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Replace the cassette and front sprocket?

13K views 90 replies 38 participants last post by  Curveball  
#1 ·
Bike is six months old, took it to the bike shop because the shifting has been a little off (it’s a 12 speed Sram).

First thing the mechanic does is he puts a gauge on the chain and says, “chain is pretty worn”. I say, ok, put a new chain on it. He says, no I won’t be able to adjust it. Need a new cassette and front cog/sprocket. He’s done this to friends of mine as well. I didn’t see him give any sort of visual inspection to the cassette or front cog. Just a gauge...boom...need a new drivetrain.

Bike has maybe 700 miles on it now. Is it worth buying a new chain and trying to adjust it myself? Or am I wasting my time? Is it really necessary to replace almost my entire drivetrain every six months? Or have to replace chains that are supposedly capable of lasting 2,000 miles, every 2-3 months?
 
#2 ·
Try just a new chain first. If it still shifts poorly then you could replace the rest.

With how scarce cassettes and 12 speed chains are lately I’m riding my current drivetrain into the ground. It’s not shifting the best right now because the chain is overly worn but I accept the suboptimal performance just to eke out as much life as possible.
 
#7 ·
Find another mechanic, or better yet, start learning to maintain your bike.

You might have needed a new chain, but drive train replacement ?
Your shifting issue might not be the chain.
I really should start wrenching on my bike. I have mechanical skills, it’s just I don’t have bike tools…and I’ve always considered adjustments to bike drive trains kind of like performing art. It takes experience. But I’m seriously thinking of doing it. Wonder how much a set of tools would cost?
 
#4 ·
I do not know that worn chain would be the source of shifting issues so I'd 1st recheck the derailleur and the cable adjustment. Worn out chain usually results in it skipping under the load (some gears would be worse than other). If the chain is indeed worn, it'll be costly. I've found that even barely .75 wear required new cassette to match replacement chain so might as well run it till past 1.0. I usually keep front sprocket though but that one will also be done after 2, 3. My new chain/cassette set got me puzzled on trails last weekend with the crank just spinning under any load and me blaming cheap Chinese cassette (that's proved to be a decent purchase after all). This was a 1st in my experience (though ocassional upgrades tend to obscure real durability of my cranksets). At least I had granny gear up front to fall back to and do 40 miles on (I do not fancy 1x setup - too expensive, not flexible enough and the rear dinner plate looks stupid imho).
 
#5 ·
I don't think anyone can say that a cassette needs replacing unless they have tested it with a new chain. I've repaced drivetrain parts on hundreds of cuatomers' bikes, and the only reliable test of rongs and cassettes (besides obvious visual damage) is to put a fresh chain on and test ride it. If anything skips, time to replace those, too.

Your mechanic is probably wrong, but without seeing the bike in-person myself, I can't assume that the mechanic doesn't see something that I can't.
 
#6 ·
Thanks for the feedback. That’s my plan (try a chain first).

I’m starting to become a little apprehensive of this bike shop. First, I purchased the bike there and they give you one free “tightening/adjustment”. When I got there I figured they’d just adjust the derailleur. Instead the guy immediately said, this won’t qualify for the 30 day checkup. First, I didn’t realize it was 30 days…no one ever said 30 days. Second, he immediately started bouncing the bike, moving pivots and looking for stuff. Then he throws his gauge on the chain and says, very worn, needs a new cassette, sprocket, chain and tuneup. And we’re a month out.

And this isn’t the first time something like this^^ has happened to others I personally know that go there.

I’ve purchased 4 bikes there (two in the last year). I have not received my “free adjustment” once. Lol. And I’ve also probably spent over $3,000 in repairs, tuneups, whatever, there. I don’t think I’m going to go back regardless now. I’ll try a chain first - and god help me - if that chain and a few quick adjustments to my derailleur take care of this? I’m going to be really pissed.
 
#20 ·
No doubt in my mind that this is within reason. OP hasn't told us which level of 12spd SRAM bits is on the bike. I've specifically used lower end SRAM chains and 700mi is solidly in the middle of their lifespan. I've gotten as little as about 550mi on low end SRAM chains. We don't know OP's riding conditions, preferred chain lube brand, or cleaning/lubrication regimen (all things that can either extend or reduce service life of drivetrain parts).

I do agree with others who say that because we don't know how the chain actually measured, we don't know if it's reasonable to recommend a full drivetrain replacement at this point. If OP rides in slop and grit, uses a crap lube, and has a poor cleaning/lubing regimen, it's possible that the whole thing is clapped out and would need to be replaced together. It's also possible that it's an overly conservative recommendation. If the chain is just worn, I find that I can usually get a couple chains per cassette. But I also keep track of chain wear myself and am able to catch it early so that I can keep my stuff running well.

I try to keep spare drivetrain parts (and brake pads and whatnot) on hand so that when I do hit my preferred wear threshold, I can replace what I need to replace without waiting for parts or an appointment at the shop. It's been a bit more critical to buy parts early and whenever I find them in stock given the shortages the past couple years.
 
#15 ·
IMO, testing the cassette and not making assumptions is the best thing for the customer, rather than jumping to conclusions and selling them parts they might not need. cassette wear is one of the few things I can only test by actually riding the bike. if I'm not sure, I'll have someone bigger than me ride the bike too and try to make the cassette skip with a new chain. if I doesn't skip, we advise the customer to replace the cassette on the next go-around when the chain is worn, and to bring it by to check the chain more often or just buy a chain wear indicator tool to use at home.
 
#48 ·
IMO, testing the cassette and not making assumptions is the best thing for the customer, rather than jumping to conclusions and selling them parts they might not need.

I also hate selling things that people don't need or want. Seriously it really bothers me and do my best to never do it.

As mentioned if I think someone will need to replace their cassette and/or chainring when replacing a chain I will tell the customer that but I'll also install just the chain if they absolutely insist. Not to brag but I'm very rarely wrong about that and always end up doing the cassette anyway after they discover the terrible skipping or chainring grinding.
 
#18 ·
Also, don't feel like you have to upgrade all at once. All the SRAM 12 speed stuff is interchangeable, so do it a piece at a time. I've had a bad run with chains lately. Mostly operator error, but am on my 3rd or 4th in a year. FWIW, I think GX chains are fine. X01 and XX1 are pretty much the same(from what Ive heard) other than the coating. I currently have an x01 now after bouncing a couple of XX1's off the rocks. Got tired of buying quick links and splicing. I think I had 5 quick links on my last one before I gave up. I only have an x01 now because they were out of GX. That said, it has been going strong for a while now. I think Ive only actually worn out one chain, but did replace the chainring and cassette when I did it, but the old cassette was actually damaged and I wanted to try an oval up front. Ran really well with all of it changed out.

Yeah, you shouldnt be wearing out a drivetrain in 700 miles.

On the tool front, I just grab a tool every now and then. I finally picked up a nice chainbreaker (you can use your multitool) and it is a godsend compared to that.
 
#19 ·
Buy your own chain-wear checker, the cheaper ones are often plenty good, and the Park one shows a very small amount of wear at the lower of the two wear indicators .5 at the lower end, and .75 at the higher end (Park), cheaper wear indicators start at .75 and have 1.0 at the higher end, I have a Spin Doctor brand cheaper checker tool too. I've changed quite a few chains that have just reached .75 and have not had to change chainrings or cassette.
.. When you buy a new chain, and remove the old one, (if you can) put 2 small finish nails side by side into something high enough to hang your chain on, to see how many links you need to remove from the old one, and to actually see how much longer the old one is compared to the new one, which is kind of interesting.
 
#21 ·
I would buy a chain and see how it goes. No skipping, no worries. Buy a chain checker. You can buy reliable chain checkers off eBay directly from china for less than 5 bucks. I had a park that I some how lost so I replaced it with a 3$ generic tool. Works perfect. Change chains as soon as they measure .75 and you can do 3 to 5 chains per cassette. 2 per front ring. Drive train parts are too expensive these days to not maximize their life span.
 
#22 ·
I work on my own everything because I was raised without much money so I had to, and also because in my adult life I've had professionals screw up enough things to realize that I'm more careful with my own stuff than anyone else. Goes for automobiles, bikes, house, whatever. If I can fix it I do. You can buy a lot of really nice bike tools with even half the $3K in service you mentioned spending at this particular shop. Personally I wouldn't set foot in there again, sounds like they've been giving the shaft to you and your buddies for years. It's a shame too because there are so many good shops out there, but one like this hurts them all. I had one like that in the area I used to live; I can't count the number of people that told me stories about how they took their bike in for the free break-in service and walked out with $200+ bills.

At any rate, lots of good advice here. I agree, get a chain checker, see where the one they are telling you to replace the drivetrain is. If it's not super worn, well, there's your truth about the shop you're dealing with. If it is, maybe it's not a bad shop after all. Replace the chain as needed and start buying the tools you need to take care of your bikes yourself. In the long run it's much cheaper, and you'll know it's done to your standards. I don't use any 12 speed stuff, but as I recall NX runs on a Shimano splined hub. I don't think you can go to GX or higher without changing over to XD, so you'll want to take that into consideration when you're thinking about upgrading. I'd also consider finding a different LBS to source parts.
 
#69 ·
Trails are mostly single track, but no sand. It was a very muggy summer/fall. Bought the bike in late august. Did ride it through the winter a little bit too. I do lube the chain regularly, try to keep it clean but it’s tough.

The cassette itself looks “good”, but that’s just me and a few people looking at it in the parking lot at the trails. Teeth look good. It doesn’t look worn or anything. It’s a lower end cassette from SRAM that came with the bike - it’s a heavy cassette and It’s not aluminum. I do plan on eventually upgrading it but I was hoping to get a year out of it before I do.
 
#25 ·
A 6" steel ruler graduated in 1/32" is cheap. Chain tools are reasonably inexpensive and indispensable.
Buy a new chain, check how it wraps around the chainring, if it shows too much gap as if the chain is riding up on the teeth, then the whole drivetrain probably needs replacement. If this is the case, I'd adjust the current setup, and ensure the B tension is right, soak that chain in some good lube, then ride the worn drivetrain until all the teeth are little nubbins (I'm exaggerating). Everything is just too expensive right now.
Once you replace the whole drivetrain, then keep an extra chain around and replace it regularly.
Back when I was an undergrad and racing with Temple U. our coach (who was also a pro-racer) could stretch a new chain in two 60-mile training rides. We'd be doing 23mph average and he would crush it on the hills. This is back in 9 speed days, by the way, so the chains were thicker and suffered less side-to-side deflection. If you're really pushing it in nasty riding conditions, you could probably wear out a chain pretty fast.

Phil Forrest
 
#26 ·
Depending on conditions I suppose the miles could lead to wear. I am a clyde and do put down some power. Add in numerous rides on crushed gravel surfaces when wet and I tend to wear out chains and cassettes pretty fast. The need to replace a low end cassette is is not surprising. I am in the midst of a new chain -> bad shifting -> see if i can adjust it away before buying a new cassette cycle myself. The real red flag to me is the front cog. I am still running my original front ring on my 1x11 fat bike after 4 years and 2500+ miles. I don't understand how a 1x system would need a cog replaced at 700 miles in any conditions save for the most extreme of gritty.
 
#27 ·
Worn chains ruin cassettes and chain rings.

When I ran SRAM GX chains, they either broke or were stretched by 500ish miles. The NX chain is even weaker.

A new chain may or may not work, depends how long you rode with a stretched chain. I can look at the teeth of a cassette or chainring and tell if they are damaged from a stretched chain, I'm sure the mechanic can too.

The correct fix that will give the best results is what the mechanic has said, period. If they only replace the chain, you'll be back complaining they didn't fix your bike properly in a week.

Get a chain stretch gauge and replace the next chain at 0.5 wear!
 
#28 ·
The correct fix that will give the best results is what the mechanic has said, period.
You had me 'til you said this.
I've encountered more bike shop mechanics that know less than I do about bicycle repair than those that know more.
So when it comes to shops, I start off as a skeptic. (Apologies to the many excellent bike shop mechanics out there -- there are some excellent ones.)
Anyway, new drivetrain in 700 miles... sorry, I'm not swallowing that without investigating more deeply.
It's possible, but very unlikely. I'd want to have a look at it personally before going along with that mechanic's kneejerk diagnosis.
=sParty
 
#29 ·
Check the hanger alignment, then get a new chain and try it, and learn to adjust the derailleur yourself for optimum shifting. 12 speeds are finicky with chain wear. Even if the chain has worn in 700 miles (entirely possible) it seems unlikely to me that it would have also damaged the cassette and chainring in such a relatively short time. I have had chain damage that has affected shifting before stretch has reached the critical value. And replace it with a higher end chain. They do wear better.
 
#31 ·
Bike has maybe 700 miles on it now. Is it worth buying a new chain and trying to adjust it myself? Or am I wasting my time? Is it really necessary to replace almost my entire drivetrain every six months? Or have to replace chains that are supposedly capable of lasting 2,000 miles, every 2-3 months?
It's absolutely possible that the chain is worn at 700 miles if your ride a lot in poor conditions and/or don't keep your chain lubed and cleaned. You probably have a ruler in your house. Google the method to check your chain with a ruler; it's actually a lot more accurate than any tool if you can line the ruler up on the pins correctly. The ideal chain is exactly 12 inches at 12 links pin to pin. They're almost always a bit longer even at the start. More than 1/16" and your should replace. Much longer and your whole drivetrain is probably trashed. Hard part is holding the ruler in place exactly at the center of the pin while checking.

And yes, you should learn to do this and all routine maintenance yourself.
 
#33 ·
Also… when installing new chain on questionable cassette… give it more than a spin in the stand. Sometimes takes a minute of loaded riding before everything will mesh. Many times ive been suprised that i didnt need to replace cassette. Watch worn chainrings they can hold chain and cause chainsuck.

Also xx1 chains last for ages if you keep them lubed.

Another tool to buy: dropout alignment tool. $40 for cyclospirit is a great investment.
 
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#34 ·
For what it's worth - as stated, the shifting issue isn't likely to be the worn chain.

Regarding chain/cassette wear - in the old days, if you waited too long you were basically SOL. But starting with quality 11sp, I've been amazed on how far I've let chains go and new chains just mesh fantastic with the same cassette. Old gen W/N rings, not so good tho - noise. But anyway back to the cassette - I had an V1, first year, original xx1 11sp cassette that I put thru at least 10 worn chains (should have been like 30+) and no skipping or ill effect. Extreme mileage. I finally changed it last year but I think it's still serviceable. Crazy.

^Part of the reason I don't mind ponying up for the expensive and light upper Sram cass. It lasts.
 
#36 ·
yeah I've got to say I'm blown away with how long x01 and xx1 cassettes last. I've only worn out two and I've been running them since 2013. I have three right now all have seen 3 to 5 chains. One skips in the 42t, the other two look like they should skip but they don't. I just keep changing chains at .75 until I get a skip which 100% of the time comes from the alloy 42t first. I wish there was a good supply of replacement 11 speed big cogs. All I'm seeing is 10 speed conversion options.
 
#35 ·
Doublebase, That mechanic is flat out wrong, You don't need a new drivetrain, you need a whole new bike. If the drivetrain is worn out at 700 miles, the bike is trash. I'll generously take it off your hands sight unseen for $50. I'm sure the same shop would be happy to sell you another bike. All sarcasm aside, I can't imagine a complete drive train replacement at 700 miles. If you ride in only sand and/or mud and never clean and lube your chain, MAYBE the chain would be worn to needing replacement at 700 miles, but I doubt it. Oh yeah, if you have legs like the Hulk and lay down huge amounts of power at all times, that would wear it sooner. I have over 2000 miles on a drivetrain and the chain still in within the normal stretch limits, I don't clean it every ride...really maybe every 5-10 rides and it still is in good shape. YMMV. Check the chain, replace if necessary and go from there.
 
#39 ·
Very true, but 700miles?!? That seems super short unless horrible conditions and poor maintenance. If it were an e-bike with 12 speed and poor chain care, I MIGHT be inclined to believe it. I have an e bike with 12 speed and over 1000 miles on it with zero measurable wear on the chain.
 
#38 ·
Bike is six months old, took it to the bike shop because the shifting has been a little off (it’s a 12 speed Sram).

First thing the mechanic does is he puts a gauge on the chain and says, “chain is pretty worn”. I say, ok, put a new chain on it. He says, no I won’t be able to adjust it. Need a new cassette and front cog/sprocket. He’s done this to friends of mine as well. I didn’t see him give any sort of visual inspection to the cassette or front cog. Just a gauge...boom...need a new drivetrain.

Bike has maybe 700 miles on it now. Is it worth buying a new chain and trying to adjust it myself? Or am I wasting my time? Is it really necessary to replace almost my entire drivetrain every six months? Or have to replace chains that are supposedly capable of lasting 2,000 miles, every 2-3 months?
I live near the beach and sand is everywhere. It eats up my chains and I go through them every few months no matter how much I clean the and lube the chain. I ride almost entirely on singlet track and dirt roads. My sprocket and drive chain are showing wear after 3000-ish miles and shifting isn’t as good as it was new but it is acceptable. I mean having to replace everything after 700 miles seems absurd.
 
#43 ·
I have found that a GX chain wears quite a bit faster than an XO1 chain and a GX sometimes has degraded shifting due to side link wear (I'm guessing) even when the chain hasn't stretched. When I rode an 11 speed, and on my wife's 11 speed, chain wear as a factor in shifting quality, seems to be less of a factor.

If you don't need or prefer the high/low end range of a 12 speed, I see no reason to get one, frankly.