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Suntour SL reverse-pull FD?

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Suntour SL reverse-pull FD?

Old 09-17-22, 03:54 PM
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Suntour SL reverse-pull FD?

Anyone have experience with one of these? Specifically if it can handle a triple (26/42/46)? Looking to 'upgrade' my Peugeot TH-8 tandem...

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Old 09-17-22, 06:14 PM
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I don't think I have any direct experience with that model but the cage looks long enough and it looks as though you should be able to get enough swing out of it. If you own it, I would just put it on and see. In my experience, what works on one bike might not on another. I do know a Suntour reverse pull (which, I can't remember but most probably very similar) was effective for me on an early Santana tandem but I do believe the chain rings were larger and I suppose that could make a difference. My bet is that it "can handle" the triple but, again my experience is, shifting to a granny on a tandem generally takes a lot more planning and good timing than doing so on a single.
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Old 09-17-22, 07:12 PM
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Originally Posted by L134 View Post
My bet is that it "can handle" the triple but, again my experience is, shifting to a granny on a tandem generally takes a lot more planning and good timing than doing so on a single.
That's interesting- any idea why that is?
I don't currently own that FD, but another member is selling one and I'm very tempted (not least because the package includes a V-GT RD and some bar-ends). I really like DT shifters on my single(s), but I'm discovering that I don't like them so much on the tandem and I think I'd feel better with bar-ends.
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Old 09-18-22, 05:48 AM
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Originally Posted by ehcoplex View Post
That's interesting- any idea why that is?
I don't currently own that FD, but another member is selling one and I'm very tempted (not least because the package includes a V-GT RD and some bar-ends). I really like DT shifters on my single(s), but I'm discovering that I don't like them so much on the tandem and I think I'd feel better with bar-ends.
As to whether it will work might be a trial and error thing.

Other than cruising around in the store, oh yeah it was crazy, I have l experience no with tandems, but I suspect what he means is, it could upset the rhythm of the stoker if it’s done quickly and I suspect it is simply much easier to drip the chain off.

I briefly worked in a shop that had been a Staples so it was bigger than most shop and we had this goofy little test track. So of course when the store was empty and we were bored we did a lot of test riding, and rode through the store too. It was trip piloting the long Jamis tandem through that place.
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Old 09-18-22, 06:03 AM
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Originally Posted by L134 View Post
My bet is that it "can handle" the triple but, again my experience is, shifting to a granny on a tandem generally takes a lot more planning and good timing than doing so on a single.
Originally Posted by ehcoplex View Post
That's interesting- any idea why that is?
The longer cable run to the front derailleur (assuming it is mounted on the stoker seat tube) has more friction and stretch than on a single. The reverse-pull of the SL derailleur should help with this, as shifting to the granny does not depend on the derailleur's spring, but can be aggressively shifted by the rider.
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Old 09-18-22, 06:12 AM
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I have the SL on one of my bikes (not a tandem though) and it shifts very well as do most SunTour changers. One thing to bear in mind is the cage is alloy and it wears faster than the one on the Comp-V, which shifts equally well.
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Old 09-18-22, 06:15 AM
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Originally Posted by JohnDThompson View Post
The longer cable run to the front derailleur (assuming it is mounted on the stoker seat tube) has more friction and stretch than on a single. The reverse-pull of the SL derailleur should help with this, as shifting to the granny does not depend on the derailleur's spring, but can be aggressively shifted by the rider.
Makes sense!
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Old 09-18-22, 08:48 AM
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Originally Posted by JohnDThompson View Post
The longer cable run to the front derailleur (assuming it is mounted on the stoker seat tube) has more friction and stretch than on a single. The reverse-pull of the SL derailleur should help with this, as shifting to the granny does not depend on the derailleur's spring, but can be aggressively shifted by the rider.
ehcoplex ,

That and, I think, even on a single one wants to let up on the pedal stroke when making the shift to reduce tension in the chain making it easier for it to release from the middle chain ring. This is a timing thing so the captain and stoker need to be in sync which makes the timing more difficult on a tandem. You let up but your stoker doesn't at the same moment and there may be no derailleur that can handle that. The other related timing issue with the tandem is that, due to weight, you lose momentum on the hill much more quickly so (unless you are an experienced, practiced tandem team with great sync) making your shift before you lose too much momentum and cadence makes it easier to reduce the tension in the chain enough to complete the shift. Wait too long to make the shift to where you have to apply pressure just to keep going and there may be no derailleur that can handle it. Anticipating the need for the shift and making it probably before you would on a single becomes more critical. The teamwork, to me, is part of the reward of tandeming. If your styles are closely matched, this stuff probably comes more easily than if they are not. Practice.

Having said all this, if your current derailleur will drop the chain to the granny without trouble if you are riding around in a level parking lot or while the bike is on a stand but won't when you need it, it is probably because you and your stoker aren't in full sync and/or you waited to long to attempt the shift. I think the reverse pull can help overcome some of this but if you are wildly out of sync, probably not a lot.
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Old 09-18-22, 09:30 AM
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Originally Posted by L134 View Post
...That and, I think, even on a single one wants to let up on the pedal stroke when making the shift to reduce tension in the chain making it easier for it to release from the middle chain ring. This is a timing thing so the captain and stoker need to be in sync which makes the timing more difficult on a tandem....
+1. Based on my tandem experience, this is more critical that the cable issue, though both are factors.

Regarding the ability to handle a triple, my tandem was a 1985 Santana Elan, equipped with a Compe-V front derailleur. This is from the same era as the SL, so the latter likely has the same travel and can handle the lateral throw, provided the spindle length doesn't skew the chainline too far from the nominal cage position.

However, the capacity of the SL is stated as 15T. You are asking it to handle 20T, so you'll have to be careful with crosschaining and will not have as many useful combinations as with a wide range front derailleur.

Also, as noted, the SL cage is aluminum. Besides the higher wear rate, aluminum is not as stiff as steel. To compensate you have to make it thicker but this mitigates the weight savings. The cage may not be stiff enough to shift under some of the heavy load situations experienced on tandems. This is where the previously mentioned co-ordination between the captain and stoker can be critical.

The bottom line is that you can likely make it work but the concessions in gearing and performance may not be acceptable.

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Old 09-18-22, 01:32 PM
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The FD shifting issue happens more-or-less the same when I test-ride around on the tandem alone, so it's not a sync issue- or at least that's not the primary issue....! The FD is one of the SLJ models (earlier, I think...) with the cable clamp at the front, so the short run of housing from under the BB has to contort a bit to get up and around the seat-post, so I think that may be the source of the issue.

The aluminum cage and stated limited range of the SL gives me pause.... and I realized I have a set of Cyclone MKII derailleurs that were intended for another bike that I may just try on the tandem (if the 'endless band' clamp on the FD will tighten enough...). It's not a reverse pull, but maybe it'll work.
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Old 09-18-22, 03:47 PM
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I've used a 1st gen Cyclone FD, an early Compe-V, and a Vx on a 45-42-28 crankset. I had to adjust all of them pretty carefully to prevent them from hitting both the chain and the crank, as Sheldon pointed out somewhere. The Compe-V is, as you probably know, top-normal. I've been using it for a few hundred miles, and I sort of like it; in any case, I have no plans to go back at this point. You can always try your SL, and get a steel top-normal FD if you like it.
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Old 09-18-22, 06:08 PM
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Originally Posted by philbob57 View Post
I've used a 1st gen Cyclone FD, an early Compe-V, and a Vx on a 45-42-28 crankset. I had to adjust all of them pretty carefully to prevent them from hitting both the chain and the crank, as Sheldon pointed out somewhere. The Compe-V is, as you probably know, top-normal. I've been using it for a few hundred miles, and I sort of like it; in any case, I have no plans to go back at this point. You can always try your SL, and get a steel top-normal FD if you like it.
45-42-28 is a great ringset combo.

I have used high-normal SunTour front derailleurs with triples, with no problem, other than remembering which bike I was riding.

When I worked at a Peugeot-Nishiki dealership, the boss really liked the SunTour fronts, because it made gear changing easier to explain to novice customers -- "pull back both levers for low, push both forward for high."
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Old 09-18-22, 07:03 PM
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Originally Posted by John E View Post
45-42-28 is a great ringset combo.
"
45-42-30 on my PX-10 and I love it. Haven't spent enough time on the tandem with 46-42-26 to know how it compares, but seem pretty close.... I need to figure out what all the cogs on the cassette are and plug it into the gear calculator and see what the spread looks like...

Tried the Cyclone FD for fit on the seat-tube, and while it will clamp securely I realized it doesn't have a built-in cable-housing stop.. So if I want to try it I'll have to get some sort of clamp-on stop or under-BB cable guide.... I can't really tell from the photos if an SL FD has a built in cable-housing stop- anyone know?
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Old 09-19-22, 05:24 AM
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Originally Posted by ehcoplex View Post
Tried the Cyclone FD for fit on the seat-tube, and while it will clamp securely I realized it doesn't have a built-in cable-housing stop.. So if I want to try it I'll have to get some sort of clamp-on stop or under-BB cable guide.... I can't really tell from the photos if an SL FD has a built in cable-housing stop- anyone know?
If I recall correctly, the SL does have a built in cable housing stop.

But, no stop ... no problem. Just route your cable housing under the BB shell, cut it off after it has completed the bend toward the front derailleur, and let the upper end hang. Works like a champ on my 1959 Capo, which has a stop-less Campag. front in place of the OEM Campag. pushrod pillbox. (Think ca. 1970 Simplex, but angled slightly upward and aluminum-cased, both huge improvements.)

1959 Capo with Nervar Star crank and Campag. 980 derailleur upgrades and new Brooks Pro saddle.

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Old 09-19-22, 05:36 AM
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Originally Posted by John E View Post
If I recall correctly, the SL does have a built in cable housing stop.

But, no stop ... no problem. Just route your cable housing under the BB shell, cut it off after it has completed the bend toward the front derailleur, and let the upper end hang. Works like a champ on my 1959 Capo, which has a stop-less Campag. front in place of the OEM Campag. pushrod pillbox.
Ah yes, of course. I was thinking the housing needed to ‘push’ against something for the DR to work, but of course it doesn’t.
Head lugs on that Capo are beautiful!
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Old 09-19-22, 06:33 AM
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For completeness yes there is a cable stop on the SL. Its part of the movable lever, and the cable end is held fixed.
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Old 09-19-22, 06:46 AM
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Originally Posted by ehcoplex View Post
... Head lugs on that Capo are beautiful!
Thank you -- Otto Cap used these lugs for more than a decade (1952 model shown here, with Capo brand derailleurs).

1952 Capo Sieger with Capo brand derailleurs and very-rare-for-Capo through-frame cable routing.

Adolf Christian rode a similar Capo Sieger to his 3rd place finish in the 1957 Tour de France.
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Old 09-19-22, 09:15 AM
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Originally Posted by markk900 View Post
For completeness yes there is a cable stop on the SL. Its part of the movable lever, and the cable end is held fixed.
Thanks!
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Old 09-19-22, 05:40 PM
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Yes, I have this model of FD on a bike. It started off working well with a triple (30-39-50), but recently it has become rather ineffectual in moving the chain from 39 to 50, though it manages it on the second or third attempt, or sometimes even on the first. (From 30 to 39 presents no problem. And once the chain is on the 50, it's happy there: it never threatens to fall back onto the 39.) Of course I avoid cross-chaining, though it's very likely that I'm ignorantly making some similarly stupid mistake.
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