Converting Triple to Double

CakeLovinBeast
Posts: 312
When I initially bought my bike, I was only able to get the model that I wanted as a triple 50-39-30 and to begin with on the hills of Devon, I was glad of it! Nowadays, I'm able to get up pretty much all I want on the 39, and so I'm considering a bit of an upgrade/weigh-saving exercise to change it to a double, so I'm looking for some advice please. The bike is currently full 105, but I'm planning to introduce some Ultegra for a bit of bling too.
- I'm assuming that I need to replace the front derailleur in addition to the left-hand shifter, else it'll throw too far... Is that right?
- Can I simply remove the chainset, unbolt the 30T inner ring, and re-install the 50-39 as a double? Or do double and triple chainings somehow differ?
- I know that a compact would usually be 50-34, but I'm comfortable with my 39 now, so don't see the need to replace it, unless I'm going to cause myself issues? Presumably so long as the chainrings have the same PCD, I'm of the understanding that that'll be OK, so long as there's not too big a difference in the number of teeth?
Thanks in advance!
- I'm assuming that I need to replace the front derailleur in addition to the left-hand shifter, else it'll throw too far... Is that right?
- Can I simply remove the chainset, unbolt the 30T inner ring, and re-install the 50-39 as a double? Or do double and triple chainings somehow differ?
- I know that a compact would usually be 50-34, but I'm comfortable with my 39 now, so don't see the need to replace it, unless I'm going to cause myself issues? Presumably so long as the chainrings have the same PCD, I'm of the understanding that that'll be OK, so long as there's not too big a difference in the number of teeth?
Thanks in advance!
Twitter: @FunkyMrMagic
0
Comments
-
It depends how nice a job you want to do of it.
You could just take the granny ring off and put in a longer bolt for the limit adjusting bolt on the derailleur. Your shifter would let the cable go slack if you tried changing into the non existent gear, but the chain shouldn't come off if you've set the stop correctly.0 -
Why not keep the triple and get e.g. a 12-21 cassette. 30-21 is roughly the same as 39-27. Cutting out the lower ratios this way gives you much tighter gearing throughout the range, and the ability to fit a climbing cassette if you ever do some epic mountain trips. Triple are underrated!0
-
The shimano tech docs tell you what restrictions there are in terms of minimum and maximum tooth differences between the rings. Typically the figures are for a minimum of 11 difference between outer and middle and max of 20 overall. So you should be able to go to 50/34 OK. If you want to just save weight by losing the granny ring then as you say just unbolt it and then 'dial it out' with a combination of lo limit and cable tension adjustment. You could try this with the granny ring in place first before you do any surgery.0
-
Thanks for that.
I realise that there's no real benefit by losing the granny ring, but it's part of a plan to build up a new race bike on a limited budget. Step one is to get new "race" wheels. Step two is to begin a staged phase-out of some of the 105 triple to Ultegra double. At that point, I'll then look to buy a new carbon frame and transfer components over... As I replace the 105 with Ultegra, I'll move the 105 bits back over to the "old" frame as a winter bike.Twitter: @FunkyMrMagic0