Thorn Cycles Forum
Technical => General Technical => Topic started by: in4 on July 24, 2023, 12:55:55 PM
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Just adjusted my EBB as per Thorn instructions. It was quite stiff to move, doesn’t surprise me when considering the conditions I cycled in on my recent Scottish tour. My question is: Should I lubricate/grease the EBB and if so, is there an access hole/ point I should use? TIA
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I always lubricated the shells of my Thorn Nomad Mk2 and Mk3 EBBs when I was building the bike or replacing the BB, i.e. when the cranks were not attached. It was easy then to slide the shell out and rub grease on it. But when your cranks are attached, there is no real way to get grease around the shell.
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Should I lubricate/grease the EBB
Yes. Without periodic lubrication, they can seize in place making future adjustments difficult or impossible until freed with some effort. Remember, the frame's BB shell is steel, while the eccentric insert is anodized aluminum. Galvanic corrosion can form between these two dissimilar metals over time without some sort of grease a an isolator. I believe Thorn has recommended using CopperSlip. I have had good luck using Phil Waterproof grease.
if so, is there an access hole/ point I should use?
Like WT, I remove one crankarm (the off-side/left side) and then loosen the grub screws and slide the eccentric and BB with right arm attached, pulling the unit out the right side. I then clean and grease the interior of the frame shell and the exterior of the eccentric and then reinsert and reattach the left crankarm. It is a pretty quick operation and keeps adjustments smooth (or restores easy adjustability if it is sticky to start with).
As for lateral (left/right) adjustments of the eccentric, I've found my Nomad one is perfectly centered when it is midway in the frame's BB shell. I just use my fingers as a crude caliper to check my eyes and...done. If yours is purposely offset for some reason (i.e. to achieve the needed chainline with the crankset you're using), be sure to note and measure any offset before removing the eccentric so you can restore it After.
Best, Dan.
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I'll second Phil waterproof grease.
One of my many squeaks disappeared after applying the grease. Don't need much at all. Now it's a regular part of my PPM.
Unlike Dan, I'm unable to remove a crank arm.
( What should I buy?). I undo the 2 bolts holding the EBB and slide it to the left, grease and then slide to the right. Appears to work.
Best
Matt
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Unlike Dan, I'm unable to remove a crank arm.
( What should I buy?).
A standard crankarm puller for 3-piece cranks should cover the bulk of current cranksets intended to work with internal bottom brackets. Something like this...
https://www.sjscycles.co.uk/tools/cyclo-14mm-cotterless-crank-puller/?geoc=US
Of course, you'll need a socket wrench to remove and replace the crankarm bolt as well; you get that by flipping the above tool over to the socket end. Yours may not even require that, as many more recent cranksets of this sort are supplied with a center bolt that incorporates a duct cap and is tightened/loosened using an 8mm allen head wrench.
If your crankset is a 2-piece design with external/outboard bottom bracket, then you can remove the left crankarm by loosening allen-head machine screws and flipping the safety catch up before sliding the left arm leftward, off the spindle.
I undo the 2 bolts holding the EBB and slide it to the left, grease and then slide to the right. Appears to work.
If you can get enough grease in there to do good, then you should be fine. Thorn's eccentrics are sort of hollowed out in the middle, leaving only a ring on each side and part of the middle to deal with. Other designs (like the one on my tandem) are solid with no reliefs.
Best, Dan.
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Thanks Dan. It's on my Xmas list.
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I have never lubricated my bottom bracket eccentric. It is anodized aluminum, the shell (Nomad Mk II) is painted (or is it powder coated?) steel, so the paint isolates the steel from the aluminum eccentric. Thus, no dissimilar metal corrosion.
I was not aware that some of the eccentric shells were bare steel inside. I suppose that the Mk III Nomad would probably need a tighter fitting shell than the Mk II because of the bolts that hold the shell tight around the eccentric.
Someone on this forum years ago said that he removed one eccentric bolt when he adjusts it on a Mk II Nomad so that he could see where the depressions were from the pointy end on that bolt that presses into the eccentric, so that when he adjusted it he could make sure that the depressions (I call them divots) are far enough apart to prevent the eccentric from forming a groove. That sounded like a brilliant idea to me, that is what I do. And that also means that my chain has to get quite loose before I adjust it because I want the divots to be at least a couple mm apart on my eccentric.
I have now adjusted my chain enough times with replacement chains that I almost never create a new divot, reuse old ones.
I bought a XLC brand crank puller for my Nomad Mk II square taper cranks. It uses the 15mm open end wrench that is the on eccentric wrench that comes with the Nomad Mk II frame. And there also is an 8mm socket on the part of that puller that you turn. I have to remove both crank arms to pack my frame into the S&S case, thus the wrench goes with me on a tour. I want to minimize the size and number of tools I need when I travel with that bike. I also cut a straight stub of 8mm allen wrench that fits into the 8mm socket hex hole in the eccentric wrench, so I can use that on both the crank arm bolts and XLC crank puller.
https://www.xlc-parts.com/gb-en/xlc-crank-puller-to-s07-for-square-bb/
The XLC tool, the eccentric tool and a multi-tool are in the photo. The stub of 8mm allen wrench is attached to the eccentric tool with a rubber band so it does not get lost.
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One useful thread on seized eccentrics can be found here...
http://thorncyclesforum.co.uk/index.php?topic=1738.0
Best, Dan.
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Up till now* my annual service has included removing those items that have a tendency to seize - seatpost, EBB shell, cranks**, pedals - it's a chance to air the frame out, clean and examine the components, spray some ACF-50 inside and apply copperslip before refitting. It isn't a huge task, the entire service, including a hub oil change, will be done in two sessions over a weekend, leaving the frame to air, and the flush oil to drain, overnight.
I do sometimes wonder if I overdo it, but I've never had a roadside repair that I've thought could have been avoided. I can't remember the last time I did any maintenance on the bikes, other than adjusting brakes and lubricating chains, outside of that annual service.
*My riding has reduced, grandkids do that for you, I may start servicing my bikes bi-annually.
** There is an argument that the crank/spindle interface shouldn't be lubricated and are best left undisturbed. I've seen several wrecked by becoming impossible to remove, I don't know of anyone who'd wrecked one by lubrication!
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One useful thread on seized eccentrics can be found here...
http://thorncyclesforum.co.uk/index.php?topic=1738.0
Best, Dan.
Thanks for that trip down memory lane Dan. Interesting the discussion of split shells. I always thought them a superior design, I spec'd it on my custom bike before Thorn adopted it, though Thorn have made a much neater job of it with only partial splits.
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...and a reminder of why it's a good idea!
http://thorncyclesforum.co.uk/index.php?topic=14338.0
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** There is an argument that the crank/spindle interface shouldn't be lubricated and are best left undisturbed. I've seen several wrecked by becoming impossible to remove, I don't know of anyone who'd wrecked one by lubrication!
What was the cause, dissimilar metal corrosion?
I have never had such a problem, maybe I need to start worrying about it.
If my memory is correct, Campy recommends against it. I have Campy square taper cranks on four bikes.
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** There is an argument that the crank/spindle interface shouldn't be lubricated and are best left undisturbed. I've seen several wrecked by becoming impossible to remove, I don't know of anyone who'd wrecked one by lubrication!
What was the cause, dissimilar metal corrosion?
I think probably corrosion of some sort, it doesn't have to be galvanic to cause seizure.
The problem is usually stripping the threads trying to remove, I've done it once, it's difficult to judge how hard to go, tool was fully inserted and I didn't think I was using excessive force... I've considered self extractors a couple of times, but some reports suggest these can be equally troublesome. Thankfully, apart from that once, mine come off reasonably easily if removed when servicing.
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I've had good luck over the years by lightly greasing my square-taper BB spindles and then torquing them to spec ONCE. I don't re-torque nor do I lubricate the underside of the bolt heads. My general approach is summed up nicely here...
https://www.renehersecycles.com/to-grease-or-not-to-grease/#:~:text=They%20advised%3A%20%E2%80%9CGrease%20the%20tapers,press%2Dfit%20between%20the%20parts.
Best, Dan.
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** There is an argument that the crank/spindle interface shouldn't be lubricated and are best left undisturbed. I've seen several wrecked by becoming impossible to remove, I don't know of anyone who'd wrecked one by lubrication!
What was the cause, dissimilar metal corrosion?
I think probably corrosion of some sort, it doesn't have to be galvanic to cause seizure.
The problem is usually stripping the threads trying to remove, I've done it once, it's difficult to judge how hard to go, tool was fully inserted and I didn't think I was using excessive force... I've considered self extractors a couple of times, but some reports suggest these can be equally troublesome. Thankfully, apart from that once, mine come off reasonably easily if removed when servicing.
Since I have to remove my crank arms on my Nomad Mk II to fit it into an S&S case, I installed self extractors. They might have worked better if I used a thread locker like Loctite, but I did not. Somewhere in the middle of Iceland, one of my self extractors self extracted. (See photo.) Thus, when I went to pack up the bike to go home, had no extractor on that side. Had to transfer self extractor from one side to the other to remove the crank arm and did not have the proper tools to do so. That is when I bought the small XLC crank puller I described in a previous post in this thread. That stays in my tool back and won't fall out at an inopportune time. With the stub of an 8mm allen wrench that I cut to fit in the Thorn eccentric tool, that does all I need.
No more self extractors for me. I had crank pullers before that, but they were larger or my Sugino puller used different tools that I could avoid bringing with the XLC one. Since whatever tools I used had to be carried on the tour, I wanted to minimize that as much as possible.
A friend of mine had to cut a crankarm off of a bike. He got the bike used and the crank was on there really tight, so tight that the square end of the spindle was flush with the square hole in the crank arm. I had never seen a crank on a spindle that far. I am not sure why he ended up cutting it off. I loaned him my Sugino puller, he might have worried that he would break my tool if he forced it too much, that would not surprise me?
Crank arm bolts are the only bolts on a bike that I more often then not use a torque wrench when I install them. But, I do not carry a torque wrench on tour, so they often are not torqued properly on my Nomad Mk II. I previously mentioned that most of my cranks are Campy, but my Nomad Mk II uses low budget Vuelta crank arms.
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I've had good luck over the years by lightly greasing my square-taper BB spindles and then torquing them to spec ONCE. I don't re-torque nor do I lubricate the underside of the bolt heads. My general approach is summed up nicely here...
https://www.renehersecycles.com/to-grease-or-not-to-grease/#:~:text=They%20advised%3A%20%E2%80%9CGrease%20the%20tapers,press%2Dfit%20between%20the%20parts.
Best, Dan.
Thanks for posting that link. I might start using grease on square tapers.
I have known people that kept tightening their crank arm bolts. And I have noticed that crank arm bolts seem to be looser after a while. But I have resisted the urge to keep tightening them.
I have assumed that the crank arm was slightly stuck on the spindle and that the bolt was in tension pressing on it. And with repeated pedaling, the arm would slowly slip further into place, reducing tension within the bolt, as the stresses in the components come into equilibrium with each other. I have no clue if that actually happened or not, but when I could not figure out why crank arm bolts felt unusually loose later, I tried to figure out why. And the slipping crankarm on a spindle was the only logical answer I could conjure up.
I was afraid that if my suspicion was correct and the crank arm shifted on the spindle, repeated tightening of the bolt could do more harm than good. That is why I did not keep re-tightening them.
And, if I use grease on the taper, it is more likely to slip into place and stay there when first installed is my thinking.
I will keep using a thread locker on crank arm bolts. I recall a friend telling me that he was out for a bike ride and suddenly he heard someone swearing loudly. This was in the days of toe clips, not cleats on shoes. He looked at the guy swearing and he saw him on his bike, with a toe clip holding a pedal on his shoe, and a crank arm hanging loosely from his foot, no longer attached to the bike. I do not want a crank arm bolt to fall out and get lost. Or that could happen to me.
If I grease the taper, I wonder how much less torque I should use on my Campy cranks? (No, I am not asking you to research it.) I would be inclined to reduce it ... 20 percent.
I took a snapshot of part of a page of the Campy instructions, attached. I have not bothered to de-grease, but otherwise this is what I have been doing. (If you think this is a copyright violation, please delete it.)
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No more self extractors for me.
I tried self extractors a few years ago, as I thought they would be a good idea on tour.
They worked a few times, but finally one got stuck, so I had to remove the self extractor and use a normal extractor tool.
So I stopped using self extractors.
Except on very long tours, I don't bother carrying a crank extractor tool.
I don't think I have ever needed one while on tour since I started using square taper bottom brackets (the old cotter pin bottom brackets were another matter).
And in most places I go to it should be possible to find a bike shop with the necessary tools if I ever do need to remove a crank.
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Continuing the subject of cranks, I wonder if cranks fitted in cold weather might need tightening in hot weather as aluminium expands more than steel? Also, I usually find I need to retighten the cranks after the first ride or two but I'm probably not using enough brute force as I use a big L-shaped Allen key.
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..., I usually find I need to retighten the cranks after the first ride or two but I'm probably not using enough brute force as I use a big L-shaped Allen key.
At home I leave a 8mm allen wrench on my half inch drive torque wrench, as the vast majority of times I used that torque wrench, it was for crank arm bolts. I think the handle is about 15 inches long (~~375mm).
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Ha, I didn't mean to set us off on another path to perfection, I sometimes laugh at myself for overdoing it, though I'm greatful to those who make my obsessions seem reasonable!
I've never put a torque wrench on a crank, I don't have one that goes that high, I put a bit of copperslip on and do it up pretty tight. The objective is for it to stay on till it needs to come off, then do so without drama. So far, so good.
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Ha, I didn't mean to set us off on another path to perfection, I sometimes laugh at myself for overdoing it, though I'm greatful to those who make my obsessions seem reasonable!
I've never put a torque wrench on a crank, I don't have one that goes that high, I put a bit of copperslip on and do it up pretty tight. The objective is for it to stay on till it needs to come off, then do so without drama. So far, so good.
Years ago, soon after I built up a bike with a square taper, probably almost two decades ago, I heard a slight squeak as I pedaled. Stopped, tried to find what was loose. I was miles form home. I only had a tiny little multi-tool but it did have an 8mm allen wrench, figured out that one of my crank bolts needed tightening. I had read of a few cases where people rode too many miles with a loose crank and ruined them, so that scared to into doing a better job on that bolt.
Soon after that in 2006 I bought a 2003 Land Rover Disco 2. That came with a receiver hitch from the factory, but mine was first owned by a rental car company. They do not like people to pull trailers, so they pulled off the hitches and discarded them.
So, I had to buy a pretty expensive replacement hitch to bolt to the frame. And that had torque specifications that I wanted to make sure I did it right, so I bought the big torque wrench to install the hitch. I learned that I did not need that torque wrench because lying on my back on the ground trying to tighten the bolts I learned that I did not have enough muscle to reach the required torque levels. But I did the best I could.
So, that is why I use the torque wrench on those bolts on crank arms. I want to do it right, and for another project I had already bought the wrench, all I had to buy for the bikes was an 8mm allen wrench that fit on a half inch drive torque wrench.
There is only one other thing on a bike I am careful on torque. I have a Ritchey Break Away bike, that has a coupler similar in function to an S&S coupler on the downtube. And the coupler has to be tightened to 4 nm of torque, no more, no less. It uses a 4mm allen wrench. So I bought a much smaller torque wrench for that.
Everything else, I do by feel.