mx5-kiwi

Looking for some sensible advice please.

89 NA has what I think is the original Goodwin Big Brake kit on the front (Willwood Calipers, 11" discs (need to check that size though)) and 1600 calipers on a large disc with a Flying Miata Adaptor.....

Running full race pads.

I may be just being silly but I find the pedal a little soft and it has a lot of travel under hard braking in track day/race situations.

I could just learn to accept it but it leaves me with a constant feeling of unease that they have faded / overheated etc....they don't overheat or fade but the do feel a bit like they have or are about too....15-20 minute sessions at competitive lap times.

They are great in that the modulation etc is easy and feel fine on the road.

But I think I would prefer are slightly harder feel and slightly less travel.....

Questions are,

- Should I just accept it, it is fine.
- this is common and you can do .xxxx to help.
- this isn't common and it is VERY expensive to change.....thsi is what you do xxx

MR.M!474

iTrader: (5)

When was the last time that you bled the brakes?
Did you bleed your brake fluid in the correct order?
Do you have the stock rubber lines or SS lines?

I had this problem too and it turned out to be my old gunky brake fluid which would start to boil after doing hard braking. Flush your brake fluid and bleed it in the RR,RL,FR,FL order..i believe that's the order.

As an additional upgrade you should replace your stock rubber lines with 949 racing SS lines.

mx5-kiwi

Cheers but the car has full braided lines. Brake kit, suspension, engine came from one of our top, succesfull race cars (well in MX5's anyway), which was parted out mostly to me.

Bleeding might help but it feels pretty much the same as it did at the last track day when everything was fresh (fluid and bled).

Problem is I have approx 80-100 hp more now (via the engine swap) and the performance and feel is a bit more important than it was.....

MR.M!474

iTrader: (5)

It definitely sounds like boiling fluid though. If it feels fine when driving normal but gets soft when driving hard for a prolonged period of time i would think your issue is the brake fluid...especially if the car is still braking hard.

What fluid are u using?

hustler

iTrader: (6)

You have a turbo car, why aren't you running TSE brakes? They are god.

MR.M!474

iTrader: (5)

Only thing left for you to do really is to add more rotor and pad for better heat capacity. Sell your old set up to help pay for the new one. Idk what 1600 brakes are unless you mean the stock 1.6l calipers? id suggest upgrading them to sport brakes or better if u go with the TSE front BBK. Properly ducting air to the caliper/rotor cant hurt either.

TSE BBK is on my to do list, cant wait to see what everyone is raving about.

mr_hyde

iTrader: (4)

I think the 1600 refers to stock rears with brackets for larger disks. What booster/master cylinder are you running? If it is the original '90, going to the 15/16th should help the pedal.

1993ka24det

What are the weight difference between stock rotor and the 2 piece that TSE/FM has?

Carbon Ceramic brakes ;-) I wish

hustler

iTrader: (6)

Imagine Angela Merkel dressed as Hildegard of the SS holding you in bandage, forcing you to modernize Nietzsche's Gay Science while her Germany Shepard laps boiling-hot Nutella off your ***** (for your sins) ... every time you step on the pedal.

hustler

iTrader: (6)

Significant improvement as well.

Savington

iTrader: (31)

It's not "the 2 piece that TSE/FM has". Our 2-piece rotor is not shared with any other kit.

MR.M!474

iTrader: (5)

...I..I don't know what to say. You've brought tears to my eyes, thank you.

hustler

iTrader: (6)

Did it out the pear in your birnbrot?

MR.M!474

iTrader: (5)

Hustler, sometimes I really do wish I could understand what you are saying.

mx5-kiwi

Thanks for the replies.

Yes stock MC and booster on Goodwin big brake kit (willwood 4 pot) with 11.00" rotors and stock 1600 calipers on FM adaptor brackets to a 10.75" disc. Oh and they have TSE brake Prawns with 2.5" ducting from the front spoiler.

Despite Hustlers hustling of the TSE kit (I DO appreciate the advice and believe me would LOVE that kit!!) Going to the 15/16th MC is an upgrade for my current kit then...?

What is this likely to do...firmer pedal or less travel or both?

Leafy

iTrader: (1)

Kiwi, if you double tap the brakes is the 2nd hit of the pedal a lot firmer and with shorter travel? I mean, before you go to stop if you hit the brakes to the engagement point, let off then hit them again, is the pedal shorter? You could just be getting pad kickback because the rotors/hubs/spindles have some runout. Which is a much bigger issues on fixed rotor fixed caliper brakes than it is on brakes with floating rotors or calipers.

z31maniac

Both. Larger bore pushes more fluid (also makes it higher effort).

shanem

iTrader: (1)

i had a similar issue on the brakes of my previous car, have you tried a different brake fluid. i know most people like motul or the blue stuff whos name escapes me right now or the wilwood stuff that comes with those kits. i had problems with the pedal feel changing as the brakes heated.

they werent fading, just the pedal would engage lower as laps went by and things heated up. i read up and saw that some of the porsche cup drivers had that issue (they called it comressability IIRC) and went to endless brake fluid or brembo lcf 600+. since that brembo stuff is not that expensive at ~$20 per 500ml i went with it. no more problems with the pedal compressing when hot after that and activating lower. i run it in my miata too with decent results. that siad, i am on stock brakes and running ~5 seconds under spec miata record and there is a huge difference in how stock brakes perform within a windows of a 2:04 (3 seconds under SM record) to a 2:02 (5 seconds under) at my track.

at 2:04, the stock brakes are being taxed, but ok, at 2:02 i didnt think i would make a few corners, not that i slowed down. i just had exceptionally high sphincter tone for a few corners.

I ordered the Fm 4 wheel kit, hustler promptly chastised me for not going with the TSE kit. idk, all 4 wheels for the same money sounded good at the time. i figure it will be hugely better than stock so ill not know the difference.

mx5-kiwi

Just to confirm, brake does not pump up and it doesn't change (very little if any) as it gets hot.

Just that a long and soft'ish (but very standard feeling) pedal for road driving is not that confidence inspiring slowing down from 200km/h.

Absolutely no problem from 50-80km/h.

Just to confirm brake feel is very standard I just think a bit firmer and less travel would be a little less concerning at higher speeds. Probably me just being finicky.......or not enough experience.

Anyway, thank you for the suggestions, will also look at a different fluid.

Sounds like the 15/16th MC is the answer, Is this a direct bolt on?

Savington

iTrader: (31)

It sounds like you have air in the master cylinder.