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Rob McAuley
10-04-2015, 03:59 PM
Well, the 335xi has been sold for parts, and as the shop were pulling out the engine, they checked the brake lines, and saw that the rubber hose had pulled away from the crimped-on metal end.

I'd always installed stainless steel braided brake lines on my other track cars, but figured that this street car wouldn't need it.

http://spin2winracing.ca/picture_library/Brake%20Line.jpg

A few lessons learned:

Stainless Steel Brake Lines do more than provide a firmer pedal.
If you take out the boring, slow chicane (or loop), make sure there is sufficient runoff.
Do at least one hard brake on your warm-up lap before you really need it.
Never let the calipers hang from the brake lines (I didn't do this, but in the future, I will rig up a coat hanger to make it easier to support them without putting pressure on the hoses).

ONdriver
10-04-2015, 06:38 PM
Never let the calipers hang from the brake lines (I didn't do this, but in the future, I will rig up a coat hanger to make it easier to support them without putting pressure on the hoses).

I use a couple meat hooks from Princess Auto to support the calipers when I'm working on it, much more secure than coat hanger wire!
http://www.princessauto.com/en/detail/7-in-meat-hook/A-p8113037e

John P
10-04-2015, 07:58 PM
Most shops let them hang on the brake hose. If the hose can't take it, then it probably needs replacement.

JohnP

terrydale
10-04-2015, 08:46 PM
Most shops let them hang on the brake hose. If the hose can't take it, then it probably needs replacement. JohnP

First, I have been a Licensed Technician for a very long time and letting a caliper hang unsupported on the flex hose is a Basic 101 No No. Not only is it just common sense, it is also something that any competent technician knows not to do. Seeing it done should raise alarms about who you have working on your vehicles rather than being 'proof' that its OK.

Second, if the hose can't 'take it' and one doesn't find that out until the first hard application of the brakes, then that is a very hard way to prove to yourself that you shouldn't have let the caliper hang unsupported on the flex hose during the last service. :eek:

DavidSim
10-04-2015, 08:52 PM
>>I use a couple meat hooks from Princess Auto to support the calipers when I'm working on it, much more secure than coat hanger wire!<<

Thanks for the recommendation, I am going to check these out next time I visit the Princess.

terrydale
10-04-2015, 08:55 PM
>>I use a couple meat hooks from Princess Auto to support the calipers when I'm working on it, much more secure than coat hanger wire!<<

Thanks for the recommendation, I am going to check these out next time I visit the Princess.

Bungie cords - SOP

wings2k
10-04-2015, 10:37 PM
How old were the lines? had the exact same failure on my S2000 a number of years ago, lucky for me the pedal went to the floor at about the very second I was about to release the brake anyways.

I promptly upgraded the lines, but they were at least 7 or 8 years old at the time.

nissannx
10-04-2015, 10:49 PM
Hard lessons.

Stainless lines are good, but they fail also. Brake lines should be on your race car's consumable list and be up for replacement every few years. But inspect them all of the time!

10gt61
10-05-2015, 10:01 AM
Thanks for posting this Rob. It may save someone from a similar experience.
I always have the complete brake system on my car checked before every season, and I do use stainless steel lines. It's fun to do mods to engine, suspension etc. but brakes are of utmost importance and have to be as good as they can be!

kmorris
10-05-2015, 11:19 AM
This brings up a couple of questions:

1. Does anyone have a good guideline on replacement interval for stainless flex hoses? Even with no mechanical damage, the inner rubber hose must deteriorate over time, but how quickly?

2. When people talk about 'checking' flex hoses, what does it mean beyond visual inspection for leaks and visible damage?

Good topic Rob.

wparsons
10-05-2015, 11:32 AM
This brings up a couple of questions:

1. Does anyone have a good guideline on replacement interval for stainless flex hoses? Even with no mechanical damage, the inner rubber hose must deteriorate over time, but how quickly?

2. When people talk about 'checking' flex hoses, what does it mean beyond visual inspection for leaks and visible damage?

Good topic Rob.

I've heard of some people that replace lines annually, I'm personally going to replace my stainless lines this coming spring. They have about 3 years of driving on them, and the better part of 100k km's. They might be plenty good, but ~$100 for new lines is cheap insurance to me.

terrydale
10-05-2015, 11:37 AM
This brings up a couple of questions:
1. Does anyone have a good guideline on replacement interval for stainless flex hoses? Even with no mechanical damage, the inner rubber hose must deteriorate over time, but how quickly?
2. When people talk about 'checking' flex hoses, what does it mean beyond visual inspection for leaks and visible damage?
Good topic Rob.

Checking a non-steel braided hose involves bending it and looking for cracks in the outer rubber covering, looking for bulges, looking for signs of expansion near the fittings. Any doubt means replacement.

Doing any of that on a steel braided line is problematic as everything that has just been described is all hidden underneath the braid.

So, keeping in mind that a hose is built to withstand internal pressure; that it is NOT designed to handle being stretched (by some jerk who leaves it hanging while servicing the brakes); that it absorbs high heat - especially while sitting heat-soaking after a hard run; that it depends on how many times it has been heated and over what period of time (months, years); that rubber deteriorates naturally with age - even while sitting on a shelf; that the only thing that allows your brakes to work is that the hydraulic system can hold the pressure created when tromping on the brake pedal (easily over 1000 psi). So, how often should your hydraulic brake flex lines be changed? In street cars, they typically seem to come due after the second brake friction replacement - or 3 years/100,000km. More or less!!

If in doubt, change them out!! :)

For what its worth from a Licensed Technician with a few decades of experience both street and track.............

Grant Galloway
10-05-2015, 03:35 PM
Thanks for sharing and investigating what actually happened.

They are certain that this happened prior to the crash not during the crash!

I am very anal about checking brakes and run SS lines, I also bleed brakes after every event!

It's a bummer that a $50 part caused this issue, but I'm sure everyone else will be looking at this item in the off season.

Grant

Slowpoke
10-05-2015, 11:57 PM
I always get coated exterior lines and change them every 3 to 4 years depending on usage.

I always have bungee cords for hanging the calipers during service.

Dave Barker
10-17-2015, 09:21 AM
Rob, this kind of failure is related to repeated high pressure in the lines. We have seen it happen twice with OEM lines in our series in the past that I am aware of, once in a Honda product and once in a GM product, neither of which were as well used as yours so I don't think it is a manufacturer specific issue but might be a real concern to those who don't upgrade their brake lines. To be fair, I am sure that if you let the caliper hang by the line it would make things worse.

OTOH, I stand by my statement that if this had happened to your family while driving on the 401 and in a panic stop, the results could have been far worse. Small silver lining to the cloud but.....