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bikerbobbbb 08-07-17 05:07 PM

Rear dérailleur spacer -- Is it safe? / Is there a better solution?
I think my bike used to use the smallest/highest cog in the rear dérailleur. (Note on that below.) Maybe it worked when the bike was new. A couple times when I was at my local bike shop years ago the mechanic told me he just couldn't get it to go it, that it wouldn't go that far, blah, blah, blah. I remember thinking that it used to go that far, so what changed now?

A weekend or two ago, I messed with it. I adjusted the big screw on top (for overall spacing between jumps I think), and the low and high limiter screws. At one point I did get it to jump down to the smallest cog, but the upper cogs couldn't be reached so I adjusted it again and never got back to that. I think that was something with the big screw and the small cog adjuster screw, but I couldn't get it to do that again no matter what combination I tried.

The derailleur could hit that smallest cog if I moved it over by hand. With the hand shifter I wouldn't move over. I tried lots of combinations but it just wouldn't go over any further. I squirted it with WD-40 to loosen anything up. It didn't seem to have a lot of gunk on that piece of it. It seemed like the spring inside it mechanically could not move it any more even though the pieces could be moved over by hand.

And it only need to move about a millimeter. Just pushing it with a finger worked.

Later I got an idea. The bike wheel doesn't move, right? And the dérailleur is attached to the frame. It's the wheel, the cassette, and then the frame with the dérailleur, right? And the wheel with the cassette slot into the frame/dérailleur.

When I built my rear wheels I went from a 35mm hub to 30mm hub (I think). But there's some leeway in the space there apparently. If the dérailleur can't jump over a couple mm's why not move the dérailleur itself over?

So that's what I tried today and it seems to have worked. I'm wondering if this is safe (I'm thinking "good enough") and if there's a better way. What I did was take two washers and stick them between the hub and the frame. That pushes the derailleur out a couple millimeters. And that seems to have worked -- I can shift to the lowest cog now. It's not perfect, but I could mess with the shifting settings later. I can use the hand shifter and get down to that smallest cog.

On the plus side, I think in the past I was riding and looked down. I saw one cog still available, but the second-to-last cog's teeth were butted against the third cog, so I think I was actually on the third smallest cog. When I looked down I only saw the smallest. So today when I added the two washer spacers I got down to the smallest cog. From riding it, it felt like I was actually jumping down *two* more cogs, not one. That's a definitely plus. Besides just having it as an option, there are a few places here where it is a plus. I couldn't pedal any faster before. Now I've got gear options that push my thighs.

So my questions...

Is it safe enough? By adding spaces on the hub, instead of a 1/2 inch of the hub 'stem' going into the frame, I only have about a 1/4 inch. It seemed like two washers was best. I started with that, but I wouldn't want less.

Does it affect braking? The brakes worked normally. After I made my new rear wheel I set the brakes within a mm or so of the rims. No change there with these washers in place. Apparently I'm fine for brakes (which I'll need if I can move a little faster).

I imagine it will wear the chain a little more? If I'm over one (or two) more cogs, that's the rightmost, smallest cog going to the leftmost, smallest chainring up front. It's the most angle for the chain. The local bike shop guy always mentioned I was bringing it in like that and that it would wear the chain, but I figured the chain wears. I'll replace the chain. What's the problem? I should have asked him. The problem is the teeth on the chain ring and cassette wear down too. But those can be replaced. I bought the bike to ride, not to last forever. I want all the gears to work.

Instead of adding washers, could I replace the entire rear derailleur and that would fix this issue? I really do want those lowest cogs on the cassette. When it's a smooth, long slope, I really do want to have that extra option of power available. My thighs will have to build up some now but... they can do that.

I'm pretty sure it's actually two extra cogs I'm getting, not just the one. Thinking it was one more cog was the viewpoint from riding and looking down.

I can post pics, but I would imagine you can get the idea. My main reason for posting here is because there's a little less of the hub sticking into the bike frame now. The skewer's on tight. I did wonder about the heads on the skewer, but if they would crack off, they would crack off whether this was 1/4" one way or the other. If the wheel did actually come loose, it's still in the bike frame slot or the wheel would still stay in some upright position. It would probably jam the wheel in place and wear the tire, but I doubt I would suddenly fall over.

79pmooney 08-07-17 05:23 PM

That's a trick that has been done for decades. Look to make sure the "B" screw engages the landing on the dropout properly. (The "B" screw is the screw that pulls the derailleur back and tightens the chain. You will see it below the axle looking at the derailleur from the rear. It should be solidly hitting a small protrusion or indent on the dropout.)


squirtdad 08-07-17 05:24 PM

Repair Help Articles | Park Tool read and research first while tools are locked away.

over all lots wrong here....can't get into it all

If it worked you before should be able to get it work without spacers.

there is no adjustment of the derailler for spacing between gears (jumps as you call it) that is all controlled by the shifter..... If you don't know what something does....don't monkey with it is good rule that I was taught, find out what it does, then monkey

when you talk about small ring on cassette and small ring on on crank, it is called cross chaining and often will not shift well. there is also no need to do it, as you can get an equal gear with a different combo. If you need higher gearing shift to a bigger ring on the crank first (you also should not use the big/big combo)

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