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Jerky braking at slow speeds - Ride/Handling/Suspension/Brakes/Wheels/Tyres - The Lotus Forums Jump to content
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Jerky braking at slow speeds

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Do any of you guys experience an undulating sensation when gently braking at very low speeds? Like when coming to soft and gentle stop at a stop light.

When I get ready to stop at a light, I'll apply the brakes then go into neutral as the revs go down. I let the car coast with soft pressure applied to the brakes to try and come to a smooth stop.

This is when I get the undulating sensation. It's almost like the pedal is being pumped and the brakes are grabbing on/off as the car rolls.

Or imagine the car coasting on a road with lateral grooves running across (tiny speed bumps). It feels like that.

The car rides and brakes fine otherwise. It's only at slow speeds that I feel it.

Is this just the nature low profile tires?

Stiff chassis just picking up the slightest irregularities of the road?

When I feel the jerky motion and then let off the brakes, the ride becomes smooth again.

Don't feel anything through my foot when on the pedals. No vibrations.

I will bug the dealer about it when it's time to bring her in, but I thought I'd post this and see if anyone has had a similar experience.

Thanks!

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Has the car been on track? Handbrake used between sessions?

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This sounds like what I get on my Esprit. It's done it since I got it 10 years ago and only goes after the discs are changed or reground, and then only for about 12 months

The car does not get used anywhere near hard enough to be "warped" but that's what it feels like through the brake pedal.

When it gets really bad it starts to make a grindin "wub-wub" noise too and I feel it through the steering wheel, which is the sign it needs attention.

No-one else has ever mentioned the same problem, and I assumed it may have been a "feature" of the (fairly crappy) Brembo brakes. However I was a passenger in a Sport 350 once which looked like it was suffering more than mine (driver didn't seem bothered) and they have APs obviously.

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It'll be high/low spots on the (probably) front discs. Normally due to wear, very occasionally a result of poor disc fitting procedure leaving muck on the mating face. If they are slightly warped and not too worn, you could get them skimmed, but it's better to replace them.

To assess whether it's the rears, slow to a stop using handbrake only.

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Brother's Jag had a similar problem, very slight run out, less than 1 mm, local Subaru dealer had a piece of kit that ' ground ' them in situ on the car, £100 for fronts

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Indeed, and insitu is the best way. But if you're springing for that you might as well go for new ones.

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I had this exact problem sometimes with my LE, that was solved by either:

a: a cleaning of the brakes by my dealer

b: a couple of hard brakings on a spirited drive.

But if I spent a couple of weeks driving it in town only, the problem would come back.

She just wants to be driven fast :rambo:

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What do you mean by "insitu?"

I think it's the front rotors that's causing the issue, but it's difficult to tell. I tried stopping with the parking brake and I want to say it felt smoother, but I'm not 100% sure.

I will have the dealer take a look when it's time to bring her in.

Thanks everyone!

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In situ, on the car, ie, jacked front end, removed wheels and lowered car onto the grinding machine one side at a time, took an hour or so. My bro was pleased with the results because he had recently replaced the discs because of run out ( Jag dealer supplied) . For the trade to have a piece of kit makes you wonder if there are quality control problems with whole batches of discs being borderline for run- out

Just googled this

http://www.skimmydiscs.co.uk/index.php

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Mine does it a bit, too. Just kind of got used to it - the brakes work brilliantly, so never been concerned. Always thought it was th tyres to be honest.

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Mine too.

I have had the rotors checked and apparently they are fine. Generally some good hard stops make the issue go away for a while - suspect I'm too light on the pedal!

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This definitely sounds like you have excess pad material on your rotors and they need to be cleaned a little. Usually use 80 grit paper running from hub straight to the outside of the rotor on the fronts all the way around.  As others have said before here: Stopping a few times from 60MPH to 0 should do the tricks sometimes (depending how much materials was deposited).  Anyone buying a new vehicle should bed in the pads to the rotors to prevent this from happening.

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I had the same problem. Bob Fogle, noticing that I yank the hand-brake pretty hard, suggested I might have been overdoing it and thus warping a rotor. But between using the hand-brake more lightly and pushing the brakes hard at Sebring, the problem pretty much disappeared. 

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There no way on Earth the handbrake being pulled hard would warp a disc. You just cleared material build up on the discs on your trackday.

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Yeah, that's what I figured too. Just blew whatever gunk there was off the rotors and/or pads. It's still noticeable, but nothing like it was.

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In situ, on the car, ie, jacked front end, removed wheels and lowered car onto the grinding machine one side at a time, took an hour or so. My bro was pleased with the results because he had recently replaced the discs because of run out ( Jag dealer supplied) . For the trade to have a piece of kit makes you wonder if there are quality control problems with whole batches of discs being borderline for run- outJust googled this

http://www.skimmydiscs.co.uk/index.php

I've once again got a pulsating brake peddle.. Not too bad on the road but will be very annoying on the three Trackdays I've got booked this summer. Front disks only had 10,000 miles, rears have had 21,000 miles. Pads apparently 80% on front 90% rear. Most of my driving on A-Roads and motorways with very little town driving.

What am I doing wrong? I drive normally, haven't tracked it since the problem. Occasionally when the disks are warm do a 60 to 0 hard brake to clean them but still a wobble and vibration!

Spoken to a few specialists and come up with two options:-

1. Disks off and taken away to be ground down to a perfect flat finish. This will cost £500 for all 4. Also a pain as the car will be away for two days and the garage doesn't have any courtesy cars.

2. From Skimmydisks.co.uk using ProCut in situ £240 for all four. A friend with an M3 had this done and swears by it..

Am tempted to just try doing the rears as the front disks were replaced by my dealer last year and the steering wheel doesn't vibrate.

Any advice much appreciated :-)

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The Service Notes recommend that the discs aren't skimmed but are replaced. They also have disc 'run-out' figures which your dealer can check and if required, replace them. 

 

The run-out will also show if the disc is correctly mounted true on the hub etc, worth pursuing that avenue first but as mentioned, avoid having them skimmed.

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My Esprit is almost unbearable for this at the moment, but too skint to do anything for a while. And guess what? The family Volvo has started doing it 3 months and 3000 miles after a set of genuine replacement pads/discs.

 

What is it with braking hardware these days?

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Car booked in tomorrow morning on your advice Bibs ;-) hopefully an alignment issue. It's bearable but will be exaggerated at my first track outing of the season. Hate that vibration when your concentrating on a corner :-(

It's very annoying as my cars brakes whilst strong are frustrating.

Any other Evora owners getting this pulsing at slow speed and vibration at high speeds when braking?

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