Bottom Bracket length

steelie600

Is there a way to work out what length BB I need for Ralph?? Its a 68mm english thread fitment. But just come to order an Octalink BB and theres 4 different lengths. If I just get the longest would It cause issues with chain run?? I'll be running 2x10 or possibly 2x9 (not thought that far yet) But defo only 2 at the front.

Your thoughts please

Kev

nicklouse

You need to know what cranks you have then read their manual an that will tell you what ength you need.


Or provide the info and you may get an answer.

steelie600

SR suntour Duro twin coggers, but never thought to check the suntour site. Signature very apt tonight!

I banged my head putting a clutch in a focus today, ive not been right since! LOL

Edited cos im a muppet and put wrong model crank in

steelie600

Cant find any info on suntour site about bb length required

nicklouse

Crank info?

Chunkers1980

Have you got 2 cogs on your crank? In it came with 2 rings originally? Stop banging your head.

steelie600

Here

Same crank but comes without BB, it is an Octalink one just need to know how long it needs to be. OR what I can get away with.

Chunkers1980

Description Included bottom bracket (External bearing system)

nicklouse

steelie600 wrote:

Here

Same crank but comes without BB, it is an Octalink one just need to know how long it needs to be. OR what I can get away with.

Do you have the cranks?

What does it say on them. What is the part number?

Those are not octalink.

steelie600

No not got them yet or even ordered them, HOWEVER I have found the cranks WITH the BB and there is an option on length on that too 114mm and 120mm. Might be worth sending the vendor an email about it. And where ive found the crank the ad says octalink, unless its Isis??? Very similar I do beleive??

All this is because mr Hong kong china man was out of stock of the groupset I wanted, so now im gonna make my own!! LOL

nicklouse

steelie600 wrote:

No not got them yet or even ordered them, HOWEVER I have found the cranks WITH the BB and there is an option on length on that too 114mm and 120mm. Might be worth sending the vendor an email about it. And where ive found the crank the ad says octalink, unless its Isis??? Very similar I do beleive??

All this is because mr Hong kong china man was out of stock of the groupset I wanted, so now im gonna make my own!! LOL

External 68/73 come with one length.

83mm come with what they need. Don't thong there are ant external for 100mm BBs yet.

I would have a read of Parktools again if you are going to continue with this ordering from the east as if you don't know what you need you will not get the right stuff.

Also please give all the info you have with line so that people don't have to double guess you as they will very fast lose interest.

cooldad

I think Nick means links.
Octolink is Shimano, everyone else came up with Isis, the two are incompatible.

steelie600

Nick ive got the handle on the external bit mine is a 68mm BB needed im on about the actual spindle length!!

Like I say there are varying flavours, noww do I get the biggest one which will space the pedals out (I am a big guy after all) or do I get the right one to line up the granny ring with the big wheel on the back?

My thinking cos im running 2 at the front is get the 122mm which will give the chain an easier run to all gears at the back, or is this just folly??

cooldad

If you get an external BB chainset spindle length is fixed.

nicklouse

steelie600 wrote:

Nick ive got the handle on the external bit mine is a 68mm BB needed im on about the actual spindle length!!

as i said it makes no difference.

where and what are they offering?

Link?

nicklouse

steelie600 wrote:

Like I say there are varying flavours, noww do I get the biggest one which will space the pedals out (I am a big guy after all) or do I get the right one to line up the granny ring with the big wheel on the back?

My thinking cos im running 2 at the front is get the 122mm which will give the chain an easier run to all gears at the back, or is this just folly??

you are not making any sense at all.

Chunkers1980

plehtonnactsujuoyelpoepemos

The Rookie

You need to get the right BB width to get the right chainline to suite where your cranks put the chainwheels in relation to the end of the BB, nothing else is relevant or matters, not the bike size, not how overweight you are, nor your inside leg measurement.
If your running a double up front you may consider putting the nominal chainline between the 2 rings (like road doubles) but in my experience most people on doubles on MTB's run in the larger ring all the time unless going into steeper climbs, in which case you want the nominal chainline in line with your outer ring.
Read Sheldon Brown (Nic's sig) and what he has to say about chainline, but your probably looking for 47.5mm.

steelie600

nicklouse wrote:

steelie600 wrote:

Like I say there are varying flavours, noww do I get the biggest one which will space the pedals out (I am a big guy after all) or do I get the right one to line up the granny ring with the big wheel on the back?

My thinking cos im running 2 at the front is get the 122mm which will give the chain an easier run to all gears at the back, or is this just folly??

you are not making any sense at all.

HOW COME??

Right my bb hole in my frame is 68mm weve established that, SO I need an english thread 68mm BB, Right??

NOW there are options to the "spindle length" on the BB's of 110mm, 114mm, 118mm and 122mm < THIS is what has got me confused.

How do I know which one to get?? I will be running a 9 cog cassette initially does this help, and the email from the vendor has said the Crank is Octalink fitment and Shimano shifter compatible, He also has Isis and square fitment and One that are for Sram.

I understand that I need to keep the chain as straight as possible and avoid un necessary angles in its run to prolong its life. AND From what I can fathom out USING a 122mm crank spindle will place both cogs at the front centrally to my rear cassette, thus giving a straighter run for the chain.

Am I correct that this is the right way to do it OR do I just need to line the granny ring up with the 2nd gear on the rear like a normal 3 gear crank??

nicklouse

there are not any spindle lengths offered for 2 piece external cranks.
ISIS does not use those lengths.
Octalink is special and you need to know what cranks to see what chain line they give.

If you want help then give links to exactly what you are looking at. or you may be buying more than once.

so what chain line does the frame need? 47.5 or 50mm?

and which axle gives that chain line with those cranks?

find out and ask the seller as thats all i can offer.

as nothing you have said or linked to actually matches each other.

steelie600

^^^^ thats the info I needed! Cheers nick

This is one ive been looking at
THIS is the other

Second one has a chainline of 50mm as it says in the description

So is there a way of working out the BB size needed?? rear wheel is standard 135mm fitment if that helps any??

The Rookie

Find the data sheets on srsuntour's webby and it will tell you, no-one can second guess it, no point us looking it up when you can just as well.

cooldad

Or just get one of these - simple
http://www.ebay.co.uk/itm/Shimano-Deore ... 43af41c457

steelie600

The Beginner wrote:

Find the data sheets on srsuntour's webby and it will tell you, no-one can second guess it, no point us looking it up when you can just as well.

There isnt any!! Ive already looked!

And CD I think your right, just man up get a Shimano and be done with it!

Chunkers1980

Different doesn't mean good.

It'll match your different frame.

steelie600

Ive just ordered a Deore one with BB, Took the easy route! LOL , Just thought the SR ones were reasonably priced compared to Shimano's. But obviously a lot of grief to get the right one due to not publishing any specs about them.