANY MANY MANY people had trouble getting their cars bled, because they essentially bled out the whole rear circuit while changing calipers or awaiting their return.  I also think people failed to realize the left rear is the farthest from the master cylinder - not the right rear!  EVERY one of these cars was fixed with "proper" bleeding.  Unfortunately, "no bubbles" doesn't necessarily mean you are fully bled (See also clutch slave cylinder!) 

 

3.  Non-sticking calipers means you CAN get pad knockback that your old sticky calipers didn't exhibit.  On rears, not having the adjuster installed can exacerbate the knockback.  Especially at tracks with ripply curbing.  Never a problem at Mid-Ohio, but could admittedly be a real Code Brown issue at Road America. 

 

Having said that  - some people may want to understand how the adjuster works before making a decision. IF the adjuster is working properly, a manual adjustment WILL NOT last an entire session.  Said "backwards", IF your manual adjustment remains stable for a session, THEN your adjuster is already "not working".  With a properly working adjuster, you'll be lucky if your manual adjustment lasts 2 laps.  Prove it to yourself.  Back it way off.  Put the capscrew back in, start the engine, make 10 brake applies.  The running clearance of the adjuster is designed to be pretty tight (function of wave springs and funky BNC-connector looking cam barrel thing) and it adjusts "fast" (function of the helix angle on the jackscrew thread).  The internal friction of the adjuster IS CRITICAL - but notice the thing ain't exactly a ball bearing.  It's a bunch of sloppy claptrap.  There are EIGHT components in the damn thing and it doesn't work very well.  (I assume Mazda copied it from Mercedes).

 

I made a few custom sets for the "I love my park brake" crowd where we "converted" the adjuster to being a pure manual setup.

 

Long story short:  This adjuster depends on friction to work, and it is all made of slip fits.  Some of them work too well, some of them don't work at all (yay!), and a lot of them are in-between.

 

All this would make for a diabolically boring YouTube video someday ...

 

P.S. To Todd's point, regardless of the voodoo happening in the rear calipers of our production-based cars, the FRONTS have no adjuster, and no corner of a "real racecar" has an adjuster.  Pad knockback is a reality of racing, at least at some tracks.  The best drivers know how to address it, and that is why you see all those phantom "premature" brake lights down the straights.

[DrDomm]

I was a brake pad kickback non-believer...until the exit curbing of Turn 5 at Road America showed me the light.  Fortunately there's plenty of opportunity to make Turn 6 in these cars. 

[Muda]

You're not taking nearly enough exit curbing at T2 Thunderbolt.