NA Miata doesn't like stopping

My sister's 93 Auto is a fun little car, as long as you don't need to stop. The calipers were recently rebuilt, new Wagner thermo quiet pads.

I'm wondering if I'm just used to more modern brakes, and maybe they were never that good to begin with, or if something is wrong. Is there any swaps/upgrades that would work for a daily driver? Brakes are a pretty significant safety feature, so I'd like them to work, and work well.

what fluid was used and was it rebled after caliper replacement?

I haven't personally driven a 1.6 car with stock brakes that made me feel confident. Non-performance parts store pads wouldn't help, either.

drummerfromdefleopard wrote: what fluid was used and was it rebled after caliper replacement?

no idea the brand, but yes it was bled. feel free to surprise me, but I doubt the brand of fluid would take it from 10% to 100%.

Swank Force One wrote: I haven't personally driven a 1.6 car with stock brakes that made me feel confident. Non-performance parts store pads wouldn't help, either.

That's what I figured. Performance pads im sure would help, but its not exactly the economical solution.

brand wouldn't but proper DOT rating for the car and flushing the system to not mix different DOT rating of fluid can contribute, though normally not when freshly performed, unless there's still massive air bubbles in the lines from inadequate bleeding.

lnlogauge wrote:

drummerfromdefleopard wrote: what fluid was used and was it rebled after caliper replacement?

no idea the brand, but yes it was bled. feel free to surprise me, but I doubt the brand of fluid would take it from 10% to 100%.

Swank Force One wrote: I haven't personally driven a 1.6 car with stock brakes that made me feel confident. Non-performance parts store pads wouldn't help, either.

That's what I figured. Performance pads im sure would help, but its not exactly the economical solution.

I don't remember if they're available in 1.6 fitment, but the Stoptech Street Performance pads on Rockauto are pretty damn cheap, and quite good actually.

Fluid isn't going to make a difference unless you're concerned about heat resistance or a mushy pedal. Mixing DOT ratings won't make any difference to pedal feel with the exception of having DOT5 in there somewhere.

For most people, "good" brakes are ones that provide a high level of retardation for a given pedal pressure. It's all about pad aggressiveness, rotor size and amount of boost. The 1.6 Miata doesn't have a lot of the last two. If you want the over-servoed feel of most modern cars, the way to do that is with a set of pads that have a lot of bite.

Now, you say you want a brake swap but simply buying a good set of pads "isn't the economical solution". So I'm taking that to say that you're looking for something that costs less than $83.95, which is what a set of Porterfield R4S pads would run. Not much in the way of brake swaps in that range.

My suggestion would be to bed the pads. It's probably never been done, and that can make a big difference.

If you stomp on the pedal can you get all 4 wheels to lock up? If so, brakes are working normally. Want to stop faster? Step harder.

Now, on the other hand, if you can get the pedal to the floor and the tires aren't squealing, then there is another problem.

Either throw on 1.8 caliper brackets, pads and rotors on or a more aggressive pad. Ive got rockautos powerstop performance pads on the rear of mine (1.6) and hawk hps on the front (1.8) and it stops much better than anything else I drive

What is the actual problem?

Pedal mushy, going to floor? (leak, air in system, bad master)

Pedal hard and not stopping? (brake booster or vacuum source bad)

Pedal feels fine, but car not slowing a proper rate (E36 M3ty or non-bedded pads)

Cone_Junkie wrote: Pedal feels fine, but car not slowing a proper rate (E36 M3ty or non-bedded pads)

Or E36 M3 12 year old Falken Azenis 215s on the front - its what I deserved waiting on 200TW toyos. Running Hawk HPS on the back and Napa pads on the front. Still was locking the fronts, but couldn't get any smoke out of them :)

Tires stop the car, not brakes.

But brakes can fail to make full use of the tires. Tires are simply the ultimate limitation.

Keith Tanner wrote: But brakes can fail to make full use of the tires. Tires are simply the ultimate limitation.

I know, I just like being a wise guy.

In reply to rcutclif:

I stomped on them, and the tires didn't come close to squealing.

Maybe I'm misguided, but I thought performance pads were very limited use. If 84 bucks fixes the problem, that's awesome. I just don't want to spend 84.00 every few months. I am curious about the 1.8 swap. Is it just the calipers/rotors? Same master cylinder?

Yeah, same master cylinder with the 1.8 brakes. All you need is the rotors and the brackets to fit your 1.6 calipers to the bigger 1.8 rotors.

Miatas don't way a lot and in general, even high performance pads last quite a while. I've had HP+ on my last Miata that survived close to two years with some semi-daily driving and the odd trackday. The bigger question is if your sister can live with the dust most high performance pads create?

lnlogauge wrote: In reply to rcutclif: I stomped on them, and the tires didn't come close to squealing.

Then stop right here. No more talk of performance anything or 1.8 calipers, etc. You have a serious problem somewhere.

Does the pedal go all the way to the floor of the car? If so, there is likely air in the system and re bleeding will fix it. If not, your brake lines might be blocked somewhere.

In reply to rcutclif:

My vote would be on the "rebuilt" calipers either not being rebuilt properly or not installed properly.

I'd pull the wheels off and check the calipers to make sure they are sliding properly and the pistons are moving okay.

If not, then move up the system to verify fluid is flowing through the lines and that the master cylinder is working.

Question: we're the rotors replaced as well? Were they cleaned before installation? Sometimes residue is left on the rotors that should be cleaned off.

lnlogauge wrote: ...new Wagner thermo quiet pads.

Those pads were never particularly good at actually stopping cars.

With good pads, rotors unscored, and the rest in good shape, a Miata will stop on a dime and give change.

So yea, replace those junkie pads with something good, make sure the rotors are actually smooth, and it should stop quite well.

Did you adjust the rear calipers by removing the 14mm cap bolt on the back and using the allen key to adjust rear pad spacing?

I thought the 1.6 Miata brakes were perfectly adequate for a stock vehicle. I did have some 'good' summer only tires on it. I have no idea what pads I put on it, honestly.

Any idea if the rubber brake lines were ever replaced? Remember that they're now 22 years old at best, and they do eventually swell and block. A set of stainless might be all that it takes to fix it.

In reply to WonkoTheSane:

That's a good idea. I'll add new lines to the list. The car has new Rotors as well, so that shouldn't be the problem. I'll start with the Porterfield pads with new lines, and see how it goes. or stops.

With the car running (not moving), if you put FIRM pressure on the brake pedal, does it slowly start to sink further?

My thoughts are it needs a rebleed or the master cylinder is one its way out.

Double check that the sliders are free (I know you stated that they were just rebuilt, but they could freeze quickly over a winter, especially if not greased generously with the right stuff), Miatas love to freeze up and you could only be using one pad of two on each caliper. I had to replace both rears on mine, the sliders were so locked that putting them in a vice and sledghammering them wouldnt budge them. Car felt 1000x better after fixing that.

Second that the thermoquiet pads aren't going to feel the grabbiest.

Check those soft lines, do a re-bleed while you are at it.