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View Full Version : Soft Pedal vs. Axle Runout - solutions? Willwoods (fixed callipers) on a 12 bolt GM



bovey
08-11-2013, 03:40 PM
Apparently this is a common problem with fixed rear callipers - that no one seems to warn you about until after you complete a rear disc conversion. lol. You put rear discs on to stop better, but because your putting fixed callipers on a rear end that naturally has end play - the callipers get knocked back. The result is a soft inconsistent petal that every one says "It must be air." Well it's not always air, it's could be axle runout knocking back the pads while corning.

My situation:
12.24 Wilwoods with 4 piston fixed callipers
Wilwood Master - 1" manual
Wilwood proportioning valve
12 bolt Series 4 GM - 71 GMC - stock other that a Auburn Pro limited slip
Axle End play is minimal and in spec.
Rotors are true.
rear axle mounting surface is true and clean.
Petal is consistent while driving straight but after you turn a corner, like while autoXing and the petal goes soft.

Solutions(?):

1) C-clip elimination - however I have heard that it's more of a drag race this and in autocross you can still have lateral G issues. Anyone have experience with this?

2) Spoke to one racer who made new c-clips that fit tightly and take out most of the endplay. However, he did say MOST, it's still an issue.

3) New rear-end. Suggestions? For the guys how are autoXing, what do you use?

4) Open to other ideas and experience.

Thank our everyone in advance.
Bovey

Red67Mustang
08-11-2013, 04:18 PM
May be cheaper to just change the brakes to floating calipers. Have you spoken with Wilwood about the problem to see if they would cut you some slack on floating calipers? (Assuming they even offer them).

sccacuda
08-11-2013, 04:35 PM
A C-clip eliminator should remove the majority of axle endplay by playing with shims either between the bearing and retainer plate or cup and housing. These are straight rollers that don't want any preload, so endplay is inevitable. A full floater will eliminate all to within a few thousands. You can buy GN snouts and put them on your existing axle for a full floater setup, or switch to a FF rear.

bovey
08-11-2013, 06:50 PM
Looking at Willwood floating callipers... also been reading about how many people have this issue. I do not understand why they offer fixed rear conversions for c-clip rear-ends. People must just put up with the petal or maybe they don't know any better??? Going to call Wilwood tomorrow - The bolt pattern on the floating callipers is different from the kit that they make for a truck 12 bolt - let's see if they make a special bracket for the D-154 calliper (floater). Going to look at FF rears too.

bovey
08-11-2013, 06:58 PM
Hoping Wilwood has an option - a 12 bolt FF Moser is $2922.00 - with the options I need, which I already have, but with c-clips...

Ron Sutton
08-11-2013, 09:03 PM
Hoping Wilwood has an option - a 12 bolt FF Moser is $2922.00 - with the options I need, which I already have, but with c-clips...

Don't panic ... there is a low cost solution.

Changing the rear end to full floater housing ends is without a doubt, the best method. But it is mildly expensive, involved & requires cutting & welding on new housing ends, getting new axles, etc, etc. Again, it is the best way to go … safer, stronger, more true, less wheel & brake rotor deflection, which are causes of brake pad knock back. Just out of the price range for some guys.

A less expensive alternative for 10-bolt & 12-bolt GM guys … are to add on C-clip eliminators. Not the drag racing kind with the roller ball bearings. The street & track kind that use Timken tapered roller bearings … along with a secure way of retaining the axle in case of failure.

They are available from Strange Engineering. Part # A1033
Go to this link (http://www.strangeengineering.net/catalog/index.html)… then go to page 16 … and scroll down until you find the part #A1033.

These C-clip eliminators solve two big issues. One is they reduce wheel & brake rotor deflection … and therefore pad knock back. Two … it adds a big level of safety for c-clip axles. I think this is a big deal.

The safety issue is not about the c-clip falling out or breaking. The issue is ... if the axle breaks ... the results are disastrous. The axle, tire & wheel combo come out of the car ... under load & at speed! A c-clip eliminator converts your axle bearing to a press on bearing of better quality ... AND ... utilizes a bearing housing end that bolts onto the housing end/backing plate end. Not only is it stronger ... but if for any reason you break an axle ... the axle stays in the rear end. Not so with factory c-clips ... if it breaks ... the axle, wheel & tire come OUT !

You don’t need new axles. Everything stays the same … brakes, wheels, housing, etc. It does require some labor for installation. A full set up costs $180 ... so it is a VERY SMALL price to pay for a LOT of safety for you & the people around you ... and protection for your car. This is the version for street, cornering, auto-x, etc. It uses a tapered roller bearing, which is stronger in every direction, compared to the POS stock gm axle bearing.

Wes.Drelleshak
08-11-2013, 09:10 PM
Those darn c clips and end play. Yep that will do it. Joking aside I've heard people installing a 2 pound res valve on the rear line to help hold the caliper to the rotor. Does this work ? I have no idea, sounds like it might. The c clip eliminator might push the wheels out a Inch or so, so Make sure you have room.
Also some people that get brake knock back may drag the brake pedal with the left foot making the piston stay in the bore. Lets talk axle bearings. Some believe that sealed none tapered bearings work for autocross but they may or may not need to be checked or changed more often than a say ford large tapered bearing. On a ford 9 inch the bearing retainer plate can also deflect causing brake pad knock back. Overall vehicle weight is a major factor to bearing side load or c clip load. The best bet is to build a floater but that is also not budget friendly. Hopes this helps. WesD

Ron Sutton
08-11-2013, 09:15 PM
Hey Wes,

Agreed ... floater is best route. The C-clip eliminator does not move the axle flange, wheels or brakes in or out. I do find the larger the rotor ... the more of an issue this is.

GEARBOXGARAGE
08-12-2013, 04:49 AM
Ron,

Thanks for the link and great info! I checked it out and saw that it mentions GM G-body for A1033. I'm not familiar with the G-bocy axles, so I assume they have the same bolt pattern and housing end size as the 12 bolt truck rear ends?

-Mike

Ron Sutton
08-12-2013, 06:18 AM
Ron,

Thanks for the link and great info! I checked it out and saw that it mentions GM G-body for A1033. I'm not familiar with the G-bocy axles, so I assume they have the same bolt pattern and housing end size as the 12 bolt truck rear ends?

-Mike

I'm sorry, but the G-body axle & truck axles are not the same.

Even though the description is a little misleading ... the A1033 fits all small bearing GM passenger car housings ... including 8.2" 10-bolts from the 60's, most 12-bolts & 8.5" 10-bolts from the 70's ... as long as they are the small bearing. The gap in their product line is the larger bearing ends on the Impala & C10 trucks.

The A1033 also fits the G-body axles with the weird 3-bolt end, but requires drilling of the end & installing a "sleeve" on the axle, which IS supplied in the A1033 kit.

If you were also ordering axles from Strange, their A1100 kits fits all the same rear ends as the A1033 ... but the ID of the bearing is larger ... to fit on the Strange custom axle. Their forged axles ... combined with A1100 c-clip eliminator kit with tapered roller bearings ... are a good lower cost alternative to building a floater rear end.

But I still strongly recommend the floater rear end for hardcore PT cars that are going to run road course track days and/or lots of AutoX events. In addition to being safer, they reduce or eliminate brake pad knock back issues by minimizing hub, rotor & wheel deflection.

Wes.Drelleshak
08-12-2013, 07:29 AM
Good to know Ron. The Ford 8.8 c clip eliminator kit that i was looking at moves the wheels out 1 inch. I didn't know if the truck 12 bolt would do the same with the eliminator kit.

I agree with Ron on the size of the rotors. The larger diameter rotors can increase the degree of movement side to side. Make sure you install a quality bearings and not china junk. But if you really get down to it it's not the brakes fault it's the axle/rearend.
Anyone tried a Speedway Motors Floater for a street vehicle?

On my truck I used Speedway Engineering hubs, axles with a Currie Enterprises Ford 9 inch center housing, tubes with Wilwood 4 piston calipers. That combo works really good!

Ron Sutton
08-12-2013, 07:32 AM
Good to know Ron. The Ford 8.8 c clip eliminator kit that i was looking at moves the wheels out 1 inch. I didn't know if the truck 12 bolt would do the same with the eliminator kit.

I agree with Ron on the size of the rotors. The larger diameter rotors can increase the degree of movement side to side. Make sure you install a quality bearings and not china junk. But if you really get down to it it's not the brakes fault it's the axle/rearend.
Anyone tried a Speedway Motors Floater for a street vehicle?

On my truck I used Speedway Engineering hubs, axles with a Currie Enterprises Ford 9 inch center housing, tubes with Wilwood 4 piston calipers. That combo works really good!

I really trust the Speedway Engineering stuff. I run their floater hubs too.

andrewb70
08-12-2013, 03:46 PM
This is why I went with the 4th gen f-body (LS1) rear brakes with floating calipers. I know that fixed calipers sound sexy and all that, but as much as we like to pretend that we own race cars, the truth is that we don't.

Andrew

bovey
08-12-2013, 04:17 PM
Just a quick reply, larger one later.

First. Ron. Wes. Thanks for all the info - amazing. Seriously large help. Researching.

Second. Wes - do you run the 12.19 with the 4 piston Wilwoods - just curious.

Third. Andrew. I am envious that you knew enough to do that. I asked a lot of questions, but did not know to ask about axle end play - Learning is fun.

Fourth. A photo from the week-end. Had an off day, like really, REALLY off, but it was still a riot.

80735

Again, more later.
Bovey

Ron Sutton
08-12-2013, 04:34 PM
This is why I went with the 4th gen f-body (LS1) rear brakes with floating calipers. I know that fixed calipers sound sexy and all that, but as much as we like to pretend that we own race cars, the truth is that we don't.

Andrew


I agree on the floating part. Even in race cars ... rules permitting, we like to either float the caliper or the rotor.

With that in mind, Wilwood offers some sweet floating replacement calipers for GM applications. They replace the stock cast iron single piston factory caliper, with billet aluminum calipers, red or black powder coated, with single or twin stainless steel pistons with good braking force ... and they float, just like the stock calipers.

The D52 Dual Piston Calipers are here (http://wilwood.com/Calipers/CaliperList.aspx?subname=GM%20D52%20Dual%20Piston) .
The D154 Single and Dual Piston Floater Calipers are here (http://wilwood.com/Calipers/CaliperList.aspx?subname=D154%20Single%20and%20Dua l%20Piston%20Floater).

Here is a quick chart showing them compared with many other calipers ... ALL with the same pedal ratio, foot force, master cylinder & brake pads.

80739

Clamping force by itself doesn't mean a particular caliper is good or bad. Just realize, when you put a brake system together ... EVERY detail matters. You need to design the whole system to achieve the desired braking. Personally, I do not like calipers with low clamping force for performance street cars ... because they require aggressive race pads to achieve the optimum braking numbers. Aggressive race pads wear out quicker & cost more.

Just my opinion & preference.

bovey
08-12-2013, 05:41 PM
Ron. Could you explain Brake Torque vs. Total Braking Torque if 70%. Also, I'm assuming Calliper braking force is a gross number if they call out the lower "net" number on the following line - is that correct?

RobNoLimit
08-12-2013, 05:42 PM
1. C-clip eliminator would be pn the top of my list, if for safety only, but there are other benefits.
2. depending on the rotor hats that came in your kit, you may be able to swap them for a set that use 'T' nut mounts to 'float' the rotor. Calling Wilwood may help, but searching their tech notes section will tell you. If you get me the exact part number of the rotor and hat I can help.
3. Ron, that brake table is great! where on earch did yopu get that, and, can I get a copy.it tells me I was right. Factory Impalla 12" rotor and full size caliper is where its at!

Ron Sutton
08-12-2013, 05:56 PM
Ron. Could you explain Brake Torque vs. Total Braking Torque if 70%. Also, I'm assuming Calliper braking force is a gross number if they call out the lower "net" number on the following line - is that correct?


No worries.

You should probably ignore the 5 lines with black type. The two you care about are purple. The "Brake Torque" is the actual braking force of the front brake caliper & pad ... with the rotor, pedal ratio, foot force & master cylinder spec'd in the sheet.

The bottom line that says "Total Braking Torque if 70%" is a "Ron helper" so I don't have to do the math in my head. I usually shoot for 70% front braking force, so that number is "backed into" ... and is what the TOTAL braking force will be with that caliper & pad accounting for 70%.

P.S. All of these braking force numbers are on the low side ... because they're using a 5-1 pedal ratio, 1" M/C & moderate street brake pad. This chart was just for comparison of calipers. All of these systems can make more braking force with a higher pedal ratio, more aggressive pad or smaller M/C.

Ron Sutton
08-12-2013, 05:59 PM
1. C-clip eliminator would be pn the top of my list, if for safety only, but there are other benefits.
2. depending on the rotor hats that came in your kit, you may be able to swap them for a set that use 'T' nut mounts to 'float' the rotor. Calling Wilwood may help, but searching their tech notes section will tell you. If you get me the exact part number of the rotor and hat I can help.
3. Ron, that brake table is great! where on earch did yopu get that, and, can I get a copy.it tells me I was right. Factory Impalla 12" rotor and full size caliper is where its at!

Hey Rob,

I got tired of calculating brake systems one at a time, so I built a spread sheet. I have a few versions for comparing 2-4 front & rear systems side by side. I created this one so I could compare all the common front caliper & rotor combinations and sort the hype from the facts. :)

bovey
08-12-2013, 06:30 PM
1. C-clip eliminator would be pn the top of my list, if for safety only, but there are other benefits.
2. depending on the rotor hats that came in your kit, you may be able to swap them for a set that use 'T' nut mounts to 'float' the rotor. Calling Wilwood may help, but searching their tech notes section will tell you. If you get me the exact part number of the rotor and hat I can help.

1) This seems to a consensus - the only challenge I seem to have is the Truck 12 bolt. My Wilwoods are for the Truck mount. Moser makes what they call an Impala and Truck kit - SKU 9100 - I just have to confirm the tapered bearings. Still reading.

2) The exact part numbers of the the kit are as follows.

Forged Dynalite Rear Parking Brake Kit w/drilled and slotted rotors P#:140-10094-D
SRP Drilled Rotor & Hat (12.19"D x .81"W) Left P#: 160-9990-BK, Right P#: 160-9989-BK
Forged Dynalite Callipers (4 Piston - lug mount) Left or Right P#: 120-6806
Link:
http://www.wilwood.com/BrakeKits/BrakeKitsProdRear.aspx?itemno=140-10094-D&year=1971&make=Chevrolet&model=C10+Pickup&option=Vehicles+using+CPP+2%22+Drop+Spindle%2c+5+L ug+only.

The video you just posted also reminded me of my long term goals - excellent timing. Which is to put a proper chassis under this thing. I do not intend to use my current frame because it is a Canadian truck and spent time in salt. Getting a second original chassis doing all the bolt-ons seems silly when companies like No Limit, etc make bolt in chassis that let's be honest - rock. I am getting my feet wet AutoXing this year and want to keep my budget in check - which is why the FF rear is not ideal. However, I do like the idea of doing either A) c-clip eliminator or B) floating callipers. But I just want to make sure I don't get in over my head with a c-clip eliminator kit as I cannot do that level of work on my own and have to farm it out.

bovey
08-12-2013, 06:31 PM
P.S. Thanks for the clarification on the terms. It's a fascinating chart.

bovey
08-13-2013, 03:12 PM
Spoke to Wilwood Tech today.

You can order parts to change the fixed 12.19 kit into a floater using the D154 callipers. So, if you have the Forged Dynalite Rear Parking Brake Kit - P# 140-10094 /D/DR/R you need the following parts to change to floating callipers.

1) 12.19 brackets - P# 250-12188 - same for both sides - X 2 - bracket only for D154 callipers. They bolt to the existing backing plate.

2) D154 calipers - various P# depending options you need. - These callipers come with slide pin, etc. Callipers DO NOT come with pads.

3) Pads P#150-8936K - BP-10 is Willwood's Street Performance Pad - same compound as the fixed Dynalite Kit.

OR

Wilwood now make a floater C10 12.19 kit WITH D154 callipers - here is the link

http://www.wilwood.com/BrakeKits/BrakeKitsProdRear.aspx?itemno=140-12569-D

P# 140-12569 same /D/DR/R options. It should be noted that the kit comes with the smaller piston callipers but you can order what need depending on your application.

NOTE: The tech guy did say that depending on the amount of end play a floater kit may not solve the issue. He said the same as everyone, to do it properly do a c-clip eliminator kit + the floater OR get a FF rear-end.

I am still sorting finding all the right C-clip eliminator parts for the Truck/Full Size Car 12 bolt.

Cheers,
Bovey

Ron Sutton
08-13-2013, 05:16 PM
Hey Bovey,

Thanks for sharing the info you found.

surlyjoe
08-14-2013, 06:35 AM
A bit of a highjack sorry. Ron, I read your posts on the f body brakes and rear caliper choice. I was wondering what brake bias is best for a c10? More bias to the front? This leads to the next question which is the kit above includes the d154 with smaller 1" pistons as opposed to the 1.25". Which caliper would be the better choice for a truck? With say 12" on the front with d52 caliper.

Ron Sutton
08-14-2013, 09:09 AM
A bit of a highjack sorry. Ron, I read your posts on the f body brakes and rear caliper choice. I was wondering what brake bias is best for a c10? More bias to the front? This leads to the next question which is the kit above includes the d154 with smaller 1" pistons as opposed to the 1.25". Which caliper would be the better choice for a truck? With say 12" on the front with d52 caliper.

Hey Joe,

Start a new thread titled" Need help with C10 Brake Upgrade" ... with this info & specifically ask for my help in the post. Also, please put in more details about the truck, wheel size, weight, suspension types, how you plan to use it, goals, etc.

I'll find it an answer your questions, show you some brake system options & help you work out a set-up.

bovey
08-14-2013, 12:48 PM
I look forward to the new thread. FYI - I run:

Stock front everything with Hawk HP+ pads

Wilwood 1" manual master

Wilwood proportioning valve

Wilwood 12.19 x .81 rear w/ 4 piston calipers.

Lines are stock sizes with short braided flex lines on the calipers.

Truck is 3950lb

I was surprised when I did not have to dial down the rear bias.

I'll update my post with wheel/tire weight later.

With exception to what I've outlined in this thread - I works great and pulls down amazingly well. I've have very surprised C6 and STi owners along for ride alongs. They swear a lot when something stops better than they expected. Me too for that matter.

Ron Sutton
08-14-2013, 12:56 PM
I look forward to the new thread. FYI - I run:

Stock front everything with Hawk HP+ pads

Wilwood 1" manual master

Wilwood proportioning valve

Wilwood 12.19 x .81 rear w/ 4 piston calipers.

Lines are stock sizes with short braided flex lines on the calipers.

Truck is 3950lb

I was surprised when I did not have to dial down the rear bias.

I'll update my post with wheel/tire weight later.

With exception to what I've outlined in this thread - I works great and pulls down amazingly well. I've have very surprised C6 and STi owners along for ride alongs. They swear a lot when something stops better than they expected. Me too for that matter.

Did I understand correctly that you still have the stock GM front brakes?
Is that the 11-7/8" rotor & caliper with 1 big 2-15/16" piston?

.

bovey
08-14-2013, 03:48 PM
Yes. I'd have to confirm those sizes for you. BUT, I run what people generally refer to as the stock 12" front rotor, I would have to confirm the calliper piston size for for you. I remember correctly, when we put it back together the stock callipers cross reference with the monster Cadillacs of the era and cop cars - but it's been a long time - they might have been for the '73-87... sorry for the lack of details. While the parts are a little underwhelming, it seems to work well. I am upgrading further next year, but am experimenting with really minimal stuff this year as a basis.

Ron Sutton
08-14-2013, 04:09 PM
I just wanted to be clear.

We ran that same set-up in the NASCAR Modified class, because rules required "cast iron stock appearing calipers" & stock rotors. Actually ours were 77+ Impala from Howe, but similar to what's in your truck. We had to tone down the brake pad compound so we didn't have too much brakes. :)

bovey
08-14-2013, 05:51 PM
That's interesting. And on that note, when doing a advanced driving school in the spring - other drivers had STis, M3s, EVOs, Caymens, etc, etc. With my stock 43 y/o brakes and NO ABS, they only had 3-5 feet on my stops from 50 MPH. I was shocked, everyone was shocked. Some of these cars had 13" and 14" Brembos all the way around. Seriously, one of those rotors is worth more than my entire brake system at the time (still had drums). However, I would be willing to bet once they figured out their ABS the difference would grow, or at least I'd hope for the hardware they where running. That is all.

The plan was to upgrade the front to 13" or whatever, but I would like to get the system working well before tossing more $ at it.

RobNoLimit
08-14-2013, 07:23 PM
For comparison, and discussion, I can tell you what we run, and how it stacks up. Our Wide-Ride IFS uses an Impala clone spindle, we had them made. they are .800" taller than OEM, and the steering arm is shorter and positioned farther outboard. But, the standard brake package for our front ends uses OEM style rotors and calipers. I say OEM style, because we had rotors made with dual patterns and screw in wheel studs, and there drilled and slotted. They are 11 7/8" x 1" rotor, and the Impala cop car 2 15/16" piston floating caliper. We also offer several brake 'upgrades', 13", 14", 4 piston, 6 piston.... and I have tried them all. My last truck, the Silver Bullit F100, was the test bed. In the end, the only set up that offered better braking than the OE gear was a combination of a No Limit billit hub, No Limit floater plate, Wilwood spec-37 14" x1.1" rotor, and a Wilwood 4 piston Superlite caliper with 1.75" bores. The same set up without floater plates was close, but barely better than the OE. what did all of this teach me? well, Cop cars had good brakes. Some of the aftermarket is engaged in selling 'the Emperors New Clothes', and, you don't always get what you pay for. So, ask questions from those who know from first hand experience, do your home work BEFORE you shell out hard earned cash, and always thank Ron for sharing his time and knowledge.

bovey
08-14-2013, 07:40 PM
A) Fascinating. B) Great Advice C) Yes. Ron ROCKS. Actually, many of you do. Thanks.

P.S. Was checking out your C10 chassis. We will talk at some point in time.


Just tagging the other discussion on C10 brake upgrades:

https://www.pro-touring.com/showthread.php?101154-Need-help-with-c10-brake-upgrade

Ron Sutton
08-16-2013, 03:19 PM
Hey Rob,


For comparison, and discussion, I can tell you what we run, and how it stacks up. Our Wide-Ride IFS uses an Impala clone spindle, we had them made. they are .800" taller than OEM, and the steering arm is shorter and positioned farther outboard.
What the *#%@ ? You're holding out on me. I gotta see it & get some specs. Post photos please!

But, the standard brake package for our front ends uses OEM style rotors and calipers. I say OEM style, because we had rotors made with dual patterns and screw in wheel studs, and there drilled and slotted. They are 11 7/8" x 1" rotor, and the Impala cop car 2 15/16" piston floating caliper. We also offer several brake 'upgrades', 13", 14", 4 piston, 6 piston.... and I have tried them all.
Hard to beat the 6-3/4" piston area of those big GM calipers. We ran them in our Mods & I had to reduce braking force by running harder pads. :)

My last truck, the Silver Bullit F100, was the test bed. In the end, the only set up that offered better braking than the OE gear was a combination of a No Limit billit hub, No Limit floater plate
Hmmm. More stuff you make that I need to know about. Post photos please!

, Wilwood spec-37 14" x1.1" rotor, and a Wilwood 4 piston Superlite caliper with 1.75" bores. The same set up without floater plates was close, but barely better than the OE. what did all of this teach me? well, Cop cars had good brakes. Some of the aftermarket is engaged in selling 'the Emperors New Clothes', and, you don't always get what you pay for.
Way too true ... from several sources.

So, ask questions from those who know from first hand experience, do your home work BEFORE you shell out hard earned cash, and always thank Ron for sharing his time and knowledge.

Please post info & photos of the Superlite floater mount & custom spindle with Impala pin.

Thanks !!!

Ron Sutton
08-16-2013, 03:21 PM
That's interesting. And on that note, when doing a advanced driving school in the spring - other drivers had STis, M3s, EVOs, Caymens, etc, etc. With my stock 43 y/o brakes and NO ABS, they only had 3-5 feet on my stops from 50 MPH. I was shocked, everyone was shocked. Some of these cars had 13" and 14" Brembos all the way around. Seriously, one of those rotors is worth more than my entire brake system at the time (still had drums). However, I would be willing to bet once they figured out their ABS the difference would grow, or at least I'd hope for the hardware they where running. That is all.

The plan was to upgrade the front to 13" or whatever, but I would like to get the system working well before tossing more $ at it.

Bovey,

Would you measure your brake pedal for me?

On the brake pedal, what is the distance from the center of the upper pivot to:
a. The closest master cylinder pushrod connection hole
b. The second master cylinder pushrod connection hole
c. The center of the foot pedal

bovey
08-18-2013, 04:09 PM
Ron. We are on the same page - I was already doing that for you - kinda. I'm going redo based on your request. I'm working out the details for "blank slate" and was going to post tonight - but I'll do the above and do a super post all at once. Your eagerness is inspiring. Thanks.

bovey
09-05-2013, 04:28 PM
Update.

For a bunch of reasons, that I'll save you from, I decided to try a band-aid solution on my pad knock back issue. I have read many threads on many forums and decided to try a residual valve. Wes had mentioned it earlier in the thread. Now, when you talk to Wilwood, they say that you only need to do this if you have a low mounted MC OR are running rear drum brakes. HOWEVER, if you read their TECH bulletins for trouble shooting, they do recommend a 2 lb residual valve to solve the problem. In the online community many have tried the 2 lb with no luck, but have found the 10 lb to work on c-clip GM rear-ends.

So, today I did my own experiment.

After reading, and reading, I bought a 10lb and a 2lb. I installed the 10lb first, and if it was too much - I'd put the 2 lb in. BUT, the 10 lb worked amazing. Not 100%, but close enough for a $30 fix. I have no issues with the pads dragging AND the front and rear brake temps are the same. Better yet, my brakes are firm, the pedal feels great, although there is a super small amount of pump-up every so often. Again, this is a band-aid fix.

So, I'm going to monitor brake disc temps over the week-end during regular driving AND I have a race next week-end.

Will report back. Thanks for all your help. Will also report back when I build a proper rear-end.

GEARBOXGARAGE
09-05-2013, 04:47 PM
That's some great info, bovey! I was thinking about this exact situation earlier this week and wondered if this would provide an adequate temporary fix when running c-clips. Can't wait to hear your report back on the results.

bovey
09-16-2013, 11:31 AM
Hey everyone,

I've been running with the 10lb residual valve fix for about a week and half. Everything is working as I mentioned in my last post. Given the totally different front and rear set-ups I wasn't expecting them to be the same, but am glad everything is in the same-ish ballpark - with exception to my left front (sitting in driver's seat). I'm using a point and shoot temperature gun, so there is a +/- on these numbers. All four corner temps where taken within about 20-30 seconds.

FYI - I use Hawk HP+ on the front and Wilwood BP-10 on the rear.

A lovely 3.5 hour drive to my parents in stop and go traffic on a highway - the temps on arrival were:
left rear: 224.6°F
right rear: 228.2°F

left front: 244.4°F
right front: 231.8°F

This week-end I AutoX'd. My runs were around 85 seconds - the course is fairly technical as I run with a Subaru/Miata/S2000 crowd. The track ends with a full stop-stop box so I'm really on 'em at the end an there was a carousel at the end of the track as I was running on an airstrip. Again, everything pulled down great and (sadly) achieved lock-up a few times. Temps taken after my 4th run in about 1 hour.

left rear: 246.2°F
right rear: 249.8°F

left front: 296.6°F
right front: 269.6°F

My left front suggests the calliper is not working correct. Going to take it apart and clean it. I can't feel anything, but clearly something is up.

Cheers,
bovey

BuddyP
09-18-2013, 07:30 AM
Great thread! Wish I would've saw this a couple days ago before spending hours on the internet machine reading up on bits and pieces of this. I have the same fade you had with hard cornering or when backing up due to what I finally figured out was knock back. However I have a set of C6 brakes I'm going to replace the wilwoods with. But may still look into the Strange C-clip eliminator kit.

bovey
09-18-2013, 03:13 PM
Cool. When looking at the c-clip kits. Ask for tapered bearings (some call it a circle track kit), NOT the kind used in drag racing. The tapered bearing helps with lateral force and help solve the knock back issue. Apparently, not all c-clip eliminator kits are created equal. Be sure to tell strange or whomever what you are trying to solve a knock back issue. Why you ask? Some c-clip eliminator kits leave a little play - like 1000s of an inch - AND that is enough to cause pad knock back.

Be sure that the axle end plates for the kit are thick (1/4" -ish) and go all the way around not the thin notched kind you can install after the axles are in. You can find threads on this.

If you are working on the Camaro in the photo (which is awesome by the way) - you will not have much problem finding thread on the the stuff I have mentioned above. It's a different story with Truck/Impala 12 bolts as they are different housings (ends) and the axles seem to be a different dia. for the bearings as they need to be lathed to fit the kits/parts available/that I could find).

Good luck!