Suntour query

[setspeed]

I recently bought a '92 bike with a Suntour XC Ltd groupset. I've never had a Suntour drivetrain before and, although I like it for the most part, it has a strange quirk that I'm not sure is normal or a fault. I've not bothered to research it or try adjusting any components yet, I thought I'd ask here first, to see if it's normal/expected behaviour.
The issue is that when upshifting to a higher gear on the rear mech, it feels like there's a short period when the chain completely disengages from the cassette, and suddenly there's me spinning the cranks like crazy. Then after a fraction of a second, the chain engages in the higher gear.
It's very disconcerting at high speeds/cadence.
Can anyone chime in with knowledge about this?

 

[FluffyChicken]

Do you ride modern stuff.

They have a longer engagement in the old stuff
That or it is slightly out on shifting, they work by overshifting on the up, Shimano fiddles that by using a wibblypulley, the centeron, so it then moves to 'centre on' the cog.
So it could be riding up on the cogs for a bit..

That or it for some reason doesn't have the AP or AP-II cogs

Or... Erm buggrit
You'll get used to it.
Ride and tweak the adjustment aft eh shifter barrel, see what happens.

 

[Tootyred]

I cant say ive ever had that on suntour..i use it all the time. Sound more like the indexing has been set up at one end of the block, not to the middle....so the other end is getting a bit woolly.

Ride and tweak the adjustment aft eh shifter barrel, see what happens.

 

[Tootyred]

Other than that, check hanger alignment, check chain wear, check cassette wear, check jocky wear......

 

[setspeed]

Thanks for replies. As I said, I've not done anything with the bike yet, just got it and ridden it a couple of times, and there is some rattling in a couple of gears which indicates the indexing needs sorting. So hopefully the issue will go away with some tweaking. I just wondered if it was a Suntour issue, because I've never had the same thing happen on any Shimano drivetrain, even when the indexing is properly 'out'. Shimano either shifts (and rattles badly), bounces up and down between cogs, or it doesn't shift.

 

[FluffyChicken]

Unless there is play in the mech, then unlike Shimano it can't fall inline. It's why replacement guide pulleys often didn't work well on Shimano as people got used to the Shimano setup. Until they started adding play (side to side movement aka centeron) in the pulley.


Mine always had a very secure sounding thunk on gear change, this was 7 and 8 speed MicroDrive. Felt well made and reliable.

 

[Dr Dremel]

I´ve had that same issue on a bike with a low milage XC Pro gruppo, all stock including a minty AP II chain. Very annoying and quite dangerous, as it caused a pretty serious endo when I laid down power and cranks spun free. I knew of the issue, just not in that moment

I did replicate the problem, it was the side plates of the chain riding on top of the teeth of the sprockets, no engagement until the chain would fall onto the sprocket. No matter how I dialed in cable length and end points, the problem would persist and shifting was kind of random.

The first thing which actually made a difference was the way the cable was pinched on the RD. I don´t know how the LTD RD looks like, but on the XC Pro there is a small ridge, in which the cable must sit (similar to the more common XT 735 RDs). If it does not sit exactly in that ridge while being pinched, it changes the leverage ratio and the clicks in the thumbshifter are always off.

But sometimes the chain would still slide. What got rid of that behaviour was that I changed the right thumbshifter. Comparing the two the old one was slightly bent. Now in theory this should not have affected the ratios (amount of cable being pulled), but it is working fine since then.