Brake lines - an experiment

[Barry]

I've been thinking about the usual mantra of "steel braided brake lines good OEM rubber lines bad".  

Having the OEM rubber lines I've been naturally inclined not to subscribed to that view so out of idle curiosity I put digital calipers on an OEM rubber brake line and measured the line diameter accurately. I then squeezed the brake lever expecting perhaps to see some small expansion of the line even if only a few thou. Result nothing. I squeezed harder, far harder in fact than I've ever braked in reality; still nothing. The line didn't expand so much as a half a thou.

I assume the reason will be because the brake line outer sheath is all but irrelevant and the inner line (hard nylon ?) is what contains the pressure.

Anyone have a view or are prepared to repeat the experiment.

[Bob_Roller]

My concern, is the rubber getting hardened with age .

I had a front brake failure on my oilhead about 6 weeks ago, the rubber OEM line cracked at the swaged banjo fitting .

This was a 10 year old line .

I've seen over the years, old rubber lines just fail by splitting with no warning of their impending failure .

It is recommended that rubber lines be replaced at least every 5-6 years .

With the cost difference between the OEM rubber lines and aftermarket braided stainless lines, I'll go with the stainless lines every time .

There is no inner liner on BMW OEM lines, it's just rubber, that's on the airhead and oilhead bikes the hose wall thickness is maybe 3 mm thick .

I've cut both open, wondering how they were constructed .

The pressure in an unassisted motorcycle brake system is usually below 200 psi (don't know the metric equivalent) .

[steve hawkins]

It is all about new for old.

And how much you are gonna pay for OEM items against after market.

Everyone likes a bit of bling

Rev. light

[Bob_Roller]

The price difference between OEM and aftermarket lines is usually insignificant, the aftermarket lines for my oilhead cost a bit less than OEM parts .

[georgesgiralt]

Hello !
the problem with rubber lines is that sometimes they peel inside. They, then, make kind of valves preventing the pressure to drop at the calliper.
This cause the brakes to overheat and you're left with no braking power when you need it.
When I was a student, my car experienced this and the right wheel roller bearing broke due to the balls loosing their hardness because of the heat. The disk was bright blue ! (and the rubber line was really short).
A friend of mine has seen a rubber line exploding (the tube split open in all the length ! like someone tried to open it with a sharp knife). The owner had luck, it happened in its garage !  My friend had kept the line on it's workshop for a long time. He then sold a lot of new brake lines ... to everyone seeing the faulty one ......
I bet braided lines have an expiration date also, but I do not know the lifespan of them...

[Bob_Roller]

I inquired as to how long of a service life for braided stainless lines when I replaced the lines on my oilhead .

The response I got was unless they were damaged in some way, you could expect 30 years of use .

I've worked on commercial aircraft for the last 36 years and I've only seen a handful of braided stainless  line failures, most common were failures due to abrasion on the line .

The rest, were at the swaged fittings at the ends .

These lines had been in service for 25-30 years on 3000 psi hydraulic systems .

[marcmax]

All I can add is an anecdotal comment about my brake lines.

I replaced the oem lines with braided stainless lines when I redid my bike recently. I did it mostly for looks but also because the oem lines were old. I also got a good deal when the lines were on sale as part of a group buy.

I have never had any complaints about the dual discs on my LS. I thought they stopped adequately but did notice that the brake lever 'felt' a little soft. It almost felt a little spongy when squeezing the lever.

Once I installed braided lines I can't say I noticed any improvement in braking but I definitely can feel a difference at the lever. It is a firmer feel when applying the brakes

[georgesgiralt]

Hello !
My '82 R65 had double discs and a 15 mm main cylinder. With OEM lines I judged the brake lever too spongy and with too much travel.
One day, I had a leak and it was because the cylinder itself was pitted, so the gasket could not work any more. I then bought a 16 mm diameter cylinder and all was well. Braking became perfect.
Then, last year I decided to put her back on the road and checked everything. New calliper rings, new brake lines (OEM where 30 years old, so... ), this time braided. Now the lever is hard as rock. I am going to have the right hand twice as big ans the left hand ! So I'm considering buying a 15 mm cylinder ....
Maybe the rubber lines expand just enough to make the lever feel spongy and the braided lines do not ?

[Bob_Roller]

With the incessant heat here in the desert, I have replaced all of the brake lines on my vehicles with braided stainless replacements .

The cost was about 15% more than OEM rubber replacement lines for the 4 wheel vehicles .

[Justin B.]

I put all stainless lines (From Moto-Bins) on my '95 RT for actually less than the local stealer, errr, dealer wanted for stockers...

[davidpdx]

It seems like I remember reading somewhere (Snowbum?) that you have to be careful as there are low quality braided line for sale that may be even less durable than rubber.  

[Bob_Roller]

I do wonder about the quality of some of the aftermarket lines .

The supplier that I have gotten my lines from, Speigler Performance, are DOT approved .

They have a lifetime warranty for the original owner .

[Barry]

It seems like I remember reading somewhere (Snowbum?) that you have to be careful as there are low quality braided line for sale that may be even less durable than rubber.  

I threw a similar post into the airheads list and Snowbum did respond on similar lines. He seems not to be a fan of braided hoses and says the BMW rubber hoses are of very high quality.

Quality seems to be the important issue regardless of the materials  of construction.


 

There is no inner liner on BMW OEM lines, it's just rubber, that's on the airhead and oilhead bikes the hose wall thickness is maybe 3 mm thick .

This is quite an eye opener for me as based on Snowbums site I had assumed they contained a plastic liner.


One thing I did learn from the list is that hoses are dated. There is a plastic ring on the hose (yellow in my case) with the date embossed on it. My hose seems to be in perfect condition with no signs at all of the rubber deteriorating. I've also demonstrated that there is no expansion under pressure so I was surprised and not a little shocked to read 09/78 on the plastic ring. The bike was manufactured in October 78 so it fits.

I started this out of curiosity not because I was thinking of a replacement but I will have to consider the available options now.