juddering brakes

[SoManyCarsSuchLittleTime]

I have a 2018 A110 Legende - just done 15K miles

I have done a few trackdays this summer and noticed a juddering from the steering wheel under hard braking

I have taken the wheels off and checked the discs to see if they are warped (using a Dial Test Indicator) but this only showed a possible deflection of about 5/100ths of a mm which was more likely caused by me pushing the disc to rotate it

so I replaced the front pads (as they take the most wear and the juddering was coming up the steering wheel)

while there does not seem to be any juddering under normal road conditions, the next track day they seemed to reappear

does anyone have any similar experiences or cures

thanks Nick

[worldwidewebs]

It's pad transfer - the standard discs are notorious for it.

[SoManyCarsSuchLittleTime]

thanks for your speedy reply

please explain "pad transfer" - it is not a term I am aware of

[Simon Owen]

I had this in Spain this year.

My understanding is brake judder is caused by an uneven buildup of pad material on the friction surface of the disc.

Not done anything yet but assume upgraded pads would fix it, possibly discs too I dunno ?

Not great really, considering my occurrence was purely on the road not track (fast road to be fair).

[7en]

Apparently if they sit for a while the pads will leave residue on the discs and the longer the car is left the worse it will be, to the point they'll even weld themselves on.

[worldwidewebs]

SoManyCarsSuchLittleTime said:

thanks for your speedy reply

please explain "pad transfer" - it is not a term I am aware of

Probably a more accurate description would be uneven pad transfer. When the discs/pads gets hot, the pads can transfer some of their friction material to the pad. But rather than the normal/expected consistent 'micro-film' (my term) across the whole surface of the disc it can be thicker and in patches. It's this that causes the judder and is often what is really happening when people talk about warped discs, which in fact rarely happen.

The standard Alpine discs are fine for most usage but on track, when they get hot, they will often suffer from the above problem. I don't know what causes it, maybe it's a relatively low iron content in the disc, but it is well known. The rear discs actually do very little braking so I wouldn't worry too much about them bar fitting some better pads but on the front I'd look to replace the discs and pads. I'm happily running Tarox discs on track (and road) - they are relatively cheap at £350 a pair, work well, but are quite heavy. There are other, better, options out there but the price can go up quite sharply. Speak with Life110, MP Rezeau for starters

[SoManyCarsSuchLittleTime]

Thanks to all my learned friends for your knowledge and advice - much appreciated!

As the pads and discs had been on the car for 13k miles before this occurred when I did the track days I am assuming this must have happened when the car was standing after the sessions

Unfortunately these modern cars automatically engage the handbrake when they are stopped which I guess, from what has been said, is when the transfer of pad deposits has occurred

I have subsequently worked out a “dance” that leaves the car in gear but without the handbrake on when the engine is switched off which will hopefully prevent this happening again - as long as I remember the dance

1. Switch car off with the Start/Stop button
2. Do not put your foot on the footbrake
3. Switch car on with the Start/Stop button - engine does not start
4. Press the handbrake button while pressing the footbrake - handbrake is released and light goes out on the handbrake button - Apply Handbrake warning appears on the dashboard
5. Gently Rock the car to check the gears are engaged

Now all I need is to remove the deposits which is difficult as I think the car also stops you putting a foot on the brake and the accelerator at the same time

Any thoughts?

[timbo999]

Its worth doing a couple of cool down laps after a session on track. It can be difficult to go slow enough not to need the brakes especially on an open pit lane day. In these I usually come off track and do a few laps of the paddock car park - which can be just as difficult depending where you are - at Brands I go through the tunnel and circulate in the bigger car park. Probably teaching you to suck eggs but worth mentioning.

[Whaleblue]

Some interesting and useful posts here.

Re applying braking and acceleration simultaneously, I’d be surprised if the car stops it from happening as that would stop heel and toe work (for those talented enough to usefully apply). However, no idea if it’s a good/safe idea here, nor whether it would help?

Edited by Whaleblue on Wednesday 20th December 16:38

[Liam22]

SoManyCarsSuchLittleTime said:

I have subsequently worked out a “dance” that leaves the car in gear but without the handbrake on

It's a lot simpler to depress the handbrake button while turning the engine off.

[s111dpc]

SoManyCarsSuchLittleTime said:

Thanks to all my learned friends for your knowledge and advice - much appreciated!

As the pads and discs had been on the car for 13k miles before this occurred when I did the track days I am assuming this must have happened when the car was standing after the sessions

Unfortunately these modern cars automatically engage the handbrake when they are stopped which I guess, from what has been said, is when the transfer of pad deposits has occurred

I have subsequently worked out a “dance” that leaves the car in gear but without the handbrake on when the engine is switched off which will hopefully prevent this happening again - as long as I remember the dance

1. Switch car off with the Start/Stop button
2. Do not put your foot on the footbrake
3. Switch car on with the Start/Stop button - engine does not start
4. Press the handbrake button while pressing the footbrake - handbrake is released and light goes out on the handbrake button - Apply Handbrake warning appears on the dashboard
5. Gently Rock the car to check the gears are engaged

Now all I need is to remove the deposits which is difficult as I think the car also stops you putting a foot on the brake and the accelerator at the same time

Any thoughts?

On the ‘dance’ you can also just turn the car off by holding the handbrake button down as you push the stop button - this doesn’t apply the handbrake but will leave the car in Park

[SoManyCarsSuchLittleTime]

Thanks @Liam22 and @s111dpc

I was never very good at dancing - or reading the manual for that matter

[Julian Thompson]

That’s good to know, is it possible to switch it off in neutral with the handbrake off too? (For ramp positioning etc)

[worldwidewebs]

Julian Thompson said:

That’s good to know, is it possible to switch it off in neutral with the handbrake off too? (For ramp positioning etc)

It is.

With the engine off, ignition on, doors closed and gearbox in position (P), it is possible to switch to position (N) by a short press on the N switch while simultaneously depressing the brake pedal (the N switch integrated indicator light appears in white and N is displayed on the instrument panel).
(N) position may be engaged before the driver’s door is opened and for a maximum of around 45 seconds after the engine has stopped. After this time or after opening the driver’s door, it will be necessary to turn on the ignition again to disengage position (P).

Taken from the manual
https://e-guide.alpinecars.com/eng/Alpine-A110/AUT...

[s111dpc]

Julian Thompson said:

That’s good to know, is it possible to switch it off in neutral with the handbrake off too? (For ramp positioning etc)

That’s how I park it in my garage, the procedure I use is:

1) turn off the engine by holding the handbrake button down then push Start/Stop switch - this doesn’t set the handbrake.
2) push start button but do not put foot on brake - this switches the ignition on
3) put foot on brake and then press N button - this takes the car out of Park and into Neutral
4) push stop button again to turn off ignition (without any other inputs i.e. no foot on brake etc)

This allows the car to be pushed if required - obviously only suitable for level ground