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Author Topic:   Brake System
Dirt Full Roller

Total posts: 66
posted April 18, 2002 10:51 PM
Got a few ?'s before I start making my brake system. It's a metric car and I'll be using an aftermarket hanging reverse mount assembly w/ balance bar. On the rear-end I'll most likely be going with discs rather than drums with all four calipers being the same (metrics).

1) Generally speaking, a prop valve is considered a course adjustment and the balance bar is considered a fine adjustment. With that said, is there usually enough adjustability in the bar alone without using a prop valve for front/rear bias?

2) What size master cylinders do I need to go with? Same for front and rear or a smaller one (more pressure, less volume) for the front?

3)On the RF I was thinking of running a shut-off valve but thought about also putting a prop valve in that line so that I could have something other than just on and off. Is this necessary or should I keep it simple and stay with shut-off only?

4) Plastic brake lines. I don't necessarily want your general opinions of them as they have already been posted on previous topics. I see no problems with using them on modifieds, late models, etc... What I would like to know from you though is whether or not you yourself have put plastic lines on your heavy street stock before and how it has worked/not worked for you. Has the extrta weight of the vehicle had any affect on the system in general? It would seem to me at first glance as though the extra weight would be nullified by the slower speeds from which you are decellerating from but I'd like to hear from someone who has already tried them.

Many thanks and I apologize for the length.

Dirt Maniac

Total posts: 140
posted April 19, 2002 01:32 AM
Hi opinion.....

1) Yes. There is usually enough adjustabillity to use only the balance bar,provided everything is sized correctly.

2) Use a 7/8 bore for the front and a 1" for the rear.

3) Many late models do use a proportiong valve and a shut off on the RF. It makes sense to me. Is it nessasary on streetstocks?
I would say No,but it is a nice adjustment tool. I always tell new streetstock racers not to use a RF shutoff........One needs some seat time first....get comfortable racing beside others first......

4) Hope You don't think this is a "general opinion", here goes anyway...... Plastic has more elasticity than steel. Uses up more pedal travel...... For this reason,and a saftey concern,I do not use or recommend them.I use 3/16 steel lines.

I will conceed that plastic lines will work for your car and they are fast and easy. I think Sleepy said he has used them for many years with no problem. So,they must be better than I give them credit for. It's not really a right or wrong question.

Good Luck,

Dirt Maniac

Total posts: 199
posted April 19, 2002 10:33 AM
Snowman is right about plastic lines having a little expansion. I used them on go karts back in the 1970's, and later on in sprint cars. On my I-Stock (metric) I use plastic lines all the way to the caliper. They are fast and easy to install and repair. With the pedal being a touch softer, make sure you have enough travel on the master cylinder. I had to re work my first bracket to get all the travel in the m/c. Doesn't mean I won't, but in 30 years I've never had a problem.

Heavy car vs. light: The hydraulic pressure in the brake system is about the same in karts, sprints and stocks. The nylon lines used have a pressure rating of about 1000 psi greater than the brake pressure. SLEEPY

snowman don't forget to call sometime

Dirt Full Roller

Total posts: 66
posted April 19, 2002 08:25 PM
Thanks for the info guys. Snowman, didn't mind your "general opinion" at all. Now that I re-read my post it did sound kinda snotty on that part but wasn't intended to be.

Dirt Maniac

Total posts: 140
posted April 23, 2002 12:40 AM
BlaneP, I didn't find your question rude. You were seeking very application specific information,which I tried to provide. Not having personal experience with plastic lines, All I could provide was my reason for not using them. I had always assumed they were junk untill I seen Sleepy recommend them.Obviously, they work better than I thought.

One more thing....(and I know that you know this Blane, but I include it for any newbies)
This info is for the specified bore and caliper sizes ONLY. These items must be sized to each other.

Good Luck to you this season Blane.

Sleepy....Hi. Sorry it has taken so long to reply. Been out of town working again. I had just got home and had to leave again. Now I'm working late locally. Look at the time I'm posting....Geez...I need to get a life....I think I will be home at a decent hour Wednesday. I'll see if I can catch you then.

I just read you shock dyno article yesterday. Great article. To have some economical means of comparing, thats a good idea. I think we got bit a couple of times by the high/low tollerance deal.
Catch You later,

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