Alivio 8 vs LX 9 speed
I have a Specialized Sirrus that has a Deore LX Derailleur which is a 9 speed. I also have a Trek 4500 with Alivio Derailleur which is an 8 speed. I was thinking about upgrading the LX on the Sirrus with XT and putting the LX on the Trek.
The LBS I bought the Sirrus from said that is doable, however the LBS I bought the Trek from said it isn't. So my question is which one is correct and which one isn't? Also is it worth my money to upgrade if they are working ok?
I am not having any problems with the Sirrus and really the only thing with the Trek is chain slap and that is only when we are going down hill on a very bumpy trail and fairly fast.
As usual Thanks for all of your advice...
I would think it would work, but You'ed have to be careful about not shifting too far over and setting up the derrailleur right. It would mainly mean being very careful to make sure the derrailleur is adjucted, or it seems like you could shift into your spokes pretty easy. I think.
It's the shifters that determine the increments. If you have 8-speed indexed shifters, you must use an 8-speed cassette. Deraileurs themselves aren't indexed; they move according to how much cable the shifter pulls. Therefore you can use a 9-speed derailleur with an 8-speed cassette, but it will still of course be 8-speed.
You can pick up LX and XT RD's for good prices on sale, but unless there's a particular malfunction in your Alivio RD that you're trying to correct, I frankly doubt you'll notice much difference. But if it's worth $40 or whatever to you, you can certainly go ahead and do it.
To do a 9-speed upgrade, you will need new shifters, rear derailleur, cassette, and probably a chain.
Your Trek is upgradable to 9 speed. It will require a tad more than just putting the lx derailleur on the rear. Your existing Alivio rear derailleur is limited to the maximum cog size it can handle. I believe the limit is 30 teeth on the largest cog.
If your front derailleur on the Trek is an Alivio you will be limited to a maximum chainring size of 42 teeth if memory serves me correctly. So if you upgrade your largest chainring to a 44 tooth like on most 9 speed systems(XTR excluded) you will need a new front derailleur. I will defer to others on the 9 speed chain compatibility of the chainrings.
Of course, you will need a 9 speed cassette on the Trek. The overall width of a 9 speed and 8 speed mountain bike cassette are the same. The cog spacing is reduced with the 9 speed.
You need a 9 speed shifter for the rear. It would be possible to find one and not a pair of shifters if you don't care about looks/the shifters matching.
Your chainstay width at the dropouts should be 135mm. Since it is already an 8 speed this is a given. I believe the transition to 135mm in mountain bikes happened back around 1990.
Thanks for all the advice. Really all I was going to do is put an XT rd on my Sirrus and put the LX rd that was on it on my Trek. I wasn't planning on turning my Trek into a 9. I don't do real technical off road stuff so the 8 speed is fine.
I am really not having any problem with either one of them other than some chain slap on the trek.
Do you think the LX would help with the chain slap? I have heard the LX spring is quite a bit stronger than the Alivio.
I think you're not very likely to notice much of a difference on either bike, frankly, unless one of the current derailleurs is malfunctioning or worn out.
A stiffer spring might help a little with the chain slap, but so will shortening the chain by a link or two.
But like I said, there's no real reason not to do it, either. It seems like a fair amount of work and expense to get rid of a little chain slap, though.
As usual you are right. I rode a little off road tonight and most of the chain slap is going down a bumpy trail if I leave it in the little cog.
Both bikes shift very smoothly with the exception if I am climbing which I guess none of them do at that point unless they are the high end, but they don't do bad even then.
So I will ride them until I have a problem then worry about it.
A better upgrade would probably be the front fork on the Trek. It has a Rock Shox Judy TT so I may upgrade to a higher grade fork. But then again I may just leave it alone.