Help required choosing Chainrings/Chainset

Good info on chains.

http://www.bikeparts.com/ProductInfo/Chains.html

nobody760 said:

Good info on chains.
http://www.bikeparts.com/ProductInfo/Chains.html

Thanks for the reply, but I don't really have a problem with chains, I've
used the higher-end Sachs/Sram chains for ages now (the powerlink is great!)

My real problem is in determining what would be a compatible chainset to
replace my current one with.

Are 9-speed chainsets really incompatible with 7/8 speed drivetrains?

AJ

AJ MacLeod said:

Are 9-speed chainsets really incompatible with 7/8 speed drivetrains?

By "drivetrain", I assume you mean "cassette" (the cluster of sprockets
on the rear wheel), since the chainset is part of the drivetrain
(drivetrain = chain, chainrings, cranks, pedals, bottom bracket,
cassette [rear sprockets], rear hub, front and rear derailleurs).

Anyway, there shouldn't be a problem using a 9-speed chainset with a
7/8-speed cassette, rear mech and chain.

A 9-speed cassette has sprockets that are narrower and closer together,
so you would need a narrower chain, but /I believe/ the chainring
spacing on a 9-speed chainset is no different to that of a 8-speed
chainset - the difference is that the 9-speed chainset will have
slightly thinner chainrings.

d.

davek said:

Anyway, there shouldn't be a problem using a 9-speed chainset with a
7/8-speed cassette, rear mech and chain.

I suppose this is probably what I most want to confirm. In various online
catalogues they state that the 9-speed chainsets are not compatible with
7/8 speed cassettes; does anyone know differently from experience?

Quoted message said:

A 9-speed cassette has sprockets that are narrower and closer together, so
you would need a narrower chain, but /I believe/ the chainring spacing on
a 9-speed chainset is no different to that of a 8-speed chainset - the
difference is that the 9-speed chainset will have slightly thinner
chainrings.

Yes, I guessed that 9-speed likely used thinner rings/sprockets than 7/8
speed. I can't help wondering though how well a 7/8 speed chain (sachs
PC58 is what I use) would sit on the narrower rings - and whether it would
tend to wear badly? Has anyone tried? I just don't really want to spend
a significant (to me) sum on something if it's not going to work right.

Cheers,

AJ

AJ MacLeod said:

I can't help wondering though how well a 7/8 speed chain (sachs
PC58 is what I use) would sit on the narrower rings - and whether it

would

Quoted message said:

tend to wear badly?

According to Jobst Brandt:
"Chain wear depends almost entirely on cleanliness and lubrication
rather than being a load problem. For bicycles the effect of load
variations is insignificant compared to the lubricant and grit
effects."

Full article here:
<url:http://sheldonbrown.com/brandt/chain-care.html>

Quoted message said:

Has anyone tried? I just don't really want to spend
a significant (to me) sum on something if it's not going to work

right.

I think it will work fine. But don't quote me on that. ;-)

d.

AJ MacLeod said:

davek said:

Anyway, there shouldn't be a problem using a 9-speed chainset with a
7/8-speed cassette, rear mech and chain.

I suppose this is probably what I most want to confirm. In various
online catalogues they state that the 9-speed chainsets are not
compatible with 7/8 speed cassettes; does anyone know differently
from experience?

I've used 9 and 10 speed Campag chainsets & rings with 8 and 9 speed
chains respecitively, without problems, and from what I remember from
previous posters, it's not a problem with Shimano either.

Quoted message said:

Quoted message said:

A 9-speed cassette has sprockets that are narrower and closer
together, so you would need a narrower chain, but /I believe/ the
chainring spacing on a 9-speed chainset is no different to that of a
8-speed chainset - the difference is that the 9-speed chainset will
have slightly thinner chainrings.

Yes, I guessed that 9-speed likely used thinner rings/sprockets than
7/8 speed. I can't help wondering though how well a 7/8 speed chain
(sachs PC58 is what I use) would sit on the narrower rings - and
whether it would tend to wear badly?

There's no problem with drive or wear becuase the *internal* width of 8
and 9 speed chain is almost the same. It's the overall width that's
different and the chainring teeth don't "know" or care about that. It's
just a question of whether a chain that's wider than the chainset was
designed for jams or rubs on adjacent rings, that's all, and that probably
won't happen.

If worst comes to the worst, you can use a 9-speed chain, which will
engage with 7/8 speed sprockets, just /might/ not change gear quite so
well.

Sorry I don't know more about your chainset. It might help if you specify
the ring sizes (count the teeth), measure distance between two adjacent
chainring bolt holes (centre to centre, inner and outer rings) and find a
model number if one is marked on back of crank or something, and then post
all that info to rec.bicycles.tech and search the net for the model
number.

If you get the same ring sizes again, it's bound to be compatible with
your front mech. I think the only issue will be bottom bracket
compatibility, and perhaps it'll be worth changing that anyway (to UN73,
for example).

~PB

Pete Biggs said:

I've used 9 and 10 speed Campag chainsets & rings with 8 and 9 speed
chains respecitively, without problems, and from what I remember from
previous posters, it's not a problem with Shimano either.

That's reassuring!

Quoted message said:

There's no problem with drive or wear becuase the *internal* width of 8
and 9 speed chain is almost the same. It's the overall width that's
different and the chainring teeth don't "know" or care about that.

This is what I hadn't suspected. I can't imagine the tolerances between
rings being so fine on a chainset that they would cause problems, so I
think I'll go the 9-speed replacement chainset route. There doesn't seem
to be the glut of "new-old stock" of 7/8 speed chainsets going cheaply
that I had hoped for!

Quoted message said:

If you get the same ring sizes again, it's bound to be compatible with
your front mech. I think the only issue will be bottom bracket
compatibility, and perhaps it'll be worth changing that anyway (to UN73,
for example).

You may be right; despite being convinced it should have failed years
ago, it feels every bit as good as a new one. I can't quite remember if I
fitted it myself or if it came with the bike; I know I fitted the chainset
(original was rather horrible) so I probably bought the BB to suit.
Even the semi-decent Shimano cartridge BBs seem to be extremely good from
a wear point of view.

Thanks for all the replies, I think I'll risk the 9-speed chainset option
assuming I don't find any 8spd bargains. I'll let you know if it doesn't
work!

Cheers,
AJ

In article <[email hidden]>,

AJ MacLeod said:

Hi all,

I've reached the stage where I need either two new chainrings
(inner & middle) or a whole new chainset (as the price will probably be
not too different.)

However, having spent ages looking around, I'm pretty confused as to the
amount of possibilities and don't want to waste money on something
incompatible.

I currently have an STX-RC chainset from about '95 or '96 (cranks a sort
of slightly bronzed colour). It has five arms, 170mm long cranks, and
says "Shimano IG chain only." Would I be right in thinking this is a
compact drive chainset? It certainly looks smaller than the definitely
full-sized ones I have lying around. Could anyone recommend a semi-decent
replacement costing less than fifty pounds?

STX-RC is a bit of a problem as the chainrings are specific to that
crank. Best bin it entirely.

It is a compact size though.

To replace it, a Deore crank would be my choice at that money or
possibly a Truvativ Stylo if you can find a square taper crank for that
money which might be doable. I'd bet on you also needing a new bottom
bracket.

DON'T buy an ISIS standard crank - the ISIS splined bottom brackets are
terrible. The axle is larger diameter but to fit it in, the bearings got
smaller. Shimano did the same with their Octalink splined bottom
brackets but they last 2-3 times as long IME.

So, either a square taper Stylo if you can find one, or Deore Octalink
or Square. Possibly even Deore LX if you can find one cheap enough. Some
of the Truvativ cranks are good for the money under £50 too. They tend
to have good chainrings but watch out for ISIS.

170mm might be tricky though as pretty much all cranks moved up to
175mm. Unless you've got really short legs, I doubt you'll notice the
difference.

Have a search on Bikepimp...

http://www.bikepimp.co.uk/

Shaun

Shaun Murray said:

Have a search on Bikepimp...
http://www.bikepimp.co.uk/

Thanks, that's an excellent link; I was using froogle before, but I think
that one's better.

Quoted message said:

STX-RC is a bit of a problem as the chainrings are specific to that
crank. Best bin it entirely.

Really? I was planning on retiring it - the crank arms suffered from a
few years of commuting through the worst of Aberdonian winters - the
corrosive gunk off the roads ate away at them terribly, even though I was
cleaning the bike meticulously every week.

Quoted message said:

To replace it, a Deore crank would be my choice at that money or
possibly a Truvativ Stylo if you can find a square taper crank for that
money which might be doable. I'd bet on you also needing a new bottom
bracket.

I was thinking that, but I can't detect any undue noise, roughness or play
in the bearings. It's not that big a deal to change it, so I think I'll
keep my current one till it dies, unless I need a new one for my new
chainset.

Quoted message said:

DON'T buy an ISIS standard crank - the ISIS splined bottom brackets are
terrible. The axle is larger diameter but to fit it in, the
bearings got
smaller. Shimano did the same with their Octalink splined bottom
brackets but they last 2-3 times as long IME.

I've not been following the fads of the mountain bike world for a while
and didn't realise until I started searching that these new splined BBs
were all the rage. I'm very impressed with the "conventional" Shimano
cartridge BBs - probably pretty heavy, but well worth it for the
longevity. The days of losing bearings on the floor and getting covered
with grease seem to be well and truly gone, thankfully!

Quoted message said:

170mm might be tricky though as pretty much all cranks moved up to
175mm. Unless you've got really short legs, I doubt you'll notice the
difference.

On the road probably not (I'm not that tall, but not THAT short either -
5'7 or 8 ish) - but I'm keen on preserving any ground clearance I can for
the off-road riding I do (rutted tracks, particularly.) I know it's a
very small difference, and possibly psychological, but even so...

Cheers for the advice

AJ

Shaun Murray wrote:

..............

Quoted message said:

Quoted message said:

I currently have an STX-RC chainset from about '95 or '96 (cranks a
sort of slightly bronzed colour). It has five arms

..............

Quoted message said:

STX-RC is a bit of a problem as the chainrings are specific to that
crank.

Why is that? The BCD (PCD) of the '97 model isn't unique, according to:
www.bikepro.com/products/shimano_tables/shim_frtchnwhl_table.html . Is
there any problem other than the BCD or was the '96/95 version different?

5-arm rings post-free from www.settlecycles.co.uk/shop :
TA 58mm: £13.99
TA 94mm: £16.99 to £26.99

BCD can be worked out using the table here:
http://www.sheldonbrown.com/gloss_bo-z.html

Quoted message said:

170mm might be tricky though as pretty much all cranks moved up to
175mm.

Deore and LX* cranks are still made in 170mm as well as 175mm.

* and probably all the rest for all I know. Check via:
See http://www.shimano-europe.com/cycling/

~PB

Pete Biggs said:

Why is that? The BCD (PCD) of the '97 model isn't unique,
according to:
www.bikepro.com/products/shimano_tables/shim_frtchnwhl_table.html
Is there any problem other than the BCD or was the '96/95
version different?

The early STX-RC cranks had an odd chainring attachment. The crank had a
58mm bcd. The inner and middle rings mounted directly to the crank, and the
large chainring bolted to the middle one:

http://bernd.sluka.de/Fahrrad/Shimano/TM/FC-MC33_1995.gif

Later models were more conventional, but the inner ring attached to the
middle, rather than directly to the crank:

http://bernd.sluka.de/Fahrrad/Shimano/TM/FC-MC36-S_1997.gif

James Thomson

James Thomson said:

The early STX-RC cranks had an odd chainring attachment. The crank had a
58mm bcd. The inner and middle rings mounted directly to the crank, and
the large chainring bolted to the middle one:

http://bernd.sluka.de/Fahrrad/Shimano/TM/FC-MC33_1995.gif

This is what I have, in what must be "chromica" finish. Looked very nice
until the salt etc ate it! The chainset was a pretty good buy, really - I
got it cheap because it was at least one "model year" old, and it's given
sterling service up till now.

Cheers,

AJ

In article <[email hidden]>,

AJ MacLeod said:

Really? I was planning on retiring it - the crank arms suffered from a
few years of commuting through the worst of Aberdonian winters - the
corrosive gunk off the roads ate away at them terribly, even though I was
cleaning the bike meticulously every week.

James has already posted why the chainrings are fun. Pace used to do an
STX-RC to normal compact BCD convertor but not for quite a while. Don't
think I've seen one for at least 8 years.

Quoted message said:

Quoted message said:

To replace it, a Deore crank would be my choice at that money or
possibly a Truvativ Stylo if you can find a square taper crank for that
money which might be doable. I'd bet on you also needing a new bottom
bracket.

I was thinking that, but I can't detect any undue noise, roughness or play
in the bearings. It's not that big a deal to change it, so I think I'll
keep my current one till it dies, unless I need a new one for my new
chainset.

I was more thinking along the lines of needing to replace it because the
axle length of an STX-RC crank is unlikely to be the same as a modern
crank. Most of the recent Shimano cranks take 113mm bottom brackets.

That's without the issue of splined or not.

However, if you've had the same BB all the time on the same crank, I'd
be very surprised if it's not needing a replacement.

Shaun