Pulsing brakes...

The Oily Bits S1 Specific Topics
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Fellow Exigers,I’ve thinking this one out of the only trackday that I’ve done so far, and decided to get your opinions.My car’s brakes before the track day, after and on the first lap were feeling normal, but once warm, during hard braking they always felt “pulsing”, almost like a slightly warped rotor(s). [image]http://www.exiges.com/ubb/NonCGI/images/icons/confused.gif[/image]When they cool down they feel normal, only using them hard on the track it felt like this.Have somebody ever felt this? My car still has the normal brake lines, I want to change them to SS lines. Would I feel this effect increased?Cheers,Uldis

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UldisSounds like your rotors are slightly warped -may be cured by skimming them. Don’t forgot to NOT apply the handbrake, or sit in the car with your foot on the brake when returning to the paddock after a session on track!With regards the SS brakelines, this is really a must do, along with SRF fluid, then as soon as possble change the pads to either Mintex or the best option, Pagids.

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My brake pedal provides a smooth feel when the brakes are cold, after a couple of laps the pedal will pulse (quite violently) if you apply a gentle pressure, but that goes away if you brake hard… Go figure.

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Pesky, skimming the rotors even if while cold or moderate use the problem doesn’t appear? it seems to me that yes, they’re warping, but under heat only and going back to true as they cool moderately.The SS lines and fluid I’ll do soon, but SRF: is that the brand? type? DOT 4, 5, 5.1?And don’t worry, at rest the car stays only in gear and I barely touch the brakes when coming back.Admin5, could it be that you have some play somewhere? something worn down there? Thanks.

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One of the probs at I had at Knockhill was when coming off for a red flag when someone spun on the track and moving back into the pit-lane, waiting to go back out. The pitlane exit is on a slight decline so I couldn’t stop meself moving forward without the brakes. Obviously I didn’t want to use the brakes as they’d still be very hot. Tried to put some steering lock on for rolling resistance, to no avail, so had to end up having to pull off to the side which was flatter. Don’t know what everyone else was doing. Really could do with some remote control chocks. [image]http://www.exiges.com/ubb/NonCGI/images/icons/wink.gif[/image]Flat pit-lanes please.

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How about leaving it in gear?Cheers

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With the engine running? [image]http://www.exiges.com/ubb/NonCGI/images/icons/wink.gif[/image]Was third from the front of a long queue so had to be ready to go when the green came on again plus often if I switch my engine off when hot, it has a habit of playing funny boogers, like idling at 3,000rpms.

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Leaving it in gear is good, though a bit of a pain. I’ve seen lots of people using chocks (aka sandbags)

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I once saw somebody leave it in gear - and then decided to switch the engine back on by leaning in the window. Cue new clam and minor damage to the car in front.Cheers

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Not quite so damaging, but how many people have leaned into the car to start it, only to realise you’ve left your windscreen wipers on, and it wipes the contents of the wet screen onto you ? (or is it just me that happens to ?)

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I had a similar problem earlier this year. Go here for my original posting: http://www.exiges.com/ubb/NonCGI/Forum1/HTML/000775.html It turns out that it was faulty manufacture (but note comments on hot pads on hot discs while stationary).Are your discs clean or could you have a simiar problem?Mike

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quote:Originally posted by Admin5:Not quite so damaging, but how many people have leaned into the car to start it, only to realise you’ve left your windscreen wipers on, and it wipes the contents of the wet screen onto you ? (or is it just me that happens to ?)Most definately not just you!I seem to catch the wiper nearly every time I get out and get wet as you describe when I lean in to start it in the morning! [image]http://www.exiges.com/ubb/NonCGI/images/icons/frown.gif[/image]Ian [image]http://www.exiges.com/ubb/NonCGI/images/icons/smile.gif[/image]

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Uldis - sounds similar to the problem I experienced - see:- http://www.exiges.com/ubb/NonCGI/Forum2/HTML/000057.html Cheers, Tim

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I wonder… if you could make something out of a pushbike brake caliper that just clamped onto the driveshaft. Then you could have the car stopped with the engine running and not have to use the wheel brakes.Hmmmm Bri

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Timbo,thatt’s it, that’s exactly may problem.And I was searching for this subject and couldn’t find it !So, I only need to change the pads for it to go away. I thought that I had bed them in properly but it seems that I really overcooked them.Seems not to be so critical, so I will see how much I wear them at Knockhill on Wednesday (whole day, remember? [image]http://www.exiges.com/ubb/NonCGI/images/icons/grin.gif[/image] ) and change whatever I need to change after that.I mean, the car still stops, right?Uldis

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My brakes have always ‘pulsed’ a bit when hot. A few month ago, I got a couple of demo laps round Donington with a Lutus test driver. I could actually feel the pulsing from the passenger seat, so I asked him if it was normal. He told me it’s perfecty normal for cross drilled brakes to do that when really hot. It’s something to do with slightly uneven expansion due to the holes.

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Makes sense, because these brakes are solid, one piece and still cross drilled. The only comparison point I have are the (cast iron) ones I used while racing bikes, but they were fully floaters (cast iron part separate from the aluminum center).I have seen some of these in eliseparts (they call the steel MMC, not cast iron) but the only guy that I have seen had them in an Elise that KH track day (a guy called Tut), broke them (shattered), so he was not very impressed (and neither am I).Just curious, does anybody know if there are other serious fully floating discs around?Cheers,Uldis

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Uldis - I fear you may be a tad confused about the various disks you have seen.The disks you get from Eliseparts are an aluminium bell with a steel disk. These are not MMCs.MMCs (Metal Matrix Compound) were specified on early standard Elises, until the supplier folded and it was not possible to obtain an economical replacement. They are not up to the job of constant pounding around a circuit on a heavily modified car. On a standard car for road use they are fantastic, until it gets wet.Cheers

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Ok, thanks for the correction.Then it means that the ones Tut broke were the steel disks with aluminum bell. Not very good design then? or are they also known to fatigue and the best would be the plain old cast iron (original on the Exige)?Cheers,Uldis

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quote:Originally posted by Uldis:…the ones Tut broke were the steel disks with aluminum bell.HE GOT METAL DISKS TO SHATTER!!!Which bit went, bell or disk? What was he doing?!