Bicycle Mechanics - Squealing issue, can't reproduce off bike

Please note that I'm new to working on my bike, so instead of just taking it in I'm trying to see if I can self fix. Here's the issue:

Bike now makes a loud squealing noise at times when I'm coasting. It is difficult to reproduce on the bike, but it happens when I'm going fast (above 20mph) and then hit a pot hole. The squealing starts and if I start pedaling even a little bit it immediately stops. I've noticed that the chain during this time goes slack, so when I start pedaling again it must tighten the chain and sort itself out. Because I'm new to fixing & identifying the problem, I'm not sure what's causing the noise exactly. I've ruled out the brakes (I think) as I've opened them up while riding to give extra clearance and the problem still happened. Other things that might help:

1) I "recently" changed the cables & housing - this was my first time doing it so maybe I screwed something up. I've ridden about 300 or so miles afterwards with no problem though, and shifting is very smooth and accurate.
2) Chain and cassette are also relatively new (about 500 miles or so on them)
3) Running Chorus/record parts with Record chain. Chain has quicklink on it.
4) Ksyrium wheels, probably have around 1500k miles on them. Don't think they have ever been serviced.

Any thoughts? I can't reproduce the problem on my workstand and can't clipout of the pedals without the problem "fixing" itself before I get off.

Thanks so much!

Something that should be lubed, isn't. The shock of the pothole causes the two surfaces to connect. When you start to pedal, everything is pulled back into alignment. As the chain goes slack, seems the dragging part could be the freehub. Take the cassette off and see if there is any sideways play in the freehub, try doing this as you rotate the freehub with your fingers. 1500 miles wouldn't be enough to start worrying about a freehub so this is only to eliminate things, unless you do mean 1500k miles?

get some one to ride around in circles around you?

The only part that is different between pedaling and coasting is the free hub! It is turning when you are coasting
and stopped when you are pedaling.

Hold the bike with the rear wheel off the ground and spin the wheel. Also check the rear wheel for bearing free
play!

freehub or ratchet. the chain slack is a good indicator

Help me out with the mileage on the wheels. 1500 miles is basically brand new and lubrication should not be an issue. 1500k miles would be 1.5 million miles, and they'd be well past needing service!

I believe the ksyrium freehub has a rubber seal between it and the hub flange. Sounds to me like your freehub body is loose (or the bearing has some play in it after 1.5 million miles ;) ) and when you hit a large bump the seal is displaced creating drag and a squeal. Pedaling causes it to reseat itself.

Remove the cassette and check the freehub for any play. It should move essentially not at all when you try to move it up and down, in/out or side to side.

BL

Ha yes - sorry. Not 1.5 million miles. If it was I'd be way to badass to worry about squeeks :p

They are fairly new - 1500 miles or there about, got them used but barely used - so who knows. I'll see if the freehub has any play - sounds like that's the issue. Will report back what I find!

It sounds like the freehub or freewheel needs to be cleaned and lubed. The tip off is the slack upper loop on your chain which shows that the freehub isn't quite free and is trying to spin with the wheel.

But, the fact that it starts after a bump or jolt means something else is probably going on. Double check that the axle isn't broken. Broken axles aren't always obvious because QR skewer in the center will keep the parts fairly close to inline. But there's enough movement that the axle can be out of line slightly and rub inside the spinning shell.

Ah ok - so it sounds like it definitely needs lubing and or maintenance. Apparently this sounds like a common thing and not a huge fix. Found something online about it after you guys said it's the freehub...

http://velonews.competitor.com/2006/10/bikes-and-tech/technical-faq/technical-faq-noisy-mavic-freehubs_101299

I'm betting there's a bunch of dirt/grit in there - it's very sandy here and I've been caught out in the rain a few times this year. Wish me luck! Good thing it's 32 degrees out and don't feel like riding much ;-)

Just to finish this out for anyone searching for this later on, a thorough cleaning and lubing of everything definitely solved the problem. Went out for a quick ride today, got the bike up to 38mph, coasted, and all is a-ok (previously it would make a squeal). In addition, my wheel is supremely silent. I've been used to the very very loud clicking the Ksyriums were making which honestly I liked because people could hear me. Good problem to now have. Opening up the freehub, all looked absolutely new (as it should have) but it was extremely gunked up with sand, dirt and overall grime. I ride in a sandy location and got caught in the rain (heavy at times) a few times this year.

For anyone who has this problem, I followed this video and it was exactly what I needed:
http://www.youtube.com/watch?v=FzoBeJ5HaOI

To note:
1) To a beginner it seems like a HUGE deal. It absolutely is not.
2) DO be careful of losing the little spring in the pawl. You won't really know what to look for until you do it, but lay down a white cloth on the floor or work table IN CASE the spring pops out.
3) Based on my conditions, I have a feeling I will need to do this right around whenever I need to change my chain
4) There's an end cap on the axle that just pulls off. Mine was stuck. It pulls off eventually.
5) Don't lose the washer. The washer and spring are easily losable parts.

Thanks again for all the help & I'm glad that nothing was broken! I'll still keep my fingers crossed though :thumb: