Dishing flip flop or spacers behind sprockets?

I'm building a wheel on a fixed / free flip-flop hub. One side will be a Shimano freewheel and the other a Surley / Andel fixed sprocket.

Looking at Sheldon Browns table for those sprockets, I'm going to have a few mm difference between the two side.

from http://www.sheldonbrown.com/chainline.html

Chainline
(From Shoulder) for 3/32 sprockets
Surly = 6.4mm
Shimano = 7.89mm

so that's 1.49 mm difference.

Trying to sort chainline so that it is good for both sides and havea few options.

** Option one* is to move the axle and dish the wheel very slightly so it sits centre in the frame and also places the sprockets same distance from the lockring nuts, hopefully with a good chainline to match chainring, or I'll need to adjust chainring too. This seems quite a convoluted method and if I then change either sprocket fro another brand with a different shoulder I have to go through the process of redishing again to line eveything up.

**** Option two*** is to put 1.49mm or near as possible of spacers behind the Surly side and then adjust front chainring out to keep in line. Only concern about this is moving the sprocket away from the centre of the hub might bring it too near or over the edge of the thread? Is this normal. This solution does seem simpler though and more easily adjustable in the future for swapping sprockets.

• Option three*** is to just not bother with trying to get them the same and set it all up for perfect chainline for the fixed side (which will need tighter chain and therefore benefit from being perfect more) and run the freewheel side 1.49mm out of line.
  
  

**** Option four*** is to set it up so they're both 0.75mm out, and go for something in the middle. Doesn't sound great through as it wil never be perfect.

Hoping that those figures on Sheldon's site are correct too as looking at the hub with the Shimano it actully looks like it's going to sit more like 4mm further out, which would bring the Surly sprocket option 2 even nearer or further over the fixed thread edge to match up.

Going for 3/32 chain as I may need it to be more forgiving.

Anyone been through this, have advice and experience or any other solution?

option 2.
1.5mm of cog spacers should'nt be a problem (you can use BB spacers), just make sure the lockring still threads on nicely.
http://www.velosolo.co.uk/shoptrack.html

(ED: I've got 2x1mm spacers on my fixed, and the lockring still does enough turns)

Also. 0.75mm out on chainline is chuff all.

option 2.
1.5mm of cog spacers should'nt be a problem (you can use BB spacers), just make sure the lockring still threads on nicely.
http://www.velosolo.co.uk/shoptrack.html

(ED: I've got 2x1mm spacers on my fixed, and the lockring still does enough turns)

Don't forget the 0.01mm inverse spacer to take it down to 1.49mm

Don't forget the 0.01mm inverse spacer to take it down to 1.49mm

Was planning on using the three 0.004mm ones I've got and then adding an inverse shimmed 0.0002mm spacer to counterset it slightly to the west.

Also. 0.75mm out on chainline is chuff all.

Thanks that's what I'm hoping, that it's only 0.75mm and Sheldon's table is correct.

option 2.
1.5mm of cog spacers should'nt be a problem (you can use BB spacers), just make sure the lockring still threads on nicely.
http://www.velosolo.co.uk/shoptrack.html

(ED: I've got 2x1mm spacers on my fixed, and the lockring still does enough turns)

Good to know.

I've got a few BB spacers from the random boxes in the workshop just in case.

Thanks all for replies.

run 1/8th chain on 3/32 ring and sprockets to give you a bit of leeway

Thanks that's what I'm hoping, that it's only 0.75mm and Sheldon's table is correct.

Are you doubting Sheldon?

Option 5:
Stop worrying, and

Option 5:
Stop worrying, and

mmmm

Are you doubting Sheldon?

I wouldn't dare. Only being carefull as some of those measurements are emailed in from other people.

I've got a few BB spacers from the random boxes in the workshop just in case.

In that case just play with spacers untill things line-up.

I find it tricky to measure chainline (just how do you decide on the centre of the hub to say 0.5mm accuracy?). So I used a spirit level.

With the bike hanging from a front wheel hook on the wall, I made sure the top tube was 100% perpendicular with good old planet earth. I then checked the chain, adding or removing spacers, untill toptube and chain were as paralell as possible. Probably a stupid way of doing it, but it worked for me.

I
I find it tricky to measure chainline (just how do you decide on the centre of the hub to say 0.5mm accuracy?).

You don't find the centre, you take the whole width and halve it then use it with other measured dimensions to work out where your chainline should be / is. Then you can measure from the rear dropout or locknuts to the sprocket.

Vernier Caliper, ruler, knowing the dimensions of the hub you have from manufacturers info and working it out with the rear droput spacing all help.

http://www.sheldonbrown.com/chainline.html

A EF: Perhaps an uninformed / naive question, but are you sure that the distance from centre to shoulder is the same on the freewheel side of the hub as it is on the fixed side? By centre, I mean exactly half way between the locknuts, not half way between the flanges.

Example:

• If centre to shoulder on fixed side is 35.6, your chainline will be 35.6 + 6.4 = 42mm
  
• If centre to shoulder on freewheel side is 34.11, your chainline will be 34.11 + 7.89 = 42mm
  
  

Now, I am sure it won't work out this perfectly, but if centre to shoulder measurement is different on both sides, it will impact how much spacing you need behind the Surly / Andel.

Perhaps I am being a bit dim (quite possible) and missing the point. If so, please ignore.

A EF: Perhaps an uninformed / naive question, but are you sure that the distance from centre to shoulder is the same on the freewheel side of the hub as it is on the fixed side? By centre, I mean exactly half way between the locknuts, not half way between the flanges.

Example:

• If centre to shoulder on fixed side is 35.6, your chainline will be 35.6 + 6.4 = 42mm
  
• If centre to shoulder on freewheel side is 34.11, your chainline will be 34.11 + 7.89 = 42mm
  
  

Now, I am sure it won't work out this perfectly, but if centre to shoulder measurement is different on both sides, it will impact how much spacing you need behind the Surly / Andel.

Perhaps I am being a bit dim (quite possible) and missing the point. If so, please ignore.

I can see your reasoning, but the distance from centre of hub (as you define it) to the start of the threads for freewheel/cog are (as far as I'm aware) always equal. Especially if you buy a fixed/fixed hub, which is usually the best idea.

A EF: Perhaps an uninformed / naive question, but are you sure that the distance from centre to shoulder is the same on the freewheel side of the hub as it is on the fixed side? By centre, I mean exactly half way between the locknuts, not half way between the flanges.

Example:

• If centre to shoulder on fixed side is 35.6, your chainline will be 35.6 + 6.4 = 42mm
  
• If centre to shoulder on freewheel side is 34.11, your chainline will be 34.11 + 7.89 = 42mm
  
  

Now, I am sure it won't work out this perfectly, but if centre to shoulder measurement is different on both sides, it will impact how much spacing you need behind the Surly / Andel.

Perhaps I am being a bit dim (quite possible) and missing the point. If so, please ignore.

Not naive at all.

This had crossed my mind and I am hoping that it is the case. If the manufacturers take into account that freewheel sprockets are always slightly wider you'd hope they'd allow a little more space on the freewheel side to keep everything equal and balanced.

I'll find out when I put it together I guess and will report back. (not got hub in front of me and waiting on sprocket delivery).