JeanLucPicard

Hi

I need a longer cage derailleur for my old bike. The old one is a Suntour AR, and to keep the bike more original I thought I'll try to find a other Suntour derailleur.

I'm wondering those it really matter if I get a low end Suntour derailleur or higher end Suntour derailleur? Since it is friction shifting, the only benefits of a higher end model would be lightness and noise? Is there anything else?

Thanks,

greg3rd48 

I have Suntour ARX RD/FD on two of my '84 Fuji's and they work very smoothly. I just mailed away my last AR RD but if you need an AR FD you are welcome to it.

The Golden Boy 

First up... why do you need a longer cage derailleur?


Second up... why go with a cheap derailleur when you can get a good one for not much more?

jimmuller 

I have a Suntour RD labeled "ar II" you are welcome to. It's not a super-long cage, more like medium length. It cam from a Fuji I am planning to give to someone. I put a triple crank on it and the ar's cage won't quite handle the range, but would be fine for a more typical double.

repechage

I cannot tell if a front or rear dérailleur is required with greater capacity yet.

If you note the ratios you have or want the hive mind here can assimilate it...

mstateglfr 

SunTour long cage RDs had different capacities. And it isn't as simple as the nicer ones had more capacity. So there is a good bit of difference in performance between RDs since they vary in capability.

Phil_gretz

If you'd be kind enough to describe your crankset (# of chainrings, # of teeth on each ring) and rear cogset (# of cogs, # of teeth on smallest and largest cog), then we can give specific advice. To answer your question, all SunTour derailleurs will function well in friction mode.

We each have our favorites. VxGT is really nice, as is VGT-Luxe. Cyclone II rear derailleurs are light and shift well. Do a little research about "capacity" and "chain wrap" values, use your tooth counts to calculate what you'll need, then look at candidate derailleurs on this web site:

SunTour derailleurs

You'll find that there are many models that will work fine for you. Whatever model you choose, it'll be available on eBay. Good luck. PG

SoreFeet

No it doesn't really matter at all. The only thing that matters is the amount of teeth and ring size you are using. Swapping out the derailleur should be relatively painless procedure.

The old Deore or even Exage are good substitute for the Suntour.

JeanLucPicard

Well the old freewheel was old and worn(chain skipping). Not sure of the size of that one but it was very small(13-21t maybe).

So the new one I got is much larger(I thought why not, for those super steep hills). It is : 14.18.22.28.34.
I need to check the crankset, no idea what teeth count that could be(suntour as well).
I didn't really check if it would suit the bike, but I had a idea that the 34 cog would be too big, but I thought I'd just get a new derailleur anyway(current one is a big worn). 34 is the only cog that is too big.

The reason I ask is I can see on ebay some long cage derailliuers like Suntour cyclone, which is about $60~ new or like a Suntour GT for about $20~ in excellent condition, but if there isn't much of a difference I may as well go with the GT or a different brand.

Bianchigirll 

That is quite the switch. Did you check the chain? Does it simply have stiff links or is it stretched? If the freewheel (FW) is worn enough for the chain to skip over it the chain is most likely stretched beyond use too.

Either way you will need a longer chain and depending on you chain wheels you may have trouble getting that to 14-34 to work.

jimmuller 

What BG said. All of it.

Plus, the gaps on that FW are so large you wil most certainly wish you had ratios in between them on occasion. That places high value on your selection of chain rings to get a decent crossover pattern. For that FW I'd suggest half-step.

JeanLucPicard

I've changed the chain as well so all new fw and chain.

Everything seems fine other than the derailleur hitting the biggest cog.

I wasn't looking to spend much money so that's why I thought maybe just get a low end used suntour derailleur seeing as it doesn't make much of a difference I suppose.
I live in Australia, if anyone with spare derailleur(I think mine is medium, sorry jimmuller and greg) I don't mind buying it and paying for shipping costs from America.

The Golden Boy 

It's not the cage length you're interested in-

The cage just takes up/lets out chain slack.

If your upper pulley is hitting the FW cog- I was using a 1990-ish XC Pro with either a 32 or 34- and it worked great.

Otherwise, something like a Sachs/Huret DuoPar, Suntour Mountech II, Suntour LeTech. I would also imagine the Shimano MTB derailleurs would be swell as well (XT/Deore/LX)

JeanLucPicard

The cage length isn't the problem?
What causes the largest cog to hit the pulley?

Thanks,

jimmuller 

Look at it and think about it for a minute. The cage length determines how much chain it can take up or release. TGB already said that.

The reason the largest cog hits the guide pulley (or the pulley hits the largest cog) is because it it too close, which is to say the pulley sits too high. I don't recall now what RD you ended up using, but here is the thing. If the guide pulley is too far away from the cogs it won't shift promptly. If it is too close, something hits. The classic problem with RDs, the ultimate question of life, the universe, and everything, is how to get that distance just right. The inner cogs are always bigger than the outer cogs, so on the ideal RD the pulley would move downward as it moves inward, upward as it moves outward, to keep the pulley-cog distance just right.

Back in the 1960's Suntour invented the slant parallelogram RD to do just that. Ever since their patent ran out in the 1980's just about every new RD has used this design.

Another technique is to have the guide pulley be positioned behind the cage pivot so that as the tension pulley moves backwards or forwards the guide pulley moves up or down. The Shimano Crane GS and the Campagnolo Rally did this. The problem with this design is that chain is taken up or released not only by a rear shift to a different size cog but also by a front shift. If the pulley is positioned ideally for one chain ring it won't be ideal for the other though it may still be acceptable. One good thing about this design is that you can reposition the guide pulley vertically by changing the chain length, as long as it can still handle the extreme combinations (big-big or little-little). Some RDs could even us both techniques.

But the real question is, after all that, exactly what distance was the RD designed for? It is still possible that the cogs are bigger than the designed distance, or that the difference between the largest and smallest distances is too great. The overall size of the RD and the length of the mounting bracket determine how high or low the pulley sits for any give cog. If you use a FW with a very very large cog you must use a RD which allows the guide pulley to move that far down. Most were not intended to accommodate a huge big cog. You may be able to fix it by finding a longer hanger. I'm not an expert on what is available or what different companies made.

Or to put it an other way, if you bang your head on the door frame then either you are too tall for the door or the door is too short. End of story.

Phil_gretz

So, JeanLuc, you must ask yourself, "how would a mountain bike be equipped to handle this large an inner cog?" The answer will lead your thinking...