Brake Failure At the Track - LotusTalk - The Lotus Cars Community
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post #1 of 21 (permalink) Old 08-26-2018, 06:44 PM Thread Starter
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Brake Failure At the Track

Did a rally this weekend, which included 2 track days,

On the first track day, about 15 laps in on the third session at the end of a small straight I was able to bring the car down from speed fine but when I went to the brakes in the next corner the pedal fell nearly to the floor.

I could pump it back up with 2-3 pumps and get some semblance of braking, but when it was happening it felt like I sprang a pinhole leak in one of the lines. I expected to see a puddle of brake fluid on the ground but after about 5 minutes sitting the pedal pressure came back to normal and stayed that way.

The track is Canaan up in NH, a small tight ex go kart track.
Car is a Rev 400 on R888Rs
And I had just put new RC5+ pads on the night before with fresh Motul 600.

I ran at this track last year, and didn't have a problem, but the brakes were smoking (grease burning off the back of pads and pins I'm guessing)

So this was unexpected, and these sessions weren't even 20 minutes.

Also I've developed what sounds like a brake pad rattle up front (since the pad swap) which hasn't gotten any better even after 2 track days. At low speeds it can be loud and really annoying, touch the brakes and it goes away or increase spead and it goes away.
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post #2 of 21 (permalink) Old 08-26-2018, 06:56 PM
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2 things and you should be set. You clearly boiled the fluid. no big deal and common.

1) Castrol SRF. FAR better fluid than motul.

2) Stainless steel caliper pistons that we sell. Cheap and a great improvement over the aluminum pistons in the stock calipers in terms of boiling fluid.

Hope that helps,

Phil
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post #3 of 21 (permalink) Old 08-27-2018, 04:20 AM
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wonder if that rattle is related. pad drag creating heat boiling fluid


check that brake disc temp compared to others
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post #4 of 21 (permalink) Old 08-27-2018, 06:04 AM
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Pad drag is definitely a possibility - but my guess is if that's the case it's from the driver's foot. Happens to a lot of people, especially if left foot braking and not used to doing so.
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post #5 of 21 (permalink) Old 08-27-2018, 09:10 AM
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The RC5+ are an aggressive street pad. I would look at using track pads for such events.

The Motul is fine for heavy braking but I'm guessing that top speeds were not too high on this go-kart track? Where did the leak come from?

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post #6 of 21 (permalink) Old 08-27-2018, 11:50 AM Thread Starter
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The rattling is loud and continuous at speeds under about 45. So any thoughts on if that's related and/or how to stop it would be good.
I wasn't doing any left foot braking, but I also wasn't driving the car hard enough (I would think) for brake fade. I was definetly pushing harder last year on old RC5s and didn't have a problem (but it was also colder out).

This seems really confusing
@shinoo there was no leak, I thought I had a pinhole leak when the issue popped up on track. When I got to the pits I still have a very full reservior and it stayed that way.

Did a track day again the next day and it didn't happen again, despite having to come down from 120-130 on the front straight, but I was driving pretty gently this day just due to the still unresolved issues.
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post #7 of 21 (permalink) Old 08-27-2018, 02:54 PM
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The rattle is the pad. I would start with a track pad. I ran a '05 Elise with 5+ on track and quickly found that they were inadequate. I then tried them on an even lighter ca (S190 Elise) and they still faded. Try our G-loc R10 or R12.

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post #8 of 21 (permalink) Old 08-28-2018, 01:08 PM
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Running a go kart track may not have let the the brakes cool enough between braking zones.

Shinoo's experience with RC5+ pads is the complete opposite of mine. I have run several track days with them and only had consistent strong braking with them. They are rubbish on the street, grabby, loud, and wear the rotor quickly because they need heat to create a transfer layer to function properly.

I run fresh Castrol synthetic DOT 3/4 brake fluid (not SRF) and BOE SS caliper pistons and have not had any issues (knocking on wood).
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post #9 of 21 (permalink) Old 08-28-2018, 01:52 PM Thread Starter
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Short video from from this weekend's rally, showing how loud the noise is:

Coming clearly from the front... stops when I touch the brakes @turbophil

The last set of RC5s I had made no noises like this and maybe a good squeek or two but could be taken care of with just modulation of the pedal.

Now on top of this noise when driving under about 45mph (and it's pretty consistent) they're starting to squeel under braking too.
@shinoo how streetable are the GLoc pads? I'd like to run similar pads with a slightly more agressive front pads and the BOE radial caliper mounts on the rear, to get some more rear braking bias.
Pads didn't seem to be the problem though. fluid or some other issue seemed to be the problem, but now I'm interested in potential brake upgrades.

Like I said I wasn't going hard (which might have led to me dragging the brakes more than diving on them when I was driving harder last year.)

Last edited by Ls1Rx7; 08-28-2018 at 02:03 PM.
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post #10 of 21 (permalink) Old 08-28-2018, 02:03 PM
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It's a fairly small track. Fast cars can get around close to 1:05. I get around in 1:10. I think you can get up to 110mph on the back straight in a high hp car. I don't think i get close to 100. But depending on their configuration, you might have to brake hard for a chicane at the edge of it.

So yea it's small, but i didnt it was small enough for cars to have issues. They run a lot of regular car events there. So yea, the brake boiling issue is odd. Wondering if theres something else going on there.

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post #11 of 21 (permalink) Old 08-28-2018, 07:42 PM
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Did you bed the new pads before the track experience? It could be you had green pad fade.That can be rather scary.
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post #12 of 21 (permalink) Old 08-28-2018, 07:47 PM Thread Starter
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Originally Posted by jmcwpb View Post
Did you bed the new pads before the track experience? It could be you had green pad fade.That can be rather scary.
Yeah I bedded them, and I could feel when they started grabbing liek they were supposed to.
I also drove it 70 miles to the starting point of the rally, then drove aother 70 miles (at high speed) to get up there all before getting on track.
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post #13 of 21 (permalink) Old 09-05-2018, 06:26 PM Thread Starter
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Quote:
Originally Posted by turbophil View Post
2 things and you should be set. You clearly boiled the fluid. no big deal and common.

1) Castrol SRF. FAR better fluid than motul.

2) Stainless steel caliper pistons that we sell. Cheap and a great improvement over the aluminum pistons in the stock calipers in terms of boiling fluid.

Hope that helps,

Phil
Ordered the stainless steel pistons, and new seals. Will report back.
Any thoughts on the video I posted about the brake noise?

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It's a fairly small track. Fast cars can get around close to 1:05. I get around in 1:10. I think you can get up to 110mph on the back straight in a high hp car. I don't think i get close to 100. But depending on their configuration, you might have to brake hard for a chicane at the edge of it.

So yea it's small, but i didnt it was small enough for cars to have issues. They run a lot of regular car events there. So yea, the brake boiling issue is odd. Wondering if theres something else going on there.

That straight has an on camber kink in it, and a minor slalom. I can get up to about 90 with the rev 400 setup. I think it'd be pretty close to impossible for a street car to get to 110
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post #14 of 21 (permalink) Old 09-05-2018, 08:11 PM
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Originally Posted by Ls1Rx7 View Post
Ordered the stainless steel pistons, and new seals. Will report back.
Any thoughts on the video I posted about the brake noise?




That straight has an on camber kink in it, and a minor slalom. I can get up to about 90 with the rev 400 setup. I think it'd be pretty close to impossible for a street car to get to 110
Yea haha, wasn't a street car. The guy i was talking to was actually racing a fully race prepped Chevy silverado. Nuts, i know. But yea i think he hits that speed after the kink. And depending on the track setup...if they remove the chicane, you can get more speed before having to brake.

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post #15 of 21 (permalink) Old 09-12-2018, 11:49 AM Thread Starter
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Went to the dealership to look over the car and inspect the brake issue.

THey pretty much echoed what we thought, I used new pads with old rotors (rotors are near the end of their life)
And that typically causes some noise, but they couldn't really figure out why the pads are moving around so much.

They have a vertical movement to them and they are just shake rattlin and rollin around in there, and it's getting really annoying. Like at any speed they're rattling loudly. THey were even doing it at 70mph on the ride from the dealership, so them moving them around seems to have made it even worse.
They couldn't tell if it was the pins moving around in the calipers, or the pads moving around on the pins. I can tell you that I greased everything like I was supposed to, but I kinda wish I had just left it nice and rusty. It probably wouldn't be bouncing around right now.


So I can get new rotors, which I probably need anyway, and maybe the pads will wear in a groove into the rotor and hold the pad in place vertically, but it seems odd that the pads have so much movement.
Any thoughts??
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post #16 of 21 (permalink) Old 09-13-2018, 05:51 PM Thread Starter
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bumping this up , still looking for some input
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post #17 of 21 (permalink) Old 09-14-2018, 03:48 AM
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Hows your hub in that corner. I always get the worst rattling in the FR and I always have my FR hub fail first, I was just thinking they might be related?

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post #18 of 21 (permalink) Old 09-14-2018, 06:50 AM Thread Starter
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Hows your hub in that corner. I always get the worst rattling in the FR and I always have my FR hub fail first, I was just thinking they might be related?
You would hope the dealership would have noticed something like that. It doesn't sound like a wheel bearing. It's deff a noise linked to brakes as applying the brakes stops the noise 100% of the time.

Also after driving the car through torrential rains to get it to the dealer (A real treat on worn R888Rs ). I think the grease is starting to come off because the noise at least initially seems to be getting better.
Pads are grabbing better too, compared to the track day, so surprisingly they still might be getting bedded in completely. My old set of RC5+s never grabbed like this, I can't even heel toe the car right now because they're so grabby.
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post #19 of 21 (permalink) Old 09-14-2018, 07:24 AM
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Hey bro, I was the one riding shotgun in my buddys twin turbo 350 on the rally. Trying to remember if you said you had recently changed out the lines to stainless as well. Just thinking you may have shook some air bubbles out of the abs module as well. If the pressure in the lines wasn't holding the pistons may have backed off enough to allow some vibrating in the pads. Have you re-bled the brakes since the rally?
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post #20 of 21 (permalink) Old 09-14-2018, 08:35 AM
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I had some issues with uneven transfer way back, when I was using Pagids. This would cause a rasping noise and vibration that could be felt in the pedal. I heard and felt this when on the brakes though. I now use PFCs. They are very forgiving when it comes to switching and bedding.

I understand that uneven transfer occurs commonly if pad type is changed and rotor is not changed, but it can occur with a like for like pads change. Once the uneven transfer occurs, the rotors are done, the hot spots change the surface.

The AP 2-pots do have an anti-rattle strip on the bottom of the pad slot opening. Are those still there?

I only track my car and religiously never get any grease anywhere near the pads. I think this is only trouble.

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