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Use the line made for brakes and are lined with teflon
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I had steel line going side to side on my dragster but thought the braided line line looked better, so I changed it. Used the braided line meant for brakes with the teflon lining. My hand brake never got hard and you could watch the braided actually expand when the brakes were applied. The steel line went back on the following week.
Quote:Hard line ONLY except to unsprung areas ( axle / caliper, etc). The braided part of a braided line does little ( if any ) control of the line expansion under pressure. It's just a protective cover from external abraision.
I thought I saw a car some time ago that had braided flex line from the master cylinder to the proportioning valve on the frame in place of steel lines. Is this safe and Nhra acceptable to do? It seems to me it would be, but you never know. If anyone has done this, pics would be awesome! Thanks - Andy
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The braided part of a braided line does little ( if any ) control of the line expansion under pressure. It's just a protective cover from external abraision.
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Mr P body, i believe your correct, the braided hose you used could have had a less tight braid that allowed alot of expansion of the teflon. its hard to say, thats why i said it was a guess. since you seem to have ruled out the too small master, it may be a matter of finding a better hose supplier.
just and FYI i am a firm believer in steel lines and only to use hose where absolutely necessary for compliance.
Quote:You are absolutely right. I ment to refer to the steel outer jacket ( abraision ) not the braided layer just outside the teflon liner. That being said, Braided line, not matter who the manufacturer, will expand under pressure. The more of it you use, the more pressure loss will occur when peddle pressure remains constant. Sure, you can overcome the loss by adding more peddle pressure, but you will lose some feel and end up with a spongier feeling peddle. Adding more fluid by going to a bigger master bore sure as hell isn't the answer. Other drawbacks include $$$ and about twice the diameter of steel line - gee, I wonder why?Quote:
The braided part of a braided line does little ( if any ) control of the line expansion under pressure. It's just a protective cover from external abraision.
this is absolutely false. the braid is an integral reinforcement to the teflon lining. brake lines work at a few thousand psi and teflon itself would not hold up. the braided brake lines are different than the braided fuel lines. the fuel line braid is there for aesthetics and abrasion resistance. the brake line is braid is there for strength. that being said there are various braided hoses manufacturers and having tested most there is a wide difference in quality between them. the braid needs to be flexible but tight on the core and some of the hoses we worked on had double braided layers.
hoses are designed to move when the braid packages are considered they are designed to swell and shorten as well as some amount of twist is acceptable. this is fine when used in a hydraulic system. its not fine when your using it in a brake system with a limited amount of pedal travel and master cylinder piston/stroke volume.
For those that had a the spongy pedal i would surmise that the extra volume added by the hoses was identifying the limit of the master cylinder if you went with a larger bore master the spongyness would go away, again this a guess, and would need to be tested. as with all engineered hydraulic systems it is important to consider the entire system when selecting parts, most racers don't and very few people actually understand hydraulics.
