All about gears

sand_hun

Johnmcl7 said:

You only need to go up onto the big ring if you need to go faster, if you're happy with the speeds you're doing on the small ring then you can stick with it.  The current trend with bike gearing is to have one ring on the front and bigger cassettes at the back.

As for cars, I can't stand automatics although it's approaching the time I can't avoid them any longer.

Aaah OK thank you. I rode 25 miles + the other day whilst remaining on the small ring and adjusting gears via the right shifter. If felt as if that was enough in terms of gear range and speed, so I guess I could get away with doing it like this but it probably means I'm not using the bike to its full potential

EssexExile

Automatic headlights, automatic choke, automatic wipers, automatic cruise control, automatic lane control, why on earth wouldn't you want automatic gears?

NBLondon

Goudy said:

I asked why does that arrow on the dash keep lighting up, to which he replied it's a gear change indicator that tells him when to change, clever isn't it.
I said not really, if it's clever enough to know what gear then why doesn't it just select the right one for you!

'Cause it isn't that clever... The indicator is basically saying "revs have reached this number". If you're actually competent at driving a manual, your ears are telling you that already. Plus, you are reading the road ahead and know whether you are likely to need to change down again in the next 15 seconds and making the decision to stay in 3rd (or whatever). Save 0.005p of fuel by changing up early and spend 0.007p of wear and tear on the transmission. I've only driven a modern automatic in the US when I appreciated being able to put more attention to unfamiliar roads. Maybe I should try one and see how they have changed since the 90s.

facade

sand_hun said:

The bike

I'm struggling to comprehend how to use shifters on a road bike. I tend to stay on the small chainring and only use the right shifters to go up/down gears. Can anyone here explain in layman's terms how (and when) you might want to use the left shifters to switch between the small and big chainring?

The Plan is to pedal at a nice constant speed- one..two..one..two..

You keep changing up the gears until it starts to become hard work, but you can keep up the one..two..one..two..

If pedalling gets easier, you go up a gear (and go faster) if it gets harder, you go down a gear or two.

On a flat road, you will be on the large chainring all the time.  Going up a steep hill you drop to the small chainring as you can't get any lower gears on the large one, drop chainring when you are in the middle of the rear gears, go up a chain ring when you get to thetop gear on the back.

Always start off in a low gear, so change down 3 or 4 gears as you come to a stop.

Johnmcl7

sand_hun said:

Johnmcl7 said:

You only need to go up onto the big ring if you need to go faster, if you're happy with the speeds you're doing on the small ring then you can stick with it.  The current trend with bike gearing is to have one ring on the front and bigger cassettes at the back.

As for cars, I can't stand automatics although it's approaching the time I can't avoid them any longer.

Aaah OK thank you. I rode 25 miles + the other day whilst remaining on the small ring and adjusting gears via the right shifter. If felt as if that was enough in terms of gear range and speed, so I guess I could get away with doing it like this but it probably means I'm not using the bike to its full potential

As long as you're happy with the gears you're and not spinning too fast on the pedals then I wouldn't worry about it.  Bikes generally have a wide range of gears to be flexible so you may simply not need all those gears for the route you're doing.

Username03725

Bike gears:

You have to imagine your gears as a range of ratios spread over the front 2 cogs and the number of cogs on the rear wheel. Let's have a stab at 8 cogs on the rear wheel. It doesn't matter if there are 9, 10, 11 or even 12, and road bikes have lately started appearing with 13 but that's getting silly. Your 8 rear cogs each have a number of teeth; lets guess the biggest has 28, the smallest maybe 14 teeth. Maybe they go down in equal steps of 2 teeth per cog - 28, 26, 24, 22, 20, 18, 16, 14. The front two might have 28 teeth on the small cog, 38 on the bigger one. Who knows? It doesn't matter though, the principle remains.

With that setup, you have 16 gears in total, 2 sets of 8 made up of 8 gears to choose from on the small front ring, and 8 on the bigger ring.

The lowest ratio is small front to big rear - 28:28 in my guesswork above. That's (handily) a gear size of 1. Your biggest gear (highest, equivalent to 5th or 6th in your car) is big front to small rear, 38:14, a ratio of 2.71. So it follows that in your lowest gear for each turn of the pedals you go forward one unit of distance, and in your biggest gear you go 2.71 times further. But nothing is free in terms of energy transfer, so it takes more effort to pedal in the higher gear. In exchange for the extra effort you go further. It's that simple.

Back to your 16 gears. You have gear sizes that go from 1 to 2.71, starting from small front / big rear to big front / small rear. At the extremes the easiest (but slowest speeds) gears are the first few big rear cogs in conjunction with the small front cog, and conversely the hardest gears (but faster speeds) are the smaller rear cogs with the large front cog. And in the middle there's a mix of ratios (gear sizes) where similar gear sizes are found in combinations of big or small front.  

How best to use them? You don't need to start in the lowest gear like a car as your legs have muscles, not pistons that must keep moving to create force. And you just use whatever feels comfortable for any given speed and effort. Pootling along on a slight downhill? Big front, one of the middle rear cogs. Or the small front and one of the smaller rear cogs - you'll find they're quite similar once you get used to swapping gears. Gentle uphill you have the same options - small front and a middling rear cog, or perhaps the large front and a bigger rear cog. The two options will provide a similar speed for the same effort. It's just up to you which combination to select. Avoid extremes of small to small and big to big though as it can stretch your chain, and try to make use of all gears to even out the wear. If you never use e.g. the biggest gear (big f to small r) and then one day you need it, your chain may have worn and longer fits over the unused teeth correctly.

Now you get to pedalling speed, it's called cadence and refers to pedal revs per minute. Slow is around 40 & below, middling is 50-60 (around 1 rev per second, try counting it), and then 70-80 is a good speed. And as your speed is limited by your strength & fitness you'll find that your cadence points you to the right gears to maintain that approximate cadence of 50-60 for pootling and 70+ if you're getting a move on. Note this is for road cycling. Picking extremes just to make a point, if a hopelessly unfit cyclist is riding with a fit club rider at 18mph, the unfit guy might be busting a gut pedalling for all he's worth in a lower gear whilst clubman is ambling along in a big gear at half the cadence. The point being there's not a one size fits all answer to what gear and what cadence to pedal at. You use the gear selection that works for you.

Don't be afraid to change gear. It's not like a car, working up to top for cruising. With UK topography you're rarely on a level road for long, and you have 16 (or whatever) gears, so use them, finding the best for any given situation. On mine I'm up & down all the while, and swapping front cogs from big to small and back again for whatever works best. It makes life easier and cycling is more enjoyable.

Mutton_Geoff

sand_hun said:

The bike

I'm struggling to comprehend how to use shifters on a road bike. I tend to stay on the small chainring and only use the right shifters to go up/down gears. Can anyone here explain in layman's terms how (and when) you might want to use the left shifters to switch between the small and big chainring?

It's really important that you use both the front and rear chain rings otherwise you will be "cross chained" some of the time. This is not good for your bike.

Try this video, although your bike probably has different levers for the gear changes.

https://www.youtube.com/watch?v=v-DIl9UnvY8

Grumpy_chap

Isn't the truth that major High Street Retailers sell bikes and make much of 18 gears (or whatever, where the bigger number = better) but, for the vast majority of purchasers, a basic 6 gears will do just fine?  How many people with three cogs only ever use the centre cog?

Username03725

Grumpy_chap said:

Isn't the truth that major High Street Retailers sell bikes and make much of 18 gears (or whatever, where the bigger number = better) but, for the vast majority of purchasers, a basic 6 gears will do just fine?  How many people with three cogs only ever use the centre cog?

How many? Lots probably. 

The issue is that lots of gears gives a wider range of gear ratios with a smaller difference between each one, and for people whose buying decisions are led by arbitrary values like the number of gears that’s possibly a deciding factor. 16 gears with 2 front rings will have a few duplicate or almost duplicate ratios; a triple clanger will have even more but the range from easiest to hardest will be wider and the gap between gears will be much more manageable. A similar range low to high with one ring will have enormous gaps between each gear, so you can either keep it simple and have no front changer but big gaps between gears, or 2 or even 3 rings up front and more duplicates but a smoother spread.

I've set up a few bikes with cheap gear sets over the years and the triple ring front derailleurs are almost impossible to get bang on for each ring, and given the number of people who’ve asked me the same question that OP has and then given up trying to grasp it opting instead to leave it in the middle or easier of the two, I do believe that simple gear sets with one ring and a reasonable spread of 8 or 9 gears would be enough for most.

Alanp

Of course the simplest thing would be to buy an electric bike….