Spec Miata Community   
search | help | calendar | games | forum home

  next oldest topic   next newest topic
» Hello Spec Miata Community » SpecMiata.com » Spec Miata Garage » RF Brake Drag

 - Email this page to someone! | Subscribe To Topic  
Author Topic: RF Brake Drag
tom_hampton
Member

Region: SW
Year : 1992
Posts: 51
Status: Offline
Icon 1 posted  Profile for tom_hampton   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Again, I searched. The problem seems to be that there isn't a lot of resolution in these types of "issue" threads. A lot seem to die out with numerous suggestions, but no definitave reply stating "this was it, its fixed."

This is another one of those things I'm trying to clear up BEFORE I go to get an alignment.

My RF pads are dragging signficantly more than any other corner. LF wheel will spins maybe 10 revolutions before coming to a stop. You can hear a bit of pad drag on the LF (normal, I know), but the RF wheel only rotats about 2 (the pedal drag is distinct and continuous).

Worse still, I have a TON of brake dust on the RF wheel from driving the car to work 4 times, and test drives...only. Maybe 300 miles total.

The car also veers right on initial braking, but it doesn't continue to veer. IE, On fist application of brake it jumps right, but once pressure stabilizes the car decelerates in a straight line even with hands "off the wheel".

I rebuilt and painted the calipers last month (admittedly, my first rebuild...so it could be the monkey with the wrench). I've removed the clips and springs. I've adjusted the brake pedal pushrod length to the point that the brake lights stayed on (er...can you say dead battery [banghead] ). Pins are lubed with CV2, also checked for free movement.

At this point, I'm thinking either:

  • bad caliper / bad rebuild
  • bad proportioning valve
  • bad master cylinder

The MC seems the least likely because its only one wheel, not front/rear.

I'm running PF97s on all 4 corners, and brand new Castrol LMA. All brake parts are 1992 original (AFAIK). There was no rust in any caliper cylinders, and everything went back together without any perceived issues.

--------------------
---
Tom Hampton
Miata build: http://www.tomhampton.info

Frank Todaro
Member

Region: Ohio Valley Region
Car #: 35
Year : 1999
Posts: 170
Status: Offline
Icon 1 posted  Profile for Frank Todaro     Edit/Delete Post  Report this post to a Moderator

I run clips and springs on my calipers, did you "remove" them permanently? Of the things on your list most likely I would think its the caliper. the Master would have the same effect on all the brakes. I don't know much about the proportioning valve but would expect it falls in the same class and the Master.
One think not on your list is the Hub, I would check it without the caliper on.
If you did not have the problem before your rebuild then that is the likely cause.

--------------------
Frank
Member: No Pain Racing

CP Verified Driver
Member

Region: NER
Car #: 7
Year : 1999
Posts: 636
Status: Offline
Icon 1 posted  Profile for CP   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Uh, buy a new caliper?

--------------------
-Cy
Supported by LTD Racing & Speed Shack - New England's Premier Auto Accessory Store
Rt1 AutoMile - Norwood, MA
http://www.speedshackonline.com

SAE113 Verified Driver
Member

Region: Central Florida
Car #: 01 & 99
Year : '92 & '94
Posts: 137
Status: Offline
Icon 1 posted  Profile for SAE113     Edit/Delete Post  Report this post to a Moderator

brake hose

--------------------
Steven Elicati
'92 Protege ITA#01
'94 Miata ITA#99

tom_hampton
Member

Region: SW
Year : 1992
Posts: 51
Status: Offline
Icon 1 posted  Profile for tom_hampton   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Hubs rebuilt 3 weeks ago. They don't spin like JD's in his video, but they both spin similar to each other. And the pads are definately dragging much heavier on the RF. Its audible when you turn the wheel by hand.

The proportioning valve is in series with the RF brake line coming from the MC. The LF brake line comes straight off the MC and does NOT pass through the prop-valve. Hence my suspicion. And the reason I think the MC is NOT at fault.

Brake lines are brand new braided.

New caliper, sure...no harm done in a new caliper. I was hoping to avoid the buying stuff from Mazda one at a time thing. So much cycle-time involved in that. Buy it, try it, buy the next thing, try it...etc. Weeks go by.

I suppose I could buy a prop-valve and MC along with a new caliper.

Now that I think of it, the RF was a little difficult to bleed. At the time I chalked it up to perhaps being completely full of air. I had to resort to the "open, push, close, release, open, push, close, release" method to get it to bleed. Even after fluid started coming out it was still VERY slow to bleed.

I don't know if the unmodified car exhibited the same issue. I never checked for brake drag before dissasembly. It drove fine, but so does this. I don't know if I would have made note of a turn on initial bite...or just attributed it to one of many quirks in a 214,000 mile donor car that the seller got in the breakup. I'm pretty sure this was a revenge sale. [Big Grin]

--------------------
---
Tom Hampton
Miata build: http://www.tomhampton.info

Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
Posts: 2000
Status: Offline
Icon 1 posted  Profile for Keith in WA     Edit/Delete Post  Report this post to a Moderator

Brand new rotors and brand new pads? Some pads fit pretty tight with brand new rotors and the tollerances aren't balls on.

--------------------
Keith Novak
(Will work for tires)

tom_hampton
Member

Region: SW
Year : 1992
Posts: 51
Status: Offline
Icon 1 posted  Profile for tom_hampton   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Yes...and yes. Hmmmm...

--------------------
---
Tom Hampton
Miata build: http://www.tomhampton.info

B Wilson Verified Driver Series Champ
Gold Member

Region: Oregon
Car #: 68
Year : 91
Posts: 2359
Status: Offline
Icon 1 posted  Profile for B Wilson   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

So take it all apart, and switch disk/pads from side to side and report back.

Sounds to me like you have something bent or caliper sucks. While apart inspect and compare caliper brackets. (forget that, I just re-read your bleeding issue, just replace the caliper)

This may be a good time to start buying spare parts (used is okay especially for these types of issues), you'll need them in the future. Also a great time to start finding fellow racers with spare parts. You'll find we do a lot of horse trading/sharing.

Here I'll ask, anyone in the SW got a spare NA used RF caliper Tom can try on his car?

-bw

--------------------
Bruce Wilson
2010 Oregon Region Champ
2010 Monte Shelton Driver of the Year
2010 25 Hours of Thunderhill E3 and Under 2 liter Overall Champion
Oregon Region SM Class Advisor

tom_hampton
Member

Region: SW
Year : 1992
Posts: 51
Status: Offline
Icon 1 posted  Profile for tom_hampton   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Bruce-

Thanks for the advice. As I've noted in another thread I haven't met anyone in this class yet. I've been to a couple scca meetings kinda hoping to, but it was all srf guys.

I guess I hadn't felt presumptuous enough to ask to borrow parts. Im in the dfw area.

I'd noticed from following along, over the last year, that people trend to replace, and then rebuild the old part and put in the spares bin. So that is what I have been doing with other parts I've removed.

My tendancy has been to buy new...particularly for critical parts. At 214 k, it is a higher mileage donor..most parts appear original. Only the lf hub has clearly been replaced (new style).

--------------------
---
Tom Hampton
Miata build: http://www.tomhampton.info

d mathias Verified Driver Made Donation to Website
Member

Region: OVR
Car #: 88
Year : 1991
Posts: 2401
Status: Offline
Icon 1 posted  Profile for d mathias     Edit/Delete Post  Report this post to a Moderator

FYI - my policy has always been to replace brakes in pairs, that is, if you are replacing the RF caliper, then replace the LF caliper too.

Gibscreen Verified Driver Series Champ
Member

Region: NASA-SoCal
Car #: 23
Year : 1995
Posts: 912
Status: Offline
Icon 1 posted  Profile for Gibscreen   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

You never answered Frank Todaro's question about whether you permanently removed the clips and springs. The springs pull the pads away from the rotor in a uniform manner, so without the springs its entirely possible that one side has the pads resting against the rotor and the other side not so much.

I agree its frustrating reading other threads where there is no resolution, just suggestions. Its also frustrating offering simple suggestions that the OP doesn't rule out.

--------------------
Rob Gibson
RJ Racing
2010 NASA Nationals TTE Champion
2008/2009 WERC Champion
2007 NASA SoCal SM Champion
rjracing.net
Weekend-Racer.com

B Wilson Verified Driver Series Champ
Gold Member

Region: Oregon
Car #: 68
Year : 91
Posts: 2359
Status: Offline
Icon 1 posted  Profile for B Wilson   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

[Wink]

I was going to post a thread about why veterans don't answer questions anymore, but that would be one of the reasons...

There's hardly ever a simple answer to questions like these. But I'd be fixing, buying new, or buying 2 new calipers right about now [Big Grin]

-bw

--------------------
Bruce Wilson
2010 Oregon Region Champ
2010 Monte Shelton Driver of the Year
2010 25 Hours of Thunderhill E3 and Under 2 liter Overall Champion
Oregon Region SM Class Advisor

tom_hampton
Member

Region: SW
Year : 1992
Posts: 51
Status: Offline
Icon 1 posted  Profile for tom_hampton   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Rob-

Sorry, I missed that question in all the others. I was running the springs and clips until last weekend. I didn't intentionally neglect to answer it. I have ben trying to respond to all...I just missed it.

I removed them while troubleshooting the squeal that turned out to be my speedo cable. Brake drag preceded removal of clips and forums...and did not change after removal.

Bruce-

Sorry...my statement was really meant to say that the OP often doesn't return to the thread to clear up the final outcome. So, you can read lots of suggestions from the kind folks who try to help...but, not what the final answer turned out to be.

In the few question threads that I've started...uv tried to make a point to come back and say what I finally found the issue to be (eg speedo cable).

I have a prop valve, and 2 calipers in my mazda cart as I type. I was going to get a MC, too...but, they are on back order.

--------------------
---
Tom Hampton
Miata build: http://www.tomhampton.info

Gibscreen Verified Driver Series Champ
Member

Region: NASA-SoCal
Car #: 23
Year : 1995
Posts: 912
Status: Offline
Icon 1 posted  Profile for Gibscreen   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Tom,

Call Tim at Mazdaspeed re: the MC. The online catalog only shows rebuilt MCs but Tim will give you the p/n for a brand new MC that costs maybe $20 more.

--------------------
Rob Gibson
RJ Racing
2010 NASA Nationals TTE Champion
2008/2009 WERC Champion
2007 NASA SoCal SM Champion
rjracing.net
Weekend-Racer.com

MIATA 17 Verified Driver
2X SMMC Winner


Region: Milwaukee
Car #: 17
Year : 97 & 99
Posts: 107
Status: Offline
Icon 1 posted  Profile for MIATA 17     Edit/Delete Post  Report this post to a Moderator

Did you put the grease the piston and seal when rebuilding?

If you did, unfortunately it's time for a new or reman caliper. Some times when the caliper's get too worn, the piston rocks inside the caliper bore and they stick not releasing properly and thus causing brake drag. Only way to fix realistically is to replace it.

Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
Posts: 2000
Status: Offline
Icon 1 posted  Profile for Keith in WA     Edit/Delete Post  Report this post to a Moderator

The other thing that happens with 20yo calipers, is that they probably didn't have the freshest, thickest pads in them, so they spent a lot of time not going all the way back into the bores. The black nasty brake fluid causes corrosion on the deepest part of the bore that hasn't been touched in years, and you have a sticky spot.

If you're going to change the brake prop and MC, I'd do them both at once, and bench bleed the MC before installing it. Unless of course you want to spend most of the winter bleeding and rebleeding the brakes.

--------------------
Keith Novak
(Will work for tires)

tom_hampton
Member

Region: SW
Year : 1992
Posts: 51
Status: Offline
Icon 1 posted  Profile for tom_hampton   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Yes...I put the grease on the seal and piston. I'll get all parts and swap one at a time. Will report back.

Thanks.

--------------------
---
Tom Hampton
Miata build: http://www.tomhampton.info

CP Verified Driver
Member

Region: NER
Car #: 7
Year : 1999
Posts: 636
Status: Offline
Icon 1 posted  Profile for CP   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Lube the seal and piston with brake fluid.

--------------------
-Cy
Supported by LTD Racing & Speed Shack - New England's Premier Auto Accessory Store
Rt1 AutoMile - Norwood, MA
http://www.speedshackonline.com

iambhooper
Member

Region: NCR
Car #: NA
SMIM: NA
Posts: 125
Status: Offline
Icon 1 posted  Profile for iambhooper     Edit/Delete Post  Report this post to a Moderator

not trying to hijack the thread, but searching for some of my handleing ill's from the go, i found that the wear on my RF Hawk blues looked like ]/[ if you stacked the pads together.

pad's have been used 2 weekends. now i know VIR does put a lot of strain on the RF's, but i've never seen that on pad's before.

--------------------
hoop
'91 Spec Miata
'90 NA Beater/Track Day car
'06 RSX Type S

   

   Close Topic   Feature Topic   Move Topic   Delete Topic next oldest topic   next newest topic
 - Printer-friendly view of this topic | Subscribe To Topic
Hop To: