Better Braking.

[dmad_dood]

Over the past year or so i've slowly been trying to get my brakes up to scratch and i'm almost there. When i bought my car the brakes were "useless" and thats quite optimistic. The rotors were ground down to a pulp, very rusty and i'm also assuming the pads were contaminated. I started off with rotors and pads. I bought brand new oem rotors at a great price and bought some hawk hps pads front and rear for $100 delivered Swapped everything over and bedded everything in and hmmm very average brakes still.. The fronts were working ok but the bias was completely out, touch the peddle and the fronts would just lock. Better but not great. Over the next week or so they slowly got better but wasn't anywhere near scratch so back to the drawing board. I though that it would probably be a good idea to change out my old fluid (which i probably should of started with). Bought myself some good quality dot 4 and flushed all the old fluid out. Thought i could get away with doing it myself but after 2 hours of gravity feeding i was getting no where so i recruited my dads foot and within 20min brakes were nice and solid with a little less travel and a little less sponge. I started with the front drivers side calliper then passenger front and so on... when bleeding the rear drivers side i found a bit of air in the calliper which i thought might of contributed to shocking bias but then i did the rear passenger side and oh dear.. There was literally no fluid in the calliper. After 10 pumps opening and closing the bleed nipple nothing came out

After i got my car back together and took it for a drive it was obvious that the rear pads weren't even scrubbed in and now the car is pulling up a lot better. I still find that the braking isn't that great but its not dangerous anymore. I still find if i punch the brakes the fronts will lock very easily so i'm suspecting that bias is still any issue. Any ideas how to fix this or does anyone else have this problem.

Im also not sold on my pads, through winter they were very average. Being street pads they should work from the first stop but defiantly need 2 or 3 good stops to start working properly, so i think next time i will be changing from hawk hps's, for spirited driving there pretty good when they get hot.

Over the weekend with the good weather i embarked on the mission of improving braking once again (albiet only cosmetic). I was sick of looking at my ugly brown and greasy, rusty callipers and rotors and for the price of $10.00 and a bit of elbow grease and time i thought hey, it could only be better then what i've got and in the spirit of my putting the order through for my news wheels, i thought it was a good time to get the car up to scratch.

Im not going to go through all the details but basically i jacked my car up under 4 jack stands took all my wheels up, taped up the braking surfaces on my rotors, sanded back all the rust with 240 wet and dry and doused in brake cleaner before i took to the spray can.



I only needed one can of 500˚c calliper and rotor paint and that was plenty enough to do 3-4 coats per corner including calliper and rotor. For $10.00 im very happy with the results and has very subtly transformed the car into not a pile of c**p



Haven't been here around much lately and thought this was a good excuse to do a little write up. When my wheels arrive ill put some more photos up of the whole car.

(P.S the final product looks a lot better with all that overspray gone)

Jono.

[timk]

I like how you painted your brake pads to match the caliper!

I'm amazed at how much pads make a difference hey!

[itrungs]

I'm running QFM pads and DBA rotors and I would recommend everyone else to try them. Not too sure about how they stack up against the top pads out there, but I would think that the QFM pads are right up there.

[Mr Morlock]

Not sure what model your car is - but I have not had any problem with brake performance in an NBp2 and the car is also very light on brakes- pads have lasted a very long time and still going- light progressive and effective. Rotors can be machined in fact should be machined every time the pads are replaced. I recently did the front brakes on my daily car- big rotors and pad replacement and the machining cost $44- they will not machine if undersize.

To clean brakes you use brake cleaner not fluid and don't brush or blow dust off. Your brakes should not be locking up under normal conditions- if there is no abs and you stab and hold or just hold the foot down you would expect it to lock up. Workshop manuals always give instructions on brake servicing and repairs. You brakes might need a pro to look at them if you are still getting lock up.

[dmad_dood]

Rotors and pads are brand new and ive got an na8. I also cleaned with brake cleaner and bled with brake fluid. The brakes aren't really the problem its just my grip under braking which is puzzling as i'm running good tyres at correct pressures aswell.

[Magpie]

Have you fully inspected the calipers? Slider pins sliding, pistons no leaks?

When you changed the rears how did you get the pads out?

What tyres and what pressures?

Is one side locking up when braking in a straight line?

If the brakes are OEM then a bias controller will be installed. There is a very strong front bias, at least for the NA models. It is possible to install a manual bias controller, but unless you know what you are doing setting it up is dangerous. To get more rear bias you can fit a more agressive pad.

Since my car does very little street driving it has entry level race pads, winmax W5/W3 combination and when they are cold they are difficult to predict, they need in excess of 100 deg c to become effective. At full operating temp they are brilliant!

My suggestion would be to have all 4 calipers overhauled.

[zossy1]

NA8s have too much front bias from the factory. There is nothing you can do about this other than either go with a NB8B brake bracket/rotor upgrade to the rear (though this could give too much rear bias, depending on pad choice), or install an adjustable prop valve.

All NA and NB MX5s have a tendency to lock the front passenger's side brake first under straight line braking. It is fairly hard to cure this issue as it is related to weight transfer and if you are a fatass like me, it's even worse. Corner weighting can help but this is not really possible without adjustable suspension and access to corner weighting scales.

[davekmoore]

Having ABS also sort of solves the issue of the bias to the front left as just after the car starts turning gently left the ABS comes in and straightens things back up!

[93_Clubman]

I started with the front drivers side calliper then passenger front and so on... when bleeding the rear drivers side i found a bit of air in the calliper which i thought might of contributed to shocking bias but then i did the rear passenger side and oh dear.. There was literally no fluid in the calliper. After 10 pumps opening and closing the bleed nipple nothing came out

Both the Rod's MX5 Enthusiast's Shop Manual & the Haynes MX5 Repair Manual say that you should start bleeding at the caliper furthest away from the brake master cylinder, then the next furthest, then the next furthest again, finishing on the closest to the brake master cylinder.

[davekmoore]

My mate who's a Mazda tech also started with the one furthest away today. Emptied the master cylinder first. All worked out fine. Used up quite a lot of expensive brake fluid, but worth it to get rid of the 300 and get mostly 600 in.

[davekmoore]

Better brakes.jpg

Click to enlarge if you like brake porn!
Remember to add decent brake fluid and bear in mind the hats will give you a wider track so if you have wide wheels you may need to roll and/or pull the guards.
15x8 +25s on mine will need a roll and they only just cleared the calipers, and then only after the balance weights were removed.

[MattR]

You know you can quite easily "overbrake" a car.

Does a 1000kg or so car really need 6 spot calipers that are from a near 2000kg car????

Whilst pretty and they stop a heavy car well you are adding unsprung weight compared to a 4 spot caliper from the same manufacturuer in the same material.

Personally, I use the smallest brakes possible that will do the job. On the new race car build, I am only upgrading from S14 brakes to Z32 alloy 4 spot brakes on the front and R33 2 spots on the rear as that's all a 1100kg car will need for a 300km race around QR. Other advantage is that they are cheap to buy, $350 for the 4 calipers and rotors, and pads are cheap and easy to get $300 for a full set from Hawk in the US of A

[dmad_dood]

To clarify im very sure theres nothing wrong with the callipers or the pads or the rotors or the brake fluid or when i changed the pads over making sure i wound off the handbrake to pull the rear pads out. Its just locking up the fronts way before the rear (the rears have never locked up). It might be worth re-bleeding but as all of you are saying, na8s do suffer from poor braking bias so im not sure the bleed is the issue. Does anyone no the science behind bleeding the furthest calliper first?

If it is a bias issue shouldn't everyone be having the same problem? Maybe it just bugs me more then everyone else? Or could it be suspension set up limiting grip under braking?

[MattR]

A lot of cars will only the fronts and if you can get the rears to lock you have done well I drive a variety of cars and demonstrate emergency braking as part of some part time driver training I do. One of the cars we use without ABS will not lock the rears unless I pull on the hand brake, another car locks the rears after some effort and a third car will lock all four wheels almost simultaneously.

Suspension can help or hinder depending on how old and type, whether it is standard with a lot of km or brand new and set up for the car. Also tyres can have a huge effect. How old are the tyres, what pressures are you running and what is the general condition of the tyres?

But with your dramas, I would be looking at the brakes. As had been said before, when you replaced the pads did you also replace the grease on the slider pins? What condition were the pins in when you did the swap? What did the piston seals look like on the calipers? What was the general condition of the calipers?

What does the pedal feel like? When you lock the fronts first how are you using the brakes? Are you smashing the pedal as hard as you can under heavy braking?

And for bleeding from the furthest point first, it is to maximise the amount of air you get out of the braking system. Sometimes you may need to bleed the brakes a few times doing it by pumping the pedal. If you have the time, gravity is best, or if you have the pressure bleeder that is better again if used correctly.

[manga_blue]

The NA8 bias valve is a bit weak to the rears but you still should be getting some useful braking from them, not necessarily to lock-up though. Mazda probably valved them that way so you couldn't lock rears.

If it were my car I'd be taking the calipers off, fully dismantling, cleaning, inspecting and reassembling them with new seals and new main slider pins. They're about 20 years old, how long do you expect rubber to last??? Then I'd bleed them in order of distance from the master: LR, RR, LF, RF