Thorn Cycles Forum
Technical => Transmission => Topic started by: rafiki on August 30, 2018, 01:14:30 pm
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After reversing the chainring and sprocket and fitting a new chain I have noticed that the crank isn't turning at all smoothly in the EBB. Can the EBB be serviced/lubricated or is this going to be due to wear or damage?
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Brian, do you mean the eccentric is difficult to move/adjust for chain tension? If so, the eccentric needs to be lubed so it can more easily turn in the frame's bottom bracket hanger. Grease or anti-seize will prevent future galling between the aluminum eccentric and steel bottom bracket hanger.
If the eccentric has been adjusted a number of times so fresh indents have been made too close together, it can make it difficult to rotate the eccentric for adjustment and once rotated, may not easily hold adjustment. Solution here would be to replace the eccentric in this case. The damage would be visible in the form of a number of closely spaced divots in the edge faces of the eccentric.
If instead you find the cranks are not spinning freely or smoothly on the bottom bracket bearings (in the eccentric), then you would need to replace or service the bottom bracket depending on if it is a cartridge bb or one that can be opened and serviced.
Best
Dan.
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Hi Dan. It's adjustable OK. The cranks are not spinning freely in the BB. Can I tell which type of BB I have without dismantling it?
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After reversing the chainring and sprocket and fitting a new chain I have noticed that the crank isn't turning at all smoothly in the EBB. Can the EBB be serviced/lubricated or is this going to be due to wear or damage?
Poor you, sounds like a whole raft of trouble you've had to deal with! So all you have done is take the cranks off the square taper bottom bracket using a crank tool? If it worked OK before, it is hard to imagine how removing might have damaged anything. I assume the cranks are properly seated on the tapers.
If standard and original our BB is probably a Shimano UN55 or UN72. The problem is that they come various flavours to do with axle length, diameter and how much sticks out left and right. I don't think there is anything visible at the ends so it would have to come out, but maybe a call to SJS is in order?
Did you get that seized seatpost shifted? I picked up that woe on another forum. The CTC folk have been discussing stuck posts and the name of a specialist remover The Seatpost man came up in Chorley Lancashire.
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Two further thoughts: I assume this is with the chain off? If the chain was too tight it could cause this problem. Also a long shot, but undo the eccentric bolts with the chain off and see if it persists -there's an outside chance the BB might be under pressure.
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From my Thorn Sterling invoice: Shimano Deore FC-M532 26/36/48 2 piece design 9 speed 4 Arm Triple Chainset Black 170mm.
It's a Hollowtech II system.
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Two further thoughts: I assume this is with the chain off? If the chain was too tight it could cause this problem. Also a long shot, but undo the eccentric bolts with the chain off and see if it persists -there's an outside chance the BB might be under pressure.
Yes, it's with the chain off. I had the same thought.
You mean the two bolts beneath the bottom bracket? I'll have a look at that.
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From my Thorn Sterling invoice: Shimano Deore FC-M532 26/36/48 2 piece design 9 speed 4 Arm Triple Chainset Black 170mm.
It's a Hollowtech II system.
Ah ok, that explains why the chain ring you mention is apparently repurposed from a derailleur system. I’m only familiar with old fashioned square taper systems. I’m sure someone will advise on hollotech external bottom brackets. These should be easier to replace.
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I watched a couple of videos on Youtube. When I get the right tool I can dismantle it and have a look. Perhaps a clean, lube and refit will be all that is necessary
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Did you get that seized seatpost shifted? I picked up that woe on another forum. The CTC folk have been discussing stuck posts and the name of a specialist remover The Seatpost man came up in Chorley Lancashire.
No luck yet. A friend and I had a go but failed. I have ordered some Plusgas as some say it's a better product than WD40 and I am riding on the gravel roads with no seatpost clamp and live in hope! Yes, I saw that about the Seatpost Man. Interesting but a long way from southern Spain. If I drive to UK I might take the bike with me an pop up there.
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Am I correct in assuming that the bottom bracket cups should be tight into the BB insert? The left one on my system can be rotated left and right with the fingers.
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Brian,
If you have an external bottom bracket, then yes! definitely the cups should be tight in the eccentric. They should be for an inboard/square taper cartridge bb also.
If the bottom bracket is a Shimano one with external/outboard bearings and feels rough or excessively tight while turning, it has likely had it, but I'd sure try tightening the cups first. External units are sensitive to needing square faces and if one cup is loose, it won't turn smoothly.
In my experience, Shimano's external bottom brackets are not been so very long-lasting for me in my heavy, high-mileage use. For this reason, I switched to a Phil Wood unit on my Nomad and have had no problems since.
You may wish to read some of my past posts about both the Shimano and Phil units:
http://thorncyclesforum.co.uk/index.php?topic=7289.msg46639#msg46639
http://thorncyclesforum.co.uk/index.php?topic=12155.msg88741#msg88741
http://thorncyclesforum.co.uk/index.php?topic=4479.msg21711#msg21711
http://thorncyclesforum.co.uk/index.php?topic=11252.msg81756#msg81756
http://thorncyclesforum.co.uk/index.php?topic=7969.msg52145#msg52145
http://thorncyclesforum.co.uk/index.php?topic=6535.msg39691#msg39691
http://thorncyclesforum.co.uk/index.php?topic=6193.msg36847#msg36847
Best,
Dan.
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Thanks Dan. I am not at all technical so I attach a pic of the area of my bike when new. Perhaps from it you can tell me what type of bracket it is. It's definitely a Shimano system.
(http://i192.photobucket.com/albums/z29/rafikiphoto/Thorn%20Sterling/G9_IMG_01926__Full_zpspzsrqgu7.jpg)
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Brian, that is definitely a Shimano external/outboard bearing bottom bracket.
The preload adjustment is that little star-shaped thing in the center of the left crankarm.
If the cups are loose they can become misaligned, leading to excess friction. Excess preload when first installing or adjusting the bottom bracket can also result in stiff turning.
Your bike sure is a pretty color!
Best,
Dan.
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Thanks again. Good to know what I am dealing with. So the bearings are housed in the cups and the cups screw into the BB insert. The crank spindle is supported by the insert. It's the insert that is eccentric and is what is turned to adjust the chain tension. I think I've got it. Correct me please if I am wrong.
I guess my next job is to remove the whole thing, clean and lube, refit and tighten up properly to see if the stiffness has been fixed. If not then a new insert and new cups?
Your bike sure is a pretty color!
Thanks, Dan.
(https://beta-static.photobucket.com/images/z29/rafikiphoto/Thorn%20Sterling/M_240_002711-Edit_zpsvofssnld.jpg?width=1920&height=1080&fit=bounds)
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At present, there's several options I'd try if it were my EBB/OBB (in order of ease/cost):
1) I'd send for the tool to fit the splines on the outside of the cups and tighten them if loose. A torque wrench would be handy here but you can probably get by without.
2) I'd look into replacing the Shimano bearings with the same. They aren't too expensive and you may find they give good enough service for the price. SJS Cycles has them here for only £9.99 including VAT. That's a great bargain, enough to lay in several sets against future wear. You could by a lot of these for what I paid for my Phil unit. I paid about USD$100 but they typically retail for around USD$165. This makes replacement with the Shimano unit from SJS Cycles a real attractive alternative. See:
https://www.sjscycles.co.uk/bottom-brackets/shimano-deore-outboard-bearing-bottom-bracket-english-thread-bb51b/?geoc=US
Replacement should take you only 30 minutes or less with the required tools ready to hand.
3) Kits are available to put upgraded bearings into the original Shimano cups. These are typically better sealed, have more grease and better/more bearings, but is is a fair job to do and requires some specific tools.
4) Replace with a premium aftermarket set of bearings/cups. I chose Phil Wood because the cups are hard and stiff stainless, the sealing is really good, they're packed with Phil waterproof grease and the bearings are very high quality. These are also expensive, but for me far cheaper than replacing multiple sets of the original cups at the normal retail price.
Hopefully helpful.
All the best,
Dan.
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Brian,
Our posts crossed. Yes, you've grasped the basics. The only caution compared to an internal/square taper bottom bracket is in this case, the spindle is permanently attached to the right crankarm. It passes clear through both bearings (and the plastic seal in the middle and any spacers required to set chainline) and is secured with the left crankarm, which clamps onto the fee end of the spindle. A toothed plate serves as a lock. Preload (end pressure on the bearings) is set by turning the little plastic star-shaped nut in the left crankarm while the arm clamp bolts are loose. You then tighten the arm bolts to lock in the adjustment and...done.
This may help:
https://www.youtube.com/watch?v=N6-4JHDTvZg
The part where you need to use caution begins at the 8m45s mark in the video.
Best,
Dan.
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This insert is used in my BB I believe, Dan.
https://www.sjscycles.co.uk/bottom-brackets/eccentric-bottom-bracket-insert-fits-raven-mk2-sport-tour-etc-732mm-for-external-bearing-bottom-bracket-gold/ (https://www.sjscycles.co.uk/bottom-brackets/eccentric-bottom-bracket-insert-fits-raven-mk2-sport-tour-etc-732mm-for-external-bearing-bottom-bracket-gold/)
Does this fit inside that Shimano sleeve or do both cups separate from the sleeve and fit directly into the insert?
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Brian,
That gold-colored insert is your eccentric.
As far as your bottom bracket bearings are concerned, your eccentric is just like the threaded bottom bracket hanger in a conventional frame.
You'd leave the eccentric firmly clamped in your frame while you remove and install your bottom bracket cups.
The Shimano bottom bracket (as shown in the SJS Cycles link I gave above) has a plastic sleeve that fits between the separate left and right cups, inside the eccentric. It provides a measure of weather sealing from any water coming down the seatpost or in any open bottle bosses. To install this bottom bracket, you'd insert one half of the plastic sleeve in one cup and install the cup in your eccentric. Then, you'd do the same with the other. The plastic sleeves are...sleeved so one half slides over the other.
So to answer your question directly, the cups are separate and go in each side of your eccentric insert. The protective weather sleeve goes between the cups at time of installation.
Best,
Dan.
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Very clear. Thanks Dan. I have ordered the Park Tool tool. Once it is here I will work on this. I will also take your advice about getting in a stock of the Shimano bearings.
Very many thanks. In the meantime I will be cycling on my good old Dawes Mean Street XT which I have ridden from new since 1994. It's still going strong and is a very comfortable ride.
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Terrific, Brian and all good wishes and encouragement to you. You'll soon have this sorted! :)
Best,
Dan.
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Well done, guys, and good luck, Brian!
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Thanks, chaps. I am so grateful. I have always been mechanically challenged. Sod's law applies here always, and in spades!