Titanium brake shims.

[GreenV8S]

The Wookie said:

CL pads do generally run quite hot

Surely the pad temperature is determined by the power being absorbed by the brakes and the available cooling. Different pads are able to keep working effectively at different temperatures, but I've never heard of a pad causing higher temperatures for a given driving situation.

[stevieturbo]

GreenV8S said:

Surely the pad temperature is determined by the power being absorbed by the brakes and the available cooling. Different pads are able to keep working effectively at different temperatures, but I've never heard of a pad causing higher temperatures for a given driving situation.

As said, mixing the wrong pads with the wrong disc material can cause excessive wear and heat.

It's not quite as simple as brakes off or on and every application will result in the same heat/wear/energy etc.

All parts need patched together for the application.

[GreenV8S]

stevieturbo said:

As said, mixing the wrong pads with the wrong disc material can cause excessive wear and heat.

Excessive *heat*?

Every pad / disc combination is 100% efficient at converting kinetic energy to heat. How do you think the choice of material alters that?

[The Wookie]

GreenV8S said:

Surely the pad temperature is determined by the power being absorbed by the brakes and the available cooling. Different pads are able to keep working effectively at different temperatures, but I've never heard of a pad causing higher temperatures for a given driving situation.

Brakes are very dynamic and the energy has different routes of rejection, I’m pretty sure we usually see high surface temps or at least big thermal gradients on CL pads.

Personally pad compound behaviour has never been my area so I might be talking bks but the only thing I’ve seen first hand is back to back tests on a WRC tests where paint tell-tales and disc life as limited by cracking indicated high disc cheek temps while running a set route compared to a couple of other compounds.

[stevieturbo]

GreenV8S said:

Excessive *heat*?

Every pad / disc combination is 100% efficient at converting kinetic energy to heat. How do you think the choice of material alters that?

Do you think all discs are the same ? Would make some race discs utterly pointless if cheaper materials could be used ?
Likewise pads ?
And how those materials deal with or disperse any heat....

Wow...you just wiped out the entire braking industry with one fell swoop when one everything fits all.

[xjay1337]

stevieturbo said:

Do you think all discs are the same ? Would make some race discs utterly pointless if cheaper materials could be used ?
Likewise pads ?
And how those materials deal with or disperse any heat....

Wow...you just wiped out the entire braking industry with one fell swoop when one everything fits all.

To be fair no discs (assuming same size and construction type) improve braking performance or heat transfer . All you can ask for is a good base material so expansion under heat is consistent.

Never understand why people want to pay 400 quid for some discs when the 200 ones will do the same.

[The Wookie]

xjay1337 said:

To be fair no discs (assuming same size and construction type) improve braking performance or heat transfer . All you can ask for is a good base material so expansion under heat is consistent.

Never understand why people want to pay 400 quid for some discs when the 200 ones will do the same.

Because good quality discs usually have better tolerances and treatment so they end up being a more consistent and resilient base for expansion.

[xjay1337]

The Wookie said:

Because good quality discs usually have better tolerances and treatment so they end up being a more consistent and resilient base for expansion.

Sort of what I said - but most good discs are generally of equal quality.

For me I find Mtec work really well and they're cheap.

[stevieturbo]

xjay1337 said:

To be fair no discs (assuming same size and construction type) improve braking performance or heat transfer . All you can ask for is a good base material so expansion under heat is consistent.

Never understand why people want to pay 400 quid for some discs when the 200 ones will do the same.

yet you've totally contradicted yourself.

All discs are not of the same construction type, or materials, or designs. Just the same as all pads are not the same type, materials or designs.

Even if to some people they look the same.

A bit like this F40 replica looking the same as an F40....they must be exactly the same then ?

https://www.youtube.com/watch?v=oWSFXOwrg3Q

[stevieturbo]

Although unrelated to this application, this was quite interesting....but hell, they also look the same so must be the same as every other brakes out there. Porsche must be doing some dumb st when cheaper stuff that looks the same would work the same.

https://www.youtube.com/watch?v=ZCj83_uF9dE

[LimSlip]

GreenV8S said:

Excessive *heat*?

Every pad / disc combination is 100% efficient at converting kinetic energy to heat. How do you think the choice of material alters that?

You are correct, exactly the same total amount of heat is generated irrespective of pads or discs. However the thermal conductivity of the pad material itself varies, which can end up with more heat being transferred into the caliper pistons.

[xjay1337]

stevieturbo said:

yet you've totally contradicted yourself.

All discs are not of the same construction type, or materials, or designs. Just the same as all pads are not the same type, materials or designs.

Even if to some people they look the same.

A bit like this F40 replica looking the same as an F40....they must be exactly the same then ?

https://www.youtube.com/watch?v=oWSFXOwrg3Q

If you take for example Pagid discs and Brembo discs (from Euros so "oem equivalent" there is not going to be any real world difference.

I find it stupid people want to buy silly "race discs" for £400 when there are plenty of decent discs on the market for, for example, £200.

My particular car OEM discs are around £230 or M-tec ones are £160. Only one of them warped after 1 trackday the other handled 6 full days with only minor surface cracking :-)

Tarox do some but they're around £330 from what other owners tell me the durability between the Mtec and Tarrox are identical, in some cases actually the Mtec is better (for my specific application).

All of them are made of iron at the end of the day and most of the "premium" discs are going to be a near enough equal quality.

Like sure a Dacia isn't the same quality as a BMW but then the difference between an Audi and BMW and Mercedes is perhaps so small ......

I'm not stupid enough to think that your £30 "motorist discount center" disc is going to be the same metallurgically as the Tarrox for example but for most people especially on the road then the £30 one will be absolutely fine and those who purely "upgrade" to incredibly expensive discs without looking at better pads, new/fresh fluid, better cooling or better calipers are wasting their money. Lots of people are like "oh yeah I got these really fancy Tarrox discs....."
Cool, what pads I ask
"Just OEM ones mate they're amazing".
Me : laugh:

In Fact even on my cheap stty daily I have decent pads but the cheapest brake discs available from ECP and that's been fine for nearly 3 years...!

Sure different grades of iron and different heat treatments and perhaps internal vane designs on a vented disc but again once you are over the "budget" range then most are going to be fairly equal.

A funny story some OEM VW/Audi brakes are designed poorly so both discs have directional vanes but only one side is correct and the other is effectively mounted backwards :-) So even big brand OEM manufactures can get it wrong.

[GreenV8S]

LimSlip said:

You are correct, exactly the same total amount of heat is generated irrespective of pads or discs. However the thermal conductivity of the pad material itself varies, which can end up with more heat being transferred into the caliper pistons.

The pad thermal conductivity (together with any backing plates and shims) is really the only thing I can see making any difference here. I wouldn't expect to find a huge difference in thermal conductivity between pad brands/types, and what difference there was would surely be swamped by variations in pad thickness due to wear. The idea that some pad/disc brand/type combinations inherently generate more heat than others seems a bit of a stretch to me.

[stevieturbo]

xjay1337 said:

If you take for example Pagid discs and Brembo discs (from Euros so "oem equivalent" there is not going to be any real world difference.

I find it stupid people want to buy silly "race discs" for £400 when there are plenty of decent discs on the market for, for example, £200.

My particular car OEM discs are around £230 or M-tec ones are £160. Only one of them warped after 1 trackday the other handled 6 full days with only minor surface cracking :-)

Tarox do some but they're around £330 from what other owners tell me the durability between the Mtec and Tarrox are identical, in some cases actually the Mtec is better (for my specific application).

All of them are made of iron at the end of the day and most of the "premium" discs are going to be a near enough equal quality.

Like sure a Dacia isn't the same quality as a BMW but then the difference between an Audi and BMW and Mercedes is perhaps so small ......

I'm not stupid enough to think that your £30 "motorist discount center" disc is going to be the same metallurgically as the Tarrox for example but for most people especially on the road then the £30 one will be absolutely fine and those who purely "upgrade" to incredibly expensive discs without looking at better pads, new/fresh fluid, better cooling or better calipers are wasting their money. Lots of people are like "oh yeah I got these really fancy Tarrox discs....."
Cool, what pads I ask
"Just OEM ones mate they're amazing".
Me : laugh:

In Fact even on my cheap stty daily I have decent pads but the cheapest brake discs available from ECP and that's been fine for nearly 3 years...!

Sure different grades of iron and different heat treatments and perhaps internal vane designs on a vented disc but again once you are over the "budget" range then most are going to be fairly equal.

A funny story some OEM VW/Audi brakes are designed poorly so both discs have directional vanes but only one side is correct and the other is effectively mounted backwards :-) So even big brand OEM manufactures can get it wrong.

You're showing yourself to be rather naive if you think a a Euro "OEM Equivalent" is the same quality as an actual OEM part.

And you can be sure the OEM tested those brakes you may feel are the wrong way round....and I'm sure they worked fine for the application, and saved the expensive of 2 different discs for those who thinks all discs are the same to get wrong.

[stevieturbo]

GreenV8S said:

The pad thermal conductivity (together with any backing plates and shims) is really the only thing I can see making any difference here. I wouldn't expect to find a huge difference in thermal conductivity between pad brands/types, and what difference there was would surely be swamped by variations in pad thickness due to wear. The idea that some pad/disc brand/type combinations inherently generate more heat than others seems a bit of a stretch to me.

yet as the porsche link above....it is very true.

Or the use of carbon brakes, or simply better materials. If you use a very aggressive pad, it will eat the ste out of a crap disc...which has endured more friction than necessary, more heat generated, more wear...simply through incompatible parts.

[LimSlip]

stevieturbo said:

yet as the porsche link above....it is very true.

Or the use of carbon brakes, or simply better materials. If you use a very aggressive pad, it will eat the ste out of a crap disc...which has endured more friction than necessary, more heat generated, more wear...simply through incompatible parts.

It's not true. Brakes convert kinetic energy into thermal energy, a conversion which is 100% efficient. The amount of energy that needs to be converted can easily be calculated from KE=0.5mv^2, the brake materials and construction play no part in this value. If a pad/disc combination has a higher level of friction, then it requires less clamping force applied for the same rate of braking but it does not produce any more heat energy. If you could extract more than 100% of the kinetic energy as heat, the world's energy problems would be over.

Where brake materials and design makes a difference is how well this heat is dissipated, i.e. directing the bulk of it into the disc (and then into the air) is obviously preferable to having it conducted through the pads and back into the caliper.

[GreenV8S]

stevieturbo said:

Or the use of carbon brakes, or simply better materials. If you use a very aggressive pad, it will eat the ste out of a crap disc...which has endured more friction than necessary, more heat generated, more wear...simply through incompatible parts.

Wear, certainly. But the amount of energy going into the brakes is unchanged and the only differences in temperatures surely are just due to variations in pad conductivity, which are unlikely to vary hugely for the sort of pads in question and in any case would be insignificant compared to variations in pad thickness. I am simply not convinced that pad/disc brand/type combinations are relevant to this problem.

[xjay1337]

stevieturbo said:

You're showing yourself to be rather naive if you think a a Euro "OEM Equivalent" is the same quality as an actual OEM part.

And you can be sure the OEM tested those brakes you may feel are the wrong way round....and I'm sure they worked fine for the application, and saved the expensive of 2 different discs for those who thinks all discs are the same to get wrong.

Two words. Audi Ttrs.

But it's ok. Guess I'm naive then :/

I know when a debate is pointless. I'll bow out to your superior knowledge.

Edited by xjay1337 on Monday 22 June 21:29

[The Wookie]

xjay1337 said:

Two words. Audi Ttrs.

But it's ok. Guess I'm naive then :/

I know when a debate is pointless. I'll bow out to your superior knowledge.

Edited by xjay1337 on Monday 22 June 21:29

The brake discs on the TTRS are a proprietary semi-floating technology which is owned exclusively by one 2nd tier supplier, the 1st tier brake supplier only has control/responsibility over the specification and design. Therefore any disc of the same design that has that technology comes from the same factory.

That's rarely the case for single piece brake discs and even obscure detail differences between disc design and manufacturing processes can result in annoying NVH problems.

If you do the research and find one of the OEM's that was an original supplier for the vehicle then you're drastically improving your chances of getting something which is the identical specification which was signed off during the original vehicle development process. Often other OEM stuff will be fine but it's never a guarantee.

[The Wookie]

The Wookie said:

GreenV8S said:

Surely the pad temperature is determined by the power being absorbed by the brakes and the available cooling. Different pads are able to keep working effectively at different temperatures, but I've never heard of a pad causing higher temperatures for a given driving situation.

Brakes are very dynamic and the energy has different routes of rejection, I’m pretty sure we usually see high surface temps or at least big thermal gradients on CL pads.

Personally pad compound behaviour has never been my area so I might be talking bks but the only thing I’ve seen first hand is back to back tests on a WRC tests where paint tell-tales and disc life as limited by cracking indicated high disc cheek temps while running a set route compared to a couple of other compounds.

Just had half an hour so I did a bit of digging in our reservoir of test data. I was getting a bit confused, the behaviour I've observed in CL pads is that they produce a high thermal gradient across the face of the disc (i.e. thermal banding) not through the cheek.

On dyno testing, stabilised disc bulk temperatures tend to be relatively consistent between different friction materials but from the data I've looked at there are significant differences in pad bulk temps between compounds, indicating that pad thermal conductivity is very relevant.

My interpretation is it compound choice might have little effect on disc bulk temperature but it will have a significant effect on piston/caliper/fluid temps and probably peak in-stop surface temps to an extent.

Edited by The Wookie on Tuesday 23 June 12:36