Flip flop hubs?
 

My Touché came with a flip flop hub and 18t and 20t fixed sprockets.

Living in a hilly area at that time, I soon chickened out and put a massive freewheel on one side. *After a while, I removed the sprocket to save weight and reduce clutter.

Later, I moved to a flatter area, put just the 18t fixed sprocket on, shortened the chain, and I've ridden it like that since.

I now realise I over-shortened the chain because I tried recently and can't get it to go round the 20t sprocket. *In due course, I will get a new chain.

So, a question: is 2t difference the maximum? *My bike has track ends ("horizontal drop outs") and runs a rear brake. It seems to me that having a 2t difference will make approximately a 1 link difference to how far forward or back the wheel has to be if I flip (or flop) the hub. *It seems to me intuitively that more than 2t difference would be unworkable. *Any thoughts?

Now a thought: the whole point of a flip flop hub is that you have 2 ratios readily available by turning the wheel. *It would make sense for those ratios to be significantly different, otherwise, changing would be more trouble than it was worth.

There has been much discussion on another thread about whether it is smoother and more efficient (and less wear) to achieve a particular ratio with 2 large cogs rather than 2 small cogs.

However, with small cogs, those 2t difference on the sprocket would make a bigger proportional difference.

Examples:
A20t has 11% more teeth than an 18t.
A 12t has 20% more teeth than a 10t.

*My question:*Those of you who not only own flip flop hubs but actually use them, double fixed, and swapping sides reasonably often, what sort of set up do you recommend and why?

I know on my geared bike, the gears are around 10% apart (very roughly) and I often change 2 gears at a time, and that on my old Sturmey Archer 3 speed, each gear was 33% higher than the one below, which was far too wide, so the ideal gear was always somewhere in the gap!

I run a 17 on one side for general road riding, and interchangeable 14-15-16 on the other side using Miche cogs. In the past I just used the smaller cogs for track, but I might start using the 16 or 15 on the road sometimes since I live in a flatter area now. As a rule, I don't flip my wheel while out on a ride. If I were to do a really long climb and descent fixed, it would probably be worth it to change at the top, but that's not really my thing. Depends on your terrain and riding really.

And you can probably do more than a 2t jump. I think someone calculated that a 1t difference equals like 1/8 movement of axle in the dropouts or something. I regularly switched from 17 to 14 with plenty of room to spare. How big of a jump your bike can do depends on how long your dropouts are.

Flipping the wheel will cause the braking surface to move relative to the brake pads. More than a 1 tooth difference may require adjusting the pads so they don't rub the tire.

I flip between 15 and 16 tooth sprockets and run a 48 ring in the front. This increases/decreases gear ratio by 7%.

The higher geared 15 tooth sprocket is used to help keep up with fast road riders on a flat paceline rides or riding hard on a flat course when I'm fresh. Sometimes after a weekend of hard riding I can't push the 15 and switching to the lower geared 16 tooth sprocket helps me keep cadence up. 7% doesn't sound like much but it helps and I won't hesitate to flip the wheel while out on a ride. For hilly rides it is always the 16 tooth sprocket.

The bottom line for me is adjusting the brakes. Mine are set up so that the pads don't rub the tire and make full contact with the braking surface when using either sprocket. I can flip the wheel on the road and not have to adjust the pads.


-Tim-

Thank you. That is exactly the sort of answer I was looking for.

I recall that when I briefly ran the bike with 18t & 20t on the flip flop, the brakes did not rub when I flipped the wheel. That is an important consideration as I prefer the versatility of 2 brakes.

The second part of my query is adequately answered by the fact that you feel it worthwhile to have only 1t difference and still bother to change mid ride from time to time.

Thanks again.