Current setup is a 12-28 cassette with a 26/36/46 triple up front with a Shimano 105 rear mech.
I have ordered a double chain set and bb (Shimano and will fit) 34/50
Cassette 11-34 due to big hills and to compensate for losing the 26 up front which gets used frequently.
New chain 🙄
How do I check whether the rear mech will take this increased cassette size?
Any other considerations other than the limit screws on the front mech?
All transmission is Shimano 10 speed
You'll hate the big jump from 34/50 😈
How’s it different from 36/52 - 16t difference
You’ll hate the big jump from 34/50
Only of you can't figure out how to change gears properly 🙄
As for actual issues, your front mech may well not work with a twin ring over a triple as the spacing between the rings might be different, the same will go for the shifter - it might not pull eno8gh cable to shift across the set up you're proposing.
Other than that, once you get it into your head you haven't got a twiddly 26t at the front you'll be fine.
Double specific front shifter? Is the distance between chainrings not the same?
Curse of the compact! Learn to spin
All these people on compacts who stick mainly in big ring would be better with 1x
Have you got STI's (changers, not the other sort...)? If so, you'll obviously need a new lefty double. Is your current rear mech long cage? If so, you might get away without a goat link or similar but you might not be able to run big/big or small/small. Is the front der 105? Might be alright, might not. Is it 10 speed before and after? So you're reusing the chain? Just watch length in case you need a bit more which you will if you end up in 50/34 by mistake.
If so, you’ll obviously need a new lefty double
No, you don't
simondbarnes
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If so, you’ll obviously need a new lefty doubleNo, you don’tsimondbarnes
Subscriber
If so, you’ll obviously need a new lefty doubleNo, you don’t
Are you saying you can run a double with 2 clicks of 3? I did not know that.
Yes, you can.
Are you saying you can run a double with 2 clicks of 3?
One of two 🙂
Well there you go. Can you go the other way...? 😜
It’s like when we used to use triple mechs and shifters on 2x10 MTB’s. You adjust the limit screws and then remember not to hamfistedly try to push the lever past the tension looking for a third stop (do not try this, it will break things).
Agree on ‘curse of the compact’ though. When I ran a compact I stayed on the big ring apart from bailouts. I might as well have been on a 1x. Shifting to 36-46 ‘CX’ ratios fixed this for years (dislike SRAM road but prefer their MTB stuff). Now ‘GRX’ is happening I may ditch the front mech all together...
Why?
Not even getting a lower bottom gear
So all I need to order is a medium cage rear mech then it will all work?
Why?
This.
Are you saying you can run a double with 2 clicks of 3? I did not know that.
You can, but having previously done that and broken the shifter by forgetting what gear I was in and accidentally mashing it into the absent third position, I'd say a double shifter is preferable. (Maybe they're more robust these days.)
But then if I had a triple shifter I'd just use a triple chainset, especially if the granny ring "gets used frequently". (The one time I swapped a triple for a double was to deliberately deny myself the lower gears.) You get a wider gear range, less dramatic changes between gears, and a more usable middle ring for cruising on the flat. The only loss, to my mind, is that the big ring works a little less well with the larger sprockets. (If you have a square taper you can pull the chainline back in so that the middle and big have the same positions as a double and the granny only plays nicely with the larger sprockets… which if you ask me is just about the ideal if you need the gear range of a triple.)
As above, I can't quite get my head round why, if you use the 26 a lot, you'd fit a double.
I've switched back and forth a few times.
Are you saying you can run a double with 2 clicks of 3?
Yes, my bike is this way now, BUT IT'S VERY IMPORTANT to use the outer two clicks of the triple shifter, not the inner two. If you use the inner two, then you try and mis-shift to the outer one then it can get stuck halfway into the shift before pulling against the mech's cable stop and the strain snaps a small part inside the shifter. So your double is set up as big and middle.
Also, double front mechs are quite different to triple ones. The double ones don't work well at all with triple, but I didn't try the other way round.
As above, I can’t quite get my head round why, if you use the 26 a lot, you’d fit a double.
Because if you have a wider spread on the back you end up front shifting much less. Compounded by the fact that with a triple you get slightly more chain line issues because on the middle the chain can rub on the big ring when using the bottom end of the cassette.
Because if you have a wider spread on the back you end up front shifting much less.
Hm, not convinced, but then I treat a triple as a double with some bail-out gears (which get used when the bike's loaded or when I'm whacked, but not for most riding). Plus a wider range means wider spacing, which many people don't like, though personally I don't have a problem with it (I mostly use 12-30 cassettes these days).
Compounded by the fact that with a triple you get slightly more chain line issues because on the middle the chain can rub on the big ring when using the bottom end of the cassette.
Struggling a bit with the logic of that one. With a compact double you've got a more inboard chainline (ie a greater angle of the chain when in the smaller sprockets) and a greater difference in ring sizes (ie the chain will be passing the big ring at a point where it reaches further backwards towards the chain). Surely a triple is less likely to suffer this issue? (I don't have it, but admittedly my triple is on a bike with long chainstays.)
molgrips
Yes, my bike is this way now, BUT IT’S VERY IMPORTANT to use the outer two clicks of the triple shifter, not the inner two. If you use the inner two, then you try and mis-shift to the outer one then it can get stuck halfway into the shift before pulling against the mech’s cable stop and the strain snaps a small part inside the shifter. So your double is set up as big and middle.
One of my road bikes was like this when I bought it - it's got a triple Sora shifter, but a compact double. I think the mech is a triple too.
It works fine when set-up as above.
I treat a triple as a double with some bail-out gears (which get used when the bike’s loaded or when I’m whacked, but not for most riding)
This
As others have said, unless you've got a very good reason, I wouldn't bother. With a triple you get nice smallish gaps between gears and shifting at the front is really not that problematic.
I've got a 24/36/46 with an 11/28 cassette on my commuter/tourer/trundler and it's great. I spend most of my time in the middle ring, trundling along.
I've got a compact with 11/28 on my nice bike though cos, you know, fashion 🙂
How’s it different from 36/52 – 16t difference
It's not, both are big jumps, if you are happy with top being 46 to 12 originally why don't you get a more CX type double rather than a compact unless your aim is to increase the high gears without losing the low, in which case why change from a triple?
So all I need to order is a medium cage rear mech then it will all work?
Shimano 5701 GS rear mech is only rated to 32t. It'll probably work with a 34 depending on mech hanger length / angle though.
If you do that wierd thing they're recommending up there, yes. Sounds like a rear derailleur, mebbies a goat link copy and some chain as 50/34 is definitely more chain than 46/28.