starrats

They have lasted 4000miles which seems incredible to me, but have now worn down to piranha teeth. The chainrings are the 53-39T version and came with the Trek 1000 SL (https://www.trekbikes.com/uk/en/bikes/2007/archive/1000#). The bike has a Bontrager Sport crankset, but the chainrings themselves have no brand that I can find. I would love if you could give me some ideas of chainrings which have very good quality and good performance so I wouldn't have to replace the whole crank set.

The bike has an Sram PG 850 8 Speed Road Cassette 12-26, which I found based on loads of helpful information from this website .

Also, could you please advise me on buying a new chain as I have never bought or fitted one myself and would like to do both.

Just to clear it up; the bike has two chainrings at the front(53-39) and an 8 speed cassette at the back (26-12). Am I right in thinking that every time my pedals rotate 360deg. on the highest gear, the wheels will rotate 4.42=(53/12) times, or am I missing something?

I am looking to spend around £50/$78 on the chainrings and the chain, can I still get qood quality? Endurance is more important than performance to me right now.

Many thanks,
James

contango 

From you quoting a price in pounds I'm guessing you're in the UK.

If you know the size and the tooth count you can probably find something to match on www.chainreactioncycles.com - you can also get chains there.

If you're replacing the chain and chainrings you'll most likely need to replace your cassette as well. When you replace the cassette you may need to readjust your rear derailleur (I did, as I realised when the chain kept skipping between gears).

Replacing the chain is relatively straightforward. I'd recommend using a chain with a powerlink/missing link/master link/whatever-anyone-else-calls-it. That's a special kind of link you can open and close with no tools, which means you can remove your chain easily. That makes it easier to clean the chain, the jockey wheels etc.

If you've got an 8-speed cassette you'll want an 8-speed chain. I use 9-speed and have been impressed with the KMC X9 chains. I think the equivalent for 8-speed is KMC X8 - you can buy a regular grey one, a silver one, a blinged out gold one, and assorted lightweight derivatives. I just go for the regular one but then I'm not interested in pimping my ride or saving an ounce or two. Check it against your old chain so you can shorten it (you'll need a chain tool to remove however many surplus links are necessary), then use the master link to join the two ends together.

Replacing the cassette may sound daunting (it did to me at first) but it's pretty simple. You'll need a chain whip and lockring removal tool. Take the back wheel off, put the lockring removal tool into the lockring (the bit next to the smallest sprocket) and use the skewer to hold it in place. Then use the chain whip to stop the cogs turning while you turn the lockring removal tool with a suitably sized spanner. It may take a bit of force but once it gives it will unscrew, then you can slide the cassette off and the new one on. Some or all of the sprockets may be loose so make sure they go on the right way around (look at the way the old one came off if you're not sure). Then put the lockring removal tool back in and crank it the other way, and your cassette is changed. You may need to adjust your rear derailleur limit screws and/or cable tension - if the chain doesn't engage all the gears correctly you'll need to adjust it.

I've never replaced chainrings so can't say from experience, so a Google or Youtube search will probably give you something more useful than me speculating.

Budget wise, I'd be surprised if you can do it all within £50 especially if you don't have the tools you need. A cheap 9-speed chain will run to about £10-15 and chainrings look like they'll cost around £25-30 upwards, depending on quality and toothcount. Both chainrings and a chain will run, at a guess, to somewhere close to £70 or so, and with a cassette on top you'll be nudging against £90. If you need the tools as well, I paid something like £11 for the chain whip, £5 for the lockring removal tool and £12 for the chain tool. I already had a bunch of allen keys and spanners I could use.

Although it looks like you'll break your budget it's still pretty cheap when you think the tools will last multiple uses and even £90 in parts over 4000 miles works out only 2.25p/mile

FBinNY 

I'd start with just the chain. Chainrings usually last far more than 4,000 miles, so yours may in fact be OK, even though they don't look it. When the chain is installed you can use it to gauge the condition of the chainring by using the tip of a screwdriver to pull it outward from the ring at the 3 o'clock position (halfway around).

The amount the chain pulls away is an indicator of the chainring condition. A new chain on a new ring will barely pull away. On a worn ring you'll be able to pull the chain out farther. If a new chain can be pulled far enough that you can see 1/4" of daylight between the chain and ring the ring is toast.

fr333zin

If you do need to replace the chainrings, a really good place to look in UK is St John's Street Cycles https://www.sjscycles.co.uk/chainrings-dept49_pg1/. You first need to know the Bolt Circle Diameter (BCD) of course. Measuring between two adjacent bolts will tell you. 130mm BCD is most probable and the distance between adjacent bolts will be 76.4mm if this is the case. I'd be happy to use Stronglight Zicral or TA Alize chainrings. Prices for Shimano chainrings seem to be too high imho, I guess that is the price of not being very informed! Ribble Cycles also often have on-line bargains so also worth a look here: https://www.ribblecycles.co.uk/product/t/chainring

I am sorry to tell you that your budget should be 1.5x to 2x if you need to replace all three parts

starrats

contango, the master link chain impressed me as I know how difficult it is to do with a hammer and a nail and a concrete window seal, will probably invest in the chain link remover this time. I have aleady replaced the cassette and havn't used it since.

FBinNY, that's very interesting.
First bike shop: "bike's not really worth repairing, you'll need new shifters/chainrings/chain, (list went on) which will just cost too much", second " shifters are fine just new cables and chainrings and a chain" and now you tell me this, which is great news by the way thank you. I will swap the chain and see how much it's slacking, great to know that tip. I'll remember them quotes aswell as it sums up my bike situation perfectly, well hopefully only before now!

fr333zin, thanks for the info on (BCD)! You're right it is 76.4mm(centre to centre). I can't measure exactly what the BCD is without taking off the chainring, so I'll assume that it's 130mm as you have said.



Thanks for all the tips and URLs, am actually looking forward to fixing it now, was very lazy to do it before.

DOS

+1 on just replacing the chain only.

I would bet that the front rings and cassette still have life with only 4000 miles on them. You'll know pretty quick if the cassette is shot because new chain will slip as you ride if cassette is overly worn. On chainrings, even if you find one is shot via the FBINY method, both may not be so you may only need to replace 1 ring, not both. (I don't live among a lot of hills so I wear out my big ring faster than my small)

As for your bike shops, I wouldn't go back to the one that told you to ditch the bike. It sounds like they were talking a complete upgrade to 9 or 10 speeds. There are still 8 speed drive train components on the market, so no need to change shifters as long as they work, and wearing out drive train components is normal wear and tear that does not require a complete upgrade or breaking bank to address. For example, here is your exact SRAM 8 speed 12-26 cassette for $22.00.
https://www.amazon.com/SRAM-PG850-8-S.../dp/B003WOQ5DM

starrats

Thanks DOS! I will only change the chain to begin with and see what happens. That's a very good find because mine was £23 from ebay if I remember rightly.

They said upgrading the bike might be cheaper because they thought it could be the front gear shifters that were gone, when it was only the cheap gear cables. I wont be going back!

HillRider

After 4000 miles the cassette, at least the cogs you ride most in, will probably skip on a new chain so plan on changing it too. However, 4000 miles is very low mileage on chainrings, particularly big ones like 53 and 39, and I'd be amazed if they are really worn out unless you ride on a sand beach all the time. I will typically get 30,000 miles and more on a road crank like yours.

So, go ahead and change the chain and cassette but keep the chainrings until you are sure there is a problem with them.

contango 

Better to use a chain tool. The master link makes it all academic unless the chain breaks (or the one-off first use if you have to shorten it) because you can literally open it with your fingers. It takes a little practise though.

Both times I've changed the chain on one of my bikes I've also changed the cassette. I use Shimano Deore cassettes which are cheap enough to not worry about them (£17.99 from chainreactioncycles.com). I've put north of 3000 miles on my Rockhopper and as a heavy rider I'll be putting more strain on stuff than many riders would. For good measure I bought it when about all I knew of cycling was that you turned the pedals and the bike went forward, so I tended to do things like pulling away in a high gear and put extra strain on the drivetrain as a result.

When I swapped out the cassette on the Rockhopper (to be more precise I had the LBS do it because I had a tour coming up and didn't want to make a hash of it) I could see the difference in the tooth shapes between my cassette and a new one. Most of the time I use the middle 3-4 sprockets on the cassette and the difference was quite surprising.

I've never had to replace a chainring as yet.

Gear cables should be cheap. My LBS swapped out a cable on my tricross for something like £12 - that was parts and labour together. If you buy online and do the work yourself I'd reckon on half that and maybe a little less.

Looigi

Hmmm. I put 5k miles on a year and get 4-5k out of a chain and 12-15k out of a cassette and rings. That's road riding mainly in dry conditions and keeping the chain well lubed with a wet lube. A severely worn chain will wear teeth much faster. I replace the chain at 1/16" elongation over 12".

zukahn1 

For chains one of the best for the price for a 8 speed set is the KMC Z7 chain in silver which can be found online for about $12 in the US with shipping not sure about UK pricing with shipping in the 116 length which is standard for most road bikes it just slips on easy with the master link and is easier to adjust if needed using a stanard chain tool than shimano or Sram chains.

starrats

Thanks for the advise on the cassette. I'm sure I would have had to replace it aswell but someone stole the whole back wheel so I replaced that. No lectures please, main reason was lazyness mixed with a bit of stupidness. Thanks

starrats

The cassette I put on my new back wheel was a SRAM PG850 12-26 teeth, 8 speed cassette, it cost about £23.

Thanks zukahn1, I did get a KMC chain: KMC X-82 (6 7 8 speed), with a master link, and it only cost £7.91 incl postage: you're the second to give KMC approval on this page so I thought I'd try it out.

FBinNY 

No lecture here, shat happened. However it's not your laziness or stupidity at fault, it thievery that's to blame, and maybe the laziness or stupidity of people who see stuff like this every day and do nothing. Sad truth is that much bike theft wouldn't happen if passersby just shouter "hey you! what are you doing!"

FastJake

+1

You already got the new cassette so replace the chain, leave the rings alone until you're sure they're bad. Many newer chainrings appear to be shark toothed even when brand new. They are specially shaped for better shifting. If you're concerned get some really good close up shots of the rings and post them here.

contango 

From the way the thread is going I'd suggest buying or borrowing a chain extension gauge to see if your chain needs replacing yet.

Most sources I've seen suggest replacing it when it's about 0.75% extended. It sounds like you may not need to replace the chainrings, the cassette could be quite new, so unless the chain needs replacing you could just save your money. A cheap chain gauge comes in under £10.

FBinNY 

A cheap 12" (obsolete in the UK) or 31cm ruler is even less than that. There's no need to spend for a special tool when on you already own will do as well or maybe even better. (don't want to start that debate).

Using a ruler measure 24 pitches (pin to pin on center, for 24 half links) of a chain tensioned enough to pull out any slack, and if it measure more than 306.5mm (12-1/16") replace the chain.

If 31cm is longer than a commonly available (cheap) ruler, you can measure over a shorter length. it's the same math convert a multiple of inches to mm, for nominal length, multiply by 1.05 to 1.075 for acceptable wear length.

FastJake

But I thought Great Britain was part of the UK. Wouldn't they use the English system there?? Sorry... I had to.

With the chain off the bike measuring might be easier if it's hung from something, but on the bike I would advise against using less than a 12" ruler. Too small a scale for a good measurement.

FBinNY 

We're talking about an eyeball measurement of 1/16" over 12". If that's possible, certainly taking something a hair less than 1/16" over 11" isn't significantly harder. Remember we're talking a guideline, not a precise line that makes a critical difference.

Looigi

Exactly. And a ruler is the best tool for the job because it directly measures chain elongation without factoring in roller wear, which is much less consequential.