Monday, October 27, 2008

Ask Dr. Stupid, from Bedrock

> Dr. Stupid,
> Do road and mountain bike cassettes have the same spacing?
> Sincerely,
> FF

Well Mr. Flintstone,

I may need to put on my special cycling cap for this one, as it's both
an easy and potentially difficult question to answer.

A (Shimano, SRAM, etc.) 8 speed cassette has the same spacing between
the cogs, regardless of application. So do 9 speed and 10 speed.
Although the distance between cogs is different for 8,9,10 (amoungst
other things).
Campy may do some strange things, they're allowed, they are Italian
and God-like.
Prior to 8 speed, they did have different spacing between cogs, but it
was more based on Brand, i.e. Suntour, Shimano, Regina.

From 8 speed to 10 speed, the total width of the cassette is about the same.
Meaning you can put a fancy-dancy 10 speed cassette on an older 8 speed hub.
I just did it downstairs, just to make sure (and I needed to know myself).
Again, Campy is probably stupid... I mean different.

Doesn't mean that your 8 speed shifters are going to work w/ the 10
speed though.
AND, more importantly, not all road ders. are capable of handling the
large cogs typically found on a "mtb" cassette.

Cassettes are cassettes. If you want to run an 11x23 on your mtb,
then you can, and if you want to run a 12x34 on your Carbon road
machine, then you can (w/ maybe a new der.).

A Road wheel has different spacing than a MTB wheel.
Road rr. wheel is 130mm from dropout to dropout.
MTB rr. wheel is 135mm.

The only relevance there is that although you have a 29er wheel, and
the rim size is 700c as well. It will not (w/o frame spreading) fit
in your road frame.
And it's probably got a disc brake too.
This does mean that you *can* if you want, run some sweet cross tyres
(or any 700c road tyre) on that 29er of yours.

Course this can be more complicated too.
Different companies, different years, different speeds.
What a headache.

The good Doctor says to take two, fiddle w/ your bikes, and ride it in
the morning.


Sheldon Brown calls it cold-setting-
It's not Rocket Surgery, it's fiendRacing!

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