Bicycle Mechanics - What is better about a better derailleur?

Whats the difference between a $40 derailleur and a $120 derailleur? Honest question, I'd really like to know :)

$80 and weight :D

Better derailleurs generally have better bushings in their pulleys. The cheapest are just plastic spinning on steel. The better ones have either ceramic bushings or cartridge bearings, which are both smoother and last longer.

As mentioned, weight is also generally a factor.

On the road bike, where derailleurs last a long time, the nicer ones may be worth it, but I’ve ruined way too many riding mountain bikes to ever think about spending the $$ on an XTR.

In a word, "crispness".

$80 and weight :DBling and poseur' points too.

The better components are easer to install, and adjust.

They stay in adjustment longer and function better.

If you want better shifting, get better levers. If you want to go faster, get better wheels. Either one will cost more than the derailleur. If you've got crappy levers, it's unlikely you'll notice any benefit from the new derailleur!

If the overall bike is of a good enough quality to upgrade, upgrading the derailleur is pretty far down the list, IMO. If not, you get a lot more bang for the buck buying a better bike!

The bike is pretty good, its an old cannondale super v. I really like it. I'm giving it a total overhual over the next several months, in a few steps. First step is the drivetrain. Its rather worn, and the rear derailleur is tweaked slightly, but I want upgrade to 9 speed anyways :p So I'm trying to decide what derailleur (and shifter) to get.

I don't mind spending some good cash to get quality, but not so much that I'm spending $50 more for something only slightly better. I'm trying to figure out where that point of deminishing returns is at.

Oops. That's a mtn bike, isn't it? I'm out of my area of expertise. In any case, if you're upgrading to a different number of rear cogs, you may have to upgrade shifters... not sure about mtn bike components.

Yeah its an mtb. I forgot this isn't an mtb specific forum so I didn't mention that. oops :p

The four "more modern" mountain bikes we've owned came with the cheaper front deraileur (just below below LX). They did fine until they wore some. Then they would take much longer to shift and would not stay adjusted. We've used LX, XT and XTR with about 7 bikes (4 ATB and 3 road) over the years. I'd say XT is a little faster shifting than LX. XTR is about the same as XT, but it's a lot more ruggedly built. For my money, LX is the best value. XTR has gotten too expensive; they don't discount it like they used too anymore. Probably due to the decline in the value of the dollar.

For the rear, our only experience is with LX and XT. I have never noticed a difference for the rear.

Al

You can tell a pretty huge difference between say Alivio and XT, but go from XT to XTR and there isn't much of a perceptible difference. Same for like Tiagra vs. Ultegra vs. Dura Ace. I do like using XTR rears on my mountain bikes becuase they do last forever, and are rediculously smooth. On my road bike I have an old Ultegra 600 (probably 10-12 years old) and its smooth like butter. For the fronts anything goes... they all basically work the same and shift the same. If you have LX/105 or better shifters you will notice a difference in response and the smoothness as well.

Spring quality and tension are the biggest. Those translate into the "crisper" shifting as well as chain slap/suck control (different springs for both).

The pulleys make a little bit of difference.

For your own perception (maybe your buddies too), there might be some cool factor.

I really question weight. The weight of dirt in your tires will be more than what you save, but to some, every gram counts.

On the road, I ended up with the top end Dura Ace through a good deal. Love it.
On the trails, I go middle of the road since I tend to fall/hit things that lower the life span. XTR is nicer than XT for sure, but at the replacement price point, I've been very happy with XT.

The better components are easer to install, and adjust.

Really??...........

As far as I know, with XTR you still have to screw it onto the hanger, set the limits and fuss with cable tension. Same as Alivio :D

As far as I know, with XTR you still have to screw it onto the hanger, set the limits and fuss with cable tension. Same as Alivio :D....and attach the cable.

"better" dérailleurs are made better with more expensive an lighter materials. However, there is a point of diminishing return, when you go to more expensive dérailleurs. As you go higher in teh groupo hierarchy you pay more and more for a smaller and smaller return for your money..

Typically the mid point in the groupo hierarchy is the best value. Ex: Ultegra or Centaur...

I've used older altus, alivio, acera x, lx, and xt rear derailleurs. As well as lots of really crappy ones. I've never done a test of trying out each one with the same shifters, but I certainly noticed a differenc on the way up the hierarchy. On the road it's neglible, but obviously on the trail the difference is more profound. I don't know if they still make it, but the acera x was just fine, the lx works no problems (8 years old and been crashed), as long as I keep it tuned right, and the xt was a bit better. But for me the lx is just right because it's what's sitting on my bike right now. No need to upgrade. For my front derailleur I had an stx-rc and it was pretty good, a little finicky with tuning, but that seized up steel/aluminium stylee. So now I've got an old alivio on there and I really don't notice a difference. I'm running 8 speed xt shifters. The biggest upgrade to your shifting is knowing how to tune them right, and making sure all your parts are compatible. Right now I'm running too big of a third chainring, so I'm having to fudge the setup, forcing me to shift the front more often to avoid rubbing. I'm either going to change my front shifter to an old exage friction thumbshifter, or take of the big ring and put a bashguard on and be done with it. More offroading or more touring with the trailer... tough choice ;)

You can really tell the difference in a racing situation. I was once in a mtn bike race with an STX-RC group and an LX rear derailler (and Gripshift) and the shifting was very sloppy! It shifted fine just riding around.

I find the biggest difference in performance is between my bike (lx rear, stx-rc front, xt shifters) being freshly tuned or not quite right. When it's tuned right I have no problems. Of course someone else could hop on my bike and have troubles because they wouldn't know the what little tricks to use in each shifting situation. You know what I mean. When your setup isn't running quite right and you hold that shifter in a bit to force the chain over, then ease it up. Or when it's really bad and shift up twice and down once. hehehe When my setup is freshly tuned there's is a slight bit of that, but since the bike has seen 8 years of heavy use, I guess I'm not too worried about it. It's all part of the experience. More organic :)