nitram38
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| posted on 13/3/09 at 10:40 PM |
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Wilwood experts, answers please!
I have wilwood pedals and front powerlite 4 pot calipers with bias set up. My master cylinders are 0.7 rear 0.625 front.
My rear calipers are rover 214 on discs.
The issue I am having is that on first press of the brake, there is a bit more travel as if the powerlite pistons have retracted since last use and
then the pedal is firm on the second press.
The pedal has a bit more travel than I would like but I think this is because of the 0.625 master on the front circuit (bias is right over to
fronts).
I think I have all of the air out but I haven't ruled it out as a cause.
The brakes aren't working well yet, but this is probably because of only taking it up the end of the cul-de-sac and back and they are not
bedded in.
Just for added info, the masters are higher than the calipers and the resevoirs higher still.
Any tips/advice?
Cheers Martin
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nitram38
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| posted on 13/3/09 at 10:47 PM |
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Just got an answer from wilwoods (after I posted!!!!) It might help someone else!
Martin,
Thank you for the inquiry and use of Wilwood Disc Brakes. Yes, for the 4-piston calipers, the 0625 master cylinder is much to small and is not
providing enough volume to the caliper, making it necessary to pump the pedal twice.
With the Wilwood pedal assembly I recommend a 0.75" front master cylinder and a 1" rear master cylinder.
Regards,
MJ
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cloudy
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| posted on 13/3/09 at 10:49 PM |
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Uh oh, same problem i had (only on the front) and I have 625's on front and rear... back's worked fine for me? I'll soon see when
i've fitted the replacement MC's and drive to SVA again...
James
www.warnercars.com
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nitram38
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| posted on 13/3/09 at 10:51 PM |
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I'm going to keep the rears as 0.7 as they seem solid.
Looks like another order...
It's a bit annoying because I bought pedals and masters from rallydesign. Perhaps they should have questioned me?
[Edited on 13/3/2009 by nitram38]
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cloudy
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| posted on 13/3/09 at 10:51 PM |
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Also to add, when its bled through and air isn't getting in my pedal is pretty rock solid with no discernable difference between first and
second press
[Edited on 13/3/09 by cloudy]
www.warnercars.com
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cloudy
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| posted on 13/3/09 at 10:55 PM |
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Inded - Rally design are usually really on the ball when it comes to compatibility....
James
www.warnercars.com
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cloudy
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| posted on 13/3/09 at 11:03 PM |
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You've worried me now, I wonder if the front discs have slightly more runout causing a larger piston retraction in motion than the rear, meaning
you need the double pump to get the pads back in contact. Would explain the issues and why it only appears when the car is in motion....  I could
just get a .7 front, but the bias is already rear enough without making it worse.. Perhaps another two 7's ?
www.warnercars.com
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cloudy
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| posted on 13/3/09 at 11:07 PM |
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Thinking aloud here, it can't be that because once it goes its always like that untill you rebleed even whilst stationary...
You may find it just needs a more thorough bleeding....
James
www.warnercars.com
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nitram38
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| posted on 13/3/09 at 11:09 PM |
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Are you running 4 pot powerlites? Mine are vented discs, but I don't think that it will make a difference.
I would go 0.75 as per my email from wilwood and leave your rears alone.
It also depends what your pedal ratio is, unless you are using wilwood pedals too?
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cloudy
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| posted on 13/3/09 at 11:11 PM |
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Spec is powerlites all round with .625 wilwood cylinders
Custom pedal box, so it may well be different (not that it changes the MC stroke, just the effort)
[Edited on 13/3/09 by cloudy]
www.warnercars.com
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nitram38
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| posted on 13/3/09 at 11:16 PM |
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I've bought my replacement of this
ebay seller.
Seems a bit cheaper than rally design.
I'll let you know how I get on.
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Canada EH!
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| posted on 14/3/09 at 01:10 AM |
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Question, are the pedals floor or top mount?
If floor mount you may need a residual valve to prevent fluid flowing back into the master cylinder.
Residual valve holds about 1-2 lb pressure on the caliper preventing drainback.
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nitram38
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| posted on 14/3/09 at 06:15 AM |
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Top Mount.
I think the volume was the problem.
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goaty
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| posted on 14/3/09 at 09:02 AM |
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i have ordered .7 front and .625 rear for mine, running Midilites up front a sierra discs on back....Hope they are ok, dont fancy spending more on
brakes.
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greggors84
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| posted on 14/3/09 at 10:59 AM |
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quote:
Originally posted by goaty
i have ordered .7 front and .625 rear for mine, running Midilites up front a sierra discs on back....Hope they are ok, dont fancy spending more on
brakes.
The smaller diameter MC creates more pressure than larger one so normally you have this on the front. It depends on the sizes on the pistons in the
rear calipers, if they are close to the size of the fronts you may end up with lots of front bias to stop the rears locking up.
You should be ok using 4 pots on the front compared to the single piston sierra rears but it is a big single piston.
Edited to say that if the .625 dont move enough fluid for the 4 pots then it maybe worth keeping it that way round and at worst you might end up
winding a bit more front bias on.
[Edited on 14/3/2009 by greggors84]
Chris
The Magnificent 7!
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nitram38
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| posted on 14/3/09 at 12:26 PM |
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I have two 0.625 wilwoods for sale 
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britishtrident
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| posted on 14/3/09 at 05:03 PM |
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Its a caliper problem to each caliper body clamp a dial gauge with the stylus touching the disc and measure the deflection when you pump the pedal
it should be zero.
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daviep
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| posted on 17/3/09 at 02:57 AM |
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quote:
Originally posted by nitram38
Are you running 4 pot powerlites? Mine are vented discs, but I don't think that it will make a difference.
I would go 0.75 as per my email from wilwood and leave your rears alone.
It also depends what your pedal ratio is, unless you are using wilwood pedals too?
This is why I love forums..... The person who has set up his system incorrectly is advising other people. Classic
If you're brake balance is good and the bias is already adjusted all the way to the front if you only change the front m/c then your balance is
going to move to the rear and you won't be able to adjust it towards the front.
If the balance bar started off all the way towards one end then it would suggest to me the your setup was specced wrongly to begin with. Fitting a
larger m/c to the front is only going to compound the problem.
Davie
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nitram38
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| posted on 17/3/09 at 04:53 AM |
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Sorry if you think I'm wrong, but I have taken the advice directly from wilwood technical, the people who make the pedals/brakes I am using.
I'd best give them a call to tell them they are wrong................
They have advised that a 0.625 master is definitely too small for powerlites and recommend a 0.75".
You are right about the ratio of the fronts being smaller as they recommend a 1" cylinder for the rears, if you are using wilwoods.
My rear brakes are rover so are different to wilwoods and so a 0.75 is fine.
My fronts need one press to bring the pads forward and a second press for them to work correctly, the volume of the master is too small.
I think Cloudy will need a 0.75 for his fronts to work correctly.
As to advice from someone who has got it "wrong", why is this a problem?
People who do nothing, never make any mistakes, but it is by making mistakes we find out about things.
Rally design supplied my pedals, calipers and master cylinders. I went by their recommendations.
I'd best give them a call too...........
[Edited on 17/3/2009 by nitram38]
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MikeRJ
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| posted on 17/3/09 at 08:17 AM |
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The point daviep is making is if your bias bar is already adjusted fully to the front it suggests the rear master cylinder is already too small.
Fitting a larger diameter master cylinder to the front will exacerbate the situation, and you won't be able to achieve the correct balance
unless you also increase the size of the rear master cylinder.
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nitram38
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| posted on 17/3/09 at 10:56 AM |
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You are probably right but since changing the front mc is cheaper I want to take it step by step. I have never seen a 1? mc anywhere!
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MikeRJ
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| posted on 17/3/09 at 11:15 AM |
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I've not seen the common Girling type in 1" either, though Rally Design do sell them with 0.813" bore.
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Doug68
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| posted on 17/3/09 at 01:36 PM |
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Wilwood make 1" dia and bigger, I got mine from:
http://www.carshopinc.com
They were roughly US$55 each from memory.
You may get screwed at the current exchange rates though.
Doug. 1TG
Sports Car Builders WA
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daviep
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| posted on 17/3/09 at 04:02 PM |
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quote:
Originally posted by nitram38
You are probably right but since changing the front mc is cheaper I want to take it step by step. I have never seen a 1? mc anywhere!
Brakes and Steering are probably the two systems which need to be designed properly in order to be intrinsically safe.
To make your brake balance incorrect in order to save a few quid just seems stupid to me.
If having to much rear braking is a problem then maybe you should be looking at changing the rear calipers to something with a smaller piston area
rather than bodging to try and remedy what appears to be a design flaw in the ratio between front and rear caliper sizes.
Davie
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daviep
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| posted on 17/3/09 at 04:18 PM |
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quote:
Originally posted by nitram38
Sorry if you think I'm wrong, but I have taken the advice directly from wilwood technical, the people who make the pedals/brakes I am using.
I'd best give them a call to tell them they are wrong................
No you're not they advised the use of a 1" rear m/c. Which you ignored
They have advised that a 0.625 master is definitely too small for powerlites and recommend a 0.75".
You are right about the ratio of the fronts being smaller as they recommend a 1" cylinder for the rears, if you are using wilwoods.
My rear brakes are rover so are different to wilwoods and so a 0.75 is fine.
Doesn't sound like it's fine to me if the bias is all the way towards the front.
My fronts need one press to bring the pads forward and a second press for them to work correctly, the volume of the master is too small.
I think Cloudy will need a 0.75 for his fronts to work correctly.
As to advice from someone who has got it "wrong", why is this a problem?
The fact that you designed your system incorrectly suggest to me you possibly shouldn't be advising others..
People who do nothing, never make any mistakes, but it is by making mistakes we find out about things.
Rally design supplied my pedals, calipers and master cylinders. I went by their recommendations.
I'd best give them a call too...........
If you gave them all the relevant data to be able to spec your system correctly then I would give them a call. However in your own words
"It's a bit annoying because I bought pedals and masters from rallydesign. Perhaps they should have questioned me?" It sounds like
you ordered specific components..
[Edited on 17/3/2009 by nitram38]
I am only trying to help you build a safe car. I don't know why you feel the need to answer with sarcatic comments. The title of the thread is
"Wilwood experts, answers please" pretty pointless asking a question you don't want to hear the answer to.
Cheers
Davie
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