New Chain and Rear Cog

Triathlon Forum
1

I was told yesterday when I went in for a simple tune and cleaning of my bike that I need a new chain. And when I replace the chain, I have to replace the rear cog in tandem. I have two questions with this, I wasn’t expecting my cog and chain to “need replacement” so quick. I’ve only had the bike for a little shy of 2 years. I know it depends on mileage, but I don’t consider myself a massive mileage biker. 1) How many miles or time is it until you change the chain and cog? 2) And do these need to be replaced together?

I’ve had my previous road bike for over 5 years and never replaced my chain or cog and haven’t noticed any problems. I figured that with a Dure-Ace setup, for the price, it would’ve lasted at least 2 years.

I ask, because I really felt like the shop was trying to sell me everything in the store.

2

…if you do need to replace the chain / cog…you can go with Ultegra to save some $$$.

I’ve done this for several years with no problems.

3

A chain typcially lasts 1500 to 3000 miles, depending on care, lube, dirt, etc. It’s certainly reasonable to expect to have to switch chains in a 2 year period. You can find a 105 chain online for under $30.

Shops don’t have a definite way to test for cassette wear, and as a rule, will recommend changing a cassette with the chain. Usually, this isn’t necessary. If your cassette is worn out (either from lots of use, or if you didn’t change your chain in time), you will need to replace it. As a very rough rule of thumb, I keep my cassettes as long as I keep 3 chains. Have a look at the teeth on the cassette, and see if they look worn relative to a new one. If you don’t have access to a new one, compare the cogs you most often use to the ones you least often use (likely the small ring), and see if the shape is different.

Dura-ace doesn’t necessarily last longer. It’s smoother and lighter. 105/ultrega are likely both equally durable, if not moreso.

4

If you wait a long time between chain cleanings, the chain gets crap in it, stretches, gets worn and wears on the cassette as well. The new chain will skip shifts or skip when riding due to wear n tear from the old chain on the cassette.

You may not need a new cassette or you may. If you haven’t replaced your chain in 2-5 years, you’ll probably need a new cassette. The reason you are not seeing problems is bc the chain and cassette are mated. If you switched cassettes only, you would notice it. if you switched chains only, you would notice it.

fwiw, change your chain every 3-4000 miles and you should only have to change chains. Doing it 1x per year may cause you to have to change cassettes as well.

5

Here’s the thing…I haven’t had any issues at all. I just wanted to get a cleaning and tune-up in preparation for Ironman Louisville. I wanted to get a tune-up now for the homestretch of training and then get a small tune-up the week prior to the Ironman. But as far as shifting issues or skipping, I haven’t had any issues.

I simply felt that the shop tried to sell me everything in the store. I would’ve walked out with a new bike if they had their way.

6

right and you probably won’t have shifting issues with that chain on that cassette. Put that chain on a different cassette or a new chain on that cassette and you get problems.
As long as you ride that chain and that cassette together, you should be ok. Eventually though, when you replace that chain, you will need to replace that cassette b/c that chain wore that cassette out (for lack of a better term)

7

That makes sense. Thanks. So would it hurt or help to change the chain at this point, or should I just wait and do the entire replacement all together? I guess I’d have to look and see what my rear cassette’s teeth look like.

8

Its not about how long in terms of years, its about how many miles.

Lance rides more miles per day than you, but you both should replace chain after same number of miles. If you wait too long, then the stretched chain will cause wear and tear on rear cassette as well as front chain rings. If you replace approximately every 1,500 miles, then you shouldn’t have to replace chain rings or cassettes.

Dura-Ace doesn’t mean more durable; it just means it weighs less. Sometimes lightweight means less durable. I had a mechanic suggest 2-3k miles for Ultegra chains but 1k to 1,500 miles for Dura Ace.

9

Great information from everyone. I appreciate it. I’ll have to review my log and see how many miles I’ve ridden. And estimate how many miles are on my trainer to see what I’ve done over the past 18 months.

10

I would change the chain now, and ride it. If it works OK, keep the cassette, if it skips, swap the cassette.

11

The real answer here is that, of course, as usual, your LBS is trying to rip you off.

Or, you know, trying to save you from hurting yourself. One or the other.

The posts on the thread so far have been kind-of right on. kind of.

How much mileage or time you have on your chain is pretty much irrelevant. The pertinent question is how much it has stretched, and this is easily measurable and a simple question of fact. If your chain is out of spec, it needs to be replaced. How hard you ride, how much you ride, and the conditions you ride in are all variables that effect the condition of your chain, but all that really matters is “has it elongated past the acceptable tolerance level?” I would be pretty surprised if your LBS lead you astray on something as easy to check as this.

If you let your chain elongate past a certain point, you will cause damage to your cassette, and sometimes the chainrings. This damage may not be readily apparent to you, but at a certain level of chain elongation it is almost inevitable. The cog will deform to match the spacing of the rollers on your elongated chain.

You may not notice that this has occurred, and to all outward appearances everything will be fine until one day you stand up on the pedals, you push down hard, your chain skips, and you lose teeth (the, uhm, kind that you have in your mouth. Not the ones on the chainring. But, well, those too, actually…) Or, you know, go over the bars and die or something.

This is also why a good bike shop will recommend replacing the cassette at a certain measured level of chain elongation. It just happens to be good, solid, practical, conservative advice.

Same-ish scenario. You replace the chain, leave the deformed cassette, all is good for a couple of weeks, then you stand up on the pedals, chain skips, you lose teeth. Sure, maybe you can save some $ and get away with just replacing the chain. You may even get lucky and never have a problem; but if you have worked on bikes long enough, you have seen someone try this, have it work fine for a week or so, and then walk back into the shop with a split lip. Or worse. I had a customer wind up in a halo for six months this way - but, hey - they saved fifty bucks on a new cassette.

The Local Bike Shop can’t afford to kill off it’s customers, or worse, get sued by them. That’s why they risk pissing off cheapskates by offering them good advice that sounds like a scam to people who don’t know what they are talking about, generally aren’t interested in hearing an explanation, and refuse to believe that anything they are told is true unless and until it has been vetted by the idiot squad on RBR.

Thankfully, most of the chuckleheads in the tin-foil conspiracy caps simply shop on line now, and only waddle in - resplendent in bandages - when the thing that used to be their bike is largely reduced to a pile of parts. While they fondle their ironic moustaches, we explain to them why that BB lockring isn’t a cog lock ring, or that perhaps if they had actually replaced that chain they wouldn’t have needed to max out their girlfriend’s Visa card paying medical bills…

.

12

Basically keep replacing the chain until the cassette causing skipping when shifting, then get a new cassette. 3:1 ratio seems bout right. I’ve read (FWIW) that Ultegras are longer lasting than D/A due to the different materials (Steel vs Ti?)