nitram38
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| posted on 17/3/09 at 04:20 PM |
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What are you on about?
I have spent £19k on this project and i'd rather not spend money on extra parts just on your say so.
My brakes will be proven on the sva rollers, so what is your issue?
You don'know the capacity of rover rear callipers so what do you suggest? Maybe I should quit building until I get my slide rule out?
What you can be sure of is there will not be any problems left on my car. I'm just taking sensible steps.
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cloudy
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| posted on 17/3/09 at 04:43 PM |
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I can add that 0.625/0.625 is now working fine for me, It was either faulty MC or vibration induced air ingress - The maximum braking effort is
achieved well within the stroke...
Playing devils advocate - willwood's advice may well have been latching onto a potential problem you primed them with?
www.warnercars.com
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daviep
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| posted on 17/3/09 at 05:28 PM |
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quote:
Originally posted by nitram38
What are you on about?
I don't know why you are being so aggresive? All I'm on about is how I interpret the facts. It sounds as if you have too much
braking on the rear as suggested by the balance being all the way to one end. A well designed system should have the correct balance with the bias bar
roughly in the cntre of it's adjustment. I'm only making the suggestion that possibly the ratio between the front and rear calipers may be
wrong.
I have spent £19k on this project and i'd rather not spend money on extra parts just on your say so.
I'm not asking you to, I'm suggesting that you look at what is causing the problem and not just at the symptom..
My brakes will be proven on the sva rollers, so what is your issue?
It's a bit like the self centering issue, you can make a car self center by toeing out and dropping the tyre pressures but that
doesn't make it right.
You don'know the capacity of rover rear callipers so what do you suggest? Maybe I should quit building until I get my slide rule out?
It would have been the sensible thing to do before purchasing any components.
What you can be sure of is there will not be any problems left on my car. I'm just taking sensible steps.
Don't be upset I'm only offering an alternative opinion.
Regards
Davie
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nitram38
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| posted on 17/3/09 at 06:23 PM |
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So what if you said I should buy a 1" MC and I don't need one, then I have wasted my money.
The wilwood email assumed I was running wilwood rears, so I don't want to base my buying on that.
All I wanted to do is change the fronts first and re-check my brakes and if neccesary change the rear MC.
I don't need comments about me having to design a system before I start as all I and most people have, is standard parts to work with.
I don't have the facility to create a 0.937 MC if it is needed so I have to buy what is available.
Cloudy has already proved that a 0.625 works with his set up, but he has probably got a different pedal ratio.
I feel like I have taken a caning for finding out and trying to pass the information on.
[Edited on 17/3/2009 by nitram38]
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cloudy
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| posted on 17/3/09 at 06:26 PM |
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The pedal ratio won't affect the amount of fluid pumped per press unless you are artifically limiting the travel somehow...
I can only put your problems down to high runout on your front discs or the fronts needed more of a bleed (The powerlites are a bitch to bleed, they
seem to retain air all over the place and the bleed nipples need more force than you'd think to seal off)
James
www.warnercars.com
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nitram38
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| posted on 17/3/09 at 06:28 PM |
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Wilwood say that with the wilwood pedals, 0.625 is too small.
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cloudy
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| posted on 17/3/09 at 06:34 PM |
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If you push the pedal without fluid, what bottoms out first? the pedal or the MC? If it's the MC I can't see the pedal choice making a
blind bit of difference....
James
[Edited on 17/3/09 by cloudy]
www.warnercars.com
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nitram38
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| posted on 17/3/09 at 07:21 PM |
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My cylinder doesn't bottom out.
First press and the brakes work, but they work better after that
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britishtrident
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| posted on 18/3/09 at 08:26 AM |
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The ammount of brake fluid the mastercylinder has to displace to make the calipers bite the disc should be really tiny --- properly setup the pad to
disc clearance should be almost zero say 0.01 to 0.025mm.
Taking a 0.625" (16mm) master cylinder operating a pair of Cortina or Sierra calipers as an example then the piston in a 0.625" cylinder
will require to move about 45 times the pad to disc clearance. Doing the sums that works out at very close to 1mm ! If the pedal leverage is say 6
to 1 then that is 6mm at the pedal pad --- not exactly a lot.
If the replacement calipers aren't massively bigger in terms of total piston area then these numbers don't alter much.
Even fitting massively bigger calipers with a 50% increase in caliper piston area won't result in more than 1.5 mm at the mastercylinder or 9mm
at the pedal.
However if something else is wrong such as the caliper is not mounted squarely or i has trapped air or the caliper is flexing then it is a different
ball game -- still using calipers with the same area as a cortina or Sierra if the pad to disc gap increases to 0.5mm (0.02" then the
required movement of the master cylinder is now about 22mm or 132mm at the pedal pad ----- a little bit excessive.
If all the air is out the system and the wheel bearings are in correct adjustment large pedal movements on the first press sugest flexing in the
system.
It would be productive to do a dial gauge delfection test on both the caliper mountings relative to the disc and the flexing of caliper body, --- .
That Wilwood seem to automatically recommend very big bore mastercylinders makes me suspect the defelection results for the flexing of the caliper
body would be of interest.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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cloudy
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| posted on 18/3/09 at 08:47 AM |
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Britishtrident - excellent reply...
My problem turned out to me badly seated bearings in the alloy cortina hubs, giving a runout of around 0.5mm... (Same symptoms as you martin)
I seem to remember your uprights were homemade, did you make the caliper mounts yourself? Are those dead square?
James
www.warnercars.com
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nitram38
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| posted on 18/3/09 at 09:32 AM |
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The caliper mounts were welded on the uprights then milled so that they are true to the disc/hub.
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cloudy
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| posted on 18/3/09 at 09:36 AM |
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As BT says, might be worth measuring the runout - If even you just do as I did and fire a laser from almost dead behind the disc just glancing it.
It'll show up even the most minute variance 
James
www.warnercars.com
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nitram38
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| posted on 19/3/09 at 05:33 AM |
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I will re-check the runout. My 0.75 arrived yesterday and I swapped it out. Tonight I will try and bleed the brakes.
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cloudy
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| posted on 19/3/09 at 09:14 AM |
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Good luck
www.warnercars.com
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nitram38
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| posted on 19/3/09 at 06:44 PM |
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I bled the front brakes tonight and now they are spot on.
I even got to move the bias over a bit to the rears. 
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cloudy
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| posted on 19/3/09 at 06:51 PM |
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Result
www.warnercars.com
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nitram38
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| posted on 19/3/09 at 08:02 PM |
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quote:
Originally posted by cloudy
Result
Just as well I didn't buy that 1" MC isn't it!
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daviep
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| posted on 20/3/09 at 04:26 AM |
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Congratulations
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robv
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| posted on 31/3/09 at 07:07 PM |
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Out of interest, what size pistons do you have in your powerlites?
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nitram38
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| posted on 31/3/09 at 07:11 PM |
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Pass......
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nitram38
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| posted on 2/4/09 at 10:25 AM |
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Just an update, the brakes started being soft on the first press in the morning after it had been standing.
I contacted wilwood who said that some calipers have round seals that will pull the pads back from the disc.
I've bled them to death so I tried the block of wood on the pedal overnight trick and for the last 2 mornings, the pedal is back to spot on.
Might help some of you with those last few small air bubbles...........
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ghostrain
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| posted on 4/4/09 at 01:18 PM |
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Wilwood experts,answers please
I don't normally respond to posts but there is so much confusion on this post that I felt compelled to respond.
I assume that enquiries to Wilwood you mean Wilwood Europe ie Rally Design not Wilwood USA?.
Before anyone at Rally Design can give a sensible answer on recommended master cylinder sizes on a balance bar system we need the following info-
1. The type of vehicle-FWD,RWD,4WD,Front Engine,Mid Engine etc etc?
2 Type of caliper-4 pot,2pot,single pot slider etc etc?
3. Caliper piston size?
4. Pedal ratio?
I am only posting because Nitram38 last post suggests in answer to Robv's question 'what size pistons in the Powerlites' he answers
'pass'-do I read into that don't know. If he doesn't know his piston sizes I just cannot see how we at RD could advise master
cylinder sizes.
The sizes of 0.75 and 1.0 are very unusual for these type of vehicles,I would like to know what info you supplied to my guys to respond with these
sizes.
Anyway while I am posting the following may be helpful.
The largest pistons available on the Powerlite caliper are 1.38" with a 4:1 pedal ratio the ideal master cylinder size is 0.56" which
unfortunately is not cheaply available(but RD is considering manufacture),0.625 is good on a 5:1 pedal ratio and 0.7 is good on a 6:1 pedal ratio.
I don't know the size of the pistons in the rear Rover calipers....were these calipers off the front or rear of the donor Rover?-we are often
horrified at work when we are asked to quote m/cyl sizes when front calipers are used on the rear of these lightweight cars...a popular mod is front
XR3i calipers/discs bolted onto an English rear axle,they bolt on easily but the effective swept piston area is very high(calculate 3.142xpiston
radiusxpiston radius x 2)we sometimes have to recommend 0.813 or even 1.0 master cylinders on the rear circuit but this is to overcome a bad caliper
selection better to use smaller piston sizes in the first place.
All this misinformation is one of the problems of these forums....if you supply insufficient or wrong information you cannot expect to get a helpful
answer and then everybody puts in their input and the error gets confused and compounded....if Nitram38 gives me the info as above I can give a
sensible answer.
The Wilwood balance bar set up in the Rally Design catalogue is very helpful in setting up the balance bar-it is rarely at right angles at rest,the
longer pushrod is normally on the front circuit.
Hope this helps .
Senior brakes designer,Rally Design
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nitram38
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| posted on 4/4/09 at 01:29 PM |
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Thanks for the clarification.
The trouble with brake systems is there are so many permutations for the amateur and even when everything is accounted for it is not working.
By talking on here, hopefully we learn and others can benefit from our mistakes.
TBH I wouldn't buy wilwoods again because of all the issues I've had with threads (had a leak on the tapered inlets of both caliper) and
the dual chamber bleeding which is a PITA.
I am using the rover rear calipers on mine and not the wilwoods. This also was why wilwood (usa) suggested a 1" cylinder?
Anyhow, mine seem to feel right on 0.75 and 0.75.
The fronts lock before the rears.
The sva rollers will be the final judge!
[Edited on 4/4/2009 by nitram38]
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cloudy
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| posted on 4/4/09 at 01:38 PM |
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Be interesting to compare, I'll scan the 2 page brake report the SVA man kindly gave me (you have to request it)
James
www.warnercars.com
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ghostrain
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| posted on 4/4/09 at 01:40 PM |
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Explains all-I did not appreciate that your enquiry was to Wilwood USA...out of interest what piston sizes(front and rear) and pedal ratio did you
advise to them?
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