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I'm not happy with results of front brake line replacement. What next?

BrianG

Member
Member
I have just replaced the stock from brake lines with the Spiegler 2-line set from Murph on my '95 C10 and I don't notice any difference in lever feel. There is still lots of travel and there isn't the firmness I expected. There aren't any leaks at the banjos and I feel pretty confident in my bleed job having pumped about 8 oz of fluid through and not seeing any air for three cycles on each side (I use the squeeze lever>loosen valve>tighten valve>release lever>repeat method). What do I do now?
 
If the lines were just replaced on a 27 year old motorcycle you are very lucky they have not burst by now. The new braided lines are a lot tougher and stronger than the original lines. First of all they will not dry rot. They will stop the bike faster and hold pressure a lot better. You need a Mighty vac to bleed the brakes properly. The lines Murph sells are top quality and he has sold hundreds of sets. I will be buying a set soon myself from him. Get a Mighty vac and re-bleed the job it will make a difference. I used to do it the old fashion way as you did until a friend helped me one time with his Mighty vac it does make a difference try it.

Dean
 
You still have air in the system would be my guess. The air that accumulates on the sides of the lines is in the form of extremely small bubbles.
Oil ( hydraulic fluid) will not compress, period, air does. If you master cylinder is working correctly, your calipers are not leaking , and your lines arent expanding, you have air in your system . I can guarantee you Spiegler lines are not giving up pressure due to expansion.
Tie the clutch lever to the handlebar, leave it over night...when you think about it, give the lines a little smack. See what you have in the morning...
I've had bikes that took a few days of bleeding to get all the air out...

Murph
 
IIRC, there are a few items in the COG website Tech Index regarding bleeding C10 brakes that may be worth reviewing.
 
The C10 has cheap/crummy brake calipers - sliding pin type, to be exact. They flex and that causes excess lever travel compared to better designs.

All that being said, you probably still have air in the system somewhere and I'd first be looking at where the lines attach to the master cylinder. Those union bolts are very good at trapping small quantities of air.

Put the bike on sidestand and move the handlebars all the way left to create the steepest escape angle for trapped air. Being sure the fluid in the master cylinder reservoir will not spill, remove the cover. Gently tap on the union bolts with a suitable tool (screwdriver handle works great) a few times and then s-l-o-w-l-y pull in the brake lever. Your reward for all this would be seeing air bubbling up through the fluid. Rinse and repeat until no more bubbles escape.

If you pull in the brake lever too fast you'll create a fountain of brake fluid. That's bad.

Some people advocate for firmly applying the brake lever and bungy-cording it that way overnight as a way to rid the system of air. I've not ever tried this myself and have had good luck with the procedure I described above.
 
Thanks all. I'll see what tomorrow brings after compressing the lever overnight and tapping the lines and upper banjo regularly until I go to bed.
An unknown to me is how to tell if the master cylinder is working properly.
 
I had to do the tie the lever back on my 98 when i switched to braided lines. It works, leave it set that way over night...
 
The C10 has cheap/crummy brake calipers - sliding pin type, to be exact. They flex and that causes excess lever travel compared to better designs.

All that being said, you probably still have air in the system somewhere and I'd first be looking at where the lines attach to the master cylinder. Those union bolts are very good at trapping small quantities of air.

Put the bike on sidestand and move the handlebars all the way left to create the steepest escape angle for trapped air. Being sure the fluid in the master cylinder reservoir will not spill, remove the cover. Gently tap on the union bolts with a suitable tool (screwdriver handle works great) a few times and then s-l-o-w-l-y pull in the brake lever. Your reward for all this would be seeing air bubbling up through the fluid. Rinse and repeat until no more bubbles escape.

If you pull in the brake lever too fast you'll create a fountain of brake fluid. That's bad.

Some people advocate for firmly applying the brake lever and bungy-cording it that way overnight as a way to rid the system of air. I've not ever tried this myself and have had good luck with the procedure I described above.
^This. Pay particular attention to twisting the bars and slowly squeeze the lever. You will likely get quite a bit of bubbly action.

BTW, I have gone through a pint or more when filling the pipes. I'll go through almost all or all of a 12 oz bottle just purging the fluid in both systems as part of my preventative maintenance regimen, not even bleeding air out.

BTW, OP, are you sure that you do not have a master cylinder issue? A required rebuild would not be out of the question on a twenty odd year old bike.
 
Bfluet, I suspect just a bit of air trapped in the system. Just asking (below) in case there is an underlying issue.
(A C-10 can be a PITA to get all the air out)

It would help us to know why you changed the brake lines?
ie; Were you having issues?
I understand their old and you wanted to do so, but were there issues going on?
 
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Brake lever feel is much better now. First I removed the master cylinder cover and diaphragm then tapped the brake lines bottom to top every half hour for two hours. Brake lever feel improved but I still wasn't happy with it so I put the diaphragm and cover back on and then compressed the lever and tied it in place overnight. This morning the level feel is how I expect that it should be. I'll be taking it for a ride later today. Thank you all for the advise.
It would help us to know why you changed the brake lines?
ie; Were you having issues?
I understand their old and you wanted to do so, but were there issues going on?
The lever had become really spongy and I couldn't resolve it with my bleed attempts so I suspected the old lines were bulging.
 
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