adlai

For something so simple, I've had to Google it every time I adjust a derailleur. Is L the low gear? What does low mean here? Low as in low tooth count or low as in lower effort? Is H high gear? High tooth count?

And generally is the L screw on the left or the right? Which screw am I turning? Sometimes the light isn't great so I have to turn the light on my phone and peer in really close at the indentations which are the same black color as the rest of the derailleur.

Crikes.

skidder

I can't remember either. I just figure it out by moving the shifter lever (I don't have brifters) and see what moves, then adjust the proper screw to put the RD over the proper gear on the cassette. Not something to worry about.

smd4

L= low gear. The gear you use to start the bike. The easiest gear. Biggest gear in back, smallest in front.

H=high gear. The gear you use to make the bike go as fast as possible. The hardest gear. Smallest gear in back, largest in front.

LesterOfPuppets

L is the cog/ring closest to the frame
H is the cog/ring furthest from the frame

Works on both derailleurs.

Sorry I don't have a mnemonic device for it.

msu2001la

Left and Right would make a lot more sense to me as well.

On cars, using "low and high" to describe gears makes more sense, because they're numbered from low to high. The smaller the number the lower the gear. No one knows or cares how many teeth the cogs have, and no one can see the physical size of the gears.

There's no such numbering on a bike - and in fact people usually refer to gearing by the number of cogs so an 11t gear is a lower number and physically smaller than a 12t gear, but the 11t is the "bigger" or "taller" gear. People use the phrase "pushing a big gear" all the time to mean using the smallest physical size of gear on the cassette. It breaks my brain...

mpetry912 

"Low" is left

"High" is right

Again applies for both front and rear detailleurs

but a close look at the mechanism should tell you

/markp

frogman

and when you adjust the screws, righty tighty, lefty loosey

nomadmax 

So then derailleurs should be right normal for the rear and the front should be left normal? If you're gonna visit, learn the language and customs.

Barry2 

“L” is for LOUD, the noise made by the chain hitting the spokes
”H” is for the HARM the chain will do to your frame



Barry

Troul 

L = Lazy
H = Hurting

cyccommute 

As others have said, L is low and H is high. Saying “left” or “right” would make no sense as only some of the lower end derailers have screws positioned on the low part of the derailer body. More often, the limit screws are on the back of the derailer and are aligned vertically.

pdlamb

I'd be happy if I could just find the "L" and "H" on half my derailers.

njkayaker

Then, remember L as left and H as the other thing (not left).

Riders shouldn't have an issue with L being low (the largest sprocket).

cyccommute 

Well, there is that too. And Shimano can be a bit loosey goosey about which screw on the front derailer is low and which is high. They switch them often on different models.

freeranger

Had to go out in the garage to see if my derailleurs were marked L or H. If they are, I couldn't see it. Are all derailleurs marked?

spelger

no. not on my old Sora, only the RD was labeled, FD not. upgraded to Tiagra and same deal. on my new ride with ultegra Di2 they aren't labeled either.

Iride01 

Limit screws should only need to be adjusted at time of installation. If you are adjusting them after the install, and there hasn't been any physical damage to the bike and drivetrain, then you are doing something wrong. They aren't for adjusting indexing issues or other common problems with gear shifting.

soyabean

If you don't know which is L or H, it doesn't matter if you peek inside the derailleur (both FD and RD), you can see the screws how they hit a stop for any of the outermost cogs, meaning, leftmost cog on the non-drive side, rightmost cog on the drive side.

Lighting problems are easily solved. Get a brighter lamp. Work outdoors in the daytime.

smd4

Absolutely. "Left" and "Right" would have no meaning on my DA 7700 RD, where the screws are vertical.

Surprised this is an issue with so many people.

LesterOfPuppets

Same with my olde Sora FD. Luckily it's really easy to see the stop on those, with a quick glance I can see that the outside screw works on the outside chainring.

prj71

If you don't which is which (it's not that difficult) then maybe you are candidate for bringing your bike to the bike shop to be worked on.

79pmooney

Or changes in chains. Old story - 1977. I trained on the reliable Sedisport chains but had started racing with the quicker shifting Uniglides. Took me one costly race where i dropped the chain twice before I learned that the limit screws needed to be snugged up 'till the chain rubbed slightly in low and high to guaranty not dropping the chain on a shift.

Granted that was long before indexing, shaped teeth, etc. Still, the blanket statement that limit screws should never be touched after installation - well maybe for modern index systems but with friction shifted systems, both limit screws affect how quickly and easily you can get to the extreme cogs. Especially before ramped teeth. Low gear may be taking the RD cage quite close to the spokes. I've had more than a few bikes where I've juggled the ease of shifting with the sound of the idler pulley nut brushing the spokes. (Yes, I've mixed and matched Italian hubs and Japanese FWs where the low cog can get quite close to the hub. And yes, the hangers were straight.)

Maelochs

"Left" and "right"/ Wait left and right on the bike? From the front or the back? On my 105 the screws are vertical .... so which way do I lay the bike down?

I have seen that in the back "L" is almost always closest to the derailleur body and "H" farther away in the back. I sometimes forget ... so I pop off the headlight and check before I do harm. But .... "L" is always closer the hub, even if vertical .... and "H" is always farther ... which is sort of the way the derailleur swings. Still ... I check periodically. No desire to put the derailleur into the spokes.

Up front I have never seen "H" not be on the outside, which is the way the derailleur swings.

Also ... if you are making small adjustments, you should be able to actually See the effect of your adjustment before you break something. If you are turning one screw and the derailleur's range of motion isn't limited, turn the other screw.

Sorry, but your "left" and "right" seems a lot less universal than ""L" for Low gear (and we all know what low gear is, if we actually ride bikes) and "H" for High gear.

rosefarts

I can’t remember the last time I looked at the letters. Just eyeball whether the screw is physically touching the stop or is pretty close. The rest can be sorted out from there.

cyccommute 

That’s possible on some derailers, especially old ones or cheaper new ones but many derailers don’t really let you see the stops.