Recently I've been noticing some "rattles" or "clunkiness" in my front end, mainly over rough pavement.  It's not a huge deal, but I'd like to make it go away.

I figured it might be the head bearings, so I got the special tool, followed the procedure and torqued the adjuster nut to 30Nm.  The nut ended up in about the same location and the front end felt no different afterwards.

Today I had the front wheel off with a pitbull under-triple stand.  I can feel and hear a slight clunk in each fork tube if I grab/shake the caliper bracket.  I presume that this is the result of fork bushing clearance, and I also suspect that this is what I've been feeling.  How much  fork bushing play is normal?  Is there a standard way to test or measure it?  The wheel will be off for a few more days and I'm interested in doing additional tests on the forks.

The bike is an '07 M695 with ~10k miles.  It comes from the factory with the non-adjustable Marzocchi forks (same as S2R800), but early on I upgraded the forks with Matris internals that have preload, rebound and compression.  I've been into them multiple times to fine-tune spacers/oil level/viscosity, so I'm confident that the internals are good.  No leakage whatsoever.

BK

AFIAK, there is no definitive test for bushings on an assembled fork and 10K miles would certainly be premature wear.  '07 bike with an internal fork problem?  Warranty!

Quote from: howie on October 12, 2008, 09:14:53 PM
AFIAK, there is no definitive test for bushings on an assembled fork and 10K miles would certainly be premature wear.  '07 bike with an internal fork problem?  Warranty!

I doubt the new bike warranty would apply here since 1.5yrs ago I replaced all the internals with aftermarket components (spring, cartridge, cap, oil, etc.).  I could look into it, but I'll bet it's a real long shot, especially because the "clunkiness" is not super obvious.

I'm mainly interested in learning about bushing wear characteristics to see if I'm on the right track.  It's not leaking fluid and the stiction was good last time I measured it.  I wonder if the lower viscosity fork oil I'm now using exaggerates the feel of the slop.

BK

whats the warranty on the parts that were installed?

Quote from: BK_856er on October 12, 2008, 10:29:33 PM
I doubt the new bike warranty would apply here since 1.5yrs ago I replaced all the internals with aftermarket components (spring, cartridge, cap, oil, etc.).  I could look into it, but I'll bet it's a real long shot, especially because the "clunkiness" is not super obvious.

I'm mainly interested in learning about bushing wear characteristics to see if I'm on the right track.  It's not leaking fluid and the stiction was good last time I measured it.  I wonder if the lower viscosity fork oil I'm now using exaggerates the feel of the slop.

BK

Obviously, Ducati will not honor aftermarket parts and work.  The warranty repair would probably be new stock forks anyway.  Did you do the work or was the work done for you? 

Quote from: howie on October 13, 2008, 05:59:11 AM
Obviously, Ducati will not honor aftermarket parts and work.  The warranty repair would probably be new stock forks anyway.  Did you do the work or was the work done for you? 

I did the work myself.  I realize that Ducati will not warranty aftermarket parts, but even though the bushings are OE virtually everything else in there is not, so they would have a strong argument to deny the claim.  I could put all the old parts back in, but that's a fair amount of work on my part and maybe the bushings are fine after all.  I'd rather not focus on the warranty thing.  I want to understand the role of the bushings, how they wear and how to evaluate them.  My only other point of reference is a set of Ohlins R&T forks with 25mm internals on my track bike....not really a fair comparison in relation to the Marzocchi fork.  I'm going to try and rig up a dial indicator to measure the movement of the fork leg.  Looks to be 1-2mm or so deflection at the bottom of the fork leg with an associated audible clunk.  Sound excessive for a Marzocchi?

BK

I looked in the shop manual.  All they say about the bushings is (paraphrased) if you you dissassemble the forks, replace the bushings.  No spec.  Off hand, I don't think bushings are your problem.  I suppose you could try and talk to the manufacturer of the parts.

Quote from: howie on October 13, 2008, 02:03:42 PM
I looked in the shop manual.  All they say about the bushings is (paraphrased) if you you dissassemble the forks, replace the bushings.  No spec.  Off hand, I don't think bushings are your problem.  I suppose you could try and talk to the manufacturer of the parts.

Will do.  I appreciate the trouble you took to dig up the info!

I'll update when I learn more.

BK

Quote from: BK_856er on October 13, 2008, 09:08:51 AM
--------------SNIP---------------
  I'm going to try and rig up a dial indicator to measure the movement of the fork leg.  Looks to be 1-2mm or so deflection at the bottom of the fork leg with an associated audible clunk.  Sound excessive for a Marzocchi?

BK

That sounds like a lot, for any fork.
Curious to hear what the dial indicator reads.

Quote from: Speeddog on October 13, 2008, 05:59:52 PM
That sounds like a lot, for any fork.
Curious to hear what the dial indicator reads.

Tough to get a super accurate reading due to flexing of various components, but measured at axle level I got 0.040" (~1mm) total displacement forward and back.  Each side gave the same value.  Wheel off, front supported by under-triple stand, forks installed in the triples.  Dial indicator clamped in vice sitting on a "lab-jack" adjusted to a suitable height.  Support the fork tube with one hand and push/pull on the lower fork leg with the other hand to induce clunking.  Still sound like a lot?

BK

So the total distance moved was +/- .040", a total of .080"?
Yeah, that sounds like a lot.

I've got 3 sets of fork legs at the shop (all off of the bike), one set is S4Rt Showas with ~800 miles on 'em, the others are unknown mileage, IIRC one set is older 41mm Showas, not sure about the other set.

I'll try to rig something up with a dial indicator tomorrow.

Quote from: Speeddog on October 13, 2008, 09:49:37 PM
So the total distance moved was +/- .040", a total of .080"?
Yeah, that sounds like a lot.

I've got 3 sets of fork legs at the shop (all off of the bike), one set is S4Rt Showas with ~800 miles on 'em, the others are unknown mileage, IIRC one set is older 41mm Showas, not sure about the other set.

I'll try to rig something up with a dial indicator tomorrow.

Sorry if I was unclear, the total movement for both directions combined was 0.04" (not 0.080").

That'd be super cool if you could get a measurement.   

BK

The Italian manufacturer of my fork internals, Matris, failed to respond to multiple previous simple technical inquiries, so direct information is apparently a dead-end.  Morever, I gather that they are not currently represented in the USA.  Despite the support issues, they have some very nice products.  Anyway, Jason at D.O.S. (my suspension guru) has informed me that all forks will have a good amount of movement of the type that I'm seeing, even when new, and I should probably look elsewhere for the source of my rattle over rough pavement.  In particular he suggested that I look more carefully at the steering head bearings for any sign of play and also described his preferred technique to set the bearing preload.  Up until now I had only re-torqued them to spec and figured at my low mileage they should be intact and OK.  Tonight I bought a ladder to suspend the front end and PROPERLY checked for play in the steering head bearings....nada....seems nice and tight.  I'm going to button things up, enjoy the rest of riding season and do more investigation as a winter project.

In summary, fork bushing wear does not seem to be a common problem, at least on low-mileage forks, and some measured slop in the bushings with the wheel off is completely normal.   

BK

I was going over my work after final assembly and I think I may have located a potential source of my front end rattle.  Brake calipers.  My M695 has those shitty floating calipers and there is gobs of movement/noise if grab and shake them.  I'll need to test that theory with some on/off brake runs over a rough patch.  Applying the brake takes up most of the slop.

BK