I could use some freewheel advice
 

I'm hoping I can replace my freewheel to improve shifting performance. I don't know much about freewheel compatibility so I figure I will ask the experts.

Right now I have an Atom 5 speed "corncob" with a Campy NR RD and crank. I am assuming that my poor shifts are a 2 part problem of freewheel wear and design. It is my understanding that there are great vintage freewheels from suntour, sachs and others but I would prefer something new and easy to find.

It seems that Shimano and IRD are the most promising choices. What is the maximum size that the NR derailleur can handle? With 126mm rear spacing, can I fit a 6 or 7 speed compact freewheel with altering anything else? Is IRD's cost all bling factor or is there a performance difference, have there QC problems been taken care of?

I realize that shifting problems can also be caused by improper chain length. I am having a little trouble gauging whether mine is correct so I will take a picture with the chain in big-big and small-small. It may be a technique learning curve too, this is not my first friction shifting bike but it is my first with downtube shifters.

Thanks in advance for the advice.
Matt

EDIT: as promised, here are the pics.

Small-small:
http://farm4.static.flickr.com/3654/...12a8f930_o.jpg

Big-big:
Removed old picture, new picture is further down in the thread

The freewheel in question:
http://farm4.static.flickr.com/3587/...4558d80a_o.jpg

With 126 spacing you can fit a 6 or an ultra-7. I don't think that Shimano made an ultra-7, at least I've never seen one. Suntour did, and I use one. The shifts are a bit more prone to skip (2 cogs for the price of one), I think, than a normally-spaced 6 would be. Without shaped teeth, friction shifting is an art learned through long practice, and familiarity with your particular equipment/setup, and I'm certainly no expert at it. But I like it, and put up with it. You could respace your rear wheel to 130 and fit a 7-speed; and you don't really need to cold-set your frame's rear end to try that.

I don't have an IRD freewheel, but I'm glad they make them still. They do have shaped teeth, so the shifting should be pretty good.

A NR derailer can do 26, maybe 28 teeth.

A Suntour Ultra 6 might be your best bet.

It would add one more gear and still fit the spacing on your wheel. Just looking, our chain looks a little tight to me. Has it been a while since you replaced it? I'm always surprised by how fast a chain can stretch when then affects how the bike shifts. A new chain makes a big difference. The usual rule of thumb is to wrap the chain around the two bigs without the RD, then add a link.

Here's a Suntour Ultra 6 that is similar in range to your existing 5 speed. Best of luck.

http://cgi.ebay.com/NOS-Suntour-Pro-...3286.m20.l1116

You also asked how big a rear sprocket can a Campy NR handle? I run a 29 tooth on my Continental. It's tight but it works.

http://i125.photobucket.com/albums/p...voRecordRD.jpg

I can vouch for the IRD freewheels. They are spedny but worth it IMHO. They also use a Shimano freehub tool for easy on and off. I was running the original Regina freewheel on my Paramount and the shifting was terrible. I replaced it with an IRD and the shifting improved dramaticaly.

I have also had good luck w/ late model Suntour and Shimano freewheels as well. They are a bit less and I have found them on ebay.

If memory serves me, I think 27th is the max for the Campy RD you have.

I will keep an eye on that auction. The chain is actually new, I may have cut it a bit short though.

Is there a suntour model line up to be learn? Thanks for the help!

-Matt

Your chain looks short to me.

+1 - seems apparent in the big big pic.

As PB advised, search for a Suntour New Winner or Winner Pro Ultra-6 freewheel. These will fit your 120mm spacing.
A Shimano twist-tooth freewheel from that era will also work well.
Both will run fine with your new KMC Z chain.

6mm is a bit of stretching, but if you can find an index-capable Shimano 600 6-sp freewheel, especially an EX or newer, your shifting should be smoother. You'd probably need a new axle, though, since it will need 3mm more length per side.

I went from a 6-sp Regina friction to a 6-sp Shimano 600EX and it was a different bike, like it was waiting for me to shift.

The OP lists a 126 mm OLN, suitable for any 6 sp freewheel and virtually all 7 sp freewheels (nominally 127 mm OLN). You may need to shift some spacers from LH to RH side and re-dish the wheel but Atom freewheels tend to sit 'outboard' more than Asian freewheels in my experience (depending on model).

You don't have a corncob freewheel i.e. single tooth jumps. The NR rear mech was rated to 26t, the SR to 28t but you can push both by a couple of teeth with a little care. Campag mechs work better with a longer chain than shorter.

Edit: I see the auction is BIN, ouch pricey!!

Well, looks like I will be buying a new chain then...rats. How about these 6speed hyperglide freewheels from harris cyclery, 19.95 seems decent of course it does go to 28t.

You don't have a corncob freewheel i.e. single tooth jumps. [/QUOTE]

Ahh, I seem to have misunderstood, I thought the jumps appeared small and figured that it was. This should be a good learning experience for me.

+10 Chain too short. Go to the Sheldon Brown site, it has a simple and effective way to pick the proper chain length.

I will add what little I know. I have heard of several fellas running 28 t cogs. The problem I ran into was not the cog size but the total number of tooth difference. I had a 24 tooth difference and I had to get the chain length just right or it seemed like it would have either bent the NR derailer by being too short or it would not wrap enough chain like the chain was too long. At least with my set up the NR derailer would not have handled a 26 tooth difference. The 24 tooth was the max difference that it would handle. Just the way it seemed to me. Good luck and have fun

Ok, my chain actually checked out according to the Sheldon method. Here it is an additional link longer:

http://farm4.static.flickr.com/3664/...79b0478e_o.jpg

+1 - I'll second this. My setup was a Nuovo Record RD with a 52/42 chainring setup and 14-28 freewheel so 24t difference - pretty standard C&V setup. With the chain adjusted just right it worked flawlessly. One tooth too many and the chain would sag, one tooth less and the whole thing would bind if you accidentally shifted into the big-big combo.

With the original Regina freewheel (similar to that Atom) it shifted terribly but shifting was great with a Shimano Uniglide (twist tooth) type freewheel. I haven't used the IRD but suspect from the design that it would work great. Beggars can't be choosers these days but the big issue with the IRDs IMO is that they are shiny nickel plated silver. If they were black, gold, brown, or whatever i would be stocking up on them.

Yeah, I actually like the look of the IRD. After seeing what the NOS suntour and hyperglides go for IRD might be a real option.

I really do appreciate all of the help, this is a very murky subject for me.

Campy Record will handle 52-42 with a 13-28 or 14-28, but not optimally. You will need a longer chain.

That was the setup for racing over Smugglers Notch back in the day.

Sorry, I don't understand what you mean? I had the chain 1 link longer than this pic and it really sagged:
http://farm4.static.flickr.com/3664/...79b0478e_o.jpg

Correct, the NR (and SR) was originally designed for half-step gearing i.e. small total tooth differences. They aren't touring mechs, so either narrow freewheel/wide chainwheel difference or wide freewheel/narrow chainwheel difference.

Part of pushing the limits is finding the best fore/aft position for the rear axle to maximise chain take-up.

Hmm, this seems to be getting a little complicated, I will have to check what size the chain rings are. As you can see I have the rear axle toward the front of the drops, I assumed this was the correct position?

Moving it back is better. You may choose to remove the DO adjusters all together in order to really get it back there... it will allow a little more chain wrap which will help shifting. As far as freewheels go, you can't go wrong with a 14-28 shimano HG, ugly and all but they shift well... I have some 26T HG freewheel cogs saved up so I can convert them to 14-26. That is even more ideal for me. I don't like having to force the big 28. I am actually rocking regina DTs on both my record bikes, but I ride them so seldom it hardly matters. I have quite a few freewheels on hand so send me a PM if you are interested... I'll have to do a short survey of what I have but I recently pulled a suntour ultra 6 off a bike with the original HKK ultra-6 chain. They probably have no more than 100kms on them....

Yes, it will sag, especially on the smaller cogs. That's why I said "not optimally." The longer chain is for wrapping the 42/28. Old racers knew the chain was long so we just avoided using the small ring with the smaller rear cogs. Using a 52/42, "optimum" maxes out around 26, but I still don't use anything larger than a 24 on my old Record-equipped bikes.

If you want full-range performance with this gearing I recommend getting a derailleur with capacity to wrap more chain.

By the way, it looks like you've got the original 52/45 rings that came with the bike.

I'm not worried about full range, I have another bike with a 21 speed Deore DX group. I am just trying to make this group function as good as it can (hopefully).

Not saying that it is operating poorly, it just seems like it should/could be better.