240sx brake cooling

[dan240]

Hi,

I have a SOHC 240sx coupe that I have autocrossed for years but have never taken to any track days. I have delusions of running it in IT some day. I will be running the car at Willow Springs this month and I am wondering what your guys do to handle brake temps.

With a NA 240sx are good pads and fluid enough? Will I need to remove the dust shields and add some ducting?

I know you guys run with stock sized rotors and I'm wondering if thats enough on this car.

Thanks,
Dan

[erlrich]

I don't have any extra cooling on my car, but I'm sure it wouldn't hurt if you wanted to add some ducts. I run blues on the front, hp+ on the rear (poor boy's bias adjustment), stainless braided lines, and use RBF600 fluid. Everything else is stock. I do replace the pads and rotors when the pads are down to about 1/2 thickness, and I bleed the brakes after every session. I have yet to have a problem with fade.

[Tristan Smith]

The brakes are good on these cars, but ducting air on them helps. Most of us have at least one duct if not two on the fronts. Other wise see above.

[dan240]

Thank you for the info. That takes some worry off my mind.

Can I assume that most of you guys also run a proportioning valve on the car. (in regards to the "poor boys" bias adjust)?

Best,
Dan

[Tristan Smith]

No bias, it's built into the brake master cylinder, so not a lot that you can do except use different pads.

[CCARVER]

I have been running HT-10s all the way around with no issues.
I have 3" ducts in the front from the factory vents in the bumper run to the calipers.
I plan to do the 8 hr enduro with NASA in Jan. I will update you then on how everything holds up for that time frame.
But all is good for the last two years of racing this current setup.
Carver

[jamsilvia]

I've run my car with Hawk blues all around, and with the ABS calipers up front. The only time I've ever had brake issues (even running the car in several enduros) was when I ran with < 1/4 of pad (hey, it was only a sprint race!!). Well, the track was damp - i.e. very slick, and required a lot more braking than normal. After about 10 laps I had to pump the pedal up. So I'd never run them that low again!

As far as bias is concerned, with the ABS calipers in the front (and ABS m/c...they're all on the same line item) - I have too much FRONT bias. Anyone else have similar results? I had thought that I would have to put the bias control in the front lines, not the rear line. Thoughts???

joe

[Tristan Smith]

Someone please correct me if I am wrong, but bias only works if you can change the relationship between the amount of pressure going to either the front of rear brakes. Since bias is built into the master cylinder you really can't change that unless you re-plumb a significant amount of your braking system, which I don't think would be allowed in the rules.

Jam, I would say go back to a stock master cylinder. I run the standard MC and ABS calipers and rotors and don't have problems locking up the fronts unless driver error is involved.

[JeffYoung]

Actually, brake ciruicitry "may be revised." In other words, my belief (and others concur) is that you have to use the stock calipers and the stock master cylinder, but pretty much anything in between is free. So, yes, even on your car you could affect line pressure and bias by putting an adjustable valve in each line to adjust the front bias down, and the rear up.


Someone please correct me if I am wrong, but bias only works if you can change the relationship between the amount of pressure going to either the front of rear brakes. Since bias is built into the master cylinder you really can't change that unless you re-plumb a significant amount of your braking system, which I don't think would be allowed in the rules.

Jam, I would say go back to a stock master cylinder. I run the standard MC and ABS calipers and rotors and don't have problems locking up the fronts unless driver error is involved.

[erlrich]

Yeah, I also think based on the rules you could add bias adjustment to either end of the car, but with the fronts it would be a mojor PITA since you would have to add an prop valve in each line, whereas for the rears you would only need the one.

Joe - I've never heard anyone complain about too much front bias in these car, at least not on a dry track. Even with the blues front/hp+ rear pads I will still lock up the rears first. I agree with Tristan I would try going back to the non-ABS m/c and see if that helps.

[JeffYoung]

You may also want to get a line pressure gauge (fairly cheap) and check the line pressures. When I did that (got a guage) it helped me diagnose a kinked line that was affecting pressure to one caliper.

[MikeITA240SX]

I have run at tracks in Wa, Or, BC and Thunder Hill in No. Cal. for several years with the ABS calipers/rotors, Hawk Blues and 3" ducts in front, and Hawk Blues in the rear. I use the Motul RBF600. This setup has been very reliable. The stock bias has always been excellent. I have always felt that if I needed to change it, I would start with changing the pads on one end or the other. I have run Hawk Blues on the front and Axxis Metal Masters on the rear, but decided I liked the improved control and durability of the Hawks in back too. (Truth is that Metal Masters will work fine on all corners on a track that is easy on brakes, like Portland International without the Festival Curves (chicane), but won't hold up at all on harder braking tracks like Mission).

The only time/place I have felt like I needed more brake or more cooling has been at Mission Raceway in B. C. This is a very challenging short course that wrings everything out of brakes, car and driver. Over Labor Day weekend, I was beginning to see the limits of my brake setup, but I am pretty sure that if I had some HT-10s for the front, that would have solved my problems.

When I first got the car, it had the smaller non-ABS setup in the front with 2.5" ducts, and I had more than one brake fire reported by turn workers. Part of it could have been my early driving style, but putting the larger ABS setup on definitely made a big difference, and I have never regretted it.

[DavidM]

non-ABS rotors here with one duct cooling the rotors and another the calipers. Hawk blue pads. No fade issues. I can't comment on a setup without cooling as this is how the car was when I bought it. I'd personally have at least something cooling the rotors.

David

[jamsilvia]

I wonder whether I'm getting more front bias due to the fact that I'm not running any brake ducts at all. Could it be that the fronts are in a higher heat range where the coeff of friction is higher than my rears?

I will also rebuild my stock M/C and see if its any better vs the ABS one.

[invisible saddle]

check out www.splparts.com they have brake ducting but of a different style and design