can you mix and match 8 speed 9 speed components?

[chainsaw]

I have a new 8 speed 4500 frame. I will be putting 8 speed components on this bike: a wheelset with an almost new XT 8 speed cassette, 8 speed XT shifters, an almost new 8 speed SRAM chain, an almost new XT front Derailleur (this isn't 8 speed specific I don't think), and an XTR 8 speed rear Derailleur.

I would like to put on a new SHIMANO XT® CRANKSET M752, that is the new Hollowtech one. But before I buy it, I want to be sure this is a good idea, because the JensonUSA description says "Specially designed    chainrings deliver quick and precise shifting with the super-narrow 9 speed    chain"... does this mean I need to avoid using it on my 8  speed system?

[jimbo]

It should work, that's what I'm doing.  Just might not shift as good as a 9-speed chain.

[keen]

  I run an all 8 spd. drivetrain. When it came to my final crankset purchase there seemed to be a big debate as to wether or not the two were compatible. Some said no problem others had shifting woes. I decided the last thing I wanted was poor shifting. I purchased a new 8spd. Coda set off E-bay. Shifting is perfect.

[GaryF52]

I run an LX Mega 9 crankset on an 8 speed setup and it works just fine.  I've also used an LX Mega 9 front derailleur on my 8 speed with no problems.  

With most gripshift shifters you can trim the front derailleur to prevent the chain from rubbing.  Don't know if you can do this with Shimano shifters.

[Phillip]

The 9 speed crank will work just fine. Use a 9 speed Sram chain, it's a little wider than the Shimano's 9 speed.

[Vandal]

I've got a 9-speed RaceFace crankset and everything else is 8-speed.  No problems what-so-ever.  Smooth shifts every time.  If you look at the "9-speed conversion" packages that some on-line bike shops offer, none of them include a new crankset or chainrings (or front derailluer for that matter).  That leads me to believe that standard chainrings can be used with either setup.  Not fact, just a logical conclusion (ie: I may be wrong!).

[Phillip]

Here's Shimano's advice from their website on mixing and matching 8 & 9 speed.

13) What components are compatible between 8-speed and Mega-9?
First, Shimano® only guarantees index performance with an entire 9-speed drivetrain that includes shift levers, front derailleur, crankset, 9-speed chain, cassette, and rear derailleur. The hubs are the same dimensions. Although several 8- and 9-speed combinations are rideable the performance and durability will not be up to Shimano standards. The following rideable combinations have potential drivetrain problems.
 When using an 8-speed rear derailleur it may not clear the 34-tooth cog on some frames.

 The 9-speed chain is ~0.5 mm narrower and so is the front derailleur cage.
 Using a 9-speed chain with 8-speed front derailleur and crankset will result in sluggish shifting and the adjustment is more critical. You may have to continue to hold the shift lever in an "overshift" until the shift is complete. In the worst case, some 8-speed chain rings have shown a tendency for "chain jamming" during downshifts with a 9 speed chain.
 The 8-speed chain is too wide for 9 speed front derailleur; the chain will rub during cross shifting (large/mid ring/large cog).
 9-speed chain should be no problem for an 8-speed rear drivetrain.

 The 9-speed chainring release teeth and pick-up teeth are reprofiled for narrower chains, therefore you can not use an 8-speed chain, and the pick-up teeth will make noise against the chain during minor cross chaining.

Furthermore, success with one bike may not guarantee the same result with another bike due to the different dimensions between frames and production tolerances of components. It might be OK, but Shimano® can't guarantee it. Finally, although you may be partially upgrading to 9-speed you may downgrade the shifting performance.

[Gordo]

My bike has an almost complete Deore 9 speed group cranks, front and rear D's and rear hub. But I have older LX 8 speed shifters and a 8 speed cassette. I also use a 2 ring plus bashring set up. I have a 8 speed chain.

My bike shifts well but the chain rubs on the Front D cage when the chain is in the smallest cog. I think this is due to the narrower cage on the 9 speed.  

[Phillip]

That or the width of the 8 speed chain. Maybe that's why Shimano reccomends a 9 speed chain with your setup.