Slipping one piece crank

I've just converted a mountain bike to fixed for polo, but there is a slight slippage backwards and forwards, on occasion on the one piece crank. If I do it up any tighter then it's a struggle to pedal.
Any ideas people?
Cheers.

is it the crank or is it a slack chain?

also -

one piece crank

2 piece crank

3 piece crank

slack chain

http://www.londonfgss.com/thread24236.html

slack chain

It's the crank.
Chain = tight as.
Thanks.

At the risk of getting hosed down with the forum flame thrower have you tightened the hell out of your lockring?

Just seen the pics above Malaysian, soz. They don't show on phones, but yes, it's a 1 piece.
cup = not too tight, lock ring = tight as hell, right?
I had the same problem with the same rear wheel and chain on a different frame with a different crank and BB, but it's definitely the crank moving. Clearly I'm the common denominator though.

I'm fitting a new chainring tonight so I'll have another go. Maybe I should get one of those men-types to have a go at the lock nut after me, huh?

Left my flame retardant suit at home. Shit.

cup = not too tight, lock ring = tight as hell, right?

Lockring on your wheel rather than you crankset? I know you said it's your cranks but definitely sounds like the problem I had with my cog unscrewing a little then tightening back up...

Aye, I meant the lockring on the wheel- nine times out of ten it's that.

It does feel like the cranks are rocking slightly despite the chain being tight, leading you to suspect the crankset, but (in my experience) it's because I have not tightened my lockring sufficiently and the sprocket is unscrewing itself slightly when I resist the cranks.

try taking your cog and lockring off, locktite em, put them back on tight as possible, go and stomp on the pedals up a steep hill, then at the top tighten up your lock ring as tight as poss. repeat.

if that doesn't fix it I'll eat my hat

See now, that's why I come here. You guys are genius.
If it's happened on both bikes then it must be the wheel.

Thanks very much.
Will report back (if interested).

Roll over to either SE or N drinks tonight if you want drunk people to fiddle with your bike.

There is the possibility that this will lead to it being fixed, probably a higher possibility earlier in the evening.

SE has the advantage of Nhat attending who works in a real proper bike shop and everything.

Ha, thanks very much. I think alcohol got me in this position in the first place.

Don't have it with me today as it (will be) is my polo bike.
Plus I have a mallet to construct before tomorrow too.

Would like to pop down for beers regardless another night though. I reckon I owe a few people some pints by now.

Cheers guys.

Hat eating time Malaysian, I'm afraid.

The rear lock locking is a tights as a... and it doesn't move when I jiggle the pedals.
It is just the BB that moves when I put pressure on.
If I tighten the cup any more then it's too hard to pedal, and the lockring is also as tight as the afore mentioned.

Confused.

I'll grab the ketchup and my top hat also.

How is the chainring attached to the crank?

All the photo's in this thread are blocked- I can only see attachments for some reason btw.

The slippage most likely has nothing to do with your rear cog or lockring or how much you tighten the bearings up on the bottom bracket, it will be because the interface between 1 piece crank and chainring is usually nothing more than a peg in a hole. Peg on crank fits into hole on chainring, and it's usually nothing like a tight fit which is fine when it's only used to pedal forward - the peg rests against one side of the hole and exerts force on it - but if used fixed the peg will move back and forth in the hole giving the feeling of slippage. It will wear badly and really isn't up to the job.

So 1 piece cranks are shite in essence?

I swear it's the BB moving though. I can see it with my eyes!

I haven't put any pictures up of the offending BB but I can do if it will make a difference.

Still don't get how a BB can slip if it's 1 piece and the barings are fine and the cups look decent to me. it wasn't slipping when it was geared but is now, with prev chainring and new one.
Granted the fit on the peg is shite, but it's not this that is moving.

Thanks for your input guys.

I think it's got to the stage where the offending bike needs to be taken to one of the drinks for someone to have a look at- West's is tonight, although I have no idea if that is near you.

Excellent excuse to go to the pub.
I'm South so maybe next week.
I'll be the one on the beater with the White Lightening wheel disks.
Oh dear.

Hat duly eaten...

You look young to be riding a fixed gear.

This is how I roll - the original fixed gear, before it got "fashionable"

you may note the track geometry, 9 spoke rear wheels, original brooks and integrated fork/stem/headset...

A the classic Mo' handlebars.
I have envy.

envy you should...

lookin to upgrade to one of these for time trialing

aerospokes, chrome dropouts and even tighter geometry

so if you wanna make an offer on the other I can drop off?

I'll take the Brookes and the Mo Bars if you split.

So 1 piece cranks are shite in essence?

I swear it's the BB moving though. I can see it with my eyes!

I haven't put any pictures up of the offending BB but I can do if it will make a difference.

Still don't get how a BB can slip if it's 1 piece and the barings are fine and the cups look decent to me. it wasn't slipping when it was geared but is now, with prev chainring and new one.
Granted the fit on the peg is shite, but it's not this that is moving.

Thanks for your input guys.

No, they're fine for what they're intended for. They aren't intended for fixed wheel bikes. Especially a fixed wheel polo bike.
I don't really get how a bottom bracket can "slip".
It rotates, it's meant to. If it didn't go back and forward it would be stuck?
Only other movement i can envisage from a bb would be play in the bearings which would be a knock or rattle. This would be side to side.