Mountain Biking - What do I need to know when buying a rear derailleur?

And is there really a noticeable difference between a 50 dollar derailleur and a $100 one?

I have a shimano deore lx. I look on the net and I see some various models that are long, medium, and short. I'm not sure what I should get. Other than that all I know is that I have 9 gears and that's something to consider...Not sure what else I should worry about though,


Thanks.

This is getting really lame. :D

I looked on the FAQ, didn't find much

This is getting really lame. :D

So are your replies. Don't answer if you don't want to.

To make it simple if you are running a 3-ring crankset, you will need the long cage derailleur and if you are running a 2-ring crankset, you can use the medium cage.

To make it simple if you are running a 3-ring crankset, you will need the long cage derailleur and if you are running a 2-ring crankset, you can use the medium cage.

Eh see it depends on your gearing too. I would be comfortable running a short cage derailleur on a 2 ring setup with a small spread cassette such as a FR/DH rig with a road cassette.

I'm a little confused. I don't know how to tell if my original derailleur is a 'long'. It says LX, does that mean long?

Any more info on how to pick long/med/short? I'm still pretty confused on that. I have 3 chain rings and 9 gears on the cassette.

What's a small spread? What's a large spread? Does that equate to the long/med/short thing, somehow?

If you have an 11-32 or 11-34 cassette, and three chainrings, you need a long cage derailuer. LX does not mean long cage. The length of the derailuer determines how much slack can be taken out of the chain. If you run only a small ring up front and use a close ratio road cassette, such as an 11-23 ultegra, you could get by with a short or medium cage. Does that make any sense?

Yes there are differences in derailleurs. Bearings or bushings, construction material, weight, durability, shifting. The LX is the model, as in Deore, LX, XT, XTR.

I think with your set up you will need a long cage deraileur. You will notice some differences in shifting with a higher priced deraileur, such as smoother, crisper shifting among other things. If you are just using your bike for recreational use I would go no higher than a XT level shimano or sram X7/X9. What type of bike do you have? You can try looking your bike up on the manufactures
website. It should tell you the model of your deraileur. You can then search for it on shimano's website. I have a 3 ring crankset and an 8 speed 11-32 rear casset and my deraileur is a long cage.

I have a 2003 specialized rockhopper comp fsr. I am doing recreational, don't give a crap about weight, but want a medium-performance derailleur. Not something cheap that will fall apart, but something good enough that I can possibly switch it to my future bike, or at least something that is just decent but isn't over $100

I like this one, despite it being a little pricey for me
http://www.rei.com/product/764680
$109 from REI
http://www.rei.com/product/764680
Would this be better than what I have (I'm guessing yes?)


Or maybe I should just go cheaper? (Would this be better than what I have? Or worse?)
http://www.rei.com/product/764679
$54 from REI
http://www.rei.com/product/764679

I'm trying to get an idea of what my current derailleur was worth, new, and the quality of it compared to these types of derailleurs I am posting.

I am looking at REI bc I have a giftcard there, by the way. But maybe I can get these cheaper off other sites..

http://www.blueskycycling.com/product3887_38_-2008-Shimano-Deore-XT-M771-Rear-Derailleur.htm

LOL! Hilarious, thanks

The XT one you have linked to for $109 is a very good derailleur. Its one step down from the top of the line XTR. I would go with this one though.
http://www.rei.com/product/764681?cm_sp=prod*desc_rel_item*element (http://www.rei.com/product/764681?cm_sp=prod*desc_rel_item*element)

Its the shadow form of the XT which means it does not stick out as much as the regular derailleur and its the same price. It also means a less chance of trashing your new derailleur on a rock or other object. The XT line will not disappoint and is better than what you have. The 54 dollar one is no better than what you currently have on your bike that would be a step down. If you are relly serious about improving your shifting, look into buying new shifters in the future. You can buy the nicest deraileur out there and still have crappy shifting if your shifters are cheap.

Yeah, all I'm looking for is maybe a small step up from my original derailleur. I just need to replace my old one because I think it is old. The guy at the LBS wiggled it and said it was nearing the end of its life. I can see that one of the cogs on the derailleur is very worn so it must be at the end of its life? It's not like it is causing any huge problems but it doesn't seem too smooth and occasionally when I hit a bump while pedaling, the gears can skip temporarily (so annoying) but this isn't too often.

Any comments on how I should know when to replace my derailleur? I just got this bike, used, and then used it for a couple years, and I have never compared a new derailleur to an old one, but all I know is my bike sure doesn't shift as well as others with nearly the same quality equiptment..it shift fine and all, but it doesnt feel/sound as smooth as others' bikes. And when you turn the crank backwards it doesn't seem too smooth, almost kinda rough, and I can see the derailleur 'leg' pulsating back and forth about a 1/4" as I crank the pedals backwards.

I have cleaned the derailleur and I have a new chain and drivetrain...so I dunno..maybe I should replace the derrailleur, maybe not...man I'm such a noob!

Good information on derailers here.

http://sheldonbrown.com/harris/derailers-rear.html

Go with an XT if anything.

Are you sure you really need a new derailleur? Might the bike just need a tune up?

If your current one is broken or something, Shimano's lineup goes like this:


Deore
Deore LX (I think in more recent years it's just been called "LX", but I could be wrong.)
XT
XTR

So the XT would be the smallest step up you can make. However, a current year LX is probably also going to be a noticeable step up from a 2003 LX, so just getting a new LX may be fine and it will definitely cost less than an XT.

Deore would be one step down but you might find it good enough for your purposes. When in doubt, use a long cage. It's probably what you have now.

If you do buy a deore, don't buy it from REI. It can be had online for ~20 dollars with shipping. Nashbar or performance, I think.

I have XT on one bike and acera on my other.. honestly there is not much difference in shifting .. If your running a 32 or 34 rear cassette get a long cage.. nashbar deore is a good deal at 20 bucks.. just get that.. The rear derailer importance is overrated in my opinion.

^^
Agreed, plus they are vulnerable. If you want good shifting the money is much better spent on the shifters themselves, or nice new cables, correctly adjusted (cheap and worth it).

Is your LX broken or something?

To make it simple if you are running a 3-ring crankset, you will need the long cage derailleur and if you are running a 2-ring crankset, you can use the medium cage.

I have a 3-ring crankset(Shimano XT) and run a medium cage RD(SRAM X9), I have no shifting problems at all.

And is there really a noticeable difference between a 50 dollar derailleur and a $100 one?



No difference what so ever, I prefer $7 derailleurs no difference between XTR/X.0 at all, its just bragging rights yo.

No difference what so ever, I prefer $7 derailleurs no difference between XTR/X.0 at all, its just bragging rights yo.
I disagree, The old shimano SIS front derailleurs work fine for a while but they are flimsey and weak. There is a difference between low end and high end components. Not everyone notices the differences but to say there is none is wrong.

I disagree, The old shimano SIS front derailleurs work fine for a while but they are flimsey and weak. There is a difference between low end and high end components. Not everyone notices the differences but to say there is none is wrong.

I was totally kidding at what I said. $7 derailleurs are the custom ones made for Walmart Mongoose bikes which totally suck.

You get what you pay for.

Walmart Mongoose bikes which totally suck.
LOL I totally agree!

You get what you pay for.

Which is a slightly lighter and shinier rear derailleur.

People tend to overvalue the importance of the rear mech in shifting performance. There is a reason that the RD is the part usually one step up from the rest of the drivetrain on new bikes- it tends to sell the bike. On a mountain bike, where breaking rear derailleurs is not uncommon, I go with the cheapest model that will perform adequately.

MY LX shifters, yes plural worked OK for a while but soon worked like crap. I've noticed better shifting as I've gone from LX, to XT to XTR all using the same XT trigger shifters.

I see it like this, while more money to replace if you break them, the more you spend on components, in this example rear derailleur often times the smoother and longer lasting it is (and most times lighter too for the weight weenies) When you get up to the XT range and higher, they are just higher quality components, bearings and materials that don't wear out as fast. It's a toss up, do you pay more for in my opinion a better product or do you spend less but maybe have to spend that "less" again because the cheaper product wore out faster.

I personally don't tend to buy anything less than Shimano XT/Sram X.9, and on the new bike I'm looking at it has a mix of 2008 XT and SRAM X.0 which I'm paying more for, just for personal preference.

MY LX shifters, yes plural worked OK for a while but soon worked like crap. I've noticed better shifting as I've gone from LX, to XT to XTR all using the same XT trigger shifters.

Shifters matter a great deal more than derailleurs.

Go with an XT if anything.

This reminds me of the typical roadie conversation, which is why I quit hanging there. A newbie asks what group should I buy. Forumite says:
1. I only ride Dura Ace, everything esle is crap
2. Wouldn't ride anything less than Record, but have Chorus on my beater.
3. Anything less than Ultegra is complete crap and I wouldn't bother riding if I had to go lower.

Sad thing is these are actual answers, or as close as I remember. Truth be known, regular Deore works great. Save your money and get what works. Good luck

Tim

Shifters matter a great deal more than derailleurs.

I meant to say LX Der. not shifters, I use XT Shifters but have XTR on the way,, yeee haaaaaaw.

If you wreck a lot buy some crappy stuff and be done with it and in the end like everything else you get what you pay for.