Brake judder after brake fluid top-up, then all fine?

  1. My model of MX-5 is: __NC 2.0
  2. I’m based near: __London
  3. I’m looking for technical help or recommendations on: __brake judder

3 weeks ago I had the pads, lines replaced, fluid changed for dot 5.1. Since then periodically handbrake warning light on. I thought it was an electrical glitch, then realised it’s also the light for low brake fluid level. I checked the level, was 1/3 towards minimum. I topped up to about 2/3, using dot 4 as I didn’t have any other. This was during track day.

Next few laps, bad brake judder. Steering wheel and brake pedal vibrated a lot under braking. I pulled in, waited 30 mins, issue was gone. No judder for the rest of the day.

All explanations for brake judder I found point to issues which wouldn’t ordinarily solve itself (like distorted discs etc). Any ideas?

Where had the brake fluid gone? Worked past the caliper piston seals and contaminated the disc causing slip-stick between the pads and disc maybe?

Maybe. I guess the car needs to go back to the garage to have this checked?

By the way when the garage changed the fluid I made the mistake of not checking the level. The light was on pretty much since then. So maybe they just didn’t put enough fluid in.

The coincidence of me topping up fluid and judder starting that very moment is a bit odd.

Did you bed in the pads properly before your track day and what pads did you have fitted?

Yes I did bed them in properly; I used Roddisons

When you came off track did you cool the brakes on your final lap by not using them? Did you put the hand brake on when back in the paddock and leave it on? Did you sit with your foot on the brake pedal for any time when you stopped? Just a few reasons that may have resulted in you warping your discs.

Thanks all for help. Warped discs due to not doing the cool down lap is probably the issue here.

Some say …

Discs don’t warp. They just pick up uneven amounts of pad material around and across their surface, which gives the impression of the discs being warped. The pick up happens more when the brakes are hot and used hard. Some or all of the pick it can be removed when the brakes are used when cooler.

This sort of ties in with what you suffered.

Also, bear in mind that standard Roddisons pads will wear quickly on the track, causing your brake fluid level to drop.

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