Hello all...

I've been riding my old beater for a couple of years now, we get along pretty well, but I'd like a bit more selection of gears if possible.

I had been thinking that I could change to a 'bigger small' front ring, but then I learned that it's 118 BCD and 118 is obsolete. That it seems would require a new crankset, and I don't know enough to even begin to pick one for this bike.

So then he say's to hisself HEY! How about 7 or 8 in the back? Then I learn all about the (scary music please) Atom Helicomatic.

(Think, think, think...)

New wheel set? Go with new hubs, freewheel, cassette in 700s? Start with something like this maybe?
https://cgi.ebay.com/NIB-Sealed-Cartr...QQcmdZViewItem

If any of ya'll might have 'been there done that' I'd sure like to hear what you learned, good/bad/otherwise.

Thanks! JT

I think you'd do better to find a vintage 7-speed set up. That would mean at least a different rear wheel. I recommend this, because to go to 8 speeds, you'd need to change to a cassette, and you would likely need to spread the rear, and possibly change the shift levers. With a seven speed freewheel, you'll have more options for changing out gearing, with minimum hassles changing out other things.

I went to a NOS 7 speed on my Continental.
It has worked out very well on this old touring bike.

What problem are you trying to fix? I assume your 520 has a triple. I have never heard of anyone wanting a bigger granny gear. What kind of set up do you have in the front now?

What problem are you trying to fix? I assume your 520 has a triple. I have never heard of anyone wanting a bigger granny gear. What kind of set up do you have in the front now?

Good point. Perhaps what I wish I had was a smaller middle? (HAHA, yes, that's why I ride in the first place )
The difference between the small and middle on the front is a big jump.

Possibly that 28-45-50 chainring setup that was popular in Waterloo for a couple years?
Always disliked it myself, but not to the point of actually doing anything about it.

Should be able to swap in a different crank for a couple of bucks... find a used triple with a square taper and it might be cheaper than buying new rings.

Sounds like your bike has a virtual half-step plus granny setup, where the difference between the middle and big ring is quite small compared to the difference b/w the middle and the granny. You can change to a smaller middle ring to make the ring combination more akin to that of a mtb, but the derailleur, if it's original, may not be able to handle the jumps too well. This kind of setup calls for a front derailleur that is more three dimensional, where the cages are generally shorter and the distance between them is much greater.
As you said, 118 is an oddball bcd and the chances of finding something are slim. You're probably better off changing cranks to something with a more useful bcd like 110, as rings are widely available (i.e. - Sugino AT, old Shimano Deore or XT etc, etc.). Used deals can be had online from time to time. You can post something in the ISO/WTB sticky here or maybe try your luck on eBay.
Good luck!

allow me to piggy-back on this thread: I'm trying to help a friend with a similar bike, a 1985 Trek 620. It has the same gearing 50/45/28 triple with a 5-speed Helicomatic in the back with 28t cog. We have determined that the Huret Ecopar is toast and have swapped in an early Shimano Deerhead RD but it's not happy shifting this modest range, either...you'd think it would be a walk in the park for it. The original Huret FD does an OK job shifting the big jump from 28 to 45, but it wouldn't hurt to find something even better: any specific suggestions for a "three dimensional" FD that would do the job? I'm going to try another approach and check out the RD hanger for straightness any maybe swap in a newer chain, tho the old one still shows no real stretch...It has new cables and housing...

I think the original deerhead XT r/der. came in a few different cage lengths, so you may have the shorter one, though I'd be suprised if it couldn't shift up to a 28t. Even my Shimano Sante rear on my Davidson (which has a very short cage) shifts up to a 26t no problems at all. Are you sure there is nothing wrong with it? Is it setup correctly, with the low screw turned out enough to allow the jump? Does the shifter have enough travel? Is there a lot of slop at the pivots?

As for the front derailleur, there are many that will work. I have an older XTR on my Miyata and it works very well, and that's with a 48-40-26 setup. Any decent late-80/early '90s Shimano (DX, LX, XT, XTR) etc.) or Suntour (XC, XC ltd. etc.) derailleur is my recommendation. The main issues you may run across when changing to a newer MTB-type derailleur are:

1) The bottom of the derailleur cages, where they join with a spacer and bolt or screw, may be very close to hitting the rear shifter cable when the derailleur is set at it's optimum level (i.e. - 1-3mm above the largest ring). However, this is typically only an issue for bikes where a) the cable routes on top of the bottom bracket and chain stay instead of under (Personally I don't know about the 620; you will know that of course), and b) if the larger ring is anything less than approx. 50t, which yours isn't. My Miyata has this problem (the derailleur is sitting a few mm higher than optimum, but luckily it still shifts quite well).
2) The outer cage may rub the inside of the crankarm when shifting to/in the largest ring. It depends on the crank and the derailleur combination. You will just have to try it to find out.

-Leigh

I think the original deerhead XT r/der. came in a few different cage lengths, so you may have the shorter one, though I'd be suprised if it couldn't shift up to a 28t. Even the Shimano Sante on my Davidson (which has a very short cage) shifts up to a 26t no problems at all. Are you sure there is nothing wrong with it? Is it setup correctly, with the low screw turned out enough to allow the jump?

As for the front derailleur, there are many that will work. I have an older XTR on my Miyata and it works very well, and that's with a 48-40-26 setup. Any decent late-80/early '90s Shimano (DX, LX, XT, XTR) etc.) or Suntour (XC, XC ltd. etc.) derailleur is my recommendation. The main issues you may run across when changing to a newer MTB-type derailleur are:

1) The bottom of the derailleur cages, where they join with a spacer and bolt or screw, may be very close to hitting the rear shifter cable when the derailleur is set at it's optimum level (i.e. - 1-3mm above the largest ring). However, this is typically only an issue for bikes where a) the cable routes on top of the bottom bracket and chain stay instead of under (Personally I don't know about the 620; you will know that of course), and b) if the larger ring is anything less than approx. 50t, which yours isn't. My Miyata has this problem (the derailleur is sitting a few mm higher than optimum, but luckily it still shifts quite well).
2) The outer cage may rub the inside of the crankarm when shifting to/in the largest ring. It depends on the crank and the derailleur combination. You will just have to try it to find out.

However, with all that said, I assume you are not changing the ring setup, so leaving the original Huret is probably the best idea. These type of derailleurs (long cages, with small distances and little vertical staggering between them) work best for such an application. If you really want to change, I can personally tell you that the 1st gen. Suntour Cyclone is a great derailleur; well-made, sturdy and shifts very smoothly. I ran one of these on my Miyata until I changed the gearing. It shifted a 26-48-52 flawlessly.

-Leigh

I have a green 1984 520 and ran a Sugino touring 26x36x46 triple with SRAM 11x32 cassette. Needless to say things were pretty slow at 21.7 gear inches

On my 620 I grew very frustrated with the shifting qualities of the Maillaird Helicomatic freewheel. A great concept, and nicely done, I put several chains on it in an attempt to find one that would function well.
At length I gave it up and put an Asian hub of some description on it with a Suntour freewheel. Problem solved.

Ohhhhhh, shiny! (Voices like the little green guys in the claw machine, toy story)
Wish mine looked like that under the grime.

Antipodes and Mooo: thanks for the advice. I have tried an early Deore FD but the inner cage jammed against the middle ring (very strange, but true) so I'm going to stick with earlier shaped FD cages. I'll see if a new chain and RD make the FD shifting improve, if not I have a few (Japanese) options to try. Could be that the rear hub needs to go, but for a Helico it's in very good shape, I told the owner to just use it till it strips out or he's ready to rebuild the rear wheel.

Thanks all! I think I'm learning stuff...again. Ouch.
Just for fun last evening while fixing a flat on my son's bike I tried his 700 rear wheel on the 520. His is a recent Jamis with el-cheapo Shimano components. Jamis website lists the wheelset as " Alex AKX R1.0 wheelset 700c 28H radial front/ 32H 3X". The derailleur was able to shift to 7 of the 8 without any adjustment, no interference. It just wouldn't quite get to the big sprocket. It looks like there is plenty of adjustment left in the limit settings and there appears to be room left to set the brake pads on the wheels. It fit the frame with no spreading, no need to force anything at all. It really seems like it works?!?!? Am I missing something or should I just swap out wheels/tires, adjust it and see if I like it?

Thanks again!
JT

You're not missing anything. You'd want to check the dish on the wheel to ensure you have proper braking. I presume you have friction shifting?

I don't know, but your son is.

It ALMOST works. Grrr. Not quite enough adjustment in the rear derailleur to get all 8.

What I DID learn was just how crudded up the 25 year old freewheel is. WOW.... zoom on the fresh(er) parts. Quiet, smooth, faster, just plain better.

So now I'm looking around for NOS 7 speed (thank you USAZorro) or doing it the 'ugly' way and using a 7 speed cassette with a spacer on a new wheelset.

NOS 7 speed would be better if they are 27" setups. I'm guessing they might be?

JT

I have a friend who went with a relatively new Deore for his touring build. He seemed happy with it and the long cage should be able to handle large jumps if I am correct