Just installed new rotors and pads, fronts dragging. - LotusTalk - The Lotus Cars Community
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post #1 of 22 (permalink) Old 03-01-2011, 04:07 PM Thread Starter
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Exclamation Just installed new rotors and pads, fronts dragging.

Just spent my entire day installing new DBA4000 rotors and Hawk HPS pads at all four corners.

The rears came out just fine, but the front wheels don't turn freely. Just drove 4 miles to try to break them/bed them in and it's a bit better but still unacceptable. Without the pedal pressed the brakes will still hold the car on a slight incline. I'd compare it to having a parking brake pulled just a few clicks (maybe half applied).

Yes I retracted the front pistons all the way (flush with the caliper housing).

Thoughts?

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post #2 of 22 (permalink) Old 03-01-2011, 04:30 PM
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Did you use brake caliper grease on pads? Did the pads slide into position easily?

And I hate to ask, but are they facing the right way?
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post #3 of 22 (permalink) Old 03-01-2011, 05:01 PM Thread Starter
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I used brake caliper grease (supplied) on the backing plates.

The front pads did not slide into position easily, but were tapped into place with a drift and small hammer with not much effort. Snug fit, but a fit nonetheless.

No buzzing, rattling, squealing, scratching or sound of doom in general, just an awful lot of resistance. I'm guessing 20 miles might wear them into normal operation, but then again, they might catch fire in 20 miles. Since I view brakes as one of the important boundaries between my life on Earth and an unscheduled departure to the hereafter, I'd like a handful of opinions before I tempt fate.

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post #4 of 22 (permalink) Old 03-01-2011, 05:13 PM
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did you clean the hubs before putting the new rotors on?

If not you might have a run-out issue with dirt or rust behind the rotor hat, spacing the rotor out enough to hit the outboard pad.

Or the rotor could have excessive run-out I suppose. Though least likely.

did you read this?
https://www.lotustalk.com/forums/f91/...-issues-77090/

Looks like their Hawk pads were too thick to fit. And they had a tab...

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post #5 of 22 (permalink) Old 03-01-2011, 05:18 PM
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Hmm... did both inside and outside pads require being tapped into place?

New pads + new rotors = minimum clearance... but I haven't had to use a hammer to put in new pads.
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post #6 of 22 (permalink) Old 03-01-2011, 05:21 PM Thread Starter
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I cleaned the hub surface with cleaner and wire brush (still a trace of rust though), then lightly coated it with Copaslip anti-seize compound.

Both inner and outer pads needed to be tapped in (both sides). There was definitely a runout issue with the previous set, the driver's side outer pad was 1/3 the thickness of the inner pad. Passenger side wore equally.

On this installation, both the left and right wheels have near identical resistance.

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post #7 of 22 (permalink) Old 03-01-2011, 05:26 PM
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The run-out issue is different than pad wear rates. Run-out is a measure of how the assembly would wobble if the rotor were warped or made crooked.

Pads wearing differently is sometimes normal, though usually a big difference points to a problem with the piston sliding in the bore, or with the caliper slides, or the pad sliding on the caliper. Since the Elise has 2 piston fronts, it would wither be the pad sliding on the caliper or the pistons in the bore. But since you had to tap the pads in on the slides... Sounds like the pads are sticking on the slides. Those need to be totally cleaned, or replaced, and lubed with the graphite pad lube.

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post #8 of 22 (permalink) Old 03-01-2011, 05:31 PM Thread Starter
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Not sure what you're referring to by slides. My E-type Jaguar piston faces had a T-section on the piston that a groove on the pad would slide onto. The Elise has no such thing. The pads just hang from the locating pins between the piston and rotor surface.

Installing the pads could best be described as an interference fit.

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post #9 of 22 (permalink) Old 03-01-2011, 05:38 PM
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Right. It's been a while since I helped my friend change pads on an Elise. I have an Esprit... The pads on the Esprit and most other cars have shoulders that slide on spring clips or edges of the caliper as the piston push them.

THe Elise AP racing brakes have pad retaining pins and anti rattle springs. The pad must be free to slide on these pins. Rust and lack of lubrication can cause the pads to wear unevenly since they can't slide properly. The pads can also wear uneven if one piston is rusted or stuck in the caliper bore.

Lotus Elise Maintenance, Front Brake Pad Replacement

Did your Hawk pads have tabs on the back? Or did you use shims behind the pads?

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post #10 of 22 (permalink) Old 03-01-2011, 07:15 PM Thread Starter
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Well, I just went out to the garage to re-inspect my work. Jacked the car on one side, grabbed a wheel spoke with my left hand to rotate it and crushed two fingers between the spoke and brake caliper.

Burst a few blood vessel, no nerve damage, but I won't be playing bass for a few days.

Why don't I just pay people to do my mechanical work??????

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post #11 of 22 (permalink) Old 03-01-2011, 07:35 PM
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I haven't done the brakes on my Elise, yet, but I've changed pads on all of our other cars. I agree that the pads have to slide rather freely. Definitely should be able to push them in by hand (after retracting the piston, obviously )
I usually use some fine sandpaper on the channels and then put some lube. Do the calipers have little brass inserts in the channels? Those are usually just clipped in and can get bent. Then the tab on the pad will get stuck. Maybe they got bent under?
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post #12 of 22 (permalink) Old 03-01-2011, 07:42 PM
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I just read all the posts and my mind was headed toward the caliper guide pin sleeves as well. If brass, the tapping to get the pads in perhaps distorted them, so the caliper can't quite retract fully? Bummer about the finger.
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post #13 of 22 (permalink) Old 03-01-2011, 07:55 PM
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Eric, did you clean and grease the guide pins, as well as the part of the caliper directly above and below the pads (the part the the backing plates slide against, not to be confused with the back of the plate in contact with the piston)?

Top and bottom arrows are the points of contact between the backing plate and the caliper... middle arrow is the contact point of the upper guide pin...
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post #14 of 22 (permalink) Old 03-01-2011, 08:30 PM
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Quote:
Originally Posted by ErictheBastard View Post
Well, I just went out to the garage to re-inspect my work. Jacked the car on one side, grabbed a wheel spoke with my left hand to rotate it and crushed two fingers between the spoke and brake caliper.

Burst a few blood vessel, no nerve damage, but I won't be playing bass for a few days.

Why don't I just pay people to do my mechanical work??????
OUCH!!

But you're not the first or second person to complaint about front brake dragging. Front brake drag on Lotus is quite normal. I know my elise also didn't not glide as free as other cars.
https://www.lotustalk.com/forums/f91/...problem-35724/
https://www.lotustalk.com/forums/f91/...t-video-80008/
https://www.lotustalk.com/forums/f91/...ragging-71951/
https://www.lotustalk.com/forums/f91/...rubbing-69319/
https://www.lotustalk.com/forums/f101...rubbing-55742/
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post #15 of 22 (permalink) Old 03-02-2011, 07:32 AM
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Quote:
Originally Posted by ErictheBastard View Post
Well, I just went out to the garage to re-inspect my work. Jacked the car on one side, grabbed a wheel spoke with my left hand to rotate it and crushed two fingers between the spoke and brake caliper.

Burst a few blood vessel, no nerve damage, but I won't be playing bass for a few days.

Why don't I just pay people to do my mechanical work??????
Ouch!!! I seem to like to do that every couple years loading motorcycles into my truck. Not fun. I hope it wasn't your pimp hand.
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post #16 of 22 (permalink) Old 03-02-2011, 08:08 AM
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Just spent my entire day installing new DBA4000 rotors and Hawk HPS pads at all four corners.

The rears came out just fine, but the front wheels don't turn freely. Just drove 4 miles to try to break them/bed them in and it's a bit better but still unacceptable. Without the pedal pressed the brakes will still hold the car on a slight incline. I'd compare it to having a parking brake pulled just a few clicks (maybe half applied).

Yes I retracted the front pistons all the way (flush with the caliper housing).

Thoughts?
Sometimes the boys at Hawk get a little over enthusiastic with the pad paint. There is a reasonable chance that the black coating is slightly thicker than ideal, causing the "interference fit" installation you've described.

If that is the case (and I can't check it from here), I would suggest removing the front pads and hitting them very lightly on a belt or disc sander. The goal would be to remove the paint from the edges that contact the pad wear abutments in the caliper (both leading and trailing), not grind the steel back plate down, so go easy.

Make sure you lube the fresh, ready to oxidize ends with Hawk's lube or, even better, the Permatex Ceramic Extreme purple goo.

Chris
post #17 of 22 (permalink) Old 03-02-2011, 08:57 AM Thread Starter
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Found the culprit!

On the Hawk HPS pads, there's a small locating pin (upper right hand in the pic) that obviously is there for another application of this pad. It is slightly proud of the backing plate (.5mm perhaps?) and this was causing the excessive interference.

Once I filed them flush with the backing plate (even though I am now crippled), the whole assembly fell right together and there is now normal pad contact.
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post #18 of 22 (permalink) Old 03-02-2011, 09:42 AM
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Those must be for a last gen Subaru STI Rear brembo caliper. I had the same pin with a
set of stoptech pads for an STI I put on for another LT member.

We however did not have any issues as the stock rotors were already a bit worn... I'm guessing your new pads and rotors together were just thick enough for the pins to cause a problem.

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post #19 of 22 (permalink) Old 03-02-2011, 09:42 AM
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Yikes, I should have mentioned that pin... I had to file it down on my first set of HT-10s, but since then the sets I get already have that pin ground down.

BTW, interesting to see a shim already bonded to the pad... race pads don't come that way.
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post #20 of 22 (permalink) Old 03-02-2011, 10:05 AM
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On the Hawk HPS pads, there's a small locating pin (upper right hand in the pic) that obviously is there for another application of this pad. It is slightly proud of the backing plate (.5mm perhaps?) and this was causing the excessive interference.

Once I filed them flush with the backing plate (even though I am now crippled), the whole assembly fell right together and there is now normal pad contact.
Good work! That pin is for riveting a pad sensor or "squealer" that some other applications require (per the OEM).

I just let Hawk know they need to watch this on future runs, but there are many sets already on shelves in the field.

Chris
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