Rear D touching spokes Tink tink tink tink

[redir]

Because this is only happening on one wheel of several that I have tried I think it rules out a bent RD hanger. The bike is a C'dale Synapse with a Powertap G-3 Hub and a 11-32 cassette.

The RD hanger is brand new, it's the kind that bolts on. By eye it looks straight and again this is the only wheel doing it. I've set the stop so that the chain barely gets on to the lowest cog. It only does it while under stress, so like a really steep hill. Once the hill levels out it goes away.

This led me to believe that dish or spoke tension had something to do with it so I gave each drive side spoke a half turn and trued it up. Still does it. My other PT G-3 wheel does not do it though that cassette is a 11-28 I think. I do not have a spoke tension meter but the other G3 wheel definitely has a higher pitch when plucking the spokes, audibly, and the spokes are actually longer on that wheel.

I cannot fit a spacer with the 11-speed cassette. Unless they make a thinner one then the one I have which is pretty thin.

When it's in the stand of course it doesn't do it but eyeballing it the RD looks to be at least 3-5mm away from any spokes so I'm not sure what is going on.

[Dude]

if you can't fit a spacer in there...
- make sure the low limit screw is set properly.
- you can't fit any spacer in there?
- ensure rear der is aligned with cassette properly - this is a function of the der itself might actually be bent and/or the brand new der hanger coulc still be bent and/or the dropout might be bent.
- ensure b screw is set properly

[oldguy00]

So in the work stand, when in the easiest gear, the cage is 3-5mm away from the spokes?
Are you sure the sound you hear when riding is the cage hitting the spokes? Is the cassette on tight, no play?

[David Kirk]

The location of the drive-side spokes laterally is not in any way standardized. The freehub part, and its lateral location, are much more standardized but the driveside flange on the hub can be anywhere the maker wants it to be.

Add to that spoke lacing patterns change the spoke's location in space and it can be very hard to tell what the hell is going on.

As a rule it's best to make sure that the derailleur hanger is indeed straight. The fact that you get contact with one wheel and not another doesn't not rule out the bent hanger issue.

If in the end your hanger is straight, and the derailleur properly adjusted, and it hits one wheel and not another then I'd say that the wheel that hits is simply incompatible with the rest of your set up.

If this is the case that sucks but you'd be far from the first one to find one part works and another doesn't.

I'd check that hanger.

dave

[CampyGrampy]

There may be interference between the cassette and the spokes. Powertaps have unusual hub geometry. I have had this issue with a G3. It was carrying the cassette when it should have been coasting. Turned out the issue was very occasional rub between the inner cog and where the spokes crossed. The fix was a changing to a cassette with a smaller inside cog. You might want to pull the cassette and check for any abrasions where the spokes cross nearest the flange.

[Alistair]

Swap cassettes - does the noise move with cassette?

Swap FH body - does the noise move with FH?

All else fails, time to N+1 your stable.

[November Dave]

11-32 cassette should have more clearance than an 11-28 cassette, so out of the gate this is funky.

If the wheel with the 11-28 cassette has a significantly deeper rim, that would increase the clearance as well as making it a stiffer wheel all else being equal.

As David Kirk suggests, different spoke patterns could affect this but with 3-5mm clearance by eye in the stand that should be plenty. PTap hubs drive from the ND side so this is one of the rare hubs that could be laced radially on the drive side - that's not what's happening with the wheel with the 11-28 cassette, is it?

I'd stop adding spoke tension without a good measurement. One wheel could be laced with thinner spokes than the other which would yield a different tone. If the 11-28 wheel has a deeper rim, the shorter spokes would make a higher tone. Etc.

If the wheel is moving around that much, you'd probably be seeing other funky things.

If it's a 10 speed cassette on an 11 speed freehub, you need that 1.85mm spacer between the cassette and hub, and the 11t is barely hanging on the freehub until the lock ring is tightened. If it's an Ultegra hub, they used another spacer behind but time is making memories of that hazy.

Assuming these are QR wheels, are you using different QRs with each? A crappy QR could let things move and cause weird things.

[Mark McM]

As above, just because the derailleur only contacts with one wheel and another does not rule out a bent hanger. Hangers, especially replaceable ones held on with small screws, are remarkably easy to bend.

When you say the derailleur only contacts under stress, as when climbing a steep hill, does that mean it does it primarily when standing and stomping on the pedals? If so, I'd bet it rubs when stomping on the right pedal, but not when stomping on the left pedal. When standing, we typically lean the bike away from the pedal we are stomping on. This imparts a lateral load on the wheel, and the wheel may flex laterally. When we lean the bike to the left and stomp on the right pedal, the wheel may flex to the right (toward the derailleur), and when we lean the bike the right and stomp on the left pedal, the wheel may flex to the left (away from the derailleur).

Wheel flex is determined by component material and geometry, so there isn't much to do there. But if there is free-play in the bearings, it may increase deflection under lateral load, so you'll probably want to check for play in the bearings as well.

If, after checking all other things (hanger alignment, limit screw adjustment, indexing adjustment, bearing adjustment, etc.) the derailleur still contacts that spokes, then it might just be a wheels/drivetrain incompatibility - but all is not yet lost. You may be able to get more derailleur clearance by using a larger cassette. The drive side spokes angle inward from the hub flange to the rim. So the further away from the hub (larger radius), the further the derailleur will be from the spokes. With a larger cassette, the derailleur cage will be sitting further from away from the hub, and will have more spoke clearance.

[Tickdoc]

Last time I had this it was just a loose derailleur. I'll assume you've already checked that, but worth a check at least.

[dgauthier]

Originally Posted by redir

(...) This led me to believe that dish or spoke tension had something to do with it so I gave each drive side spoke a half turn and trued it up.(...)

Have you confirmed the wheel is perfectly dished by measuring it?

[CNY rider]

Originally Posted by November Dave

11-32 cassette should have more clearance than an 11-28 cassette, so out of the gate this is funky.
.

This is non-intuitive, at least for me.
Could you explain why?
Thanks.

[AngryScientist]

Originally Posted by CNY rider

This is non-intuitive, at least for me.
Could you explain why?
Thanks.

The further you get away from the centerline of the hub, tangentially, the further the spokes should be from the largest cog. Spokes angle in toward the rim, so a 32 cog, which has a larger diameter than a 28 should have the RD "lower" and closer to the rim than on a 28, which should decrease the chances of spoke contact.

man, what a ramble. does that make any sense?

[CNY rider]

Originally Posted by AngryScientist

The further you get away from the centerline of the hub, tangentially, the further the spokes should be from the largest cog. Spokes angle in toward the rim, so a 32 cog, which has a larger diameter than a 28 should have the RD "lower" and closer to the rim than on a 28, which should decrease the chances of spoke contact.

man, what a ramble. does that make any sense?

In fact it does, thank you.
I did not think about how the position of the RD changed with the larger cog.

[redir]

Looks like I have a lot of work to do tonight. Thanks for all the valuable info. I would have thought the opposite of a larger cassette too, intuitively. I think the 32 is the biggest one I have.

I forgot to mention it's the G3 laced to a Zipp 303. The other G3 hub I have is laced to an Open Pro.

Good suggestion looking for scratch marks. Yes it only does it under stress. I don't necessarily need to stand on the pedal but just sit and spin hard. I'll have to see on my morning commute tomorrow if it's the drive side pedal only.

[redir]

Is there a way to accurately measure a hangar to see if it's bent without special tools?