Question About Rear Derailleur Adjustment Screws

Crevice

Active Member
I recently did an adjustment on my rear derailleur. The bike runs super smooth now, it's super quiet, it shifts great, everything's fine but the screw is so high above the rear derailleur it just has me a little concerned. It was like that when I got the bike after it was professionally built by a local bike shop with a good reputation. I'm just wondering if that screw being so high is unusual. Do any of you guys have a screw this high like that or is this something that is sign that something's out of whack?

I'm also unsure how long these screws are. If it needs further adjustment in the future, will it fall out or just not be able to do it?

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iluvmybike

Über Member
Those two top screws are just for the rd limit settings (should be marked 'H' and 'L' ) and once set should not need adjusting at all unless you fit a different wheel. These settings stop the rd cage from moving too far out (rd would throw chain off and possibly jam in frame) or too far in (rd would hit spokes). They are not used for adjusting the smoothness of gear changing - that is down to cable tension set by using the barrel adjuster. Set the H limit first by shifting to smallest cog and then using the H screw and looking at the rd cage it should be a nice straight line - if you screw the screw in and out you should see the rd cage move. Then shift to biggest cog and set L screw again to be in a nice straight line. You can thern adjust the cable tension to adjust the gears so they move nicely up and down. This video should help:


View: https://www.youtube.com/watch?v=92Cu_jneQFw
 

Ming the Merciless

There is no mercy
Location
Inside my skull
With the chain on the smallest cog at back. Try pulling the derailleur out towards you. With chain on biggest cog at back. Try pushing derailleur into wheel. If in either case moves any significant distance then the limit screws you are referring to, aren’t set right. To adjust just turn the limit screw till you see the derailleur move slightly. Then back off a little.
 

Dogtrousers

Kilometre nibbler
Because of the wonders of indexed shifting it's possible to get the indexing right - the shifter will not try to push/pull the mech out of bounds - and yet not have the limit screws set right. This means that under the right (wrong) circumstances, a bumpy road for example, the chain could go off the end of the cassette because the limit screws are not policing the movement of the mech. So you could get the mech in the spokes or the chain jammed behind the cassette.

So if you have backed off the limit screws at all then you may have opened up a potential problem - best do what @Ming the Merciless suggests move into top (or bottom) gear turn the appropriate hi or lo screw til you meet resistance and the mech twitches a bit, then back it off.
 
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OP
OP
Crevice

Crevice

Active Member
This is the tutorial by Park Tool I followed to the letter. It has almost 8 million views. I feel confident that I did the adjustments correctly but as I mentioned the H screw was high like this when I first received the bike. The minor adjustments here and there I made by closely watching this tutorial made a big difference.

The H screw just seems high. I guess I'm at the "if it's not broke, don't fix it" stage but I was wondering if any of you have a high screw like this as well?

 
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Svendo

Guru
Location
Walsden
To answer your question directly: the screw is fine, unless you change wheels (or possibly cassette brand) leave it alone. If you make such a change it’ll only need a small adjustment. The basic positions of the 2 screws are determined by the side to side position of the thread the derailleur screws into in relation to the drop out and therefore the wheel and cassette. This can vary a surprising amount across different frames hence the need for the screws. I think all my bikes have been similar, and at the front derailleur too.
 
You probably know this, but Shimano use JIS screws and ideally you should be using a JIS screwdriver, not Philips or Posidriv. This is more important with screws that need to be tight, like the ones on SPD pedal bindings, but be careful with derailleur B-tension screws.
 

Willam

Senior Member
You probably know this, but Shimano use JIS screws and ideally you should be using a JIS screwdriver, not Philips or Posidriv. This is more important with screws that need to be tight, like the ones on SPD pedal bindings, but be careful with derailleur B-tension screws.
It’s SRAM not Shimano.
 

Willam

Senior Member
Going from your op you seem to be thinking those screws have anything to do with how smooth the gears are, they don’t, all the High screw does is stop the mech going into your spokes, you can try pushing the mech into the spokes with your hand, if it doesn’t go into your spokes then you should be fine.
 
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Alex321

Über Member
Location
South Wales
You probably know this, but Shimano use JIS screws and ideally you should be using a JIS screwdriver, not Philips or Posidriv. This is more important with screws that need to be tight, like the ones on SPD pedal bindings, but be careful with derailleur B-tension screws.
First, it is SRAM he has, but second, modern Shimano (like most others) use screws with hex socket heads - you need a 2mm hex key for them, not any sort of screwdriver.
 

C R

Guru
Location
Worcester
First, it is SRAM he has, but second, modern Shimano (like most others) use screws with hex socket heads - you need a 2mm hex key for them, not any sort of screwdriver.
I think the shimano limit screws are still jis, at least they are in my less than two years old sora dérailleurs.
 

Alex321

Über Member
Location
South Wales
I think the shimano limit screws are still jis, at least they are in my less than two years old sora dérailleurs.
They are hex keys in my 105 R7000, both as originally fitted on the bike bought last August, and on the replacement I had to get after bending it.

Just looked up some manuals. It seems to vary, depending on range.
For 105 (R7000), ultegra R8000, Dura-Ace R9100, it is 2mm hex keys.
https://si.shimano.com/pdfs/dm/DM-RARD001-04-ENG.pdf


For Claris RD2000 it is cross head screwdriver
https://si.shimano.com/pdfs/dm/DM-RBRD001-00-ENG.pdf

For Sora R3000 it is cross head
https://si.shimano.com/api/publish/storage/pdf/en/dm/GN0001/DM-GN0001-24-ENG.pdf

For older versions RD-9000 RD-6800 RD-5800 RD-4700 it was cross head screwdrivers
 
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Ajax Bay

Guru
Location
East Devon
modern Shimano (like most others) use screws with hex socket heads -
Maybe (depends how you define modern (?expensive, hi-end)). Most derailleurs (including the overwhelming majority on bikes made this decade) use limit screws which can be adjusted with a cross or flat blade screwdriver. I suggest that an RD/FD with fancy hex socket screws is a totally unnecessary change merely made by manufacturers for the sake of it, with no beneficial effect.
 
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