(Not a) Bottom bracket screech.

[AlMorpeth]

My first post on this site.
I have a Lynskey Procross titanium framed bike that I am starting to fall out of love with, when going down hill and stop pedalling, I can only describe as a screeching noise reverberates through the frame, if I start pedalling again the noise stops, if I back pedal there feels like resistance in the crankset and the chain goes slack. Initially there was a Praxisworks push fit bottom bracket fitted, I put new bearings in which seemed to make a difference for about 100 miles and then the noise returned. I thought the solution to the problem was to throw money at it! I brought a new Hope unit, which I duly fitted........but with no success, the noise persists.
I love this bike and initially thought it was the one bike that I would keep, but I am coming to the end of my tether with it, as I sound like a World War Two Stuka dive bomber going down hill.
Has anyone experienced the same issue and managed to resolve it?
Thanks in advance for any advice.
Alan

 

[Sharky]

Check your freehub. Sounds more like it is sticking a pawl, causing the cassette to turn into a fixed gear.
Dismantle, clean and apply a little oil.

If you have another rear wheel, this would prove/disprove this possible cause.

 

[Cycleops]

Could indeed be the freehub. Remove the rear wheel and turn the cranks by hand and then spin the cassette. You'll soon see where the problem lies.
If the freehub is the culprit try flushing it out with WD40 or similar. If that doesn't work dismantle it and inspect. Might need replacing.

BTW to the forum.

 

[Ming the Merciless]

Also check the jockey wheels. Sometimes they can cause a screeching sound and resistance if dry. A bit of grease can sort it.

 

[Ming the Merciless]

You need to consider which parts are moving against each other when you hear a screech. Parts that aren’t moving I.e. cranks / BB won’t be the cause.

 

[si_c]

You need to consider which parts are moving against each other when you hear a screech. Parts that aren’t moving I.e. cranks / BB won’t be the cause.

Very much this. Sounds like a drivetrain clean and a front and rear hub service is in order.

 

[fossyant]

What are the wheels. If Mavic it could be the screech of death. You'll need to give them a good clean as the freehub uses a 'plastic' bushing on part of the freehub.

 

[AlMorpeth]

Thank you all for your replies, it sounds like I had wrongly assumed it was the BB. I will give the drivetrain and freehubs a clean and service this week. Fossyant, the wheels are Mavic Ksyrium. Cycleops thanks for the welcome.
Alan

 

[si_c]

Thank you all for your replies, it sounds like I had wrongly assumed it was the BB. I will give the drivetrain and freehubs a clean and service this week. Fossyant, the wheels are Mavic Ksyrium. Cycleops thanks for the welcome.
Alan

Easy assumption to make - I assume all the noises on my bike come from the BB but probably only 1 in 3 actually do.

Oh and

 

[Paulus]

Thank you all for your replies, it sounds like I had wrongly assumed it was the BB. I will give the drivetrain and freehubs a clean and service this week. Fossyant, the wheels are Mavic Ksyrium. Cycleops thanks for the welcome.
Alan

An easy way to check for BB problems is to drop the chain off off the chainwheels and spin the cranks. Any resistance, play or grinding will be instantly apparent.
As posted above, take the back wheel off and spin the hub by hand, again checking for problems.

ps, welcome to the forum.

 

[Big John]

I think the slack chain gives the clue. Sounds like the freehub. Cycleops suggests a liberal spraying of WD40 and I'd definitely try that before attempting to service the freehub. If you do decide to service it then I hope you have lots of patience. There are videos on YouTube that show you how to do it but there are endless tiny bearings that suddenly become very animated when they see daylight and go everywhere if you're not careful. An easier solution is to source a new one 😉

 

[fossyant]

Try and drop a bit of chain lube between the hub body and freehub. The plastic bushing is at the inner side. I've had the screech a couple of times on one set of wheels, but they haven't done it now for a few years. I'm running 4 sets of Mavic wheels. Aksium, Ksyrium and two sets of Crossrides.

 

[rogerzilla]

Mavic howl.

Separate axle with allen keys in the end. Pull off freehub. Oil the nylon bushing with mineral oil. Reassemble.