Hondo6

I recently found a rider-quality SunTour XCM triple drive side crank I plan to use for a future build. It's 110/74mm BCD. Here's a photo:



From the logo, based on SunTour catalogs available at the Disraeli Gears website it appears to be a 1991 model.

I'm pretty sure this crank was used in both double and triple configurations. Unfortunately, so far I've been unable to find spindle length info for this crank for either double or triple chainring configs. The last SunTour catalog I've been able to find that gave spindle length info was from the mid-1980s (also on the Disraeli Gears site).

From that mid-1980s reference, I'd guess 117mm for double and 125mm for triple configs. But I really don't know.

Can any of our SunTour experts either (1) point me at a definitive source that would tell me those spindle lengths, or (2) tell me from personal experience what length works, preferably for both 2x and 3x? The 2x info is more critical, as I'll likely be setting it up that way initially.

Thanks in advance for any advice.

TugaDude

This might be a shot in the dark, but here is Sheldon Brown's page which shows various makers cranks and their respective BB sizes.

What I'm thinking is perhaps you might be able to compare the Suntour crank to a similar Shimano and start there.

In any case, it seems for the triples, except for one that I noticed, the length doesn't exceed 122.5mm, so based on that, you might consider that the top end. And your estimate of 117mm might be good, but it might be a tad high.

Hopefully someone has more/better info to help you. Good luck!

P.S. I tried velobase.com with little luck. Here is the appropriate page. The page on the crank itself was of no help on spindle length.
https://velobase.com/ListComponents....7-e8e9d9083a63

seypat

Later catalogs on Velobase.

https://velobase.com/Resource_Tools/CatalogScans.aspx

Hondo6

Thanks. I actually checked both of those sources before finding the mid-1980s SunTour catalog with earlier SunTour BB spindle length info on Disraeli.

Unfortunately, neither those nor the 1990 and 1991 SunTour catalogs at Disraeli had the info I needed. Sheldon Brown's bottom bracket database doesn' t list the XCM crank at all. As you noted, the Velobase link for the crank doesn't have the spindle length required for either the XCM 2x or 3x config.

The info in the mid-1980s SunTour catalog may or may not be applicable, since the XCM triple crank seems to date from around 1990. The later catalogs do specify the SunTour BB model for the XCM, and it isn't the same one; it may or may not have used the same spindle length. Plus, the XCM is from after SunTour released Accushift; their mid-1980s catalog listing spindle lengths is pre-Accushift. That might be a factor too; dunno.

Again, thanks. I do hope someone out there has/can point me at the info I'm looking for. I realy don't want to go the "trial and error" route if I don't have to.

hazetguy 

From a Suntour '90 Model Bicycle Components Features & Specifications catalog:

hazetguy 

From a 1991 Suntour Product Line catalog.
Note that it is mentioned that the 1991 crank has been "revised" and the pic for 1991 shows the same markings as on your crank arm.
There appear to be a couple different bottom brackets available for 1991, one English, one Italian thread. No axle length is given, but the markings are.

machinist42

Not a "Suntour Expert" but shouldn't really matter as that's a Sakae (SR) crank. Not a Sakae Expert either, so there is that...

1990 Schwinn Voyageur picked up this past spring had a Sakae XCE crank, with a absolutely useless BB. BB spindle had posts like the ones for the XCE and XCM in hazelnutguy's reply here:

Measuring excluding the bolt post things yielded 125 mm and so used a 127mm BB-UN55 had laying around. Chainline's perfect for the triple. Have no experience with a double.

From hazyguy's data sheet, the XCM is takes a BB spindle 2mm or so shorter then the XCE, so perhaps you can extrapolate to like 122.5 for the triple and 115 for the double?

Good luck!

Hondo6

I owe you one, @hazetguy. N-3T is a standard 68mm BB spindle, and I have the docs to decode that re: length.

Many thanks.

Hondo6

Thanks. The N-3T spindle hazetguy's doc references is 126mm in length, per the Indian Standards Organization document Sheldon Brown references somewhere on his website (it's in PDF, and I have a copy stored locally). I think I've located a source for one of those and have it bookmarked.

machinist42

Jon's source notwithstanding, the actual spindle stock with the XCE triple crank on the 1990 Voyageur was a 3S.

Likely doesn't make a lick of difference?

Hondo6

Maybe not. His second doc says that the chainline tolerance is +/- 1.5mm - and the 3S and 3T only differ by 1.5mm.

But the difference in length for those two spindles is all on the drive side (39mm flange to taper end for the 3T drive side vice 37.5mm for the 3S drive side), so that puts things at the edge of tolerance. I think I'll go with the 3T, since that's what's specified in his 1991 doc and that appears to be the model of the XCM drive side crankarm I have.

TugaDude

Let us know how it works out and good luck!

zukahn1 

The similar cranks I have worked on from that era run 125 or so effective spindle length I believe they spec 125.5 as the charts show. If you running the standard size small chain ring a modern sealed 125 should clear everything and give you a fairly good chain and tread line. If needed you can add 1-2 mm spacing to either side of the BB to adjust some.

52telecaster

Great advice here already but I'll give you my down and dirty way to do this with any square taper. I assemble the drive side and take it to my favorite bike shop where they have the 4 popular sizes of Shimano. I hand press it on each bb to see which looks like it wouldn't interfere when tightened. It usually gets me plenty close and the Shimano bbs work well. This doesn't help when you have esoteric stuff but it will get you a working setup for cheap.