Compact double – convert to triple?

[mrmacmusic]

Apologies if this is a daft question, but searching was not my friend...

My Boardman Hybrid Comp runs a compact chainset (FSA Vero 52/34) with Microshift front derailleur, however the SRAM X5 shifter is marked as 3-speed. There are some crazy price drops on drivetrain bits and bobs over at CRC just now, and I'm tempted to convert to a triple setup. The Tiagra triple octalink chainset (4404) is only £32 and matching Tiagra 9-speed triple derailleur (4403) just £8.50

So, would I just need the chainset or will that Microshift front derailleur need replacing too? Presumably I'll need a new bottom bracket as well, as I'm fairly certain the Boardman doesn't have an octalink BB, so how do I work out which I'd need – they seem to not only come in different sizes (diameter x length??) but also different languages (English and Italian)...?!?

 

[Alembicbassman]

Looks like you'll need an Octalink BB, Shimano should have a stated length in the spec sheet, and a triple front mech. The X5 shifter is a 3 speed and the rear mech is X5 MTB so will handle the difference.

Here's the spec sheet.

http://techdocs.shimano.com/media/t...01-4404/SI-1G80A-En_v1_m56577569830606930.pdf

Says 118mm BB for triple to give a 45mm chainline. You can go longer if the chainline isn't 45mm from the centre of the seatpost to centre of middle ring.

Boardman is standard English 68mm shell and threads. You'll need a BB tool to remove it and the drive side is reverse threaded (clockwise to un-do)

 

[mrmacmusic]

Looks like you'll need an Octalink BB, Shimano should have a stated length in the spec sheet, and a triple front mech. The X5 shifter is a 3 speed and the rear mech is X5 MTB so will handle the difference.

Here's the spec sheet.

http://techdocs.shimano.com/media/t...01-4404/SI-1G80A-En_v1_m56577569830606930.pdf

Says 118mm BB for triple to give a 45mm chainline. You can go longer if the chainline isn't 45mm from the centre of the seatpost to centre of middle ring.

Boardman is standard English 68mm shell and threads. You'll need a BB tool to remove it and the drive side is reverse threaded (clockwise to un-do)

Cheers – most helpful

 

[Alembicbassman]

If you use the braze-on mech at CRC you'll need a band on clamp that matches the seatpost diameter of the Boardman like this

http://www.planet-x-bikes.co.uk/i/q/FMPXCLAMP/front_mech_band_on_clamp

Wiggle have a cheap Octalink 118mm BB for £15

http://www.wiggle.co.uk/shimano-es2..._campaign=uk&gclid=CPmAra-KjrUCFaTMtAodCScALg

 

[RecordAceFromNew]

Apologies if this is a daft question, but searching was not my friend...

My Boardman Hybrid Comp runs a compact chainset (FSA Vero 52/34) with Microshift front derailleur, however the SRAM X5 shifter is marked as 3-speed. There are some crazy price drops on drivetrain bits and bobs over at CRC just now, and I'm tempted to convert to a triple setup. The Tiagra triple octalink chainset (4404) is only £32 and matching Tiagra 9-speed triple derailleur (4403) just £8.50

So, would I just need the chainset or will that Microshift front derailleur need replacing too? Presumably I'll need a new bottom bracket as well, as I'm fairly certain the Boardman doesn't have an octalink BB, so how do I work out which I'd need – they seem to not only come in different sizes (diameter x length??) but also different languages (English and Italian)...?!?

Since sram x5 are mtb equipment and iirc the front shifter is indexed you should avoid getting the Tiagra front mech, because being road equipment it requires less cable pull than what the X5 delivers which will make indexing tricky and can mess up your shifter and cabling in the long run.

If I were you I would firstly measure what the existing chainline of the FSA Vero is. If it is 45mm then the Microshift mech might work reasonably without any change but can't be sure because I have no idea what its spec is. If it doesn't work well then something like this or this should be compatible.

If on the other hand your existing chainline is greater such as 47.5mm or 50mm which are not uncommon for hybrids and mtbs then we might need to reconsider options. This has some relevance to your plans.

 

[mrmacmusic]

If I were you I would firstly measure what the existing chainline of the FSA Vero is. If it is 45mm then the Microshift mech might work reasonably without any change but can't be sure because I have no idea what its spec is. If it doesn't work well then something like this or this should be compatible.

Thanks again

I've measured my chainline and it's 45mm, so presumably that means I should stick with the 68x118mm BB size mentioned above (and in the Shimano Tech Doc), and I can maybe just wait and see if the existing front mech will work, which I guess it might? If it doesn't, would this front mech work OK? My down tube would appear to be approx 35mm eye-balling a ruler, so it looks like I'd need the 34.9mm version anyway.

 

[RecordAceFromNew]

Thanks again

I've measured my chainline and it's 45mm, so presumably that means I should stick with the 68x118mm BB size mentioned above (and in the Shimano Tech Doc), and I can maybe just wait and see if the existing front mech will work, which I guess it might? If it doesn't, would this front mech work OK? My down tube would appear to be approx 35mm eye-balling a ruler, so it looks like I'd need the 34.9mm version anyway.

Let's hope the Microshift works, and if not if your seat tube is 31.8mm not 34.9mm then the R443 is available for the former. If not you could go with the R453 which is available for 34.9mm seat tubes. If you go with a mtb triple front mech like sram's X5/7/9/0 and that LX they are designed for 50mm chainline, which is not ideal because there is a possibility that you might have issues with set up for the inner front ring if the front mech can't go far enough inboard.

 

[mrmacmusic]

Let's hope the Microshift works, and if not if your seat tube is 31.8mm not 34.9mm then the R443 is available for the former. If not you could go with the R453 which is available for 34.9mm seat tubes. If you go with a mtb triple front mech like sram's X5/7/9/0 and that LX they are designed for 50mm chainline, which is not ideal because there is a possibility that you might have issues with set up for the inner front ring if the front mech can't go far enough inboard.

Cheers again RAFN, those techdocs have been very helpful and I appreciate being steered in the right direction

Having given this some further thought, I'm going to forget trying to retain the Microshift front derailleur, and am also now planning to swap out the SRAM X5 shifters too – since getting the Boardman, I've always had a niggling feeling that I prefer the old 8-speed Shimano shifters that were on my Ridgeback Flight 01... the SRAMs seem to have a longer throw to change gear.

I couldn't pass up the bargains, so I've ordered a 5505 105 triple chainset, and also decided to grab a 5504 105 triple front derailleur as well I'm thinking (hoping) that if I can pick up a set of Shimano R440/441 shifters they will do the trick, even though the technical information "recommends" they're only for R443/453 FD and 4404/4503 chainsets?

On the lookout for a matching 105 rear derailleur now too, and I've started thinking that I should just be saving up these bargain bits'n'bobs so I can set about my first custom build! LBS even has a Genesis Croix de Fer frame/forks in my size for £210.....

 

[RecordAceFromNew]

I couldn't pass up the bargains, so I've ordered a 5505 105 triple chainset, and also decided to grab a 5504 105 triple front derailleur as well I'm thinking (hoping) that if I can pick up a set of Shimano R440/441 shifters they will do the trick, even though the technical information "recommends" they're only for R443/453 FD and 4404/4503 chainsets?

What you will find is those flat bar shifters will be able to drive the 105 road front mech, but the cable will be a little slack for the small ring while tensioned beyond spec for the large ring if you set tension to be just right for the middle ring with the H/L screws setting the range correctly, which is the best one can do under the circumstance.

 

[mrmacmusic]

What you will find is those flat bar shifters will be able to drive the 105 road front mech, but the cable will be a little slack for the small ring while tensioned beyond spec for the large ring if you set tension to be just right for the middle ring with the H/L screws setting the range correctly, which is the best one can do under the circumstance.

Can you help me understand this by explaining why? I – naively it seems – assumed that all Shimano's road triple front derailleurs would move the same amount between rings, so why would the cable be slack in the small chainring and overly tight when on the outer if being operated by a shifter that has road (rather than MTB) pull ratios?

 

[RecordAceFromNew]

Can you help me understand this by explaining why? I – naively it seems – assumed that all Shimano's road triple front derailleurs would move the same amount between rings, so why would the cable be slack in the small chainring and overly tight when on the outer if being operated by a shifter that has road (rather than MTB) pull ratios?

In case there is any misunderstanding, firstly the R440 front shifter does not have road shifter cable pull ratio, and secondly the issue is not about how much the front mech moves between rings. The issue is how much cable is pulled by a road front shifter compared to a mtb front shifter (which happens to be the same as a flat bar road bike front shifter like e.g. the SL-R440) across a triple. The difference is approximately 13.5mm for road vs 19.5mm for flat bar shifters.

To understand my statement earlier, if we start with the premise that cable tension should be set by centering the front mech on the middle ring (which is generally the only sensible thing to do, since the positions of the front mech at the inner and outer rings should and could be set just so by the L and H screws), it follows that when the road front mech arrives at the H screw the flat bar front shifter must still have somewhat more cable to pull before it hits the ratchet than a road shifter would have. Conversely, the cable will be looser than normal when it is released and the front mech is stopped by the L screw.

The thing to remember for the current application, is flat bar road front mechs are designed to work with mtb cable pull but road chainline. For all intent and purpose there is no real difference (except colour ) between flat bar road front shifters and mtb front shifters.

Just for completeness, while e.g. the R440 shifter has some trim-like functionality at the first half of its stroke, ime that part does not pull enough cable for a road mech to move across all 3 rings.