I'd like some help identifying the type of free wheel that's this 1983 Trek 620 that I recently purchased. The '83 620 is on the lower end of the spectrum for this model, but this bike has a 24" frame that fits me very well. Also, I couldn't resist the Grab On handlebar foam grips.



According to Trek brouchures I've seen, the bike came with an Atom Helicomatic 6 speed 13-28 free wheel, which doesn't appear to be what's on the bike now.



Can you tell me whether this is a suitable free wheel for touring . . . it rides great so far, but I haven't had it out with a load, yet. Also, is there anyway to tell from these pictures whether the bike retains its Heliocomatic hub? I've seen posters decry this type of hub and would like to know if I may need to replace it.



Thank you.

I vote for Suntour, Maybe a Winner Pro. For the most part there is not enough information in the pics. Can you take the wheel off the bike and post a good pic of the FW center? OH remove the skewer too.

Provided it is a quality FW it should be fine for touring but whether the gear ratio agree with you is another matter. If you live in or plan to ride in hilly terrain you may want something wider.

The type of tool needed to remove it will be the biggest clue. The brand and sometimes the model is often written on the body.

Looks like it's set up similar to my '83 600, which I've aimed towards a 620.
Isn't looking Helicomatic to me, but I'd need to see more - like the wheel pulled.
Mine:
Front: Cyclone MkII FD with a 52/44/28 crank. Your large/middle ring gap may be smaller.
Rear: MkII GT with a 13/24 freewheel (Suntour hubs, too)
I put bar end shifters on mine.
28*24 gives me a pretty low gear, but what kind of touring (weight carried + terrain) are you tackling?

I've never seen a high flange Helicomatic. It usually has a big ol' HELICOMATIC sticker on the hub.

As far as whether it's suitable for touring... I'm a wuss and I would want at LEAST a 28 big cog in the back- yours looks like a 21 or so.

As far as the 620 and it's position... it was ALWAYS a good and upper level touring bike during it's time of existence- always second only to the 720.

As far as the 1983 Trek 620- it's only slightly less desirable as a touring bike because of the sidepulls (but even the best touring bikes of a few years prior had sidepulls and centerpulls).

As far as YOUR particular bike... It looks like you've had the wheels replaced- which I think is a good thing. Check to see what those hubs and rims are. If they're not stamped, the QRs might have come with the hubs. It looks like you've got a really nice derailleur upgrade with the Cyclone MII setup.

IMO, I'd get one of those 6 speed Shimano 14-28 freewheels (or the 14-34 if you're carrying a lot of weight). Steal the Sachs/Huret shifters off your Passage and replace whatever is on the 620. Then score a set of dual pivot Tektro brakes (I think they're the R539), make sure your stuff is greased up and go to town. IMO, dual pivot sidepulls have as much 'stopping power' as any of the canti brakes I've used.

Pull the wheel off and look at the freewheel. The brand will be right on the rim of the hole. Looks like the wheels are not OEM as the rims definitely are not.

Thanks for your thoughts on the the FW. Yes, the gear ratio is what I was concerned about; however, the smallest ring on the crank seems likely to give me some effective options for hill climbing. I'll have to test it out and see.

I'll see what I can do with providing additional pics.

Thanks for your informative reply. After I take the bike out and see how it responds to various conditions, I'll definitely take a look that the Shimano you suggest.

Thanks for your helpful information. As far as the kind of touring, I only do relatively short tours, typically no more than a week. I will add rear and front racks, but I'd like to keep weight under 40 pounds total. In terms of terrain, I do a lot of rails/trails, but also Midwestern rural roads that have steep, but relatively low hills.

BTW your bike looks to be set up with a half step plus granny. I believe these normally had a slightly wider gear ratio in the back, and you shifted between the chain wheels more often to sort of 'split' the rear gear. Look up threads with information on half steps on here or check Sheldon Brown's site.

Depending on how your other bikes are set up, you find swapping out the middle chain wheel for a more common (these days anyway) alpine set up.

I think I saw this bike on CL a couple days ago, if you got it for what he was asking, you got a very very good deal. I was tempted to grab it, but it's too big for me, and I wasn't sure about the non-original components. Anyhow, if it doesn't work out, you can turn around and sell it for a good profit.

Hey Josh,

I don't think that the person I bought this bike from had posted it on CL yet, although he has other bikes up. I paid $200 for it. Although the bike is missing some of it's original accessories (rear rack, bottle cage, and pedal cages) I thought that was a reasonable price, especially since he put on new cables, tires, and tubes.

Thanks for the suggestion to check out Sheldon Brown's site. I had heard of "alpine gearing" but I didn't know what it referred to.

It's nearly impossible from those pics to say the gearing is a half-step plus granny or an alpine-plus granny, or what. If you will count out the teeth and publish that, I or someone can tell you if it follows either of those models. both of them have rather specific relationships between the gears and between the fronts and the backs, that try to give you even jumps as you shift your way up throughout the gears, and to eliminate wasted gears - if you have 2x5, you get 10 distinct gear ratios with no duplication, for example.

The free wheel has a ratio of 13/14/15/17/19/21. Crankset is 28/45/50.

Your lowest gear will be 28/21*27 which works out to 36 gear inches. That is low enough for climbing a hill with luggage on the bike, for most people. Some people would prefer a lower low and would replace the freewheel. I never feel the need for a gear lower than 36 inches, but I'm better at hill climbing than some people.

Need more pictures of the hub with the wheels taken off.

But, I'm going to take a guess on the hubs and say that they may be Normandy High Flange hubs. Definately not original and not helicomatic. Which is a reason to be very happy. I would get a more spaced out gearing ration, Sunrace makes a real nice replacement sets. I think I have a 13-28tooth one that is very nice.

Thanks noglider. If I understand the formula you used, you take the number of teeth on the smallest crank, and divide that by the number of teeth on the largest ring on the freewheel, and multiply that by the size of the wheel to get gear inches. Is that correct?

What was the problem with helicomatic hubs?

Undersized bearings in the rear hub. Much easier for the hub to fail, needed greasing fairly frequently to prevent bearing cracking, excessive heat, scorched bearing races.

The helicomatic mechanism or cog grooves were fairly novel however, but all the fancy machining and fitment cause a lack of space for properly sized rear hub bearings. Front hubs were fine, no issues.

Correct. And by size of the wheel, if you're using 700c, that equals 622 + 2*tire height, so assuming 700x28's, then 622+2(28)/25.4 (convert to inches) = 26.69". 28/21*26.69 = 35.59 gear inches.

noglider just rounded to 27, which would be a be a 700x32.

Now I changed out my wheelset from a 27" to a 700c. Has your bike been changed to 700c? That will allow for a slightly wider/taller tire. I changed out mine primarily for fenders. I forgot about that in my sample calculation.

Thanks for the information!

The bike still has 27" wheels, but it has enough room for fenders, which I do want to add, so I'll probably just stick with the wheels I've got.

All of 'em can be slightly different, but with fenders my bike has very little clearance running 700c tires that actually measure 29-30. That's a total of 682mm, which less the 630 (27") = 26mm or maybe you fit a 1 1/8". Yours may be "looser".

I don't recall which wheel was tighter - often it's the front, but for some reason I'm thinking rear on mine. Not sure. I could change out the fender mounting hardware for something a little more clearance friendly, too, but it fit the tires I had.

Yes that's how you calculate your lowest gear. Any gear is calculated as F/R*D where

F = number of teeth in front
R = number of teeth in rear
D = wheel diameter in inches

This gives you the effective wheel diameter, if you were riding an old fashioned high wheeler bike. Back in those days, to go faster, you bought a bike with a bigger wheel if your legs could handle it.

Some perspective: 25 or 30 inches is about the lowest useful gear that adults use. 72" is a moderate gear for general purpose if your terrain is flat. 100" is for hammering really hard or going downhill fast. Very few people can pedal at 90 rpm in a 100" gear for long, so you rarely want a gear higher than 100" or 110" as a top gear.

Now make a chart of all your gears. See the pattern of shifting, going from one gear to the next.