Hard vs Flexible brake lines

[Fawudd]

This evening, I spent some "quality" time bending some brake line for the front wheel on the squarelight. What started this whole saga was a desire to install the steel braided lines I had sitting around for some time. A couple of the fittings on the hard lines were chewed up by a previous owner, and hence the need to replace one of the hard lines as well....

 

While trying to bend the lines, I wondered why there is a short section of hard line from the caliper in the first place? It goes to a perch on the strut tower, where a rubber line (originally, now steel braided in my case) then goes a short distance to another perch on the fender wall, to connect to a hard line again. I fully understand that flexiblitiy is needed between the wheel with suspension travel and the fender wall, but why not just make a single flexible connection from the caliper to the fender wall? It just seems like unwanted fittings (just waiting to be rounded off) and connections, exposed to the elements and the most corrosive of fluids. If the factory didn't, why didn't the aftermarket just make full steel braided lines? Is the braking performance difference of 12" of hard vs flex that significant ?

 

I also realize that this is not strictly a BMW or a 2002 issue, but I am guessing that the wizards on this forum can quickly set me straight....

Edited March 15, 2019 by Fawudd

[Schnellvintage]

They use the short hard lines to reduce and/or eliminate the stress of the steering movement and suspension movement on the brake caliper connection. The strut mounting does the same for the connections for the flex lines.
With any hydraulics lines....you don’t want any stresses on the connections, which would be prone to leaking and/ or breaking.

Fwiw,
Matt



Sent from my iPhone using Tapatalk

[Simeon]

If you imagine the steering on full left hand lock and at the extreme of suspension droop. Imagine how long the hoses would need to be to get from the hydraulic fitting at the hole in the inner fender to the caliper. Now imagine the slack in those hoses with the steering on full right hand lock with the suspension compressed to the maximum of its travel. This amount of slack (or somewhere between the two extremes) would be dangling around the wheel wells catching on whatever may flow by. 

 

Having the connection to the hard lines on the strut brings the hoses to a central point with the minimum amount of displacement to reflect all states of the steering and suspension. 

[Son of Marty]

The metal lines bleed heat out of the caliper?

 

[TobyB]

because otherwise it would look like my Ferd Truck does.

 

Complete with tire wear on the line.

 

It's also REALLY crowded where the line exits the caliper.

 

Because they always did it that way.

 

t

has more answers, if you need

[tzei]

Braided steel lines all the way to calibers are common practise in race cars. As stated above one should carefully take account line lenghts and support those so no interference occurs any movement situations (as per oe). A banjo fittings might be needed at caliber end.