Gear numbers up and now down

[Pale Rider]

Browsing new MTBs I notice some now come with 20 gears - 2 X 10.

I'm old enough to remember when 18 - 3 X 6 - was an innovation, then 21, then 24, then 27, then 30.

I wonder what is the thinking behind 20 gears.

Is it all just marketing?

 

[CopperCyclist]

21 gears was normally 3 x 7.
20 gears is 2 x 10.

Although there is one 'extra' gear in the 21 gear setup, it's actually much better to have the 10 separate cogs on the back, rather than a lesser number of 7. This means each gear is closer to the other, so you have less chance of having big gaps where you don't really have the right gear, and it's easier to use your gears to keep a constant cadence.

Additionally, even though you have 21 gears, the overlap between them would be great due to running on three different front cogs. Without doing the calculations, I'd assume you'll probably get a better range of gearing on the 20 gear setup.

If you ignore the total number of gears overall, and look just at the increase of rear cogs, you'll see the development there is what you'd expect 5 to 6 to 7 to 8 to 9 to 10 to what I believe is the most recent, 11.

 

[lulubel]

You generally get a wider range of gears with a triple because you can have the same range (probably 11-34 or similar) on the back, but the 3 rings on the front can give higher and lower gears than a double.

As I understand it, triples are generally used on more XC oriented bikes because they're expected to climb and descend, as well as often being used on the road to get to and from where they're going. Double, and even single chain rings are used when there's less requirement for a wide range of gears. (I'd assume DH fits into this category.)

@CopperCyclist I don't know what it's like where you ride, but there isn't any benefit to having the gears close together for the MTBing I do because opportunities to maintain a steady cadence are very few and far between. It's a different matter on the roadie, of course, but even then I went for a road triple with a megarange cassette, so I've got the low gears I need to get up the climbs, and the high gears I want for coming down them!

 

[Cubist]

The advantage as far as I'm concerned is that you can pick a front chainring best suited for the bit of riding you're on, and use all the rear cogs without worrying about chainline etc. I run 38/26 and 11-36 on my full sus, and have converted a 9 speed 42/32/22 over 11-32 to a Bash and 36/22 over 11-34. I lose one and a half gears at the top, which I rarely used, gain a crawler gear, but get to play with 36/11-34 in the big ring. WHich reminds me, I need to adjust the chainline, as small/small is not chain friendly at the moment. The advantage with this second setup is I can fit a bash guard and no longer worry about near fatal injuries from the outer teeth.

 

[02GF74]

with more than 1 chain ring on front, there is an overlap in gears so although the number of combinations may be 27, the number of different ratios is less than that. also changing front gear is more troublesome and there is risk the chin can drop off even with correclty adjusted mech - is rare though.

the latest is 1x11 - this gives 11 different ratios, probably the same as 27 spd but needs no frotn mech plus the teeth on the front chainring are taller meaning the chain will not jump off. donwside is the chain has to go through quite a bit angle when used at the biggest and smallest sprockets so it isn't going to last as long.

... and yes, there is some marketing involved as the manufacturers have to come up with new items to get us to part with our pennies.

 

[Motozulu]

This is all very technical for me - all I know is that on my Merida -30 gears- I never use the big ring (downhill) even on the road ride home when I could use it. I could get rid I'm sure and just have the 2 cogs but I would'nt have a clue how to go about it so will just carry on ignoring it.

 

[lulubel]

this gives 11 different ratios, probably the same as 27 spd but needs no frotn mech plus the teeth on the front chainring are taller meaning the chain will not jump off.

Wow! What kind of cassette would you need with a single chain ring to get the same range as a 22/32/44 triple with an 11-34 cassette?

 

[02GF74]

10-42

SRAM XX1 see: http://www.pinkbike.com/news/sram-xx1-ride-11-speed-2013.html

 

[lukesdad]

Well if you could still get quality 7 speed components I'd still be running it !

 

[lulubel]

10-42

According to Sheldon, that gives a range from 1.7 to 7.0 with a 36 tooth chain ring.

The triple setup is giving a range from 1.3 up to 7.8.

I'm not sure if it would matter to most, or if it's just me who uses those high and low gears. I can see how it could be achieved with a double, though.

 

[Cubist]

This is all very technical for me - all I know is that on my Merida -30 gears- I never use the big ring (downhill) even on the road ride home when I could use it. I could get rid I'm sure and just have the 2 cogs but I would'nt have a clue how to go about it so will just carry on ignoring it.

Simples, to coin a phrase.

Buy a bashguard from BBG bashguards for about £12 posted from the states, and bolt it on in place of your outer chainring. You can even do this with the cranks on the bike. Trim your front mech using the limit screws to only operate on the first two chainrings, and shorten your chain. About twenty minutes' work. You can change your middle ring to give you a slightly higher gear, say a 34 or 36t would be ideal. Looks neat too.