Chainline adjustment

ContrelaMontre

Alright guys I'm nearly there, but I've got one final hurdle to overcome - Chainline!

I've put everything together and have come out with a 3mm difference in chainline - 41mm at the front 44 at the back. This is resulting in a slight noise when I turn the pedals so I want to get it sorted. I've got a Zenith double fixed hub with a Dura Ace sprocket at the back and am using the inner ring of the original Raleigh chainset and original BB* up front - using a 3/32 chain.

So what should I do?

Sheldon Brown (RIP) in his Chainline article says, "you can usually add a spacer washer between the right-side bottom bracket mounting ring (or cup) and the bottom bracket shell of the frame." - Any idea how to do this? Could someone explain or direct me to somewhere that actually shows how?

Any other suggestions or solutions?


*I don't actually know what type of BB it is as I don't know how to identify the differences. Except I'm pretty certain it is English threaded. It's an old Raleigh - circa 1982.

SamWise72

If it's too narrow at the front, why don't you move the ring to the outside of the spider?

ContrelaMontre

SamWise72 wrote:

If it's too narrow at the front, why don't you move the ring to the outside of the spider?

Because some clever engineer decided to make the outer ring integral - i.e. I can't take it off.

I have been thinking about whether I can get my hands on some 165 cranks anywhere that I can attach the inner ring to but I'm trying to find the cheapest solution at present.

If I put shorter crank bolts on, which would move the inner ring closer to the outer, do you think that would work? The chain'll probably catch on the outer ring then though wouldn't it.

meagain

3mm is not much, really!
I don't know the hub, but can you not move it over a litle via spacers and slightly redish?
If you can shift the inner front nearer to the outer could always cut down the latter so that doesn't foul the chain - but your gearing is going to change significantly.
Failing all that, I'd just use a 1/8th chain and accept a little noise!.

PS Is it a cup and cone b/b axle? If so the axle might protrude a different amount each side - tho' admittedly the longer flat is probably already on the drive side.

ContrelaMontre

meagain wrote:

3mm is not much, really!
I don't know the hub, but can you not move it over a litle via spacers and slightly redish?
If you can shift the inner front nearer to the outer could always cut down the latter so that doesn't foul the chain - but your gearing is going to change significantly.

Why would my gearing change? Not sure I understand your point

PS Is it a cup and cone b/b axle? If so the axle might protrude a different amount each side - tho' admittedly the longer flat is probably already on the drive side.

Yeah I think it's cup and cone and solid threaded axle. But it's a double fixed hub so I'd rather not redish the wheel unless I can't find another solution.

meagain

Sorry - assumed that the inner is smaller.

ContrelaMontre

meagain wrote:

Sorry - assumed that the inner is smaller.

Oh do you mean use the outer ring instead? That would significantly change my gearing!

I'm going to look at shorter stack bolts as an option though as provided the clearance to the outer ring is sufficient this might be the difference I'm after.

SamWise72

Short stack bolts won't work - they're designed to let you fit one chainring instead of two. The position of the inner chainring is limited by the fact that it physically hits the spider - nothing you can do will make it move further outboard, but washers/spacers could be used to move it further inboard.

If you buy short-stack bolts, all you'll have is bolts that are too short. If it were me, I'd drop a tenner on an old bike from ebay just for the cranks. That's gonna be your cheapest option. Anything with square taper cranks where it looks as though both rings are removable.

Other options are - respace the hub (might not need to redish if you're not running a rear brake), get a different BB (shorter axle) get a bb where both cups move, so you can hack the chainline (either the almost extinct Shimano UN72, or a Phil Wood, for twice what your bike cost so far).

Sorry to be the bearer of bad tidings, but I'd hate to see you waste money on chainring bolts that aren't going to help.

ContrelaMontre

SamWise72 wrote:

Short stack bolts won't work - they're designed to let you fit one chainring instead of two. The position of the inner chainring is limited by the fact that it physically hits the spider - nothing you can do will make it move further outboard, but washers/spacers could be used to move it further inboard.

If you buy short-stack bolts, all you'll have is bolts that are too short. If it were me, I'd drop a tenner on an old bike from ebay just for the cranks. That's gonna be your cheapest option. Anything with square taper cranks where it looks as though both rings are removable.

Other options are - respace the hub (might not need to redish if you're not running a rear brake), get a different BB (shorter axle) get a bb where both cups move, so you can hack the chainline (either the almost extinct Shimano UN72, or a Phil Wood, for twice what your bike cost so far).

Sorry to be the bearer of bad tidings, but I'd hate to see you waste money on chainring bolts that aren't going to help.

That's cool. I have got an old chainset anyway that I'm going to see if it fits. I hadn't planned on using it as it's 170mm arms and I'd prefer the extra clearance but we'll see. I don't know if it matches the BB though - I'll have a look though.

SamWise72

Only one way to find out! If it's square taper, it'll 99.9% fit - there are two standards, but Sheldon said in practice, he always found them interchangeable, so you should be fine. Of course, chainline differs from crankset to crankset (a little) so who knows? TBH, 5mm of clearance makes little difference - I've got bikes on 165 and 170, and I've never had pedal strike with either. Pics?

ContrelaMontre

SamWise72 wrote:

Pics?

I'll try and sort some out at the weekend if I can. I'll need to arrange some sort of image hosting account I guess.

Pete Beer

I find 165 cranks usually miss curb edges if you are forced into the gutter. I've also got the rear wheel off the ground cornering with 170's.

SamWise72

ContrelaMontre wrote:

SamWise72 wrote:

Pics?

I'll try and sort some out at the weekend if I can. I'll need to arrange some sort of image hosting account I guess.

Photobucket is your friend. Free, and totally easy to use.