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Spent some time this weekend bleeding my brakes for what seems like the nth time. They're pretty good at stopping but I'd always remembered my stock brakes as having a harder pedal.
My belief is that there has to be an air pocket above the top rear piston. Here's a caliper installed and the blue tape is the diameter of the real piston cylinder and where logically it would be located.
The green line is where I would imagine they've drilled down the bleed screws. This is all supposition but it would seem there has to be air above the highest part of the line I drew.
Loosened the bolts and angled the caliper like so:
not perfect but better. I opened the bleed screw and eyeballed the fluid coming out as I pushed on the brake pedal with a stick. It sure seemed like air came first, then brake fluid.
Nowhere have I seen any special instructions about bleeding these things on the car. Am I wrong in my thinking?
p.s. the pedal seemed like it got harder but that is all subjective!
I'd do the same thing, again, and this time tilt the outer side of the caliper upward, just in case there is an air bubble trapped in the back of the bore. Tap the caliper a few times (lightly) with a screwdriver handle to get the bubble to move toward the bleeder. Not much else you can do. Good luck.
Duane
I'll stop short of say "it does" to "it should" state in the instructions that the lay over mount will require you to remove the caliper for bleeding. For the exact reason you show. Put some plywood in there of course to keep the pistons from coming out.
Once properly bled it won't be so import in the future for flushing it so long as you don't allow air to suck back in. Or boil it..but I doubt you'd see that.
I'll stop short and say "it should" state in the instructions that the lay over mount will require you to remove the caliper for bleeding. For the exact reason you show. Put some plywood in there of course to keep the pistons from coming out.
Once properly bled it won't be so import in the future for flushing it so long as you don't allow air to suck back in. Or boil it..but I doubt you'd see that.
Yep, I had to do the same as you. A real pain in the azz since I also had to shim the calipers to center them on the rotor. So when I remove the caliper I also have to remove and replace the shims. I really can't understand why they let a couple things like this move these calipers from a fantastic product to a mediocre product.
All they had to do is copy the bleeder setup of the stock calipers.
You can also see on these pictures why the emergency brake cable is too long with the Global West trailing arms. You can see how they moved the bracket closer to the halfshafts. Another case of shoddy engineering making a great product only mediocre.
Yet another GW fix comes to mind looking at your picture. I had to extend the rubber bump stop to keep my shocks from bottoming out. That doesn't show in my picture but look at the little rubber o-ring tell-tale on the shock rod. Gets pretty close. Those are adjustable Vari-Shocks. the story of installing those would be another thread's worth. The need for that extender may be the shocks and not the TA's. Hard to separate which is the real offender.
I talked to Wilwood at SEMA about how they screwed up their caliper design, they weren't interested in what I had to say. If someone wrecks their Vette with these on them, they would have a good liability suit on their hands. Maybe follow Dave Herlinger's instructions on how to gravity bleed your Vette with the calipers unbolted and the bleeder screw sitting at the top of the caliper so it completely fills with fluid....yes there is an air pocket left if you try to bleed them bolted in place.
I am assuming that most of you going to Willwood brakes are making the conversion for the weight savings and better heat rejection over the stock iron calipers for road racing....brake performance will be no better than the stock 4 piston GM calipers with the 12 inch rotors. There have been quite a few test articles and a forum member that tested brake performance on the street with the Willwood 4 piston calipers and stock size rotors versus the GM calipers/rotors...no difference in stopping distances which is not surprising since the Willwood system with 4 piston calipers and 12 inch rotors is the same design as the GM system but in aluminum. The only way to decrease the C3 brake distance is to use a bigger rotor like the 13 inch front rotor AND/or 4/6 piston front fixed willwood caliper. I never quite understand why folks go through all the effort to change the C3 brake system which is terrific for the street, racing is different.
I am assuming that most of you going to Willwood brakes are making the conversion for the weight savings and better heat rejection over the stock iron calipers for road racing....brake performance will be no better than the stock 4 piston GM calipers with the 12 inch rotors. There have been quite a few test articles and a forum member that tested brake performance on the street with the Willwood 4 piston calipers and stock size rotors versus the GM calipers/rotors...no difference in stopping distances which is not surprising since the Willwood system with 4 piston calipers and 12 inch rotors is the same design as the GM system but in aluminum. The only way to decrease the C3 brake distance is to use a bigger rotor like the 13 inch front rotor AND/or 4/6 piston front fixed willwood caliper. I never quite understand why folks go through all the effort to change the C3 brake system which is terrific for the street, racing is different.
And they LOOK good!!!
True- same surface area-and I have seen/re posted "Hotrod427s" test/comparison.
I did go w/ bigger rotors in front- 14"- which made a lot more sense than the 13" for only a $100 or so difference in price.
I never quite understand why folks go through all the effort to change the C3 brake system which is terrific for the street, racing is different.
Absolutely agree the stock brakes are pretty damn good. My reasons were in order
weight - my car is under 3000 #'s
better braking - a little better with the six piston fronts
rally wheels - just in case I want to get that look back
As to the caliper shimming. I added washers to the mounting bolts to back them out a little. The calipers could be shimmed to center them a bit but they look OK.
And for the record from a previous post it is easy to get confused about which front caliper to mount where, as two of the 6 pistons are larger. Should it be leading or trailing? Mine are wrong I can't remember which way is wrong but they need to be swapped, left to right. Still haven't gotten around to that. Haven't seen any adverse effects on pad wear (yet).
I doubt anyone is going to crash their car as a result...appears they'd never get out of the garage...
The rear caliper kits do come with 8 washers to address the bolt length. Being 1.50" long and the need for 1.375...which other than perhaps the oe bolts (if the same pitch) is just not something your'e going to readily find. Thus two washers under each head.
The centering issue I can't truly speak too. However....
I do note many other after market parts on the car in question. Anything would or could move either the axle off center (an alternate dif perhaps) different than oe axles, alternate spindles, maybe even the lack of dust plates...can all contribute to the centering issue. Even the possibility that the rotors in use (Wilwoods??) are not identical to the stock parts.
I'm not saying your wrong in your thoughts but before waving the quality control flag lets fully compare apples to apples and identify the exact cause. Right now we simply have a highly modified car needing some adjustments. Not too uncommon on such projects.
As we've stated many times before: the change in calipers, despite going to six vs four pot fronts is not a measurable change in brake torque. These are simply replacement parts not meant to do anything with bias, rotor torque etc.
The six is nearly identical in piston area (clamping) but spreads the load bit better to control tapering. The proper placement of a larger piston on any such caliper is the trailing edge. This compensates for the boundary layer build up by the leading edge and clamps a bit harder at the end as the rotor passes by.
Installing them wrong will lead to a number of issues including rapid wear and possibly a bound up or stuck piston later as a result. Not good. Pay attention here.
If not..well we have a thread like the one in the Focus ST board: about Problems with Wilwood DP6 Calipers. Which of course started to go off course to read like many others to be poor product..bad design...yada, yada. This is how it start usually. The result: he had installed them incorrectly. (I gave him two new pads for his next track day for his humble apologies to the readers)
Todd: Would slowly pushing the pistons all the way back push all the air out? Have to be careful not to overflow the MC of course.
Hmm. If there is air in it now I'm not sure I'd try that on the risk of pushing the air back into the hose. I guess the company answer is just take a bit of time and do it right. Despite the design and hassle to remove it (yeah I get it) but not doing it is always going to result in a soft pedal. Wedge something between the pads when off or pivoted and put them 'up' to be safe.
Not a real common thing but others do this also. It was standard on Stohr C-sports and a hassle there also~
Hmm. If there is air in it now I'm not sure I'd try that on the risk of pushing the air back into the hose. I guess the company answer is just take a bit of time and do it right. Despite the design and hassle to remove it (yeah I get it) but not doing it is always going to result in a soft pedal. Wedge something between the pads when off or pivoted and put them 'up' to be safe.
Not a real common thing but others do this also. It was standard on Stohr C-sports and a hassle there also~
Ahh, forgot to mention I have speed bleeders. I would open the speed bleeders and push the pistons back. The hose is way down low so I think an air bubble would go out the bleeder. It depends on where the bleeder hole is in the cylinder. Once the piston goes past the bleeder hole then the air is trapped. I do not think it is possible even with that to get all the air out without standing the caliper up vertically.
I looked at the long previous post on this just now
and a lot of this was covered previously. This particular subject, bleeding the rears, was brought up then but I just finally got around to revisiting the rears so I thought I'd start this thread to home in on that.
It seems to me that as long is there is air in the rears the designed-in proportionality is incorrect and the fronts are doing more of the braking.
And as to swapping the fronts (again), well another day perhaps.
05-18-2015, 08:14 PM
Bleeding Wilwood direct replacement rear brakes
DSCN5197 by Richard Hayes, on Flickr
DSCN5198 by Richard Hayes, on Flickr
DSCN5199 by Richard Hayes, on Flickr
DSCN3920_zps92fb8c93 by Richard Hayes, on Flickr
