Lower gearing on a double

Civilian_Target

I have a Shimano Sora 9-speed double, with a 50 / 34T chainring at the front and 26T in the largest sprocket in the back.

The problem is that this isn't giving me the traction I need to climb to work with panniers on the back without getting out of the seat. I would like to be able to spin up the hills and save my knees. It also leaves the bike a bit underspecced for touring.

The local bike shop suggested that I could change the front chain ring for a triple at 50 / 39 / 30T (at 210 euros including fitting, since I would also need a new front chain-movey-thing, a new chain and a longer cage at the back). But... by my calculations this won't buy me a whole lot more power... maybe enough to get to work, but not enough for a weekend climb in the alps.

What can I do to get a bit more climbing power? Could I put in a 32T back sprocket, for example?

DirkVoodoo

Well, you're not buying power, the problem is a lack of it.

30-27 should be enough really, I can't think of much more you can do other than maybe carrying less on the bike. For your weekend in the alps will you be operating from a base where you could maybe leave most of your gear during the day? If not, you may need to rethink your plan for the trip.

EDIT: You could get a smaller front ring, 74mm BCD I think on triple inner rings so maybe look at different sizes. This may limit your gearing at the upper limit though and I'm not sure if you reach a point where you might be going so slow as to not move forward.

Paul Kiernan

Are you sure it's a 26 on the back? I thought 9-speed were either 25 or 27 largest sprocket?

DualFrontDiscs

For loaded touring, sub 29 gear inches are recommended.

Which is to say, a 700c wheeled bike should have a front chain ring SMALLER than the largest rear sprocket.

Other reasons for such gearing, other than loaded touring, include damaged knees, not strong enough, very steep/ very tired. If you combine all of the above reasons, you should definitely have such gearing.

DFD.

cdaly_

Cheapest option would be to change the cassette. 12-27t might be enough but, given that I'm using a 30x28t lowest gear, I can see how you might want more. a 12-30t cassette would get you those lower gears but at the cost of bigger gaps between gears. I found I didn't like the big gaps.

If you want to avoid the gaps, converting to a 52/42/30t triple and a 12-28t cassette will get you a nice wide range with small gaps between gears. That's gonna cost you though...

blorg

I have 30-28 which I am living with as it was what I have but frankly that is not enough for extended loaded touring, I could do with mountain bike gears up front.

DualFrontDiscs

blorg wrote: »

I have 30-28 which I am living with as it was what I have but frankly that is not enough for extended loaded touring, I could do with mountain bike gears up front.

+1

Civilian_Target

Paul Kiernan wrote: »

Are you sure it's a 26 on the back? I thought 9-speed were either 25 or 27 largest sprocket?

Not 100%, I did a quick count and came to 26...

I'd get a gear ratio falling from 1.4 to 1.05 if I moved to a 32T cassette at the back (no - the larger gaps don't worry me, I'm used to hub gears) - what else would I need if I did that? Just a new chain and a larger deraileur cage?

cdaly_

I have a suspicion that a compact would already have a long-cage derailleur to cope with the 16t difference up front. If that is the case, It would probably cope with a 32t at the rear. You would, however, have to avoid cross chaining even more as it wouldn't cope with 50x32 (too tight) or 34x12 (too loose).

papac

cdaly_ wrote: »

I have a suspicion that a compact would already have a long-cage derailleur to cope with the 16t difference up front.

Compacts use short cage derailleurs generally afaik. Its one of their selling points- you retain the crisp shifting.

You could run a 34tooth mtb cassette and derailleur on the back with a longer chain I reckon.The cheap ones work fine (if sloppy) and its no huge loss if you decide on the triple solution later.Triples are best for touring imo.

rughdh

papac wrote: »

Compacts use short cage derailleurs generally afaik. Its one of their selling points- you retain the crisp shifting.

You could run a 34tooth mtb cassette and derailleur on the back with a longer chain I reckon.The cheap ones work fine (if sloppy) and its no huge loss if you decide on the triple solution later.Triples are best for touring imo.

I've an 8-speed 50/34 with 30T as the largest sprocket on the cassette, which now gets me up anything. I had a 32T on it for climbing the Maria Blanc (Pyrenees), but 30T probably would have done me. The same applies to 9-speed (and even 10-speed to a degree if you don't mind paying through the nose). It's a matter of availability of big-toothed cassettes.

With regard to touring: I got up Djouce (Wicklow Mts) with this setup fully loaded. I use a long cage derailleur. It came with a short cage as papac said. So new chain, long cage derailleur (high or top normal) and cassette is about right.

Single Malt

Get a medium cage mtb rear mech and a mtb cassette 11-32. That will get you closer to the required ratio for what you are doing, otherwise its triple, which is a big investment.

rughdh

Single Malt wrote: »

Get a medium cage mtb rear mech and a mtb cassette 11-32. That will get you closer to the required ratio for what you are doing, otherwise its triple, which is a big investment.

It's worth looking at the manufacturers stated "Total Capacity" of the rear mech.

(32 - 11) + (50 - 34) = 37 and a 34T big cog would bring it to a 39. I think I had to go for a long cage with a Total Capacity of 45 because the capacity of the medium cage was too small. You may can get away with exceeding it by a tooth or two, though, depending on the manufacturer of the mech. Something to consider.

IM0

Civilian_Target wrote: »

I have a Shimano Sora 9-speed double, with a 50 / 34T chainring at the front and 26T in the largest sprocket in the back.
......It also leaves the bike a bit underspecced for touring.

The local bike shop suggested that I could change the front chain ring for a triple at 50 / 39 / 30T

....but... by my calculations this won't buy me a whole lot more power... maybe enough to get to work, but not enough for a weekend climb in the alps.

What can I do to get a bit more climbing power? Could I put in a 32T back sprocket, for example?

been there done it touring with 30kgs+ in the alps that is. do yourself a favour and get the tripple AND a 32t, youll need it if its loaded touring on some passes.

Civilian_Target

Wow, thanks for the tips guys.

So, I have a short cage derailleur at the moment, it's 29T.
My current rear cassette is
(26-12) = 13
(50-34) = 16 +13 = 29

Actually, the long cage one only has a capacity of 31T, so it's not exactly a massive improvement

There doesn't seem to be a good way out of this one - if I'm going to do the conversion to the triple though, it would seem like a good plan to get a larger rear cassette too. If I'm going to do that though, it seems I'm replacing the whole groupset. Ouch!

blorg

The term "capacity" used on its own refers to the range the derailleur will support, not the maximum cog size. The longer the cage the more chain slack the derailleur can take up; the greater your range the more chain slack you will have in small-small needing taking up.

Shimano road derailleurs from a given groupset generally support the same largest cog size (was 27T, now 28T on 10 speed road) but the range is different- 29T on short cage but 37T with long cage (could you possibly have misread this as 31T?) MTB derailleurs can have even greater ranges.

These numbers are somewhat conservative and depending on your bike you may get away with far more; there are reports of people running 32T on the back with standard Shimano road derailleurs and I know I get away with 50/34 12-28 with a short cage on one bike which is notionally out of spec (the range) but can't use 50/34 12-27 on another without excess chain slack. What you get away with will depend on your frame; Shimano specs are what will work on every bike.

As you are running 9 speed you can get a 32T MTB cassette relatively cheaply which is probably the easiest/cheapest thing to try first.

papac

Use an MTB derailleur.
My daughters bike has an 11-34 8-speed cassette with an mtb derailleur (deore).Sora shifter. Massive gear range but gappy.

Touring bikes mix mtb and road stuff all the time.
Its by far the cheapest solution.

penexpers

Sugnio have a new chainset coming out soon (was meant to be out in June). A double with a 74mm inner BCD which would allow lower triple rings to be used on a double.

http://www.suginoltd.co.jp/english/ox801d_main_english.htm

The only downside is if you use a 74mm BDC chainring, you are limited to 48T for the outer chainring.

papac

http://www.chainreactioncycles.com/Models.aspx?ModelID=5045
http://www.chainreactioncycles.com/Models.aspx?ModelID=38673
http://www.chainreactioncycles.com/Models.aspx?ModelID=6053

Less than fifty quid.

Al Wright

I had a similar problem with lack of leverage on my old sports bike that I used for light touring. The chainset was geared towards road 50/40 T and cassette was 7 speed, 11 to 28 (or thereabouts). I replaced the rear mech to longer reach and replaced cassette with MTB type, 12-33. It works well being older friction shifter type. At the time the cost of the parts was about 50 euros.

Civilian_Target

OK... I think I get what you're saying now.

My rear deraileur is definitely at max tension now on the two large cogs, it even squeaks a bit when I turn it.

But from what I've understood, I can buy a 32T cassette now anyway, and without replacing anything else I should still be about to use it fine on the 34T chainring, and still be able to use it on the 50T chainring in the higher gears. Then, if I want to make the change permanent, the likelyhood is that I will be able to do everything, except maybe largest-largest, by changing only the chain and the cage.

Sounds good!

Single Malt

Civilian_Target wrote: »

OK... I think I get what you're saying now.

My rear deraileur is definitely at max tension now on the two large cogs, it even squeaks a bit when I turn it.

But from what I've understood, I can buy a 32T cassette now anyway, and without replacing anything else I should still be about to use it fine on the 34T chainring, and still be able to use it on the 50T chainring in the higher gears. Then, if I want to make the change permanent, the likelyhood is that I will be able to do everything, except maybe largest-largest, by changing only the chain and the cage.

Sounds good!

Oil the bushes on jockey wheels and chain if it squeaks, that has nothing to do with what you are saying!

IM0

Single Malt wrote: »

Oil the bushes on jockey wheels and chain if it squeaks, that has nothing to do with what you are saying!

and dont use the large large combination either :rolleyes: