Brake temps

[DoomsdayMelody]

I wanted to start a discussion on unsprung weight and it’s potential effect on brake temps. Long story short, I’m interested in what i term quality of drive modifications to my car, things that will help magnify the traits of the car that I like, without hurting the things about the car that I do like.

Two things that I’ve set to eliminate or mitigate are heat soak of the engine, and heat soak on the braking system. Since this is in the brakes forum, I’ll focus mostly on that here.

My main question is, if I were to remove 6lbs of rotating mass per corner, would I see a reduction in braking temps? Ideally on the front axle since our torque vectoring system really heats the front pads up when the road gets twisty.

I know an LSD is the correct answer for this specific question, and I know whoosh even sells some underbody fins that act as kick ups to help cool the brakes, but I was just wondering if anyone on the forum has seen an improvement on fade resistance after they’ve installed a lighter wheel/tire setup on their FiST.


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[jeffreylyon]

Removing rotating mass will have an effect on the amount of energy required to slow your car. Google "Fast Ford Light Wheels" and read the PDF. I noticed better everything when I went to lighter wheels. Removing weight from your rotors will result in higher brake temperatures due to lower thermal mass.

I late brake hard; there's a picture of me floating around throwing sparks off my front rotors on a track day. I had upgraded pads, fluid and Boomba Racing deflectors before I updated to Wilwoods. I don't remember fading but I did start to burn the power coat off my calipers. But, again, I'm not nice to my brakes. That said, never on the street did I remember thinking about wanting more brake, even before the upgrades. Unless you're trying to find another 20 feet in the braking zone on a track day I'd say live with what you have and fix it once you find its limits.

Not so w/ an I/C. One pull in third and you'll find its limit.

 

[maestromaestro]

The assumption is that if you have more weight to stop, then you have to apply a greater braking force, thus generating more heat through friction. But, if you have a greater mass/volume of metal (i.e., a thicker or bigger rotor), it would act as a heat sink, assisting in dissipating the heat from the action of the pads.

I believe the general view is that heavier rotors are beneficial - that is, the weight penalty is offset by the reduction in the braking components' temperature.

But, it is also dependent on your driving style and the course itself - so, you may be ahead with the lighter setup on a course with fewer turns/fast sweepers, for instance.

 

[DoomsdayMelody]

Removing rotating mass will have an effect on the amount of energy required to slow your car. Google "Fast Ford Light Wheels" and read the PDF. I noticed better everything when I went to lighter wheels. Removing weight from your rotors will result in higher brake temperatures due to lower thermal mass.

I late brake hard; there's a picture of me floating around throwing sparks off my front rotors on a track day. I had upgraded pads, fluid and Boomba Racing deflectors before I updated to Wilwoods. I don't remember fading but I did start to burn the power coat off my calipers. But, again, I'm not nice to my brakes. That said, never on the street did I remember thinking about wanting more brake, even before the upgrades. Unless you're trying to find another 20 feet in the braking zone on a track day I'd say live with what you have and fix it once you find its limits.

Not so w/ an I/C. One pull in third and you'll find its limit.

I had heard the IC was a better investment. I’ve not driven the car on a technical road in quite some time but true one time I was really on it on such a road I remember the smell of cooking brakes when I had stopped at a pull off. Maybe I’ll settle for those Boomba deflectors, rather than doing a full set of wheels and tires.


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[DoomsdayMelody]

The assumption is that if you have more weight to stop, then you have to apply a greater braking force, thus generating more heat through friction. But, if you have a greater mass/volume of metal (i.e., a thicker or bigger rotor), it would act as a heat sink, assisting in dissipating the heat from the action of the pads.

I believe the general view is that heavier rotors are beneficial - that is, the weight penalty is offset by the reduction in the braking components' temperature.

But, it is also dependent on your driving style and the course itself - so, you may be ahead with the lighter setup on a course with fewer turns/fast sweepers, for instance.

Makes sense from a thermodynamics persepective... so I guess shedding weight, sprung or unsprung will have a similar effect on a stock rotor.


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[jeffreylyon]

Makes sense from a thermodynamics persepective... so I guess shedding weight, sprung or unsprung will have a similar effect on a stock rotor.

Reduction of sprung or unsprung mass that is not rotating will have the same effect on the amount of energy required to slow your car from and to given speeds. *Rotating* mass has a much greater effect.

Again, I'd not spend any money on your braking system until you've decided that you've reach its limits.

 

[maestromaestro]

Makes sense from a thermodynamics persepective... so I guess shedding weight, sprung or unsprung will have a similar effect on a stock rotor.


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This is more the realm of Newtonian physics and heat transfer, not thermodynamics... On a related note, I hated thermo in grad school.

 

[maestromaestro]

Reduction of sprung or unsprung mass that is not rotating will have the same effect on the amount of energy required to slow your car from and to given speeds. *Rotating* mass has a much greater effect.

Again, I'd not spend any money on your braking system until you've decided that you've reach its limits.

Well, this is an interesting proposition. One would argue that this is precisely where you'd need to spend your money, rather than on the 'go fast' bits. The argument is that one could do well by learning how to drive a slow car fast, and if you are saying that one should learn to drive an unmolested example at its limit, I will agree. However, the braking system on the FiST is the second woeful item - right after it's ridiculous tendency to overheat on the track. So, I'd say that the money should be first spent on an oil cooler (and/or a bigger radiator) and then on the braking system, as you'd find the "limit" of those muy rapido!

 

[maestromaestro]

I had heard the IC was a better investment. I’ve not driven the car on a technical road in quite some time but true one time I was really on it on such a road I remember the smell of cooking brakes when I had stopped at a pull off. Maybe I’ll settle for those Boomba deflectors, rather than doing a full set of wheels and tires.


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I have the Boomba deflectors. If they do anything, it is relatively minor. Your better bet - notwithstanding what I said in the previous post - is to work with the heat dissipation by using beefier rotors. Also, before you do that, get yourself a liter of Castrol SRF and flush your braking system. You will boil everything else, if you drive hard enough in high heat. To that end, the pads are critical as well.

 

[jeffreylyon]

Well, this is an interesting proposition. One would argue that this is precisely where you'd need to spend your money, rather than on the 'go fast' bits. The argument is that one could do well by learning how to drive a slow car fast, and if you are saying that one should learn to drive an unmolested example at its limit, I will agree. However, the braking system on the FiST is the second woeful item - right after it's ridiculous tendency to overheat on the track. So, I'd say that the money should be first spent on an oil cooler (and/or a bigger radiator) and then on the braking system, as you'd find the "limit" of those muy rapido!

Well, like I said in my earlier post, I didn't have any problems with my stock rotor and calipers with upgraded fluid and pads on my first couple track nights in my FiST. It wasn't until I knew the car more that I ran into braking issues. I don't think OP has any intention of tracking his car..., yet.

Further, I drive the snot out of my car on track nights and don't have cooling problems in the Pittsburgh region. I'm dropping in an X-47R right now and figured that it would be a good time to add an oil cooler, but that's only because of the additional revs and heat the new turbo is going to bring to the party. OP may be in a different situation, given his locale.

 

[DoomsdayMelody]

Well, like I said in my earlier post, I didn't have any problems with my stock rotor and calipers with upgraded fluid and pads on my first couple track nights in my FiST. It wasn't until I knew the car more that I ran into braking issues. I don't think OP has any intention of tracking his car..., yet.

Further, I drive the snot out of my car on track nights and don't have cooling problems in the Pittsburgh region. I'm dropping in an X-47R right now and figured that it would be a good time to add an oil cooler, but that's only because of the additional revs and heat the new turbo is going to bring to the party. OP may be in a different situation, given his locale.

Yeah, at this point I’m planning on stock forced induction, with the possibility of running E20-30 on the stock tune. When I wear these pilot sport A/S 3s out I was considering going to a summer tire like the fire hawks... but then had the thought of minus sizing my wheel/tire setup to help regulate brake temps. Not that I’ve found the limit of the braking system, that’s just more of a limit I’d rather not discover. Only other planned mod is an IC, since my entire plan with this car is to keep the magic of the car as it is and only mod it to compliment the strengths it already has.

Haven’t tracked it, don’t have plans to track it, but would certainly like to get into autox, and have plans to do so in the near future... maybe.


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[DoomsdayMelody]

I have the Boomba deflectors. If they do anything, it is relatively minor. Your better bet - notwithstanding what I said in the previous post - is to work with the heat dissipation by using beefier rotors. Also, before you do that, get yourself a liter of Castrol SRF and flush your braking system. You will boil everything else, if you drive hard enough in high heat. To that end, the pads are critical as well.

Beefier rotors as in a BBK? Or is there a manufacturer that sells a higher density rotor in the stock size?


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[TyphoonFiST]

Or just get Cryoed rotors.....IMO

 

[DoomsdayMelody]

This is more the realm of Newtonian physics and heat transfer, not thermodynamics... On a related note, I hated thermo in grad school.

I’d say tomato, tomahto but you sound like you are a bit better versed on this stuff lol (by a bit I mean significantly)


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[DoomsdayMelody]

Or just get Cryoed rotors.....IMO

Had looked at that as well, but I feel like that’s a bandaid and not fixing the primary issue, which is that our brakes are kinda undersized for the scope of their responsibility. I have no experience with cryogenically treated rotors, but at that price point and their relative lack of durability, you’d almost be better off and dropping the cash on a LSD.


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[TyphoonFiST]

I have Cryoed rotors by power slot. Pretty good in my opinion...hell you can get anything you want Cryoed...pads...rotors and other parts. Its done by Diversified cryogenics/ Frozen rotors here in MN.

 

[maestromaestro]

I have Cryoed rotors by power slot. Pretty good in my opinion...hell you can get anything you want Cryoed...pads...rotors and other parts. Its done by Diversified cryogenics/ Frozen rotors here in MN.

I hate to bring my credentials out, but - cryo treatment of rotors is garbage, metallulrgically speaking. It is used to impart marginal improvement in wear resistance, transforming retained austenite to martensite. Has nothing to do with heat transfer; moreover, I don't believe that the steels that are used in fabrication of the rotors have any retained austenite to begin with. I am too lazy to look. But - again, nothing to do with the heat transfer/dissipation.

 

[jeffreylyon]

Had looked at that as well, but I feel like that’s a bandaid and not fixing the primary issue, which is that our brakes are kinda undersized for the scope of their responsibility. I have no experience with cryogenically treated rotors, but at that price point and their relative lack of durability, you’d almost be better off and dropping the cash on a LSD.

I don't think the cryo-ed rotors will have any effect, at all, on heat transfer or resistance to soak. It's all amount pads and fluid to reduce fade and air to increase heat rejection.

The FiST has two traction modes, traction control and ECS. Most people turn both off when driving in anger. We can't turn off TVC, but, on the street, that isn't going to increase brake temperature much unless you're driving like a mad man. In short, an LSD, which will be close to $2000 with installation, won't help brake temps. on a street-drive FiST, especially when the nannies are off.

However, on an A/C circuit an LSD will make a huge improvement in corner exits. That's another conversation.

 

[jeffreylyon]

running E20-30 on the stock tune

That won't do anything but reduce power. You need a new tune to take advantage of E30. Without one you're just running your car with less potent fuel.

Not that I’ve found the limit of the braking system, that’s just more of a limit I’d rather not discover

Fade is not the end of the world and usually comes up gradually. If you find yourself running your brakes into fade it's time to think about brake upgrades. The first would be pads and fluid. If you're still running out of brakes maybe it's time for ducting or bigger brakes. You might be prematurely optimizing a bit.

 

[DoomsdayMelody]

That won't do anything but reduce power. You need a new tune to take advantage of E30. Without one you're just running your car with less potent fuel.

I had been given a different impression here:

https://www.fiestastforum.com/threads/second-fist-2016-fiesta-st.10415/

Granted, no two engines will respond identically, but I’d assumed that the stock programing can take some advantage of the increased octane rating, even if you need a tune to get the full benefit.

Fade is not the end of the world and usually comes up gradually. If you find yourself running your brakes into fade it's time to think about brake upgrades. The first would be pads and fluid. If you're still running out of brakes maybe it's time for ducting or bigger brakes. You might be prematurely optimizing a bit.

That’s a fair assessment, seems to be what most everyone is suggesting. I guess I’ll be prioritizing either the IC or the radiator first.


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