Crankset compatibilty

[Spikejns]

I am new to biking, well I have reentered biking and wow have things changed. Anyway I Have a Trek bike and have purchased a new crank set Alivio and it xcame with a large 42 tooth chainring. I would like to get a 44 tooth. What do i need to be aware of for getting the correct chainring & what chains work with it and lastly I am also considering a new front derailleur also a Shimano XTR M952 that will fit my bike as far as the tube diameter goes, but will it work with the above crankset and chainring change?

 

[alfeng]

I am new to biking, well I have reentered biking and wow have things changed. Anyway I Have a Trek bike and have purchased a new crank set Alivio and it xcame with a large 42 tooth chainring. I would like to get a 44 tooth. What do i need to be aware of for getting the correct chainring & what chains work with it and lastly I am also considering a new front derailleur also a Shimano XTR M952 that will fit my bike as far as the tube diameter goes, but will it work with the above crankset and chainring change?

99% probability that you need a 104 BCD 4-arm chainring ... but, if you're getting a larger chainring, you may want to consider a 46t (or, even a 48t) chainring.

Unless you damaged the bike's front derailleur, you will probably not see/feel any difference in shifting that some proper maintenance wouldn't give you.

 

[Spikejns]

Yes what I read on the crankset is that it has a 104 bolt pattern and I have a new chain. I am assuming I will need more links. The New Front Derailuer I am considering (Shimano XTR M952) says it is compatible with a 9 speed chain. If I read correctly a 9 speed chain has a narrow profile to match the 9 speed rear cogs, but I don't see how it would effect the front derailuer. Also are the chainrings different for different chains? The chain I have is a Shimano CN-IG70. I believe it is a standard width chain.

 

[alfeng]

Yes what I read on the crankset is that it has a 104 bolt pattern and I have a new chain. I am assuming I will need more links. The New Front Derailuer I am considering (Shimano XTR M952) says it is compatible with a 9 speed chain. If I read correctly a 9 speed chain has a narrow profile to match the 9 speed rear cogs, but I don't see how it would effect the front derailuer. Also are the chainrings different for different chains? The chain I have is a Shimano CN-IG70. I believe it is a standard width chain.

Are you updating your bike from whatever-speed to a 9-speed drivetrain en toto? Do you already have the 9-speed cassette? Do you already have the 9-speed shifters? Which rear derailleur are you using? Just how old is your Trek?

WHY did you choose-and-buy the ALIVIO crankset, and what is it replacing?

Regardless, MY rule-of-thumb is to MATCH THE CHAIN TO THE CASSETTE, FIRST ... AND, THE FRONT DERAILLEUR TO THE CHAIN when using Shimano indexed shifting ...

The rear derailleur generally doesn't care whether you are using a narrower chain (e.g., 10-speed); but generally, 10-speed chains cost more than comparable (same brand & group 'grade') 9-speed chains, and 9-speed chains generally cost more than 8-speed chains.

The difference in the chains is in the EXTERNAL width of the links ... it is small, but it will make a difference when indexing a triple crankset.

The distance between the plates on a front derailleur varies based on the width of the chain it is spec'd to use. The indexing moves the cable a certain length, and therefore moves the front derailleur cage a certain amount. If the distance between the plates of the front cage is too wide for the chain that you are using, then the chain will not be moved sufficiently ... and, the converse is true whereby too narrow a distance & too wide a chain will move the chain too much.

BUT, having said that, I will say that if you maintain near-perfect adjustment on your rear derailleur, you may be able to use some 8-speed chains with a 9-speed Shimano cassette.

If properly adjusted, I doubt that you would notice any difference in how an ALIVIO front derailleur shifts when compare with the shifting of an XTR front derailleur -- the difference in Shimano's front derailleurs is very small to the point of being mostly cosmetic -- presuming you are comparing "like" front deralleurs (that is, either 8-or-9-speed, respectively). Why pay more? If you don't want an ALIVIO, get an LX or XT from the "same" generation of components as the rest of the drivetrain.

While you theoretically need one-more-inch in the length of the chain compared with your existing chain if you switch to a 44t from a 42t, you may not need a longer chain ... it depends how much slack is currently in the chain that is on the bike ... AND, if your bike is old enough to have horizontal dropouts, then there is more latitude in the chain length.

Shimano (and, others) does have different chainrings for optimum shifting with the various drivetrains ... try what you have before changing; but, be aware that the mating the chain & front derailleur will have a greater impact on the shifting than any ramping-and-pinning which may-or-may-not exist ...

So, if you have your heart set on that XTR 952 front derailleur [BTW. This might be stating the obvious, but there are at least three types of XTR front derailleurs based on the direction the cable pulls from AND the swing], you definitely want a 9-speed chain regardless of whether your current cassette is 7-or-8-speed.

Of course, others may disagree!?!

 

[Spikejns]

Are you updating your bike from whatever-speed to a 9-speed drivetrain en toto? Do you already have the 9-speed cassette? Do you already have the 9-speed shifters? Which rear derailleur are you using? Just how old is your Trek?

WHY did you choose-and-buy the ALIVIO crankset, and what is it replacing?

Regardless, MY rule-of-thumb is to MATCH THE CHAIN TO THE CASSETTE, FIRST ... AND, THE FRONT DERAILLEUR TO THE CHAIN when using Shimano indexed shifting ...

The rear derailleur generally doesn't care whether you are using a narrower chain (e.g., 10-speed); but generally, 10-speed chains cost more than comparable (same brand & group 'grade') 9-speed chains, and 9-speed chains generally cost more than 8-speed chains.

The difference in the chains is in the EXTERNAL width of the links ... it is small, but it will make a difference when indexing a triple crankset.

The distance between the plates on a front derailleur varies based on the width of the chain it is spec'd to use. The indexing moves the cable a certain length, and therefore moves the front derailleur cage a certain amount. If the distance between the plates of the front cage is too wide for the chain that you are using, then the chain will not be moved sufficiently ... and, the converse is true whereby too narrow a distance & too wide a chain will move the chain too much.

BUT, having said that, I will say that if you maintain near-perfect adjustment on your rear derailleur, you may be able to use some 8-speed chains with a 9-speed Shimano cassette.

If properly adjusted, I doubt that you would notice any difference in how an ALIVIO front derailleur shifts when compare with the shifting of an XTR front derailleur -- the difference in Shimano's front derailleurs is very small to the point of being mostly cosmetic -- presuming you are comparing "like" front deralleurs (that is, either 8-or-9-speed, respectively). Why pay more? If you don't want an ALIVIO, get an LX or XT from the "same" generation of components as the rest of the drivetrain.

While you theoretically need one-more-inch in the length of the chain compared with your existing chain if you switch to a 44t from a 42t, you may not need a longer chain ... it depends how much slack is currently in the chain that is on the bike ... AND, if your bike is old enough to have horizontal dropouts, then there is more latitude in the chain length.

Shimano (and, others) does have different chainrings for optimum shifting with the various drivetrains ... try what you have before changing; but, be aware that the mating the chain & front derailleur will have a greater impact on the shifting than any ramping-and-pinning which may-or-may-not exist ...

So, if you have your heart set on that XTR 952 front derailleur [BTW. This might be stating the obvious, but there are at least three types of XTR front derailleurs based on the direction the cable pulls from AND the swing], you definitely want a 9-speed chain regardless of whether your current cassette is 7-or-8-speed.

Of course, others may disagree!?!

To make a long story short My sons bike had a bent crank set so I bought the crank set for his. When I got the new crank set in I decided to put my old crank on his bike moved the Sakae off my bike to his and am looking to put the Alivio on mine. Would love a 48 tooth chainring if possible but not sure what or where to buy. Looking for the chainring I found a great deal on the Shimano XTR M952 1-1/8" top pull, which is what I need for $20.00 new . Seemed like a steal. While I don't currently have indexed shifters I would consider changing them down the road. Currently I can adjust my shifters to get the best front derailleur position. (No indexing). So what your are saying is that a 9 speed chain is what I need for this front derailluer. and it would work with my old 7 speed rear cog. If I continued to up grade down the road a 9 speed rear cog & 9 speed indexed shifter for the back would be next or possibly a 3 speed index shifter for the front. then the rearcog... Do you need to match the rear derailluer? Thanks for your insights.

 

[alfeng]

...

Would love a 48 tooth chainring if possible but not sure what or where to buy. Looking for the chainring I found a great deal on the Shimano XTR M952 1-1/8" top pull, which is what I need for $20.00 new .

... So what your are saying is that a 9 speed chain is what I need for this front derailluer. and it would work with my old 7 speed rear cog. If I continued to up grade down the road a 9 speed rear cog & 9 speed indexed shifter for the back would be next or possibly a 3 speed index shifter for the front. then the rearcog... Do you need to match the rear derailluer?

Shimano makes a 48t 104BCD "touring" chainring in both steel & aluminum. If your bike shop can't get them for you, you can get them through eBay (the steel "set" that includes the middle & granny is less than $20 from one eBay retailer ... the single 48t alloy ring is probably 2x that much at your LBS).

You can use a narrower chain on the rear than the original. The Shimano 8-speed chain is essentially the same as the old SEDIS 'narrow' chain ... and, the latter was certainly okay with a 5-speed freewheel.

It is much better, IMO, to match the front derailleur to the chain AND vice-versa ... but, for the time being, you can probably continue to use whatever chain you currently have since you are NOT currently using indexed shifting. If/When you do opt for indexed shifting, you'll definitely want to get a 9-speed chain regardless of whether you choose an 8-speed or 9-speed indexed drivetrain.

You do not need to match the rear derailleur Almost ANY Shimano rear derailleur can be used with almost any Shimano drivetrain ... the rear derailleur anchoring needs to be different if you get a 10-speed rear derailleur, but it is otherwise compatible. The so-called RAPID RISE (reverse pull) can be used in place of the "regular" rise rear derailleurs. Only the pre-1985 (give-or-take) are incompatible with the indexing; so, let your budget be your guide.

FWIW. I'm currently inclined to devolving some of my bikes to only 8-speeds (my dust-covered MTB still only has 8-speeds) ... the advantage of having 9-or-10-speeds is negligible for the average rider. The 8-speed shifters will work with a many/(if not all) 7-speed freewheels & all 7-speed cassettes ... so, if you find some 8-speed shifters at a good price, then you may want to give them serious consideration.

BTW. Yeah, $20 for a new XTR front derailleur is a very good deal!