Singlespeed Chain Alignment

TheJackal

I'm combining the small chainring (29T) off a double Chainset with a Gusset Double Six SS Sprocket (17T) for use on dedicated Single speed wheels (Easton One SS). The BB is a BSA 73mm and I've not used any spacers.

The problem is that the sprocket is a lot wider than a normal sprocket so as not to dig into the freehub BUT when trying to align it with the chainring, to get a straight chainline, the chainring seems to require that the sprocket is as far over to towards the spokes as possible.

As the sprocket is offset and can only go on to the freehub in one direction, I cannot get the chain aligned, as the sprocket is too far away from the spokes.

Have I done something wrong? Or, could I use spacers to move the chainring over? Or, should I just go for a normal thin sprocket that will allow me to place it as near to the spokes as possible?

nicklouse

The sprocket can be used two ways to give two different rear chain lines.

So flip it.

What cranks? Most need a spacer on a 73mm BB.

More info needed.

stubs

Chain shouldnt be anywhere near the spokes. If you have everything right chainline wise the cog should be roughly in the middle of a splined freehub. Measure from the centre of the seat tube to the chainring this should be approx 50mm if its out you need to play with bottom bracket spacers to get it within +2 or -2mm.

This might help http://www.charliethebikemonger.com/faqs-4-w.asp

nicklouse

stubs wrote:

Chain shouldnt be anywhere near the spokes. If you have everything right chainline wise the cog should be roughly in the middle of a splined freehub. Measure from the centre of the seat tube to the chainring this should be approx 50mm if its out you need to play with bottom bracket spacers to get it within +2 or -2mm.

This might help http://www.charliethebikemonger.com/faqs-4-w.asp

Did you note the wheels the OP has? Yes the sprocket will be closer to the spokes than the middle.

TheJackal

The sprocket cannot be flipped. It is designed to go on one way with cogs on the outside, as far as I can see.

Cranks are ControlTech Double Play with their proprietary BB which is designed to run as 68mm but can be run as 73mm without the spacers.

Because the Hubs are SS specific it would seem that the spokes are a lot further over towards the dropout. If it were a "normal" freehub, the sprocket would have enough room to be "spacer-ed" into place.

nicklouse

it flips.

unless there is something on the hub stopping it.

http://www.gussetbikes.com/products-inf ... id=CSGU6ON

Built-in offset optimises chainline.

TheJackal

I've tried and tried again but the splines don't align when flipped.

It's one of these... http://www.gussetbikes.com/products-inf ... id=CSGU612

TheJackal

The narrowest spline on HG freehubs has a two different sized gaps next to it. Flip the sprocket and the narrower gap fits over the wider gap and vice versa.

nicklouse

ok i have in front of me one brand new 66er cog in plastic bag and one shimano free body.

and you are right.

the other ones i have fitted must have been different.

not sure way they are not flipable as it would make life easier.



ok back to your issue.

is the body alloy or steel. as the cranks have a chain line of 47.5mm (48) rather than the more common 50mm you might need to use a non shoulderd cog.

which fitting type is the BB? GXP or shimano type? been a while since i removed the last lot of controltec external cups.

TheJackal

The BB is Shimano HT11-type and therefore threaded. I've not used any spacers as the ControlTech instructions only mention a 68mm BB and the Tranny BB is 73mm. The BB comes with 3 X 2.5mm spacers 2 X 1mm spacers and 1 x 0.3mm spacer but I've not used any on the drive side.

I'm not sure about the freehub (?) body. The hub is an Easton XC One SS.

nicklouse

ok as it is a shimano type you will need one spacer on the drive side with a 73mm BB,

very little info from controltec.

this will help the chailine a bit.

see how that goes.

TheJackal

I'll try one spacer but I reckon it's going to need at least 2 x 2.5mm spacers.

If I put any more would it cause any damage, Nick?

Chunkers1980

I'd say you'll likely not have enough thread.

nicklouse

TheJackal wrote:

I'll try one spacer but I reckon it's going to need at least 2 x 2.5mm spacers.

If I put any more would it cause any damage, Nick?

I can't remember what the control tec cranks are like but you will be fine with the drive side cup but it comes down to how things work on the non drive side with the arm fitting....
I have run 5mm spacers on the drive side of a 73mm bb with a shimano crankset.

I would start off with one and see how it goes.

TheJackal

OK will do.

i suppose the only problem is whether there is enough thread to stop any play, right?

The ControlTech instructions (!!!) if they can be called that, state that, for a 68mm BB, install 2 on the drive side and 1 on the left side and then check for play. As this is a 73mm shell, I just omitted the spacers all together.

I'd prefer to use the Gusset cog as the base is wider but can't believe that they're not flippable!

nicklouse

That is standard shimano type spacer con fig. So you should have one on the drive.

Might have to drop Maz a mail about that.

TheJackal

I've just bunged 5mm on and the chainline is bob on with no lateral play. Although, when "hand" tight, the cranks won't move freely, so I've slackened the bolt off to allow the cranks to rotate relatively freely. There still isn't any lateral play, when I do this. So...?

nicklouse

I would also be tempted to take a file to big "tooth" on the cog do you can flip it.

How is the arm held on? Is it just one bolt on the end ( I think it is) or is it preload and two pinch bolts?

TheJackal

One bolt on the end and then splined. Seems very tight to tighten and much less play than on Hollowtechs I've previously fitted. Would hate to ruin the crank, mind.

nicklouse

If it is one bolt then you can not run 5mm of spacers on the 73mm bb as you will crush the bearings.

One 2.5mm spacer only to give a total BB width of 75mm. This should allow the cranks to bottom out and preload the bearings. It is like the Raceface set up.

TheJackal

OK. I'll return the cogs and get something without a shoulder. A pity, mind.

TheJackal

nicklouse wrote:

If it is one bolt then you can not run 5mm of spacers on the 73mm bb as you will crush the bearings.

I haven't just gone and crushed the bearings have I? :oops:

nicklouse

you should be OK.

TheJackal

Nick,

I dremmeled the offending spline and have managed to flip the Double Six cog.

Using the "67.5mm skewer" method, the chainline now seems bob on.

One question though. How should the cranks feel in terms of rotation? They certainly don't flop and feel quite tight. There also seems to be a slight noise! I only ask as I'm a bit wary that I may have knackered the bearings. :oops:

nicklouse

if the chain line is out there will be a noise.

if you are talking about free spinning? then external bearing cranks dont spin that easily but tzhey are fine.

TheJackal

Thanks. No, the noise is slight and not the usual chain noise. It seems to come from the BB.

How would it feel/sound if I'd knackered the bearings?

nicklouse

just had to read back through as i could not remember what had happened.


remember when you used to over tighten the headset and it would end up with index steering. ( brinneled )

but i would just use it as it may just go if it was just compacted grease.