HalfPint

Hi,

I recently bought a used Trek 7300FX and I used a chain ware tool today and it told me it was bad. So with that said, I suppose I need help deciding what to buy. I only paid 150 for the bike, and I hoping to stay cheap, but I don't necessarily want to sacrifice quality either. Also, do I need to replace the front chainrings?

Thanks,
J

giantcfr1

No usually just the chain. A new chain should be reasonably cheap. Might be an idea to have a look at the rear cassette as they tend to wear much quicker than your front chain-rings. The chain-rings should last you for years. I was told once one cassette replacement to two chain replacements, but I don't know how true that is.

fairymuff

Start by replacing the chain. It's possible that the cassette needs replacing as well if the previous owner didn't replace the chain often enough. If that's the case you will notice quickly enough, as the chain will skip. If you replace the chain and it doesn't skip, you won't need to change the cassette. It's very unlikely that you'll need to replace the front rings.

HalfPint

Thanks for the responses guys. Although I know very little about how most of the parts on these bikes work, I'm learning to try and fix everything myself. Would this https://https://www.amazon.com/Shimano-CN-HG50-8-Speed-Chain-Black/dp/B0013EP4W6/ref=cm_rdp_product be an appropriate chain for my bike?

Thanks again,
J

fairymuff

You can use any chain that is suitable for an 8 speed drivetrain, so yes, the Shimano will work. Personally, I wouldn't go with Shimano as they use a somewhat odd pin system on their chains which makes opening and closing the chain more of a hassle than necessary. SRAM chains come with a so-called 'powerlink' which can (normally) be opened without tools.

Which reminds me: you will need a chain breaker to take the old chain off and adjust the length of the new chain. They look something like this:



And are usually included in the bigger multitools. You use it to push the pin out of one of the links to open it. If you don't have a multitool, now is a good time to buy one (with a chain breaker).

himespau 

I believe KMC brand chains also come with a power link (or master link), right?

fairymuff

They may well do. I've got some KMC powerlinks in my tool box, so their chains may well come equipped with them.

Tip of the Day: the most practical purpose of a powerlink on a chain is that it gives you a starting and end point when lubing because it stands out clearly from the other links.

himespau 

I've thought many times when relubing my chain my next chain needed one for that reason if no other.

fairymuff

Like I said: You can get just the powerlinks from KMC (as well as SRAM I think). I usually carry some spares when touring, but stuck one on my wife's new bike that came with a Shimano chain just for the purpose of lubing.

You can use KMC (and presumably SRAM) powerlinks on Shimano chains.

HalfPint

Alright, so the consensus is that I don't need a new cassette or chainrings and to buy an sram chain. I'm going to post some pics of my bike later, so you guys can tell me if you think I got a good deal if that's cool.

fairymuff

I'd say that you are unlikely to need new chainrings. You may well need a new cassette, but you will be able to tell easily once you've replaced the chain. If the chain skips, you need a new cassette. If it doesn't you don't.

Do post pics of your bike. Without pics, it didn't happen

RollCNY

Can also use 9 speed chain on 8 speed system. I have used SRAM's and KMC's, get whichever is cheaper as their is no practical difference.

HalfPint

HalfPint

Sorry to double post, but after I inserted the images, I couldn't add text because they were too large. Anyways, there she is. What are your thoughts considering I paid $150 for her?

UH60Hwkdrvr

I am by no means a bicycle mechanic, however, I have owned and worked on many off-road motorcycles with chain sprockets. You can tell when the sprockets are worn out when they no longer look symmetrical (like the ones in your picture). If it were my bike, I would seek the advice of a professional bike mechanic and then act on their guidance. I am guessing that the cassette you have displayed is worn out.

m.a.c.

giantcfr1

...but then the shimano cassettes are usually shaped that way to assist with gear changes. If you feel the gear changes aren`t smooth enough after you change the chain and tune it, then by all means ask the shop to take a look at it. My experience in Australia (I know maybe diff. elseware) is that the LBS is after a sale and tend to advise in their favour in the first instance.

HalfPint

Alright, well it does seem to be a bit rough whenever I switch gears, so I'm considering on just replacing the cassette. Is there a reasonably priced one that you guys would recommend?

fairymuff

Really, I'd start by changing the chain and only change the cassette if you notice problems (in particular skipping) afterwards. A Cassette will easily set you back another $30 (though being from the UK I'm not up with prices your side of the pond), and you'll have to buy two more tools if you want to change it yourself. I'd save myself the expense and only go there if needed.

Also: judging from that pic, you want to lube that chain. Shifting may well be easier after that.

HalfPint

Fairy,

I replaced the chain with https://www.amazon.com/gp/product/B000VPK58Q and after adjusting the rear deraileur a lot, my chain skips pretty bad. I'm thinking I need to buy a new cassette. I'm thinking about this one https://www.amazon.com/SRAM-PG850-8-S...pr_product_top, but I don't know which one to get. What does 11-32 and all that crap mean?

Thanks,
J

giantcfr1

Not actually crap. The numbers represent the number of teeth on your low and high geared cogs. This will / can govern which deraileur you use and how easily you want to pedal. Make it easy and just count the number of teeth already on your low and high geared cogs, on your old cassette.

fairymuff

Yes. If it skips you need a new cassette.

As said, the numbers are the number of teeth on the cog. The higher the high number, the lighter your low gear. The lower the low number, the heavier the tall gear.
11-32 is pretty standard for a hybrid, so that cassette will probably be alright. Bear in mind that you'll also need a lockring removal tool. (I think this one'll work on a SRAM cassette as well as a chainwhip to do the job.

HalfPint

Thanks for the replies guys all good info. Is the SRAM cassette a good choice?

fairymuff

Yes, it'll be fine. It's an entry level cassette, but your bike isn't top of the range either, so there's no point in paying more. Good price though at $20.