What's the bottom line on a 512BBi Clutch?

Just an opinion, and to be clear, I'm not a Boxer owner, but a 550 Maranello owner and was in a similar situation as you with a new clutch that was very grabby.

The 550's stock clutch is a single disc type, lined with organic friction material. I had this replaced with a triple disc, metallic lined clutch with lightened flywheel from OS Giken. Metallic lined clutches are notorious for having "very" positive engagements, and the additional number of discs only makes it worse.

To mitigate the On/Off toggle switch behavior, I "retuned" the hydraulic circuit so that the slave cylinder would have a shorter stroke, for the normal stroke of the master. To do this, the master must displace less fluid when it strokes than before, which means its bore must be reduced.

There are two ways of doing this:

1. Reducing the bore by having the master rebuilt and sleeved. I don't recommend this, or I should say, I don't know anyone I could recommend to do this. I do know a shop in California that does this, and that I would NOT recommend, however.

2. Finding a similar master cylinder with a smaller bore.

I believe your Boxer has a master cylinder with an 11/16" bore, so you could try to find a similar master with a 5/8" bore. I don't think you'll find one in the Ferrari parts catalog, but you may find one from an Alfa - they use the same vendor for master cylinders, and it's rumored some of the earlier Alfas had 5/8" masters.

After an unsuccessful search for an Alfa master cylinder, I resorted to fitting an aftermarket 5/8" bore master cylinder to my 550, and had to do a little adapting of it to make it work. It's very functional, and has improved the engagement of the clutch tremendously, making the car much easier to drive. As a side benefit, the clutch pedal is quite a bit lighter now too.

 

I have the same issue. i dont mind the on off effect, but the clutch engages at then end of the pedal travel, ie far from the floor which makes modulation difficult, any ideas on a cure adjustment?

 

Thanks! I'm a big Boxer fan - wanna swap titles?

15K miles seems to be a fairly typical interval for changing the OEM 550 clutch, and I just felt that wasn't good enough, so I was looking for something more robust, plus I wanted a lighter pedal so that my wife could drive the car without straining, if she wanted to. Multiplate clutches typically don't require pressure plates as heavy as single disc clutches to handle the same torque, due to the increased area of their friction surfaces, so you wind up with a lighter clutch pedal.

Just FYI, I'm not the only owner who's done this. FChatter mk_e also "retuned" his hydraulic system ratio with very good success after he changed to a multidisc clutch on his supercharged 308 project.

I agree, go after the slave if it's easier to get to, and I've done just that for other cars. Obviously you need to perform the opposite operation on the slave as the master, ie to get a shorter stroke on the slave, you need to overbore it, or find a slave that already has a larger bore. If you overbore, be very careful which shop you choose to do it, and don't forget, they'll have to come up with a new set of seals and a new piston for it. You also need to be sure your slave casting has plenty of reserve thickness for the overbore. Start with a 1/16" overbore, and if it doesn't produce the desired result, go for another 1/16". A 1/8" difference on either the master or slave produces a really big change in the stroke and in the clutch pedal feel. For example, if you change to a 5/8" master from a 3/4", the stroke of the slave will be 1/4" shorter for the same stroke on the master as before, which is a 30% reduction in the slave stroke.

The change in pedal effort will be proportional to the change in bore area, which is the same as the 30% difference above, so your pedal should be roughly 30% lighter. mk_e and I both refer to our clutch pedals as being "Honda-light"

Can't speak to the issue of the components not being engineered correctly. I'm really not qualified to give an opinion on Boxer specific parts. We 550 owners certainly have many frustrations about the quirky engineering in our cars. Part of the "charm", right?

Your clutch could be nearing the end of its service life, unless it's always been that way? If it's always been like that, you could try shortening the actuator rod on the master by a few turns. Then you'll probably have to readjust the height of your pedal. I also don't like a clutch engaging near the top of the pedal - that's just asking for slipping problems. IMO, it ought to start engaging within an inch or two of the bottom of the pedal, be fully engaged 3/4 of the way up, and have some free play on top so you know the master & slave are fully retracted.

Unfortunately , our 550's have a hydraulic release bearing type of slave of the type that Ferrari calls a "constant contact" bearing. In other words, there's a spring that holds the bearing's face in constant contact with the fingers of the pressure plate. So in theory there is no free play between the release bearing and the clutch. Where we can adjust for free play is between the pedal and the master. Since you Boxer owners apparently have a more conventional slave setup, you ought to be able to "tune" your master or slave actuator rod lengths to get the engage/disengage points where they should be.