Chainring compatibility

Pete Biggs

Tom Anderson wrote:

>>> You can use any
>>> combination of an N-speed crankset, M-speed cassette and P-speed
>>> chain as long as P >= N and P >= M?
>>
>> P <=> N and P>= M
>
> P <=> N?
>
> And presumably N <=> M?
>
> That would mean describing a crankset as '9-speed' meant nothing at
> all.

It does mean almost nothing to completely nothing in practice. Welcome to
the clashing worlds of marketing and bike customisation. If there are any
dimensional differences between a chainset of one speed and another, they
will be small and usually of no noticeable consequence.

In a rare case where the chainrings close enough together that they cause
chain rub in certain gears on a certain bike with a certain chain, you can
just space the rings further apart with thin washers.

Even *brakes* are sometimes described as "9 speed"! As if they couldn't be
used with 8 or 10-speed systems! Actually it's just because they're part of
a 9-speed groupset and visually match the other components.

~PB

Pete Biggs

Tom Anderson wrote:

> Okay, this:
>
> http://www.ultimatepursuits.co.uk/p...l=1&v=VARFCM410
>
> This isn't far off either:
>
> http://www.ultimatepursuits.co.uk/p...l=1&v=VARFCM532
>
> Both of those presumably fit a JIS square BB, and are in ideologically
> pure 104/64 BCD, rather than any kind of overgrown road madness .

Yes, they look more suitable for your kind of bike.

You could perhaps change the outer ring for a slighter bigger one, but it
may be worth having a lower top gear than you would ideally want in order to
have more suitable bottom and middle gears. This is what I've done on my
own bikes. It is no big deal to have to freewheel down steep hills. I make
do with a 50x14 top gear on my hack-tourer (with 700c wheel).

~PB

Tom Anderson

On Wed, 4 Jun 2008, Pete Biggs wrote:

> Tom Anderson wrote:
>
>>>> You can use any combination of an N-speed crankset, M-speed cassette
>>>> and P-speed chain as long as P >= N and P >= M?
>>>
>>> P <=> N and P>= M
>>
>> P <=> N?
>>
>> And presumably N <=> M?
>>
>> That would mean describing a crankset as '9-speed' meant nothing at
>> all.
>
> It does mean almost nothing to completely nothing in practice. Welcome
> to the clashing worlds of marketing and bike customisation. If there
> are any dimensional differences between a chainset of one speed and
> another, they will be small and usually of no noticeable consequence.

RAGE.

> Even *brakes* are sometimes described as "9 speed"! As if they couldn't
> be used with 8 or 10-speed systems! Actually it's just because they're
> part of a 9-speed groupset and visually match the other components.

Oh, but that actually does make sense. Brakes have to be designed to stop
you at any of the speeds you can go, so if you have a 9-speed groupset,
you need a brake that works at more speeds than if you have an 8-speed
groupset.

Obviously.

tom

--
I had no idea it was going to end in such tragedy

Tom Anderson

On Wed, 4 Jun 2008, Pete Biggs wrote:

> Tom Anderson wrote:
>
>> Okay, this:
>>
>> http://www.ultimatepursuits.co.uk/p...l=1&v=VARFCM410
>>
>> This isn't far off either:
>>
>> http://www.ultimatepursuits.co.uk/p...l=1&v=VARFCM532
>>
>> Both of those presumably fit a JIS square BB, and are in ideologically
>> pure 104/64 BCD, rather than any kind of overgrown road madness .
>
> Yes, they look more suitable for your kind of bike.
>
> You could perhaps change the outer ring for a slighter bigger one, but
> it may be worth having a lower top gear than you would ideally want in
> order to have more suitable bottom and middle gears.

Bear in mind that i currently have a top of 42. Even 48 will be a step up
in the world for me. Any number beginning with a 5 just seems unthinkable.

> This is what I've done on my own bikes. It is no big deal to have to
> freewheel down steep hills. I make do with a 50x14 top gear on my
> hack-tourer (with 700c wheel).

This is also exactly what i'm planning - i want to maintain good
low-speed, poor surface, and hill capability, and i very rarely have a
chance to go >25 mph. Even 20 mph is a bit of a treat, actually.

tom

--
I had no idea it was going to end in such tragedy

Pete Biggs

Tom Anderson wrote:

>> Even *brakes* are sometimes described as "9 speed"! As if they
>> couldn't be used with 8 or 10-speed systems! Actually it's just
>> because they're part of a 9-speed groupset and visually match the
>> other components.
>
> Oh, but that actually does make sense. Brakes have to be designed to
> stop you at any of the speeds you can go, so if you have a 9-speed
> groupset, you need a brake that works at more speeds than if you have
> an 8-speed groupset.
>
> Obviously.

Excellent. There will be jobs in $himaNO's and Crampandgoslow's marketing
departments waiting for you.

~PB

Daniel Barlow

Tom Anderson <twic@urchin.earth.li> writes:

> Oh, but that actually does make sense. Brakes have to be designed to
> stop you at any of the speeds you can go, so if you have a 9-speed
> groupset, you need a brake that works at more speeds than if you have
> an 8-speed groupset.

I want a groupset that goes to 11

-dan

Testing

Tom Anderson wrote:

>> You might need to change the BB anyway even if the new cranks fit a
>> square taper. Different cranks require different axle lengths, and
>> there are two standards of square taper.
>
> Are they different enough that it's really a problem? I have SR Suntour
> cranks now, so i assume a JIS BB; Shimano will fit that, but what about
> Truvativ? Aaargh ...

Sadly yes, I can confirm from experience that they /are/
sufficiently different. I wanted to migrate from a
standard Suntour road double to a compact, bought
an unbranded crankset (I later identified it as
an unbadged Sugino unit) that I then customised with
the rings that I wanted, but when I came to fit it
I found it was so loose on the taper that a proper
fit could not be achieved. I then spent rather too
much on a TA Axix titanium BB (about GBP 70, if I remember
correctly), then found that the crankset didn't engage
fully enough so the chainline was adversely affected.
The most reliable advice I have read (and which I
will follow faithfully should I even need to go
through all this again) is to buy your BB and
crankset from the same manufacturer !

Philip Taylor

Pete Biggs

Tom Anderson wrote:

> On the subject of this whole 8-speed-cranksets-with-9-speed-cassettes
> thing, a friend of mine was highly skeptical. In order to allay his
> fears, and of course not because i have the slightest doubt in you,
> i'm going to get a second opinion from rec.bicycles.tech ...

It's always good to get a second opinion, so I'm not offended at all. I
know what it'll be, though :-) (I learn't a lot from r.b.t).

~PB

Tom Anderson

>> Pete Biggs wrote:
>>
>>> Even *brakes* are sometimes described as "9 speed"! As if they
>>> couldn't be used with 8 or 10-speed systems! Actually it's just
>>> because they're part of a 9-speed groupset and visually match the
>>> other components.

On the subject of this whole 8-speed-cranksets-with-9-speed-cassettes
thing, a friend of mine was highly skeptical. In order to allay his fears,
and of course not because i have the slightest doubt in you, i'm going to
get a second opinion from rec.bicycles.tech ...

tom

--
only positivistic reason and the forms of philosophy based on it are
universally valid -- Pope Benedict XVI