Boxer flywheel studs

JRV: More problems with the new Boxer clutch!....studs may be too short!

While assemblying the clutch onto the flywheel, on the table, I noticed that the clutch frame sits off the flywheel by about 2 mm. Those at AP Racing tell me this is normal, and that it will go down to meet the flywheel when the bolts are torqued.

The problem is that there is little thread on the studs to engage, and possibly hold the clutch housing. The stud has a threaded portion on both ends, one being longer than the other. The long end is the end removed from the flywheel. The short end was the end holding the clutch.

Facts: Hole in flywheel depth = 13.9 mm
Stud lenght = 45.2 mm
Long threaded portion of stud = 15.5 mm
Short threaded portion of stud = 12 mm

AP Racing told me they have the stud stick out, from the flywheel 33 mm.

My solution: I can get this, and it should solve the problem, but I would have to inset the short end into the flywheel, not the long end, which was originally in it. With the long end in, the useable lenght becomes only 30 mm. With the short end in the useable lenght becomes 33 mm.

The short end lenght is 12 mm deep, but the flywheel frame depth is 13.9 mm deep....it may be short, but will it be adequate?

Your opinion?

I heard that studs do not have to Locktited down....true?

Hi Henryk,

First off let me say that on the Nut End (outer)you really only need full thread engagement + 1 thread sticking out. Less than full nut (thread) engagement would be risky.

Now, by reversing the studs if you get 12mm thread engagement this is actually plenty, as the general fastner rule of thumb is 100% of the cross section is minimum, and at 12mm you have 150% of the cross section (8mm) engaged.

I believe the reason they suggest no locktight is neccesary is because it's expected that the studs are bottomed and tightened very securely into the flywheel itself, and then the nut tightened with lock washer on the outer end with the PP applying constant pusing pressure against the studs insuring no amount of vibration could work them loose. It's common on PP studs to simply use lock washers as the PP then applies constant force insuring they can't come loose once properly tightened. In essence the studs are spring loaded.

So it sounds like you should reverse the studs to get the 33mm protrusion hieght, unless of course that leaves more than 1-2 threads sticking out of the nuts with lock washers. As to lock tight on the threads inserted into the flywheel, doesn't sound absolutely necc. as long as the studs are bottomed and tight, but also couldn't hurt, either way is fine.

Regards, JRV

I will then turn the studs around.....something for you to keep in mind when you do these.

FYI: Here is a picture of the nuts (bolts?) they sent with the new clutch. There are no washers.

The torque setting is 11 ft-lbs. This was comfirmed twice with AP Racing........I thought this was a little low.......they assured me it wasn't.

My next concern is whether the gap between the clutch casting and the flywheel will close with only 11 ft-lbs of torque. They told me that the clutch casting should be right against the flywheel. I initially thought of this as a "floating" design, but they assured me it wasn't.

I will then turn the studs around.....something for you to keep in mind when you do these.

FYI: Here is a picture of the nuts (bolts?) they sent with the new clutch. There are no washers.

The torque setting is 11 ft-lbs. This was comfirmed twice with AP Racing........I thought this was a little low.......they assured me it wasn't.

My next concern is whether the gap between the clutch casting and the flywheel will close with only 11 ft-lbs of torque. They told me that the clutch casting should be right against the flywheel. I initially thought of this as a "floating" design, but they assured me it wasn't.

I can't seem to delete that last redundant post.

Henryk,

Are those the nuts in the photo for the new style PP?

These appear to be self aligning nuts, interesting.

Also, the 11 ftlbs should be fine as PP's 'spring load as I mentioned.

Yes I'm sure the PP will draw down as they explained as this is normal to spring load and clamp the discs.

A note, if the PP doesn't draw down and spring load then you'll need to reverse the studs back the other way, as a failure to seat all the way down will mean the studs bottomed to soon.

Yes they are. Six of these are included with the new clutch.....as are 3 alignment pins (same as the old ones).

Here is a picture of the hole where the new bolts go into. Why no washers?

Reversing the studs, I do't think is an option. This will leave less than the 33 mm required.......unless I just screw in the long end 12 mm deep, without bottoming it out on the flywheel.....is this acceptible?

My other option would be to just extend the threads on the short end with a metric die.

I thought of this possible problem earlier. I will know by getting to 11 ft-lbs, and feeling if the nut bottoms before then.

OK Got It !

You don't reverse the studs, the 12mm lenght is supposed to go down giving the correct protrusion hieght. The special centering bolts need the long threaded end to pull the PP completely down. Neat!

They don'trequire lock washers because the PP keeps constant sring tension (load) on them. Cool Setup!

Can't wait to see and install this new design.

Regards, JRV

ps: how did the CO/HC testing go on your TR?