martyr13

I'm trying to help my dad fix his Schwinn High Timber mtn bike. It came with a 7 speed 13-28 dnp cassette. The smallest sprocket broke in half, and the teeth of the second smallest are almost completely worn (the bike is less than a year old). What cassette can I use to replace it? Any low-end name brand component will suffice. I would just like to order the correct size. I was going to order the Shimano HG50, but I noticed the lockring on the Shimano takes the Park Tool FR-5. My FR-5 does not fit the dnp cassette, does this mean they're not compatible?

dscheidt

A lot of bike-shaped objects have screw-on freewheels, not cassettes. See https://www.sheldonbrown.com/free-k7.html
and if you can't figure it out, post some pics.

martyr13

---Unless there are freewheels that slide onto freehubs, it's a cassette. Multiple separate sprockets slide on and off the freehub. I would like to know if anyone has ever replaced the off-brand dnp cassettes with name brand cassettes, and how I go about figuring out which one to replace it with.

JiveTurkey

It might be Shimano-compatible. What kind of shifter and rear derailleur is on it? If it's Shimano or lower-level SRAM, then any Shimano/SRAM-compatible cassette with the same number of cogs will work. There are a few caveats though.

martyr13

The derailleur is a Shimano Tourney, but the shifters are off brand (Gripshift, I think). One more thing, I just noticed the freehub has three tiers. Is that normal on mountain bikes? I'm pretty sure my road bike freehub only has one level.

bikinfool

As in the freehub having three differing diameters? Never saw one like that myself. Not normal for a Shimano/SRAM cassette, they use a uniform freehub body...got pics?

dscheidt

I've worked on some of these things. They're utter pieces of bike-shaped crap. (It tells you what Pacific Cycle think of them that they don't admit they make them on their website...) They all had crappy DNP freewheels. Not freehubs. If they've started using cassettes, I wouldn't count on being able to get a replacement. But you could talk to Niagara, as they sell the parts....

larry_llama

is it possible that it is a freewheel - but that the cogs have loosened from the freewheel?

This is a distinct possibility with crappy freewheels.

I would be very VERY surprised if that bike had a 7 speed cassette.

If you can send a picture.....

my vote is that it's a heavily damaged freewheel, not a cassette - they just used a cassette style construction method when manufacturing the freewheel.

Your FR-5 will not fit a freewheel, you will likely need a "falcon" freewheel remover (FR-7)

dscheidt

fr-1 (standard shimano) on the dnp freewheels I've worked with.

Doohickie

Any chance of taking it to a bike shop? They will hate you but they are more likely to be able to get it apart and figure out what you need. What you're running into, by the way, is exactly why they are referred to as Bike Shaped Objects. They are built to be cheap and gently or rarely ridden. Any kind of hard miles and they break and are not built for repair.

You may consider just getting a new wheel. If dad weighs less than 200 lb. you can probably just get a straight freehub replacement wheel for maybe $50 plus the cost of the new cassette.

martyr13

A number of things to respond to here. Sorry about the delay, but I thought I was supposed to get email notification when someone commented on this thread, but I haven't gotten one since the second reply, anyway...

Of course I could take it to a bike shop. I'm not impoverished, I just like tinkering. I'm posting here, because I want to figure out how to fix it, and to learn more about bikes in the process, even pos bike shaped objects.

I really don't need the tool to remove the cassette. The cassette is already removed, because it's broke. I was mentioning the removal tool, because I was wondering if it was possible for a Shimano cassette that gets tightened with the FR 5 could possibly be compatible with a cassette that cannot be tightened with the FR 5, but I think it's pretty obvious at this point that they are not compatible.

I've never removed a freehub body before, so I'll probably try to do that, and replace it with a proper one, or like someone else said, just by a whole new rear wheel. Thank you for all your responses.

cny-bikeman

One note not related to the mechanical issue. If there is that much fatique/wear on the outer cogs your dad may need to ride with some folks who can teach him about gear usage. He's doing neither his muscles, his heart nor his bike any favors by riding primarily in the small cogs. Higher pedaling revs/min using a variety of gears and avoiding cross chain combos will get him in better shape and keep his bike in better shape.

dabac

The thing in your pic is a disassembled freehub, not a cassette. The right freewheel puller will get it off in a jiffy.

reason

Definitely a freewheel. Newer ones with hyperglide style teeth use splined rather than threaded cogs. Anyway, if you don't want to buy the puller and you happen to have a nice big vice grip and pointy screwdriver, you can remove it destructively. https://www.parktool.com/repair/readhowto.asp?id=46

Basically you use a hammer and punch/pointy thing to unscrew the front plate (it's reverse threaded so you want to go clockwise). Then the splined part with all the little ball bearings will fall out. Finally you just grip the core piece with the vice grip and give it all you got (this one is threaded normally). Any new 7 speed freewheel should screw right back on the hub.

DX-MAN

Yup, it's a freewheel; check Nashbar or the LBS, or even get hold of one of the manufacturers of the big-box BSO's (they all have 800-numbers on top-tube decals), and get one from them. Use the FR tool, unscrew the old, install the new, adjust your shifting, ride, adjust again. Repeat until the new freewheel is so tight you think it'll never come off.

martyr13

Ok, so I need to buy the FR-1 freewheel puller. Between that and a vice, will that take off that entire body? Also, when I purchase the seven speed freeweel to put back on the wheel, should it be an HG freeweel, or no?

larry_llama

You can get away without the tool if you use the destructive removal method mentioned above. Installing the new freewheel does not require a tool.

Any 7 speed freewheel will work. They are probably all HG now. You can get one for $10 or less if you go to the right shop (or co op)

clean and GREASE THE THREADS WELL before screwing the replacement freewheel on - and be certain you aren't cross threading it ;-)

martyr13

I bought the fr-1, pulled the mangled freewheel off easily. I bought the Shimano hg-37 13-28, which is the same size as the old one. I cleaned and greased the threads, and it screwed right on. After quite a bit of fiddling with the barrel adjusters, I got the bike to shift through its full range of gears. It seems to be shifting cleanly, and pedaling relatively smoothly in the stand.

But, when I'm pedaling it under load, there's this creaking, grinding, rubbing sound coming from (I believe) the back wheel (It's really hard to isolate it, since it only makes the noise under load). I can feel it in my feet while I'm pedaling. It's just not pedaling cleanly.

cny-bikeman

Not practical to isolate without seeing the bike. Get thee to a shop or person familiar with bike repair.

martyr13

If you don't have anything useful to say, keep your comments to yourself. I'm asking these questions, because I'm trying to become a person more familiar with bicycle repair. Obviously, I can take it to a shop, and have it fixed, and if all else fails, that's what I'll do. I have a specific problem, and I'm trying to understand it. It's not like I'm unaware there are establishments called bike shops that fix bikes. A lot of people have been helpful so far, and I've made progress, but if I listened to people like you, I would never learn anything, because I would outsource any challenging task that came my way.

bikinfool

Perhaps there was more going on back there than the messed up freewheel. Might try overhauling the hub, checking the axle in the process.

cny-bikeman

I did not say you should not learn and I did not say you had to go to a shop, but I worked at shops for years and had no problem showing customers what the problem was with their bike after I fixed it, or even immediately if it was not worth putting up in the stand and charging for it. Not every shop is like that but many are. There are also bike clubs and bike co-ops that have repair clinics in some places, as well as individuals who might be willing to help. Check Craigslist if you have one in town for a bike forum, for example

If you truly want to learn more the best way to do it is in person. You can learn a lot online but not how something is supposed to sound, feel or look.

If you still want to try to solve this or any other problem online then describe exactly what conditions the sound occurs or does not occur - gears combinations being used, continuous sound or in sync with wheel or pedal revolutions, etc. Here's an example of the possible causes with your description so far (sound and vibration carry, so may or may not be in rear).
Pedal bearings
Crank bearings
Bent chainwheel
Worn chain
Dirty chain
Rear hub bearing loose
Worn freewheel cogs
Loose spokes
Broken frame
Too high a gear for speed
...and probably some I have not thought of.

roberth33tiger

have you checked your chain for wear? new freewheel-old chain, not good