BostonRoadee

Okay, I’ve done my homework (Lennard Zinn & Sheldon Brown) and searched the forum, and I still have a question. If it’s in the wrong place or I’ve missed a relevant post, feel free to point me there, please.

I need to know if I need to replace my cassette, but it’s a bit more complicated than that.

I’m recently back into biking after many, many years away. I bought a Giant OCR 3 (no giggles, please), with an 8-spd, 11-25 cassette. I thought I took decent care of my chain this winter (according to the instructions from my highly respected local LBS), but after 1200 miles, much of it rainy and post-snow roads (plus way more hours on my rollers, too) I recently noticed some skipping and a slight grinding or crunching feeling/sound when I pedal. Waited a couple weeks (b/c didn’t know what it was), then last night, looked it up in Zinn, and then measured the chain three times: Almost 1/16” too long (just a tiny hair under). Thus, tretched, should be replaced, according to Zinn and Brown.

I looked at the cogs – they don’t look too bad to me. No dramatic hooking/shark finning, very little deep scratching, etc. But I am no expert. So, LBS this morning confirmed the chain should be replaced – AND the mechanic told me “You have to replace the cassette, too.” It just seemed like a knee-jerk thing, maybe what they tell everyone. I don’t think he looked at the cassette first. I asked a few q’s – “Do you mean chain is stretched too far and so it’s a sure thing cassette should also be replaced?” Answer, yes.

Zinn says you should replace cassette if chain is 1/8” too long – not 1/16”. It’s possible I mis-measured last night. I’m definitely not an expert, just getting back into the sport. LBS has a good rep, but their svce. Dep’t has been known to be shoddy at times. So, my radar is up: Am I getting an “up-sell?” What do you think?

datlas 

I am not a mechanic....but...


First, did you clean/oil the chain to see if that helps?? If you still have the problem, why not put on a new chain and see how it works before you sign up for a new cassette? That's what I would do.

But see what the BF experts say.

BostonRoadee

Good point, and I thought of that too. However, the LBS is scheduled to do the whole job on Fri., and I'd like to get it all done at once. First, they're much better at it than me, second, being finals period for grad school, I don't have the time/patience to learn it all myself right now...

garysol1 

If it were me at that low of a mileage I would be doing chain only. BUT.....You mentioned skipping. If what you heard and felt truly was SKIPPING then a cassette may not be a bad idea.

anti.team

I think it depends on the condition the bike was in when you bought it. I'm assuming that it was used, since an 8sp cassette puts it at about 8+ years old (edit: oops, forgot about 8sp Sora!) How many miles were on the cassette/chain when you bought it?

If both cassette and chain were new when you started, just replace the chain. The consensus I have seen around here is that a cassette should last about 2-3 times as long as the chain.

datlas 

If you are like most grad students, money is an issue. I would just cancel friday's appointment...clean/lube the chain....if still skipping put on a new chain yourself (it's easy even a klutz like me can do it)....and re-evaluate.

If on the other hand you have the spare change, go ahead and give the LBS your money on friday.

xerotope

Um, my '04 Trek 1000 has an 8 speed cassette. As does the 2008 OCR3 (according to their site). 8 speed cassettes are still pretty common with entry level drive trains like Shimano Sora.

+1 to taking your cassette off and giving it a good cleaning though.

sharkey00

I would say if your chain is skipping during riding you should replace both. Those teeth are probably more worn than you think. If you replaced it before skipping you should be able to replace just the chain. That said I would bet that if you just replaced the chain you would have no problems but would run into problems sooner (say 600 mi this time).

Also, if you are trying to save money learn how to replace a cassette yourself. In my opinion it is one of the cheapest and easiest repairs. Just but the tool for 6 bucks (your LBS is probably charging you at least 15 or gasp for a "tune up"). It is a simple thing to do just for lack of a better term, unscrew the old one, slap on the new one and done. The best part is no adjustments to fiddle with.

StanSeven

Assuming the previous owner put miles on the bike and you didn't start with a new chain and cassette, they probably both need replacing. A chain with 1/16" wear doesn't usually cause skipping so they both likely are worn.

One caution about Zinn's advice is several chains, regardless of wear, cause cassettes to go.

If you aren't convinced about needing a new cassette, just replace the chain and try riding. If the cassette is bad, you'll find out in a few minutes. The drivetrain won't be smooth and you'll start getting skips almost right away.

Podolak

I put my 8-speed cassette on my Marin Novato through heck this Winter, it is still smooth. I would think a good chain cleaning and cassette cleaning like everyone else has suggested would be your best bet. If you don't have the time to do it, maybe your LBS can just do that for you.

BostonRoadee

Thanks, everyone so far. BTW, not to cast questions on anyone, but could those of you who are mechanics or work in LBS's ID yourselves? It would help me weight the answers.

NOTES:

1) The bike is an '07 OCR3, bought new from an LBS (on clearance in September).

2) I agree with them on replacing the chain -- no questions there.

3) I'm not POSITIVE about the skipping, it's somewhat subtle and I don't have a lot of experience yet with bike maintenance (not for the last 26 yrs, anyway). It makes a slight grinding sound (which I can also feel through the cranks/pedals), and every once in a while (esp., but not only, after changing gears) I do feel the pedals jerk forward for a moment.

4) Finally:
True, but if I don't get skips right away, as others have pointed out, but the cassette is still a bit worn, it might still wear out the chain sooner than it should. LBS guy told me that the original chain was fairly cheap -- which I believe -- which might have led to extra wear on cassette...?

5) I might be willing to try installing chain and cassette if it's as easy as you guys say. I'm considering a chain with a master link (is that what it's called?) which'll allow me to pop chain off w/o tool, even.

Camilo

Sora 8 speed are fairly recent. My daughter's ~ 2 yo Giant OCR has Sora 8 speed. They may be selling old stock 8 speeds as new still, although I think most recent version is 9.

To OP: I would try the chain with the old cassette. I would also ask the bike shop to show me EXACTLY why they think the cassette is worn, definitely ask another person than the one who is recommending it.

Camilo

Yes all this stuff is easy but requires special tools.

Chain - even with a master link, I believe you'll have to cut it to size with a chain tool (punches out rivets). They are cheap, about $5. Since you have an existing chain, you won't have to go through the process of figuring length, you'll just compare.

Cassette: another dead-easy task, but you'll need a chain whip ($10-$20 mail order, local price uncertain), a cassette locknut tool ($5) and a long handled wrench of the appropriate size, either adjustable or open end. To be proper, you'll also need a torque wrench, but many/most say just tighten it very tight.

JPMacG

I recommend that you replace the chain yourself. Invest in a chain tool (about $10) buy an 8-speed chain ($15 to 25$) and replace it yourself. It takes about 10 minutes. Then, if the new chain skips on the cassette, replace the cassette. Chain removal and replacement is a good skill to have and is really very easy. Cassette replacement is a little more difficult but still something everyone can do themselves.

FWIW, I have a 2006 Giant FCR3, which probably has nearly the same cassette and chain. My first chain lasted 2200 miles, after which it had stretched 1/16 inch. I replaced the chain, but the new chain skipped on the old cassette, so I replaced the cassette too. The new cassette was around $20.

mustang1

Change the chain and cassette.

If the chain is worn, the cassette will also be worn. If you're tight on cash, do what the others say and change the chain and then if you require it, the cassette as well. But really, just nullify and potential grief in one go.

I'm not a mechanic.

I have 2006 Tiagra-kitted Allez. It's an 8 speed.

neilG

I USED to work in bike shops. If a customer tells me a chain skips, I do the following:

I ride the bike.
Determine whether or not there is a tight or bent link, or is seriously dirty. Repair as needed.
Replace chain if needed, test ride again.
Replace cassette if needed. Test ride again

The labor cost of cleaning a chain could easily be the same as a new chain. The mechanic would much rather replace the chain than muck around in the solvent tank. However, this presents the problem of putting a new chain on a worn cassette. In my case, I would first do a quick spray with some lube to partially clean the chain.

_dhan_

new in september? I can't imagine a cassette going out that quickly. Then again, I haven't been riding in super crappy weather either. Are you sure that the chain was skipping? My first inclination would be to check the shifting to make sure that the chain wasn't trying to jump cogs. That could also give the lurching forward feeling. Just tossing that out there.

I'm no mechanic, but I did build up my bike myself.

twilkins9076

I can see wearing out a chain in 1200 miles of crappy riding, but the cassette should be good for more than that. I echo the prior advice of replacing the chain and cleaning the cassette. If you've still got a problem, then consider replacing it.

I've also head mechanics tell me they recommend replacing the cassette every time you replace the chain, but in my experience unless you've allowed your chain to be badly worn, you probably don't need to.

It's interesting...I tend to take real good care of my chains, and the one on my single bike is just now showing measurable stretch at about 4700 miles. Because it has never been replaced since the bike was purchased, I've wondered if I will need to replace the cassette at the same time, but was planning to just do the chain first and see what happens.

Retro Grouch 

At 12 1/16" I'm going to recommend replacing the chain but not the cassette AND adjusting the rear derailleur.

I pretty much don't care how old the bike is. 1/16" of stretch is 1/16". That's the early edge of the replacement point.

So how about the skip? Have you had your derailleur adjustment checked? My bet is that 1/2 turn on the barrel adjuster will cure the skip.

Oh - and even if adjusting the derailleur fixes the skip, don't be tempted to skip the chain replacement. It still has 1/16" wear. If you let it go it will be necessary to replace the cassette and cassettes are more expensive than chains.

Gonzo Bob

I probably replace the chain 5 or 6 times before I replace the cassette, so I'm with RG. Replace the chain but not the cassette. But it also sounds like the cassette needs a good cleaning. A dirty cassette and a dirty chain or a chain with a stiff link could be the cause of your skipping and not wear. Replacing with a new chain only takes care of part of that. If you clean the cassette and replace the chain and still get skipping (and it's not a mal-adjusted derailer), then replace the cassette.

fthomas

I work for a large LBS part time. With that said it does not qualify me as an expert (drip under pressure). Please be more specific by what you mean by skip". If the chain is "jumping" on the sprocket (the teeth on the sprocket combined with the worn chain will not hold under pressure) and not "skipping" from one gear to the other then you may get what you are describing. It also sounds as if things need to be adjusted, which would not be surprising given cable stretch, chain wear, and all other wear combined.

Chains are not all that expensive

A cassette can be expensive, but you can also get a Forte from Performance really cheap. They actually are pretty good given the price.

Your cassette and chain rings should last quite a while and from your description I don't think it would warrant a new cassette.

Take it apart and make sure that your hub is in good condition and adjusted properly in addition to cleaning the cassette. Could it be the Pawl that is going out in the freehub? In which case you need a new freehub and/or rear hub and not just a cassette. None of it is rocket science.



On many of the less expensive bikes (a lot) you can actually see the cassette wobble as if it is floating on the rear hub while the bike is on the repair stand. Cheap hubs and cassette's combine lax tolerances resulting in this wobble! MOST people will never notice it when riding or shifting gears. A lot of people do not put that many miles on their bikes or use the bike in really adverse conditions.

Link on How to Repair a Rear Hub

Bill Kapaun

I can get the KMC-51? chains at my local dept. store for $6-7. I just replace once per year as a matter of course. When I get several in the used pile, maybe I'll measure them?

BTW, isn't your cassette a 12-26?

IF you do need a new cassette, now would be a good time to try a different combo if your gearing doesn't quite suit you. Maybe a 13-26 if you never use your 12?

BostonRoadee

You guys have been awesome. The total lack of dumb, sardonic responses makes this a refreshing change from the Road Bike sub-forum. Thank you all for your useful insights.

The majority ruling here (not without dissent, I note) seems to be: Replace the chain, clean the cassette (haven't done so in too long, I admit), ride the bike a while, and see what happens. If there's still a problem, look into replacing the cassette. There are also other issues on the bike to check out (below).

I was definitely planning on replacing the chain anyway, so it works for me.

FThomas' point about cassette wobble is well-taken. I remember seeing some of that while bike was on the stand, but being new to the game, I didn't connect it with what I'm calling "skipping."

It's hard to be more specific about skipping, b/c I can't get the bike to do it on the repair stand, so I can inspect it more closely. It only does it sporadically while I'm riding.

I will try to get one of the more senior LBS mechanics (I trust them more, and not just because of their age) to look at it on Friday. I'll describe the "skipping," point out the cassette wobble, have them check the rear derailleur (yes, I can do it myself, but why not have them take a peek?), replace the chain, and there's a few other small, non-related fixes I'm having them do.

I think that sums up the most coherent way of weaving everyone's advice together. Thank you again.

I've been waiting -- too long, it seems -- to tend to my bike until I get through with my insane finals period here in grad school. Finals are almost over, it's getting warm outside, and I look forward to having a smoother drive train to ride the daylights out of.

garysol1 

I would bet a dollar that the skipping is a slightly miss adjusted rear deraileur causing the chain to try and jump up a gear every now and then.

ThreLittleBirds

I would bet $5