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8 speed to 6 speed alien technology fix?!?!

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8 speed to 6 speed alien technology fix?!?!

Old 05-21-19, 11:28 PM
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8 speed to 6 speed alien technology fix?!?!

Hello! I'm a brand new fish on this forum and also to biking, in all honesty. I can't seem to find much on here for my problem, please pardon me if it's been asked before. I'll get right to it though! (Please bear with me here, I can't post pictures)

I traded some small tile work for a Specialized Sirrus recently and it had some problems. It looks like it's from around 2012 based on google images, these are decent bikes and I want to treat it right. It appears that someone has taken this bike and attempted to make the rear gear set into a 6 speed. It doesn't have the stock wheels on it, I think. They are the same diameter though. It still has the 8 speed shifter/derailer. Pretty sure someone just put a 6 speed cassette on it and called it good to make it appear sellable. It rides "okay" and shifts pretty well, despite this molestation. I still want it corrected though, low gears are dicey. Somehow, the chain hasn't jumped off from going over limits. Aside from all of that, everything else on the bike is in great condition!

How in the world do I fix this? Will I simply need a new cassette and maybe a spacer? Or is this like a new hub/axle/wheel/cassette sort of thing? Current cassette is a 6 speed Shimano MF-TZ20. Derailer is a 200CX with a matching 8 speed shifter.

Last edited by BlackEx; 05-22-19 at 01:04 AM. Reason: Adding year/generation of manufacture
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Old 05-22-19, 05:54 AM
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The original rear wheel probably got damaged. It may be best to find another rear wheel that will take an 8 speed cassette. You'll also need to check the spacing between the rear dropouts and get the wheel to match.

I recently put an eight speed cassette on a ten-speed wheel I got from Craigslist with no problem at all.

If you find a wheel, you'll also need to adjust the derailleur and cable to make it work.

Is there a bike co-op in your area? That would be a good place to start, for both the parts and a mechanic to help out.
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Old 05-22-19, 07:42 AM
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New wheel and new 8 speed cassette. Also suggest a bag of flaming poo on the porch of the person you got it from.
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Old 05-22-19, 08:02 AM
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What you have on your rear wheel is a freewheel, not a cassette. In order to upgrade to 8 speed you will need a new rear wheel.
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Old 05-22-19, 09:18 AM
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Others above are correct - the bike has a 'freewheel' hub and to put 8 speeds on it you need to replace the wheel.

As for the chain not jumping off the ends of the cogs, there are two philips-head screws on the derailleur who's only function is to control the limits of movement on either side. You should adjust these screws when installing a new cassette or wheel and they should not need to be touched again.
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Old 05-22-19, 09:24 AM
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I put my C&V 6 speed freewheel hub wheels in modern steel frames with 130 width rear dropouts
with new axles and a bit of added spacer in the left axle end,,,

around 1990..
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Old 05-22-19, 12:17 PM
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Thanks for the info, guys! Really! Helps me a ton. I'll get some measurements and come back to this thread later tonight. I may have a question or two about what to look for when buying a wheel, spacer, etc.

I like the flamingo poo idea btw. I don't think this guy even knew about it! It had been sitting for a couple years. I put down like three small pieces of tile for this bike so I am not too hurt if I have to give it some TLC.
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