Brake problem...........

[Manky Monkey]

If you've got both discs & drums I'd say one to front & one to back.

[terry t]

are you using a dual brake circut system.

[ROD]

No ,one m/cyl powering all 4 brakes

[Olds]

I assume it's a Girling style integral reservoir master cylinder.
One 2psi rpv in the line before it splits to front and back should be ok.

[terry t]

No ,one m/cyl powering all 4 brakes

so its one pipe out off m/cyl to a two way splitter to the front and rear.

[ROD]

Yes thats correct Terry.
 Today I experimented........ shut the balance valve to the rear brakes,then depressed the pedal,appears to need less travel to operate the front brakes.I then opened it about 3/4 of the way. This caused the nose to dive and lock up,but I still had to double pump the pedal to do this. My thoughts are that the bal valve should be fully open to allow the rears to brake first,or at very least all brakes come on together.But with valve fully open I still have to double pump to get a bit better pedal. You can actually see that the second pump doesnt allow the rod operating the cylinder to go in as much,so I think it needs a larger (7/8"?) bore m/cyl,a good bleed out,and then if prob persists I will get the residual valve in line as per ON's post.Would I benefit from a higher (remote) mounted reservoir to maintain a 'head' of fluid,or does it only matter that the height of the actual m/cyl bore should ideally be higher?

[terry t]

so is the hand brake easy to get at when riding

[ROD]

   Are you trying to tell me summat Terry? 

[Olds]

Try bleeding first as that costs near nowt. Bleed with valve fully open.
A remote reservoir will help but I believe it should be as high as the highest pipework(not sure)
I would have thought that on a trike, if you are going to fit a balance valve it would be in the front line to prevent front end lock up.
Locking up the rears can be very entertaining while locking up the front can be very frightening.
I rarely use the front brakes,  (twin Z1000 discs) but its good to know they are there when I need to stop a bit fast.

[terry t]

  Are you trying to tell me summat Terry? 

no Rod just curious. if you could reach the hand brake if the main brake failed 

[ROD]

Yes not a problem to reach,very accessible!
 
 O N ...yes,good idea, I will try bleeding them tamara. If that fails,apparently theres a Land Rover place a few miles away who does all the cylinders,so will run over there to get a 7/8 bore one.

[ROD]

Ive now bled the brakes,but still have the same" double pump to get good brakes ",symptom. Ive looked at adjusting the Golf calipers to allow the pads to be closer to the disc,but they seem ok. Ive tried pulling the handbrake on one notch ,thinking it would take up the wear in the pads,but it still needs a double pump.The larger bore m/cylinders dont appear to come in the integral reservoir type (remote only) . Wheres the best place to get residual pressure valves?

[Olds]

http://www.cbsonline.co.uk/
They do integral master cylinders in 0.625"  0.7" & 0.75"
or separate reservoir kits in 0.625" 0.750" 0.875" & 1.0"
& 2lb residual pressure relief valves
Probably not the cheapest place. Their catalogue is worth having just to show what's available and for ideas.
If the problem exists with the handbrake on it suggests that the trouble might be with the front. The brake line probably goes up from the master to a splitter near the headstock before going back down to the callipers. This can be really difficult to bleed fully. Ideally you should get the brake line as near to level as possible, or take the callipers off, and bleed with them higher than the splitter, as any air will try to go to the highest point.

[ROD]

Thanks ON ,all the things Id thought of too! CBS are very cheap for the cylinders.Im going there tomorrow to pickup a residual valve. I'll fit it immediately after the m/cyl and see what happens then. Rally Design in Kent have a good article on their site about all this. I rang them with the problem and explained that the splitter on the headstock was the highest of all the pipework, and they didnt think a larger m/cyl would help much. They suggested a R.V. as a start.Their article suggests that if you put the reservoir high it will help,but he said that even if this was done on my system,it still wouldnt give enough 'head' of fluid to push the fluid up to the highest points. OK in a car where all the lines are more or less on a horizontal with the m/cyl.
  Roughly speaking the dimensions,using the floor as a baseline are..
 m/cyl to floor 6"
 caliper tops to floor 15"
  Headstock splitter to floor 24"
 
 I have a bleed nipple at the headstock,actually on the splitter,but it didnt seem to be releasing any air when I bled the system.
 
 I'll keep you posted!
 

[ROD]

Today I received the RPV from car Builder Solutions,great! Took pipe off trike(brake fluid discovered on frame ..see other post in Gen Section.) Dug out my pipe flaring tool..bu**er!.. A part is missing for the tool! It was only a cheapo one,and didnt work succesfully previously,but I thought I might get away with making 2 flares,especially as Im doing it on the bench ..had to order a new tool from amazon,different design this time..so more waiting! At least Im a bit nearer solving the problem.