larwyn

Okay I've posted several times that I am no bicycle mechanic, so here's the proof. I have seen lots of good advice given here and hoping that someone can tell me what the problem might be.

My wife was given a Schwinn Suburban by a friend it is a fairly recent hybrid with a 7 speed cassette and 3 speed crank. Black plastic Sram ESP 7 speed derailleur and grip shifters. She threw the chain yesterday, it lodged between the smallest rear cog and the dropout.

I read up on derailleur adjustment, watched a couple of videos last night and walked out to the garage this morning fully confident that I was about to straighten out the shifting problems that that the lady who gave her the bike mentioned.

So I shifted to the smallest cog on the back and the largest cog on the front, removed the cable from the derailleur and adjusted the "H" limit. I loosened until the chain was threatening to jump off and then tightened until silent. I then pulled the slack out of the cable and reattached it to the RD. I then shifted the chain onto the second smallest cog and adjusted cable tension until it shifted back down to the smallest cog, then tightened the cable tension until it shifted back to the second cog and ran quietly. I then adjusted the "L" limit screw until the chain jumped off the largest cog, put it back on and adjusted until it was quiet and stayed on the largest cog. The "B" angle screw adjustment seemed fine with about 1/4" gap between the pulley and the largest cog.

When shifting up or down through the gears it always skips either 4th or 3rd gear and jumps right on up to the next gear. I only get 6 clicks of the shifter between the smallest and largest cog and the shifter seems to be prevented from going into the detent marked "1" through the cable by the "L" limit screw. It seems like the "span" is off but I have found no reference to a way of adjusting this.

I have adjusted the limits and indexing several different times, using several different variations of what is basically the same procedure that I found on the internet.

It seems like either the shifter is pulling too much cable for each detent, or the derailleur's range of movement has somehow become non-linear.

Sorry for the long post but I was hoping that someone out there could see exactly what I was doing wrong if I described the procedure that I went through and the results that I got.

Whether I eyeballed the adjustment or adjusted the cable tension until the chain shifted the results were the same. Skipping 3rd or 4th gear and only indicating 6 gears on the shifter (1st out of the range of cable movement). The bike chain does shift onto the largest cog, but it indicates "2" on the shifter, and when it reads "7" it is accurate as the chain is on the smallest rear cog.

What should I check next?

bikeman715

you need to have the rear derailer 's hanger check , it sound like it bent . To do so take it to your LBS and have them use https://www.parktool.com/product/dera...nt-gauge-dag-2.It only takes 10 mins to do . Your sound like it off just a little ,you make not see it but it will affect your (her ) shifting like you posted.

gyozadude

The references for limits of derailleur movement are indeed the small cog and the big cog. But the reference for proper indexed gear and cable tension are the 2nd to smallest cog and larger. Try to avoid using the smallest cog (Highest gear) as the cable tension reference. The fact that you can twist the adjuster barrel(s) on cable tension to cause the chain to move from 2nd smallest cog to smallest means you've probably got too much adjuster barrel unscrewed.

Try this:
a) shifter to tallest rear gear (i.e. the smallest cog outermost).
b) adjuster barrels almost in all the way, except for 1 or 2 turns backed out
c) set H-limit adjustment
d) tighten the RD cable now with some tension (like using one hand to pull on end of cable)
e) try to shift to 2nd smallest cog, and adjust tension until centered on 2nd smallest cog
f) shift through other gears
g) set the L-limit screw.

That should do it. The key is to shift to 2nd smallest cog with first click on the rear shifter and then center using cable tension on the 2nd gear. We shouldn't use the 1st smallest cog as the cable tension reference because various manufacturers often assume zero or minimal tension and no cable housing compression yet and the RD is resting against the H-limit screw. So they usually increase the amount of cable slack picked up by the shifter on the very first click because they try to accomodate all that cable housing compression, pre-stretch in brake cables, etc. So for indexing to work, the amount of slack picked up by the shifter on subsequent gear shifts is consistent and smaller. Hope that works for you.

Al1943

I agree with having the derailleur hanger alignment checked.
Use the derailleur adjustment instructions found at www.parktool.com. Do each step in detail and in sequence, leaving nothing out.
A 7-speed shifter should click 6 times.

larwyn

Thanks to all for the advice, I knew it had to be something simple, just did not know what to check. After realigning the derailleur hanger it no longer skips gears as the shifter now indicates all 7 positions.

After checking out the Park DAG-2 at Park's site. I figured I could make something that would work well enough, considering that the tolerance is well over 1/8" inch for the final check. After putting the bike back on the rack and removing the derailleur and seeing that nice flat surface I decided to give it a go with a straight edge (actually the 24 inch level which was hanging near by) and a simple ruler. By this method I found the hanger to be twisted and bent in as if the bike had been dropped on the derailleur (big surprise, right?). It was off on both the horizontal and vertical plane by about 1/4 to 5/16 of an inch. I twisted it back in the proper direction with an adjustable wrench, got it within approximately 1/8". Reinstalled the derailleur, readjusted the screws and indexing and all is much better now. I still have a bit of an indexing problem with the second to the largest cog, too much cable tension (rattles a bit in that gear) but if I adjust that out it messes with the 7 to 6 shifting. A more careful measurement of the hanger alignment might fix the problem but it is good enough for the now.!!

Thanks again to all three of you who responded so quickly.

bikeman715

yes you are on the right track , more adjustment of the hanger is all you need at this point . once you do that then the shifting be good to go .

larwyn

Well, I decided I couldn't live with "good enough" so I tackled the rear derailleur on my my lady's Schwinn once again. I had some success using a straight edge, ruler and adjustable wrench to adjust the RD hanger. Today in my effort to improve on the the adjustments that I made previously I came up with the idea to bolt a 1,2,3 block to the RD hanger to use as a reference surface, that way I could clamp a 24 inch level across the wheel and rotate and measure the adjustment that way. I got it adjusted to within 1/16" that way and put everything back together. There was noticeable improvement but there was still a bit of "rattle" on that second to largest cog.

I thought about pulling the RD once more and trying again. But instead I picked up a large screw driver, placed it between the cassette and the RD hanger and pried it out just a bit (actually about as much as I was afraid that I had bent the hanger when I tightened down the bolt holding the RD). Readjusted the stops and tension one more time and now it "snaps" into each gear and runs quietly, all is well...

If I had to do that job very often I would just go ahead and buy the DAG-2. I know how to do the job without it and have proven to myself that I can do it, but I can see how that tool could save a lot of time and frustration and I think it is one special tool that just might be worth it's price. If I had the right parts laying around I would make one myself but in this case I just cannot duplicate the function of the Park tool with what is currently in my scrap bin.

Thanks again for the help......

dedhed

While I've been known to straighten them, that hanger is probably a replacable one for about $15.
https://wheelsmfg.com/content/section/4/27/

larwyn

Thanks but no, this one is just a tapped hole in the steel dropout plate. But shifting is fine now, after the final tweaking with a pry bar/screwdriver, the 6 pound hammer remained "holstered"......

bikeman715

Larwyn , I 'm glad to hear you got the hanger straight and the shifting is now working as it should . Yes having the tool does save time & frustration . I have the earlier version of the tool and can't count how many time it same the day and the hanger .

dedhed

I also ordered up a 3" long M10X1.0 bolt from Fastenal and welded an 8" pipe to it as a straightening tool. Gives more control to your bending and keeps the hole & threads from getting tweaked.

larwyn

I know it's an old thread but it is mine. My DAG-2 just came in mail. I decided that I would not jump through the hoops which I described in this thread in the future. If I still had a metal lathe I would have made it but DAG-2's are much cheaper than lathes.......

What is kind of amazing is that after all this time, my previous adjustments, including the final "blind tweak", seem to have been right on the mark. But it is a world easier to measure with the proper tool.

bikeman715

as they always said the right tool for the right job always get it done right.

reptilezs

almost every RD adjustment guide fails to put hanger alignment as the first step, too bad. most fd guides tell you where to mount it(height and rotation), why not the RD?