So chances are you have your bike built up, the chainring and rear sprocket is in place and so is your chain – time to rock’n roll. However you have done the right thing and checked your chainline before packing away all the tools and you’ve just discovered that what you thought was a perfectly adequate chainline is in fact way out.

What to do – just leave it or attempt fixing it? Definitely have a go a trying to minimise the problem, doing nothing could have you either jamming your rear wheel with the chain coming off, you could damage chainring or sprocket or even break the chain itself – so definitely, it’s worth trying to do as much as you can to make sure your chainline front and back are within 1-2 mm of one another. How to measure it – check here

So let’s say the chainline is out – what could you do? Couple of suggestions starting with the easiest one, also handy if you are trying to persuade a bike with 130mm drop out distance to deal with a fixed rear wheel which are narrower than normal road wheels.

Washers -

This is the easier way of doing what is suggested in the Axle Spacing point below, meaning you don’t have to re-dish the wheel afterwards. So the trick here is a simple one and it works better on bikes which are slightly wider between the drop outs than your purist track bike.

Let’s say you have measured your front chainline and it is 46mm and having measured the distance of the inside of the drop out to the centre of the rear sprocket (example 12mm) and knowing what half the distance between the rear drop outs (example 120/2=60mm) is – you take 60mm minus 12mm to arrive at 48mm chainline at the back – now this is 2mm out from what you have on the front and yes, you could get away with it – but adding a simple 2mm washer between the wheel and the dropout on the drive side will bring the distance between the drop out and sprocket to 14mm instead of 12, meaning that your chainline on the back will have gone from 48mm to 46mm. Perfect!

You can use the same trick to space out your rear wheel if your drop outs are a little wider than the wheel itself. Find out the distance between the drop outs when they are not in tension (i.e with the wheel off) and compare with the width of the wheel itself, adding washers for half of that discrepancy on each side, compensating accordingly if the chainline needs adjusting by adding a few more washers on one side versus the other.

Word of caution however – don’t go mad and try to stress the frame excessively by trying to attach wider drop-outs to a narrower fixie rear wheel without any spacing. A mm here and there is not a problem as steel in particular has some innate flex in it and thus small alterations can be achieved using washers, but for big discrepancies and other frame materials you are better off trying some of the other tricks below. London fixie bike have some handy collections of washers if you don’t have these lying about in the bottom of your toolbox, or you can get them from Clerkenwell screws or any other place that sells nuts and bolts.

Sprocket and sprocket spacers

Sprockets aren’t all the same although they may look it – some are wider than others and when swapping between different ones you may just be altering your chainline without realising it. If you have space on your hub, in addition to the lockring you could tweak this by using some spacers – again London fixie bike has these or you could just go back to the point above and use washers to make up for the change.

Moving chainring from outside to inside of cranks -

One way to quickly make up for a 3mm or more discrepancy in the chainline is by altering the front chainline instead. In some cases moving the chainring from being attached to the outside of the crank arm to the inside (there is still a seat on the inside of crank arms too, although not quite as pronounced as on the outside) can solve a seemingly impossible situation. There is no harm in this as long as you make sure to do up your chainring bolts properly. This means the front chainline will have got shorter (measure it again) and this may give you some more tweaking options for the rear wheel.

A new bottom bracket -

Sounds radical, but sometimes you can save yourself a lot of trouble by starting with a bottom bracket suited for fixies in the first place. Modern road bikes having to accomodate compact or triple chainsets will sometimes have to have bottom brackets that have wider spindles, which means that attaching a fixie chainset to them will put your chainline hopelessly out never mind what you do. For replacing the bottom bracket you will need some proper tools, you need to know if its english or italian thread (determines which direction you turn the tools) and you’ll need to get a new bottom bracket which has the same thread and is the proper length (measure the width of the bottom bracket to be sure).

Bottom bracket spacer -

Sometimes you have the opposite problem i.e the bottom bracket seems too narrow and you could really do with it being wider, giving you a better clearance between chainring and chainstay and a longer chainline on the front so there are spacers for this purpose too. I know I’m doing a lot of adverts for London fixie bike, but that’s fine for us UK and European folks – if you are in the States, get on to Sheldon Brown and Harris Cyclery and he’ll be able to sort you out. 

Axle spacing/Re-dishing -

Sheldon talks this through is some detail, and it seems straight forward enough – although I must confess I’ve never tried it myself. Why not? Because occasionally I like swapping my wheels between frames and dishing them specifically to suit one frame could put them out for another one, so there’s why. However, if you are not a bicycle magpie like me (somehow mysteriously accumulating more and more fixies!) this could just be the thing for you.