It is becoming increasingly common to see 348's with broken diaphragm spring fingers. There a few theads highlighting it. This prompted me to look further into it. I use a consultant engineer to rebuild my clutches, and between us, it hasn't taken long to work out why. The clutch diaphragm is being overthrown, due to either excessive pedal stroke, and/or oversize clutch master cylinder and/or undersized clutch slave cylinder. Further to this, your clutch diaphragm is actually more prone to breaking if you have had "precautionary" clutch changes... often sold by dealers as a "while the belts are being done....etc" The reason here, is that with a new clutch fitted, the diaphragm is already flexed a fair way (the fingers are flatter) before you even press the pedal, so operating a "new" clutch, overthrows the diaphragm even further than once it's worn a bit and the fingers have rasied a little. This constant overthrowing gradually fatigues the diaphragm spring, until after X amount of operations and heat cycles, it begins to fail. City driving is a killer in so many ways. The solution..... either fit a pedal stop to reduce travel, or replace the master cylinder for a smaller bore size. A smaller bore M/Cyl is the best option, as it also gives better feel and graduation during take up. I'm investigating easy options here, and will let you know.
Thanks. Nice write up. Should the clutch pedal stop be 2.5cm or less for 348's on non-original clutches? Would this modification be appropriate to add to the 348 clutch change procedures?
Unbelievable timing for this post! I was at Krause & England (Raleigh, NC) today speaking with Peter about that very issue. He has an amazing 348 dual disk clutch with about 6 broken fingers. I'm sure he'll post some pictures soon. I was there to deliver the dual disk clutch and some other replacement items. This particular car was a 1991 model (if memory serves) and was going through its second (at least) clutch. Ferrarifixer -- I'm no mechanical engineer, but are there any metals/materials which would the design of a continous spring (it would almost look like a shallow funnel) instead of the fingers?
err.. not sure what you mean with 2.5 cm and non original clutch. I'm thinking a new M/cyl is needed, and could be installed at any time... sooner the better really.
You need the fingers... as the gaps between them allow the disc to "shrink" as it is deflected. Without the gaps, ie a solid disc, it would "plink", and get stuck in the released position, without releasing..."plonk". In engineering terms so to speak.!
OK. I was just trying to draw out the proper dimension for the clutch pedal stop if one needed to install that as an interim fix until a smaller master cylinder could be found. I'm presuming that we're talking about master cylinder # 175211 (shown in picture), and that some smaller size and different part # (obviously) is required. This is connected directly to the clutch pedal and resides just under the brake fluid reservoir in front, correct (as in, not an enormous job to replace)? Image Unavailable, Please Login
Also, I'm presuming that no "fix" for the existing master cylinder is viable (e.g. some sort of plug to reduce m/cyl volume).
Just a refresher pic of my clutch that my main man ferrarifixer has. Does the clutch Peter have look like this?? Image Unavailable, Please Login
Two questions. 1) If you went with a smaller master cylinder wouldn't that affect the stopping power of the breaks? Since both the clutch and break calippers run off of the same MC. Don't the F40's have problems with the MCs not producing enough force causing break fade? So wouldn't reducing the MC also reduce the amount of hydrolic pressure available of proper breaking and clutch operation? The smaller the mc the less pressure it can make, no? For around town I don't think it would be a problem, but what about on those track days, or spirited runs on the twisty back roads? 2) If you were to reduce the amount of travel on the clutch peddle, how can you be sure that the clutch is fully disengaging? I know when I had a new clutch and flywheel put in my car the height of the disengagment was pretty high. Now over time it should lower as the clutch wears, and as a result the height at which the peddle fully disengages the clutch gets lower. So if by adding a stop to the back the the peddle, wouldn't that prevent the clutch from fully disengaging from the flywheel and the clutch wears, because the peddle isn't being pushed down far enough?
err ernie.. I think you get too much sun in south cal.... firstly.. its brakes, not breaks... but the scary part is you thinking they share a M/Cyl with the clutch....... *shudder*!! Reservoir only mate. second point.... sounds like you need a bleed... the clutch engagement point stays the same with hydraulic clutches, unless you've got air in it, or it's so worn out and/or the fingers are failing that the car doesn't move until it's half way engaged....
Pap - That's pretty much it! The innerds were a bit scracted/scored too from the fingers getting tossed around like a food processor. Those fingers are actually quite stout. It's not like they're delicate little things. It would be fun to use a trashed plate for some heat/stress testing and see at what point they fail.
Recently worked on a 348 ts clutch (helped) and it looked very different than the one shown above. The fingers were slotted. That is they had a slot cut in each finger in the area in the middle of each finger, also the plate shown around the fingers was different as well. Is it possible that Ferrari made changes to this assembly? The name on the assembly said Borg.
LOL. Okay since those questions are taken care of, question #3. Has this problem, with the busted fingers, been on the dual clutch cars, single clutch cars, or both?
The PP I have removed from the November 1991 348TS that Daniel refers to looks EXACTLY like ferrarifixer's pic. As a matter of fact, it is close in serial number to the one in the picture. This is more likely an age-related, fatigue issue rather than a hyper-extension issue, IMO. Pics Monday... -Peter
Well what do you know. AP Racing uses a Borg & Beck clutch. I wonder how much cheaper it would be to just buy the clutch from Borg? I can't quiet make out the part number on that pic. Plus I wonder if Borg has an update for the diaphram fingers?
Just curious,is that a single plate clutch Sue? Or a twin plate?? It seems to have just 3,allen headed bolts that keep it all together,when mine has 6 bolts? Maybe because it is a BORG?? Mine is an AP clutch,just different designs maybe hey? Cheers
And what the hell is that silver crap in the bellhousing around the clutch?? It looks like foam expand looking ****?? hehe.
Thats a later type single plate clutch like a 355 one. And yeah... what IS that goo.. was it on fire?
I found this while looking for BMW parts for my 330cic & 325is I don't think I would want to mount this to my car. Looks like it mounts to the floor. I'm not going to drill MY floor! would you? Image Unavailable, Please Login Image Unavailable, Please Login
The goo is grease from the Assembly. That's why we pulled the thing in the first place. It seems that the seals on the shaft (3 small rings) went bad and caused trans fluid to get into the assembly. It loosed the grease and this is the result. Works great now that the seals were replaced. Yes it is a Borg clutch, single plate. After looking into it this was a recommended upgrade for the 348, similar in nature to the alternator upgrade. If one looks at the parts book it shows a breakdown of the old clutch and indicates it is obsolete. Hense the original thread is spot on, the clutch is poor in design and recognized so by Ferrari.
I agree fatigue. I don't know how 348 people destroy these clutches. I run an "obsolete" dual disc in my 348 race car with the only clutch mod as no grease pack and voight crap on a solid flywheel. I'm probably 6-8lbs lighter and drive my car harder than any of you. My clutch is 5 years old now and it still has not blown up. I hope I have not jinxed myself. I have seen clutches destroyed by placing the pumpkin on the car v.s placing the clutch/flywheel pack on the shafts first and then the pumpkin. "NoDoubt" where is the thread where we had the giant discussion of the flywheel pack positioning and the little grub screw? We talked about this here. Also, I think the dual disc is obsolete because it was too hard for FNA mechanic part replacers to replace them not because of a bad design. Also, cost is a huge issue with Ferrari. There is no doubt... ask any racer the value of single vs. multi-disc clutches. Racers use multidiscs. Streetdrivers is just doesn't matter. Even with the latestes 348/355 design for example there are pictures on this board of Throwout bearings that have actually split open. That never happened to the old first gen T/O bearing. In fact the old T/O bearing could be rebuilt. I know because I have done it. This is just one example...so how could anyone say the latest design is really the best one? We just don't know why Ferrari does things but we all want to think they do it for better cars. Look at any Ferrari build quality you know they suck. Here is the best DIY'ER tip and please remember it. When you are trying to work on your Ferrari the dumbest, cheapest way to handle a problem is the way that Ferrari designed it.
