fatman

In the case of a 3 chainrings front, 9 cogs rear cassette bike. If you can not use all the chainrings in convination with all the rear cogs, Why are bike called 27 speeds?

For example the manual of my bike said that you should not cross the chain with the big chainring and the big rear cog. I have done this and sometime I get into trouble.

Rev.Chuck

Because it is easier than figuring out exactly how many "effective" gears a bike has for all the different combos there are based on the three front rings, 20t to 56t and nine cassete cogs 11t to 34t. You realize that there are similar gear combos in all three rings, you only have about 17 gears.

Dave Stohler

Only neophytes or ignoramuses use the term "27 speed". To the cyclist community, it's a "9-speed with a triple".

chewa

Or traditionalists, surely Dave.

I grew up in the era of the 10 speed, and I still occasionally refer to 27 speed. But then I still ask for a block rather than a cassette.

SamDaBikinMan

It is marketing hype! There is not such thing as a 27 speed bike.

deliriou5

Wow... if a triple has only 17 effective gears, then how many does a double have!!??

And how "bad" is it really to be in big ring big cog? I've done it a couple times, but only for a couple seconds at a time...

shokhead

18 of course

chewa

Depending on your chainring sizes and cassette ratios it is quite conceivable that, if you ride so as to prevent cross chaining, a triple front with 8 or 9 sp rear could realise as few as 12 - 14 gear ratios which are significantly different from others, with many more combo's giving similar gears.

I use my triple (when commuting I lock out the smallest chainring) and 8 sp rear as 3 sets of 5 gears, outer 5 for the outer ring, middle 5 or six for the middle, inner 5 for the small ring, and don't really go outwith that.

With a new chain, you can really feel when you cross chain, even with today's more flexible links.

deliriou5

so from what i gather the purpose of the triple is not so much to provide you with a greater number of gear ratios as it is to give you a wider range of ratios

joeprim

That's the way I view it. Although you do get more. But to be sure calculate all the ratios you have and see how many unique useable ones you have.

Joe

fatman

Hey! I like that I will use it as a rule.

miamijim

The 'road' wheels for my mountain bike are setup.....a triple with a 9-speed rear that yields about 25 effective gears.

What I did was use a cassette thats designed to pick-up where the previous chainring left off...

The answer is yes, your bike does have 27 gear ratios...no 2 are exactly alike although many are very close.

I didnt know I was an ignoramous......Oh, well.....

Allister

My bike has only one speed - flat out.

Dave Stohler

My touring bike uses a 6-speed rear, with half-step drops from a 4-tooth difference on the two big rings. Combine that with a 14-tooth drop to the granny gear, and I have a true 18 unique gear combos.

MikeOK

You can use the big big if you have everything adjusted right, I do it occasionally in some situations but for no longer than I need to. It does put quite a strain on your drivetrain but it's a bike, not the space shuttle...