I'm wanting to piece together a triple crankset for my commuter and only really use the middle and smallest chainrings, 42T and newly acquired Shimano 26T. Running a 6 speed chain, will use a 600ex friction FD.

I've dug up my Sugino GP130 and have the rings bolted on but the smallest is really close to the lip of the cranks that the middle kind of sits on, the chain won't even go on the smallest ring.

I take it I need some spacers or something?

EDIT: Just flipped the small around and gained a small amount, but still need spacers?

Yep, looks like you'll need a couple mm of chainring bolt spacers, no big deal. I highly recommend getting a different 42T that is thicker and has countersunk bolt holes, so that the bolt and ledge on the crank spider won't protrude so much. The one you have is for double cranks where neither of those things are a concern.

Hi I am a crank expert/ bike store owner for over 13 years. What you have going on is your mid chain ring is on backwards. The chain ring bolts need to recess into the chain ring, so the chain does not hang up on the lip of the bolts, also the little tab in the inside diameter of the mid ring is suppose to go under the crank arm. Do not listen to the other poster!

Nope, the middle-outer is a Shimano double chainring. Aside from the tab not being oriented to the crankarm, the chainring is bolted on correctly.

I think the problem is that the inner-granny chainring is designed for older Shimano forged cranks where there's a 5mm spacer under the chainring. With the GP130 crankarm, there's a bit of spacer built into the crankarm, but it's not 5mm. I think the original chainring may have been dished or there was a 2mm spacer under a flat ring. Don't worry- playing around with spacers is how we made things work in the old days.

Brian- I've been doing these sorts of conversions/adaptations/kitbashes for 35 years.

The reason that I stated the chain ring to be on backwards, is that in the late 80's Shimano figured that if they would put a flaring on the inside of the large and mid rings, so that when downshifting, the flaring would guide the chain and would have a lot less propensity to drop down between the chain rings (undesirable) and get wedged in place. There is no logic (that I know of) to have the flaring on the outside of the chain ring. I have never seen a stock crank with the faring on the outside, Because you are mixing brands, I am not ruling out the need for variation in the smallest chain ring spacing.

Yep, that's how my Deore LX triple with SG rings has the flaring/offsets. The confound is that the OP is using a 42T road ring, which was never designed to be used with a granny ring, so the offset is the other way around.

Huh. Learn something new every day. I apologize, Brian- you appear to be correct.

Well, the OP's 42T *is* mounted as it's supposed to be -- it's just not ideal for what he's trying to do. Here's a picture from Velobase showing SG road rings, installed correctly in their native habitat. You can see how the offset on the 42T is toward the frame:



And here's the backside of my Deore LX crank, showing the offset going the other way for a ring intended as a middle:



Does that help, or just muddy things? I think the OP [MENTION=321982]jgcycle[/MENTION] should look into a ring like this -- it would play much better with the granny: FSA Pro Road 9/10s 42t Middle 130mm Black Chainring

Or only $14 if a 39T would work for his purposes! https://www.universalcycles.com/shop...&category=2629

And I thought this was going to easy! Buy a ring or two, install the triple, put the 600 on the other bike...


So I'm running a 6 speed on this right now, will those chainrings that say 9 speed chain be ok with my fatter chain?


Thanks, you guys sure know a lot.

Yep, they'll be just fine. I'd use an "8-speed" chain like the SRAM PC-850.

Well, my excuse is that I was on vacation. I'm back now (back to work in the morning). So there. Nyah.