semroc

Hello all. Just put an old suntour 6 speed freewheel on my Rossin. It's a 14-34. I put my suntour v gt luxe on there, and it won't shift onto the lowest gear. I've tried backing out the adjuster screw a plethora of times. The one that says L. The derailleur hanger is straight. I put a gauge on it. I've used this derailleur before on a 28 freewheel, and it worked fine. Disraeli Gears list this derailleur as being able to handle 34 teeth. Any suggestions? I put a new cable on too. Thanks all.

L134 

Is the cable tight with chain on small cog?

Bill Kapaun

Is the chain long enough?

semroc

Yes the cable is tight, when in the small cog. Chain might not be long enough. I'll check after work. Thanks I appreciate the help. Could this be a freewheel that needs spacers to push it out more?

JohnDThompson 

If, as @Bill Kapaun suggests, the chain is long enough, perhaps the "B-screw" needs to be adjusted to give the upper pulley more clearance for the 34T sprocket. Failing that, check the hanger alignment. A V-GT Luxe unit should be able to handle a 34T sprocket.

ShannonM

Does a VGT have a B-screw? My 1980 Superbe doesn't. Does the derailleur hit the cog with no chain and no cable, moving the derailleur by hand? If it does, you're probably hosed.

Different dropouts had different derailleur hanger lengths. I know that Suntours were longer than Campys. That same Superbe is max rated at a 23T, but I'm running it on a 14-26, and I'm pretty sure a 28 would clear the top pulley. That's on a Suntour dropout on a Fuji frame. I'd guess that your Rossin has Campys, but there were several models and I don't know if they all had the same hangers. I seem to think I remember that there was something like a "racing" version with a short hanger for faster shifting on small clusters, but that might be false memory. (If such a thing existed, I'd be unsurprised to find one on a Rossin... they did have a "make things weird for theoretical gains that would be marginal even if real" thing going on back when... part of what makes them cool bikes.)

If your dropouts have adjustment screws, try removing them and running the wheel all the way back. Often, this will get you that last bit o' clearance.

--Shannon

semroc

Thanks for the reply ShannonM. I have messed with the b screw. Backed it all the way out, halfway in, didn't help. The rear wheel is all the way back in the dropouts.

70sSanO

Here’s the deal… you need to screw the B screw all the way in. And if that doesn’t work you need to get a longer screw from a hardware store. I’m not sure what thread Suntour used so take the screw with you.

I’ve had Shimano RD’s rated for 34t max cog and still needed a longer B screw when the B spring got weak. I’ve even had to resort to actually adding a nut on the end of the B screw so it could still contact the B screw stop on the hanger.

John

Kovkov

I can confirm that. I have one that does.

ShannonM

I looked at the V-GT Luxe pages on both velo-base and Disraeli Gears. None of the pictures look like they had a B-screw. I was wondering about this since, as I said, my Superbe doesn't have one.

If memory serves, and it quite possibly doesn't, didn't Shimano invent the B-screw for the 1st generation SIS groups? It was added to fine-tune the pulley-to-big-cog gap... I remember there being a precise measurement for it in the manual. (There were no instructions as to how one might go about actually making this measurement in an accurate and repeatable way with bike shop tools, but, hey, they had a number for it!) I even seem to remember articles about how one could use this new adjusting screw to get an extra couple of teeth bigger cog out of your short-cage rear derailleur, even though that's not what it was for.

If, as the pictures seem to show, the V-GT doesn't have a B-screw, then wherever the derailleur sits on the hanger is where it's gonna stay, 'cuz there's no way to change it. If where that is on the OPs Rossin won't clear a 34T cog, then they're (not) screwed.

If I'm wrong, and it does, then everything you said is exactly what the OP needs to do.

--Shannon

semroc

Hello all. So I put my suntour cyclone gt on my bike just to check it out, it goes into the 34 no problem. I'll keep working on the v gt luxe. I'll try the longer b screw. But I'll keep the cyclone on for now. Much appreciated for your time and effort.

sd5782 

On one of my bikes and the Vgt, the pulley cage was shaped such that it interfered with the big sprocket. A VXgt with a different shaped cage worked with that specific hanger/sprocket combo.

JohnDThompson 

FWIW, I've never seen a V-GT Luxe without a "B-screw." Perhaps the angle of the pictures on Velobase or Disraeli Gears doesn't show it (neither site seems to want to load tonight).

ShannonM

You are correct, and I was wrong. (It's probably the picture angles, as you say.)

I wonder why my 1980 Superbe doesn't have a B-screw, when the lower-end V from the early 70s did. It seems like a thing you'd just put into every design once it's been invented.

--Shannon