Possible to strengthen or replace body spring Suntour rear mech?

Hi there people.

I have an old Suntour Cyclone rear derailleur that doesn't want to return to the two highest (smallest) cogs on my 8 of 9 speed cassette. I think it might be because the return spring inside the body of the rear derailleur is a bit weak. Is there anyway to either make that spring stronger by bending it or by replacing it with a similar spring from another Suntour rear derailleur? This is the normal derailleur with just one guide wheel and one jockey wheel. It is NOT the triple pulley version.

Thanks and cheers

On Friday, July 5, 2019 at 1:54:00 PM UTC-7, Sir Ridesalot wrote:
Hi there people.

I have an old Suntour Cyclone rear derailleur that doesn't want to return to the two highest (smallest) cogs on my 8 of 9 speed cassette. I think it might be because the return spring inside the body of the rear derailleur is a bit weak. Is there anyway to either make that spring stronger by bending it or by replacing it with a similar spring from another Suntour rear derailleur? This is the normal derailleur with just one guide wheel and one jockey wheel. It is NOT the triple pulley version.

Thanks and cheers

Unless the spring actually has broken the strength should not be effected over time. In most cases where the rear derailleur won't return it is the cables that are the cause.

To test this simply disconnect the cable and pedal the bike and observe whether it shifts into the top gear.

On 7/5/2019 4:53 PM, Sir Ridesalot wrote:
Hi there people.

I have an old Suntour Cyclone rear derailleur that doesn't want to return to the two highest (smallest) cogs on my 8 of 9 speed cassette. I think it might be because the return spring inside the body of the rear derailleur is a bit weak. Is there anyway to either make that spring stronger by bending it or by replacing it with a similar spring from another Suntour rear derailleur? This is the normal derailleur with just one guide wheel and one jockey wheel. It is NOT the triple pulley version.

Just guessing, but my short answer is: I doubt it.

I think it would be pretty unusual for the spring to get weak unless it
was in the process of breaking - that is, unless a crack as begun in the
spring wire.

I assume you've already looked at other possible causes. But if the
shift cable is completely detached, does it make that shift? That would
indicate some cable problem. Are the pivots needing lubrication? Is
there corrosion limiting motion, or some oddball metal to metal
interference? Are the limiting screws original, in good shape and
operating properly? I'd suspect those sorts of things before the spring
itself.

IIRC, even getting access to that spring would require disassembling the
parallelogram arms. I'd think that would be difficult.

I'll point out that some things about springs are a bit
counter-intuitive. If you wanted to fabricate a complete new one,
thicker steel wire would make it stiffer, all other things being equal.
But lots of people don't know that springs with _fewer_ coils are
stiffer - again, other things being equal. So are springs with smaller
diameter (although I don't see how you could reduce that one's
diameter). I suppose you cold try to straighten out one coil of the
existing spring and re-form it into the same sort of end that the
existing spring has, so you ended up with a spring with one less coil.

But IME customizing springs is frustratingly difficult and fiddly. I'd
hope the problem lies elsewhere, and work hard to check everything else.

--
- Frank Krygowski

On 7/5/2019 3:53 PM, Sir Ridesalot wrote:
Hi there people.

I have an old Suntour Cyclone rear derailleur that doesn't want to return to the two highest (smallest) cogs on my 8 of 9 speed cassette. I think it might be because the return spring inside the body of the rear derailleur is a bit weak. Is there anyway to either make that spring stronger by bending it or by replacing it with a similar spring from another Suntour rear derailleur? This is the normal derailleur with just one guide wheel and one jockey wheel. It is NOT the triple pulley version.

Thanks and cheers


No.
Your body return spring hasn't changed.

Undo a roller bolt, slip the chain out and disconnect the
gear wire. Remove th echanger from the bike.

Look closely in a good light for dings/scuffs on the outside
edges which indicate how many times and how hard it's been
smacked. Minor deformation of the parallelogram can
sometimes be freed by carefully flexing it back using padded
vise jaws. Sometimes not.

Look closely at the pivots from various angles to see how
much crud and dirt is lodged in them. A good cleaning and
oiling usually helps even smacked bodies- they aren't made
to exceptional tolerances.

Product plug- Rock-N-Roll is really great for this sort of
problem. It goes into tight spaces amazingly well.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Friday, July 5, 2019 at 9:30:13 PM UTC-4, AMuzi wrote:
On 7/5/2019 3:53 PM, Sir Ridesalot wrote:
Hi there people.

I have an old Suntour Cyclone rear derailleur that doesn't want to return to the two highest (smallest) cogs on my 8 of 9 speed cassette. I think it might be because the return spring inside the body of the rear derailleur is a bit weak. Is there anyway to either make that spring stronger by bending it or by replacing it with a similar spring from another Suntour rear derailleur? This is the normal derailleur with just one guide wheel and one jockey wheel. It is NOT the triple pulley version.

Thanks and cheers


No.
Your body return spring hasn't changed.

Undo a roller bolt, slip the chain out and disconnect the
gear wire. Remove th echanger from the bike.

Look closely in a good light for dings/scuffs on the outside
edges which indicate how many times and how hard it's been
smacked. Minor deformation of the parallelogram can
sometimes be freed by carefully flexing it back using padded
vise jaws. Sometimes not.

Look closely at the pivots from various angles to see how
much crud and dirt is lodged in them. A good cleaning and
oiling usually helps even smacked bodies- they aren't made
to exceptional tolerances.

Product plug- Rock-N-Roll is really great for this sort of
problem. It goes into tight spaces amazingly well.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

Thanks again Andrew. I'll give all that a try.

Cheers

On Friday, July 5, 2019 at 9:30:13 PM UTC-4, AMuzi wrote:
On 7/5/2019 3:53 PM, Sir Ridesalot wrote:
Hi there people.

I have an old Suntour Cyclone rear derailleur that doesn't want to return to the two highest (smallest) cogs on my 8 of 9 speed cassette. I think it might be because the return spring inside the body of the rear derailleur is a bit weak. Is there anyway to either make that spring stronger by bending it or by replacing it with a similar spring from another Suntour rear derailleur? This is the normal derailleur with just one guide wheel and one jockey wheel. It is NOT the triple pulley version.

Thanks and cheers


No.
Your body return spring hasn't changed.

Undo a roller bolt, slip the chain out and disconnect the
gear wire. Remove th echanger from the bike.

Look closely in a good light for dings/scuffs on the outside
edges which indicate how many times and how hard it's been
smacked. Minor deformation of the parallelogram can
sometimes be freed by carefully flexing it back using padded
vise jaws. Sometimes not.

Look closely at the pivots from various angles to see how
much crud and dirt is lodged in them. A good cleaning and
oiling usually helps even smacked bodies- they aren't made
to exceptional tolerances.

Product plug- Rock-N-Roll is really great for this sort of
problem. It goes into tight spaces amazingly well.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

Update.

YES the spring in this Suntour Cyclone rear derailleur is DEFINITELY weaker than when new. Compare to all other derailleurs I have here that return spring inside the body is indeed VERY weak. Fortunately I just got a NOS rear Cyclone derailleur body with just the outer part of the cage and missing the pulleys,, cable pinch bolt assembly, the low gear limiting bolt and the body to frame mounting bolt. I'll take all those needed parts from my old Suntour Cyclone derailleur and put them on this new body. Now I'll be able to shift into ALL of my high gears.

Cheers

On 7/22/2019 1:37 PM, Sir Ridesalot wrote:
On Friday, July 5, 2019 at 9:30:13 PM UTC-4, AMuzi wrote:
On 7/5/2019 3:53 PM, Sir Ridesalot wrote:
Hi there people.

I have an old Suntour Cyclone rear derailleur that doesn't want to return to the two highest (smallest) cogs on my 8 of 9 speed cassette. I think it might be because the return spring inside the body of the rear derailleur is a bit weak. Is there anyway to either make that spring stronger by bending it or by replacing it with a similar spring from another Suntour rear derailleur? This is the normal derailleur with just one guide wheel and one jockey wheel. It is NOT the triple pulley version.

Thanks and cheers


No.
Your body return spring hasn't changed.

Undo a roller bolt, slip the chain out and disconnect the
gear wire. Remove th echanger from the bike.

Look closely in a good light for dings/scuffs on the outside
edges which indicate how many times and how hard it's been
smacked. Minor deformation of the parallelogram can
sometimes be freed by carefully flexing it back using padded
vise jaws. Sometimes not.

Look closely at the pivots from various angles to see how
much crud and dirt is lodged in them. A good cleaning and
oiling usually helps even smacked bodies- they aren't made
to exceptional tolerances.

Product plug- Rock-N-Roll is really great for this sort of
problem. It goes into tight spaces amazingly well.

Update.

YES the spring in this Suntour Cyclone rear derailleur is DEFINITELY weaker than when new. Compare to all other derailleurs I have here that return spring inside the body is indeed VERY weak. Fortunately I just got a NOS rear Cyclone derailleur body with just the outer part of the cage and missing the pulleys,, cable pinch bolt assembly, the low gear limiting bolt and the body to frame mounting bolt. I'll take all those needed parts from my old Suntour Cyclone derailleur and put them on this new body. Now I'll be able to shift into ALL of my high gears.


The lower pivot It may well be goopy or rusted inside. It
may have been disassembled then re set with the spring in a
less favorable position (six choices there) but springs do
not 'weaken'. Your symptom is real or you would not have
reported it. Twice. The diagnosis isn't weakened spring.

https://phys.org/news/2015-02-law.html

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Monday, July 22, 2019 at 5:39:25 PM UTC-4, AMuzi wrote:
On 7/22/2019 1:37 PM, Sir Ridesalot wrote:
On Friday, July 5, 2019 at 9:30:13 PM UTC-4, AMuzi wrote:
On 7/5/2019 3:53 PM, Sir Ridesalot wrote:
Hi there people.

I have an old Suntour Cyclone rear derailleur that doesn't want to return to the two highest (smallest) cogs on my 8 of 9 speed cassette. I think it might be because the return spring inside the body of the rear derailleur is a bit weak. Is there anyway to either make that spring stronger by bending it or by replacing it with a similar spring from another Suntour rear derailleur? This is the normal derailleur with just one guide wheel and one jockey wheel. It is NOT the triple pulley version.

Thanks and cheers


No.
Your body return spring hasn't changed.

Undo a roller bolt, slip the chain out and disconnect the
gear wire. Remove th echanger from the bike.

Look closely in a good light for dings/scuffs on the outside
edges which indicate how many times and how hard it's been
smacked. Minor deformation of the parallelogram can
sometimes be freed by carefully flexing it back using padded
vise jaws. Sometimes not.

Look closely at the pivots from various angles to see how
much crud and dirt is lodged in them. A good cleaning and
oiling usually helps even smacked bodies- they aren't made
to exceptional tolerances.

Product plug- Rock-N-Roll is really great for this sort of
problem. It goes into tight spaces amazingly well.

Update.

YES the spring in this Suntour Cyclone rear derailleur is DEFINITELY weaker than when new. Compare to all other derailleurs I have here that return spring inside the body is indeed VERY weak. Fortunately I just got a NOS rear Cyclone derailleur body with just the outer part of the cage and missing the pulleys,, cable pinch bolt assembly, the low gear limiting bolt and the body to frame mounting bolt. I'll take all those needed parts from my old Suntour Cyclone derailleur and put them on this new body. Now I'll be able to shift into ALL of my high gears.


The lower pivot It may well be goopy or rusted inside. It
may have been disassembled then re set with the spring in a
less favorable position (six choices there) but springs do
not 'weaken'. Your symptom is real or you would not have
reported it. Twice. The diagnosis isn't weakened spring.

https://phys.org/news/2015-02-law.html

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

Ah, but it's NOT the lower pivot of the cage that holds the idler and jockey wheels that's the problem, it's the spring inside the body that controls the side to side movement of the derailleur from high gear to low gear and back to high gear that's weak. It takes hardly any finger pressure to move the derailleur but on all my other derailleurs including the NOS Cyclone body it takes a lot of pressure to move that body.

I only did the update because it's so unusual to have such a weak spring there. I wonder if perhaps a bit of the spring has broken off at some point in time? A weak spring does show why this boy can't return itself to the high gear position though. Everything is adjusted properly, it's been tried with the cable disconnected and that spring is definitely far weaker than any other I've ever seen.

Once I get the needed parts swapped over to the NOS one I should send you this old body so you can see for yourself and perhaps tell me why it's so weak. It's been thoroughly cleaned and the movement is free but just very weak ie a very light touch is all it takes to move the body.

Cheers

Cheers

On 7/22/2019 6:36 PM, Sir Ridesalot wrote:
On Monday, July 22, 2019 at 5:39:25 PM UTC-4, AMuzi wrote:
On 7/22/2019 1:37 PM, Sir Ridesalot wrote:
On Friday, July 5, 2019 at 9:30:13 PM UTC-4, AMuzi wrote:
On 7/5/2019 3:53 PM, Sir Ridesalot wrote:
Hi there people.

I have an old Suntour Cyclone rear derailleur that doesn't want to return to the two highest (smallest) cogs on my 8 of 9 speed cassette. I think it might be because the return spring inside the body of the rear derailleur is a bit weak. Is there anyway to either make that spring stronger by bending it or by replacing it with a similar spring from another Suntour rear derailleur? This is the normal derailleur with just one guide wheel and one jockey wheel. It is NOT the triple pulley version.

Thanks and cheers


No.
Your body return spring hasn't changed.

Undo a roller bolt, slip the chain out and disconnect the
gear wire. Remove th echanger from the bike.

Look closely in a good light for dings/scuffs on the outside
edges which indicate how many times and how hard it's been
smacked. Minor deformation of the parallelogram can
sometimes be freed by carefully flexing it back using padded
vise jaws. Sometimes not.

Look closely at the pivots from various angles to see how
much crud and dirt is lodged in them. A good cleaning and
oiling usually helps even smacked bodies- they aren't made
to exceptional tolerances.

Product plug- Rock-N-Roll is really great for this sort of
problem. It goes into tight spaces amazingly well.

Update.

YES the spring in this Suntour Cyclone rear derailleur is DEFINITELY weaker than when new. Compare to all other derailleurs I have here that return spring inside the body is indeed VERY weak. Fortunately I just got a NOS rear Cyclone derailleur body with just the outer part of the cage and missing the pulleys,, cable pinch bolt assembly, the low gear limiting bolt and the body to frame mounting bolt. I'll take all those needed parts from my old Suntour Cyclone derailleur and put them on this new body. Now I'll be able to shift into ALL of my high gears.


The lower pivot It may well be goopy or rusted inside. It
may have been disassembled then re set with the spring in a
less favorable position (six choices there) but springs do
not 'weaken'. Your symptom is real or you would not have
reported it. Twice. The diagnosis isn't weakened spring.

https://phys.org/news/2015-02-law.html

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

Ah, but it's NOT the lower pivot of the cage that holds the idler and jockey wheels that's the problem, it's the spring inside the body that controls the side to side movement of the derailleur from high gear to low gear and back to high gear that's weak. It takes hardly any finger pressure to move the derailleur but on all my other derailleurs including the NOS Cyclone body it takes a lot of pressure to move that body.

I only did the update because it's so unusual to have such a weak spring there. I wonder if perhaps a bit of the spring has broken off at some point in time? A weak spring does show why this boy can't return itself to the high gear position though. Everything is adjusted properly, it's been tried with the cable disconnected and that spring is definitely far weaker than any other I've ever seen.

Once I get the needed parts swapped over to the NOS one I should send you this old body so you can see for yourself and perhaps tell me why it's so weak. It's been thoroughly cleaned and the movement is free but just very weak ie a very light touch is all it takes to move the body.

Cheers

Cheers


Oh, sorry I missed that.

Same principles apply to any steel spring but a broken
spring or damaged body are other matters entirely.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Monday, July 22, 2019 at 7:36:10 PM UTC-4, Sir Ridesalot wrote:

Ah, but it's NOT the lower pivot of the cage that holds the idler and jockey wheels that's the problem, it's the spring inside the body that controls the side to side movement of the derailleur from high gear to low gear and back to high gear that's weak. It takes hardly any finger pressure to move the derailleur but on all my other derailleurs including the NOS Cyclone body it takes a lot of pressure to move that body.

I only did the update because it's so unusual to have such a weak spring there. I wonder if perhaps a bit of the spring has broken off at some point in time? A weak spring does show why this boy can't return itself to the high gear position though. Everything is adjusted properly, it's been tried with the cable disconnected and that spring is definitely far weaker than any other I've ever seen.

Once I get the needed parts swapped over to the NOS one I should send you this old body so you can see for yourself and perhaps tell me why it's so weak. It's been thoroughly cleaned and the movement is free but just very weak ie a very light touch is all it takes to move the body.

I'd be interested in Andrew's diagnosis. As I said, the only way I can see that
spring getting weaker is if it's partially broken at some point or other.

I can remember reading here, decades ago, someone recommended always shifting
both derailleurs to the small rings. Their idea was to reduce force on the
springs so they would last longer. I know I thought "That's nonsense" and IIRC
that was the general consensus, too.

- Frank Krygowski