Butchering a MTB 22/32/44 Chainset?

[MacB]

I'm trying to work this out, if I bought the above type of chainset could I remove the 32t ring, put the 44t where it was, replace 44t with bashguard and run it as a 22/44 super compact? The front shifter would be friction based, I just can't get my head round the BCD, compatibility, side.

 

[PpPete]

I can't see any reason why not from the BCD point of view - and the rear mech should cope.
But that's an awful long way for the mech to haul the chain up from 22 to 44 teeth. Still, it's an easy change to make and reverse if it doesn't work. Just the thing to play with on wet day in your super tidy garage....

 

[MacB]

cheers Pete, may not even have to do that, Spa Cycles can put together a Touring Chainset with a 24/42 or 44 or 46 config for me, using a triple but leaving off the outer. A 24/46 and 13-25 cassette make a very nice combination, 26-50GI on the inner and 50-96GI on the outer. Just got to make sure that I can get the FD low enough on the seatpost to accomodate the 24t.

 

[jimboalee]

cheers Pete, may not even have to do that, Spa Cycles can put together a Touring Chainset with a 24/42 or 44 or 46 config for me, using a triple but leaving off the outer. A 24/46 and 13-25 cassette make a very nice combination, 26-50GI on the inner and 50-96GI on the outer. Just got to make sure that I can get the FD low enough on the seatpost to accomodate the 24t.

If you're thinking of a 24/46 and intend to only use the 24 on really steep hills, consider junking the front mech completely and manually use a plastic tyre lever to derail the chain at the bottom of the really steep hill.

At the top of the hill, stop and put the chain back on the 46 ring.

 

[GrumpyGregry]

in answer to the OP - yes I've done it, on a home made MTB based trekking bike. The shifting quality was grim. So I ditched the front shifter and used fingers instead. Very effective given you know well in advance when the such shifts will be required.

If Spa can do it that is the way I'd go these days.

What bars have you got on the Giant btw?

 

[jimboalee]

The plastic tyre lever has a bulldog clip taped to it and it lives on your map holder.

 

[GrumpyGregry]

The plastic tyre lever has a bulldog clip taped to it and it lives on your map holder.

eventually I made a hook from an old ali coat changer. the tyre leaver idea never occurred to me. Doh!

 

[MacB]

They're the On-One Midge bars Greg and I'm very happy with them. The 96 miles on Saturday were their longest test and no aches or pains apart from the palms of my hands. That was from the gel pads on my MTB mitts not really working with the hoods/corner position. I've got some unpadded ones on order, the bars have foam tubing under the bar tape anyway.

I don't think the shift would be a problem with a friction lever but my concern is over FD position. I can get the height right it's the throw that bothers me. The FD would normally lift in two jumps of 10-12 teeth but I'd be asking it to lift 18-22 teeth in one go. While it will do this will it also want to move too far to the right, for a middle ring position, before attaining the necessary height? sort of like an overshift or will it just scrunch its way up the side of the larger middle ring until it plops into place? It may require a bash guard, chain retention device, to avoid throwing the chain. I really don't mind an agricultural front shift as it would be rarely used.

Sheldon ran 51/28 and 50/28 setups, without a manual front shift, so it must be doable. Will pop along to discuss with my friendly bike mechanic tomorrow(I think I drive him almost as mad as I do you lot).

 

[GrumpyGregry]

They're the On-One Midge bars Greg and I'm very happy with them. The 96 miles on Saturday were their longest test and no aches or pains apart from the palms of my hands. That was from the gel pads on my MTB mitts not really working with the hoods/corner position. I've got some unpadded ones on order, the bars have foam tubing under the bar tape anyway.

I don't think the shift would be a problem with a friction lever but my concern is over FD position. I can get the height right it's the throw that bothers me. The FD would normally lift in two jumps of 10-12 teeth but I'd be asking it to lift 18-22 teeth in one go. While it will do this will it also want to move too far to the right, for a middle ring position, before attaining the necessary height? sort of like an overshift or will it just scrunch its way up the side of the larger middle ring until it plops into place? It may require a bash guard, chain retention device, to avoid throwing the chain. I really don't mind an agricultural front shift as it would be rarely used.

Sheldon ran 51/28 and 50/28 setups, without a manual front shift, so it must be doable. Will pop along to discuss with my friendly bike mechanic tomorrow(I think I drive him almost as mad as I do you lot).

Thought they might be, they looked gorgeous and v comfy. Am tossing up between them and some old skool style WTB Mountain bars to finish a singlespeed retro MTB shopping bike.

I was using Shimano chainrings and the pins and ramps used to drag the chain up onto the big (middle) ring after a few noisy clanky turns and a fair bit of pressure/overshifting. I set it so it just cleared the teeth of the big ring. I was using gripshift which actually made it easier imo as it was like a friction lever with 'clicks' in effect.. There was as knack to it though. Mind you were are talking over 10 years ago! One day the cable to the FD snapped, at the shifter. I took the FD off and did the rest of the trip 'manually' In the end I realised I was nearly always stopped when I needed to change anyway, either at the bottom or the top of a hill so never got around to putting it back on. It was that way when I sold it!

 

[PpPete]

They're the On-One Midge bars Greg and I'm very happy with them. The 96 miles on Saturday were their longest test and no aches or pains apart from the palms of my hands. That was from the gel pads on my MTB mitts not really working with the hoods/corner position. I've got some unpadded ones on order, the bars have foam tubing under the bar tape anyway.

I don't think the shift would be a problem with a friction lever but my concern is over FD position. I can get the height right it's the throw that bothers me. The FD would normally lift in two jumps of 10-12 teeth but I'd be asking it to lift 18-22 teeth in one go. While it will do this will it also want to move too far to the right, for a middle ring position, before attaining the necessary height? sort of like an overshift or will it just scrunch its way up the side of the larger middle ring until it plops into place? It may require a bash guard, chain retention device, to avoid throwing the chain. I really don't mind an agricultural front shift as it would be rarely used.

Sheldon ran 51/28 and 50/28 setups, without a manual front shift, so it must be doable. Will pop along to discuss with my friendly bike mechanic tomorrow(I think I drive him almost as mad as I do you lot).

Can sort of see what you are thinking - but you can prevent it moving too far left or right with the limit screws. The question is rather the other way around- having set the limit screws do you still have enough vertical motion of the cage?
I imagine that a FD designed for a compact will move with a "steeper" angle than one designed for a triple, so that may help.

 

[MacB]

Ok, well I've done some further reading and a bit of measuring and picture taking. I'm going to try this on an existing bike/chainset first. The Giant has a 30/42/52 as shown here:-

this picture shows that, though the FD is braze on it could slide about 3-5mm lower in the slot if need be:-

this final picture shows the gap, approx 18mm, between chain and bottom of FD in 30t ring and the 3rd smallest cog, I wouldn't intend ever going this far in real life. Obviously as you move to easier gears the cog gets bigger so the chain lifts:-

The BCD on this chainset is 130/74 and I can get a 24t 74 bcd chainring for £7. My understanding is that every tooth equates to a 2mm height differential. Certainly measuring between the 30/42/52 bears this out, so a 24t would be 6t difference or a lowering of the chain by 12mm.

Theoretically this could work with no other alterations but, if I had to lower the FD, then I may have to alter the big ring. Either a smaller chainring, an old worn out one would do, or a bashguard. There's no shortage of space to chainstays etc so no risk of running foul if I had to lower the FD. This would mean a climb of 18t between rings, this is only 2t more than a compact so I reckon I'll give it a go, will report back