Understanding how brakes work (for dummies like me)

davekmoore · Postby **davekmoore** » Sun May 22, 2016 10:37 pm

Thought others might also find this useful:

http://www.stoptech.com/technical-suppo ... ther-myths

The pedal feel is perfect but BARMY seems to leap from side to side when the brake pedal is pressed hard and/or for longer than a dab. As well as not stopping the car very much, the front brakes also groan like a Groany Thing and it's no longer just driver error or lack of skill that causes me to miss apexes (Jeez, sounding like an proper quick driver here :oops:

, which I am NOT!).

Based on this article it seems my continuing to expect too much from non-quite-race pads, and overheating them, has now caused enough random transfer of pad material onto the rotors to cause all the symptoms above.

Hopefully Brakes Direct, QFM, and now a 3rd party who is blamed for delays by both the first 2, will finally get the race pads to me PDQ.

tumble · Postby **tumble** » Mon May 23, 2016 12:11 am

That URL's truncated. Did you mean it to be this?

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

davekmoore · Postby **davekmoore** » Mon May 23, 2016 12:24 am

http://www.stoptech.com/technical-suppo ... ther-myths

davekmoore · Postby **davekmoore** » Mon May 23, 2016 12:26 am

Or copy and paste this into an interweb search:

The "Warped" Brake Disc and Other Myths of the Braking System

Dan · Postby **Dan** » Mon May 23, 2016 1:27 am

I had an issue about a year ago from not breaking in a set of race pads properly which caused me to run through them in just a few days when they should have lasted for many more, I also felt similar vibration issues to what were described in the article. I've had 2 sets of the same pads since then with no issues so I definitely think the advice in this article is good and I wish I had of followed the correct break in procedure like the article advocates!

Saying that I think you might have a bigger issue on your car if it's leaping side to side as that's more likely to be caused by something other than uneven pad wear (brake bias, suspension or driver are more likely).

If you re-read the article you'll notice makes no reference at all to that as a symptom so you might not want to use it as a basis to attribute your issue of the car leaping from side to side under brakes to it.

The other issue of it not stopping in time could definitely be from the pads or the break in procedure though.

Sent from my SM-N9005 using Tapatalk

Magpie · Postby **Magpie** » Mon May 23, 2016 5:45 am

Are the slider pins moving freely?

Brake fluid, when was it last changed?

What pads are you going to?

Tires, are they in decent condition?

Remember tires are what makes you stop, a lot of my recent brake issues were tire related.

ManiacLachy · Postby **ManiacLachy** » Mon May 23, 2016 7:27 am

Here you go:
http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

Magpie · Postby **Magpie** » Mon May 23, 2016 8:13 am

Have a read of this as well http://www.miataturbo.net/general-miata-chat-9/anyone-have-any-brake-questions-81577/#post1177465

If you think that it is from a build up of material then get them machined or replaced, alternatively use a more aggressive pad. Whatever you do bed in your new pads as per the directions.

However be aware of the pads temperature range and not push them past this point. The rotors main purpose is to dissipate heat as well as give the brake pads something to grip to, if either gets too hot you will have issues. Further, the heat from the pads/rotors will also heat up your brake fluid (2nd law of thermodynamics - heat flows spontaneously from a hot to a cold body). It would appear that the overarching issue is heat management.

JBT · Postby **JBT** » Mon May 23, 2016 8:16 am

Excellent articles. This is my issue using QFM HPX on the track: "When the temperature at the interface between the pad and the rotor exceeds the thermal capacity of the pad, the pad loses friction capability due largely to out gassing of the binding agents in the pad compound. The brake pedal remains firm and solid but the car will not stop. The first indication is a distinctive and unpleasant smell..." They are great street pads but caused a lot of "missed apexes" at track day.

Never had this problem with OEM or Remsa pads. Only drawback for me with Remsa is the duuuust.

Postby **beavis** » Mon May 23, 2016 10:20 am

davekmoore wrote:http://www.stoptech.com/technical-suppo ... ther-myths

you need to paste the link then put the URL [ URL] link [/URL ] tags around it before you submit or preview.

davekmoore · Postby **davekmoore** » Mon May 23, 2016 3:06 pm

Magpie wrote:Have a read of this as well http://www.miataturbo.net/general-miata-chat-9/anyone-have-any-brake-questions-81577/#post1177465

If you think that it is from a build up of material then get them machined or replaced, alternatively use a more aggressive pad. Whatever you do bed in your new pads as per the directions.

However be aware of the pads temperature range and not push them past this point. The rotors main purpose is to dissipate heat as well as give the brake pads something to grip to, if either gets too hot you will have issues. Further, the heat from the pads/rotors will also heat up your brake fluid (2nd law of thermodynamics - heat flows spontaneously from a hot to a cold body). It would appear that the overarching issue is heat management.

Pads with higher heat range going in soon. The existing rotors will be skimmed and the (new) spares put in, plus a very careful and complete bedding in. Never any issues with the pedal going soft so I reckon the fluid is ok, and it was changed recently.

Magpie, the pads will be "QFM A1RM which are rated to 780°C/1436°F and equivalent to something like Ferodo D2500 or Project Mu HC+". The combination of the car and my driving has previously overheated pads rated to 800°F and 1000°F. Tyres were pretty new NT01s.

Dan, the build up of pad material will have been from the pads overheating. Suspension is all good, albeit presently setup for sharper turn in than previously. Recently aligned and corner weighted. I don't do anything as a driver to make it steer randomly left and right and in my head it's saying high/hot spots on the rotors are causing one side to brake harder than the other on then off and the overall imperfect coating of pad material on the rotor is causing the general reduction in stopping power. All fine on the road by the way, as the track temps simply don't happen.

travis · Postby **travis** » Mon May 23, 2016 3:13 pm

Not that I've seen it here, nor have I intentionally checked, but I'm amazed when viewing in other forums at the amount of instances where the words "break" and "brake" are used incorrectly.

Maybe it's the mechanical engineer inside that's taking notice

..and goes to show we MX5 owners are just a class above

Great articles, thanks for sharing.

ManiacLachy · Postby **ManiacLachy** » Mon May 23, 2016 3:30 pm

travis wrote:Not that I've seen it here, nor have I intentionally checked, but I'm amazed when viewing in other forums at the amount of instances where the words "break" and "brake" are used incorrectly.

Maybe it's the mechanical engineer inside that's taking notice
..and goes to show we MX5 owners are just a class above

Great articles, thanks for sharing.

For your own sake, don't go on the Facebook groups, it'll brake ( :mrgreen:

) your heart!

Magpie · Postby **Magpie** » Mon May 23, 2016 4:54 pm

800°c rotor temperature is very concerning. I don't think the A1RM's were rated that high, not too many pads are.

I run Winmax 6.5's and they are good to 800°c and 3's on the rear and these are good for 600°c.

On the front the temps have never got above 430° and the callipers have not exceeded 204°. When the rear callipers were dragging I did see in excess of 630°, however this situation has been rectified.

I would be looking at other issues as to rotor temps. How did you measure them? The temps you are looking at suggests dragging. If you track your car a lot then you should inspect your callipers more often, especially the sliders and are the rear brakes releasing correctly.

This is the actual testing I did http://mx5cartalk.com/forum/viewtopic.php?p=844355#p844355

Also this is the difference to braking that tires can make.

1:01.6 lap AD08's (Purple F brake pressure, Flesh speed)
1:03.1 lap FZ201's (green F brake pressure, aqua speed)

It needs no real explanation... The AD08's allowed a braking to be later and develop more of it not to mention more speed into the turn. The only change to the car on was tires...