K-sport hand brake issues
Posted by MarkHille
Mark Hille Ultra Moderator Location: The hills of CT Join Date: 10/04/2011 Age: Midlife Crisis Posts: 135 Rally Car: I have two crap boxes |
Just to add a little clarity:
The problem with MY k-sport wasn't poor craftsmanshit, it was in the design of the master. It looks similar to this one: 
If you notice there is a yellow circle around the front seal. The problem is that when you apply pressure from the inlet side and also from the piston you get a certain amount of pressure at the outlet side. When you remove pressure from the inlet side the pressure from the outlet side forces that seal to remain sealed and you get higher pressure (not as high as it once was because you have let off the piston) still remaining on the outlet side keeping the rear brakes on. When you apply the brake pedal again, it brakes the seal in the yellow circle and allows the pressure to equalize until the next time you push the pedal and pull the handbrake at the same time. If you have a master with this design and you don't experience this problem it is because your seal isn't 100% and the pressure is allowed to equalize and release the seal. This also causes a low pedal as when you pull the handbrake it allows some fluid past this point that the main master has to overcome at some point. But if it is only a small amount it is hardly noticeable and is much preferred over the sticking rear calipers. Or you may also just never notice that the brake is sticking. One solution to the sticking problem would be to create some sort of very small bleed from the inlet side of the seal to the outlet side of the seal. You could drill a .013" hole and place a .012" stainless steal wire in the hole where the blue mark in the yellow circle is. That would in theory be enough to bleed off a small enough amount of fluid so that the handbrake would still work properly but it wouldn't hold pressure locking the seal in place. Of course this would mean that the handbrake would no longer be able to be used as a parking brake because the pressure would be lowering over time and the brakes would eventually disengage. This is not recommended because the rules state you need a working parking brake although I don't know how many of these hydraulic handbrakes would work as a parking brake anyway. |
Grant Hughes Super Moderator Location: Whitefish, MT Join Date: 01/11/2006 Age: Midlife Crisis Posts: 6,818 Rally Car: BMW |
Elite Moderator Join Date: 07/25/2014 Posts: 1 |
Alex Rademacher Elite Moderator Location: Reno,nv Join Date: 09/10/2007 Age: Midlife Crisis Posts: 686 Rally Car: 93 GC with an 01 RS swap! |
I just don't get the obsession with hydraulic hand brakes. Rallies in the south west don't really have hair pins. (I've seen 1 tight true hair pin out of 8 or so different events)
Then again i'm the guy who won't paint his car, get my name on my driving suit, etc. wouldn't having adjustable brake bias (front to rear) in real time be a lot more helpful ? and even negate the need for one? like Oh i'm coming up to the 1 hair pin in this entire rally, i'll dial my brake bias to be max rear, take the corner, and set it back to normal(ish) ? also wouldn't it be cheaper? (not trying to Rag on the OP ) 
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A.J. Johnson Infallible Moderator Location: Pendleton OR Join Date: 01/07/2011 Age: Settling Down Posts: 1,381 Rally Car: 88 Audi 80 |
Aaron Luptak Mega Moderator Location: SLC Join Date: 02/15/2008 Age: Midlife Crisis Posts: 776 Rally Car: Civic... |
why oh why would you make a custom little sheet metal bracket, and not bother to make it actually fit the master cylinder, and just hang it off the back with bolts and spacers instead? (I suppose it's better than a stack of washers...) personally, I was thinking of getting the ASD one (http://asdmotorsports.3dcartstores.com/ASD-Universal-Hydraulic-E-Brake-16-Pull-Back_p_51.html), but now that I look closely, it's just a wilwood clutch pedal (http://www.jegs.com/i/Wilwood/950/340-1289/10002/-1?parentProductId=744524) with a slick handle.  KF7RWG 
http://www.utahrallygroup.com |
Kevin Turner Elite Moderator Location: Newark, DE Join Date: 01/27/2006 Age: Midlife Crisis Posts: 364 Rally Car: 2wd Impreza... dude you should do an sti swap |
A.J. Johnson Infallible Moderator Location: Pendleton OR Join Date: 01/07/2011 Age: Settling Down Posts: 1,381 Rally Car: 88 Audi 80 |
Mark Hille Ultra Moderator Location: The hills of CT Join Date: 10/04/2011 Age: Midlife Crisis Posts: 135 Rally Car: I have two crap boxes |
I'm not offended. I think there are legitimate reasons to put a hydraulic handbrake in a rally car. My reasons include: -The stock parking brake didn't really work. It made noise and would drag the brake a bit but wouldn't keep the car from rolling on a hill. -When I put wilwood calipers on they didn't come with an option to hook the stock or any parking brake cable to them. -The k-sport brake actually has a little bar that will lock the lever in position keeping the handbrake on. Its only a matter of how long it will hold pressure for. -I love pulling the hand brake. -I want to be a drift king. I started this because I didn't know what was going on and didn't really like the fact that I could have my rear calipers dragging and not realize it. |
Grant Hughes Super Moderator Location: Whitefish, MT Join Date: 01/11/2006 Age: Midlife Crisis Posts: 6,818 Rally Car: BMW |
I helped a local rallyist swap a rear upright this weekend. Easily the biggest pain and time consuming part was removing the parking brake cable and disassembly and reassembly of the drum brakes.
So here's a few benefits of a hydraulic handbrake. 1. No disassembly of parking brake to swap a rear upright. Could prevent a penalty in service. We swapped and upright in Parc Expose at 100AW this year. Without parking brake stuff it's relatively easy. 2. Less unsprung weight - Not much but you do get to lose the shoes and parking brake internals. 3. Less rotational mass - Again not much but you also get to remove the ABS trigger wheels. Sure, that has nothing to do with the parking brakes but I don't care. Grant Hughes |
Alex Rademacher Elite Moderator Location: Reno,nv Join Date: 09/10/2007 Age: Midlife Crisis Posts: 686 Rally Car: 93 GC with an 01 RS swap! |
the more i know!
really good insight here
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