Author Topic: Band-on front mechs: can I sleeve a 31.8 down to a 28.6 (Read 3086 times)

Charlotte · « **on:** 21 July, 2009, 09:39:13 am »

Although it’s on a Mega 9 XT system at the back I need a front road mech for my project touring bike. The chainset’s a 105 flavour 52-40-30. As it’s a standard 27.2mm seatpost, I need a 28.6mm band-on derailleur.

If I was to buy this then I presume I’d be clipping some kind of adapter collar round the seat tube first? So why can’t I save a few quid and buy one of these and find an adaptor collar?

Or is it not that easy?

If it is that easy, where does one buy such a collar? Does anyone have a spare one?

MSeries · « **Reply #1 on:** 21 July, 2009, 09:41:31 am »

You may have my 28.6 Deore ? one for free if you want. Pre aged.

Front mechs don't often slip but having a 'collar' will give two opportunities for it to happen. No idea where you'd get one from.

Ian H · « **Reply #2 on:** 21 July, 2009, 09:52:32 am »

Otherwise make a collar from a piece of 16g soft aluminium. Best to do it in two halves.

StanThomas · « **Reply #3 on:** 21 July, 2009, 09:56:13 am »

Quote from: Charlotte on 21 July, 2009, 09:39:13 am

If it is that easy, where does one buy such a collar?

Yes. It is that easy. Band-on adapters for braze-on mechs are available from most bike stores, including Chain Reaction. It's usually more expensive to buy the adapter plus a braze-on mech but it will work out cheaper in this case.
You can also sleeve down newer Shimano band-on mechs to a smaller tube size with a little plastic insert. And you can sleeve down any band-on mech with some 16-guage aluminium, but it can look a bit shabby.

MSeries · « **Reply #4 on:** 21 July, 2009, 09:56:51 am »

or get a braze on one for £7.50 and a band on braze on adaptor, do they exist for 28.6 diameter tubes ?

Wobbly John · « **Reply #5 on:** 21 July, 2009, 10:04:26 am »

Quote from: Ian H on 21 July, 2009, 09:52:32 am

Otherwise make a collar from a piece of 16g soft aluminium. Best to do it in two halves.

The Wobblebike front mech is sleeved with an ali tube cut to do this - it's not easy to cut the aluminium and avoiding bits wot mark the seat tube.

Got any friendly bike shops that might have one of the plastic adapting collars?

clarion · « **Reply #6 on:** 21 July, 2009, 10:07:55 am »

I'd be a bit wary of using a sleeve for a front mech - especially one for a tourer where it could be changing under considerable strain. A very small movement can make your change go all crappy (sorry about the technical terms

).

oncemore · « **Reply #7 on:** 21 July, 2009, 10:13:26 am »

Never had any problems from "sleeving" a front mech. Best (and cheapest) means of doing so are the "hard" rubber inserts that come with cheap LED lights. Usually a selection of thicknesses - just cut to length. Also do a fair job of protecting the frame/finish.

rafletcher · « **Reply #8 on:** 21 July, 2009, 01:57:20 pm »

Quote from: clarion on 21 July, 2009, 10:07:55 am

I'd be a bit wary of using a sleeve for a front mech - especially one for a tourer where it could be changing under considerable strain. A very small movement can make your change go all crappy (sorry about the technical terms ).

I would have tho opposite opinion

Sleeving is not a problem - I think all of my seat posts are sleeved, and I exert a much gretaer load on them than any changing load on a front mech - which after all I can achieve with one or two fingers riding on the hoods. And you can rack up the bolts - crushing a tube isn't easy.

Zoidburg · « **Reply #9 on:** 21 July, 2009, 03:58:35 pm »

Due to the chuncky nature of most MTB tubes these days most Shimano MTB front mechs come in one oversized band fitting and they supply the plastic collars to fit any smaller diameter tubes.

They work fine and are unlikely to slip.

Charlotte · « **Reply #10 on:** 21 July, 2009, 04:38:50 pm »

Quote from: MSeries on 21 July, 2009, 09:41:31 am

You may have my 28.6 Deore ? one for free if you want. Pre aged.

Tempting, but I need a road mech

alecstilleyedye · « **Reply #11 on:** 21 July, 2009, 09:09:56 pm »

you can actually detach the actual mech from the band on. i had to do that once and it worked fine. if you have an old shimano 28.6mm mech, you may be able to use the band from that with the new mech.

as a consequence of the above, i have one bike that says both tiagra and sora on the front mech!

clarion · « **Reply #12 on:** 21 July, 2009, 09:37:13 pm »

Quote from: Charlotte on 21 July, 2009, 04:38:50 pm

Quote from: MSeries on 21 July, 2009, 09:41:31 am
You may have my 28.6 Deore ? one for free if you want. Pre aged.

Tempting, but I need a road mech

Eh? I'll have to go detach my Deore mechs from my tourer.

rogerzilla · « **Reply #13 on:** 21 July, 2009, 09:42:12 pm »

I have some shims upstairs that came in the leftovers box with the Hewitt, but I suspect they're the wrong size because the Hewitt has a 28.6mm OD seat tube.

Charlotte · « **Reply #14 on:** 21 July, 2009, 09:50:00 pm »

If you (or anyone else) has a spare 28.6 sleeve, I'd be able to buy one of the much cheaper 31.8 mechs from chain reaction in my OP. So I'd be dead grateful

rogerzilla · « **Reply #15 on:** 21 July, 2009, 09:57:06 pm »

It would appear that the Deore FD is 34.9mm clamp, and the shims are for reducing that to 31.8 and 28.6. The ones I have spare are designed for reducing 34.9 to 31.8 so may well work in your situation; the thickness is within 0.1mm and the diameter is probably not critical since they're flexible plastic.

Charlotte · « **Reply #16 on:** 21 July, 2009, 10:02:29 pm »

So you've not got one that can sleeve 31.8mm to my 28.6mm seat tube?

rogerzilla · « **Reply #17 on:** 22 July, 2009, 06:36:46 am »

34.9-31.8 = 3.1

31.8-28.6 = 3.2

Close enough?

gene hunt · « **Reply #18 on:** 22 July, 2009, 07:54:05 am »

This might help: Shimano RSX FD-A417 Front Deraillleur 28.6mm

Shimano Sora FD-3400 Front Derailleur 28.6mm

Just for info and I might be wrong but if your running a 27.2 seatpost then it might be 31.8 you need, I am going by my kinesis and the size of seatclamp I needed.

Charlotte · « **Reply #19 on:** 22 July, 2009, 07:56:04 am »

Quote from: rogerzilla on 22 July, 2009, 06:36:46 am

34.9-31.8 = 3.1

31.8-28.6 = 3.2

Close enough?

Ah - so the one you had came with two sleeves and they're just shims that bend to size?

rogerzilla · « **Reply #20 on:** 22 July, 2009, 06:57:17 pm »

Yes, there are two halves, a bit like a bearing shell for a car engine.

Russell · « **Reply #21 on:** 24 July, 2009, 12:31:08 pm »

I have used plastic plumbing pipe - works a treat!

Author Topic: Band-on front mechs: can I sleeve a 31.8 down to a 28.6 (Read 3086 times)

StanThomas

Zoidburg