Bicycle Mechanics - Triple to double--use same crank arms??

I've currently got an Ultegra triple set up and want to convert it to a double.

Does the ultegra double crankset use the the same crankarms as the triple? Can I just buy new chainrings instead of a whole new crankset?

Many thanks! :)

I've currently got an Ultegra triple set up and want to convert it to a double.

Does the ultegra double crankset use the the same crankarms as the triple? Can I just buy new chainrings instead of a whole new crankset?

Many thanks! :)

Ummm, your 2 questions don't seem to jive.

First question:
No, the Ultegra double crankset does not use the same crankarm as the triple. The left crank is the same, but if you want a double then you have to buy a new RIGHT double crankarm.

Second question:
If you buy just chainrings, this will do nothing for you to switch from a triple to a double.

You have several choices if you want to convert to a double setup:

1)
If your chainrings on your current setup are worn then buy a new right crankarm with new chainrings. You will also need a new bottom bracket with a longer spindle. IF the chainrings you have now are worn, this will be less costly than buying a crankarm and chainrings seperatly.

2)
If your chainrings are in good shape then you can just buy the right crank arm (no chainrings) and remove the 2 larger chainrings off your triple and transfer them to the double. You will still need a new bottom bracket.

3)
You can just remove the inner chainring on your triple and adjust the inner limit screw on your derailler to prevent shifting down onto the, now missing, small chainring. This will cost you nothing.

Why not just stay with a triple tho? I have 105 and it is a triple. Sure I don't use the small ring much, but it is there when I need it.

Digger

If you get a new right crank arm you need a shorter BB 109.5mm for double, 118mm for triple (Octalink).

In some cases, buying new rings would cost just as much as a whole new crankset. Of course with a double crankset, you'll need the new BB too, just to get a proper chainline.
Check Ebay, you can find double 105 cranksets for $60, new.

You will also need a new bottom bracket with a longer spindle.



Sorry, to go from triple to double you need a SHORTER spindle. I was thinking the other way as I just switch a double to a triple on my old touring bike.

Again, my apologies.

Digger

Yes, I know about the BB, FD, RD, changes I'll need to make. Was just looking to save some money on the crankset.

I just checked Shimano's website (which I should have done first) and they are indeed different part numbers. Thanks for responding.

The difference is basically the mounting points for the inner ring.

Yes, I know about the BB, FD, RD, changes I'll need to make. Was just looking to save some money on the crankset.

I just checked Shimano's website (which I should have done first) and they are indeed different part numbers. Thanks for responding.

You don't actually need to change the RD and FD. I converted to double on a previous bike and the triple derailers work fine. The rear derailer just doesn't have to take up the chain slack of a granny gear.

You can just remove the granny gear, adjust the low limit on the FD, retension the shifter cable, and, if you mostly ride in the middle ring (42t), the chainline will be fine. You'll have less access to the larger cogs in the big ring though.

I'm don't know if it'll work, but you may be able to use a 109.5 spindle with your triple crank with it's granny gear removed. Then the chainline may be OK.

You don't actually need to change the RD and FD. I converted to double on a previous bike and the triple derailers work fine. The rear derailer just doesn't have to take up the chain slack of a granny gear.

You can just remove the granny gear, adjust the low limit on the FD, retension the shifter cable, and, if you mostly ride in the middle ring (42t), the chainline will be fine. You'll have less access to the larger cogs in the big ring though.

I'm don't know if it'll work, but you may be able to use a 109.5 spindle with your triple crank with it's granny gear removed. Then the chainline may be OK.

I would give this a shot first. In the worst case you will just need to buy a double crankset, if it works, you save the money.

You don't actually need to change the RD and FD. I converted to double on a previous bike and the triple derailers work fine. The rear derailer just doesn't have to take up the chain slack of a granny gear.

Really? Doesn't the double FD have a trim stop for each chainring?


I'm don't know if it'll work, but you may be able to use a 109.5 spindle with your triple crank with it's granny gear removed. Then the chainline may be OK.

I might give this a shot. I don't care so much for the weight savings of the double as I do about smoother shifting. Thanks! Excellent idea.

Really? Doesn't the double FD have a trim stop for each chainring?



I might give this a shot. I don't care so much for the weight savings of the double as I do about smoother shifting. Thanks! Excellent idea.

The stops and everything are in the shifters.

You won't get smoother shifting just my taking off the granny gear and retuning. Using the triple TD should provide shifting about the same as the original. Same with the RD. Going to a short cage RD is where you should see the improvements.

The stops and everything are in the shifters.

Uhhh, I knew that.....really :o :D

Well, ok, let me save face here...I didnt realize that the only diff between the FDs was the cage size.

Thanks for the correction.