Hot Brakes - Undertray the cause?
Jul 18, 2009, 08:56 PM
#1
Hot Brakes - Undertray the cause?
So I've been tracking my Evo IX for nearly 3 years. Never really had any brake problems before. I've gotten a mushy pedal in the past, but that was back when I had bad braking (over-braking) technique and a mostly stock setup.
Fast forward to 2009. Did a few events this year; no problems. I bleed after every weekend event; and flush a few times a year. Here's my brake setup now:
- Hawk DTC60's, Goodridge SS lines, Forge Air Cooling Ducts, Motul fluid, front Ti shims
.......Then I installed a Beatrush Undertray. First event out it was about 94 ambient and I was getting a soft pedal in every session; actually lost my brakes in one session. Pedal to the floor and everything. I chalked it up to the temps and braking too much. I bled the brakes and the next day I kept the sessions short and things seemed ok.
Today; in the first session no less - brake pedal to the floor and nothing! Ambient temp like 65. Off-track (obviously) at a high rate of speed. Pumping the brake pedal and using the e-brake even to no avail.
So I flushed the entire system of fluid and went ahead and removed the underpanel while I was at it since the car was jacked up. ZERO problems the rest of the day.
Seems pretty cut-and-dry to me that the underpanel is causing my issues. Anybody else have any issues like this or a different hypothesis to offer?
Fast forward to 2009. Did a few events this year; no problems. I bleed after every weekend event; and flush a few times a year. Here's my brake setup now:
- Hawk DTC60's, Goodridge SS lines, Forge Air Cooling Ducts, Motul fluid, front Ti shims
.......Then I installed a Beatrush Undertray. First event out it was about 94 ambient and I was getting a soft pedal in every session; actually lost my brakes in one session. Pedal to the floor and everything. I chalked it up to the temps and braking too much. I bled the brakes and the next day I kept the sessions short and things seemed ok.
Today; in the first session no less - brake pedal to the floor and nothing! Ambient temp like 65. Off-track (obviously) at a high rate of speed. Pumping the brake pedal and using the e-brake even to no avail.
So I flushed the entire system of fluid and went ahead and removed the underpanel while I was at it since the car was jacked up. ZERO problems the rest of the day.
Seems pretty cut-and-dry to me that the underpanel is causing my issues. Anybody else have any issues like this or a different hypothesis to offer?
Jul 18, 2009, 11:32 PM
#2
Depends on how your ducts are ran. I learned quickly that long *** ducts with tons of bends going to the front bumper yielded nill flow (compaired to the air i was pumping out of the compressor). Then I ran a short duct (less then 1.5 feet) with only one bend and holy sh*t there was air. I won't give out all the secrets but you get the idea. Basically your lack of tray WAS your air duct before.
Jul 18, 2009, 11:38 PM
#3
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I am not sure but I am guessing those ducts are not duct tubing like the AMS kit. If that is the case and those are just curves designed to guide air to the brakes, your Beatrush undertray is now likely blocking them. Get something like the AMS duct (tubing) kit and you will be thrilled, night and day difference. Good luck!
Jul 19, 2009, 04:40 AM
#4
I am not sure but I am guessing those ducts are not duct tubing like the AMS kit. If that is the case and those are just curves designed to guide air to the brakes, your Beatrush undertray is now likely blocking them. Get something like the AMS duct (tubing) kit and you will be thrilled, night and day difference. Good luck!
So good point; I'm sure the larger AMS 3" kit would help out.
Depends on how your ducts are ran. I learned quickly that long *** ducts with tons of bends going to the front bumper yielded nill flow (compaired to the air i was pumping out of the compressor). Then I ran a short duct (less then 1.5 feet) with only one bend and holy sh*t there was air. I won't give out all the secrets but you get the idea. Basically your lack of tray WAS your air duct before.
Jul 19, 2009, 05:01 AM
#5
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Q
Few Qs for you;
1) Were you running the stock undertray before installing Beatrush one?
2) I know you track your car quite often. When was the last time you rebuilt your caliper, exchanging worn-out piston seals?
Let's start from there.
1) Were you running the stock undertray before installing Beatrush one?
2) I know you track your car quite often. When was the last time you rebuilt your caliper, exchanging worn-out piston seals?
Let's start from there.
Jul 19, 2009, 08:56 AM
#6
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Yes the larger tube would help out but I am surprised you noticed such a massive difference with a change of undertray. Balrock is right that a more direct path with the tubing is better, but unless you have ground pickups for the ducts underneath the car, it is a giant pain to route the piping past the ACD pump. For what its worth, mine are not especially straight and while I think the wear is uneven on the pads left to right, I still noticed a massive difference having the AMS ducting kit so I am not sure how Balrock got little to no air flow. Despite the uneven wear, I never have any issues with uneven braking left to right.
Jul 19, 2009, 09:31 AM
#7
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Hey Boom 29,
Yeah mushy pedal sucks. Your new setup consist of DTC60's, etc... what was your old setup? Have you also upgraded to R-compounds?
It sounds like you are getting faster and upgrading your braking to match. Your deduction of undertray or no undertray is not so cut-and-dry. And everyone here is pointing to other variables.
Did you install the tray after the complete flush? Maybe that's all you needed was a flush as oppose to a bleed? It seems you have amassed a decent setup. I would look more at upkeep than the parts. If anything I would use Castrol SRF. It is expensive at $80 a liter but considering your track day probably cost you $600 for the weekend (track fees, gas, hotel, tolls, food) it is a small price to pay and it works like a ****.
I personally do not run with a tray because I am lazy. But there is a distinct engine cooling and car aerodynamic benefit to running one.
Yeah mushy pedal sucks. Your new setup consist of DTC60's, etc... what was your old setup? Have you also upgraded to R-compounds?
It sounds like you are getting faster and upgrading your braking to match. Your deduction of undertray or no undertray is not so cut-and-dry. And everyone here is pointing to other variables.
Did you install the tray after the complete flush? Maybe that's all you needed was a flush as oppose to a bleed? It seems you have amassed a decent setup. I would look more at upkeep than the parts. If anything I would use Castrol SRF. It is expensive at $80 a liter but considering your track day probably cost you $600 for the weekend (track fees, gas, hotel, tolls, food) it is a small price to pay and it works like a ****.
I personally do not run with a tray because I am lazy. But there is a distinct engine cooling and car aerodynamic benefit to running one.
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Jul 19, 2009, 10:57 AM
#8
Hey Boom 29,
Yeah mushy pedal sucks. Your new setup consist of DTC60's, etc... what was your old setup? Have you also upgraded to R-compounds?
It sounds like you are getting faster and upgrading your braking to match. Your deduction of undertray or no undertray is not so cut-and-dry. And everyone here is pointing to other variables.
Did you install the tray after the complete flush? Maybe that's all you needed was a flush as oppose to a bleed? It seems you have amassed a decent setup. I would look more at upkeep than the parts. If anything I would use Castrol SRF. It is expensive at $80 a liter but considering your track day probably cost you $600 for the weekend (track fees, gas, hotel, tolls, food) it is a small price to pay and it works like a ****.
I personally do not run with a tray because I am lazy. But there is a distinct engine cooling and car aerodynamic benefit to running one.
Yeah mushy pedal sucks. Your new setup consist of DTC60's, etc... what was your old setup? Have you also upgraded to R-compounds?
It sounds like you are getting faster and upgrading your braking to match. Your deduction of undertray or no undertray is not so cut-and-dry. And everyone here is pointing to other variables.
Did you install the tray after the complete flush? Maybe that's all you needed was a flush as oppose to a bleed? It seems you have amassed a decent setup. I would look more at upkeep than the parts. If anything I would use Castrol SRF. It is expensive at $80 a liter but considering your track day probably cost you $600 for the weekend (track fees, gas, hotel, tolls, food) it is a small price to pay and it works like a ****.
I personally do not run with a tray because I am lazy. But there is a distinct engine cooling and car aerodynamic benefit to running one.
I figure it is a combination of things. Figured it'd be a good topic to discuss. And my 'off' was pretty serious; track exit about 90mph.
Jul 19, 2009, 03:20 PM
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The only time I’ve had a mushy pedal is when I ran the reservoir dry and induced air into the system. After bleeding and bleeding and bleeding, I managed to get all the bubbles out and no more mushy pedal.
Other than that, no problems with my cooling ducts under the tray.
Other than that, no problems with my cooling ducts under the tray.
Jul 19, 2009, 07:21 PM
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18bora, I like that setup too. What is your ride height? I am very low to the ground for street use (properly corner balanced and aligned, not slammed 
) and I am not sure I could get something like that under my car. However, being so close to the wheels and a good ways behind the front end, they may clear easily. What did you make the intakes out of?
) and I am not sure I could get something like that under my car. However, being so close to the wheels and a good ways behind the front end, they may clear easily. What did you make the intakes out of?
Jul 20, 2009, 05:29 AM
#14
2) I actually rebuilt the front this year by putting in all new seals and dust boots. Coincidentally (I hope) right at the same time I installed the Beatrush panel. I also put on my 3rd set of rotors.
