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Replacing a SunTour rear derailleur spring

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Replacing a SunTour rear derailleur spring

Old 05-26-20, 02:50 PM
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Replacing a SunTour rear derailleur spring

I've got a SunTour LePree rear derailleur (the three pulley kind) with a broken spring that I'd like to replace. The spring in question looks like this, except that the "tab" in the center is broken off.



I've got a donor derailleur that I'd like to take the spring out of to put in the LePree, but I can't figure out how to get it out. I'm also wondering if I'd be able to get it back in if I did figure it out.

Any ideas?
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Old 05-26-20, 03:03 PM
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It just pulls out. That said, they are often rusted or gunked in there very tight. Soak it in penetrating oil for a bit. Then take an Exacto blade and run it around the circumference between the spring and housing. It should eventually loosen enough to get it out with some needle nose pliers. Good luck.
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Old 05-26-20, 03:06 PM
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I think this thread, starting at post 18, would be helpful. I took apart a Cyclone MK-II apart a couple of years ago, which has the same type of spring, and used this thread as a reference. It's not top of mind because it was so long ago, but my takeaway was that the little tab was easy to lose, so be very careful.

https://www.bikeforums.net/classic-v...nto-place.html
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Old 05-26-20, 04:30 PM
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Originally Posted by noobinsf
I think this thread, starting at post 18, would be helpful. I took apart a Cyclone MK-II apart a couple of years ago, which has the same type of spring, and used this thread as a reference. It's not top of mind because it was so long ago, but my takeaway was that the little tab was easy to lose, so be very careful.


https://www.bikeforums.net/classic-v...nto-place.html
Yeah, it is. I found that little tab on my floor yesterday evening, doing some cleaning up, and tossed it. It looked like it had broken off of something, sometime in the past...But noooooooo... I rebuilt a Suntour RD for the very first time, just that morning, combining 2 that had broken and missing parts. (no, there is no tab in the other RD, that's the tab I lost, and this RD was missing the Allen nut that holds the spring and the cage to the RD body, so that tab was long gone.).

I found this thread, and the other recommended just now. 🤦Thanks, Murph...

Hard to see how the spring will pop off, but I'm guessing that little tab is there to prevent that.


And I thought things had gone pretty well yesterday...

Cheers, Eric
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Old 05-26-20, 07:06 PM
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Originally Posted by Andy_K
I've got a SunTour LePree rear derailleur (the three pulley kind) with a broken spring that I'd like to replace. The spring in question looks like this, except that the "tab" in the center is broken off.



I've got a donor derailleur that I'd like to take the spring out of to put in the LePree, but I can't figure out how to get it out. I'm also wondering if I'd be able to get it back in if I did figure it out.

Any ideas?
Unfortunately yes. I'm pretty sure that the spring in the Lepree in no way bears a resemblance to the the one you're looking at. The only spring I've found to be compatible with a 3 pulley Cyclone model comes from a Suntour Sprint 6 speed friction model. I've made that swap successfully.
If it happens to looks like the same spring, then spray lube like crazy, use quality, narrow needle nose pliers, grab the centre tab and rotate the spring back to relax it to ease it out. Vica versa going the other way. Good luck.
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Old 05-26-20, 08:28 PM
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OK, here are some pictures of my own.

This is the LePree derailleur.



And this is the donor derailleur (an XC).



The part holding the spring looks like it could be interchangeable between the two, if that would be easier. How do the pivot pins come out? The XC part is in rough shape (hence it being a donor component), but I might be able to clean it up enough. It seems to me like the spring is wound to tight to come out easily. I'll keep trying unless anyone has a brilliant suggestion.
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Old 05-26-20, 10:53 PM
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It's quite the enigma.

Do you ever watch those box puzzles on youtube? I don't, personally. But at the 3:20 mark below he gives this puzzle a smack and the two halves come apart. Might try that.

.
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Old 05-27-20, 05:06 AM
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Originally Posted by Andy_K
OK, here are some pictures of my own.
The part holding the spring looks like it could be interchangeable between the two, if that would be easier. How do the pivot pins come out? The XC part is in rough shape (hence it being a donor component), but I might be able to clean it up enough. It seems to me like the spring is wound to tight to come out easily. I'll keep trying unless anyone has a brilliant suggestion.
I would try to remove the spring before disassembling the parallelogram. If you use a needle nose pliers to twist the spring tighter, it will create a gap between it and the aluminum knuckle. Then you can slip in a thin shim of aluminum cut from a Coke can, maybe 1" by 1.5" or just less than the circumference of the spring. Relax the spring. Then pull the shim clockwise to disengage the spring hook from the housing and try gently pulling the spring out. Greasing the outside of the shim may help. A thin exacto knife blade might help with the spring hook.
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Old 05-27-20, 05:13 AM
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Originally Posted by noobinsf
I think this thread, starting at post 18, would be helpful. I took apart a Cyclone MK-II apart a couple of years ago, which has the same type of spring, and used this thread as a reference. It's not top of mind because it was so long ago, but my takeaway was that the little tab was easy to lose, so be very careful.

https://www.bikeforums.net/classic-v...nto-place.html
Thank you for this pointer! Last night I disassembled a Mountech RD and found two wedges on the bench. I figured they had broken off somewhere, but now I know where they need to go. This RD has two springs, so two wedges to keep the split threaded posts from de-forming during assembly.
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Old 06-24-20, 10:35 AM
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Very pleased to find this thread with precisely the same question that I had. I've got the same LePree 3-pulley RD with a broken spring Andy, did you ever succeed in swapping out the spring?
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Old 06-24-20, 10:47 AM
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Originally Posted by JeffreyS
Very pleased to find this thread with precisely the same question that I had. I've got the same LePree 3-pulley RD with a broken spring Andy, did you ever succeed in swapping out the spring?
Nope. I gave up and just cleaned up the XC derailleur body. I couldn't get the spring out of any of them.
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Old 06-24-20, 11:01 AM
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FWIW, I did find that the cages of SunTour derailleurs with this type of spring are somewhat interchangeable. The longer story behind what I was doing is, I had (1) a short cage Superbe derailleur, (2) a 3-pulley LePree derailleur with a broken spring, and (3) a 3-pulley XC derailleur that was a bit scratched up and missing some small parts (the B-screw and, I think, a washer in the mounting mechanism). I bought the XC as a parts donor.

I started by moving the 3-pulley cage from the XC to the Superbe. This mostly worked. The short cage Superbe has the pivot stop in a different place than the 3-pulley derailleurs, so I had to remove the pivot stop pin. Otherwise, it works perfectly.



Having done that, I wanted to move the spring from the XC to the LePree. Since I couldn't get that to work, I instead moved the cage from the LePree to the XC. This also worked without any problems. I don't have a picture of that yet, but it basically looks like it did with its original cage, so it doesn't really need a picture. I've got it mounted on a bike that's mid-build right now and it has some play where it bolts to the derailleur hanger, so I think I'm going to need to harvest another washer or something from the LePree.
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Old 06-24-20, 01:03 PM
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Thanks for the prompt response, Andy. I'm a novice, so if you couldn't manage the spring swap, I don't think I will try!
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Old 06-24-20, 01:08 PM
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Originally Posted by Andy_K
FWIW, I did find that the cages of SunTour derailleurs with this type of spring are somewhat interchangeable. The longer story behind what I was doing is, I had (1) a short cage Superbe derailleur, (2) a 3-pulley LePree derailleur with a broken spring, and (3) a 3-pulley XC derailleur that was a bit scratched up and missing some small parts (the B-screw and, I think, a washer in the mounting mechanism). I bought the XC as a parts donor.

I started by moving the 3-pulley cage from the XC to the Superbe. This mostly worked. The short cage Superbe has the pivot stop in a different place than the 3-pulley derailleurs, so I had to remove the pivot stop pin. Otherwise, it works perfectly.



Having done that, I wanted to move the spring from the XC to the LePree. Since I couldn't get that to work, I instead moved the cage from the LePree to the XC. This also worked without any problems. I don't have a picture of that yet, but it basically looks like it did with its original cage, so it doesn't really need a picture. I've got it mounted on a bike that's mid-build right now and it has some play where it bolts to the derailleur hanger, so I think I'm going to need to harvest another washer or something from the LePree.
This fits under the saying "beware of geeks bearing gifts."

I gave the LePree to Andy awhile back as gratitude for hauling my bike from Portland to Cambria for Eroica California. He installed it sometime later on an old Raleigh, and within 2-3 miles the spring broke.
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Old 06-24-20, 03:50 PM
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Originally Posted by gugie
I gave the LePree to Andy awhile back as gratitude for hauling my bike from Portland to Cambria for Eroica California. He installed it sometime later on an old Raleigh, and within 2-3 miles the spring broke.
Same bike I just put the XC on. I'm hoping to make it at least 10 miles this time! The LePree was worth every penny I paid for it.
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Old 06-24-20, 08:22 PM
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I have a 3 pulley XC that I think is the cat's pyjamas.

Suntour XC by Dave The Golden Boy, on Flickr

Suntour XC by Dave The Golden Boy, on Flickr
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Old 06-29-20, 02:34 AM
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Originally Posted by The Golden Boy
I have a 3 pulley XC that I think is the cat's pyjamas.
Mine didn't polish up quite as well as yours, but it does look pretty nice.

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