70sSanO

My wife’s bike is like that in the small-small. There have been no issues, and she will use that combination at times.

If you lower the FD and want a tad more width on your FD, you can add a small thin washer at the back of the cage where the screw holds the inner and outer plates together. Unscrew the bolt, add the washer, put it back together.

I would stop short of recommending actually widening the cage where the slightly rubs. Not that I haven’t done it, but it may, or may not, impact shift quality.

John

Harold74

Thanks for your help Dfrost. Do you still feel that way about the derailleur setup after reviewing the photo below, taken head on at the FD on the big ring? I've been working from the following premises:

1) Somewhere, I read that the FD should be at least 3mm clear of the chainring. I fear having it too close for risk of it catching the chainring during pedaling somehow. Perhaps that's not a valid fear.

2) The radius of my FD cage seems to not follow the radius of my chainring so well. So it kind of comes down to where on the FD I want that 3mm or whatever the right number is.

Harold74

Clearly, you know your way around this kind of derailleur. See the photo below taken from the top. My observations:

1) Both the inner and outer plates seem to angle inwards at the front of the derailleur. I'm unsure as to whether or not this is a design feature or a user modification.

2) The rear of the derailleur is actually pretty wide in my opinion. It verges on rubbing against the crank arm depending on how I set it up.

3) This setup works and seems to thread a pretty tight needles. So, like someone said above, I'm inclined to not mess with what works.

This FD, and another vintage RD that I have both seem to allow one to remove the chain without removing the derailleur, or vice versa. Would that have been the original design intent? If so, I like it.

Dfrost 

3mm FD clearance above the ring is excessive and leads to lower quality shifts and potential chain throws. Here’s one of mine, with about 1mm clearance at the tightest point as it swings. Looks like it will hit, but it clears because the FD cage rises as it moves outward. (Yes, I know that there are missing chain ring bolts. This was a trial fit.)



You should definitely rotate the FD so that the outer cage plate is parallel to the chain rings. The FD cage is designed to be wider at the rear. I would strongly advise not bending the cage plates! Whenever I tried that in the past, I worsened the shifting, and could never could get it back to the original shape. That cage doesnt look like it has been modified. But nothing wrong with that idea of adding a small washer at the bottom, although the screws that connect the cage plates may not be long enough. But I’d get the basic adjustments correct first.

Do you have a good bike repair manual? I like Lennard Zinn’s “Zinn and the Art of Bike Maintenance”. Good illustrations, clear explanations for everything from simple to quite complex.

Dfrost 

Why worry about a plumb arm on the big-big? If that was your goal, the chain will definitely be too long.

My chain sizing rule is to wrap the chain around the biggest cog and the big ring, without going through the RD. Then add one inch, minimum (two links). This ensures that a shift to the big-big won’t hurt anything. I don’t worry if the chain is loose on the small-small. Note that if you increase the size of the largest rear cog or big chain ring, the chain is likely to be too short.

squirtdad

looks as good as it gets to me

BITD (way before 86 10 speed (2x5) and 12 speed (2x6)) it was recommended to not cross chain (big/big, small/small was considered cross chaining) due to the high angle and stress it put on chains and wear on chain rings. But I don't ever remember it being impossible (unless an error was made). Cross chaining became less of an issue with 9/10/11/12 speed chains, being thinner and more flexible

I would not remove a link at all, based on the derailler position in Big/Big that one link would likely make it to short to run big/big (been there done that)

As long as you are not rubbing on the derailler in low/low you should be good (this is low low sizing works, i posted a video on it eariler)

Harold74

I misspoke and was thinking of those FBig-RSmall plumb cage diagrams that you see in the Shimano derailleur setup instructions when the max cassette sprocket it smallish. So far, on the two chains that I've set up, I've done it exactly as you described above, with good results.

Harold74

I've got pretty much every popular bike repair manual available, even the old one on how to maintain and operate your ten speed. I do have Zinn and that's usually where I start.

Harold74

Yes, I watched the video, thank you for that. My current setup basically meets all three methods / criteria:

1) Big-Big.
2) Small-Small
3) Plumbish at Big-Small, although not perfectly stacked over the pivot.

With all of that about as it should be, I feel pretty good that it's dialed in about as good as it can be.

Below is the Big-Small combo. I've been assuming that, when we discuss the gearing like this, it's always CHAINRING-CASSETTE when we say BIG-SMALL etc. That seems to be what the romans are doing...

Harold74

I have another idea to table for consideration, again utilizing a short cage derailleur where one would normally use a medium or long cage..

Above, we contemplated adjusting the front derailleur limit screws to preclude travel to the granny ring. Essentially, this would turn my 3x7 into a 2x7. Instead, what if I adjusted the rear derailleur limit screws to preclude travel to the largest of my cassette cogs? Essentially, I would turn my 3x7 into a 3x6.

If I've done the math correctly:

1) 3x6 should preserve 95% of the 3x7 gearing range compared to 88% with the 2x7.

2) The easiest 3x6 gear would be 86% as easy as the easiest 3x7 gear. It would be 72% for the for the 2x7 setup.

Viewed in this light, 3x6 seems quite attractive to me, being quite safe and allowing me to indulge my short cage fetish without sacrificing much. There aren't too may climbs that I couldn't tackle using [granny + second largest rear cog (24T)].

Thoughts?

Kapusta

Just one: Good God, you are complicating this.

Just stay out of the small small combo, and even if you screw up it is not that bad.

70sSanO

^ This is really the answer.

I ride a triple, and I’ve pushed the chain wrap on my RD, but could still ride in the small-small. But I’ve never ridden in it. I’m only in the small chainring for climbing far beyond what I can climb in the middle ring. It is never a normal riding ring, it’s a bailout ring.

The effort it takes to go from the lower cogs to the highest, just to go faster, far exceeds a simple shift to the middle chainring.

John

Harold74

I'm complicating it by design and for fun/sport. I enjoy thinking deeply about new things like this and it makes the experiences of both bike building and bike riding more enjoyable for me. If all I wanted was a bike that ran well, I'd just drive a sack full of cash over to the LBS down the street and say "GIVE HAROLD BIKE NOW".

Kapusta

You asked for thoughts and I answered honestly

If you are complicating it by design, then you are on the right track, and keep up the good work

Harold74

It's certainly an answer. it's the answer that I myself have been proposing since the beginning. And I'll try that out for sure. At the same time, though, I really think that the 3x6 solution provides another answer that has some definite advantages and very few compromises.

Clearly, many here are bothered by the potential safety implications of potential user error in avoiding small-small. And, as I mentioned earlier, I recently dropped into the granny gear unintentionally on a ride on my way to the middle ring so it's certainly possible. 3x6 eliminates that concern while sacrificing almost none of the original gear range.

If I do attempt 3x6, I'll probably still size the chain for big-big 3x7 to retain more future options with that same chain. That said, I could size the chain for big-big 3x6 and tighten things up even more. There's a chance that I or someone else might later adjust the RD limits back to 3x7 without re-chaining and, thus, invite a big-big failure. That seems a pretty remote possibility though.

Harold74

Thanks, it's been an interesting evolution for me. Initially, I thought that I could have anything that I wanted on most any bike. I quickly found out that's not the case and concluded that, most often, I'm best off restoring things to their original, functional condition. Now I feel that I understand a few things well enough to be able to improvise a bit, as I'd originally hoped.

squirtdad

Or you could just use inexpensive things like the correct long cage derailler instead of trying to hack a short cage.

Harold74

I sure could. But, then, I think that I've made it pretty clear that I'm interested in exploring less conventional solutions.

I'm grateful to have received a diversity of opinions on this but, at the same time, I don't expect anyone to stick around indefinitely if they are not enjoying the nuances of the discussion as I do.

squirtdad

oh I am enjoying the ride, just pointing out that big bucks at the LBS is not the only way to go for solid working solutions.....that may or may not work with your design vision.

now totally off topic.....do they still make Old Dutch potato chips? (grew up watching tv from Lethbridge as we got it better than US stations for a long time )

70sSanO

They still make Dutch Boy paint.

John

70sSanO

Or you could swap out your 12t for a 13t and have 13/28 7 speed.

Since 12 is bad and 14 is good 13 might be a good compromise. We are only talking 1t.

Plus 36/13 might be more enjoyable than 36/14.

I’m old and 38/14 is barely acceptable. I’ve toyed with going to 13-15-17, but I really like the 14-16-18-20 gapping. For me it’ll probably be fine in a year or two.

John

ShannonM

That's a smart answer. 48x13 (97 inches on 700Cs) should be plenty of gear for a bike like this. I doubt most riders would miss the 12 much. The only potential snag I see is that it looks like they've got a freewheel, and individual cogs aren't always available anymore. If the decision is to lock out a cog, I'd lose the 12t... I know I'd miss the 28x36 way, way more than the 48x12, and 48x14 is still a 90 inch gear.

Also, I totally hear ya on the 14-16-18-20. That's what I've got on the back of my 45/42/30x14-26 6-speed setup, and it's the business for flatland cruising. The short-cage RD loves it, too... move lever; slight ease off the pedals; ker-CHUNK.

--Shannon

ThermionicScott 

Blocking out cogs is a hack, and you know it. If you don't need the 48/12 top gear, you could swap to a 46T big ring, remove 1" from your chain, and get better shifting across your triple, too.

70sSanO

46t is a great idea. You’ll get more top end than a 48/14, not lose a gear, and make your 36t more enjoyable.

John

Harold74

Oh yeah. Their salt and vinegar chips are still my favorite, although Miss Vickie's are a very close second.

Please rest absolutely, 105% assured that I do, in fact, realize that a conventionally sized long cage derailleur is one of the viable options here and the option that would be preferred by most.