Gear ratios.

rolton

Hi, i was wondering if anyone could help me.
I am considering buying a fixed gear track bike. Just to get me from A to B. Simple set up, minimum maintenance.
But i live in Bristol which is very hilly, so i was wondering what anyone would suggest for me in terms of gear ratios, I haven't got thighs like Chris Hoy so i need something that i can get up to speed quickly and keep momentum up with.
Any Help would be greatly appreciated.
Thanks

gkerr4

look at what the "off-the-peg" fixed gear bikes have for a good starting point

for example the langster I have has a 42t chainring and 16t sprocket.

I think this gives a "gear inches" of around 70 inches which is pretty common across the "off-the pegs".

this gives you about 20mph at 100rpm and this works for me pretty well - that said, Blackpool isn't as hilly as bristol so perhaps you would benefit from a slightly larger sprocket - perhaps 42x18 would be fine?

Johnpwr

If you're going for fixed, then you have the problem of having something low enough to get up the hills and high enough to be able to spin fast enough on the downhills. A 66 inch gear is generally considered suitable for general riding and equates to a cadence of about 90 when averaging 18mph.

Riding somewhere almost exclusively hilly, I would suggest that a single speed freewheel would be more appropriate, because then you can coast on the downhills. I've been spun by my 66" gear at a cadence of ~195 (or that's what the computer said ) at 30 odd mph and it was unpleasant, although if you've got the knees for it, then that'd be your call.

Best of luck.

gkerr4

as an aside - and this isn't proven and doesn't stand up to medical interrogation but this is my opinion.

I think that riding downhill fixed - where the pedals are able to "drive" your feet around often at pretty high RPM due to the gearing - contributed to the fact that I have needed two bouts of knee surgery this year - one for each knee and both for meniscal tears. I started riding fixed in October last year an my prpblems started in January this year. i won't ride my langster in 'fixed' mode again and currently use it in singlespeed mode to build my legs back up post-surgery.

John.T

gkerr4. Your problem was not riding down hills on fixed. It was letting the gear drive you. When going down hill you should still pedal so as to keep up with the gear. Letting the gear drive you is not only bad for the legs but is also dangerous as the bike is less stable.
I ride 42/17 which is about 65". I can get up most of my local hills on this but do not go into the Dales on it. I can just handle 30 mph down hill which is 150 rpm. Above that the brakes go on.

barrybaines

i live in bristol and have been happily riding 48 18 on my fixed for a while now, although today i decided to give my 16t sprocket a whirl on the commute, it was interesting shall i say! However i am gonna stick with it for the rest of the week to see if i gain anything from the extra effort

oldwelshman

gkerr4 wrote:

as an aside - and this isn't proven and doesn't stand up to medical interrogation but this is my opinion.

I think that riding downhill fixed - where the pedals are able to "drive" your feet around often at pretty high RPM due to the gearing - contributed to the fact that I have needed two bouts of knee surgery this year - one for each knee and both for meniscal tears. I started riding fixed in October last year an my prpblems started in January this year. i won't ride my langster in 'fixed' mode again and currently use it in singlespeed mode to build my legs back up post-surgery.

I would be very surprised if riding a fixed caused meniscus tear, cannot see how cycling motion can cause this. I have had four of thos ops and felt when I did the inhury every time, usually caused by a twisting of the knee injury.
Anyway did you not use the brake ?

aracer

Johnpwr wrote:

Riding somewhere almost exclusively hilly, I would suggest that a single speed freewheel would be more appropriate, because then you can coast on the downhills.

I'd second that - really can't think of anything much more inappropriate for riding round Bristol (or anywhere similarly hilly) than a fixed. Irritating where I live because whilst there are plenty of roads where one works fine - including going into the towns in either direction - I live at the top of a hill which results in 30mph+ downhill runs when cold in whichever of the 3 possible directions I choose to set off. Lived on the flat when I got it :roll:

Ken Night

rolton wrote:

.
But i live in Bristol which is very hilly,.......

It's not that bad!


Riding fixed will improve your climbing, and you'll want to change the gearing as you get fitter-so be prepared for that

It'll depend on how you ride right now, and most people will use between 65" and 75"

In Plymouth, which is hillier than Bristol, I use 67" and 70" with sprockets on either side of the hub. I have run 72" and found that OK

One of the racing snakes runs his Langster at 81" and is difficult to keep up with on all but steepish downhills (29mph at 120rpm)

You could also use a fixed on one side, and a singlespeed freewheel on the other-with lower gearing on the freewheel

gkerr4

oldwelshman wrote:

gkerr4 wrote:

as an aside - and this isn't proven and doesn't stand up to medical interrogation but this is my opinion.

I think that riding downhill fixed - where the pedals are able to "drive" your feet around often at pretty high RPM due to the gearing - contributed to the fact that I have needed two bouts of knee surgery this year - one for each knee and both for meniscal tears. I started riding fixed in October last year an my prpblems started in January this year. i won't ride my langster in 'fixed' mode again and currently use it in singlespeed mode to build my legs back up post-surgery.

I would be very surprised if riding a fixed caused meniscus tear, cannot see how cycling motion can cause this. I have had four of thos ops and felt when I did the inhury every time, usually caused by a twisting of the knee injury.
Anyway did you not use the brake ?

i know what you are saying - it is usually a "twisting / impact" type of injury.

but when I was trying to explain to the ortho about 'fixed' gear riding - he just told me to be careful of devices which can cause movement in the knee "from the foot up" - whether it was to blame or not (there are thousands of fixed riders and they don't all have knee issues!) or perhaps I have some sort of genetic defect which leads me to be easily injured - i'm not sure, but after the horrid year I have had with it all - i'm simply not going to risk it any more.

rolton

So a freewheel singlespeed bike is what i should go for?

Ken Night

rolton wrote:

So a freewheel singlespeed bike is what i should go for?

No, a fixed/singlespeed-one on either side of the hub

edhornby

have a look out for second hand langsters, you may be able to pick one up fairly cheaply and they have a flip-flop (a fixed on one side, a freewheel on the other)

meagain

What others said: mid-60s is a good starting point if hills involved - altho' if you are reasonably fit to begin with you will probably be able to step up to c. 70". And don't be embarrassed about using brakeS downhill!

Fixed and knees has in the past been a much-discussed subject in Special Interests. Received wisdom used to be "bad" but from direct experience consensus was pretty much "not proven". Personally, my knees are not in the best of nick - running is for example pretty painful. And yet I rarely get any discomfort riding other than when I use a geared bike. For me at least I THINK this is because I tend to push a higher gear when available to me. Maybe "lower" is better, whether fixed or free?

meagain

What others said: mid-60s is a good starting point if hills involved - altho' if you are reasonably fit to begin with you will probably be able to step up to c. 70". And don't be embarrassed about using brakeS downhill!

Fixed and knees has in the past been a much-discussed subject in Special Interests. Received wisdom used to be "bad" but from direct experience consensus was pretty much "not proven". Personally, my knees are not in the best of nick - running is for example pretty painful. And yet I rarely get any discomfort riding other than when I use a geared bike. For me at least I THINK this is because I tend to push a higher gear when available to me. Maybe "lower" is better, whether fixed or free?

rolton

Well, thank you very much for all of your help.
I will be sure to come here next time for advice.

Cheers.