bcd and gearing questions, need info please

[DM]

Oh, I see - the 44T is the max that the front mech will take.
Actually, I think you can usually get away with a couple more teeth...

but if you go MUCH larger it's possible that you'll try to slide the front mech up the seat tube a little to clear a larger front ring and find some Muppet bike designer has put a bottle cage mounting bolt on the seat tube - exactly where you want to position the mech.

Ask Gary Fisher how I know this :evil:

Re. Middleburn 5-arm non-compact "ATB" rings - there are loads of sizes:
24T 26T 28T 34T 36T 38T 40T 46T 48T 50T 52T
http://www.middleburn.co.uk/chainrings_mtb.php

The smaller ones will be granny rings obviously, but the middle ring (say 34T upwards? - I can't remember) and outer will share the same 110mm spacing.

 

[guybe]

Oh, I see - the 44T is the max that the front mech will take.
Actually, I think you can usually get away with a couple more teeth...

but if you go MUCH larger it's possible that you'll try to slide the front mech up the seat tube a little to clear a larger front ring and find some Muppet bike designer has put a bottle cage mounting bolt on the seat tube - exactly where you want to position the mech.

Ask Gary Fisher how I know this :evil:

Re. Middleburn 5-arm non-compact "ATB" rings - there are loads of sizes:
24T 26T 28T 34T 36T 38T 40T 46T 48T 50T 52T
http://www.middleburn.co.uk/chainrings_mtb.php

The smaller ones will be granny rings obviously, but the middle ring (say 34T upwards? - I can't remember) and outer will share the same 110mm spacing.

Thanks for that, 44T is missing there, maybe I have to look for another front mech, the one I like to have is SRAM X.7, it only take 44 T max, the lower spec of SRAM X.5 will take 46 T max.

The granny ring is 74mm BCD, I think I will visit LBS tomorrow to discuss about it, cheers DM for your kind help.

 

[dbmtb]

but to answer the question fully, 130mm for road, 135mm for campag road, 144 for track and 70'd campag double, and tiny stuff for 1930's-50's stuff.

If only it were that simple...

But you got the main ones.

 

[billinjah]

im sure middleburn do a 44? mechs say 9 speed as the chain for 9 speed is narrower so the plates are closer together but modern chains are all narrow enough for it not to be an issue.

 

[messiah]

I see your problem... the front mech says it's designed for 34 tooth max... ie for compact drive, wheras your running an old non campact middleburn chainset for which the smallest outer ring you can get is 46 tooth. Hence the two look incompatible.

I've never tried running a CD front mech on a non CD chainset so I can't help with whether it works.

Edit... are XTR front mechs still rated for the non CD rings? They certainly used to be as M950 was non compact drive.

Interesting... if you stick with non CD rings (ie 24, 36, 46) what front mechs can you use? Do you have to use an old one?

I went to compact drive in 1995 and will never go back - I'm a spinner and the lower gearing suits where I live and ride.

 

[cchris2lou]

I have a 43T , 110 for sale if you want . :roll:

 

[guybe]

Thanks everyone for the info/help, after visiting LBS this afternoon, I decided to stick with the orginal Coda cranks that came with my Cannondale, I have ordered a set of 3 chainrings suitable for 9 speed gearing and will be selling the Middleburn cranks now.

Cheers chaps