1998 Rockhopper drivetrain questions
09-02-15, 01:20 PM
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1998 Rockhopper drivetrain questions
I am wondering what all I need to replace to get this bike into shape. I measured the chain with the Park tool. Both the .5 and .75 fit in quite easily so the chain is done. From what I've read the cassette needs to be replaced too. The chainrings also appear to be wearing unevenly.
If I replace my chainrings does that come with a new crank/bearings/bottom bracket?
If not do those items need to be replaced too?
Can I change gearing of the cassette or chainrings without any problem or do I need to keep it stock gearing?
If I replace my chainrings does that come with a new crank/bearings/bottom bracket?
If not do those items need to be replaced too?
Can I change gearing of the cassette or chainrings without any problem or do I need to keep it stock gearing?
09-02-15, 01:37 PM
#2
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I am wondering what all I need to replace to get this bike into shape. I measured the chain with the Park tool. Both the .5 and .75 fit in quite easily so the chain is done. From what I've read the cassette needs to be replaced too. The chainrings also appear to be wearing unevenly.
If I replace my chainrings does that come with a new crank/bearings/bottom bracket?
If not do those items need to be replaced too?
Can I change gearing of the cassette or chainrings without any problem or do I need to keep it stock gearing?
09-02-15, 02:12 PM
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I am wondering what all I need to replace to get this bike into shape. I measured the chain with the Park tool. Both the .5 and .75 fit in quite easily so the chain is done. From what I've read the cassette needs to be replaced too. The chainrings also appear to be wearing unevenly.
If I replace my chainrings does that come with a new crank/bearings/bottom bracket?
If not do those items need to be replaced too?
Can I change gearing of the cassette or chainrings without any problem or do I need to keep it stock gearing?
If I replace my chainrings does that come with a new crank/bearings/bottom bracket?
If not do those items need to be replaced too?
Can I change gearing of the cassette or chainrings without any problem or do I need to keep it stock gearing?
8-speed cassettes in 11-32 are very common and easy to find. You can pick between the Shimano version which has even spaced shifts, or the SRAM version which has smaller shifts in harder gears and bigger shifts in granny gears.
Changing the gearing is not difficult if you want to make it higher (bigger rings, smaller cassette). Making it lower would need more new parts.
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09-02-15, 03:58 PM
#5
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To start with, just replace the chain.
See if that works. The Cassette might not be worn too badly.
If with the new chain you're missing shift, skipping teeth or ghost shifting, just replace the cogset.
No need to buy a new crankset or agonize over how to find chainrings before you know you need to. Don't borrow trouble.
Other than the chain measuring worn, how does it ride as is?
See if that works. The Cassette might not be worn too badly.
If with the new chain you're missing shift, skipping teeth or ghost shifting, just replace the cogset.
No need to buy a new crankset or agonize over how to find chainrings before you know you need to. Don't borrow trouble.
Other than the chain measuring worn, how does it ride as is?
09-02-15, 04:08 PM
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I doubt that your chainrings are wearing unevenly. It's likely you are seeing a few flattened teeth on the outer ring and thinking that they are broken somehow. This is a common error. If you do have flatten teeth this is part of the design of the rings and allows better shifting. A picture of the unevenly worn teeth will help confirm this.
Your bike should have replaceable rings, however, they are 5 bolt rings which are not common anymore. You'll need to find the bolt circle diameter which you can find by measuring between two adjacent bolts and multiplying by 1.7 to give you the diameter in millimeters. Here's a chart with various bolt circle diameters and an illustration. The BCD on your crank is might be a 110mm or it may be a 92mm
No. The original crank is a pretty good one for the era.
Number of gears has been addressed above. You can put any size chainring on this crank (i.e. number of teeth) that you want but you may have problems if you go much larger than 44 teeth. Mountain bikes have wide chainstays that don't accommodate large chainrings. A 48 tooth ring might work but it might hit the chainstay.
No. The original crank is a pretty good one for the era.
Number of gears has been addressed above. You can put any size chainring on this crank (i.e. number of teeth) that you want but you may have problems if you go much larger than 44 teeth. Mountain bikes have wide chainstays that don't accommodate large chainrings. A 48 tooth ring might work but it might hit the chainstay.
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Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
09-03-15, 06:57 AM
#8
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09-03-15, 07:02 AM
#9
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Let's back up - "chainrings are unevenly worn" may mean the OP thinks that the teeth that are shorter to improve shifting are worn (as cyclocommute suggested). Besides, chainrings take a very long time to wear to the point of replacement. Secondly, if one is replacing the crankset rather than just the rings there's a good chance that the BB will need replacement as well to maintain proper chainline. Finally a 1998 Rockhopper should easily fit a 48 tooth chainring.
Last edited by cny-bikeman; 09-03-15 at 07:07 AM.
09-03-15, 07:50 AM
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Depends on the crank being replaced and what it is being replaced with. Although the Specialized crank has a funky bolt behind the arm that is difficult to deal with, it's not a bad crank overall. Additionally, rings seldom need to be replaced as a set so replacing the outer ring if it is actually worn would cost around $40. Replacing it with an Acera, for example, would definitely be a step down.
I believe this crank also has an inner BCD of 58mm which means it can take an inner ring of 20 teeth no problem and might even be able to take an 18 tooth inner. That kind of low has uses in mountain biking and touring for which this bike could easily be used.
But then I doubt if anything needs to be done to this crank at all.
I believe this crank also has an inner BCD of 58mm which means it can take an inner ring of 20 teeth no problem and might even be able to take an 18 tooth inner. That kind of low has uses in mountain biking and touring for which this bike could easily be used.
But then I doubt if anything needs to be done to this crank at all.
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Plan Epsilon Around Lake Michigan in the era of Covid
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Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
09-03-15, 07:53 AM
#11
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If the OP decides he needs a new BB, again depends on what RH you have, but on mine the BB shell is 73mm width, just FYI because square taper BBs come in a lot of different sizes.
09-03-15, 07:59 AM
#12
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Depends on the crank being replaced and what it is being replaced with. Although the Specialized crank has a funky bolt behind the arm that is difficult to deal with, it's not a bad crank overall. Additionally, rings seldom need to be replaced as a set so replacing the outer ring if it is actually worn would cost around $40. Replacing it with an Acera, for example, would definitely be a step down.
09-03-15, 08:16 AM
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I have found some Alivio cranks on-ling for $45 but that's about as low as they go.
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Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
09-03-15, 08:25 AM
#14
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I've owned a couple of versions of the Specialized crank and, although I haven't owned an Alivio, I do work with them at my local co-op on a very regular basis. They aren't nearly the quality of the Specialized crank nor are they regularly available for $35. That's the wholesale price for a new Alivio crankset. $35 is Acera territory which is an even lower quality crank.
I have found some Alivio cranks on-ling for $45 but that's about as low as they go.
$29.99.
09-03-15, 09:02 AM
#15
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oldsrocket1965, Is the Rockhopper new to you? If you're going to use it, rather than flip it, it's worth it to be prepared to replace the drivetrain, chain rings/crank set, chain, and cassette if required as well as overhauling the hubs and head set.
I have had a '98 Trek since new that has seen untold miles and hard use. I've replaced the chain at least three times and the cassette once, but the chain rings are still pretty good. I think you maybe looking at sculptured teeth on the chain rings, which can look like uneven wear. A photo would be of great help to determine which case.
Most mountain bikes of the era has 22-32-42T chain rings. You can change gear inches (gear ratios) around to suit you, but you can't change the number of available gears without replacing the shifters too.
Brad
I have had a '98 Trek since new that has seen untold miles and hard use. I've replaced the chain at least three times and the cassette once, but the chain rings are still pretty good. I think you maybe looking at sculptured teeth on the chain rings, which can look like uneven wear. A photo would be of great help to determine which case.
Most mountain bikes of the era has 22-32-42T chain rings. You can change gear inches (gear ratios) around to suit you, but you can't change the number of available gears without replacing the shifters too.
Brad
09-03-15, 04:58 PM
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Yeah, if you're running a worn chain, it will mess up the chainrings and the cassette. If the cassette is original, I'd certainly look to changing that out, it's a cheap fix. Chainrings aren't super expensive, but I don't recall if they're replaceable on the crank (on mine a Specialized own brand one). The crank on my bike broke an arm, so I just replaced it with a $35 Alivio crankset off Amazon.
If the chainrings can be replaced, you won't need a new crank or bottom bracket. Even if you replace the crankset, assuming you get a square taper one, you won't need a new bottom bracket.
My '98 Rockhopper has the original bottom bracket, and still spins like a champ. My crankset arm broke due to metal fatigue a couple of years ago.
Depends what you mean by changing the gearing? You can get a cassette with different range. But if you want to upgrade to 9, 10 or 11 speed gears, you'll have to change a lot more parts (shifters, cassette, derailleur, maybe crankset).
If the chainrings can be replaced, you won't need a new crank or bottom bracket. Even if you replace the crankset, assuming you get a square taper one, you won't need a new bottom bracket.
My '98 Rockhopper has the original bottom bracket, and still spins like a champ. My crankset arm broke due to metal fatigue a couple of years ago.
Depends what you mean by changing the gearing? You can get a cassette with different range. But if you want to upgrade to 9, 10 or 11 speed gears, you'll have to change a lot more parts (shifters, cassette, derailleur, maybe crankset).
By changing gearing I just mean changing it from 22/32/42 to 28/38/48. But the main reason for asking that was that when I looked online the cranksets I found were all 28/38/48. But I was also wondering if the cassette can be changed to different gearing (still 8 speed). Would I just need a different chain if I were to change the gearing?
09-03-15, 05:08 PM
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You might find that a compatible and good square taper crankset doesn't cost any more than replacing the chain rings. This is frustrating if you like maintaining old stuff instead of throwing it away, but it's true. It's because of the markup on piece parts, and because the aftermarket is aimed at selling upgrades, not maintenance. If you replace the crank set with a similar one, you might need to replace the bottom bracket, not because it's worn but because it's the wrong length. If you replace the crankset with a newer type it will use a new style of bottom bracket with a hollow shaft.
8-speed cassettes in 11-32 are very common and easy to find. You can pick between the Shimano version which has even spaced shifts, or the SRAM version which has smaller shifts in harder gears and bigger shifts in granny gears.
Changing the gearing is not difficult if you want to make it higher (bigger rings, smaller cassette). Making it lower would need more new parts.
8-speed cassettes in 11-32 are very common and easy to find. You can pick between the Shimano version which has even spaced shifts, or the SRAM version which has smaller shifts in harder gears and bigger shifts in granny gears.
Changing the gearing is not difficult if you want to make it higher (bigger rings, smaller cassette). Making it lower would need more new parts.
09-03-15, 05:10 PM
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09-03-15, 05:15 PM
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To start with, just replace the chain.
See if that works. The Cassette might not be worn too badly.
If with the new chain you're missing shift, skipping teeth or ghost shifting, just replace the cogset.
No need to buy a new crankset or agonize over how to find chainrings before you know you need to. Don't borrow trouble.
Other than the chain measuring worn, how does it ride as is?
See if that works. The Cassette might not be worn too badly.
If with the new chain you're missing shift, skipping teeth or ghost shifting, just replace the cogset.
No need to buy a new crankset or agonize over how to find chainrings before you know you need to. Don't borrow trouble.
Other than the chain measuring worn, how does it ride as is?
I just got the bike last weekend. The first few times I rode it while pedaling the pedals/crank would actually "lock up." I would have to pedal backwards and try to start going again. I just rode it again this morning and didn't have any issues. The bike has twist shifters which I am not used to (I have triggers on my other bike) so I don't know if I had just not totally shifted correctly or what. I had never had a bike "lock up" like that though so I was a bit concerned and I still am unsure if it had to do with shifting or something just in the gears and chain.
09-03-15, 05:34 PM
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I keep reading that the 8 speed stuff is just garbage and that they don't make any decent 8 speed parts anymore. Is this really true? I mean this bike is going to be used as a street bike and possibly occasionally used on some light trails, so maybe the parts that are still being made for it are adequate. I would like to keep the bike as original looking as possible (I like the brushed aluminum/chrome look of some of the parts), but if it doesn't make financial sense or if the newer cranksets/bottom brackets are much higher quality then I guess I wouldn't mind updating.
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09-03-15, 05:37 PM
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I doubt that your chainrings are wearing unevenly. It's likely you are seeing a few flattened teeth on the outer ring and thinking that they are broken somehow. This is a common error. If you do have flatten teeth this is part of the design of the rings and allows better shifting. A picture of the unevenly worn teeth will help confirm this.
Your bike should have replaceable rings, however, they are 5 bolt rings which are not common anymore. You'll need to find the bolt circle diameter which you can find by measuring between two adjacent bolts and multiplying by 1.7 to give you the diameter in millimeters. Here's a chart with various bolt circle diameters and an illustration. The BCD on your crank is might be a 110mm or it may be a 92mm
No. The original crank is a pretty good one for the era.
Number of gears has been addressed above. You can put any size chainring on this crank (i.e. number of teeth) that you want but you may have problems if you go much larger than 44 teeth. Mountain bikes have wide chainstays that don't accommodate large chainrings. A 48 tooth ring might work but it might hit the chainstay.
Your bike should have replaceable rings, however, they are 5 bolt rings which are not common anymore. You'll need to find the bolt circle diameter which you can find by measuring between two adjacent bolts and multiplying by 1.7 to give you the diameter in millimeters. Here's a chart with various bolt circle diameters and an illustration. The BCD on your crank is might be a 110mm or it may be a 92mm
No. The original crank is a pretty good one for the era.
Number of gears has been addressed above. You can put any size chainring on this crank (i.e. number of teeth) that you want but you may have problems if you go much larger than 44 teeth. Mountain bikes have wide chainstays that don't accommodate large chainrings. A 48 tooth ring might work but it might hit the chainstay.
Thank you for the link!
09-03-15, 05:39 PM
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Let's back up - "chainrings are unevenly worn" may mean the OP thinks that the teeth that are shorter to improve shifting are worn (as cyclocommute suggested). Besides, chainrings take a very long time to wear to the point of replacement. Secondly, if one is replacing the crankset rather than just the rings there's a good chance that the BB will need replacement as well to maintain proper chainline. Finally a 1998 Rockhopper should easily fit a 48 tooth chainring.
09-03-15, 05:43 PM
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My '98 Rockhopper (the OP hasn't stated which one he has, I have the one with rigid cromoly forks) has a BB with a 110mm spindle. The crankset I replaced the broken OEM one with was recommended to have a 113mm spindle, a difference that wasn't large enough to matter, the chainline was fine. I have ridden the bike without issue for over 1000 miles with this crankset (Alivio M410 FYI).
If the OP decides he needs a new BB, again depends on what RH you have, but on mine the BB shell is 73mm width, just FYI because square taper BBs come in a lot of different sizes.
If the OP decides he needs a new BB, again depends on what RH you have, but on mine the BB shell is 73mm width, just FYI because square taper BBs come in a lot of different sizes.
09-03-15, 05:47 PM
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oldsrocket1965, Is the Rockhopper new to you? If you're going to use it, rather than flip it, it's worth it to be prepared to replace the drivetrain, chain rings/crank set, chain, and cassette if required as well as overhauling the hubs and head set.
I have had a '98 Trek since new that has seen untold miles and hard use. I've replaced the chain at least three times and the cassette once, but the chain rings are still pretty good. I think you maybe looking at sculptured teeth on the chain rings, which can look like uneven wear. A photo would be of great help to determine which case.
Most mountain bikes of the era has 22-32-42T chain rings. You can change gear inches (gear ratios) around to suit you, but you can't change the number of available gears without replacing the shifters too.
Brad
I have had a '98 Trek since new that has seen untold miles and hard use. I've replaced the chain at least three times and the cassette once, but the chain rings are still pretty good. I think you maybe looking at sculptured teeth on the chain rings, which can look like uneven wear. A photo would be of great help to determine which case.
Most mountain bikes of the era has 22-32-42T chain rings. You can change gear inches (gear ratios) around to suit you, but you can't change the number of available gears without replacing the shifters too.
Brad
I am considering changing the shifters just because I am not that excited about the twist shifters. So I'm wondering if it would make sense to just upgrade it all to 9 speed. But again, I'm not trying to spend a fortune on this bike either. I would like to just be able to ride it for awhile.