From: Jay Kempf [jkempf@tds.net]
Sent: Friday, November 10, 2000 9:12 AM
To: 928
Subject: [928] RE: stainless steel braided brake lines (sorry, long)

Dan,

This has come up before. The deal is that Teflon does not have any rebound
(or memory). Why that's important is not in the short term but in life
expectancy. A brake system is a finicky container that likes to keep a small
amount of fluid in the right places for use when needed. There are many
potential leaks in the system, 8 of which are the crimped ends of the brake
hoses at each caliper. Each end fitting is basically a hose barb that the
flexible hose is tightly slipped over and then an outer crimp sleeve is
crushed in place to make a permanent connection. Nitrile rubber (Buna N) is
a normal material for the hose using regular brake fluid (basically mineral
oil). This soft rubber will remain in place for 10 or more years without
drying out and loosening in the crimped area of the hose. Teflon on the
other hand just compresses and then loosens immediately. It might last a
year or it might last a week or maybe only one race. Creep is a term used to
describe what happens to Teflon as it moves under compressive loads.

The reason people use Teflon is more temperature than anything else. Where
is that important? On the track. What else is true about the track? Most
people don't care about their cheap parts lasting for next season. What else
is true about Teflon? To have the same tensile strength as a rubber it is
more of a rigid plastic. What does that mean? It doesn't give as much under
internal pressure. What does that mean? It gives a slightly stiffer pedal at
the limits of use. Why is the stainless braid on a hose assembly like a
teflon hose? Cause it can't take repeated pulls from wheel movement. It
doesn't back it up for pressure reasons only pull out at the crimped
fitting.

Why should you think my opinion is worth anything? Well, my company buys
about 3 million dollars worth of Teflon products from Dupont and W.L. Gore
(GoreTex) every year. I spend alot of time discussing sealing
characteristics of these products with their engineers.

Send the Teflon lines back and get OEM ones. Sleep better tonight.

Jay Kempf
79 US 5 speed WIP


-----Original Message-----
From: daniel perez [mailto:lt_texan@hotmail.com]
Sent: Friday, November 10, 2000 8:21 AM
To: 928
Subject: [928] RE: stainless steel braided brake lines


I bought these brake lines from AJ USA

(http://www.ajusa.com/cgi-bin/shop/viewpart?cart=736980081535876&oid=5356832
)

I rechecked the site and it says nothing about the brake lines being for off
road use.

I'll call them today and find out what gives and post the results.

Dan
78 5 speed
928OC