A friend recently bought a 2003 V-Rod/Ural sidecar combo. There is a hydraulic disc on the car linked to the rear brake master cylinder.
His problem is that the rear brake won't retain pressure after a few pumps. He did find out that the previous owner had a similar problem that was not resolved completely (even by a Harley dealer).
There are no visible leaks and bleeding the system thoroughly left no indication of air in the lines. When trying to pump fresh fluid through, many strokes on the brake pedal produce only a trickle of fluid at the caliper end.
Questions are:
1. Would using DOT 4 in a DOT 5 system cause any long term problems?
2. Is it possible that the rear master cylinder with only 3500 miles on it after 13 years has lost its sealing ability and needs a rebuild?
3. Could the rear master cylinder be too small to work both brakes? The conversion kit for the Harley sidecar doesn't provide a different master cylinder - just a modification for two lines.
You're not going to like this...
Any or all of those problems is possible.
I'd start at the beginning and make sure the line is clear. First because it's free or at least almost free and it is the least likely problem but needs to be eliminated before you go forward.
Second thing is a rebuild on the master cylinder. The chances are VERY GOOD that with that low number of miles and that much age that the MC is shot. Also, the symptoms fit.
The small MC could be an issue but the symptom there is longer travel on the pedal, not loss of pressure after a few pumps. This is the least likely but if you want to fix the long throw issue an upgrade is usually easy. Take care not to over do it.
Good luck.
If this is running the Ural disk brake wheel, as there is lots of play in the wheel bearings the brakes go away when you go around a corner as the rotor pushes the pistons back in on the caliper. This could be your problem, remember you are using a master designed for single brake and running two brakes off of it, It might not have the capacity. With the Ural wheel we would remove the sleeve between the wheel bearings and adjust the bearings manually. This helps some. If you can not change to a master with more capacity then some thing that helps some is a 2 psi check valve in the brake line to the sidecar wheel. Summit racing and Jegs offer these.
Jay G
DMC sidecars
866-638-1793
www.dmcsidecars.com
When trying to pump fresh fluid through, many strokes on the brake pedal produce only a trickle of fluid at the caliper end.
Sure sounds like the brake line is blocked. That happens when the line is old rubber and has started to break down. After you replace the line, you'll also need to take the caliper apart and flush it out to remove the debris.
Al Olme - 9/29/2016 11:46 PM
You're not going to like this...
Any or all of those problems is possible.
I'd start at the beginning and make sure the line is clear. First because it's free or at least almost free and it is the least likely problem but needs to be eliminated before you go forward.
Second thing is a rebuild on the master cylinder. The chances are VERY GOOD that with that low number of miles and that much age that the MC is shot. Also, the symptoms fit.
The small MC could be an issue but the symptom there is longer travel on the pedal, not loss of pressure after a few pumps. This is the least likely but if you want to fix the long throw issue an upgrade is usually easy. Take care not to over do it.Good luck.
Well, I just heard from my friend - he did the lines and an MC rebuild. Now has perfect brakes. Thanks!
