Chainring compatibility

Tom Anderson

Hello!

I'm very confused about chainrings. This is a combination of ignorance and
a cold.

I have a mountain bike, which i have never taken anywhere near a mountain,
unless you count Muswell Hill, or possibly the hills to the north of
Exeter. I ride it to work mostly. It's got triple chainrings and a 9-speed
cassette, both of which i need to replace. The chainrings are in the shape
of a one-piece rivetted Suntour unit, so i'm replacing the entire crankset
(with something with bolts).

I'm planning to replace the cassette like-for-like, 11-32 or 11-34 or
something.

I could get a straight replacement for my current crankset, ie something
with 22/32/44 rings, like one of these:

http://wiggle.co.uk/ProductDetail.a...ered%20Chainset
http://wiggle.co.uk/ProductDetail.a...ISIS%20Chainset

But given the lack of actual mountains on my typical rides, i was thinking
i might get something a bit more tourer-like. I was thinking of a 38-tooth
middle ring, and then i suppose a 48-tooth big. Still with the 22-tooth
little ring for when i do find steep hills, if that makes any sense (22 to
38 - yikes).

I can't find a crankset that comes with a configuration like that. They
probably exist, but i couldn't track any down. No matter, though, i can
just buy a suitable middle (and possibly big) ring and fit it.

This is where the confusion sets in. How do i know if a chainring is going
to be compatible? I can tell if it's got the right number of bolt holes,
and that it has a compatible bolt circle diameter. But do chainrings vary
in their suitability for use in a triple, and with a 9-speed back end? For
instance, could i use any of these:

http://www.dmrbikes.com/?Section=pr...temid=CRSHR3840
http://www.chainreactioncycles.com/...px?ModelID=1932

Or not? Any ideas?

I'm starting to think i might be better off with a 22/32/44 crankset, and
a road cassette, purely because it's more comprehensible. That would let
me use a medium-cage mech, too, which i have heard might give me better
shifting.

Also, is anyone at all familiar with FSA's RPM range? Chain Reaction have
no fewer than four models of their cranksets in the 24-35 quid range:

http://www.chainreactioncycles.com/...px?ModelID=7601
http://www.chainreactioncycles.com/...px?ModelID=6972
http://www.chainreactioncycles.com/...px?ModelID=7604
http://www.chainreactioncycles.com/...px?ModelID=7607

Which seems excessive. None of which are the same as the FSA crankset on
Wiggle, above!

tom

--
Eat whip you steroid wall-bashing lug-head! -- The Laird

Martin

Tom Anderson wrote:
> Hello!
>
> I'm very confused about chainrings. This is a combination of ignorance
> and a cold.

You if you are going for a larger chainset, you might also need to
replace the front mech as well.

If I were going to do what you are suggesting, I would purchase the same
make of chainrings and chainset, just to make sure about compatibility.

Pete Biggs

Tom Anderson wrote:
> Hello!
>
> I'm very confused about chainrings. This is a combination of
> ignorance and a cold.
>
> I have a mountain bike, which i have never taken anywhere near a
> mountain, unless you count Muswell Hill,

I do.

> or possibly the hills to the
> north of Exeter. I ride it to work mostly. It's got triple chainrings
> and a 9-speed cassette, both of which i need to replace. The
> chainrings are in the shape of a one-piece rivetted Suntour unit, so
> i'm replacing the entire crankset (with something with bolts).
>
> I'm planning to replace the cassette like-for-like, 11-32 or 11-34 or
> something.
>
> I could get a straight replacement for my current crankset, ie
> something with 22/32/44 rings, like one of these:
>
> http://wiggle.co.uk/ProductDetail.a...ered%20Chainset
> http://wiggle.co.uk/ProductDetail.a...ISIS%20Chainset
>
> But given the lack of actual mountains on my typical rides, i was
> thinking i might get something a bit more tourer-like. I was thinking
> of a 38-tooth middle ring, and then i suppose a 48-tooth big. Still
> with the 22-tooth little ring for when i do find steep hills, if that
> makes any sense (22 to 38 - yikes).

Not a bad idea in theory, but you will find 24-38-48 more practical in terms
of derailleur setting up and performance, and crankset compatibility. 24t
is the minimum that will fit 74mm that Shimano and Campagnolo road triple
chainsets use, for example.

> I can't find a crankset that comes with a configuration like that.
> They probably exist, but i couldn't track any down. No matter,
> though, i can just buy a suitable middle (and possibly big) ring and
> fit it.
> This is where the confusion sets in. How do i know if a chainring is
> going to be compatible? I can tell if it's got the right number of
> bolt holes, and that it has a compatible bolt circle diameter. But do
> chainrings vary in their suitability for use in a triple,

Rings designed for doubles can be fitted to triple chainsets when the BCD is
compatible. There are middle-specific rings that have ramps and pins to
help the chain shift up from the inner ring. See the TA ones from
www.dotbike.com. These are not always necessary, though, depending on your
shifters and mechs and what you're prepared to tolerate.

> and with a 9-speed back end?

Any 7, 8 or 9 speed chainset would be fine with a 9-speed chain. A 10-speed
one would be too, though sometimes chainring spacers (washers) are needed to
prevent rubbing in certain reasonable gear combinations.

> I'm starting to think i might be better off with a 22/32/44 crankset,
> and a road cassette, purely because it's more comprehensible. That
> would let me use a medium-cage mech, too, which i have heard might
> give me better shifting.

The important things to decide first are the bottom gear you want, and the
size of the jumps between the rear gears. The rest then can and will be
compromised by component availability and limitations.

~PB

Tom Anderson

On Mon, 2 Jun 2008, Martin wrote:

> Tom Anderson wrote:
>
>> I'm very confused about chainrings. This is a combination of ignorance and
>> a cold.
>
> You if you are going for a larger chainset, you might also need to replace
> the front mech as well.

good point. bugger.

> If I were going to do what you are suggesting, I would purchase the same
> make of chainrings and chainset, just to make sure about compatibility.

ah, but where's the fun in that?

tom

--
102 FX 6 (goblins)

Tom Anderson

On Mon, 2 Jun 2008, Pete Biggs wrote:

> Tom Anderson wrote:
>
>> But given the lack of actual mountains on my typical rides, i was
>> thinking i might get something a bit more tourer-like. I was thinking
>> of a 38-tooth middle ring, and then i suppose a 48-tooth big. Still
>> with the 22-tooth little ring for when i do find steep hills, if that
>> makes any sense (22 to 38 - yikes).
>
> Not a bad idea in theory, but you will find 24-38-48 more practical in
> terms of derailleur setting up and performance, and crankset
> compatibility. 24t is the minimum that will fit 74mm that Shimano and
> Campagnolo road triple chainsets use, for example.

Aha. I'd been thinking in terms of fitting big rings on a 104/64 MTB
spider, but a road version might make more sense.

>> This is where the confusion sets in. How do i know if a chainring is
>> going to be compatible? I can tell if it's got the right number of bolt
>> holes, and that it has a compatible bolt circle diameter. But do
>> chainrings vary in their suitability for use in a triple,
>
> Rings designed for doubles can be fitted to triple chainsets when the
> BCD is compatible. There are middle-specific rings that have ramps and
> pins to help the chain shift up from the inner ring. See the TA ones
> from www.dotbike.com. These are not always necessary, though, depending
> on your shifters and mechs and what you're prepared to tolerate.

Righto.

>> and with a 9-speed back end?
>
> Any 7, 8 or 9 speed chainset would be fine with a 9-speed chain. A
> 10-speed one would be too, though sometimes chainring spacers (washers)
> are needed to prevent rubbing in certain reasonable gear combinations.

Okay.

I take it that if a crankset says it's 8-speed, it's not going to work
well with a 9-speed cassette?

>> I'm starting to think i might be better off with a 22/32/44 crankset,
>> and a road cassette, purely because it's more comprehensible. That
>> would let me use a medium-cage mech, too, which i have heard might
>> give me better shifting.
>
> The important things to decide first are the bottom gear you want, and
> the size of the jumps between the rear gears. The rest then can and
> will be compromised by component availability and limitations.

Fair enough.

Anyway, it turns out there are basically no 9-speed cranksets in the size
range i want which fit a square tapered bottom bracket - nobody makes one,
full stop. So, perhaps time for a new bottom bracket, which means a new
post ...

tom

--
102 FX 6 (goblins)

Pete Biggs

Tom Anderson wrote:

> I take it that if a crankset says it's 8-speed, it's not going to work
> well with a 9-speed cassette?

It will work fine. The crankset doesn't know or care what cassette you have
on the bike. You can use a 9-speed chain on an 8-speed chainset because the
*internal* width (size of holes in middle) of 7, 8, 9 and 10-speed chains is
about the same.

/snip
> Anyway, it turns out there are basically no 9-speed cranksets in the
> size range i want

Does that mean with an inner ring smaller than 24t? Otherwise I'm sure you
could find one that could take 24/39/48. 8 and 10-speed cranks would be OK
too.

> which fit a square tapered bottom bracket - nobody
> makes one, full stop. So, perhaps time for a new bottom bracket,
> which means a new post ...

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.

As mentioned by another poster, you will need to think about the front
derailleur too and what size rings it can cope with. If you change the
front mech, then you need to think about compatibility with the shifter as
well.

Have you thought about getting a whole new bike? ;-)

~PB

Tom Anderson

On Tue, 3 Jun 2008, Pete Biggs wrote:

> Tom Anderson wrote:
>
>> I take it that if a crankset says it's 8-speed, it's not going to work
>> well with a 9-speed cassette?
>
> It will work fine. The crankset doesn't know or care what cassette you
> have on the bike. You can use a 9-speed chain on an 8-speed chainset
> because the *internal* width (size of holes in middle) of 7, 8, 9 and
> 10-speed chains is about the same.

Ah, so it's to do with the size of the chain, rather than anything about
alignment of the chainrings and sprockets? 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?

>> Anyway, it turns out there are basically no 9-speed cranksets in the
>> size range i want
>
> Does that mean with an inner ring smaller than 24t? Otherwise I'm sure
> you could find one that could take 24/39/48. 8 and 10-speed cranks
> would be OK too.

I could not find a 24/38/48 or similar, in 9-speed, to fit a square
tapered BB. Not a sausage. But if the 8-speed ones work, then fine, no
problem.

>> which fit a square tapered bottom bracket - nobody makes one, full
>> stop. So, perhaps time for a new bottom bracket, which means a new post
>> ...
>
> 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 ...

> As mentioned by another poster, you will need to think about the front
> derailleur too and what size rings it can cope with. If you change the
> front mech, then you need to think about compatibility with the shifter
> as well.
>
> Have you thought about getting a whole new bike? ;-)

*SOB*

tom

--
102 FX 6 (goblins)

Pete Biggs

Tom Anderson wrote:
> On Tue, 3 Jun 2008, Pete Biggs wrote:
>
>> Tom Anderson wrote:
>>
>>> I take it that if a crankset says it's 8-speed, it's not going to
>>> work well with a 9-speed cassette?
>>
>> It will work fine. The crankset doesn't know or care what cassette
>> you have on the bike. You can use a 9-speed chain on an 8-speed
>> chainset because the *internal* width (size of holes in middle) of
>> 7, 8, 9 and 10-speed chains is about the same.
>
> Ah, so it's to do with the size of the chain, rather than anything
> about alignment of the chainrings and sprockets?

Yes, because aligment is pretty much the same with 7 to 10-speed systems.
Although the question does make me wonder about using a road chainset on an
MTB. An alternative BB would fix that *if* it was a problem anyway. (Road
chainsets tend tobe designed for 130mm hubs, MTB for 135mm).

> 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

>>> Anyway, it turns out there are basically no 9-speed cranksets in the
>>> size range i want
>>
>> Does that mean with an inner ring smaller than 24t? Otherwise I'm
>> sure you could find one that could take 24/39/48. 8 and 10-speed
>> cranks would be OK too.
>
> I could not find a 24/38/48 or similar, in 9-speed, to fit a square
> tapered BB. Not a sausage.

Campag and most Shimano road triples can take rings of that size (or 39t
middle for Campag), and I bet someone somewhere has a 9-speed model for
sale. Replacement rings are available. Selling the original rings would
help pay for them.

> But if the 8-speed ones work, then fine, no problem.

Yep. And 10-speed (though possibly requiring spacers).

>> 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?

Can be, yes.

I dunno about Truativ's.

/snip
>> Have you thought about getting a whole new bike? ;-)
>
> *SOB*

Seriously, it's very satisfiying to finally have gears that really suit you
(and it's worth some trial and error too), so don't give up your ideas yet.

~PB

Pete Biggs

Tom Anderson wrote:
> I could not find a 24/38/48 or similar, in 9-speed, to fit a square
> tapered BB. Not a sausage. But if the 8-speed ones work, then fine, no
> problem.

Here we go, I found one at the very first place I looked up:

http://www.dotbike.com/ProductsP2013.aspx?TRACK%3dDDI

This may not necessarily be the best or cheapest for your bike, but it is a
9-speed square-taper job that can take 24/39/48 rings. See the TA 135 and
74mm rings on that site. They costalot but last well. You will need to
change your BB, but suitable BBs are cheap.

You would increase chance of compatibility with existing front mech if using
an even smaller big ring, say 46t. You could freewheel down Muswell Hill!

Note. I only go on about road bike stuff so much because that's what I know
best.

~PB

Dave Larrington

In news:Pine.LNX.4.64.0806031925470.16276@urchin.earth.li,
Tom Anderson <twic@urchin.earth.li> tweaked the Babbage-Engine to tell us:

> I could not find a 24/38/48 or similar, in 9-speed, to fit a square
> tapered BB. Not a sausage.

TA Carmina / Vega and Middleburn, to name but two, can be mixed 'n' matched
to get just about any combination of rings under the sun, though cheap they
are not. I haz a 20-36-48 TA Carmina on one of the Fleet.

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk>
A complimentary biro(tm) is /not/ to be sniffed at.

Nigel Cliffe

Pete Biggs wrote:
> Tom Anderson wrote:
>> I could not find a 24/38/48 or similar, in 9-speed, to fit a square
>> tapered BB. Not a sausage. But if the 8-speed ones work, then fine,
>> no problem.
>
> Here we go, I found one at the very first place I looked up:
>
> http://www.dotbike.com/ProductsP2013.aspx?TRACK%3dDDI
>
> This may not necessarily be the best or cheapest for your bike, but
> it is a 9-speed square-taper job that can take 24/39/48 rings.

Someone can correct this if I'm wrong, but I thought that Campag square
taper is subtly different to Shimano square taper, so theoretically each
needs different bottom bracket.


- Nigel


--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

Alan Braggins

In article <g25r88$rou$1@news.albasani.net>, Nigel Cliffe wrote:
>Someone can correct this if I'm wrong, but I thought that Campag square
>taper is subtly different to Shimano square taper, so theoretically each
>needs different bottom bracket.

http://www.sheldonbrown.com/bbtaper.html has the details

Just zis Guy, you know?

On 04 Jun 2008 13:14:21 +0100 (BST), armb@chiark.greenend.org.uk
(Alan Braggins) said in
<slrng4d1ot.8ns.armb@chiark.greenend.org.uk>:

>http://www.sheldonbrown.com/bbtaper.html has the details

Such a shame that we can no longer perform the Summoning and get the
answer from the great man himself.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

85% of helmet statistics are made up, 69% of them at CHS, Puget Sound

Tom Anderson

On Tue, 3 Jun 2008, Pete Biggs wrote:

> Tom Anderson wrote:
>> On Tue, 3 Jun 2008, Pete Biggs wrote:
>>
>>> Tom Anderson wrote:
>>>
>>>> I take it that if a crankset says it's 8-speed, it's not going to
>>>> work well with a 9-speed cassette?
>>>
>>> It will work fine. The crankset doesn't know or care what cassette
>>> you have on the bike. You can use a 9-speed chain on an 8-speed
>>> chainset because the *internal* width (size of holes in middle) of
>>> 7, 8, 9 and 10-speed chains is about the same.
>>
>> Ah, so it's to do with the size of the chain, rather than anything
>> about alignment of the chainrings and sprockets?
>
> Yes, because aligment is pretty much the same with 7 to 10-speed systems.
> Although the question does make me wonder about using a road chainset on an
> MTB. An alternative BB would fix that *if* it was a problem anyway. (Road
> chainsets tend tobe designed for 130mm hubs, MTB for 135mm).
>
>> 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.

Did you mean P >= N and N <=> M?

>>> Have you thought about getting a whole new bike? ;-)
>>
>> *SOB*
>
> Seriously, it's very satisfiying to finally have gears that really suit
> you (and it's worth some trial and error too), so don't give up your
> ideas yet.

Cheers, i'm trying to stay strong!

tom

--
20 Minutes into the Future