Flip flop hub and brake adjustment

[andyh2]

What level of tooth differential between freewheels / fixed sprockets will allow gearing swap to be made without having to re-set brakes?

eg if I have 18t freewheel and 16t fixed sprocket and I swap between them am I likely to have to faff about re-aligning brake pads.

[johncharles]

Why would you need to realign anything

[andyh2]

Because the brake mounts are staying still and the wheel is moving backwards or forwards to tension the chain with the change in teeth.

[Si]

I've found that I needed to rest the blocks a tad, when changing by a couple of teeth. But on some bikes I think that you might get away with it - depends on how deep the rims are and how long your pads are, etc.

It's Friday afternoon so my maths is probably not working properly but two teeth = one link = 1 inch divided by top and bottom runs = the wheel moving by half an inch (ish).

[andrew_s]

Adding 2 teeth on a sprocket will move the wheel forwards by 1/4 inch. Move the wheel and look at the rim, and make your own judgement.

Old fashioned forwards facing horizontal dropouts are often at enough of an angle to roughly compensate for the change in rim height.

[andrew_s]

It's Friday afternoon so my maths is probably not working properly but two teeth = one link = 1 inch divided by top and bottom runs = the wheel moving by half an inch (ish).

Only half of the sprocket is in contact with the chain, so 2T = 1/2" of extra chain required, divided between top and bottom runs.

[johncharles]

I have never had to faff about as you put it as the difference has been minimal.

[andyh2]

Thanks guys, sounds like I can add a couple of teeth to my freewheel and run a lower gear than the fixed side.

[Domestique]

Never had an issue with this. I run a 42x18 in the winter then flip over to a 42x16 when the weather is better.

[quiksilver]

If you rode fixed instead of SS then you could do without a conventional back brake anyway.

[andrew_s]

If you rode fixed instead of SS then you could do without a conventional back brake anyway.

Only if you are unwise.
Brakes/cables can fail, and the fixed sprocket is a weak and inadequate subsitute.
Try going to a reasonable hill of 1:7 or thereabouts, and see if you can stop the bike running away just with your legs.

[quiksilver]

If you rode fixed instead of SS then you could do without a conventional back brake anyway.

Only if you are unwise.
Brakes/cables can fail, and the fixed sprocket is a weak and inadequate subsitute.
Try going to a reasonable hill of 1:7 or thereabouts, and see if you can stop the bike running away just with your legs.

Granted, but it would depend on your local geography/ I ride fixed in London but wouldn't back home in Cornwall.

[johncharles]

If you rode fixed instead of SS then you could do without a conventional back brake anyway.

Only if you are unwise.
Brakes/cables can fail, and the fixed sprocket is a weak and inadequate subsitute.
Try going to a reasonable hill of 1:7 or thereabouts, and see if you can stop the bike running away just with your legs.

You don't need a back brake with fixed at all no matter how steep the hill is.