Dont be a deutchbag... put on at least a front brake.

dont be a "deutchbag" and condescend to people. i could be chain tension...if you're using a road crankset with a smaller bcd, it is possible that you flexed the chainring (not exactly likely, put possible). glad you're not dead. I've done the same thing on a few occasions, and i ride a pretty tight chain...doubt me if you want, but i'm pretty sure i just flexed something that I wasn't supposed to....yeah, i dunno.

-jason

Thanks for the constructive responses and thanks Shants for that ****ing crazy story. I was feeling sick to my stomach just imagining that.

Many people have said that my chain was too slack... I really don't think that it was! I have seen far, far slacker chains in real life and in pictures on this forum. I will check this **** out today. What about the "once you go slack you never go back" thing?

Anyway I attribute this incident mostly to poor skidding technique. I am also a big guy, 6'3", 215 lbs + loaded bag, and I ride hard. I have a fuji track frame. Could it have flexed enough to do this? How could my chainline be off (stock BB + sugino 75 + surly track hub)? The chainring looks fine, no side to side deformation. I will take a closer look today.

i hate slack.

also, the foot on the back wheel seems to work surprisingly well whenever i've had a problem. unless you're going mach 10 like in shants case.

speaking of slack:
http://cs-people.bu.edu/shoffman/pics/main/bob.gif

Does the stock BB mate up correctly with the Sugino 75? I don't know, just asking.

... or if you are wearing road shoes (slick bottoms with no grip) and they are wet. Luckily, I was in the uber-burbs at the time, and I just ducked onto somebody's lawn.

I am not quite sure... There is very little clearance between the chainstays and the cranks, and the chainline looks fine. I guess I need to measure it, but I feel somewhat confused by Sheldon's explaination of measuring chainline. I would love to get the matching 75 bb but $$ is a little tight.

its the drop outs. Im willing to bet you have had the bike a while and have taken the rear on and off more than a few times. get a chain tensioner, or two.

would you mind explaining this? I certainly have taken the rear off and on many times. Does this screw up the dropouts somehow? I am sure that fuji dropouts are not the best, but wtf?

Happening to me during monstertrack. Very inconvenient.
Chainring was bent ever so slightly.

Ive done it numerous times on langsters and pistas and will bet fuji tracks are similar.

on my Langster the dropout had normal wear over time and one day I began mashing really hard through and intersection and heard a loud pop, didnt know what it was and kept riding. later I noticed my chain was realy loose so I tightened it and the same thing happened the next day, a few times. the force of mashing and skidding would yank the wheel forward in the dropout, not even enough to visibly tell with the wheel on, but the chain sure was loose. Ive done it on other peoples bikes too and its not a good feeling in traffic. I got a surly chain tensioner and never had that problem again.

the fact that you heard the pop but your chain didnt break (+ your size) makes me believe the same is going on here.

only when I am in davis and thats just because the cops have nothing to do.

so here we have a guy who almost got killed because his chain [for one reason or another] failed to stop him. thus far only one guy has suggested this dude puts on a secondary means of braking, and he gets STFU'd for being "condescending"? wtf?

to the OP: I'm sure you're capable of braking on your own without a front brake, but if something similar happens a few days/months/years down the road and you aren't so lucky, you've got only yourself to blame.

i'm not for outlawing brakeless bikes, mind you. this just seems like common sense after an incident like the one you described.

Some would say it is common sense to prevent ever having an incident like the one that was described

I agree with my boy Tangsooyuk or whatever hahaha. As he said, when you sprinted, it pulled the wheel farther up into the track end (making the chain slack). Then later it was derailled. Check the inside of your chainstays to see if there is any tire wear on it (then that is definetely what happened).

Glad you are okay.

As for the whole running brakes/ not running brakes ****: On my track only bike I obviously don't have a brake. On my street bike I run a front brake. There is really no reason not too, you can push everything soooo much harder, and not worry about getting ****ed up. I'm not really saying that you should run a brake, just stating my observation.

I totally agree with all of this. I should be using a front brake, I sort of said this in my OP. This is not a question of whether I should have a brake (I should and this incident proved it) I was just asking for thoughts on the mechanical explanation for my chain derailment as to avoid this in the future.

Also just to be clear, I did NOT almost get killed, I did not feel that my saftey had been even remotely threatened, it was like 11:00 at night and there was very little traffic. The only reason I even tried to stop is because there were 2 cars trying to turn left. I did not almost die. However, I fully understand that this could have happened at a much more inconvienent time potentially causing me harm. It was a good lesson to learn.

I tightened up the chain a little more today and tightened the crap out of the nuts. Drivetrain seems lovely. I will install a brake soon. I don't have to use it if I don't want or need to. But I just might. I also agree about being able to go faster with a brake. More confidence to bomb the **** out of ****.

Also it is not my intention to be preachy about the use of brakes. Do whatever makes you happy.
:beer:

[QUOTE=wnatw]so here we have a guy who almost got killed because his chain [for one reason or another] failed to stop him. thus far only one guy has suggested this dude puts on a secondary means of braking, and he gets STFU'd for being "condescending"? wtf?

i defintely condone brakes on track bikes..i was "stfu'ing him" for pretty much calling him a ******bag for NOT having a brake...see how that works?
-jason

... okay, I've got to just go and say it:

I'm building the next bike with front and rear brakes, a flip flop and a freewheel. I miss bombing flights of stairs.

I'm sorry ... next I might even build another road bike.

*sigh* I know I let you all down.

this reminds me of a similar story with a tandem bike flying down a long long hill, brakes worn to nothing, lots of mass going faster and faster. i've also heard stories of brakes heating rims up so much that they pop tubes and cause blowouts at high speeds going downhill. yikes.

i had derail problems for a short time, lbs cleaned up my dropouts and we put on some beefier nuts in the rear. it hasn't happened since.