Hi.

So here's my problem: (Yes, I've used the search here and all over the internet and can't seem to find an answer, sorry)

I shipped my Bike in a bike box, and when I received it and tried to re-assemble it, I found that the rear derailleur had no tension at all. The lower arm just goes forward, and the whole chain hangs down. My bike terminology isn't that great, so let me include a picture:

https://i116.photobucket.com/albums/o...o/IMG_0007.jpg

And also a close-up of the derailleur itself:

https://i116.photobucket.com/albums/o...o/IMG_0003.jpg

Circled in red on that image are the two joints which are very loose. Now, I've never really paid too much attention to my rear derailleur before I had this problem, but I'm pretty sure at least the joint marked with a "2" in the image should be really tight or spring-loaded or something, so that the whole lower arm (tension arm?) sits back, instead of just forward and loose.

It's not like it's just too loose and I can't back-pedal (there is a recently updated thread open about that), it's just completely loose, and if I try to pedal, all that loose chain just rubs against the wheel. It's like the tension lever (I think that's what it's called?) isn't doing it's job at all (keeping up slack in the chain?). I feel like it's just broken, like there is a spring that should be there that isn't, but I wanted to ask before I went and bought a new one.

If you're going to ask if this is a mountain bike or a road bike or what, umm, I think it's a mountain bike, but here is a picture of the whole bike since I'm really pretty bad with my bike terminology:

https://i116.photobucket.com/albums/o...o/IMG_0008.jpg

So, if my derailleur IS just busted, and I need to replace it, I have a few questions about that as well. I looked online at a few places...

-Do I want direct mount, or hangar? Do I need to get one that comes with a hanger, or can I use the hangar I already have (if I have one...??) I'm trying to understand the difference...actually I believe I have direct mount?

-Do I want long cage, or short cage? (I don't even know what that means?)

-Does it matter what sort of shifter I have? (Based on my googling and looking at my bike, I'm pretty sure I have trigger-shifting, and yes, it is indexed.)

-Any other size requirements I need to take into account, or if I buy the same number of gears (7 speed, for the 7 gears on my back wheel?) will it work?

Thanks in advance for taking the time to help me understand this.

Looking at your pictures, it appears that the spring that should be supplying tension at #2 is either broken or has become disengaged. At worst, you will be needing a new derailleur. You'll want a long cage derailleur. If you do have indexed shifting, you may need to replace the shifters and possibly cogs as well, as SunTour is no longer in business. Otherwise, just set it up for friction shifting; it's much less fussy about these things.

If you take the bike to a shop they should be able to set you up with what you need.

Your frame has an integrated hanger.
Your current derailleur is a long cage. If you replace, get a long cage.
As noted, Suntour is no longer in business, so if you want indexing you need to get new shifters as well to match the derailleur you buy. You could perhaps find one the same as yours on e-bay, but that's going to be a lucky find.
I seem to remember that some Suntours could be mounted so that they had no tension. The fix was to remove it and wind it up then put it back or something like that. It's been years since I've seen it.

That's a real sorry-looking RD you have there. I agree with the other posts and your theory: springs either broken or released from their end points. The #1 joint can usually be disassembled and inspected, can't rightly say about #2. With it looking like that there is little to lose by trying to disassemble and repair, it won't work in its current state anyhow.

Yep, MTB, probably from the lower end of the spectrum.

Sure looks that way. Can't tell whether its decidedly fatal or if its fixable though.

Low-to-mid range stuff is cheap, might save you a lot of frustration.


Don't know if I've heard the phrase "direct mount" in this situation before. Bikes can have either a fixed derailleur hanger that's an integrated part of the frame, or a removeable hanger screwed to the dropout, or the RD can have a bracket that's clamped beneath the wheel axle nut. There's also something called an "adaptor claw" to let you mount a high end RD to a frame w/o derailleur hanger. Your bike anyhow falls into the first category.
Considering the condition (and the mystery circumstances of the event) you might want to check the alignment of your hanger, in case its also gotten pulled out of position by whatever that upset the RD.

Long/short cage basically refers to the distance between the two small sprockets (AKA guide pulley and tension pulley) in the RD. With the gear span of a MTB you want long cage to be able to deal with all the slack you can get.

In general terms it does, but I don't really know how finicky 7-speeds of your vintage are. For the current systems there are different actuations ratios one needs to consider to get an indexed shifter to work well with the RD and cassette/freewheel of your choice.
According to this site there's only one sprocket pitch for "standard 7-speeds", which improves the odds of getting your bike running again with minimum effort.

I'd say that odds are very good that you'll get it running again if you get a long-cage, 7-spd RD. One can usually run a 8-9 speeds chain through a supposedly 7-speed RD, but I have no personal experience of the opposite.

On a side note:
In the pic it looks like your chain is on the big-big combo, and still is rather slack. You could probably benefit from shortening the chain with a few links, and try to avoid riding in both big-big and small-small.
When you replace the RD, do the cables as well. If it hasn't been done for some years it'll improve shifting.
The chain doesn't look too healthy on the whole, it seems rather stiff in the pic. I'd like to recommend a chain treplacement too, but depending on wear that might lead issues with chain skip and you needing a new freewheel/cassette.

Awesome! Thanks for the replys, everyone.

As per a few of your suggestions, I took it off to play with it.

Yes! Thank you, you are right. Once I took it off, I loosened the whole thing, and swung the arm up around (360 degrees) and bam! It wants to go back to how it was before--aka it's providing tension now. I put the whole thing back on, and there's proper tension now!

But when it was off, I was messing with the screws. Perhaps because of that, or perhaps because it's bent or another problem, my shifting's all messed up. For the most part it just needs some adjusting, I think, but when I adjusted it to the point where it would actually get the chain onto the highest gear, it started to hit the spokes when I went into that gear. So I think it might be bent?

I'm going to try to find another Suntour on eBay, but for now, would it be safe to ride it without shifting the back gears, just for a few days? Just adjust it so that I can shift it onto the mid gear, and then not go up or down? Or is this a bad idea?

This sounds like a good time for you to learn to adjust your rear derailleur:

https://bicycletutor.com/adjust-rear-derailleur/

Cool, thanks. Very informative. After adjusting, I can now shift 1-6 (the smallest ones) no problem, still can't hit 7 (if the deraileur ever gets that high, it hits the spokes. no matter where the screw is. I think it's bent.). I just won't use 7.
thanks for the help , everyone.

If it's a 7 spd freewheel/cassette, and it's hitting the spokes, you have a bent derailleur hanger (or equivalent). This may require replacement - or brute force. I am not going to be the one here to explain the methodology involved. I'd suggest a trip to you LBS. You're almost home!