/ chainring size / compatability

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Richard Carter - on 05 Mar 2014
I bought a shimano 6800 compact (50T/34T) and then I saw they sell a 36T inner chainring. Now the 36T is supposed to go with the 52T outer, but I was wondering, could I fit it instead of my 34T? The BCD is the same, the only issue is the ramps/pins won't match up properly, is this something I should worry about?

Escher - on 05 Mar 2014
In reply to Richard Carter:

Yes, it will be absolutely fine.
andy - on 05 Mar 2014
In reply to Richard Carter: I'd spotted the 52-36 option and might well go for that come new-chainset-time - interested why you'd want a 36 with a 50 though - I'd want the 52 more than the 36 - as I've got a bit fitter I find I don't need my lowest gear much so am willing to exchange a super-low bottom for a bit more umph on the chaingang - are you thinking less of a jump between rings is the main benefit?

Richard Carter - on 06 Mar 2014
I already have a highly geared bike (52/39) for going quick, this is for a bike that's just for bimbling around on. 34 is a bit low for me so 36 would be good, but I don't really have any need for 52T at the front. 50T / 11T is ample for me for top gear. I'd have probably gotten 46/36 if my local shop had it in :-P

Richard Carter - on 06 Mar 2014
In reply to Escher:

Cheers :)
SteveRi - on 06 Mar 2014
In reply to Richard Carter:
I used 36/50 for a bit on my last bike because that's what I had hanging around. I actually found it quite a good combination - plenty low enough most of the time and less of a gaping fall dropping down to a 34.
Lord of Starkness - on 06 Mar 2014
In reply to SteveRi:

I got a s/h 36/50 Stronglight Impact off fleabay for my winter hack to replace the old Campag Daytona 39/53 it came with. I'm getting too old to push big gears! My old 9 speed Veloce rear mech has a short cage, and the front changer has a max tooth difference of 14. The rear cassette is a 14-28

If I'd gone for a full compact setup I'd have had to change the whole transmission, so it was the cheapest way do give me a better spread of gearing. All I needed to do was take a couple of links out of the chain.

My good bike has a full 10 speed compact setup - 34/50 and 13-29 cassette so I've got some lower gearing when tackling longer and steeper stuff in the summer months.
Richard Carter - on 06 Mar 2014

Just out of curiosity... how do modern drivetrains cope with such a large difference in the chainrings(16T)? Isn't it a bit clunky? Aside from the fact 34T might be too low, the large gap was also a factor putting me off a bit :-P A quick calculation and I realised that 34T/36T wasn't a big a difference in gearing as I'd thought.

I'm just thinking maybe I should not bother getting the 36T and have a go with the 34T, it would be a lot less effort as it's a special order part that'll take a while and cost 20 :-P
Post edited at 10:36
Richard Carter - on 06 Mar 2014
In reply to Richard Carter:

Too many options. Arghhhhh! :-P
Escher - on 06 Mar 2014
In reply to Richard Carter: I run 52-36, same gap as 50-34, I generally double shift when changing chainrings to even out the gap I.e. Down the block when moving to inner ring, up the block 1 or 2 when changing into the big ring. It becomes second nature. Not a problem for most people, compacts are very common. It depends on the gear ratios you want. It's a playoff between closer chainrings 50-36 and closer ratios at the back. E.g. If you want closer a ratio cassette then get a 34, if you want a wide cassette like an 11-28 then maybe go for 36 up front as long as that's low enough for the riding you do. But to be honest either will be fine and you'll want to buy something extra later on the future anyway so you'll end up trying the one you don't have when there's money burning a hole! :-) so just pick one it'll be fine either way.

SteveRi - on 06 Mar 2014
In reply to Richard Carter:
The 50 lets you stay in the big ring for longer, so you end up doing less double shifting for one thing.
digby - on 06 Mar 2014
In reply to Richard Carter:

I had a compact on my Boardman Hybrid and always found the jump too big between the rings, so go for the 36. After the crank worked loose irreparably I changed the whole crankset to a Shimano 3 ring and it's so much better to use
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Richard Carter - on 12 Mar 2014
Yeah I don't like it.

Anyone got a 6800 double that they want to swap for a compact :-P

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