A friend put a set of used, 7-year old FSA SL-K Light MegaExo tandem crankset out on Facebook’s Marketplace on Friday, January 17th that had been on their 2013 Calfee. I’d been thinking about doing a crank change on our own Calfee as a bit of an experiment and the used set of carbon cranks would only cost 25% of what a new set would set me back, once all was said and done. With that in mind, I went ahead and snapped them up for his asking price later that evening.
As to the experiment, our shifting woes with our own Calfee tandem have continued as I’ve not been able eliminate an annoying front derailleur (FD) cage and chain rub when we’re in the 53/11 or 53/13 gearing. While using the Shimano instructions for the ST-6703 eliminates the FD and chain rubbing, it comes with a 50/50 chance the chain will over-shift and drop on the crank arm. As to why this is, in addition to the usual Shimano over-engineering that makes pairing a FD designed for a 130mm axle on a 145mm rear axle problematic, our 13-year old daVinci cranks mounted on Phil Wood JIS bottom brackets seems to have a few millimeters of static big chain ring run-out. That run-out, when coupled with a bit of rear bottom bracket and/or frame deflection at the rear triangle under load, seems to be root cause of both the persistent chain rub as well as the over-shift. Therefore, my hope is the more robust MegaEXO bottom brackets and different cranks will eliminate the big chain ring run-out that is causing the chain rub as well as the over-shifts.
Since these cranks were originally fitted with a Gates CarbonDrive sync belt and pulleys, and because our daVinci cranks used 34t timing rings that bolted directly to spider-less crank arms at the axle flange, over the weekend I also ordered a pair of Stronglight CT2 130BCD 39T Ceramic Teflon chain rings and two chain ring bolt sets. Thankfully, I just happen to have a new set of FSA triple chain rings (52/39/30) and a set of triple chain ring bolts sitting around I could use with the cranks. While I could have used the 52/42/30 FSA chain rings that had been on our daVinci cranks, given the goal of this exercise I thought it better to use new chain rings. In fact, I’ll also be using new chains to eliminate that part of the equation and ordered those over the weekend as well.
In terms of unintended consequences, I don’t believe there should be any.
- Crank Arm Length: The FSA SL-K Light MegaExo tandem crankset will move me to a set of 172.5mm long crank arms, whereas the daVinci crank arms I’ve been using are 170mm. However, my captain’s FSA Gossamer MegaExo tandem cranks on our triplet are 172.5mm and I’ve never had any issues switching back and forth between the tandem and triplet with regard to crank arm length in the eight (8) years we’ve been riding the triplet. Debbie’s crank arm length remains unchanged at 170mm.
- Q-Factor: Interestingly enough, the Q-Factor on the FSA SL-K Light MegaExo tandem crankset is 158mm, which is nearly the same as it has been on our daVinci cranks paired with 108mm and 111mm front & rear bottom brackets. And, as noted, we have a set of FSA Gossamer MegaExo tandem cranks on the triplet so, once again, we’ve never had any Q-factor related issues switching back and forth between our Calfee and the Precision triplet.
- Bottom Bracket Design: The MegaEXO bottom brackets (BB) used on the FSA SL-K Light MegaExo tandem cranksets thread into a standard, old-school bottom bracket shell with English threading so we’re good to go there.
- MegaEXO BB Durability: While two of the bottom brackets that are coming with the cranks are the 7-year old ones our friends have put big miles on, there is also a new, never been used BB coming with the cranks. That one will go on the rear bottom bracket and the best of the two used ones will get rebuilt and installed on the front, noting I have all the parts I need for a rebuild on hand.
On Tuesday, January 21st I cleaned-up the 170mm daVinci front & rear cranks that just came off the Calfee as well as an extra pair of 175mm front cranks that I originally bought for the Calfee. I’ll hold onto those until after we’ve determined if the FSA cranks and MegaEXO bottom brackets do anything to alleviate our front shifting issues. It’s amazing how nicely the 12-year old daVinci cranks clean-up despite all of the wear and tear. The only crank arm that’s really showing any serious wear is the right rear crank due to the over-shift issue.
The FSA cranks arrived on Wednesday, January 22nd with the two used and one new FSA MegaEXO BB7000 bottom brackets and everything looked great. The “used” bottom brackets actually looked and felt like they’re in very good shape with smooth-rolling bearings. So, I’m not sure I’ll even bother with an overhaul, noting that can sometimes be trouble than it’s worth with MegaEXO bottom bracket rebuilds. Three new KMC X-10 10.93 chains also arrived on Wednesday, and the 39t Stronglight chain rings and two sets of chain ring bolts arrived on Thursday, the 23rd.
The afternoon of Friday the 24th — after spending a few hours at a friend’s house installing a set of heated grips on one of their Harley-Davidson’s — I began the crank installation project on the Calfee. I had the bottom brackets and cranks installed in short order and had the three KMC X10 10.93 chains drying after removing the factory lubricant with a solvent bath, citric degreaser rinse and final cold water rinse. However, I decided to hold off on the chain installation until the weekend as we had dinner plans.
After a 5-mile hike and lunch afterwards with friends on Saturday morning, the 25th, I spent the latter part of the afternoon getting the drive chain right-sized and combining the other two 116 links to come up with a 158-link sync chain and then began work to dial-in the front derailleur shifting. It was interesting that the FSA spacer installation notes didn’t yield a workable solution for our tandem. I opted to call it a day once I started getting a bit frustrated so as not to create more problems while searching for a solution,
First up on my to-do list on Monday, the 27th, after reading the Wall Street Journal, was to finish sorting out the shifting issues on the tandem. Again, I’m not sure why I’ve been having so much trouble with the front shifting. Even getting the new cranks positioned so the derailleur would consistently shift the chain between all three chain rings required setting aside the instruction and resorting to trial and error. However, I was finally able to get smooth and predictable shifting across the full range of gear combinations by placing the two 2.5mm crank arm spacers and wavy washers on the left sides of the front & rear crank yielding nearly perfect shifting… in the work stand. All that was left to do is to remove the chains, clean them one more time before immersing them in a hot melt paraffin and petrolatum bath — still my preferred chain lubrication method — before re-installing them on the tandem. We had to hold out for better weather before we could see if it would shift as well when under power.
That 1st test ride finally came on Sunday, February 2nd. It was a beautiful day and after warming up into the high 50’s and low 60’s around noon time Debbie and I headed out on the tandem for the first time in three full weeks. We took full advantage of the day by riding our 25-mile loop, despite not a lot of riding under our belts, and it felt wonderful. Best of all, the new-to-us FSA cranks, new chain rings and chains delivered flawless shifting: no over-shifts and no chain rub even in the 53/11 gearing. In fact, I can’t recall when the front shifting on our Calfee tandem has performed as well, so I’m very happy with the results of my little experiment.
Just to be sure it wasn’t a fluke, we took advantage of beautiful and warm mid-60ºF temperatures on Monday, February 3rd, and headed out at 10:30am for a second 25-mile ride. Once again, flawless shifting! Now, to be fair, we’re still getting used to the “new look” and I”m thinking it may be time to update the graphics on our frame, something our friend Craig Calfee offered to do back in September 2018 when the frame was back at La Selva Beach for a little touch-up work. Perhaps I can secure a set of the new decals and do the update here at home.