CYCLING: Putting new Chainrings on my bike

geordie_ben

Marco_Panettone wrote: »

The small sprocket on the cassette is 11-tooth already (according to the link), so I don't think it's an option.

What sort of speed are you currently doing when you spin out? There's a simple gear ratio-speed-cadence calculator here: http://www.machars.net/bikecalc.htm

I'm clocking 27-28MPH

wongataa

geordie_ben wrote: »

Another bike isn't an option.

haven't got a clue what cadence is, but when I'm going down hills I can't pedal any faster as the wheels are going that fast There's no resistance against the gears

Cadence is how fat you are pedalling.

Marco_Panettone

geordie_ben wrote: »

I'm clocking 27-28MPH

28MPH with 44-11 is a cadence of 83. If you can raise this (it'll take some time, but is more than possible) to 100 you'll hit 33MPH in the same gear.

geordie_ben

Marco_Panettone wrote: »

28MPH with 44-11 is a cadence of 83. If you can raise this (it'll take some time, but is more than possible) to 100 you'll hit 33MPH in the same gear.

No I wont.. there's no resistance against the gears, meaning there is no way I can increase the speed by pedalling

rdr

Marco_Panettone wrote: »

28MPH with 44-11 is a cadence of 83. If you can raise this (it'll take some time, but is more than possible) to 100 you'll hit 33MPH in the same gear.

On my slicked up mountain bike with similar gearing I spin out at around 33mph, on my road bike with 700c wheels and 50-11/12/13 gears I can manage 34-35 on the same hill.
I think you need to work on your leg speed before you change the gearing, a cadence of at least 80 should be your norm and flat out you should be able to peak well over 100. This sort of cadence is more efficient, less tiring and less likely to damage your knees.
My first thought is - is your saddle high enough? - having your leg straight when sitting on the saddle with your heel on the pedal is a good starting point.
You cant get 46 tooth rings to fit but to go any bigger you would need to change the front changer and your rear changer would not have the capacity to take on the slack unless you reduced the range at the back. If you fit this ring your will need an extra link in your chain.

geordie_ben

rdr wrote: »

On my slicked up mountain bike with similar gearing I spin out at around 33mph, on my road bike with 700c wheels and 50-11/12/13 gears I can manage 34-35 on the same hill.
I think you need to work on your leg speed before you change the gearing, a cadence of at least 80 should be your norm and flat out you should be able to peak well over 100. This sort of cadence is more efficient, less tiring and less likely to damage your knees.
My first thought is - is your saddle high enough? - having your leg straight when sitting on the saddle with your heel on the pedal is a good starting point.
You cant get 46 tooth rings to fit but to go any bigger you would need to change the front changer and your rear changer would not have the capacity to take on the slack unless you reduced the range at the back. If you fit this ring your will need an extra link in your chain.

I might adjust my seat again

I'm sure you're all missing what I am saying (bar one person above) - I CANNOT PEDDLE ANY FASTER AS THERE IS NO RESISTANCE AGAINST THE GEARS - IN OTHER WORDS, I'M PEDALLING AGAINST THIN AIR

DCodd

geordie_ben wrote: »

I might adjust my seat again

I'm sure you're all missing what I am saying (bar one person above) - I CANNOT PEDDLE ANY FASTER AS THERE IS NO RESISTANCE AGAINST THE GEARS - IN OTHER WORDS, I'M PEDALLING AGAINST THIN AIR

No they are not. The reason you are pedalling against thin air is that your cadence (RPM) is only 80. Effectively, your rear gears (cassette) are travelling faster than your pedalling speed. If you increase your pedalling speed (RPM) to a sufficiently faster speed then the cassette / freewheel will engage again and you will feel resistance when you pedal thus increasing your speed.

Changing your chain rings can be problematic, as Marco Panettone has suggested, the rest of the drive train may not be compatible i.e. front and rear deraileurs, chain length etc. You could even find that the chain will be thrown off in some gear combinations because of poor chainline.

Such issues with gear ratios, cadence, chainlines etc are well covered online. I find for a reasonable starting point for reference is here:
http://sheldonbrown.com

rugbyleague

Sorry didnt see the cassette bottom sprocket size. No will not be able to get a cassette with a sprocket smaller than a 11 tooth.

83 appears quite low for flat out, this is my daughter in a roller racing national final a couple of years ago.

http://www.youtube.com/watch?v=9KoFl440ssY

Top speed was 50mph with a cadence of 200rpm.

Speed will improve with leg speed.

Marco_Panettone

rugbyleague wrote: »

Sorry didnt see the cassette bottom sprocket size. No will not be able to get a cassette with a sprocket smaller than a 11 tooth.

83 appears quite low for flat out, this is my daughter in a roller racing national final a couple of years ago.

http://www.youtube.com/watch?v=9KoFl440ssY

Top speed was 50mph with a cadence of 200rpm.

Speed will improve with leg speed.

Nice! Which one's your daughter? Great effort by both, and 0.05 between them over 500m is ridiculously close!
:T:T:T

brat

I think, with respect, you need to improve leg speed, your downhill cadence of ~83 is not fast enough to start to think about bigger chainrings.

You should be able to manage cadence of 120 for a downhill, pushing speeds up to 40 mph.

I get 40+ mph out of my Whyte CycloCross (downhill) while still pedalling against pressure which, at 46:11 with a 700 wheel is almost exactly the same cadence/speed ratio as yours.