105 Rear mech capacity
I've not got too much experience of Shimano drive train, and I'm putting together a winter bike for my daughter to use. Anyone know if a 105 rear mech, short cage, will be able to cope with a 50/34 and 12/27 combination. I'm pretty sure the spec says 29T max, and I'm looking for 31T.
Reckon it'll work?
Reckon it'll work?
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It will cope with a 50/34 and 12/27 no problem. A 31 on the back would require a long cage.
Or did you mean a 31T on the front? 31 on the front with a 27 on the back would be fine.
Shimano quote 29T total. I want 31 total (50/34 = 16 + 12/27 = 15)
It shouldn't work, but I'm asking if, just maybe, it does!
Anyone?
PS Sorry Pokerface, read your post again, and you say it will work. Thanks, I'll give it a go.
In any case 50/34 with 12/27 works fine. I have it on 3 bikes with no trouble what so ever. Just run the chain as long as possible as it changes better. The little tab on the rear mech cage should be just clear of the chain when in small / small gear.
There are are two critical limits for rear mechs
1) the biggest rear cog that the mech can accommodate
2) the total capacity of the rear mech, f+r combined (the ability of the mech to 'soak up' changes in chain length.
My question was really refferring to 2) above. How much 'wrap' can the 105 take up.
It's different for Ultegra. (Goes up to 28T cassette and 33T total)
What mechs are you running? In doing a bit of looking up - it seems the 105 mechs don't have as much give as say, the Ultegra ones. If you are running 105s - then the OP is safe with his choice.
I have the 105 short cage on my 50/34 12/27 and it works fine.
https://giffgaff.com/orders/affiliate/jslaterb
She's at Bath University and has been complaining about some of the hills around there. Bath must surely be the worst cycling city in Britain. She's said that she doesn't fancy cycling up Bathwick Hill (and there are some much steeper, apparently) with a bag full of books every morning . Kids today, eh :roll: