goodtimes5

I came across a beat up road bike complete with shifters and broken rear derailleur. I want to still use the bike, so I removed the rear derailleur and its shift cable. I shortened the chain to wrap around my 42 chainring and one cog on the cassette, essentially creating a single speed bike. The front derailleur still works, but I don't plan on using it since the chain is too short to fit around the rear cog and the 52 chainring.

Is this setup safe? I can pedal and ride along at a slow speed on the street, but I want to make sure everything is fine mechanically before I ride hard.

crushkilldstroy

Assuming the chainline is straight, it should be fine. If it isn't, it might try to shift on you.

tradtimbo

Even if it is straight, you could run into some problems. It is a less than optimal setup, and can be outright dangerous. A setup like your talking about is used in emergencies when you need to get home, and you have a busted derailer. Read this article to understand more:

https://timmcgivern.wordpress.com/200...the-wrong-way/

goodtimes5

I went on a test ride and actually had the wheel pulled out of one side of the dropouts. The wheel jammed up against the side of the frame, and I had to carry the bike home.

Would it be cheaper to convert to single speed or to somehow break the cassette apart and add some spacers? I'm not sure if the cassette can be split apart from the looks of it.

kyselad

This has nothing to do with your drivetrain.

the_don

yes, if the wheel slips in the dropouts, it means you didn't tighten the wheel in the dropouts!

tradtimbo

It absolutely DOES. Read the article I posted.

simply put, the bike down shifts in the rear when the bike flexes and the chain sways. The chain is too short in the larger cog, and forces the rear wheel forward. Even when you have your wheel on very tight, the force can pull it free.

This happens all the time with this setup. It doesn't always rip the wheel off, sometimes it bends the frame if the wheel is in there tight enough.

Most common, is the drivetrain binds up and you have to get off the bike and fix it.

Get a Single Speed conversion kit for a cassette wheel. If you have vertical drops, you'll need a chain tensioner as well.

not required

+1 when I used a set up like this I would pull the wheel out every time I rode it without fail, and most times bend the wheel axle. It really isn't a cool way to go single speed

Vinci

If the deraileur isn't totally hosed, you can just set the limit screws to keep it on a single rear cog. Then it is essentially just a chain tensioner.

tradtimbo

Great suggestion!

fuzz2050

I rode my bike this way for about 6 months while I saved up for a real rear wheel. Once i had it set up right I had no trouble at all. While the catastrophic failure posted earlier can happen, it is unlikely, especially considering how many bikes are equiped like this, and that guy seems to be the only person it's happened to.

Of course, using a derailer as a tensioner makes a lot more sense, as there's no risk (however small) involved.

JacoKierkegaard

This.

goodtimes5

I took a look at the damage done when the wheel slipped out of the dropouts. The axel of the wheel is horribly bent such that I can't put the wheel back into the dropouts, and the dropout on one side of the frame is also slightly bent.

I would like to add that before the ride, I had tightened the bolts as tightly as possible. This is why the frame bent - the wheel was secure on the frame, but I guess the forces described above were too great and pulled the rear wheel forward along with the dropout of the frame.

At this point, the cost of repairs or replacement parts would be more than the bike's worth.

tradtimbo

This same exact thing happened to me once. I also know someone else it has happened to. Its more prone to happen on some clusters than others.

shecky

I'm not sure I understand. The frame is flexing enough to essentially derail the chain? If this is the case, how does a single speed conversion kit fix the problem? The frame would still be flexing enough to derail the chain, only this time, the chain derails onto empty space instead of a larger cog.

If the problem is a flexible frame, the solution is a more rigid frame.

r0ckh0und 

I rode a bike this way for quite some time without any issues as long as I used a bolt on.....QR always slips. I usually use the small chainring and the middle of the freewheel.

xcx4x

my single sped is exactly like the posters.

i just took off the derailer. i have never heard of this danger. i am going to have to call bull**** until i am convinced.

a casette at lowest gear vs a single speed cog.
wouldnt BOTH cause stress on the frame upon pedaling?

xcx4x

i really do not understand the danger. what if the smallest gear on the casette was perfectly lined up with the chainring at the pedals?

tradtimbo

A set up like you describe may work fine if the next largest cog is a few teeth larger, the chain tension is high, and you don't mash heavy and sway the bike. Its fully explained in the article. Read carefully if you would like to understand. It doesn't happen with every setup.

Every frame flexes. One function of a chain tensioner is to remove slack from the chain during frame flex (a RD also does this). A BMX freewheel (single speed) has taller teeth. No ramps or pins or cut off teeth. Same as a fixed gear cog.

This is not something you can doubt or call bull ****. It has been proved countless times by people who have had to cut their chain due to a busted RD and then carefully ride home. Carefully so they don't accidently shift to a larger cog. Its happened to me, friends, and will likely continue to happen to people wanting a cheap single speed bike.

If your running an OLD ass Regina freewheel with a large increase of teeth between the cog you want to use and the next larger, you should be all set. But why the hell would you want a 5lb anchor weight (the Regina) holding you down when you can't even use all the gears?

If you doubt me (which is ridiculous by the way) then go try this out on a couple different setups and try sprinting a couple miles.