Triple Crank on S30? Help

[David Most]

I saw this discussed a bit on threads from a few years ago, but I was hoping for a bottom line easy answer. I have a Silvio v1 with a triple crank on a square taper bottom bracket (e.g., a Sugino xd600 with 152mm arms and 24/36/50 rings). Can I easily install a similar setup on an S30 (it was easy on the v1, no modifications needed)?

I don’t really use the big ring, if that matters, and I’d be okay with just the 24 and 36.

Thanks!
David

 

[Doug Burton]

Hi David,

The S30 uses a different bottom bracket arrangement. The S30 front chainstay assembly actually clamps around the external bearing shells of the required outboard bearing bottom bracket, where the Silvio V1.0 used the bottom bracket shell itself to secure the front chainstay. A square-taper bottom bracket won't work on the S30.

That being said, you can use a triple chainring system on an S30 (or at least I did on my Silvio 2.0, which is the S30's progenitor.) Your inner chainring will need to be able to clear the chainstay clamps, so you'll need a 130mm-spider crankset. I used Ultegra cranks on mine, and had to remove the "tabs" that extend from the chainring bolt bosses on the smallest ring toward the bottom bracket axle (a chain-guarding scheme) but you may not need to do that. I also offset the chainstay laterally about 4mm by moving the clamps slightly to the non-drive side of the bottom bracket.

I will try to find some photographs; it's not as drastic or complex as it sounds.

 

[David Most]

Hi Doug. Thanks for the quick post! I have a collection of cranks that I use on my favorite recumbents, all of which have 152 or 155 arms and fit on square taper bottom brackets. I like (need!) the 24 tooth gearing (with a 36 in the rear) to make it up the hills that I ride near me, and I also like the short crank arms. It’s helpful to know that I can’t use these at all with the S30. Is that the case with the S40 too? In any case, the modifications/requirements that you describe jive with what I read in the earlier threads. I guess I’m wondering, with a 130mm spider crankset, what’s the smallest granny gear that can be installed? And, then there’s my desire for the short crank arms…

 

[benphyr]

I just installed a square taper Camagnolo bottom bracket and triple crankset on a 2019 s40. And it spins great with about 2-3 mm clearance to those tabs that @Doug Burton is talking about with the pictured 30/42/52 so you will likely need to trim them from your 24 tooth granny chainring if yours have those tabs.

I think the change from clamps on the bearing shell to the bottom bracket shell itself came with the change from s30 to s40 so that makes things simpler for the s40.

 

[super slim]

http://bikesmithdesign.com/Short_Cranks/gossamer.html
If you can buy a second hand FSA Gossamer Mega Expo triple 130/74 PCD 172.5 or 175 mm crankset with external bearings, BikeSmith can shorten the cranks to 152 mm for $85!
This is what I have on my Silvio V1 with chainstay clamp to the BB, and my Silvio V2.1 with chainstay clamp to the BB External bearings.
The V2.1 required some filing of the BB bearing clamp brackets, and inside edge of the 24T chainring, so I could keep the middle chainring in line with the 4th rear sprocket.

 

[bladderhead]

Anybody who uses a triple crank needs help.

 

[chicorider]

You could also contact CB for a replacement chainstay that will give you the current BB clamp. I went that route on my S30 because I use their short chainstay. They won't give you one for free, but it will take care of the clamp-BB interface issue.

Or...hmmm...I still have the medium length chainstay that came with my S40, which I recently sold with a short chainstay. I've held on to this medium for just-in-case reasons, but at 5'4" I know I'll never use it. If I ever sell my V20, it'll have to go to a shorter person because I cut the steerer tube all the way down, and I had to cut the boom tube to fit with the curved slider. The current short chainstay will have to stay with it. And if I ever sell my S30, I can sell it with the original medium chainstay.

Sorry about all that "thinking out loud," but if you are in the continental U.S., use the medium size chainstay, and want to do a little haggling over this one, PM me.

 

[David Most]

Thank you, all, for this helpful information. I’m getting acquainted with a new (to me) S30, and it’s fun learning. I’m interested in the option that Craig referenced (going with the newer version of the chainstay that clamps to the shell), but I’d need a set of clamps, which are currently out of stock.

Meanwhile, as I look at parts in my garage, I’m wondering what sorts of bottom brackets will work with the S30 chainstay. Specifically, how large must the diameter of the bearings be in order to work with the S30 chainstay clamps? I have a Shimano bottom bracket that I could use, but the diameter of the bearings appears to be a bit smaller than that associated with the FSA bottom bracket that came with the bike (along with the FSA Omega crank). I have a memory of reading a thread that said something about some Shimano bottom brackets not working (something along the lines of needing 44 mm vs 40 mm diameter, but I may be off), though I hope that I’m wrong. I haven’t had any luck trying to search for information about bottom brackets that will work with the S30 clamp, and I’m hoping that y’all can help. Thanks again!

David