Author Topic: Thorn eccentric bb alternatives  (Read 2057 times)

humedavid

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Thorn eccentric bb alternatives
« on: June 16, 2021, 09:02:23 PM »
Hi guys,
I was just wondering if anyone uses an alternative to the Thorn eccentric bottom bracket shell, what type and if they are they happy with them.
I've got an old ish Raven with the black shell. Lot of marks on the shell now so I've been thinking of going a different route and trying a different shell.
Cheers
« Last Edit: June 16, 2021, 09:05:22 PM by humedavid »

PH

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Re: Thorn eccentric bb alternatives
« Reply #1 on: June 16, 2021, 10:16:41 PM »
Are you asking if there's an alternative insert to use in the same way, or if you can use one of the alternative systems? 
Those other systems are the wedge type and those I've seen and the one I've used were a smaller diameter than the Thorn shell so wouldn't fit. I haven't researched them so there may be one that fits, I'm not a fan, they require more maintenance and have a tendency to squeak.  Or there's the pinch bolt type Thorn now use which would require serious frame modification.  These are my preferred option, even more so now Thorn have simplified it to two bolts rather than the unnecessary four.
If you're looking for an alternative insert to use in the same way, there may be some. but they'll all function in the same way, so I can't see any advantage.  I prefer the pinch bolt type. but there's nothing wrong with the set screw type you have, the issue with wearing indents into grooves arises with too frequent adjustment, which just isn't needed.
I'd just get a new one and adjust less frequently.

humedavid

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Re: Thorn eccentric bb alternatives
« Reply #2 on: June 20, 2021, 09:22:04 PM »
Thank you for your reply.
The main reason is that my Raven does a double click when I pedal harder. I've tried many things, changed pedals, tightened and greased chainring bolts, greased cranks, removed the eccentric shell, filed off protruding metal bits, greased it, changed the whole bb to a new one, greased the seatpost etc. It still does it.
Getting a new shell from SJS Cycles is not a easy option as I'm in Europe mainland. But I think that's my inevitable next step. I did have a quick look at the different bb shells and you're right, they're different in sizing.

JohnR

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Re: Thorn eccentric bb alternatives
« Reply #3 on: June 20, 2021, 10:06:24 PM »
I've tried many things, changed pedals, tightened and greased chainring bolts, greased cranks, removed the eccentric shell, filed off protruding metal bits, greased it, changed the whole bb to a new one, greased the seatpost etc. It still does it.
What condition are the chain, chainring and sprocket? I ask because I had some similar disconcerting noises on a bike with a Gates CDX belt drive. The noise sounded mechanical so I checked every nut and bolt several times but the noise persisted. Eventually I gave the belt a good scrubbing (they are meant to be maintenance free but still collect muck) and the noise immediately went away.


Danneaux

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Re: Thorn eccentric bb alternatives
« Reply #4 on: June 20, 2021, 10:51:51 PM »
Quote
I've tried many things...
Try checking the saddle, saddle rail clamp, seatpost binder bolt and shim.

In my experience, Brooks saddle rails (if yours is so equipped) can "work" a little where they are riveted/peened to the rear steel cantle plate and so produce a click/double click with each pedal stroke. Inverting the bike and applying a tiny drop of oil (don't get it on the saddle leather) to the interface can cure a click of this sort for many years.

With other saddles I've had, the rails can click in the clamp. In that case, a thin layer of electrical tape can help. Check torque on your seatpost binder bolt as well. I had a double-click produced by one of my Thudbuster seatposts that turned out to be a faulty pivot bushing. Documenting my steps in an email to Cane Creek resulted in a warranty issue of new pivots and the tool to install them. Problem (and noise) solved.

Noises -- especially clicks -- can easily telegraph through a bike frame and appear to come from somewhere else. When I first encountered this I did the same as you, focusing on the drivetrain. I didn't conquer the problem until I checked the saddle end of things. Handlebar stem clamps can do it too. If you use the Forum's search tool and enter the terms "click" and "noise" (no quotes), a lot of suggestions will come up.

Best of luck on finding and resolving your clicking noise, David.

Best,

Dan.

mickeg

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Re: Thorn eccentric bb alternatives
« Reply #5 on: June 20, 2021, 10:58:05 PM »
I see Dan just responded, but I did not edit out my saddle comments which he already covered.

... my Raven does a double click when I pedal harder. I've tried many things, changed pedals, tightened and greased chainring bolts, greased cranks, removed the eccentric shell, filed off protruding metal bits, greased it, changed the whole bb to a new one, greased the seatpost etc. It still does it. ...

Clicking noises that you think are coming from the bottom bracket area are very hard to diagnose.  What I try to do is stand next to the bike with one foot on the ground and the other foot on the pedal, the pedal in the position where it would cause the click (likely horizontal crank arm).  Hold the bike with one hand on the saddle, other hand on the handlebar holding the rear brake so the bike does not move.  (My brakes are setup for USA, rear brake on right, thus I stand on right side of bike for this, if your rear brake is on the left, stand on the left.)  And press down on the pedal and release.

Pressing down and releasing on the pedal will cause frame flex, and lots of other things can come into play, like you already mentioned as an example, the seat post can click on the frame seat tube.  I find it easier to figure out where a click is when I am off of the bike standing next to it.

One time I found my rear rack bolt at the dropout on one side was tight, but not tight enough.  As I pressed and released pressure on the pedal, the frame flex caused the rack to move slightly against the rack bolt, causing a click at the rack bolt at the dropout.

If this press and release on the pedal does not replicate the noise, try the same thing but stand on the other side of bike and hold the front brake, pressing on the other pedal.

The next thing I would try is the saddle, as you shift your weight you will shift pressure on your saddle.

Is there any play in your headset or stem, when you pedal hard if you are pulling and pushing with your hands on the handlebar, you could be causing flex there.

If it is a square taper crank, when you changed bottom brackets, if there as a loose crank or a loose bottom bracket bushing, you should have discovered it already.  And when you changed pedals, if it was a pedal you should have discovered it then to. 

Good luck, once it took me over 1500 km to find the clicking noise, it can be hard to diagnose.

PH

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Re: Thorn eccentric bb alternatives
« Reply #6 on: June 21, 2021, 10:11:46 AM »
The main reason is that my Raven does a double click when I pedal harder.
My sympathies, hope you find the source, I'd be surprised if it was the EBB insert/shell, though I suppose it isn't impossible.  Is there an unmarked section you could adjust to, even if the chain tension wasn't ideal? You might also try a wrap of PTFE tape if you can still fit it in. 
EDIT - It occurs to me there are two interfaces on an insert, the BB itself and the insert to frame, that make isolation doubly hard, is the BB a good fit into the insert?  Went in smoothly and  tightened up OK?
I did a complete pedal strip and service a couple of years ago, only to find out the click was the cleat in the shoe...
« Last Edit: June 21, 2021, 10:49:22 AM by PH »

Andre Jute

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Re: Thorn eccentric bb alternatives
« Reply #7 on: June 21, 2021, 12:19:20 PM »
I take what I call the "Jerry Sweeney Approach" to unidentified and possibly unidentifiable (in a reasonable time-frame) creaks and rattles. Jerry was a dealer in computers and later had a factory next to the Apple factory where among other things he did all their production line rectification. I turned up at his factory one day with a Mac that died an inexplicable death and Jerry, agreeable as always, said to come back in a few hours. When I returned I asked the natural question: What was it? And Jerry shook his head. "We don't know. We reflowed the entire circuit board. After that it worked."

If I can't find the creak or rattle almost instantly, I start at the bottom bracket to crank interface (square tapers!) with a torque wrench in hand and work my way first backwards, because there is more that can creak or is likely to come loose towards the back of the bike, and then forwards, checking every fastening for correct torque against a list I keep handy in the box with each of my torque wrenches. That usually fixes the problem, and stands in well for the annual test and wipe-down I do at the annual Rohloff service.

I'm not all that keen on thread lock because it can get into places where it isn't supposed to be. But, since I'm not as obsessed with weight as I am with silence, I think nothing of working the bike over to replace every nut I can with a full length nyloc nut, replacing bolts as required. And where that isn't possible, here's a tip: replace a full depth nut with two half-depth ones. Torque the first one to spec, then screw the other one hard up against it, and the friction against the thread caused by the mating surfaces will keep both in place.

It's been twelve years and more since I last heard any kind of noise from my bike. I ascribe the freedom from rattles etc to my paranoid habit of checking a new bike over very carefully after a first short ride, regardless of which distinguished bicycle manufactory it comes from or how high the reputation of the dealer is. (My daily bike for the last noiseless dozen years is called "The Rolls-Royce of bicycles" -- and that's in Germany! I checked it over with a jaundiced eye, all the same.)

This process, which is very quick if you're organised, causes you to handle and look at every tube and fitting on the bike from an angle at which you would not normally see them, and discovers broken or maladjusted components too.