Asthmatic single speed gearing

hi forum,

i did UTS i promise, but it's an awkward call for advice from those far more bikexperienced than myself.

my girlfriend is asthmatic but is dead set on using my previous generic single speed bike rather than say, going for an old 5-speed town bike. she hates gears but doesn't want to go fixed.
my old SS has 650c wheels and has the stock issue 48/17 gearing which is shit for a SS bike in my opinion.

what do you folks reckon would be a good chainring/cog set-up for a 650c SS that is used mainly for flats/mild hills and wouldn't be too exhaustive to pedal? i'd really appreciate any suggestions. thanks!

It all depends on the person. 48/17 on 650c is about 80" which is pretty high, but some people manage higher.

On a single speed Id say its better to go too low than too high as most of you pedalling will occur uphill with plenty of coasting downhill. If the bike is some old heavy beater with lots of drag, more reason to go even lower. If it is something well setup, light and racey then a bit higher.

60-70" I reckon, depending on her. Swaying to the lower end. But bear in mind a lot of people get more out of breath spinning a low gear rather than heaving a high one. And with a too low gear, top speed will be limited and infuriating, more so than with fixed. Fixed wheels are fun even when you are spinning out, freewheels get awkward.

There's no such answer, you already know the right response... a 3 or 5-speed geared hub.

thanks DFP, sorry to be a moron, but what's an example of a 70" gearing on a 650c SS? the bike is pretty light so it can err to the higher end but yeah, definitely something lower than the current one.

i'd rather stick with the current setup and just change the chainset/cog rather than go for a whole new rear wheel with a hub gear. if i could afford to i would.

Put a 20t cog on the back and it will give you 67.5 which will be a nice gear for a SS.

cool, thank you!

Being an asthmatic doesn't change gearing. If someone is unfit then a bike on 40gi could be too much effort.

It's all about what she's used to and how fit she is.

Rabbit Singlespeed Calculator dude.

This is wrong 48x17 on a 650c wheel is around 68GI with a 23c tyre, that's a perfect gear ratio.

"My bad" if it is, I was using an online calculator too must have been screwing up.

This is wrong 48x17 on a 650c wheel is around 68GI with a 23c tyre, that's a perfect gear ratio.

Perfect for who?

I am fairly fit but 68 is slightly too high for my terrain and my perfect ratio is around 64. For riding slowly and up hills 68 is on the high side for someone who may not want to be pushing too hard.

. Fixed wheels are fun even when you are spinning out, freewheels get awkward.

What, about as awkward as not pedalling like a loon and having a little sit down instead? Sounds well awkward.

I have asthma. 50 + 20. 700c. really nice tyres.(320tpi)

sorted.

Perfect for who?

I am fairly fit but 68 is slightly too high for my terrain and my perfect ratio is around 64. For riding slowly and up hills 68 is on the high side for someone who may not want to be pushing too hard.

Likewise (apart from the fairly fit bit).

67 was too much for my asthma and the 17% gradient found at some point in every direction from home. After a year of bloody mindedness and ventolin I gave in and fitted gears offering 40 - 72 (ish) and use around 63 much of the time.

Being an asthmatic doesn't change gearing. If someone is unfit then a bike on 40gi could be too much effort.

It's all about what she's used to and how fit she is.

This. As a fellow asthmatic I'd say that your cardiovascular fitness is going to be much more of a deciding factor than your gearing. It's worth a chat with her GP or asthma nurse if her practice has one, as they can check your lung capacity and make sure she's controlling her symptoms properly. Then it's just a case of riding as much as possible so your lungs get stronger.

That and knowing your triggers - for me it's cold air, strong winds and climbing but for some people it's warm or humid conditions or pollen. So be prepared and listen to what your body's telling you.

thanks for all the interesting responses. i'll definitely fit a cog with some more teeth and see how that goes.