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What exactly does the H screw do on recent Shimano front derailleurs?

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What exactly does the H screw do on recent Shimano front derailleurs?

Old 08-07-22, 07:33 AM
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What exactly does the H screw do on recent Shimano front derailleurs?

FD-R8000, but I think the 105 and Dura Ace versions are the same.
It's not just a limit screw like in the old days.
The L screw appears to be a normal limit screw.
I really hate the "tension adjustment mechanism" since it tends to mangle up the cable much worse than just a normal clamp.
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Old 08-07-22, 08:20 AM
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We dislike this design too for a few reasons. One is that the limit screws are turned in the opposite direction than any other "modern" der. But the do just the same in limiting the cage travel.

Our joke is that after SRAM's inability to make a nice working ft der (and pushed the whole 1x thing) Shimano felt left out and decided to catch up and make a ft der that was way more complicated than needed so their riders and service people would also want a Shimano 1x system (after trying to adjust the ft der) I will say that once set up and adjusted well these ders do shift nicely, just that getting there takes more time and sometimes a cable replacement. Andy
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Old 08-07-22, 09:21 AM
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Originally Posted by beanbag View Post
FD-R8000, but I think the 105 and Dura Ace versions are the same.
It's not just a limit screw like in the old days.
The L screw appears to be a normal limit screw.
I really hate the "tension adjustment mechanism" since it tends to mangle up the cable much worse than just a normal clamp.
My first suggestion is RTFM. That explains everything. It's a limit screw just like the low limit, it's just adjusted differently. I work on these new toggle link derailleurs all the time and they're just slightly more involved than a normal derailleur and slightly more time consuming. The payoff is they work very very well. Here's the Dealers Manual, pay attention starting at page 1.

Shimano front derailleur manual
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Old 08-07-22, 11:23 AM
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I've always adjusted it as a high limit screw. Seemed to work for me. But I also read the manual for the model of Shimano front DR I was putting on. Maybe not carefully, but I did glance at it.

Most everything you need to know about installing and adjusting Shimano can be found here:

https://si.shimano.com/#/

And this place makes articles and videos that sometimes help gel the stuff gleaned from Shimano in your head:

https://www.parktool.com/en-us/blog/repair-help
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Old 08-07-22, 11:59 AM
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Originally Posted by beanbag View Post
FD-R8000, but I think the 105 and Dura Ace versions are the same.
It's not just a limit screw like in the old days.
The L screw appears to be a normal limit screw.
I really hate the "tension adjustment mechanism" since it tends to mangle up the cable much worse than just a normal clamp.
Can't add too much to the advice and link to the dealer's manual shown above - here are a couple other links that I've found helpful :
Modern Shimano Front Derailleur Adjustment Guide - Cycling Obsession (cycling-obsession.com)
installing shimano ultegra fd-r8000 34.9 front derailleur video - Google Search

The fella in the second link is pretty good although he could be a little hard to understand - but I thought he covered the newer Shimano front mech pretty well .

Last edited by blinky; 08-08-22 at 11:12 AM.
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Old 08-07-22, 02:43 PM
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Originally Posted by cxwrench View Post
My first suggestion is RTFM. That explains everything. It's a limit screw just like the low limit, it's just adjusted differently.
A screw that makes changes at both the high and high trim positions is not functioning as a limit screw.
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Old 08-07-22, 03:09 PM
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Originally Posted by beanbag View Post
A screw that makes changes at both the high and high trim positions is not functioning as a limit screw.
If you indeed bothered to read the manual and adjusted that derailleur correctly according to Shimano instructions you'd understand how wrong you are.
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Old 08-09-22, 05:41 PM
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Update: I asked on "a different forum" instead and got some useful answers..
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Old 08-09-22, 06:36 PM
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Care to share here? Andy
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Old 08-09-22, 06:38 PM
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Did you ever bother to read Shimano's manual?
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Old 08-10-22, 02:10 AM
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Originally Posted by Andrew R Stewart View Post
Care to share here? Andy
Hmm, this site blocks all references to that other site.
Google search for "Figured out the Shimano linkage derailleur design" and find the post on the site who's name starts with "red".
There's a nice description and a color-coded diagram showing all the linkages, etc.
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Old 08-10-22, 08:38 AM
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(86) Figured out the Shimano linkage derailleur design : BikeMechanics (******.com)

If this is the correct linked to page they reference the Shimano manual. As cxwrench already mentioned. Andy (****** is "r.e.d.d.i.t")
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Old 08-10-22, 11:21 AM
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yes, the poster took a picture from the manual, color-coded it himself, and then explained the linkages
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Old 08-10-22, 11:31 AM
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So people here provided the help you needed, but you wanted someone to read and explain the manual for you. Okay.
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