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Discussion Starter #1
I have a brake issue which I am working to improve by changing again the brake pad (actual Pagid RS4-2, changing for something better, I don't know yet), changing the weight of the disc (actual: stock, changing for 295-28 Alcon), and of course add new brake hose (actual: stock, changing for stainless type). I am using already Motul DOT4 600 brake oil, and I am changing it like every lapping day. I am not smouth with my brake. I am using my Elise on street and lapping day, but driving at race speed during lapping.

But, it still for me a big question about one very strange thing happening on my car, and maybe the cause can be somethinbg else, including the ABS.

During lapping, the pedal start to be more and more spongy, caused probably by heat, and fade of the pad. The worst case of the spongy pedal is all time when I am returning to the track after a car cool down, and the cool down time can be as high as 45 minutes, no matter. Typically I need to pump the brake to be back with a working pedal, go to the track, after first corner, I restart pumping the brake and after I am ok to start with a better pedal.

At the beginning, I was thinking that I did not let enough cool down before to return to the pit. My feeling was maybe the heat is going to the caliper oil when the car is stopped. Saturday, I was doing a 2 lap cool down to see if the cool down should be the cause. No changes, the pedal was spongy a lot.

I don't understand the cause. I raced many years without that kind of trouble on my other car, not equipped with ABS. My brother saw the same king of pedal issue with a Austin Martin DB7, equipped with an ABS.

Is it possible that for any reason, the ABS is doing something on the brake circuit. At the moment, I have tendency to think about a hydraulic issue more than the heating issue to explain a spongy pedal after a long cool down.

So, anybody else with this trouble?

If the ABS is the cause, I will remove it.

Any input will be appreciated.
 

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Marc,
It's been my experience that Elise/Exiges don't usually have brake fade issues unless they are driven very hard on track with the "factory fill" brake fluid which is garbage.
With the upgrades that you have listed you should not be seeing brake fade.
I would suggest that you pressure bleed the system thoughly again because it seems that you might still have some air trapped in the ABS system.
I know first hand that if you get air in the line (especially the front curcuit) it is very hard to purge it, at least doing it the old fashion way of one man pumping the pedal while you crack the bleed valve. Get youself pressure bleeder that connects on the master cylinder end if you don't already have one and push a liter or so through the system. That should do the trick.:up:
 

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change to Superblue with a real good bleed job and you'll be amazed by the difference.
 

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I run ATE Super Blue in my S1 and it's good stuff but so is the Mutol 600 that Marc is using.
One very good practice is to switch between ATE Blue and a standard gold colored fluid so that when flushing the system you know when the old fluid is fully flushed by the color of the fluid coming out of the caliper. :D
 

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Please confirm that you aren't setting the parking brake when you come off the track.

If you're really hard on the brakes (and/or let the pad material get too thin to absorb the heat), it is possible to overheat the brakes, but it will be obvious, just from looking at the rotors, if that's what's happening.

But you've got to be really, really hard on the brakes to get there for that to happen.

Since you've already changed the fluid, I'm seconding a full flush with a pressure bleeder to be sure there's no air in the system and extablish a good known baseline to start from for further troubleshooting.
 

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I alternate with superblue and superblue ( gold )
 

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Kestrel,
I think you mean ATE Type 200. :D
 

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Discussion Starter #8
Thanks everyone.

Like I said on my first message, I am changing the brake oil every lapping day, and typically, I am putting back one full bottle (500 ml) every time, and using a guy into the car pumping the brake. In regard of be certain that it is no air into the system, I don't think that I can do a better job than that.

And yes, the parking brake is not used, of course not.

Regarding the brake disc, they are just nicely blue... and the center is perfectly rusted, teh zinc plated was just not able to take the heat... I am very hard with the car, but the result is typically I am faster than all car on the track, M3, M5, 911 turbo, Elise with 290 hp.

To clarify about what I call spongy, during session, the pedal can move down by maybe 3/4, but when I am taking back the car, after a long cool down in the pit, the pedal travel can be maybe around the double. I need to be in the track to reach again a better pedal. This can happens with new and half old brake pad.

Yestersday I took time to look how the ABS is working, and it is few valves, with valves going to a oil accumulator. Maybe the dump valve leaks, or air trapped into thes ABS. Is it bleed fitting into the ABS body?

I still have hesitation to remove the ABS, in some zones, I know it is better without, but I know some places where I know it is better with (typically, bumpy tight S curve with breaking into the S with the car completely unbalance, where I am faster with the Elise than with my racing car... (without ABS)).

Any idea, me I don't know.
 

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I vote air in the system. Despite your confidence that you've avoided it, I think there is a bubble in there somewhere.

You should have it done at a good dealer once, so they can use a pressure bleeder and, more importantly, they can cycle the ABS with the Lotus scan tool during the process.

xtn
 

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Discussion Starter #10
xtn,

If the cause is only air, after cool down, the pedal should be less spongy since the air bubble temperature is lower for smaller volume. And when running, the pedal should be more and more spongy.

In this case, it is not what is happening. This is why I devided the problem in two, spongy during running, and different and higher pedal gap after long cool down.

For me it is strange, and I have big trouble to explain it just by the air bubble.

Regards
 

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Perhaps the bubble is in the ABS unit, where the greater mass (relative to just the brake line) causes the heat-up and cool-down cycle to take longer than one would think.

I don't know, but I would not rule out the bubble completely. Get it flushed by a tech with the Lotus scan tool and see what happens.

xtn
 

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And yes, the parking brake is not used, of course not.
Just making sure - a friend loaned his Viper to an pro driver with no worries, only to find that the pro came back in off the track and set the parking brake. Unfortunately, the friend didn't put everything together until he was in the weeds.
 

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Just making sure - a friend loaned his Viper to an pro driver with no worries, only to find that the pro came back in off the track and set the parking brake. Unfortunately, the friend didn't put everything together until he was in the weeds.
Ouch. Nobody told him he's supposed to take the Pbrake off before he begins his next session?

It's so cute the way you act like you have other friends....-poke-

xtn
 

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Ouch. Nobody told him he's supposed to take the Pbrake off before he begins his next session?

It's so cute the way you act like you have other friends....-poke-

xtn
Yeah, I know... he took the brake off, but due to the calipers (like ours), the fluid in the rear circuit was cooked.

No names, but the Viper guy owns a local race track.
;)
 

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Hey it looks like I'm going to be all alone for the week surrounding christmas. My family is going away to visit... well... more of it's family. You wanna go out and get drunk a large number of times during that week?
 

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I dont know if its possible on the lotus' but I have had this problem in other cars and found that the ABS is hard on the fluid and can break it down easily and when I ran the cars without the ABS, the problem went away. On a couple cars, it was a matter of removing a fuse. On the Ferrari 360, I couldnt be disconnected. I havent had any brake fade in the cup car so I havent looked into it on it.
 

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Ive had air in the ABS...complete a bleed. Then slam on the brakes to get the ABS working and bleed again. Got the air out.

PITA
 

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IIRC:

Pump brake pedal up with car stopped, assuming it comes up.

Continue pressure on pedal.

If pedal sinks, it's air in lines.

If pedal doesn't sink, it came up in step 1 due to worn pads.
 
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