sam.g

Hi,

i have a problem with my front derailleur not holding position on the big ring, it slowly moves left to the smaller chainring as I'm riding. This problem only manifests itself when on the big chainring. Both front and rear derailleurs are NOS Suntour Sprint 9000 in excellent condition.

I played around with the chain length and adjustments but nothing seems to hold. So i'm wondering if I've made a mistake assembling or setting it up or if there's a trick to keeping it in place. It's not possible to tighten it anymore. Any advice or a Suntour schematic/manual would be appreciated.

Sam in Cincy

gaucho777 

What type of shifters are you using? IME, when a derailleur does not hold its position, the problem is usally not enough tension in the shifter. If you are using downtube shifters, try tightening the mounting bolt on the shifters and/or cleaning the washers/shifter assembly.

rgver

have you tightened the shifter friction, or maybe put grease on the friction washer?

wrk101

Derailleurs just move the chain right or left. The lever and cable are the "brains" of the operation. In addition, sometimes the derailleur doesn't hold the big ring due to the high level screw being too tight. Its always best to move the derailleur back and forth by hand prior to attaching the cable, to make sure limits are set OK.

+1 the little washers on the shift levers are important!

What are you tightening? Is the clamp on the seat tube loose? If so, you have the wrong clamp diameter.

sam.g

Thanks for all the replies so far.

The shifters are Superbe Pro/Sprint 9000 levers in NOS condition that match the derailleurs. The shifter bosses are braised on so no loosening possible and the screw holding the left shifter in place is tightened to bottoming and nothing is loose. I have the limits set correctly, the chain doesn't over or under shift, it just doesn't hold in place. I believe that I have all of the hardware and washers but don't know w/o a schematic, also was wondering if there is a special way of attaching the cable.

Any other ideas of places to look?

thanks

Sam in Cincy

bear_a_bug 

To hazard a guess, are they new cables?

I'm not sure, but perhaps some cable-stretch is playing into this.

jimmuller 

Is your cable slipping in the anchor screw on the derailleur? As gaucho said, the position of the derailleur is set by the cable, end of story. If the lever is slipping then the derailleur will move. If the lever isn't slipping but the cable isn't being held tight by the derailleur, the derailleur will move. If the cable is stretching, the derailleur could move. If the cable is clamped to the DT and the clamp is slipping down then the derailleur will move, but you said yours are brazed on.

Loosening of the clamp on the DT may not be possible but the lever itself could still be slipping. Friction levers always have an adjustment. Maybe there is a washer missing on the left lever so that you can't get it tight enough.

weegie5012

Here's what I learned in the past couple of days: Attached is a thumbnail downloaded from another website, so a little blurry but readable, it shows all the parts in the shifters (identical left and right sides). Suntour PDL-M.
1)Each side shifter has 2 washers (#30008455 and #30008457 ) with a slight dish and a slot (steel, .062"), not the thinner washers, one on each side of the ratchet wheel. Make sure when reassembling that the concave part of the dish is toward the ratchet wheel on each side, or the friction will be wrong. This seems to be an important part of the reassembly if you take them apart to clean them. If the washers are backwards, you can't get enough friction to keep the derailleurs in position. The washers seem to be identical, if you get them mixed up it probably doesn't make a difference.
2) This diagram has a "spacer spring" #30008456 that wasn't present on my shifters on either side. Possibly this diagram is a later version--my shifters are on an early 1980's vintage Miyata. Does not seem to be critical to the friction.
3) The screws that hold the entire assembly to the downtube bracket are special, not just regular thread: the screws have slots with a nylon (loctite type?) coating pre-installed, to add extra friction so that the screws don't back out due to back pressure from the shifters. On my shifters, this coating was worn enough that the screws wouldn't hold--I used Loctite 248 (blue stick) as a substitute. Look at the screws under a microscope and you will see the slot and the coating.
I'm surprised no one else in all the posts has seen fit to discuss these fine points of the Suntour friction shifters.