New (Old) RD Issues
 

So I bought a set of Suntour derailleurs for the bike I'm working on and I'm having some issues getting the RD just right. It seems to be functioning ok (a bit of an issue when I go large cog/large chain ring but no biggie), but when I peddal backwards the cage tends to pivot with the lower pulley moving towards the chainring before the chain begins to rotate. This causes the chaing to become really loose on the top and drag across the chain stay. :mad:

The pulleys seems to be spinning fine and I've tried adjusting the angle of RD, but nothing seems to work and I'm really at a loss here. :twitchy: When I hold the lower pulley as I spin backwards - no problem. So I tried tightening the screw that the cage pivots on, but it is as tight as it goes. Any othe suggestions?

I know the easy answer is, "don't peddal backwards" but the bike isn't for me and I'd rather not hand it over with a list of instructions.

does it do this in every gear or just the big/big combo?

What kind of RD does in mount to a hanger on the frame or by a 'claw' attached to the dreailleur and bolted to the wheel slot in the dropout?

which angle did you check? a derailleur hanger/claw that is bent inward or outward couls cause this but also and harder to check one that is twisted from the centerline of the bike would cause it too.

It does this in every gear. My issue with the big/big is that while I can get into the big cog from the small chainring, I can’t from the large chainring. When I adjust the RD so that I can, it hits the spokes when going to the large cog on the small chainring. Essentially I can’t get to the large cog from both chainrings – it’s one or the other depending on how I set the RD.

The RD mounts directly to the threaded dropout, no claw.

The angle I was referring to was the angle that the RD hangs (if that makes sense). The cage was bent originally, which I “straightened” by hand – maybe it isn’t exactly straight yet?

This is also likely to be an issue with the freewheel mechanism in the rear wheel and not a derailleur problem. If there is too much drag or friction in the freewheel mechanism the exact thing you describe will happen.

Anyway I can "diagnose" this? Do I have to disassemble the freewheel and regrease the bearings to fix this, assuming that is the problem?

Edit - I just read Sheldon's instructions on lubricating a Freewheel - I will try this to see if that remedies my issue.

OH I never thought of freewheel lube!!

you need to check the hanger and this is tricky. if the derailleur was bent it is possible the hanger is slightly bent and that can be causing some of the trouble. you migt be able to remove the RD and wheel and lay a straight edge across the dropout face and the hanger but the best way is to have a shop use a guage on it.

Also sheck the position of the rear wheel in the dropouts. if the wheel pushed all the way back that may be causing some extra drag. most frames have a either a spacer bolted into place or those dropout ajustment screws so you can properly adjust the position of the wheel.

Thanks BG - I can tell you that the wheel is indeed all the way back and that there are no spacers or adjustments screws. Can/should I look into getting some spacers?

While I can't rule out that the hanger is bent, I highly doubt it - I should note that the RD in question did not come with the bike but was an eBay purchase I made to replace the Simplex that came with the bike at the time of purchase.

Just remove the wheel and check for free movement of the freewheel.

OK what type of bike? the axle of the wheel should positioned just over the hanger bolt, I think there was a thread about this in the C&V section last week or so.

any pics? does your frame have the holes in the dropout for adjustment screws?

http://www.thethirdhand.com/Product_.../LS-0102SF.jpg

Here is the best pic I have on hand - I can take one of the drive side dropout tonight if needed.
http://i711.photobucket.com/albums/w...d/IMG_4799.jpg

It's a '72 Raleigh Grand Sports. I'll have to check when I get home, but I don't recall seeing any holes for an adjustment screw.

See how this screw runs through the dropout and thus pushes the wheel forward

http://img59.imageshack.us/img59/1500/hh9p96256.jpg

on this bike they use a similar dropout but most of the slot is filled in to set the wheel where it should be

http://www.bikeforums.net/attachment...4&d=1329430799

If the freewheel isn't seized, it sounds as though the chain is coming off a pulley to the side when you backpedal, pivoting the cage until enough force is applied to slip the chain back on. This usually happens with a misalignment of either the rear derailleur hanger or the derailleur/cage itself (seems likely in your case).

As for the shifting issues, we'd have to see a picture. The chain might be too short.

Does the Simplex have the same "geometry" as the Suntour?

I had an old Suntour equipped 10 speed that had the RDER turned into a "pretzel" by vandalism.

I installed an old "box store" Shimano I had from the junk pile.
I had trouble with the guide pulley wanting to rub against the largest cog.
I ended up getting a Shimano Tourney and relocating the "attaching hole" in the dropout to make it work.
It still wasn't "right", but it shifted the gears.

Here is the thread I was thinking of over in the C&V threads. it also has a great pic of dropout spacer or whatever you want to call it. perhaps you can source one at your LBS

http://www.bikeforums.net/showthread...dropout-is-for

http://i856.photobucket.com/albums/a...1/IMG_1999.jpg

Thanks BG, I will look into those spacers as I confirmed that there is no hole for an adjusting screw.

As for my peddaling backwards issue; it was indeed a freewheel issue. A little lube and I was in business. Thanks for the help!

Glad to hear you got the problem fixed. too bad we found another issue for you but atleast you have something to do over the weekend.

Those dropout spacers might be handy, but they are in no way necessary.

btw I don't think it's been mentioned, but the large ring/large cog combination (as well as the small ring/small cog combo) really shouldn't be commonly used, as the chainline is at its worst, causing premature wear on the parts and inefficiency in the drive train.