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another fixer hits the road(pics)(11 posts)

another fixer hits the road(pics)jsbx
Mar 27, 2003 10:19 AM
Hi, first post to this list. Wondering if anybody here rides in the SoCal San Gabriel Valley area?
Here are some pics of a project recently completed:

65" gear
What's with the left-side drivetrain?Straightblock
Mar 27, 2003 11:31 AM
Is that a mistake? How do you keep everything together?
Now, that IS different! nmp chop
Mar 27, 2003 4:32 PM
Different, and self-destructingStraightblock
Mar 27, 2003 5:01 PM
The cranks are on the wrong sides and the wheel is backwards. The cog will want to unscrew from the hub under normal (forward) pedalling, and the pedals will even want to unscrew themselves from the cranks. I'm guessing he put it together in a hurry, and hasn't ridden it very far yet. If he had single-sided pedals instead of the Speedplays, he would have caught it right away. Still, I have to say it's a beauty.
not really that bad...jsbx
Mar 27, 2003 7:06 PM
This bike actually belongs to a friend, but I've set up and ridden bikes like that in the past. The cog is held securely by a lockring. If the pedals weren't Speedplays, I'd just switch the pedal spindles to make 'em work that way--they really don't unscrew themselves because bearings turn much easier than threads. That said, the bike was put back to normal a few weeks ago.
Mar 28, 2003 5:36 AM
Why was it set up that way to begin with?

I'm not picking a fight, just interested.
boredom, butjsbx
Mar 28, 2003 9:22 AM
there actually is a reason to set up a fixed gear left hand drive: before the internet, it was hard to get track-specific hubs with reverse-threaded lockrings, so people would just redish a road freewheel hub with a cog and a bottom bracket lockring. The problem was that if you rode brakeless, you risked catastrophic failure when stopping. So the lesser of two evils was to set the drivetrain up on the left so that your cog wouldn't come off when you really needed it to stay on. You then either found a tandem left crank arm or reversed your pedal spindles and you'd be set. That colnago has a proper track hub, but we were bored that day. You can actually feel a difference when pedalling!
Pedal threading explainedStraightblock
Mar 28, 2003 9:11 AM
Sheldon Brown explains it better than I could:

Pedal Threading


The right pedal has a normal thread, but the left pedal has a left (reverse) thread.
The reason for this is not obvious: The force from bearing friction would, in fact, tend to unscrew pedals threaded in this manner. The fact is, however, that it is not the bearing friction that makes pedals unscrew themselves, but a phenomenon called "precession".

You can demonstrate this to yourself by performing a simple experiment. Hold a pencil loosely in one fist, and move the end of it in a circle. You will see that the pencil, as it rubs against the inside of your fist, rotates in the opposite direction.

Ignorant people outside the bike industry sometimes make the astonishing discovery that the way it has been done for 100 years is "wrong." "Look at these fools, they go to the trouble of using a left thread on one pedal, then the bozos go and put the left thread on the wrong side! Shows that bicycle designers have no idea what they are doing..."

Another popular theory of armchair engineers is that the threads are done this way so that, if the pedal bearing locks up, the pedal will unscrew itself instead of breaking the rider's ankle.

The left threaded left pedal was not the result of armchair theorizing, it was a solution to a real problem: people's left pedals kept unscrewing! I have read that this was invented by the Wright brothers, but I am not sure of this.

Note! The precession effect doesn't substitute for screwing your pedals in good and tight. It is very important to do so. The threads (like virtually all threads on a bicycle) should be lubricated with grease, or at least with oil.
Pedal threading explainedjsbx
Mar 28, 2003 9:43 AM
Sorry...I didn't mean to imply that I know better than you or bicycle designers and engineers; I just haven't had problems with that in the past. Sheldon Brown himself had a bike set up this way. He didn't like the feel, as there is a very perceivable difference. Here's my bike---everything's normal, the way the engineers designed it to be:
Mar 28, 2003 10:13 AM
One of my riding buddies & former teammate has one just like it, but with the complete original Record group. He hasn't ridden it in years, and I've been trying to get him to part with it. If I can talk him out of it, a bigger problem may explaining it to Mrs. Straightblock...
Maybe it's a tandem captain's crankset??Alexx
Mar 28, 2003 1:38 PM
Believe it or not, these things do exist! Rings on the left-side crank-nearly bought one for my fixie. Thought that maybe I could run fixed cogs on both sides, a captain's crank on the left, regular on the right, and run 2 chains! now that would be unique!