Why Hydraulic Throw-Out Bearings?

[David Kirkham]

Jeff,

"Off the shelf" I guess. We use CNC brake parts slave cylinders.

http://www.cncbrakes.com/sc.asp?grp=...305&subseries=

We could make them ourselves, but they gave us a good deal and so I don't have to worry about making them ourselves. If they price gets too high, then we will make them ourselves and I think people know that. They work really well. The pedal effort is 1/2 the McLeod hydraulic throw out bearing and probably 1/10th of a Tilton...ok, I am exaggerating, but we did use one to catch a grizzly once...

David

[vettestr]

Thanks for the information and keep that grizzly fat n happy. Jeff

[David Kirkham]

I actually DID catch a bear once...a black bear. He was terrorizing a Boy Scout camp were I worked. One night I was walking back from the campfire and I ran right into that bear...I could have reached out and petted him. Oh man, what a scare. If you have ever seen a bear running through the woods, you would die. There is NO way you could ever out run one. They are scary fast. Well, my number wasn't up that night. The next day I saw him tear a "bear proof" box apart and eat an entire bag of Oreo's...and I do mean ENTIRE bag...like bag, paper, cookies, wrappers, everything. He then ate all the canned peaches (just tore the tops of the can off like they were paper). He actually avoided the canned beans. I always wondered if that bear could read!

BUT,

When he pulled a boy out of his sleeping bag the following night, we decided it was time to do something. We set up a 55 gallon drum trap and baited it with watermelon and cantaloupe. Boy, was he MAD when that door slammed down.

Boy were we glad to get rid of him!

David

[RICK LAKE]

David Kirham Yes those black bears are alot of fun. Played with some at space farms back in the 70's. Couple of 70 pound cubs that the mother was killed by auto. No front claws but they would knock the crap out of you at this small size. MY dumb state people have brought them back into NJ. We already have a Major deer problem. Now the beers are moving into towns. There have been some attacks of pets and pets driving off bears but the day is coming when a children is going to get killed and all hell so going to break loose to this dumb idea. We kill about 200 bears a year during hunting season now. Any way Had a question about failures on the TOB and fluid. Did you try hydrolic fluid from contruction machinery? My thinking is that there are sealings in the pistons, slide up and down thousand of times, and last for years with no leaks if kept clean from dirt? I have been using the ERA system for 10+ years and have not changed the fluid in the Clutch system. I have no leaks to date. The only dumb thing "I" did was install a piece of rubber high pressure hydro line between the fluid reservoir and line going to the master of the clutch. No leaks, I do check the fluid for color and water moisture. Still passed the tests. This also supplys fluid to the brakes. Being a slow driver and not pounding the brakes and cooking them may be the reason for the fluid to be OK. It should get changed about every other year. When you have everything working OK, you hate to mess with anything. Rick L

[Anthony]

David Kirkham, this topic has been brought up several times before over the last 8 - 9 years. If I remember correctly, you used to be a proponent of the mcleod hydraulic through-out bearings. Glad to see that you come around to my point of view.

Anyways, you mention DOT 3 vs 4 brake fluid. I was under the assumption that DOT 4 was a more "refined, synthetic" version of DOT 3, and really there wasn't much chemicaly different between the two, other than maybe more "stable" molecules of the same family, kind of like comparing dino vs synthetic motor oil. You can mix DOT 4 and DOT 3 I believe with no problem. Unlike DOT 5 which is ?silicon based, and is not compatable.

Maybe DOT 5 would be good to use in the Mcleod through-out bearings. I'll still stick with my external set-up.

For every person changing from external to internal through-out bearing set-up, I bet there are 20 changing from internal to external. Kind of like doctors and Canada. I know of one doctor who moved from the US to Canada (for LOVE) , and about 20 or 30 who have moved from Canada to the US for --- you know the reason.

[lovehamr]

Had to put my 3 cents in......................


I think Yogi's pissed. BaaaaHaaaaa!!!!!!!!

[vettestr]

partial quote

Originally Posted by David Kirkham

Jeff,

"Off the shelf" I guess. We use CNC brake parts slave cylinders.

David

Knowing you Kirkham Boys tend to do things a little over the top I just wanted to make sure I was not overlooking anything. I have not had any issues with our external slaves but will always take advantage of the experiences of a trusted source.

[Ronbo]

One of the biggest problems with DOT3 fluid any corvette owner can tell you...

It absorbs moisture. This causes pitting on the pistons and calipers if it's not changed out on a regular basis.

Why DOT5 seems to be avoided by everyone except GM on the Corvette only I don't know, but I'd imagine seal compatibility (and cost) is one factor.

DOT4 removes the moisture problem without having to change seals from DOT3, but I'd still change it out regularly. Brakes get mighty hot so the fluid probably breaks down over time as well.

[Jamo]

Ronbo...yup re Vette application.

I ran into a bear Sequoias (a yearly thing) whaen I was 13 or 14. All of my cousins and I were running back to our camping area from the Camp's nightly bonfire. I was winning by a small amrgin, and I could hear my folks, uncles and aunts yelling. Thinking they were urging us on, I put my head down and picked it up. Bam! Ran right into a momma bear who was scrounging the Camp garbage cans. She grunted when I looked up at her. I ran into the cabin and slid under the cot...she and the cubs evidently ran the other way.

To this day, the distinctive smell of bear fur at a zoo makes me a bit nervous.

[poboy427]

I bought mine HTOB back in about 2001 along with my Street Twin. At that time I put silicone brake fluid in it and that lasted only hrs before the o-rings desinigrated. I put in new ones and Red at McCleod said to run just reg DOT 3 brake fluid. I have had no trouble since. I flush it yearly, same with brakes.

[JayBar]

Hydraulic throw out bearings are stock in Corvettes since 1997. I have a 2000 with 89,000 miles on it. I never touched it except to change the fluid. I only wish it had an external bleeder.

I have replaced 3 Wilwood external slaves on my BDR, in 5,000 miles.

[undy]

Originally Posted by JayBar

Hydraulic throw out bearings are stock in Corvettes since 1997. I have a 2000 with 89,000 miles on it. I never touched it except to change the fluid. I only wish it had an external bleeder.

I have replaced 3 Wilwood external slaves on my BDR, in 5,000 miles.

The new C6 Z06s are frying the clutch fluid right away, depending how agressive a driver you are. I was sucking fluid out of the Master cylinder with a turkey baster in mine every two weeks and replacing it with fresh fluid for the first year or so. I still do it once a quarter or so. If not the fuild turns black and the clutch pedal ends up sticking to the floor. That's the one big problem with a HTOB, the heat from the clutch is transfered directly to the fluid.

Dave

[ratsnst1]

I know Dave that your cobras, are top notch, if you would have mentiond, that it was a fluid problem, I would not of replyied. why didnt you say from the begening, it was a fluid problem, you were bashing the throw out bearing, it works very well, I dont need to run dot 5 bfluid. mcleod will tell you guys dont run dot 5. so your telling me that you ran dot 5 syn, anywayes. I new not too. mine works very well.

[ratsnst1]

Okay my bad, I did not now that no matter what fluid you ran it was blowing seals, how many miles did it take to do this or was it from the get go.I have 2500, miles on mine and I drive it very hard, no leaks.

[Aussie Mike]

A lot of us running Chev Gen3s down under are using the T56 with it's Hydraulic Throwout bearing setup. I believe their HTO is made by AP (There was an AP in the casting of one I removed).

They do tend to turn the fluid black but I'm not sure why. It hasn't affacted the performance yet and it's pretty easy to flush the fluid through.

We've had couple of problems with them. The first was the size of the line from the M/C to the HTO. Most of us are running braided lines and initially used #3 Line. This was to restrictive and slowed the fluid returning to the M?C after releasing the clutch. The clutch would slip a bit until the returning fluid was pushed back. Switching to a #4 line fixed this problem.

Finding a M/C to suit was a problem too. You need about 11 or 12cc of fluid to disengage the clutch. Most have settled on a 1" bore cylinder. I found a 7/8" with a slightly longer stroke and it works great. The pedal is light which is important for me as my left knee is stuffed. I've also got a heavier after market pressure plate and coper/ceramic puck style clutch.

There's no adjustment on these HTO setups though so adapting them up to another application would mean machining shims etc. As your clutch wears your engagment point will change. The original pressureplates where self adjusting but that has proved troublesome. A adjustable pedal is a better solution.



Cheers

[CobraEd]

I never understood the desire to use a hydraulic clutch when cable clutches work flawlessly year after year, no, make that decade after decade. They are easy to adjust, easy to install, never leak, never break, and no fluid to bleed or change.

Now I could see that the use of a hydraulic clutch might outweigh all of these disadvanteges if they WORKED BETTER. But they don't! They do not function any better than a cable clutch.

I am really puzzled by all of this.


.

[Roscoe]

The majority of complaints I've seen have to do with the McLeod bearings. I've had a Tilton Racing HTOB in for 10 years and over 26k miles with no problems.

Roscoe

[strictlypersonl]

As things get more and more crowded in the engine compartment, the advantage of hydraulics becomes more apparent. Cables require large radii to operate smoothly and that's sometimes not practical.

In addition, some systems of hydraulics operate at zero-clearance, allowing the whole mechanism to use higher mechanical advantage because there's no slack to be taken up anywhere. Cables may have an automatic adjustment mechanism, but it's a stepped take-up, not continuous.

[convincor]

not to mention cables break, fray, stretch. Quadrants crack.
I'm my opion I've never had better control than with a hydraulic, and less pedal effort.
I don't like internal due to the expense, and the expense if it fails to have to replace the T/O plus the clutch because it's soaked with fluid. That just turned into $800+ in parts.
My set-up posted above, the only parts of the hydraulic system that could fail is the master or slave. And both are only $60 parts.

[David Kirkham]

Originally Posted by ratsnst1

Okay my bad, I did not now that no matter what fluid you ran it was blowing seals, how many miles did it take to do this or was it from the get go.I have 2500, miles on mine and I drive it very hard, no leaks.

Usually we only got 200-1000 miles out of them before the seals disintegrated. Hard driving doesn't have anything to do with it as everyone pretty much drives their cars pretty hard--why else would you own a cobra

I must say, I have never heard of a Tilton failure. All of our problems have been with the McLeod units. Also, I must add, I have a McLeod unit in my car that has been in for around 10 years with no problems at all. We isolated (we think) the problem to McLeod units that were made about 5 years ago and younger. The old units didn't seem to have the seal problem. As for what they make today, I really can't say if the seals are good or bad but there is NO WAY I am going to find out (except for checking this board for a poor soul who didn't heed our advise).

After losing thousands and thousands of dollars pulling transmissions out of cars to figure out what the problem was, we gave up and utterly REFUSE to use a McLeod hydraulic throw out bearing, period. (Tilton, is another story and we would use them, but ONLY if we absolutely HAD to.)

But, the internal units make the pedal extremely heavy. Those people who say the internal unit makes for an easier pedal were not using the system we developed. The throw out bearing system we developed is far, far easier to push than any hydraulic unit I have ever dealt with. In fact, it is so much easier that we re-engineered the system to work on the billet chassis car we are making. We originally put a Tilton unit in the billet car because of extreme space constraints, but after driving the car on the track I said that Tilton, bear-trap monster had to GO!

As for fluid, DOT 3 vs. DOT 4, I have no idea--I always thought DOT 4 was DOT 3 compatible as well. Personally, I think McLeod was feeding me a line and they probably had no idea what was going on when they told us to switch from DOT 4 to DOT 3. Like I said, we finally called our buddies at Ford and they directed us to Parker. We talked to a Parker seals engineer and he was the one who told us about sulfur vs. steam cured ethylene-propylene o-rings.

As for using normal hydraulic fluid, we did think about that, but there is a MAJOR problem. NO ONE thinks to put hydraulic fluid in their clutch...they only think to put in brake fluid. Eventually, we would have had a BIG problem. So, we solved the problem by BANNING the McLeod hydraulic unit from the the shop.

Now, I have to say that we still recommend McLeod clutches, flywheels, and pressure plates--but their customer service has gone to crap since my good friend Red Roberts sold the company. It is really sad. I wish they were better.

David