vol

Several little screws on my derailleur had been tightened only halfway through ever since the bike was assembled and bought from LBS. I always thought they were tightened to the farthest possible and it's supposed to be that way, but today I was fastening all screws on the bike and found these screws could be tightened much further till completely screwed in, so I did. Was there a good reason they had been only halfway through or was it a negligence of the bike guy who assembled the bike?

The same with 2 or 3 tiny screws nears the crank above the bottom bracket (I think...). Not sure if they were loose since new or became loosened later.

(Maybe I should ask the general question: should all the screws on all parts of the bike be tightened?)

HillRider

Have you tried riding the bike since you tightened all of the screws on your derailleurs? Some of those screws are "limit" screws that control how far the derailleurs will move to the inside and outside of their travel and they keep the derailleurs from dropping the chain off the biggest and smallest cogs and chainrings. If you tightened them all the way, your bike will probably not shift at all.

Assuming this isn't a joke or a troll, you better look up derailleur limit screws and their proper adjustments right now.

CACycling

No

Continuity

It sounds like you're talking about the High and Low (and B-tension) *adjustment* screws on the dérailleurs - they're not for holding anything on or together, but for adjusting how far they can move (and the clearance of the upper jockey wheel in the case of the RD B-tension screw).

Have you actually *ridden* the bike since these 'improvements'? I think you'll now find that your gears are all out-of-whack...

shoota 

If they are the limit screws, which it sounds like, then the next ride ought to be fun lol

demoncyclist

So, you have been a BF member for almost 3 years and have almost 1400 posts, yet you have no idea what the various pieces of hardware on your bike are for? Please let this be a joke...

ttusomeone

vol

Thanks. I haven't ridden it yet but thank God I asked before I do (going to ride this afternoon).
No this is no joke. I have little time to joke today.
Yes it is possible for someone to be a BF member for several years but still very ignorant about bike mechanics. The number of posting is no necessary implication of bike mechanics knowledge.

Many thanks to HillRider, CACycling, Continuity and Shoota, for preventing me from potential trouble this afternoon.

P.S. what about the screw above the bottom bracket area?

ttusomeone

Are you talking about the screws on the front derailleur? They are also limit screws.

demoncyclist

Both derailleurs have limit screws- 2 each, plus the B-adjustment on the rear derailleur. The limit screws are there to do just what you think- they limit the travel of the derailleurs so that you can't shift the chain too far in either direction. I'm sorry if I was harsh, but if you didn't know what they did, why did you just assume that they were loose and needed to be tightened? If the bike was operating properly, there was absolutely no need to touch any of the fiddly bits. I hope you have some time on your hands to try and get it all sorted so you can actually ride today.

FBinNY 

The only screws on derailleurs that should be tightened all the way are the those holding the pulleys, cage, and bottom assembly together, and the upper mounting bolt. Derailleurs also have 2 adjusting screws, to set the inner and outer limit of travel, and some also have one on top to set the angle it hangs at. These three are adjusting screws and are normally set someplace in the middle of their range, rather than tightened.

Your case is another example of what happens when you try to fix what ain't broke.

vol

Yes, I just tried to shift the gears and the front wouldn't until I re-loosened the screws on the front.

I don't remember the exact original positions of the limit screws, but I've just re-loosened them to around what I think was the original, and the change of gear was working while I tested spinning the wheel.

Yes, domoncyclist, there are two in the front and 3 in the rear. I was afraid those screws would fall and be lost that's why I started fastening them, but then thought I'd better come here just to be sure.

Thanks again everyone.

JohnDThompson 

Are these perhaps the limit screws on the derailluers? If so, they're meant to be that way.

mulveyr 

Regarding the low limit screw on the RD, you really, really need to set it correctly ( and not just to around where you think it was originally ) because even a quarter-turn or so difference can be the difference between shifting into your big cog, and shifting the RD into the spokes. Unless you enjoy trashing wheels, deraillers, and possibly yourself.

shoota 

Pics of these mystery screws would help immensely.

vol

Here are the pictures. The first is the front derailleur viewed from top-down. The 2nd is the rear, viewed from about 45 degree angle from top so all 3 screws are visible. Left = front of bike, right = rear of bike.

FBinNY 

As duscussed, inner and outer limits and the B-screw. (find a tutorial on derailleur adjustment to reset correctly)

vol

Which of the three in the 2nd picture is the "low limit screw"? And how to be sure to set it correctly? (I'm bringing screw driver with me this afternoon just in case)

mulveyr 

On Shimano deraillers it's typically the one that is physically lowest when you're viewing the bike upright. It will generally have a very small 'L' next to it.

For adjustments, follow the steps at https://www.parktool.com/blog/repair-...nts-derailleur .

It shouldn't be a matter of "just in case" - you really need to get them right before you ride the bike. You may be lucky and shift successfully 20 times before you damage the wheel, or it may take just once. The high limit screw is important as well, but generally the worst that happens if that one is too free is that you jam the chain between the cogs and frame, leading to an abrupt and unexpected stop.

bent-not-broken

+1! need to be adjusted properly, not just close enough

vol

Thank you so much! and for the link. If I don't have enough time to have it adjusted perfectly following the instructions before I leave shortly, I guess I'll try to avoid shifting the gears for this ride, as I don't want to make any damage. I will go through all the instructions and tutorials carefully tonight.

I'm so glad I asked the question before the ride. The Mechanics forum is super helpful (and often very timely). Thanks again for everyone's time.

cny-bikeman

I see that your posts have rarely been in the Mechanics section, so understandable you have little experience with working on your bike. However, it should be apparent that one does not just dive into tightening/adjusting any mechanical device without knowing ahead of time the proper procedure, certainly more true for one on which you travel. The only exception would be those persons who can, by observation, logic and some general knowledge of how mechanisms work, figure out what to do.

If you do any further work on the bike I would suggest you refer to the sheldonbrown.com and parktool.com/blog sites for the proper procedure. Better yet, if you have a bike co-op or knowledgable friend that is accessible to you get some in-person assistance.

sreten

Hi,

Its fairly obvious which screws / bolts / nuts should be tight
(retaining) and those that should be set (freeplay) and the
rarer limit stop type if you use some sensible observation.

e.g. the pivot bolts on common MTB brake levers :



If you just tighten them, they will stop the brakes working.
(Obviously you do set the clamp bolts tight as is sensible.)
Ideally they are set to minimise lever wiggle but its not critical.
On one side of my bike I kept finding the bottom nut missing.
Fixed that with some nylon insert self locking nuts both sides.

Just apply some commonsense to what you are adjusting.

rgds, sreten.

escarpment

I find it hard to believe that you had no idea how a derailleur works after 1400 posts.

rdtindsm

You WILL forget and shift into your spokes. From the voice of experience. Tore the dropout apart long before replaceable dropouts. 20 years ago, so I don't remember if I also trashed the der. I'm cheap, so I think I might have remembered the expense which would have paled compared to repairing the frame which I most definitely remember.

+infinity to advice to make sure it is right before you ride.