Dummy need help with transmission

[WhiteEagle197]

Hi,
I have a tricky question. Unfortunately I am quite a dummy to bicycle mechanicals so I don't know the right terms/expressions so I will try to explain with my own words :-)
So, I have an entry level Halfords hybrid bicycle with 21 speeds (3 cogwheels at the pedals and 7 at the rear wheel). I recently decided to go for a new higher-level hybrid bicycle, preferably one with 24 speeds.
But I am uncertain about a thing: when I ride on a straight plain road (0% rise - we have loads of them around here :-)) using my present bicycle even if I move that chain on the largest cogwheel (front) and the smallest (rear) it is still not very fast. When I reach approx 18-20mph speed on one of those roads I feel that I have to pedal too quickly and it doesn't feel comfortable. I have quite strong thighs and I feel I could pedal MUCH harder and create bigger torque (but I don't like to pedal any faster, it feels awkward and uncomfortable). So I would change one gear down if there was one more even smaller cogwheel at the rear. But there isn't one. So I limited to that 18-20 mph speed, while I feel I could do 22 or even 24 if I had an even smaller cogwheel at the rear or a bigger at the pedals. I hope it is clear what I try to explain, I don't know the right terms/expressions.
The real problem is that I don't know how to look for faster gears/cogwheels, what are the keywords/specs. If I buy a bicycle that has 24 speeds it may be either that it has cogwheels sized so that I can reach higher speed OR it can be that the more gears mean only finer steps between the same min. and max. transmission. How do I ensure that I buy a bicycle that has a smaller cogwheel at the rear wheel (and/or a bigger one at the pedals) than my present one has?
Thank you,
WE197

 

[EYE-TYE-MAD]

Hi,
I have a tricky question. Unfortunately I am quite a dummy to bicycle mechanicals so I don't know the right terms/expressions so I will try to explain with my own words :-)
So, I have an entry level Halfords hybrid bicycle with 21 speeds (3 cogwheels at the pedals and 7 at the rear wheel). I recently decided to go for a new higher-level hybrid bicycle, preferably one with 24 speeds.
But I am uncertain about a thing: when I ride on a straight plain road (0% rise - we have loads of them around here :-)) using my present bicycle even if I move that chain on the largest cogwheel (front) and the smallest (rear) it is still not very fast. When I reach approx 18-20mph speed on one of those roads I feel that I have to pedal too quickly and it doesn't feel comfortable. I have quite strong thighs and I feel I could pedal MUCH harder and create bigger torque (but I don't like to pedal any faster, it feels awkward and uncomfortable). So I would change one gear down if there was one more even smaller cogwheel at the rear. But there isn't one. So I limited to that 18-20 mph speed, while I feel I could do 22 or even 24 if I had an even smaller cogwheel at the rear or a bigger at the pedals. I hope it is clear what I try to explain, I don't know the right terms/expressions.
The real problem is that I don't know how to look for faster gears/cogwheels, what are the keywords/specs. If I buy a bicycle that has 24 speeds it may be either that it has cogwheels sized so that I can reach higher speed OR it can be that the more gears mean only finer steps between the same min. and max. transmission. How do I ensure that I buy a bicycle that has a smaller cogwheel at the rear wheel (and/or a bigger one at the pedals) than my present one has?
Thank you,
WE197

OK, lets start with the basics, the bit at the front is called a chainset & the bit at the back is a cassette. The chainset has removable chain rings in order that gearing can be changed to be faster, slower, more comfortable & so on. For road bikes they generally fall into two categories, 1. standard gearing or 'double' ring sizing 53/39 or 52/42, or 2. Compact gearing: ring sizing 34/50, 34/48 or 36/50. There are also triple chainsets available, although it's true to say they are generally frowned upon by most cycling purists. The combination of the chain ring size & the rear cassette ratio determines revolution speed & hence the ultimate speed of the bike. When considering a gear ratio you should give most attention to the size range of the sprockets on the cassette. Commonly this is 23t or 25t at the large end & 11t, 12t or 13t at the small end.The larger the sprocket size, the lower the gear, which is great for climbing up hills but not much use when you want to burn some rubber. So there you have it, if it's speed you want, big at the front, small at the back. If it's climbing made easy you want, it's small at the front, big at the back. Most riders settle for the compromise, somewhere in the middle, my particular preference is 53/39 chain rings with a 12 or 13-23 cassette.

 

[rollinstok]

Hi, the vast majority of rear wheel cassettes ( cogwheels ) start with the smallest being 11 teeth, so you need to look at the pedal end ( chainrings ). On most mountain bikes the smallest is 22, then 32, then 42....these sizes cross over on to some hybrids as well. Some hybrids, however, are more road based and offer bigger chainrings..maybe up to 52 teeth so check out before you buy the next bike. You are pretty accurate when you say that 24 speed will probably not give you more speed..just smaller gaps between gears. More hybrids are adopting road bike gears where you have 10 gears at the back..smallest usually 11 again, and just 2 gears at the front..usually 39 and 52..this will suit you better. Hope this helps a little.

 

[theloafer]

hi whiteEagle
this site will poss help you under stand things better.. http://sheldonbrown.com/ lots of great info

 

[WhiteEagle197]

Thank you very much for all the help. Yes, know I found out my problem: by bicycle has only a 42 biggest ring size on the chainset and 13 ring size on the casette. No wonder why I felt it too slow. Now I will be looking for one that has 48 or 52 on the chainset and 11 on the casette. Thank you!

 

[lulubel]

Don't get too hung up on the 11 on the cassette. It's the number of teeth on the big chainring that will be most significant when it comes to your top speed because that's where you can make a dramatic change.

 

[WhiteEagle197]

Don't get too hung up on the 11 on the cassette. It's the number of teeth on the big chainring that will be most significant when it comes to your top speed because that's where you can make a dramatic change.

Thank you! Do you think I should go for the 48 or the 52?

 

[lulubel]

It depends on the kind of terrain you're riding on, and whether you're looking at a double (2 chain rings) or triple (3 chain rings). A double with a 52 big ring will probably be something like 39/52 (standard double) whereas one with a 48 big ring will be more like 34/48 (compact double). You have to be aware of your lowest gears as well as your highest if you want to get up hills - if you come across hills on your rides - and the 34 small ring will obviously give you easier gears for going uphill.

The alternative is a triple with something like 30/40/52, which gives you the best of both worlds - big high gears and small low gears.

 

[WhiteEagle197]

It depends on the kind of terrain you're riding on, and whether you're looking at a double (2 chain rings) or triple (3 chain rings). A double with a 52 big ring will probably be something like 39/52 (standard double) whereas one with a 48 big ring will be more like 34/48 (compact double). You have to be aware of your lowest gears as well as your highest if you want to get up hills - if you come across hills on your rides - and the 34 small ring will obviously give you easier gears for going uphill.

The alternative is a triple with something like 30/40/52, which gives you the best of both worlds - big high gears and small low gears.

Thank you!!

 

[lukesdad]

Don't get too hung up on the 11 on the cassette. It's the number of teeth on the big chainring that will be most significant when it comes to your top speed because that's where you can make a dramatic change.

Don't get too hung up on the 11 on the cassette. It's the number of teeth on the big chainring that will be most significant when it comes to your top speed because that's where you can make a dramatic change.

Thats not quite correct, you will get a higher gearing for dropping one tooth on the cassette than you will for going one up on the chainring.

 

[lulubel]

Thats not quite correct, you will get a higher gearing for dropping one tooth on the cassette than you will for going one up on the chainring.

We weren't talking about going up one on the chainring. We were talking about going up between 6 and 10. That was why I said "because that's where you can make a dramatic change". When your starting point is 13 teeth on the cassette, there isn't as much room for manoeuvre.

 

[lukesdad]

We weren't talking about going up one on the chainring. We were talking about going up between 6 and 10. That was why I said "because that's where you can make a dramatic change". When your starting point is 13 teeth on the cassette, there isn't as much room for manoeuvre.

So how do you explain a 48/13 has a ratio of 7.5 and 42/11 has a ratio of 7.7. Changing the chain rings will also depending on size will involve new crankset new chain and probably new rear mech bottom bracket and front mech (for anything bigger than a 48 ).The cassette swap depending on the cassette it might only involve dropping in a smaller outer cog.

 

[lulubel]

Changing the chain rings will also depending on size will involve new crankset new chain and probably new rear mech bottom bracket and front mech (for anything bigger than a 48 ).The cassette swap depending on the cassette it might only involve dropping in a smaller outer cog.

I know that. We also weren't talking about changing anything. WhiteEagle is buying a new bike. Perhaps you should take a look at this thread if you're not up to date with the whole situation:
Can you recommend a reliable hybrid bicycle?

 

[lukesdad]

Ah so if you know all that care to change your statement about cassettes and chainrings ?

 

[lulubel]

Ah so if you know all that care to change your statement about cassettes and chainrings ?

What statement? The one where I said that it makes more sense to focus on getting the right size chainrings and not worry so much about the number of teeth on the cassette cogs? No, since it's good advice, as you made clear in your previous post where you explained how it's much easier and cheaper to change a cassette if the gears you have aren't right for you than it is to change chainrings.

If he buys a bike with a 48 or 52 tooth big chainring rather than his current 42, he's made a similar or better change than he could by buying a new bike with the same size chainrings as his current one but an 11 tooth small cog. If he then finds that the gears still aren't high enough for him, he can then change the cassette relatively cheaply.

If he focuses his attention on the cassette, and gets the smallest small cog he can get along with chainrings the same size as his current ones, and then finds the gears aren't high enough, he's left with no option but to change the chainrings along with all the expense that entails, or to live with a bike that isn't right for him.