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Old 04-21-2010, 12:35 PM   #1
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Why We Have Brake Issues

I have been working with a customer the has access to a machine shop. He has had some brake issues and wanted to rebuild the calipers. I pointed him to Euclid Ind for seal kits.

Needles to say he had another brake failure this last w/e. Once he got home Sunday he proceeded to pull the front wheel, removed the caliper and headed to the shop. He removed the front piston but it took 140 psi air to get the caliper out. The rear piston would not budge no matter how much air pressure he applied. He actually had to put the caliper on the lathe and cut it out. He the mic'd the front caliper bore and the piston only to find out that there was only .0015 clearance when there should have been .005 to .006. After taking some more measurements he cut 2 new pistons from stainless steel. He installed the seal kit from Euclid, reinstalled caliper, bled the brakes and took it for a test run. He ran the rotor temps to about 400 degrees. But the back side of the calipers were around 100 to 150 degrees. But, his testing cost him 2 ABS sensors on the rear.

One last bit of info. He heated the original caliper piston with a lamp he had on the bench. Just in a matter of minutes the caliper had expanded .001. He was able to actually hold the piston in his hand to do the measurement and the piston would not fit in the caliper bore. He then heated the SS piston to almost 400 degrees and it only expanded .001+. When I asked if these could be made from high carbon steel and not stainless to save on cost, he said sure. Considering that the caliper is cast and the piston sits in brake fluid there isn't any reason that it could not be done.

The bottom line here folks is that a machinist in a matter of hours fixed the problem and did a preliminary test. Further testing to follow. If it all works he will make the rest of the pistons and probably bypass the Workhorse recall. So why is it taking so long to GET-R-DONE?
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Old 04-21-2010, 01:33 PM   #2
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One of my friends owns a machine shop that does prototype military parts / Government contracts. Anyways I asked him awhile back about building pistons and said no problem. He even had some Mil spec material we could have tried. But in me doing some more research and he called a few people we found out that due to the weight of the vehicle and size of the braking system, that the steel piston would retain allot of heat and this could cause a boiling of the brake fluid. It would probably not be a problem in stop and go traffic as you are on and off the brakes to letting them cool. The problem would be in a down hill grade where the brakes are applied and used for long periods of time.

So I called the owners of CNC Hydraulics who build racing brakes and peddles. I have there products in my off-road pre-runners and race cars. I spoke to them as they use billet machined aluminum for pistons in their calipers and these parts take huge amounts of abuse. They determined that the billet aluminum would be a better way to go vs. steel, but they would do some serious testing to see if the life span of the aluminum piston would hold up for this type of application. They also agreed that a 66mm caliper seemed a bit small for such a large application. But said the Bosch brand caliper was probably used because it is a production part and it fit the chassis / wheel application used by the manufacture. As far as them making some billet pistons they said no way as this is used on the road and they build racing products and would not want any liability. Also they think the reason these manufactures are using the phenolic material is two sided. One is they dont rust or pit which a steel piston can do. Two is they dont retain heat like a steel piston does. And third and most likely reason is cost. A machined billet aluminum or billet steel product would cost twice or three times as much as the plastic part does.

This is probably the same reason WH or any chassis manufacture does not put quality trac bars, sway bars and shocks on there chassis is because of cost. If you and I can buy a trac bar for $400 then what would it cost WH when they would be buying a thousand of them? Less then $200? I would have spent an extra $200 knowing I would not have to buy aftermarket products to fix the weak points in there product.

Now my friends machine shop said he would build steel or aluminum pistons for me, but when I told him they now have a formal recall we decided to bag the whole project as this could be a huge issue with WH giving me new calipers. Also being a Ginnie pig and testing these kind of made me a bit nervous as my family rides in the MH. If this was in the off-road cars I would not hesitate to try it.

But last this still does not explain why it is taking Bosch and Workhorse so long to fix the problem. Like Oemtech stated his friend is finding possible solutions and yet Bosch takes years to find one.
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Old 04-21-2010, 01:36 PM   #3
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My guess is the reason it's taking so long is government and lawyers.

I don't care how good his system works, can you imagine the field day that an ambulance chaser could have with this if someone was injured and they found out.
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Old 04-21-2010, 02:01 PM   #4
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If it all works he will make the rest of the pistons and probably bypass the Workhorse recall.
Dale, That's not possible. There will remain an outstanding Federal recall on the vehilceby VIN# which will need to be resolved.
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Old 04-21-2010, 03:14 PM   #5
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Wow... This sounds like the replies I got when I started the Fuel Filter Adapter project. So, far I have yet to hear about a problem with it when PROPERLY installed. My has been on over 2 years and has had 3 fuel filter changes. Works as designed.

If anyone remembers when this all started I suspected that the phenolic coated piston was the problem and suggested that they be replaced with stainless steel versions.

It's amazing that when someone takes on a project like this that all kinds of stuff comes out of the wood work. Anyone ever heard of SSBC (Stainless Steel Brake Corp). It's was born out of the early 60's Corvette brake problems. I wonder what would have happened had they listened to the "It ain't going work" crowd.

The piston in question is an exact copy of the original except it has the PROPER clearances. The OEM seal kit fits and works as designed. As for pitting and corrosion, bah humbug. The caliper bore is cast iron and the piston is stainless steel. Which one will have the problem first?

As for expansion rates... The initial test prove that to not true.
Quote:
One last bit of info. He heated the original caliper piston with a lamp he had on the bench. Just in a matter of minutes the caliper had expanded .001. He was able to actually hold the piston in his hand to do the measurement and the piston would not fit in the caliper bore. He then heated the SS piston to almost 400 degrees and it only expanded .001+.
As for bypassing the recall.... This a voluntary recall by Workhorse and I don't believe that there is any law being broken if the end user decided NOT to take part in the recall. Me I op to have the recall done and then get a spare set of calipers and do my own with SS pistons.
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Old 04-21-2010, 04:36 PM   #6
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I never said the steel piston would not work. It was just brought to my attention that the steel piston will retain much more heat and this could be a issue of boiling the brake fluid. As the owner of CNC said cars and trucks that use steel pistons dont weigh 20,000 + lbs. and those calipers can be larger per proportion to the vehicle size and weight. This could be one of the reasons manufactures look at using phenolic.

Also have you researched the fluid passages in the Bosch 66mm caliper? Because a steel piston is going to be heavier and you might need more fluid to push a heavier piston. And yes I understand the smaller the fluid orifice the higher the pressure, but then you get greater heat transfer. Also if I'm remembering correctly didn't Ford use a 73mm caliper on the front of there larger chassis and a 66mm in the rear?

Like I said I was looking at this last year and even had a guy who was a mechanical engineer on RV.net and lives not to far from me, contact me and offer to do some CAD work and split the cost to build these pistons with me. He too felt the steel piston would work and when we talked about Aluminum he was even willing to try that too. We were looking to build them to the exact spec of the plastic pistons and using factory seals just like you are, and also research different options besides just a factory spec's, like caliper boar and fluid passages. But when the Recall was formalize I figured I would just hold out and wait as it could not be much longer and at the time the talk was a completely new caliper design and not just an updated piston like what Workhorse has stated they are going to be doing.

So dont include me in the "Negative Nancy" crowd as I have thought about this and I did do my research.
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Old 04-21-2010, 05:03 PM   #7
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The SS piston was designed on a 3D CAD system. The weight of the SS piston is very close to the original piston.

Sorry to lump you into the "Negative Nancy" group.
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Old 04-21-2010, 07:50 PM   #8
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Here are a couple of photo's...





I will try to get the weights of both...
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Old 04-21-2010, 07:57 PM   #9
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As for bypassing the recall.... This a voluntary recall by Workhorse and I don't believe that there is any law being broken if the end user decided NOT to take part in the recall. Me I op to have the recall done and then get a spare set of calipers and do my own with SS pistons.
Dale, This is an NHTSA Recall. The recall will always show up as being "open" if anybody looks at the vehicle service history. A few years down the road and one accident later, an owner might have to explain why they threw the recall letters in the garbage.
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Old 04-21-2010, 08:29 PM   #10
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What an awesome looking quality clone of the phenolic piston. They do look custom and expensive though.
Driver seems to think that only WH and Bosch know how to fix the problem that they created. They have made plenty of mistakes and their next fix may be another.
The heat could be a problem but the stock brakes dragging create even more heat and also the dragging damages the pads and the rotors. So in theory, the metal pistons, even if they hold heat should do less damage than the stock brakes do.

quote " A few years down the road and one accident later, an owner might have to explain why they threw the recall letters in the garbage."
Apparently WH , their reps, or Bosch, does'nt worry about that for the last few years.
I'd be thrilled if I could have access to and could afford to try those new pistons. And I believe I was one of the first to buy your quality fuel filter mod and contrary to the 'negative nellies' thoughts, it has worked great and I can buy $10 filters any where.
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Old 04-21-2010, 08:59 PM   #11
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Negative Nellies?, I thought it was Negative Nancys.

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Old 04-21-2010, 09:14 PM   #12
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Negative Nellies?, I thought it was Negative Nancys.

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LOL, There's enough for both Nellie and Nancy
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Old 04-21-2010, 09:14 PM   #13
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I'd be thrilled if I could have access to and could afford to try those new pistons.
Max, You can wish all you want to but you are not a part of the campaign.

Max, if the brakes work as designed your theory is faulty. Metal is a 100% better conductor of heat that phenolic. I am not an engineer or claim to be however I can not dismiss out of hand all the testing results that are in the public record at this time in regard to the comparison between these two materials.

The metal piston by the way isn't "awesome" there were already a metal pistons which were manufactured and included in all the NHTSA testing samples and it was benchmarked against all the other test subjects. Did you read those materials? This isn't something new or unique and it's no where near awesome. A computer can crank out these things in relatively no time at all. Whether or not the metal piston meets the design objectives has not been established whereas the new Phenolic design has.

I am not the great thinker that you assume me to be, I only am reporting the facts as I see or get them. If my source is flawed then its garbage in garbage out however you are not going to get me to say that I think that I know how Workhorse and Bosch are going to fix the problem.

I can write an opinion as well as the next person however I am only reporting what I know to be the best news at the moment it is released.
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Old 04-21-2010, 09:18 PM   #14
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/www.ssbrakes.com/ Have been using SS brakes on 'Vettes for years. Best deal is SS caliper bore and piston. Workhorse and Bosch could have fixed this a long time ago. If you like your rig and want it to be safe, spend a little $$ and git er done. Or just keep getting W horsed around. It's oniy your brakes and your family. Or wait for the gov't to save you?? The answer has been for years SS brakes in high temp operations.

I don't work for them, but have put lots of SS calipers on 'Vettes and never had a problem. I also put SS on my 99 Safari when the Bosch problem started. Not a new issue. Good Luck guys. :(
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