mordenmarauder

I have a MF -TZ500-7 with extreme wear on the 14 and 16 tooth sprockets. As I have a spare cassette, I thought I would swap these 2 over. I expected to be able to get the 2 off by unscrewing them but doesn't seem to move. Are they threaded or fixed ie not replaceable? I'm sure someone can enlighten me

Andrew R Stewart 

Assuming you have your part numbers and terms correct (and this could very well be a poor assumption) don't expect a freewheel (the MF-TZ500-7) to accept cogs from a cassette. The images of the freewheel I can see suggest a commonly done threaded on last cog (and maybe the second smallest one too). Do know these tend to be very tightly installed and generally need specific tools to remove with less chance of harm (to the cogs or you). As complete new freewheels can cost about $20/25 buying a couple of $8 cogs is a questionable value. Add in that the old chain might not mesh nicely with the replacement cogs and you'll see why so many suggest a new cog set (freewheel or cassette) and chain to insure best wear and dependable performance. Andy

grumpus

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That's a cheap freewheel - £16.99 on Amazon. Parts are not available and probably not interchangeable with anything else. With extreme sprocket wear your chain is probably knackered too.

mordenmarauder

Thanks for the replies guys. I installed a new chain on this Carrera Parva I picked up for free because previous owner had a broken rear spindle. I found it slipping and on checking the 14T sprocket realised it was completely shot, the 16 T not quite so. I just ordered a replacement cassette but was curious as to see whether these 2 sprockets could be removed and replaced. I stuck it in the vice and hammered away with a cold chisel anti-clock. It appeared to be threaded but couldn't move it. Hence the post

Andrew R Stewart 

"I just ordered a replacement cassette" mordenmarauder

Again, I hope this isn't what you did actually order as a cassette won't interchange with a freewheel unless the rear hub is also changed out. So what did you actually order? A freewheel or a cassette? Andy

jimc101

From the sound of it, you maybe worth checking the complete bike and working out what need fixing and how much it's going to cost, a free bike can be more of a money pit than a bike that cost money

Bill Kapaun

I's suggest reading this-
https://www.sheldonbrown.com/free-k7.html

grumpus

I'd take that opportunity to replace the broken hub and worn freewheel with a freehub and cassette - freehubs are less likely to suffer bent or broken axles, and are standard on all but the cheapest bikes. Cassettes offer a standard sprocket interface* so you can swap sprockets easily.

* Actually a few standards, and different widths, but Shimano's design, also used by SRAM and many smaller manufacturers, is what you'll find on most entry- to mid-level bikes.

Kontact

Helluva lot easier and cheaper to just replace the axle than re-lace a wheel.

And the freewheel is also just $25.

grumpus

Assuming you can get the right axle for a no-name hub, and the bearing surfaces in the hub aren't knackered. Cheap freewheel hubs are just a bit too crap for me to contemplate saving one, rather than replacing it with a superior design.
I did point that out in an earlier post.

Kontact

Yes you did. Pardon.

This is 99% going to be 10mm threaded axle, commonly available at most bike shops for $5.

Overall, this is an inexpensive bike. It isn't necessarily throwing good money after bad, but is there really any reason to upgrade it? Replacing a broken axle and a worn freewheel is just maintenance. Keep the bike going until it is time to sell it and get a better one.

IMHO and all that.

grumpus

IME the cones will be worn enough to make proper adjustment impossible, at least on the drive side.
If you're going to buy new bits you might as well buy bits that will work properly. I'm biased because I've broken or bent most of the non-freehub rear axles I've owned, and I enjoy building wheels. But I'm also inclined to use stuff that's "good enough", and if it ain't broke don't fix it. :-)

Kontact

New cones are also common and cheap. My first MTB had a freewheel and never bent after some jumping

grumpus

And not universal.
My first MTB had Deore XT freehub, and some nice deep section Campy rims*, because I was heavy and strong and more enthusiastic than skillful.

* these rims were an oversize 26 inch version of the Omega V hardox, introduced around 1988, I can't find any reference to them online.

Kontact

I would challenge you to find a middle of the road hubset that wouldn't take a common replacement cone. They have a large, curved bearing surface for a reason - it works regardless of the precise shape of the hub race.

We don't need more reasons not to do the simplest things to maintain our bikes.