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Fri Jan 12, 2007 9:26 am

hello!

Recently I´ve read an interesting question on a german cal-look forum. The black magic is available in two different versions which vary by material thickness. Are there any disadvantages of the thicker one? sounds to me as I can use the thicker one longer due to the thickness, isn´t it? or will I get into trouble cause the (thicker) disc may be too thick for some reasons?

Christoph / DFL

http://www.dflvwclub.de/

Fri Jan 12, 2007 9:48 am

There's a couple of considerations:
(1) A thicker disc CAN cause clutch release issues, because it takes greater pressure/travel to release the pressure platefrom the disc.
(2)thicker disc is heavier, causing spin down problems when the clutch pedal is depressed. This can cause shift "crashing", resulting in premature synchro wear.
I wish to point out that the black magic is a heavy disc to begin with, compared to most others out there.

Fri Jan 12, 2007 10:17 am

I think the thicker disk is .330" ish and is close to stock thickness. the thinner disk is .250" and typically designed for an adjustable PP or a flywheel that has been cut deeper on the PP register.
but that doesnt mean that the thinner disk will not work on a regular PP, but you are starting to go out of its normal range.

Fri Jan 12, 2007 4:09 pm

IMO a BM disc should not be used on a street driven car. Because the disc is so heavy, it has a lot of inertia. It's inertia is so great that VW syncros can't slow it down quick enough when you are shifting quickly. Bent syncros are what a BM is known for.

Fri Jan 12, 2007 4:27 pm

Bruce wrote: IMO a BM disc should not be used on a street driven car. Because the disc is so heavy, it has a lot of inertia. It's inertia is so great that VW syncros can't slow it down quick enough when you are shifting quickly. Bent syncros are what a BM is known for.

:? Ya think Bruce? The majority of the cars we've used the Black Magic disc in have been street cars & I've never seen any issues what-so-ever. What I have seen are the benefits in longer transmission wear / life & smoother shifts at the track. The Black Magic (AKA McLeod Cindered Iron Clutch) is designed to allow some slip & when driven properly can be a huge asset.

Sat Jan 13, 2007 4:05 pm

Ann Mezger wrote: Bruce wrote: IMO a BM disc should not be used on a street driven car. Because the disc is so heavy, it has a lot of inertia. It's inertia is so great that VW syncros can't slow it down quick enough when you are shifting quickly. Bent syncros are what a BM is known for.

:? Ya think Bruce? The majority of the cars we've used the Black Magic disc in have been street cars & I've never seen any issues what-so-ever. What I have seen are the benefits in longer transmission wear / life & smoother shifts at the track. The Black Magic (AKA McLeod Cindered Iron Clutch) is designed to allow some slip & when driven properly can be a huge asset.

Sounds like you guys out east don't drive your cars very hard.

Have you pulled apart gearboxes that were used with BM discs? The last gearbox I pulled apart that was used with a BM was shifting just fine. But 2nd, 3rd and 4th gear syncros were all bent. It was only a matter of time before that would have been grinding.

The sintered iron clutch disc weighs a LOT more than other types of discs. When you increase the rotational inertia of the input shaft, you will never get "smoother shifts at the track". If you demand more from your syncros, you will have more chance of grinding gears.

Sat Jan 13, 2007 4:22 pm

Bruce wrote:
Sounds like you guys out east don't drive your cars very hard.

You might want to go watch the videos on my website www.vintageperformance.net ............ we're definitely NOT easy on them. You just don't stuff 500HP in the back of a bug to be soft. :lol: Most, if not all of the cars I've posted video of have the black magic disc installed. Not only do they get the shit kicked out of them at the track, but these same cars rack up quite a bit of street miles as well....... after all that's what they were built for. Before using this clutch, we HAD to pull trannys out at least every year. Now the same cars are keeping the gear box together for several years, even after adding HP to the engine. One of many very good examples I can give is Jersey Joe's '68 with the 2387cc Nitrous engine built by Kurt. It's been over 4 years since his tranny was last touched. I assure you I am no amature & the performance of this clutch in our street cars is not dumb luck. The BM clutch works exceptionally well for both street & strip use.

Sat Jan 13, 2007 4:31 pm

Unless you have my driving style. it is just still too heavy for me.

Sat Jan 13, 2007 4:59 pm

Ann Mezger wrote: Bruce wrote:
Sounds like you guys out east don't drive your cars very hard.

The BM clutch works exceptionally well for both street & strip use.

I'm happy for you then.

Bruce wrote:
Have you pulled apart gearboxes that were used with BM discs?

If you re-read what I previously posted, the problems created by the BM disc have nothing to do with the amount of hp the engine makes. The sole problem of bent syncros is created when you shift the gears really fast. Obviously you are not shifting that fast.

Continue to granny shift them, and you will have many more reliable years.

Sat Jan 13, 2007 6:16 pm

I completely read your prior post Bruce. I have actual experience with using this clutch under many different circumstances, in several different cars, with several different drivers. What experience do you have with this clutch Bruce? How many times have you used this clutch? 20? 10? 5 times? Never because of what you theorize to be true? I'm curious to know?

To answer your question - YES we have torn down gear boxes to inspect them for damage that was NOT present. If I have 20 cars running the BM / McLeod clutch with 20 different drivers, are you really trying to tell me that they ALL granny shift & that's the ONLY reason for good results & not bending syncros? :roll:

BTW - we made the switch TO the Black Magic clutch based on advice from my tranny builder, Jim Kaforski / Der Transaxle. Maybe you should give him a call next time your tranny needs repairs Bruce - then you can hammer it & have reliability all in the same package. :D

Sat Jan 13, 2007 6:24 pm

I love my BM!!!! It worked great!!! chewed my pinion gear, Bent 4 syncros and did great wheelies. My 60ft's got slower too!!! Snapped my 1st gear also!!!

My previous Ace copperhead had faster 60fts, Softer launch with less wheelie and my R/P lasted longer.

Granny shifters with turbos will be easier on the syncros since the PSI on tap will just still make a fast 500HP street car. Naturally aspirated cars have only "X" amount of HP limited to the c/r and headwork while a turbo has the luxury of "upping" the HP by increasing the boost when they feel like going on a dyno or one last ditch for the killer ET pass. (pray something doesn't let go)

IMHO keep the BM's for the big boys with big HP. For the guy with the 200HP damn fast street car you DO NOT NEED a heavy syncro bending BM. Its funny how the internet forums have people "hush hush" or now many guys just dont bother putting the effort in sharing experiences over the net. I've talked to many guys that have busted tranny parts because of the BM. These are guys that dont bother to post anymore on forums.

Hardcore setups should be using floater clutch systems anyways. You can adjust the clamping force so you can control your launches better.

I'm vocal because there are so many people out ther going WAY OVERKILL on clutch clamping pressures and hard abrasive clutch disks for 170-200+ HP weekend warriors/street cars.

http://members.shaw.ca/acvolkswagen/Trannyblow.htm

I'm glad it happened. FTC and Weddle gear this, and quaiffe that, I now have a stronger trans because of the BM experience.

I highly disuade using the BM unless your a granny shifter and NEVER EVER powershift. If your easy on your transmission you maybe one of the fortunate people with no issues. Just remember the BM is a seriously heavy clutch compared to rag type stock solid performance discs. Heavy weight means more momentum. Something takes up the slack and must speed up the next consecutive gear. The syncro will take a beating. If you dont believe me buy one. You'll be one of the guys selling a BM on the Samba classifieds. If it works out for you the BM is a beautiful clutch since you can sandblast it and slap her backin the car.

I had NO problems with my BM and stage 1 (shimmed for less pressure) when I drove aggressively on the street. First day at the track I bent 2nd syncro and who knows when I bent the other syncros. I NEVER had issues using my ace copperhead lighter clutch disc. My driving style has NOT changed either. I do not powershift either. The BM didn't work for me.

BM bites hard unless you shim a kennedy stage 1 or use a stock pressure plate. Shockload will do nasty things to your car. If your street car is heavy its even harder on transmissions.

If you're really into preventative maintenance and pull your tranny every year the BM will be fine. Just change the syncro and r/p every year. You must pay particular attention to chassis tuning so you dont go stupid on 2-3 feet wheelies which by the way shortens the life of the r/p.

Sat Jan 13, 2007 7:17 pm

i had good luck in the begining. then it got progessivly worse to wear i couldnt even shift from first thrue 4th without grinding we toar the box down loland behold broken sncrows. sprung for all new brass put it back togerther with the good old cush loc. old blue is shifting good again power shifting second no problems. you can have the BM DISC. if i up date my clutch agine this year it will be with the old DDS double disc that i ran years ago i never had a problem with that setup like the cush loc. my two bits jeff d.

Sat Jan 13, 2007 7:35 pm

Bruce wrote:

Continue to granny shift them, and you will have many more reliable years.

BTW Bruce, The LAST person in the WORLD who could ever be accused of granny shifting anything is Jerry Spearn. Wanna take a wild guess which clutch he's running? :twisted: Oddly enough, he loves the BM so much that he's re-used the same disc with every engine combo (1915cc N/A, 1915cc Turbo, 2332cc Nitrous, & 2332cc Turbo) that's been stuffed in his ovals for the past several years. AZ Transaxle did his gear box ............ How do Jerry's trannys stay mint? :?

Sat Jan 13, 2007 7:53 pm

It seems you're the ONLY one in this thread that DOES like the BM...I won't use them for street use.

Sat Jan 13, 2007 8:20 pm

Ann Mezger wrote: What experience do you have with this clutch Bruce? How many times have you used this clutch? 20? 10? 5 times? Never because of what you theorize to be true? I'm curious to know?

It is not a theory. It is an explanation based on what I saw with my own eyes (bent syncros). I have driven cars with BM discs, and they do work just fine. The chirping is kinda funny too. Their only drawback is they bend syncros. When I first saw all those bent syncros I was baffled at why they would be bent. Then in talking to others who used the BM, they also confirmed they had bent syncros, that it is common with the BM. I would like to make it clear, I had never heard of the bending syncro problem until after I asked around which was after I saw all the bent syncros. It wasn't like I was looking for bent syncros before I took the gearbox apart. Have you actually checked the flatness of syncros used in gearboxes that were used with BM discs?

Ann, I'm sorry that me posting about a BM's proclivity to bend syncros is gonna cut into your shop's sales of BM discs, but I hope it will save others from having to get their gearboxes re-synchro'd.
I'm also happy for you that all your customers granny shift their gearboxes. It's too bad you are half a continent away, otherwise I could show you how we do it.

Sat Jan 13, 2007 8:26 pm

The Noof wrote: It seems you're the ONLY one in this thread that DOES like the BM...I won't use them for street use.

Well DAAAAMN. :shock:
Quick .... somebody needs to tell Shawn Geers & Ron Lummus to quit selling them to people with street cars. :lol:
We've installed the BM clutch in more street cars than the number of people who have posted so far Noof & I have yet to hear 1 complaint. What it comes down to is personal preference, not that the clutch has a flaw in street use. To express that you wouldn't use it on the street is fine - that's your opinion & you have you reasons. (whatever they may be) However to say that the clutch will cause damage to syncros among other complications & should never be used on the street like someone else did is wrong unless it can be proven as a fact that the clutch is what caused the damage. Excusing my successful experience by reason of "granny shifting" is lame.

Sat Jan 13, 2007 8:36 pm

Bruce, As I already pointed out we DO check everything completely. I'd waste a lot of money shipping a tranny to CA just to have it looked at. They only go when there is a problem.
As far as "cutting into my shops sales" ......... NO WORRIES. I don't promote the use of the clutch to make a profit. I promote it because it works. No need to fret about the driving skills either. Just don't tell anyone we're taking it easy on our cars .......... I wouldn't want them to think 143MPH 1/4 mile in a 2150lb. car was a simple Sunday drive. Let them think that's all it had in it. :lol:

Sat Jan 13, 2007 9:22 pm

I am no tranny expert by any means, nor will I pretend to be one. However I will tell my actual real life experiences.

This year I was only shifting at 7600rpms (shift light) and later started to shift at 7200rpms making the same ET's and MPH. I step on my clutch on every gear and I also let off on the gas as I shift. I DO NOT powershift.

I am aggressive on each consecutive gear but I NEVER bent syncros like the BM did. I have NEVER destroyed a tranny like I did with a stock type lighter clutch disc.

Yes I was running a stronger 9 tooth stock 1st/2nd mainshaft with bus ider (wider and stronger than type 1). I dont know how any tranny builder can screw up the assembly of a gearstack with the sycnros and sliders. Yet I bent my sycros.

Speaking with many guys out there you'll bend brazilian or even NOS OE vw german sycros or mint used OE vw sycros.

For race pro-ringed setups you wont careless but syncro you will.

the shockload of the bm and weight of the disc are not ideal for a 200hp "enthusiast" real street car. If the BM isn't setup right with a softer pressure plate you will hit the tranny real hard with shockload and the the momentum of the disc will be harder on sycros. This is not hearsay or speculation. Its physics.

You can roast the disc and then sandblast it and it'll be new. This is why I wanted one. Also you can use a stage one kennedy pressureplate. You MUST shimm or face the shockload consequences.

Some guys jumping on the BM bandwagon will be happy and some sad. I am statistically one of the unfortunate ones but there are more unfortunate than fortunate.

My copperhead disc is going back in with a stage 2. My BM is gonna sit on my spare parts bin for discussion purposes. It may go in a street car with stage 1 that never ever sees the track with slicks. Otherwise the track will find weakness due to traction and high rpm momentum.

I do not care who builds a tranny. Even taking off teeth off the syncro for quicker bite still wont prevent bending. All walks of life has bent sycros with the BM. All walks of life do not get the same tranny built in the same exact tranny building shop.

The shimming of pressure plate I can easily deal with but weight of disc is the other huge negative.

A heavy disk WILL CAUSE ISSUES. If the input shaft doesn't slow down quickly it will spin the gear stack which in turn makes the syncro ring work harder to spin up the next consecutive gear. THIS IS ALL ABOUT ENERGY. A lighter clutch disc will have less momentum so the input shaft will slow down faster compared the the freight train momentum of the BM which will continue to spin as you step on the clutch pedal.

IF you "granny shift" you leave a longer PAUSE between gears so that gives the input shaft more time to slow down. Easier for the sycro and less chance of grinding gears.

Street use the BM is absolutely fine. On the street you shouldn't be driving in that kinda unsafe manner. At the track in a "STREET" car you will shift quickly and clean as possible to not lose time. Momentum from the extremely heavy clutch disc is what slams sycros when you shift quickly.

Sat Jan 13, 2007 10:10 pm

That disc material was originally developed for fork lifts back in the '60s. It was tried for race/street use back then and guess what? It ate synchros. But those were Ford top loaders and Muncies.

I spent many years in the clutch biz back in the day, and the BM ain't a new product, just this application. Not saying its bad, just some results do vary.

Sat Jan 13, 2007 10:13 pm

Ann Mezger wrote: However to say that the clutch will cause damage to syncros among other complications & should never be used on the street like someone else did is wrong unless it can be proven as a fact that the clutch is what caused the damage. .

We've already proven the disc causes the bent syncros. It is called an A-B-A test. Condition A is using a stock style lightweight disc without bent syncros for many years. Then condition B is using the BM disc, and the resulting bent syncros. By switching back to the lightweight disc and seeing no more bent syncros PROVES the BM disc causes the problem. Many others have involuntarily done this sequence of testing on the street and track.

Remember this post from Jeff:

jeff denham wrote: i had good luck in the begining. then it got progessivly worse to wear i couldnt even shift from first thrue 4th without grinding .

A bent syncro doesn't grind right away. In fact, Alan's trans was not grinding at all when it was pulled apart. 2nd, 3rd, and 4th gear syncros were bent quite significantly. Given more time, he would have experienced what Jeff did.
I'm sure as time goes on, some of your customers will report back that their gearboxes are grinding gears. And I know that being the honest person you are, you will post this here, right?