MLProbst

I replaced the crankset on my time trial bike and have been adjust the front and rear derailleurs including the "B" limit screw. I think I need to start from scratch as I've gotten everything out of whack. Do I start w/ the front or rear derailleur first? Do I adjust the "B" limit when doing to the rear or does it need to be addressed first of all?

Thanks

JohnDThompson 

Start here:

https://www.parktool.com/blog/repair...eur-adjustment
https://www.parktool.com/blog/repair...eur-adjustment

MLProbst

Thanks John

cyccommute 

While the links JohnDThompson linked to are good, seldom do you need to “start from scratch” for either derailer, much less both. Far too many people start with limit screws when something goes wrong with shifting. Changing a crank might necessitate some adjustment but that is going to be a very minor adjustment and will only have an effect on how far the derailer moves inward or outward but has nothing to do with how the bike shifts through the gears.

A bit more information on what your bike is doing would be helpful but you really don’t need to “start from scratch”. That route is likely to put things even more out of whack than to fix the problem.

cxwrench

If you've messed things up and aren't super experienced starting from scratch is a great idea. OP...which front derailleur?

cyccommute 

Yea. Great idea if you want to really make a mess of things…especially if MLProbst isn’t “super experienced”. And how far towards “starting from scratch” do you suggest on going? Remove the derailer and back out all the limit screws then reinstall?

Honestly, even on a new install, there is very little to do in terms of adjusting the limit screws.

What does that have to do with the price of rice in China?

cxwrench

Ok, I've just learned a little bit more about your 'experience' level. The type of derailleur may have a LOT to do w/ how it is set up and adjusted...or do you not know about Shimano's current front derailleurs?

cyccommute 

I just love how everyone questions my “experience”. Please point to a derailer that isn’t set up like just about every other derailer that is radically different from the last 50+ years. Even electronic ones have limit screws. Looking at the current Shimano derailers and the dealer’s manual, they aren’t fundamentally different from those other antiques nor do are they set up any differently. The limit screws still do what limit screws have done since the invention of derailers…they limit travel. They don’t do anything else.

cxwrench

Current Shimano 'toggle link' derailleurs are not like any other derailleur EVER. Go read the manual and tell me it's the same as every other derailleur out there. Even the SRAM YAW derailleurs are different. I guess you don't see those very often, yeah?

MLProbst

I have moved the front derailleur from its original position on the frame and I replaced the cable. At any rate, I seem to get nowhere. I can get the rear derailleur adjusted, but I've not had any luck getting the front derailleur adjusted correctly. I can get it to shift, but never seem to get it adjusted to where I don't have serious chain rub in either the small or the big ring.

cxwrench

Once again...what derailleur do you have? I can't help you if you don't help me.

cyccommute 

“Toggle links” are not like any derailer EVER?! Really? Have you read the manual? They have some refinements but that use the same steps (with some additional ones) but it’s not like they are nothing like any other derailer. Same with SRAM YAW.

No, I don’t see those very often but I’m reasonably certain that I could install and adjust one without much more very few problems. It’s not like either one lacks limit screws or cables or attaches in any significantly different way. Honestly electronic ones have more differences and they still rely on the same kind of technology as a 70s Simplex derailer.

cyccommute 

It sounds like you changed the size of the chainrings. Assuming that you have the proper height on the front derailer, you need to check the angle of the derailer (look at the links from Park above). The outer plate should be aligned so that it is parallel with the chain ring. If you have changed the position of the derailer that is far more likely to be the issue than limit screws.

Once you check the alignment (and adjusted if needed), check the cable tension. In the smallest chainring, the cable should be taut. Shift to the largest chainring and see if the front derailer moves outward if you put pressure on the shifter. If it does, you need to increase the cable tension slightly.

If you have been adjusting the limit screws, you may need to set them again. Follow what the Park Tool links say for setting those if you need to. But, generally, once those have been adjusted, they don’t usually need further adjustment.

cxwrench

Sounds like you've never seen one. There are 2 major differences that you'd know if you ever had...wanna tell me what they are? Yes, this is a test. It's very easy for anyone that's worked on one of them. 'Very few problems'? A single one is enough to keep it from working properly. And no...the Di2 derailleurs are more similar to 'normal' derailleurs then the toggle link are. Go ahead, tell me what you think the 2 big differences are. They're pretty obvious.

cyccommute 

What? You mean the little bolt that puts pressure on the braze-on to stabilize the body and the bolt to adjust cable tension? Those are 2 fairly minor differences and really don’t impact much. The added bolt to put pressure on the braze-on is an interesting and welcome addition to that kind of derailer which were pretty awful. The cable tension adjustment could be adjusted elsewhere by in-line or frame tension adjusters.

Neither of those are “big differences”. Minor…and welcome…refinements but not something that fundamentally changes how a derailer is set up.

I’ve already said I haven’t worked on one. But I have read the manual and looked at videos on how to install one. They aren’t all that different from any other front derailer. And certainly not something that makes it so that I need to know what kind of derailer is on the bike to offer advice on how to make adjustments based on what information has been provided.

And, finally, just because I don’t see a lot of newer bikes doesn’t mean I have no experience. I’ve worked on thousands of bikes. There is very little that I haven’t seen or fixed. It’s all pretty much the same and approached in the same manner.

cxwrench

Except that with the new derailleurs ALL adjustments are made w/ the rear derailleur on the large cog. And that the high limit adjustment is made by checking chain clearance with the INNER cage plate and chain on the large cog, not the 'same as always' chain clearance to the outer place while in the small cog. You may have worked on 'thousands of bikes' but I see so many newer bikes that are set up incorrectly and I can only guess there are a couple of reasons for this. Either a new, inexperienced mechanic OR an experienced mechanic that doesn't see the need to RTFM because 'they all work the same, right'? The new Shimano and SRAM derailleurs are different. That's a fact. If someone needs help adjusting one you can't just give them the same methods you've been using forever.

3alarmer 

.
...*sigh*

cxwrench

What?

prj71

Not true.

cxwrench

Ok, which one isn't?

70sSanO

I think it might be best if the OP let us know what FD he is trying to setup.

This thread is like the quartet on the Titanic...

"Let's play Nearer my God."

"How about When the Saints go Marching in?"

"Can't we just play Auld Lang Syne? We probably won't get to do it on New Year's."

"We've never done In the Garden of Eden by I Ron Butterfly. That will probably take us to the end."

John

cxwrench

I've asked twice what derailleur the OP has...obviously no reply yet. Knowing which model he has definitely makes a difference in how it's set up despite what some 'experienced' posters would have us think.

3alarmer 

...it's actually worse than you've let on. A couple of weeks ago I had to sort out some godawful hybrid bike for someone, that came equipped with a very low end Shimano indexing system. Probably a Mart bike originally, it had been given to my friend, who fiddled around with it and replaced the front derailleur cable.

This particular front derailleur had a cage that was stepped, so it was wider at the bottom portion, narrower at the top.

I suppose it was designed with the idea that it needed to be narrower at the top for the shifting push, then wider at the bottom, to accommodate a wider chain angle variation.

Anyway, somewhere along the line a previous owner (or possibly my friend), had dropped the front derailleur position too low. With the cheap, low end. front indexing shifter, you couldn't really trim the thing to avoid chain interference with the cage. It took me a couple of minutes of head scratching to figure out what was going on, and I had the damn thing in front of me. Mart bikes are like that. I momentarily flashed back to my Saturdays working at the bike co-op. PTSD, I think.

But don't let me get in the way of another pointless exchange with you know who. I, for one, am enjoying it.

cyccommute 

Not ignoring again?

cyccommute 

I thought I was the one who was stupid. Did you not read the manual? According the DM-FD000-050 manual for front derailers from FD9000 to FD4700, this is the instruction for adjusting high limit.



See the part of the picture over on the far right side? Notice that it is set in the outer chainring and outer cassette cog?

Who needs to “read the manual”? Obviously you haven’t. It’s right there on page 16 of the manual. Under the heading “Top adjustment”. And, as I said before, with some slight differences, it’s the same procedure. They aren’t that much different from older derailers nor would they be any more difficult to install nor adjust. The minor differences wouldn’t make it necessarily to know exactly which derailer someone has to suggest a solution to a problem.

By the way, did I get the answer you were looking for? Did I pass your test?