Bleeding Wilwood Brakes?

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flashback
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Bleeding Wilwood Brakes?

#1 Post by flashback » Tue Apr 15, 2008 11:14 am

We're having a heck of a time getting a firm pedal...all the calipers are mounted with the bleeders facing up as they recommend and we have bled them a few times now. The pedal is still not where I feel it should be, a friend suggested that the XP600 fluid will not get us a "firm" pedal ever...anyone have experience with this?
G.
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#2 Post by John_Heard » Tue Apr 15, 2008 11:26 am

Is that a silicone based brake fluid? I think that's the kind that brake mfg's don't want you to use as it can cause a spongy pedal and doesn't absorb moisture in the system.

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I don't think so...

#3 Post by flashback » Tue Apr 15, 2008 1:13 pm

Here's the info from their site:

EXP 600 PLUS SUPER HIGH-TEMP RACING BRAKE FLUID:
EXP 600 Plus is a highly refined blend developed for extreme performance under the high heat and extreme pressure of professional motorsports.
What’s in a number?
EXP 600 Plus has tested to 626 degrees F with a wet boiling point of 417 F. These numbers far exceed any DOT or SAE specifications.

What’s the real test?
It is true that racing fluids need to have high boiling points. It is also true that fluids need to have low moisture affinity to slow the natural absorption rate of water vapor. But the true test of any fluid is how well it resists aeration and compressibility after it has been heated and pressure cycled a few hundred times. The real test is at the track. EXP has proven to maintain firm pedal feel and quick response, long after others have failed.

Where’s the proof?
A Winston Cup car racing for 500 laps at Martinsville is the most grueling brake test in all of motorsports. The brakes will be applied up to 1,000 times, plus pit stops, at sustained high heat and repeated high pressure. IRL, CART, ASA, Busch, Craftsman Trucks, and a whole world of other oval and road course competition series also demand extreme performance from their brake systems. EXP 600 Plus has passed the test in every series!

Note:
For optimum performance, EXP 600 Plus should not be diluted with any other brake fluids. Add new fluid to a clean system.
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kyleracer
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brakes

#4 Post by kyleracer » Tue Apr 15, 2008 8:51 pm

I had to get a brake bleed kit from the autoparts store to get mine to feel right. There is alot of air in a system trapped in the fittings etc. It took me about 3 tries to get all the air out. The kit is only $6 so the cost is cheap for the results and you can watch the fluid until it is clear without any mess :D .

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#5 Post by John_Heard » Wed Apr 16, 2008 5:53 am

That doesn't sound like silicone fluid, must be either air in the system still assuming you have a good master cyl and correct bore size. A small bore master like 7/8" will feel softer as compared to a 1 1/8" bore model even with the air out of the system.

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I'm sure it's more air...

#6 Post by flashback » Wed Apr 16, 2008 10:00 pm

We took it over to K&S Alignment last nite to get that all squared away (we were pretty dang close using the eyeball method) and driving it from the trailer over the alignment pit I got a chance to see how the brakes functioned...two or three pumps and they feel pretty good!!
I'll have my guys pickup one of those brake bleeder kits tomorrow and we'll see if we can't eliminate this problem once and for all....Thanks for all the replies here to a "newbies" questions and making me feel welcome.
If ya all are looking for some parts I run a small part-time shop and I'll get ya as good a deal as I can...we specialize in QFT carbs and FPS braided-hose/AN fittings.
Thanks again people!!!
Gene
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master cylinder

#7 Post by flashback » Thu Apr 17, 2008 10:18 pm

John_Heard wrote:That doesn't sound like silicone fluid, must be either air in the system still assuming you have a good master cyl and correct bore size. A small bore master like 7/8" will feel softer as compared to a 1 1/8" bore model even with the air out of the system.
We've got the Strange master cylinder, I believe it's the 1 1/8 one..Mopar style I understand. I picked up one of those bleeder kits today for 9 bucks so we'll give her another go tomorrow after work...like I said, after three pumps they feel real solid so it's gotta be an air problem...I'm just a nervous wreck with all the changes we've made for this season.
Once we get a run in on her I'll be good to go myself...It's been a LONG winter!!!!!
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sc racing
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#8 Post by sc racing » Sat Apr 19, 2008 11:07 am

Wilwood suggests tapping the calipers with a rubber hammer to loosen air bubbles when bleeding.They have always told me that a smaller bore will create more pressure with less effort on the pedal.Also always use 3/16" line.

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Got it....sort of....

#9 Post by flashback » Mon Apr 21, 2008 12:10 am

Well, the one-more-time method worked and we got ourselves a decent pedal only to come up with another problem.
Under moderate to heavy braking pressure I'm getting abit of shudder back through the steering wheel...didn't notice it while doing the braking arund the pits as we were attemping to "set" the pads and rotors.
The car's stopping straight and all but the shudder in the steering wheel tells me that somethings not quite right here....????
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#10 Post by John_Heard » Mon Apr 21, 2008 6:53 am

Do you have any runout in the rotors? With the tire/s off the ground and spinning the wheel is there a place it rubs the pads more than others?

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Gotta check that...

#11 Post by flashback » Mon Apr 21, 2008 8:59 am

I'm gonna borrow a magnetic base / dial indicator and check that out this week...there were some washers included with the brake kit, maybe we need to shim something??
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#12 Post by John_Heard » Mon Apr 21, 2008 9:30 am

If the caliper was crooked it would just wear the pad funky, shouldn't make it shudder I wouldn't think. Might not hurt to call Wilwood up and get their opinion too...

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Here's the latest.

#13 Post by flashback » Mon Apr 21, 2008 10:32 pm

The Wilwood tech book says that .005 to .008 runout is within spec...we have the driver side checking in at .004 and the passenger side at .008
Now, we can try and remount them (there's six mounting bolts) and see which way gets us the least amount but they do seem to be within spec.
I called and left a message on their Tech line today and I hope they'll get back to me tomorrow.
The rotors looked fine, no hot spots or anything...the passenger side has a couple of very small grooves in it....something had to have been stuck between the rotor and the pad, but I've definitely seen worse and don't think that's the problem.
We did shim them out with one more washer as the calipers were slightly set off to the inside so possibly that was the problem???
I don't have anywhere to test it until this weekend when we get to the track though...I'm sure the county sheriff wouldn't be too happy if we took her down the countyroad......but I'm contemplating doing that :wink:
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Called back from Wilwood tech staff:

#14 Post by flashback » Tue Apr 22, 2008 1:12 pm

Even though the tech catalog shows 005 to 008 being okay the techguy says to keep it under 005 and we should try re-clocking the rotor on the hub area to see if we may be running into a "stacking" problem as far as the runout goes.
He also suggested hitting the rotors with some 80 grit and redo the bedding process....we'll see how that goes and touchbase with him after this weekend.
I'll let ya know here as well, in case anyone else runs into this.
G.
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Update

#15 Post by flashback » Wed Apr 23, 2008 11:34 pm

Well, we re-clocked the .008 side and got it down to the 004/005 range, sanded the rotors and found a loose bolt! One of the three that hold the bracket to the spindle...threadlocked and torqued now! That could have been the culprit or the shudder could've shook it loose.....I'm thinking it was the cause, not the affect??
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