T47 NDS spacer?

[Nomadmax]

I just installed a Campy Chorus 12 speed crankset (170mm) on my Litespeed Arenberg (T47 BB, Campagnolo UT T47 cups). It replaced a 172.5mm crankset, same make and model. After double and triple checking everything, the NDS crankarm is only clearing the NDS chainstay by one MAYBE two millimeters. I re-installed the 172.5s that had been on the bike and they have nearly double the clearance. Wave washer is in place and I even tried two of them with no change in clearance. With the NDS pedal 3 oclock position, I can push the crankarm until it touches the chainstay.

The question is, are there NDS spacers out there for T47 threaded BBs and is that the proper fix?

[Nomadmax]

I found these and ordered a couple. I'll start with one and see where that gets me.

https://www.whiteind.com/product/bot...t-cup-spacers/

[prototoast]

How much lateral play do you have when the crank is in there? Because Campagnolo uses a hirth joint, if you add a spacer that prevents the left and right halves of the spindle from fully interlocking, you could be creating a real problem. Other brand cranks are more forgiving to adding spacers to shift the cranks right/left.

[Mark McM]

The lateral position of an Ultra Torque crankset is determined when the right (Drive Side) bearing is locked into the right cup with the spring clip. Nothing you can do on the left (Non Drive Side) is going to shift the cranks laterally, either left or right.

Since there's no such thing as a negative spacer to add to the rightcup, then the only way to get it to work is to modify the frame. For example, you could either shave down the right end of the BB shell (shifting the right cup to the left), or crimp the left chainstay for more crank arm clearance.

[avalonracing]

Whatever the case, I sure as hell wouldn't ride it with that little clearance.

[Nomadmax]

I'm not crimping a new titanium frame or facing the BB to less than the 68mm it is.

As far as the hirth joint, Campy UT cranks work on 68mm and 70mm shells without the loss of engagement. I'm thinking there's some wiggle room in there, 2mm anyway.

[Mark McM]

Originally Posted by Nomadmax

I'm not crimping a new titanium frame or facing the BB to less than the 68mm it is.

As far as the hirth joint, Campy UT cranks work on 68mm and 70mm shells without the loss of engagement. I'm thinking there's some wiggle room in there, 2mm anyway.

There is no play or wiggle room in the Hirth joint. The bolt locks the axle halves together solidly, to the same total axle width, regardless of what cups are used. There is a little bit of tolerance allowed for variations in shell width, but the crank is still positively positioned by the right side spring clip, so the crank lateral position will be determined by the position of the right cup.

The difference in lateral positioning between 68mm (BS) and 70mm (ITA) shells is built into the cups. If you don't want to shave down BB shell, then you could consider shaving down the right cup (if there's enough material in the cup to do so).

The Ultra Torque system has little adjustability, and none at all as far as shifting the cranks to the left. If you don't want to modify (cut) the frame or cups to get it to fit, then you'll have to find a different type of crank.

[mjf]

No additional solution here, but it's really odd that the 172.5 have plenty of clearance, and the 170 don't.

Campy only provides a schematic for the 180mm version, but it has me wondering if and how different the spec between sizes is outside of length. Between measure for crank arms especially, which campy has @ 114.5mm for the 180mm version.

https://www.campagnolo.com/on/demand...3_2021_ENG.pdf

[mattscq]

Curious: do both cranksets have the same q-factor if one is ending up with less clearance? is the entire thing just shifted over?

[KonaSS]

Something seems odd here, with both cranks being the same make and model.

Have you pulled both cranks and just connected the left/right arm outside the frame just to do some basic measurements/comparisons?

[Xrslug]

Have you tried installing the old Chorus crank, verifying clearance is good, then removing only the NDS arm and installing the new NDS arm? If you still have no clearance with the new NDS arm in that scenario, it would at least seem to locate the issue with new NDS arm and not any installation issues with the new crankset as a whole.

If you are certain installation is the same between the two otherwise identical cranks, then there may be something off with the new NDS anrm itself if there is that much variance in clearance between new and old. Ideally you would try a third Chorus NDS crank arm of identical length. Assuming you can’t get your hands on a third NDS arm, if you put the new NDS arm on top of the old, can you visually verify a difference at the tips of the cranks? You might also try marking the BB interface and pedal spindle interface of the old crank on a piece of paper and setting the new arm on that to see if the variance is in the new arm itself.

[Nomadmax]

I'm going to do the things mentioned above (thanks btw) and see where that gets me. If all that doesn't work out, I'll re-install the 172.5s and start looking at other cranksets.

I've grown to like the 32/48 so I may look at the Shimano GRX 12 speed double in 31/48. I have a Lynskey with the 11 speed version and like it a lot. I'd need a set of T47 BB cups and a GRX FD as well. If I decide to go that route, I'll need to figure out if the GRX has a wider Q factor and if the otherwise Campagnolo Chorus 12 drivetrain, specifically the shifters and RD will work with a setup like that.

What I'd really like to to find that I made a mistake and it works perfectly

EDIT TO ADD

I just finished doing all the install/re-install swaps using the 172.5s, 170s and every combination, including one size on one side, one size on the other. No joy. I will correct myself in that I said the 172.5s had twice the chainstay clearance, not so, it's more like a millimeter more. So, given that, I'm running the 170s as is and will see what happens. I guess I never really saw how close the 172.5s were to the NDS chainstay. They didn't hit before, so maybe that'll be the case with the 170s. One thing is for sure, I'm done messing with it until something bad happens. All in all, I'd say the Q factor of Campagnolo 12 speed cranks is a touch too narrow for the Litespeed Arenberg (disc) with it's straight chainstays.

[Mark McM]

Originally Posted by Nomadmax

I've grown to like the 32/48 so I may look at the Shimano GRX 12 speed double in 31/48. I have a Lynskey with the 11 speed version and like it a lot. I'd need a set of T47 BB cups and a GRX FD as well. If I decide to go that route, I'll need to figure out if the GRX has a wider Q factor and if the otherwise Campagnolo Chorus 12 drivetrain, specifically the shifters and RD will work with a setup like that.

This part is easier: Yes, Shimano 12spd GRX cranks have a wider chainline and Q-factor than Campagnolo Chorus 12spd cranks. Specifically, the GRX cranks have a chainline of 47mm and a Q-factor of 151mm, whereas the Chorus cranks have a chaline of 45mm and a Q-factor of 145.5mm.

Campagnolo cranks have a narrower Q-factor than most other road cranks, and that is likely causing part of the clearance issue. If the 172.mm have more clearance than the 170mm cranks, then there is likely a manufacturing variance between the two cranksets - but is the 170mm crankset narrower than spec., or is the 172.5mm crankset wider than spec.? You'll have to measure both cranksets to know for sure.

Others have likely gotten the GRX cranks to work with a Campagnolo drivetrain, but the chainline might not be optimal. These days there are plenty of other sub-compact options to consider.

[Nomadmax]

As always, thanks Mark and others.

The 170s are an experiment that may well lead to 165s. Maybe the 5mm shorter length will provide more clearance but I won't make the change for that. My cycling inseam is 815mm and I've been riding 172.5s since the 90s. This year, recovering from stage 3 NHL B cell, they suddenly feel too long, not sure why (my knees hurt a little with the same saddle height, 72cm center to top of saddle @ midpoint). My last chemo was 01-29-24 and it really did a number on me, nothing felt normal but it seems to be coming back, little by little.