Smallest inner ring possible on Standard Cranks

dubbs2009

Hi all, I am running 53/39 chainset at the moment with 12-27T cassette.

Can I swap the inner ring down from 39T to 36/34T or will this not work with the front mech I have? Would I need a tripple mech to all it to travel that far?

Cheers

marcusjb

A standard crankset has a BCD of 130mm (Shimano world)- from memory, the smallest ring will be a 38T.

You need a compact crankset (BCD 110mm) to get a smaller inner ring than that.

Front mech should work just fine if you change to a compact - just needs lower a couple of mm.

(edit to add - if you make your inner ring 34/36, you will also be changing your outer ring to a smaller tooth count, as the height between the two rings will be too great for the mech).

dubbs2009

OK thanks - thought it would not work - changing the crankset is the answer and lowering the front mech a bit... I've also heard chain might need shortening a bit? e.g. from 53/39 - 12-27T to 50/34 - 12-27T ?

marcusjb

Yeah - you'll lose a few links. Unless the existing chain only had a few hundred miles on it, I'd probably just replace the chain at the same time as the crankset - but that may be me being overly cautious.

dubbs2009

marcusjb wrote:

Yeah - you'll lose a few links. Unless the existing chain only had a few hundred miles on it, I'd probably just replace the chain at the same time as the crankset - but that may be me being overly cautious.

OK thanks - chain is pretty new - will need to get a chain removal tool next! lol - the tools one needs for the jobs are endless eh!

andrewc3142

I have the same set-up on my Acciaio, 53-39 12-27, and thought long and hard about changing to a compact.

However, in the end I decided against after trying out one on a friend's bike. Something good and smooth about the big chain ring and overall the compact just didn't feel right, at least for me.

It would be different if I do big climbs outside the UK, but I don't have the opportunity (job, family, time, etc) and for the Surrey Hills, Cotwolds, etc even if steep the climbs are short enough to go fine on a standard.

Next birthday is 55 so perhaps in a few years I might have a different view ….

dubbs2009

andrewc3142 wrote:

I have the same set-up on my Acciaio, 53-39 12-27, and thought long and hard about changing to a compact.

However, in the end I decided against after trying out one on a friend's bike. Something good and smooth about the big chain ring and overall the compact just didn't feel right, at least for me.

It would be different if I do big climbs outside the UK, but I don't have the opportunity (job, family, time, etc) and for the Surrey Hills, Cotwolds, etc even if steep the climbs are short enough to go fine on a standard.

Next birthday is 55 so perhaps in a few years I might have a different view ….

Thanks for the response Andrew - I am gonna head out on the bike tomorrow and see how I fair on some of the steep climbs around here in the Cotswolds - I would rather not mess around and stick on a compact crankset to be honest as would want to keep the same BB which means there is only 1 compact crankset available - Shimano Claris which is a pretty low end piece of kit... I currently have Ultegra 6500 on it - so would be a big down step...

I will only ride this bike in the winter so can easily tailor the riding to suit the bike it climbing is a no go I guess... messing around adding new compact cranks, shortening chain and moving front mech all sounds like a bit of a pain to be honest... All to make climbing a few hills a bit easier... no pain no gain eh! lol

All that said, the 25% climb near here is almost impossibly on 34/27 so I think with 39/27 it will be game over... just need to avoid that particular beast!

tommo7567

It may be worth considering changing your cassette instead which would be cheaper. I had a similar quandry with a standard crankset on my ribble with 39 tooth inner ring and 11-25 cassette. For £40 Ive just changed the cassette to a 105 11-28. It felt so much better on my club run yesterday and not that different from riding my compact and theres plenty of hills round Herefordshire.
Best of all there was no fettling required and no adjustments to the derailleurs needed.

dubbs2009

tommo7567 wrote:

It may be worth considering changing your cassette instead which would be cheaper. I had a similar quandry with a standard crankset on my ribble with 39 tooth inner ring and 11-25 cassette. For £40 Ive just changed the cassette to a 105 11-28. It felt so much better on my club run yesterday and not that different from riding my compact and theres plenty of hills round Herefordshire.
Best of all there was no fettling required and no adjustments to the derailleurs needed.

Thanks Tom - I have a 12-27T on the back - the rear mech will not work with anything bigger though so it's basically a lot of options to change various parts - e.g. cranks and shorten chain , cassette and rear mech etc... I rode today and yesterday and have managed the hills round here with the 39/27 setup but was looking for some more gears... maybe its good training to not have em! lol - Think I will plump for a cheap 38T inner ring and then just get on with it... no pain no gain eh!

gozzy

When you say the rear mech won't work with anything bigger, is that as stated by shimano, or have you tried it out?

Shimano mechs tend to work with a couple of teeth more than they're rated for. If you need you can screw the b-tension screw through from the other side to increase capacity.

dubbs2009

Gozzy wrote:

When you say the rear mech won't work with anything bigger, is that as stated by shimano, or have you tried it out?

Shimano mechs tend to work with a couple of teeth more than they're rated for. If you need you can screw the b-tension screw through from the other side to increase capacity.

Thanks Gozzy - It's a short arm Shimano Ultegra 6500 - the docs say 27T is the max... I guess I could try sticking on a 28/29T and see if it works...The original setup was a 12-23T - so I've already altered the mech to suit the new 12-27T - I guess much easier / cheaper and simpler to stick on a new cassette than new inner chainring with 1 less teeth.... x2 extra teeth on the granny gear in the cassette would make more difference than 1 less on the chainring yeh?

tommo7567

Dubbs, according to Shimano technical the ss rear derailluer will take a maximum 30 tooth cassette ring so you should be okay.

Durrrrr, edit.....I should learn to read mate...sorry was looking at the Tiagra rear derailleur! :roll:

dubbs2009

tommo7567 wrote:

Dubbs, according to Shimano technical the ss rear derailluer will take a maximum 30 tooth cassette ring so you should be okay.

Durrrrr, edit.....I should learn to read mate...sorry was looking at the Tiagra rear derailleur! :roll:

I have Ultegra 6500 short arm - Think its max 27T yeh?

tommo7567

The spec's say for best performance then 27 teeth but the largest sprocket can be 28 teeth so it is possible buddy.

andrewc3142

and then just get on with it... no pain no gain eh!

dubbs2009

tommo7567 wrote:

The spec's say for best performance then 27 teeth but the largest sprocket can be 28 teeth so it is possible buddy.

Thanks Tommo - will see if I can pick up a 28T cassette

tommo7567

hope it works out mate