[Closed] 456 Chainline question

An 118mm axle should give a 50mm chainline and even then chainring clearance is really tight and the stay is likely to get damage if chainsuck occurs (I've got an 853 Inbred with the same bridgeless stays). I'd also be worried about running a middle ring over 34 tooth or an outer over 44.

You could try a longer axle if you can find one but I think that you'll find that Shimano square taper were designed to run on a 47.5mm (113mm) or 50mm (118mm) axle so anything longer would throw out the chainline.

I thought on something like a UN54 a 113mm axle gave a 50mm chainline??

Now im confused

Well I could be wrong, I'm using Octalink cranks, but for those it's a 113mm axle for a 47.5mm chainline and a 118mm for a 50mm one. I thought that back in the days of square taper/Octalink cranks the standard chainline was 47.5mm.

I'm sure that someone will be able to clarify.

Looks like you might be right (sorry for confusing you) [url= http://www.sheldonbrown.com/bbsize.html#deore ]Sheldon Brown[/url] gives the M510 as having a square taper axle and a 47.5/50mm chainline on axle lengths of 110/113. Octalink must be different then.

I daresay that you could use a longer axle but I think that doing so would put the cranks outside of the chainline they're designed to work with and I'd imagine that shifting might suffer.

Built both an inbred with square taper which needed a 113 and a Scandal with Octalink which needed a 118. I bought a 113 octalink first off on the basis of the square taper and it definitely did not work.

Cheers guys - thanks for your help.

Ratadog - how tight was the chainstay clearance with 113 and is a square taper BB fairly simple to fit?

I'm running square taper on my on-one and decided to go with 10mm more axle - can't remember what size though as it was a while ago I fitted it, works out about 5 mm extra each side, lots of chain clearance, no shifting worries, might excellerate the chain wear a bit but I'd rather that than get that crunch of chainsuck, but chains flex quite a bit?

You mention maybe using a 115 or 118 over the 113 recommendrd but that's only another 1mm or 2.5mm diffence each side so not much really?

Quick piccy

[IMG] [/IMG]

Dunno if you make it out in the pic? Plenty of room for the chain on the middle ring which is where I got chainsuck.

Thanks Kojak,cheers for the pic - certainly is lodsa clearance there! i'm just worried about compromising the chainline too much.

If 110 gives a 47.5mm chainline then how come 113 gives 50mm, surely it should be 49? or it is the spindle a mm longer on the drive side?

Either way, has anybody else had any experience using a 115 or 118 to create a longer chainline?

Oh bugger hadn't really considered this and I find the thread quite confusing! Never built a bike from scratch before but I've got a Summer Season on order. I was assuming I could transfer my Deore HTII crankset onto it now I've got an SLX one for my Pitch.

That's what I thought Grumm but for the price of a brand new square taper BB (£13)it wasn't worth transferring the old one over from the other frame.

Ratadog - how tight was the chainstay clearance with 113 and is a square taper BB fairly simple to fit?

It looks like somebody else got here with the answer before I did and good on them. My square taper is now on a standard inbred not a 456, but as far as I remember the clearance is much the same and it is as illustrated above. I have never had any problems with it.

Square taper/cartridge BBs are easy to fit provided you have a bottom bracket tool that fits, you take care to get your lefts and rights sorted and check the threads, and you grease the metal threads as instructed. I tend to use antiseize on the threads rather than grease but except on the Ti bike that is probably overkill.

Essentially, the main body is inserted and screwed in till the flange on the cartridge seats against the frame and you then insert the threaded adaptor in the opposite side (shimano says grease it if it's metal but not if it's plastic) and screw that up until it's tight. Then add crank. If I remember rightly you grease the crank bolts but not the square taper itself or the square socket in the crank as the two parts deform each other slightly to produce a decent interface and if you grease the joint you may be able to get the crank on further than shimano wishes.

Park tools page on bottom bracket insertion is [url= http://www.parktool.com/repair/readhowto.asp?id=94 ]here[/url]
with lots of links to other relevant pages and lots of insistence that the job can only be performed with their own tools - not unsurprisingly

The product page for shimano's square taper BB is [url= http://cycle.shimano-eu.com/publish/content/global_cycle/en/nl/index/products/road/2200/product.-code-BB-UN26.-type-bb_road,fc_road.html ]here[/url]
and a nightmare to find in their website now they see it as less than mainstream. The pdf files top right are the product info and the fitting instructions.

Personally, I have invested in a copy of Zinn and the Art of Mountainbike maintenance which makes all these jobs seem straightforward and remains the book I have open when I am getting my fingers oily.

Hope this helps.

Thanks Ratadog - iv'e always found the Shimano site a bit clunky too!

My mate had to prize his copy of Zinn back out of my hands( albeit a bit more oily then when he gave it to me) after he lent it to me 😆 it is indeed the book to have. I feel a christams present idea coming on.

Yes, ebay always seems devoid of second hand copies of Zinn, which in itself speaks volumes, and even the previous edition seems to go for much the same as the current one with the exception of a couple of optimists trying to sell "new" copies of the previous edition through the Amazon marketplace for more than 60ukp a throw - clearly haven't noticed that Amazon will do the latest edition for less than a quarter of that.

I run a HTII BB on my summer season with 2 drive side spacers (should be one I think) haven't noticed any problems shifting and the extra clearance does seem to help.