Wilwood brake issue

I finished my roadster about 4 years ago and admittedly I don't drive it a lot (currently at 2600 mi, and car is stored from Oct-May each year). Issue began about a year ago when I noticed after not driving it for 5-6 weeks when I first got in and pressed on the brake the pedal initially would slightly "stick" as I pressed on it and then would seem to be fine although the pedal pressure seemed rather hard. Took it out for a drive recently and came to a light after a stretch of 55 mph road and as I pushed in the clutch the car had significant drag as if the brakes were being applied. Pulled over and felt all the calipers/rotors and the front calipers were too hot to touch. Sat there for about 90 min as they cooled off and was able at that point to move the car by pushing it (could not do that 90 min prior). Gingerly drove the car home the last 5 mi and started looking things over. Bled the front calipers (fluid looked discolored) and pedal pressure seemed softer than before. Test drove in a parking lot then out for a local drive and everything seemed better but with the exception of a softer pedal. Decided to bleed the rear lines after which it seemed like my pedal pressure was way too soft. Re-bled the front calipers and as I opened the bleeder brake fluid started to come out for a short time as if under pressure. Now when I pump up the brakes I build pedal pressure but it doesn't seem to hold for more than a minute after letting the pedal "rest". Checked everywhere and there are no leaks. Given the lack of use and the initial event of hot front calipers I'm thinking this is an issue with the front caliper pistons? Since I can build pedal pressure I'm hoping its not a M/C issue since getting those out will be a real pain. Any thoughts would be greatly appreciated!

N.B- currently waiting on spindles for a Coupe build, considering taking the Wilwood calipers I have new in box and throwing them on the front of the Roadster to see if that solves the issue

Check the push rod on the masters to make sure there is free play.

Thanks Gordon. When I go to look at the push rods how much free play should I expect? Are you referring to free play with the balance bar? Thanks

As usual, Gordon is spot-on with his troubleshooting. Yes, you should feel about 0.150 - 0.250 inch pedal travel before the push rods contact the master cylinders.

Normally the pistons push back enough to unload the pads when the master cylinders are released.
If the free play is OK, unfasten your calipers and push the pistons into the bores, there should be little resistance.
If you (also) have a proportioning valve, (?) that may have a malfunction restricting back-flow. Otherwise your calipers may require a rebuild.

I have had a similar issue from mixing brake fluid types.
jim

Cincy, the attached cartoon of a typical dual MC will graphically show why the guys are focusing on ensuring you have full return travel and a small amout of free play before the pedal movement starts to push on the MC piston. Note how the inlet port becomes uncovered when the piston is at the rear of its stroke. That allows any residual pressure in the system to equalize with atmospheric pressure (the reservoir is under atmospheric pressure). If the piston does not uncover the inlet port you could have pressure build up holding the brakes. Brake fluid expands and contracts with temperature. That's one of the jobs of the reservoir, to allow fluid to expand and contract without negatively affecting the system. If the piston does not uncover the inlet port the fluid is trapped between the MC piston and the caliper piston. When temp rises the fluid expands and the pressure increases.

Attachment 149953

Sounds like sticking caliper pistons. Are they the dual piston calipers off a Mustang?

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Originally Posted by rich grsc

Sounds like sticking caliper pistons. Are they the dual piston calipers off a Mustang?

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The title says Wilwoods but along your line of thinking the Wilwood pads ride on a pin that may be rusty or fouled with brake dust, etc. Mine fit pretty tight when new so any gunk on them could cause them to hang up. May need to pull the pads and clean off the pins they slide on.

I mistook his comment as meaning he was thinking of switching to Wilwoods. Never mind

This is one a lot of people and techs miss. If you are useing conventional brake hoses they may be the problem. What happens is they degradate from the inside, meaning they constrict flow. It lets flow out under pressure but can't return. Another point I want to make is caliper pistons retract in their bores by way of the square cut seal, not vacuum or any other way.

I had a Wilwood master fail at about 2000 miles. Most likely from me not getting the balance bar and masters set up correctly the first time. I would follow Gordons advice and also double check the balance bar set up.

Balance bar directions.

https://www.wilwood.com/PDF/DataSheets/ds252.pdf

Thanks everyone I will begin troubleshooting per above this week.

Pushing this thread to the top as I've had a very similar issue I've been chasing. Long story short:

(1) Issue: Not enough front brake, front was firm but then went solid/didn't lock up with heavy foot.
Solution: Changed M/C from 3/4 to 5/8 to increase caliper pressure and changed to softer pad (Carbotech 1521 street pads). The Polyjunk wilwoods were just too hard for this light of a car when on the street.

(2) Issue: Front brakes locked up when hot, then self released.
Solution: I changed everything calipers, flex lines, adjusted pedal box. What finally fixed it and solved #1 above was pulling the clevis pens from the wilwood box (spinning the rod out of the way) and increasing the spacing between both clevis and the pedal. There's washers between the clevis pins and the rod. When it rotates/more pressure on one side vs. the other it goes at an angle and will bind. You need at least 1/4" on each side to be safe here. What was happening was it was binding and holding pressure/or was running out of throw on the front not allowing for full M/C extension/full brake pressure.

Hope this helps.

Duke, I agree with your assessment of the Wilwood pads -- they have very poor low temp brake torque as the cold Mu on their pads is way too low. Low enough that in my experience you can't increase the pressure high enough to get sufficient cold brake torque without exceeding Wilwood's max pressure limit. I went to a compound that has an Mu of .45 at 600F and could lock the tires at 400 PSI where with the Wilwoods I couldn't lock them at 1200 PSI (Wildwood's recommended max pressure limit).

However, on your second issue -- if you're talking about opening up the side clearance on a balance bar pedal assembly that is not the correct way to adjust this. I hope I read that wrong as opening up the side clearance on a balance bar system can be a safety issue. In fact, in case of the loss of one system (front or back) you could end up with a condition that limits the throw on the good M/C where it no longer is effective. This will defeat the redundancy of having two separate systems. That side gap is a critical adjustment. Don't take my word for it, read the set-up instructions or call Wilwood engineering to discuss. I've had complete brake system failures -- it's a major pucker factor and you really want to have a redundant system.

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Originally Posted by NAZ

Duke, I agree with your assessment of the Wilwood pads -- they have very poor low temp brake torque as the cold Mu on their pads is way too low. Low enough that in my experience you can't increase the pressure high enough to get sufficient cold brake torque without exceeding Wilwood's max pressure limit. I went to a compound that has an Mu of .45 at 600F and could lock the tires at 400 PSI where with the Wilwoods I couldn't lock them at 1200 PSI (Wildwood's recommended max pressure limit).

However, on your second issue -- if you're talking about opening up the side clearance on a balance bar pedal assembly that is not the correct way to adjust this. I hope I read that wrong as opening up the side clearance on a balance bar system can be a safety issue. In fact, in case of the loss of one system (front or back) you could end up with a condition that limits the throw on the good M/C where it no longer is effective. This will defeat the redundancy of having two separate systems. That side gap is a critical adjustment. Don't take my word for it, read the set-up instructions or call Wilwood engineering to discuss. I've had complete brake system failures -- it's a major pucker factor and you really want to have a redundant system.

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Attachment 150156

I'm not sure if this will attach correctly, but yes, you don't want too much space here (that creates another issue), but lack of space does create binding and all kinds of other problems. According to wilwood you want a total of .20 - .25" total gap between both (e.g. .10 - .125 per side). My issue was that at rest I only had just enough to spin the washers on each side. When compressed the washers were tight and at temps on a hot day it would bind even more.

Re-opening an old thread on Wilwood balance bar setup for free play between the clevises.

I currently have my total free play gap set to 0.22" or 0.11" per side between each clevis. The Wilwood spec is 0.20" to 0.25" total free play (dimensions A+B) in the instructional brochure included with the complete kit.

There is a Wilwood YT instructional video at the following link that suggests the total free play gap is roughly 0.125" or the equivalent of two quarters stacked together. It starts at 1:45 with the suggested setup procedure.

https://www.youtube.com/watch?v=ZYK4VEOae6w

So is the total free play set at 0.22" too much slop in the balance bar or am I overthinking this? I plan to bleed the MC's and brake lines soon and don't want to pull things apart again.

TIA

Quote:

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Originally Posted by jengum

Re-opening an old thread on Wilwood balance bar setup for free play between the clevises.

I currently have my total free play gap set to 0.22" or 0.11" per side between each clevis. The Wilwood spec is 0.20" to 0.25" total free play (dimensions A+B) in the instructional brochure included with the complete kit.

There is a Wilwood YT instructional video at the following link that suggests the total free play gap is roughly 0.125" or the equivalent of two quarters stacked together. It starts at 1:45 with the suggested setup procedure.

https://www.youtube.com/watch?v=ZYK4VEOae6w

So is the total free play set at 0.22" too much slop in the balance bar or am I overthinking this? I plan to bleed the MC's and brake lines soon and don't want to pull things apart again.

TIA

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Yours is set correctly. At 1:34 of the video is the usual Wilwood instructions showing "added together in the .20" - .25" inch range." That's also in the Factory Five build manuals and how I've always set mine and they work properly. His example using the two quarters with the other side pushed over contradicts Wilwood's own instructions. It might work OK set that way because the main objective is to keep it from binding. But I wouldn't do it.