Do I really need a Fixing Bolt on my Non-Drive side Ultegra crankarm?
07-15-12, 08:37 PM
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Do I really need a Fixing Bolt on my Non-Drive side Ultegra crankarm?
When I bought my bike used it was missing one and I decided to purchase one on Ebay. I noticed that after a ride last night that it fell off. I am not sure if it's worth buying another one. Do I really need it?
07-15-12, 08:43 PM
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If you don't mind the crank arm falling off at some random moment then feel free to leave the fixing bolt out.
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07-15-12, 08:47 PM
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07-15-12, 08:51 PM
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Which bolt are you referring to then if not the bolts that hold the crank arm in place?
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07-15-12, 08:52 PM
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07-15-12, 08:59 PM
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Gotcha. I don't know what would happen if you left that out, but I wonder if it doesn't help maintain pressure on the bottom bracket, perhaps leading to creaks and wear over time if you leave it out? Might want to post this (with the Shimano tech doc link) in the mechanics forum. Traffic is a little lighter over there, but you tend to get better signal to noise in the quality of posts.
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07-15-12, 09:26 PM
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It seals the spindle of the crank from the elements, dirt, grime, mud, etc... It also puts the crank arm in the right position before the pinch bolts are secured, but you can probably do this properly without that part.
I'm not sure what, if any, other purpose it serves.
I'm not sure what, if any, other purpose it serves.
07-16-12, 07:54 AM
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Once you've got the preload on the bearings right, and you tighten the pinch bolts, you really don't need the bolt on the end.
However, if you ever want to take the crank off, or it works its way loose, you're going to have a hard time getting the preload right on the bearings again.
It's similar to a top cap on a steerer tube in this regard. The top cap adjusts the bearing load, and the stem bolts hold the stem to the steerer.
Here, the end bolt adjusts the bearing load, and once that's done, the bolts on the crankarm hold the crank arm to the spindle.
It's a cheap part; I'd go ahead and get one, and save yourself hassles down the road.
However, if you ever want to take the crank off, or it works its way loose, you're going to have a hard time getting the preload right on the bearings again.
It's similar to a top cap on a steerer tube in this regard. The top cap adjusts the bearing load, and the stem bolts hold the stem to the steerer.
Here, the end bolt adjusts the bearing load, and once that's done, the bolts on the crankarm hold the crank arm to the spindle.
It's a cheap part; I'd go ahead and get one, and save yourself hassles down the road.
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Last edited by merlinextraligh; 07-16-12 at 07:58 AM.
07-16-12, 07:56 AM
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Without the end bolt, any grime is just going to get on the inside of the spindle, where it's not going to do any harm. The end bolt isn't keeping crud from getting on the bb bearings.
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07-16-12, 11:47 AM
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Once you've got the preload on the bearings right, and you tighten the pinch bolts, you really don't need the bolt on the end.
However, if you ever want to take the crank off, or it works its way loose, you're going to have a hard time getting the preload right on the bearings again.
It's similar to a top cap on a steerer tube in this regard. The top cap adjusts the bearing load, and the stem bolts hold the stem to the steerer.
Here, the end bolt adjusts the bearing load, and once that's done, the bolts on the crankarm hold the crank arm to the spindle.
It's a cheap part; I'd go ahead and get one, and save yourself hassles down the road.
However, if you ever want to take the crank off, or it works its way loose, you're going to have a hard time getting the preload right on the bearings again.
It's similar to a top cap on a steerer tube in this regard. The top cap adjusts the bearing load, and the stem bolts hold the stem to the steerer.
Here, the end bolt adjusts the bearing load, and once that's done, the bolts on the crankarm hold the crank arm to the spindle.
It's a cheap part; I'd go ahead and get one, and save yourself hassles down the road.
07-16-12, 12:02 PM
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Too little preload = axial play you can feel in your pedal stroke. It can also affect shift quality because of side load on chain rings when shifting the FD.
Too tight preload = generally bearing drag stealing a couple of watts and premature bearing failure...or reduced bearing life.
If you make the plastic wheel finger tight or torque the preload bolt to mfr. spec, pretty hard to mess up preload. A PDF service manual exists on line for most good cranksets.
07-16-12, 06:19 PM
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If you take out the fixing bolt it'll only be a matter of time before you get a litter of baby bike bolts.
12-22-12, 11:48 AM
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The idea that the fixing bolt keeps crud out of the spindle on road cranks is valid, but Shimano's MTB cranks are open on the drive side so it falls apart there.
I like my cranks long so I use XT M770 180mm arms on my commuter. One thing I don't like about having expensive Hollowtech II cranks on that bike is the ease in which the cranks could be stolen. I consider the fixing bolt a SLIGHT barrier from theft since it is less likely that a thief could remove it without the star-shaped tool.
I like my cranks long so I use XT M770 180mm arms on my commuter. One thing I don't like about having expensive Hollowtech II cranks on that bike is the ease in which the cranks could be stolen. I consider the fixing bolt a SLIGHT barrier from theft since it is less likely that a thief could remove it without the star-shaped tool.
12-22-12, 12:55 PM
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The idea that the fixing bolt keeps crud out of the spindle on road cranks is valid, but Shimano's MTB cranks are open on the drive side so it falls apart there.
I like my cranks long so I use XT M770 180mm arms on my commuter. One thing I don't like about having expensive Hollowtech II cranks on that bike is the ease in which the cranks could be stolen. I consider the fixing bolt a SLIGHT barrier from theft since it is less likely that a thief could remove it without the star-shaped tool.
I like my cranks long so I use XT M770 180mm arms on my commuter. One thing I don't like about having expensive Hollowtech II cranks on that bike is the ease in which the cranks could be stolen. I consider the fixing bolt a SLIGHT barrier from theft since it is less likely that a thief could remove it without the star-shaped tool.
1. prevent dirt ingress as discussed.
2. Apply preload to left crank arm prior to tightening two pinch bolts on left crank arm.
Anybody hell bent on stealing a crank who knows what to look for will have the Shimano plastic wheel that inserts into the end bolt and it can be removed in 3 seconds. Steeling a crank off a bike is also a fool's errant. Much easier to steel the bike and ride it away...much less conspicuous.
There was a video study in New York city lately about stealing bikes locked to light poles in the city. Bikes were stolen all over the city while people watched. Nobody was willing to risk their life for confronting a thief when it was clear they were stealing the bike. Smart people.
12-22-12, 02:04 PM
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Not really. Not for anybody who knows anything about cranks. The Shimano crank bolt is under very little torque...finger tight. It is for two purposes:
1. prevent dirt ingress as discussed.
2. Apply preload to left crank arm prior to tightening two pinch bolts on left crank arm.
1. prevent dirt ingress as discussed.
2. Apply preload to left crank arm prior to tightening two pinch bolts on left crank arm.
Personally, I'd replace it:
https://www.niagaracycle.com/product_...ucts_id=701916
https://www.excelsports.com/main.asp?...or=11&minor=10
https://www.jensonusa.com/!vk2Guv!xRR...rm-Fixing-Bolt
12-22-12, 02:11 PM
#16
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Most of the time this is a plastic part; it plays no role for preload. It's purpose is simply to position the crank so there is no side-to-side movement. The bearings are cartridge, their only load is radial and they spin slowly; they require no preload.
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12-22-12, 02:59 PM
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Aside from using it to position the crank arm, I always assumed that the bolt also served as a bit of a safety net in case the pinch bolts were under tightened.
I had a buddy that noticed that his NDS arm was loose and he was able to catch that before the NDS arm fell off. If the fixing bolt hadn't been there, I'm pretty sure the arm would have fallen off.
Bob
I had a buddy that noticed that his NDS arm was loose and he was able to catch that before the NDS arm fell off. If the fixing bolt hadn't been there, I'm pretty sure the arm would have fallen off.
Bob
12-23-12, 10:45 AM
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Just in case nobody gets your sarcasm here, this is all wrong.
12-23-12, 12:44 PM
#20
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What kind of preload is plastic threading going to give you? Maybe you'll take some slack out of the bearing (if the bearing is particularly worn), but there is no way you can apply enough torque to the part to get a real preload. All you are doing is putting the crank arm in position and putting some compression to the bearing seal.
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"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Last edited by Brian Ratliff; 12-23-12 at 12:48 PM.
12-23-12, 01:31 PM
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Park Tools website calls it preload (or at least they did when I looked it up when I first got a Hollowtech crankset; after that I remembered how to do it.)
12-23-12, 02:08 PM
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OK, I want to know how anybody can get that damn thing out after tightening the pinch bolts.
Once those pinch bolts are tight, I can't get that thing to move.
Once those pinch bolts are tight, I can't get that thing to move.
12-23-12, 03:53 PM
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This is more likely what saved the arm, but it wouldn't have been the fixing bolt.
12-23-12, 05:21 PM
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Originally Posted by SteveV
This is correct. It's odd that it fell out because you tighten it to preload the left crank and then when you tighten the pinch bolts, they typically snug it in place. Usually, you have to loosen the pinch bolts before you can even get it out.