GR Yaris Thoughts on aftermarket discs and calipers choice

991RS

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Oct 17, 2023
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while bigger hardware typically increases unsprung weight and can do real damage to your wallet.
😀
It won't increases unsprung weight in my case, I might decrease the disc weight a little bit compare to girodiscs which are already 2kg lighter than OEM.
And I would decrease by 100g the weight of the caliper compare to OEM but that's going to be cancelled by customs brackets I guess.

The wallet part is 100% true indeed ! 😅
 

991RS

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Again the question is what temps do you have.
Your brake fluid will boil at approx 300°C, while the pads can take 800°C. So if the pads are at their limit, then you need bigger ones/6 pot. But if it's just the brake fluid, then shims are your friend.
Well...I guess I should buy some temp stickers, but the temp was enough to get the girodiscs red on a 2°C day.
As seen on my video here
 
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Onehp

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Well...I guess I should buy some temp stickers, but the temp was enough to get the girodiscs red on a 2°C day.
As seen on my video here
Steel will start to glow at ~460C, and if anything is an indicator you need more brake disk cooling, bigger calipers won't help at all in that!
 

Duke

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Well...I guess I should buy some temp stickers, but the temp was enough to get the girodiscs red on a 2°C day.
As seen on my video here
That’s seems excessive. I don’t think I’ve ever seen Yaris discs glow like that, not on track, not at the bottom of a Alpine pass, so you were either really on it, they are dragging a bit, or those discs are somehow prone to overheating?

We all like a reduction in unsprung mass, but if that is simply a reduction in the mass available to absorb heat without properly considered additional cooling to compensate then maybe that’s the result.

Not saying anything specifically about Girodiscs though, I have no experience with them, just spitballin’ 🙂
 

991RS

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Steel will start to glow at ~460C, and if anything is an indicator you need more brake disk cooling, bigger calipers won't help at all in that!
But a bigger and a thicker disc will, hence a bigger caliper
 

991RS

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That’s seems excessive. I don’t think I’ve ever seen Yaris discs glow like that, not on track, not at the bottom of a Alpine pass, so you were either really on it, they are dragging a bit, or those discs are somehow prone to overheating?
I really try to push the brake pedal at the last moment and very hard. Like a grizzly could tramble his prey :LOL: Do you picture it ? seems accurate
Then trailbrake into the corner of course.
 

991RS

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We all like a reduction in unsprung mass, but if that is simply a reduction in the mass available to absorb heat without properly considered additional cooling to compensate then maybe that’s the result.
Yes, less mass = less capacity to absorb heat (considering same size and thickness discs)
"the amount of heat required to raise the temperature of a substance is directly proportional to its mass. "
Indeed additional cooling should be considered when installing lighter disc, that's an interesting point.

The real question is does a lighter but better disc outcome his disadvantage in (less) mass by vents/material compare to OEM
I hope yes, because we all buy aftermarket discs thinking they will run cooler than OEM
In my case I will go for a bigger diameter and a thicker disc...so that's a good point too for heat management.
 
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Onehp

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Yes, less mass = less capacity to absorb heat (considering same size and thickness discs)
"the amount of heat required to raise the temperature of a substance is directly proportional to its mass. "
Indeed additional cooling should be considered when installing lighter disc, that's an interesting point.

The real question is does a lighter but better disc outcome his disadvantage in (less) mass by vents/material compare to OEM
I hope yes, because we all buy aftermarket discs thinking they will run cooler than OEM
In my case I will go for a bigger diameter and a thicker disc...so that's a good point too for heat management.
Thicker usually means wider cooling channels, that does benefit significantly, as does increase diameter.

Still first step is to have cooling air to the root of the brake disk...
 

MRA3

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Dec 29, 2021
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I think, no one on here mentioned the actual braking technique, there may be some improvement also on that?
 

991RS

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So AP racing 6 pistons calipers and AP racing discs installed yesterday.
I might do my next trackday next weekend but so far :

1) The caliper is really more of an open design than the OEM caliper, so better for heat management
2) Lighter too.
3) antiknockback springs are welcome even if I don't feel that I had the issue of a space between the pistons and the pads before
4) Different pistons size inside the caliper are welcome too (small to big)
5) Pad change even easier than OEM caliper
6) Pad so much cheaper than OEM shape.
+/- 500€ for RSL1 for my new calipers whereas +/-850€ for Endless MA45B
If you track the car a lot this is good.
7) As temperatures are going to be much lower, pad life is increased a lot, so even better for the wallet
My MA45B didn't last a long time because of the heat I guess.
8) RSL1 pads available for AP racing calipers, not for OEM shape.
9) no more dust boots ✊ :)

2 very small drawbacks :
1) Caliper doesn't clear OEM wheel but a 3 or 4mm thick spacer will fix this issue
2) OMG so much noise from the pads moving inside the caliper ! CLANK CLONK ! Like the car is broken :LOL:
This is due to the pad being very free to move inside the caliper.

I am not sure yet about the brake balance (too much at the front now ?) during my bedding procedure everything was fine but after I used the brake from higher speed and the rear MAY BE danced a little but I am not so sure about this. I will know next weekend.
 
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991RS

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Did you go got the cp9660 calipers and cp5772 362mm discs then? How are you getting on?
Yes.

After some more use of this kit I can confirm the brake balance still very good, I have no issue braking hard.
This weekend at the nurburgring : best lap 8:12 BTG with one yellow flag. Pace is 8:01 BTG ( this is "optimal lap" in racechrono app).
Using external GPS antenna.

Also I can confirm to anybody who wish to do the same : Don't do it for brake performance, the difference is very very minimal may be 0. Brake distance won't change or just a little bit maybe. But instead do it for heat management (it would be very very uncanny that I loose the brakes again with this setup) and lower cost of pads.

Feeling at the pedal is maybe a little bit better. That said the pedal feel like wood, I had to get use to this.
Also, you have very big braking power as soon as you touch the pedal, so modulation might be a little harder to do.
Also, I feel that I can't use 100% of the braking performance because it's too much power from the setup 😅


Overall, this is not a 100% positive modification to be honest, but I am very very happy with it and no regrets, If I had to do it again, I would !
 
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Michael Knight

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Yes.

After some more use of this kit I can confirm the brake balance still very good, I have no issue braking hard.
This weekend at the nurburgring : best lap 8:12 BTG with one yellow flag. Pace is 8:01 BTG ( this is "optimal lap" in racechrono app).
Using external GPS antenna.

Also I can confirm to anybody who wish to do the same : Don't do it for brake performance, the difference is very very minimal may be 0. Brake distance won't change or just a little bit maybe. But instead do it for heat management (it would be very very uncanny that I loose the brake again with this setup) and lower cost of pads.

Feeling at the pedal is maybe a little bit better. That said the pedal feel like wood, I had to get use to this.
Also, you have very big braking power as soon as you touch the pedal, so modulation might be a little harder to do.
Also, I feel that I can't use 100% of the braking performance because it's too much power from the setup 😅


Overall, this is not a 100% positive modification to be honest, but I am very very happy with it and no regrets, If I had to do it again, I would !
nice ! did you need new caliber mounts for the calibers or do they fit with standard mounts? How about rotor hats?
I like this as it provides better heat management overall + better disc + pad longeivity.
 

991RS

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nice ! did you need new caliber mounts for the calibers or do they fit with standard mounts? How about rotor hats?
I like this as it provides better heat management overall + better disc + pad longeivity.
What is needed :
bells (= hats ?) custom made
brackets custom made

Co-ord sport know better than me about the setup.
 
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991RS

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Feeling at the pedal is maybe a little bit better. That said the pedal feel like wood, I had to get use to this.
Also, you have very big braking power as soon as you touch the pedal, so modulation might be a little harder to do.
Also, I feel that I can't use 100% of the braking performance because it's too much power from the setup 😅
EDIT : I am now using Pagid RST3, the pedal is not as hard as RSL1, no wooden effect and modulation is better.

I guess AP racing calipers + RSL1 are too much for the Yaris.
But AP racing calipers + RST3 (or others to discover) is a lot better.