VegasJen

I have two Treks of roughly the same vintage (circa 2005, or so). One is a "Lexa" (fancied up WSD) and the other is just a plain Jane WSD. The back wheel on the Lexa was replaced a couple of years ago from a donor bike but I don't think the rear cassette matches the original. The front chain ring is just a two speed. The cassette on it now is a 9 -speed, but I think it came with an 8-speed originally (not sure). (This is also the back wheel that broke at the hub a couple months ago. This is relevant as I'm sourcing a replacement wheel for the bike.)

I say this because since I got the bike, I have never been able to get it to consistently shift between all nine gears. It seems I can either get it (fairly) smooth on eight but without either the high or low. Sometimes I can get both high and low, but then it skips one of the middle gears. So I don't know if my problem is spacing between the gears, the number of gears available on the "brifter", the rear deraileur or just that I suck at adjusting the shifter.

However, the WSD, despite being identical virtually every other way except for the paint/graphics, has a 3-speed chain ring and a I believe a 9-speed rear. That one shifts (almost) flawlessly. I just find it interesting that mechanically they're virtually identical except for the number of speeds.

The rest of the shift gear is Shimano Tiagra or Sora. Don't know if that matters.

So my question is, are there standard sets like 3x9 and 2x8? Or is it kind of a mix and match thing, however the manufacturer wants to put them together? Are 3x8 or 2x9 common sets? Do I need to match the front and rear gears for any particular reason? If I have a three speed chain ring, do I *need* to have a certain rear cassette to match?

cxwrench

I don't know what you're really asking, but there have been 2x5, 2x6, 2x7, 2x8, 2x9, 2x10, 2x11, and 2x12. There have also been 3x5, 6, 7, 8, 9, and some 10. Why your bike doesn't shift well? Who knows? Impossible to say in this case. If the shifter is 8 speed and you have a 9 speed wheel there's your problem. Count the cogs, count the clicks in the shifter. A 9 speed cassette needs a shifter with 8 clicks and a compatible derailleur.

SpedFast

Ditto^ Count the clicks when all else fails.

Koyote

Could be parts incompatibility, as the OP wonders, but only a real bonehead would match, say, a 9sp cassette to an 8sp shifter.

Could be a worn cassette, or worn chain, or bent derailleur hanger, or worn cables and/or housing...etc.

This post is a good argument for buyer fewer but better bikes. If you just buy one decent new bike, at least you get a warranty, shop support, and you'll know that some doofus didn't already wear it out or screw it up.

caloso

Indexed shifters work by moving the chain via the derailleur by pulling in or letting out a certain amount cable for each click. The number of cogs on the rear cassette needs to match the number of clicks (or speeds) of your right shifter. If you have an 8 speed shifter and a 9 speed cassette, the clicks won’t line up properly and the chain will skip on some cogs.

So it’s not about matching the cassette and chainrings but matching the cassette and shifter.

Camilo

What is the model of your right (rear) shifter? And, what is the model number? (usually found imprinted on the shifter body somewhere under the rubber hoods) That will tell you how many speeds it shifts, and therefore whether a speeds incompatibility is involved.

VegasJen

OK, just so I understand, am I supposed to have the same number of clicks as gears? Or minus one?

The point of this exercise is I need to replace that rear wheel. I'm not sure if the bike was originally 8 or 9 speed on the cassette. I need to figure that out so I make sure to get the right cassette for the replacement wheel.I'll take a look in the morning.

SoSmellyAir

The wheel only needs to match the frame. On a road bike wheel, a 10-speed freehub will accept a 10 speed, a 9 speed, or an 8 speed cassette, while an 11-speed freehub will also accept a 10 speed, a 9 speed, or an 8 speed cassette with a 1.85 mm spacer. So pretty much any contemporary wheel you can get will work with the cassette you need. As everyone else above pointed out, the more pertinent issue is that you need to match the shifter, the derailleur, and the cassette; all three components must have the same number of speeds, and the shifter and the derailleur must have the same pull ratio. The number of clicks on the shifter should be one less than the number of speeds.

Then the cassette determines what chain you need, which in turn determines which chain ring(s) you can use.

Dean V

As has been said, count the shifter clicks.
Put it at one end of the range and count clicks to the other end.
Number of clicks will be one less than the amount of gears as it is already on a sprocket to start with.

Bah Humbug

If it works currently and you're looking at a replacement, can't you count the number of gears on the current rear?

VegasJen

OK, thanks. Next question. If it turns out the shifter is for a 9-speed, is it possible to mount an 8-speed wheel/cassette and adjust it to shift right in all the gears? Or is there a certain distance the deraileur moves per gear change?

_ForceD_

The bike is/has been converted from 8 to 9…obviously the shifter needs to be changed. But what about the derailleur? Are all 8-9 derailleur’s interchangeable…and/or compatible with the new shifter?

Dan

SoSmellyAir

The "certain distance the derail[l]eur moves per gear change" is the pull ratio, which has to match between the shifter and the derailleur. So the answers to your questions depend on the exact models of both components. The two articles linked below say yes if (a) both components are from the same brand, and (b) that brand is either Shimano or SRAM.

Compatibility [04] Rear derailleurs | BikeGremlin

Can I Use a 9-speed Derailleur With an 8-speed Cassette? – Brainy Biker

However, you stated in your original post that the bike has a 9 speed cassette on it!?

Bald Paul

Not really. The shifters will pull the cable X amount with each click, which, in turn, will cause the RD to move Ymm side to side to change gears. If you have an eight speed cassette, that will be mechanically set up to move the correct amount between the gears (pull ratio.) If you change to a 9 speed (or vice-versa) the spacing differs, but you can't change the pull ratio setup.

SoSmellyAir

I disagree. It is possible for a later 9 speed shifter to have the same pull ratio as an earlier 8 speed shifter, such that the later 9 speed shifter can also correctly shift an 8 speed derailleur corresponding to the earlier 8 speed shifter.

VegasJen

Thanks guys. Those were the answers I needed. Basically, I need to confirm how many clicks I have on the shifter and then match the rear cassette to that number of speeds plus one. I was just trying to see if I had a little more selection to choose from.

Iride01 

If you are going to buy components to make this do what ever it is you want it to do, and some of those components are the more expensive pieces such as STI's. Then you might consider just completely changing everything out to something like Tiagra 10 speed.

cxwrench

You guys are talking about 2 different scenarios.

datlas 

It's actually even more complicated than that due to possible compatibility/incompatibility. between shifter/derailleur/cassettes. Usually if they are all "X" speed they should play nice together but it gets complicated in a hurry.

VegasJen

Not at all my intention. In fact, just the opposite. I want to make sure I only buy the part(s) that will work with what I have now. I have no intention of "reinventing the wheel" so to speak. If what I have works with an 8-speed cassette, then that's what I'm going to shop. No sense finding a 9-speed cassette/wheel, and then having to change the derailleur and shifter to fit.
Oh great!

Dave Mayer

Good. This thread should have ended here. A cassette will cost you less than $50. A set of STI (Shimano Total Integration) shifters will cost you minimum $200. Do the most cost-effective thing.
To reiterate:

1. Figure out the specs on the shifter. That is, the number of speeds. Get the parts number directly off the component, and confirm what you have.
2. Match the cassette to the shifter. The cog spacing between 8,9,10 speed cassettes is all different and they are not in any way compatible.
3. Match the chain to the number of 'speeds'. If you have a 8-speed system, then you need a 7/8 speed chain. The 9-speed chain that the bike shop will carelessly shove you out the door with will shift poorly on a 8-speed system, and all things being equal, will cost you 50% more than the correct 8-speed chain. 10-speed chain: add another 50%, and even worse performance.
4. Make sure the rear derailleur specs matches the shifters! All derailleurs are not the same in terms of how they travel across the cassette, even within the same brands. And of course Campagnolo and SRAM derailleurs are in no way compatible with Shimano shifters.

PS: anyone compelled to respond to this, please please do not make any useless complex pedantic recommendations that includes any of the following terms: 'Shift Mate', 'friction', or 'just try it'.

Iride01 

Then it's pretty important to know exactly what you already have down to the part and version number. With few exceptions, Shimano stamps or prints them on every component. Usually the backside or under the covers on the STI's.

You'll need to know the rear DR specs in particular. That number is usually on the backside of the parallelogram. You might have to remove the wheel and/or clean the gunk off of it to see it.

Once you know that info, more people that frequent the Bicycle Mechanics section of the forums will know what to do with that info to advise you what works with what.

cxwrench

^This^ Shimano 8, 9, and 10 speed have the same cable pull as 7, 8, and 9 speed mtb bike derailleurs as well. You can't use a 10 speed Shimano road shifter with a 10 speed Dyna-Sys mtb derailleur. Won't work.

RCMoeur 

I've lost count of the number of bikes we've had donated to Recycle Your Bicycle or brought in to Rusty Spoke where the number of cogs on the freewheel or cassette doesn't quite match up with the maximum number on the right-hand shifter. At RYB, if the bike is in good shape, it'll get matched up with a donor shifter/freewheel/cassette/wheel to get everything correct again, or if not, the bike becomes a donor to fix others.

Dean V

It won't work. Either put a 9 speed cassette on the wheel or see if "Jtek" do a shift mate to alter the cable pull from 9 to 8 speed spacing.