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Question Brake Lines SS vs Stock rubber

After 25 years of faithful service I believe it is time to retire my stock 79 911SC brake lines. With such service I am wondering why I would change from rubber to ss. I suppose the cost is close. Any views why I shoud go to stainless steel.

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Old 01-06-2004, 05:59 PM
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After speaking with Steve Weiner and others, I stayed with rubber lines as they require less periodic maintenance and the the rubber lines should be ok for 10 years.

SS lines look cool but they tend to flex and break. On a race car this not a big deal as they get inspected/replaced frequently. On a street car, I am not sure the extra expense is worth the extra hassel.
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Old 01-06-2004, 06:13 PM
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You will have a better pedal feel with SS. The rubber lines expand like a balloon under pressure giving your pedal a softer feel as the rubber expands.
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Old 01-06-2004, 06:15 PM
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This is an excellent question/thread that I am surprised doesn't come up more often. It is true that rubber lines can swell a little, but more so if they are older(?)

I installed SS, DOT approved lines in my car when I bought it as part of a total brake refurb job. I just always have chosen to believe that they increase brake performance, (albeit only slightly), due to a more positive transference of hydrolic force to the calipers in extreme duty situations. (Less energy lost to line flex). In every day driving, they contribute to a great pedal, plus they look cool. (Very important).

I am anxious to hear from Bill Verburg or one of our other brake experts on this.
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Old 01-06-2004, 06:23 PM
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It is pointles to change to the SS lines ... 99.99% of the anecdotes about 'improved' feel is the 'Placebo Effect' at work! There may be an improvement over old, worn out lines, but changing between new OEM rubber and Teflon/stainless lines will produce unreliable/indeterminate data in a double-blind style test -- every time!

The SS lines swell when pressurized ... just like OEM lines! I have watched them and witnessed it, personally. The single-wire braid isn't really that strong when pressurized to 1000-1500 psi!

The REAL reason that SS lines were adopted for racing is related to resistance from damage (compared to rubber hoses) by contact with debris or during off-course excursions!
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Old 01-06-2004, 07:15 PM
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i just installed the rubber ones. in my opinion, i think the brand new black rubber with the clean (zinc? colored) fittings look plenty good. to bad it made the hard lines look like @$$!
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Old 01-06-2004, 07:21 PM
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I'm not trying to rob this post so let me know if my question is inappropriate. First, I converted to SS because it was my understanding that they will expand less than rubber. Secondly, and my question, what is a good source for DOT hard brake lines. For example, flex to caliper, T to flex. Pelican has the left side T to flex but not the right side; flex to caliper are nla. Again, if a separate post is warranted let me know. Thanks in advance.
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Old 01-06-2004, 08:14 PM
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I just put SS lines from Pelican on my car last week. I did it for two reasons. 1. The originals were 19 years old and I though it was time. 2. A little extra protection from debris on the track.
I have not noticed an improvement in pedal feel. My car always has had a very hard pedal. The only complaint is they take standard wrenches instead of metric. Small point, but it just seems a little weird.

Jeff
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Old 01-06-2004, 08:21 PM
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Interesting topic, I believe I'll be changing this summer, and I'll stick with rubber because someone told me once with the rubber you can see signs of failure before it happens; whereas stainless you cannot see issues until it's too late.

Just my two cents (CDN)
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Old 01-06-2004, 08:31 PM
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Thanks for the posts. Ordered rubber today from Pelican.
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Old 01-07-2004, 05:15 AM
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I used to road race motorcyles, and there was a very real difference in brake feel and lever travel when you changed the rubber hoses, on a new bike, to new braided stainless lines. When you use your fingers to brake, as opposed to you feet, you have much more brake feel and you really notice the difference.

On my 911, I rebuilt the calipers last year and replaced the rubber lines with DOT stainless. I have a firmer pedal now, but since I rebuilt the calipers at the same time, I can't absolutely say they made the difference, but I believe so.

Also, my other car is a 96 Mustang Cobra. Many organizations won't let you on a race track with one, unless you have replaced the front brake hoses with braided stainless lines because of failures of stock rubber lines, though that was more of a design/fab fault on Ford's part.

Regards,

Jerry Kroeger
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Old 01-07-2004, 07:08 AM
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i think on a motorcycle, the brake line is significantly longer (compared to the tiny 911 rubber parts). my streetbikes, were rubber from the MC down to a T and then to the calipers. i think using braided is ok here because it may control some swelling due to all the extra rubber and the brake lines are out there totally exposed. i still use rubber because after breaking my leg in a crash, i am SLOW!
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Old 01-07-2004, 09:06 AM
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My ss lines are warranted for life, no rubber lines can equal that claim, so much for the idea they don't last as very long.
Old 01-07-2004, 11:21 AM
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Good thread idea Old Tee, it cleared up some confusion I was having on this subject as well. It looks like I am leaning toward ordering the rubber when it comes time to redo my brake lines.

Last edited by Par911; 01-07-2004 at 11:44 AM..
Old 01-07-2004, 11:41 AM
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I don't think a clear 'winner' has been determined here. If SS lines give a perceived firmer pedal so be it. The lines need to be inspected regularly regardless of type so just make sure they are installed the correct way and maintain them like everything else on your car!
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Old 01-07-2004, 11:46 AM
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I too was confused as to what to buy. The lines on my car are dated 1976 and I have good brakes. I could see old age setting in, I did research and figured these lasted close to 27 years without failure and I have yet to see any good reasons to change.
Tom
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Old 01-07-2004, 12:25 PM
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Many moons ago all the 911 track cars all went to SS lines. The brake peadle was firmer - too firm. Someone came out with a spring device in the hydralic circuit that returned some "give" to the brake feel.

I like the feel of the rubber/fabric lines.

The technical reason is that under limit-of-traction braking you sense brake lock-up and modulate the brake pressure. Since there is a delay in our bod, having some "give" in the hydrolics makes the brake system more forgiving and less prone to unintended lock-up. At the tire rotates there is varing traction depending on the tire and road surface. If the tire skidded on the previous rotation, it heated a patch of rubber. During the next rotation that patch is hotter, has less grip and is more prone to lock-up. There are also subtle variations around the rotor.

Most important are the dynamics of the car. As you trail brake into a corner, the inside front wants to lock-up. In some cirmcumstances it's off the ground so it doesn't matter if the tire is stopped. Ask Colorado's Das Schwartzgruppe. Rough pavement, undulations, and cornering have great influence on braking ability. You want to be able to use all possible.

What most on this thread are talking about is street and mild track driving, not limit-of-traction record attempts. Use the rubber lines. If you want SS lines for show, so be it. If, on the track you want damage protection, I recomend one-use duct tape over rubber lines.

BTW, I would replace the master cylinder much more often than the brake hoses. How are your caliper pistons/cylinders? Have you lubed and cycled them regularly? How is the fit of the pad in the caliper?

Best,
Grady
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Old 01-07-2004, 12:29 PM
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There are quite a few points were hysteresis rears its ugly head. The rubber lines are one, calipers flex, caliper mounts flex, pedal arms flex, bulkheads flex etc.

Unless you are on the ragged edge of the system fuctionality, there won't be much, if any, change in the feel from upgrading only a single component such as the brake lines.

That said I use the ss lines, but they are frequently inspected.

The ss is only a sheath protecting the rigid but mechanically vulnerable ptfe inner fluid pipe.

Working line pressure is highly dependant on temp
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Old 01-07-2004, 12:32 PM
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There is no doubt that Porsche OEM rubber lines in new or non-worn out condition are more than up to the job that they do. My original lines were 20 yrs. old when I replaces them and the rubber ones were more $$ than the SS if I recall, so SS it was.
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Old 01-07-2004, 12:34 PM
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Quote:
Originally posted by Bill Verburg
There are quite a few points were hysteresis rears its ugly head. The rubber lines are one, calipers flex, caliper mounts flex, pedal arms flex, bulkheads flex etc.

Unless you are on the ragged edge of the system fuctionality, there won't be much, if any, change in the feel from upgrading only a single component such as the brake lines.

That said I use the ss lines, but they are frequently inspected.

The ss is only a sheath protecting the rigid but mechanically vulnerable ptfe inner fluid pipe.

Working line pressure is highly dependant on temp
Bil,

I would add that teflon tubing (PTFE or whatever) is very unforgiving if kinked. It's strength drops dramatically.

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Old 01-07-2004, 01:30 PM
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