Dual to triple crank

[Alan Farroll]

Hi,

I have a Giant Defy 5 2013 version. I like the bike but sometimes I am struggling on very steep hills. The bike has a front mech of a dual crank set. Is it possible for me to upgrade this to a triple crank set? If so how will I tell what components I need? What will suit the bike etc?

I am not afraid of tackling this myself.

Thanks in advance

Alan

 

[ColinJ]

It is definitely possible but it might be too expensive a job for what is a fairly inexpensive bike.

You would obviously need a triple chainset, You might need a new front derailleur and/or a new rear derailleur. You might need a new left shifter. You would almost certainly need a longer bottom bracket. You might need a longer chain.

The cheapest option would be to put a new cassette on instead. I looked at a couple of adverts for your bike and they suggest that the bike has an 11-28 cassette on it. You could try something like this 11-34? You would need a longer chain and you might find that your rear derailleur couldn't cope with it, so that might have to be changed too.

 

[Dogtrousers]

I looked up your bike here.

It says
Chainset 50x34
Cassette 11-28
Rear mech Shimano 2300

I looked up your rear mech here
It says
Range 35T or less.
Largest sprocket 26T (That's what it says, even though the biggest on this bike is 28)

Your bottom gear 34/28 is ~32"

You could consider just using a cassette with lower gearing.

If you replaced the cassette with a 12-32 cassette you would get a bottom gear of 34/32 which is ~28" (significantly but not massively lower). This would require a derailleur capacity of 36, which is only one more than the rated capacity so is probably OK. However it's 6T bigger than the rated biggest sprocket, so may not be OK.

So if you went down the cassette change option you may have to change the rear mech.

If you wanted to change to a triple you would need:
New crankset
New front mech for a triple
New Bottom Bracket as the axle length will be different to maintain the chainline
New left brake lever/shifter to get a 3 rather than 2 speed + cable
Possibly/probably new rear mech depending on what you've got
New chain in either case.

Or you could do what a certain pro cyclist who we don't mention Cough*Lance*Cough did some years ago and have a down tube shifter for the front mech.

 

[ColinJ]

Ha ha - for once in these situations, I got my post in first, probably because I didn't type as detailed an answer!

 

[cyberknight]

Just cheaper to replace the chain, cassette and rear deraillier , get a long cage mech like a sora which will work fine , a wider range cassette and maybe a new chain if you go for something like dogtrousers said or just get a 12-28 which you should be able to do without changing anything .

 

[Deleted member 35268]

I have a Defy 2, with a Triple up front. 9 speed chain and cassette.

Came with;
Tiagra Triple Front Derailleur
Tiagra Triple Shifter (left side handlebars)
Tiagra Triple Chainset

I replaced some of the parts with;
Ultegra Triple Front Deraulier
Kept Shifter
Ultegra Triple Chainset
+ Changed rear derailleur to Ultegra also.

I reckon Ebay is your best bet for sourcing the parts (partly used), plenty of people will go the other way, Triple > Double.

Personally, the Triple helps me on the hills, and i'm not slow on them either. Depends where you live and the gradients you have to do.

 

[ColinJ]

... or just get a 12-28 which you should be able to do without changing anything .

How does a 12-28 cassette give a lower gear than an 11-28?

 

[cyberknight]

How does a 12-28 cassette give a lower gear than an 11-28?

It doesnt and i wasnt refering to your post although if the OP is struggling with the bike uphills atm i doubt he would need a 50x11 unless hes is doign about 32 mph + on the flat .

 

[ColinJ]

It doesnt and i wasnt refering to your post although if the OP is struggling with the bike uphills atm i doubt he would need a 50x11 unless hes is doign about 32 mph + on the flat .

I agree that the OP (and most other riders) would never need a 50x11 - I never really needed my 53x13 except on long downhills, so I have downgeared and now have a 48x13 which I can pedal to 32+ mph and I am happy to freewheel beyond that.

 

[Alan Farroll]

Hi all,

thanks for all your responses. Wow! The technical stuff is awesome and I wish I had time to get into it in that depth - I grew up in an era where it was all Raleigh bikes with the odd BMC. Also, I hope I am not causing an argument here. The addition of a third crank seems quite expensive going by what you guys are saying, although the left brake shifter already accommodates a third crank as when I change down I have to change up "as if" there is a third crank. I think I will look into the cheaper option of better rear cassette. However what about the new "compact" dual crank set? I have found some links to those. Would that be a better option?

Thanks again

Alan

 

[raleighnut]

A 50 - 34 is a compact, but a smaller one should fit on ok, 48 - 30?

 

[Alan Farroll]

Ah! So my current crank set already is a compact! Thanks raleighnut. In fact thanks everyone. It looks like I just stick with what I have or go for the expensive upgrade to triple crank. I have learned more about bikes from this.

Regards

Alan

 

[andrew_s]

An extra compact double may be as cheap as changing lots of bits.

This Sugino OX601D is supplied with 44/30 chainrings and a bottom bracket (external) for £160, and permits inner chainrings down to 24T. 44x11 is as high a gear as I'd ever use.
Alternatively, this VO Crand Cru 50.4 is supplied at 46/30, no BB (square), for £140, and allows inner chainring down to 28T.

Using either of these would mean that the only other change would be to move the front mech down the seat tube a bit & readjust.

There are also assorted MTB doubles, typically 44/22 or 42/22. These have a wider chainline, so you'd only get a good chainline on square taper models (if any exist) where you can put a shorter BB on

The smallest inner chainring on a regular road compact double is 34T (or you may be able to find 33T)

 

[youngoldbloke]

Quite expensive those chainsets. You already have a compact 50-34. The simplest (and cheapest) way to get a lower gear is to change the cassette to one with a bigger bottom sprocket - as others have pointed out. I am a great believer in 'try it and see'. I suspect your rear mech will handle a 30T, (I run a 30T on an old Tiagra set up with no problems at all), and may well accomodate a 32T. 8 speed cassettes are not expensive, new shifter, chainset, and bottom bracket will cost a lot more!

 

[Alan Farroll]

Thanks everyone. Some good feedback