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Hi there,
I'm putting together a singlespeed bike for a flat winter commute using a mountain bike with slick tyres. The ratio I'll need to run is completely confuddling my brain - I know for general off road use peeps round here recommend 32:16 or 32:18 depending on how hard are you are.
What'd be good for road use that wont kill my legs? As a guide on my road bike I average 17-18mph on the way to work, I want something I'll be able to pedal up the one or two hills but not so low I won't the able to pedal at 25mph without my legs becoming blurred.
I've had a look on Sheldon Brown but he's confused me!
I ride fixed on a road bike 48:17 for my 8 mile commute along the Tyne Valley. High enough to get a decent speed on the flat and not be too spinny on the bigger descents, but I can also crank it up the couple of short sharp climbs and get over the longer gradual ones too.
Hope that helps...
I'm just building one up at the moment, it's my first foray into SS. I've been running my geared bike in various ratios to see what works best for my commute, and I've ended deciding on a 38:14. It's for an MTB with slicks to be used on a fairly flat commute, so fairly similar requirement to yours.
Btw, Charlie the BikeMongers website has quite a good table comparing the various chainring / sprocket sizes and the resultant ratios, saves a bit of messing around with the calculator
cool - thanks for that, dicky, it's my first foray as well as I've been using my road bike with bigger wheels etc.. i've not got anything to compare it to.
That Charlie the bikmongers site is horrible - this was supposed to be a cheapy cheap build I can see it being quite pricey & pimpy now...
I've been using my road bike with bigger wheels
Use Sheldon's gear calculator to work out what gear inches you've been running with that tyre/wheel combo, then put in the new wheel/tyre size into the calculator along with a range of chainring/sprocket sizes and choose one that's close.
I found 42/16 the best ratio for my fairly flat 8 mile commute in North London, but it was a bit of a struggle on the few occasions i pointed it up any big (ish) hills.
48:15 on my 700c fixie - 9 mile commute which is pretty flat (just one half mile hill on the way home). It is a big gear though and a 48:17 is probably sensible unless you have legs completely disproportionate to your bantam weight top half (like me).
Hey PJ,
I built a mtb with slicks and 36:18 swapped to a 32:16 but still pedalling it out. Went 44:18 but I have some steep but fast hills.
Maybe useful for uphill stomps but I'd try a 42:16 or 18 depending on your hills and you sound in good shape for 18mpg average on your roadbike.
Just look after your knees. (I've chucked my gears back on 11-34 36/44 as I carry on shopping on the back too but some days no load and it's great to choose a ratio). 😀
double post
I used to use 42:16 then got used to it and went upto 42:14 on a 26" bike with 1.95" tyres on.
No massive hills although it is a 2-3 mile climb after I cross over the Tyne.
The steepest hill is this one
[url= http://maps.google.co.uk/maps?f=q&source=s_q&hl=en&geocode=&q=cut+bank+newcastle&sll=54.970298,-1.609883&sspn=0.011799,0.027595&ie=UTF8&ll=54.972811,-1.591172&spn=0.011799,0.027595&t=p&z=15&iwloc=A&layer=c&cbll=54.972905,-1.591074&panoid=VR9xXFkTVM7X5psIRtdU2Q&cbp=12,211.06,,0,25.83 ]Cut Bank In Newcastle[/url] which is probably 10%?
My suggestion would be something around the 42 mark on the front then get cheap 14, 16, 18 sprockets for the back to decide what works before getting something more expensive and duarable.
I built a mtb with slicks and 36:18 swapped to a 32:16 but still pedalling it out.
They're exactly the same ratio...