I'm trying to get my flip-flop to be the exact distance from my spokes to my cog so that when I ride in either fixed or freewheel, it is super smooth. It looks like i'm going to have to put spacers on before I thread on the fixed cog. Is this uncommon? Will it strip my hub?

Thanks!

Are you talking about the freewheel side? You could probably use a bottom bracket lockring, but I don't see how any flip-flop hub wouldn't already be lined up perfectly with a chainline, unless both sides are off.

There are no such things as spacers for fixed cogs.

The Freewheel is sort of fat. The Cog is pretty flat. The distance from the cog to spokes is like 16mm with the freewheel and 14 with the fixed cog. So basically, is it uncommon to add spacers before i thread on the fixed to make up for the 2mm difference.

Thanks.

I haven't ever had to do it. Haven't heard of anyone else having to either. The only thing that I can think of is maybe you put the cog on backwards.

Thats what i was thinking.

You can use bottom bracket spacers, however I don't know if I'd recommend it since it might not leave you with enough threading for your lockring.

If you need a spacer to adjust chain alignment, you can get bottom bracket spacers (not lockrings) in 1/2, 1, 2, and 4 mm thicknesses. They're cheap (about a dollar) and aluminum.

The problem with using a spacer there is that any other wheel will also need a spacer, plus the spacer acts like a washer -- it creates "slipperiness" between the cog and the face of the hub (not the threading but the perpendicular surface that the cog butts against). This makes it easier to disengage the cog. Plus, as Nullius said, you can run out of lockring threading.

I'd actually recommend moving the bottom bracket slightly if the cog needs spacing. If you are spacing the cog, then your bottom bracket needs to move slightly to the left. There are bottom brackets that can be adjusted in both directions but if you have one that simply cranks down tight on the right side, you'll want to ask your local shop to face the bottom bracket shell slightly.

Does your cog have good alignment? Noise can be a matter of cog shape and quality, not just alignment. If you're using a Surly cog you will have more noise. I like EAI and Dura Ace cogs the best, but even among EAI cogs there's a lot of difference in noise and smoothness between the standard black one and the stainless one with the polished edges. Check for chain alignment on the cog. Let that be the deciding factor on how you space anything. And be sure you're using a standard dimension cog (like a Dura Ace, EAI, or Phil cog).

There are a number of single-speed freewheels out there that have different spacing from cogs. That may be one source of your problem.

In short, you could be having problems with an inexpensive cog, a non-standard spaced freewheel, or simply be hearing noise because of the cog shape rather than real mis-alignment. Two millimeters of chain alignment is rather hard to detect and can create a bit of a difference in noise and smoothness but only if it makes the difference between being on the edge or simply out of alignment. Your measurement from the flange to the cog may not really be that relevant to actual performance.

Excellent! I have a Dura Ace cog. I'll let that dictact my ride and get rid of my crappy freewheel. Any recommendations?

"flange to the cog".. thats exactly what i meant!! and not spokes-to-cog... haha

Some flip-flop hubs have the freewheel side threads cut in deeper towards the flange to retain a 42mm chainline.

a 2mm deviation in chainline is nothing to worry about.

check the dish on your wheel, that could be the issue

how can wheel dish affect chainline?

it can't

****, im dumb, nevermind

make the fixed cog happy, 2mm off for a freewheel is nothing. Also, check your frame and dropout alignment before you start getting excited about how perfect your chainline is in theory.

Just adjust your bb like a normal person. I have never heard of somebody walking in their lbs and saying" I need spacers" and the clerk saying "right here man" I cannot condone the use od these if they do exsist. You need to be torqued down on the hub, anything else is a washer in the way. But what do I know?

Most people don't have adjustable BB's. These spacers are available because they are the same diameter as BB spacers, which are often needed for adjusting chainline the other direction (outboard at the BB). Putting them under a fixed cog isn't the greatest idea, but it's necessary for some applications and as long as you don't skid and all of that it's fine.