JSNYC

Am running XT hubs w/135mm spacing, a 68mm bb shell, and an FSA Gossamer tandem-specific crank (triple) & bb combo. FSA instructions/matrix seem to show that combo should be a 48mm chainline. Does that sound right?

I'm ultimately trying to figure out how many spacers to use on drive & non-drive side front and rear cranks before I tighten everything down. On the cups, i used 1 spacer on each side (manual said that's the spec for 68mm bb shell). For the front crank, the manual indicates (assuming 48mm chainline) 2 2.5mm spacers on the L side (which for front crank, is same side as rear drive side--which to me is VERY confusing; i figured drive side is the R side always, but I guess not in tandem-land).

For the life of me though, I can't get the L side crankarm flush with the BB cup. I am wrenching on the self-extracting bolt HARD and I've hit the proverbial brick wall. Am afraid to torque any more. Are these FSA cranks just really, really hard to install?

From the pic, you san see there's about 2mm +/- to go in order to be flush with the bb spacers.



Thanks for any tips & tricks.

PMK

I am not 100% positive on this. I have spoken directly with their tech support about theses cranks. The versions that we own, but have sitting in a box, I thought had a wave washer that applies bearing preload and minimizes the side float / play of the BB shaft.

Note #7 in this tech pub

https://www.fullspeedahead.com/storag...rankset_v3.pdf

I can see the wave washer is installed in your photo, outside of that wave washer preload, the crank arm should not make contact with the bearing.

The FSA tech support also informed me that I should install the crank arm with, if I recall correctly, Green Loctite. This is to keep the crank arm from loosening, working, and falling off. Do not put green Loctite on the bolt or threads.

FWIW, ALL my experience with Green Loctite (609 series), has required serious heat, typically from a propane torch, to release the Loctite bond.

Again, we do not run these cranks, have them stored in a box, and I am recalling this without looking directly at the cranks.

The bolt you are tightening is there solely for crank retention, it is supposed to bottom out, or somehow fully seat everything. It has a fairly high torque spec and will probably require a socket type allen wrench to get anywhere close to what they post for a torque spec. The wave washer is what serves as your adjustment / bearing and shaft side play removal device. There should be a small gap to allow the wave washer to function and know you have not taken the side clearance below zero.

Based on your photo, I believe it is proper. All the best with it.

PK

JSNYC

Thanks a bunch. I used to have Dura Ace 7700 and the cranks had the same self-extracting bolt design, so I'm familiar with the concept (proper seating, etc). The only difference with 7700 was there wasn't as large a gap like what's on the FSA, so I wasn't sure if what I have here is right (or not).

In terms of spacers, I have: 1) 1 2.5mm BB cup spacer on each BB cup (on the inside, i.e., adjacent to the threads), 2) no crank spacer on the left side (my left leg side) and 2 crank spacers plus the wave washer on the right side (my right leg side).

I can't imagine that wave washer being sufficient to apply preload, but maybe the gap that is there is enough that it compresses and the right force is applied. Who knows...

What really threw me off is the FSA directions for the front crank I think are wrong: the instructions said the "L" cup for the front BB was to be installed on the right leg side of the frame. That "L" cup is about 2-3mm longer (wider) and I don't understand why that extra distance is needed on that right side, since I would think the point of the extra material is to "push" a chainring out further as needed, i.e., get the chainline to spec. Since on the front crank a chainring is on the left side (my left leg side), that would make sense.

Reason I say the instructions may be wrong for the front crank install is their instructions for the rear crank are just the opposite: their "R" cup says it goes on the right leg side. Am I right or is FSA right? Put another way, I always thought "R" and "L" meant right leg side and left leg side, respectively. Do FSA instruction manual writers operate in a parallel universe?

The green goop you see is Phil Wood grease squeezed out from the crank spindle/interface. I figured better to do that initially in case I have to take it apart rather than put loctite on (which, to be honest, I've never been a fan of or had need to use on any of my road bikes).

JSNYC

Well I somewhat answered my own question and this may help someone with Gossamer cranks: I just got off the phone with FSA and indeed, their install instructions are wrong, they have it reversed L to R on the front crank install instructions. In other words, they say L bb cup when they mean R bb cup, and vice versa.

DubT

When I built our tandem I initially used FSA cranks and found their techs to be very helpful. The guy I talked to told me to wrap Teflon plumbers tape around the BB cups befor I installed them, I think this is a good idea, it should keep them from squeaking. I did the same thing when I installed the new Ultegra cranks.

Do you care to elaborate why the build has taken six months to get started?

Wayne

JSNYC

Agreed, the FSA tech I spoke with was very helpful and knowledgeable. Made for a very productive discussion.

Teflon tape--I've heard the same. Everyone's got a different take on squeak-b-gone methods, and I'm in the camp of prodigious amounts of Phil Wood grease--it's what I've used for years on various materials, so I'll stick with that.

As for build delay, well.....it's been almost a year and a half! Time flies. Life threw a few curves and the bike took a back seat. I stopped riding for at least a year or so (medical issue), and then we moved and had a ton of logistics/construction to deal with, so poof there went another 6 months.

I'm (and "we") are excited to get back on the Aliante saddles again!

woodrow5

So JSNYC,

How many crank spacer should be put on each side of captain's crankset and stoker's crankset?

PMK

Not JSNYC, FWIW, if you go to the link I posted, they seem to spell it out and it varies depending upon the build.

PK

JSNYC

Based on the manual and per my axle and BB shell width (and commensurate chainline), the setup is:
1) On the front: one BB spacer on each side of the BB cups, one crank spacer and one wave washer on each side of the crank.
2) On the back: one BB spacer on the right BB cup, no BB spacer on the left BB cup, one crank spacer and one wave washer on each side of the crank.

The reason for no left BB cup spacer is if I had torqued everything down to spec, the wave washer would have been crushed flat and the BB bearing preload so high it wouldn't spin freely. In effect, there was about 2mm too much spacer somewhere in that mix, so I backed off before getting to that point.

I picked the left side BB cup to remove, guessing/assuming that it was better to have the driveside "pushed" out 2mm (rather than remove a right side BB cup spacer and have the inner triple chainring "pulled" 2mm closer to the chainstay, which would have been really snug and might cause chain rub), and that the wave washer needs to be adjacent to a spacer on both sides.

Once the chains are on there I assume I'll be able to see the effect of all of this, and make adjustments where necessary.

Lotta moving parts on assembling a tandem, that's for sure (I've never done this before, obviously!).

woodrow5

By the way, which brand and model of front derailleur are you using with FSA crankset?

JSNYC

Ultegra 6700 triple. Anything I should make note of?