I have a Giant Quasar
I have a Giant Quasar
wow that didnt work. I typed a whole message and thats all that showed up?
ok starting over.
I have a giant quasar with suntour accushift 1500 derailluers with indexed shifting. When shifting into and out of the largest rear sprocket, the chain doesnt seem to line up with the upper derailluer pulley. It still shifts, but it makes a rubbing/grinding noise. the rest of the gears shift perfectly. any ideas?
thanks in advance
also does anyone know what this bike would have sold for originally?
Hehe, I was wondering if you were expecting us to diagnose it telepathically
It sounds like the limit screw on the rear derailer may be adjusted incorrectly. The rear derailer has two screws on the back, one which limits how far IN the derailer can move (low gear limit), and the other limits how far OUT the derailer can move (high gear limit). You should try loosening the low gear limit screw so that the derailer can move a little further inward.
See http://sheldonbrown.com/derailer-adjustment.html#rear for details on RD adjustment.
That was my first idea. the limit screws are set correctly. The largest sprocket to the 2nd largest is a much bigger jump in size than the rest of the sprockets. Could the shifter just not be pulling it up as much as it needs to?
Are the freewheel, derailer, and shifter all original stock parts? None of the Accushift freewheels that I've seen had a markedly larger jump between top cog and 2nd cog compared to the others... this page has a list of sprocket spacings for SunTour freewheels that you can compare yours to: http://sheldonbrown.com/k7.html#spacingOriginally Posted by fadetoblack6902
Can you make it shift fully onto the big cog by putting the shifter into indexed mode? What if you simply tighten the adjusting barrel on the derailer so that the derailer pulls 1 mm inward on ALL the cogs, will that work?
By the way, most SunTour freewheels shift pretty poorly compared to a modern ramped freewheel. I've successfully replaced SunTour Accushift freewheels with cheap 6-speed and 7-speed freewheels from Nashbar, and they work a lot better since they have nice shift ramps.
I do not know if they are all original parts. I am not the original owner. I tried tightening the adjustment barrel, but it still had the same problem. It will always shift into gear, it just has a delay and grinding. I didnt know you could take the shifters out of indexed mode. how do you do that? I have a couple shimano 600 freewheels, I may just try to swap it out and see if it gets better.
My Cannondale SM500 has(had) Suntour Accushift 7sp stuff. For years i've had alignment problems with it and shifting. The cables and pulleys had to be pristine and the hangar had to be in super-precise alignment to work. I'm not sure if it was an Ultra-7 freewheel or what (the year of my bike pre-dates microdrive), but finally the pawls failed and I got a new nickel-plated ramped Sunrace freewheel -- miles of improvement. Then a week or so later one of the X-Press shifter pods broke a lever, so I am upgrading everything to an old Shimano Alivio groupset i had lying around. I tried the shimano shifters with the Suntour X-1 rear derailleur and things did not line up like the OP was describing. Perhaps your bike had some upgrades and there were slight spacing differences that never were resolved. The Alivio groupset is roughly the same performance level as X-1 and so far things look promising. Try the Shimano Freewheel and i'm sure you will notice some improvement.
Yes, every Accushift downtube or bar-end shifter can be switched to friction mode. There is normally a knob or a metal tab on the side of the rear shifter that allows it to switch modes. You may have to remove the shifter from the frame temporarily in order to turn the knob, if it is very stiff.Originally Posted by fadetoblack6902
I wouldn't try swapping to a Shimano 600 freewheel right now, since it will only complicate things until you figure out what the problem is. A Shimano 7-speed freewheel, while very close in spacing to a SunTour 7-speed freewheel, is not *exactly* the same (see that link I sent earlier!!). I've had good luck getting a Shimano freewheel to work with a SunTour shifter and derailer, but at this point adding another variable to the problem won't help you...
Hmmm... I would think that Suntour X-1 is significantly better than Alivio (which is low-end OEM Shimano stuff).Originally Posted by rat_factory
It's unfortunately the case that a Shimano shifter won't work with a SunTour derailer. Some people have improvised little tricks to make them work right!
Ok it is definately an alignment issue. I realized it shifts perfect when in the large chainring. any idea where to go from here?
Weird... I can't actually think of a problem that would cause the LARGE cog to work with the LARGE chainring, but NOT the small chainring. Did you try friction mode?Originally Posted by fadetoblack6902
Hmm, havent tried that yet. i'll have to try it
Besides the cast alloy outer parallelogram face on the X-1, the Alivio rear mech weighs 5 grams less than than it. Alivio is available aftermarket and is right behind Deore. I'm not really sure, but I think X-1 was behind the crappy XCE, not XCExpert, mind you which is very nice. But then again it was a while back and I can't remember what happened 5 minutes ago. The front mech I'm using is acutally a Shimano FD-MC21, which is newer Alivio stuff and also weighs 60 grams less than the X-1 front derailleur.Originally Posted by moxfyre
All I know is that new(>1987?) slant-derailleur Shimano shifts better than any of my Suntour stuff ever has. This bike is plagued by breaking and bending parts and spends more time in the repair stand than it does being ridden.
Oh and what tricks do people use to correct different cable pull and pivot points?
Hmmm. That sounds to me like you have a Shimano mega-range freewheel and Suntour shifters and derailleurs. That's not a combination that was made in heaven. Suntour freewheels had different spacing between the largest cogs.Originally Posted by fadetoblack6902
Some derailers have more than one point at which you can connect the cable... in some cases you can connect the cable at a slightly different distance from the pivot, and thereby alter the mechanical advantage of the derailer. Search the forums or r.b.t, and you'll probably find a hack or two!Originally Posted by rat_factory
UPDATE: here's Sheldon Brown's trick for using a pre-1997 Dura-Ace shifter with a different Shimano derailer (Shimano's pre-1997 DA had a different actuation ratio than every other indexed derailer Shimano has ever made, bizarrely enough). http://sheldonbrown.com/dura-ace.html#alternate
Hmm, i knew i had seen that 'alternate cable routing' somewhere. I should have know it was Sheldon's site . I will definitely give it a try. Then again, if I go with my Alivio stuff I know it is compatable with itself.Originally Posted by moxfyre
That Sheldon, he's a crafty oneOriginally Posted by rat_factory
The basic idea is, if your shifters pull the derailer TOO FAR, then shorten the lever arm on the derailer so it moves less. If you shifters pull the derailer NOT FAR ENOUGH, then lengthen the lever arm so it moves more.
There won't always be a reasonable way to do this while securely clamping the cable, but it's always worth a shot.
Please bear with me - I'm trying to learn here. What makes everyone think this is a derailluer problem? Why not a stretched chain? Would a stretched chain show additional problems? Is that the reason for dismissing that possible cause?Originally Posted by fadetoblack6902
Sorry for not getting the picture.
It's a good question! But this is slightly different from the (typical) symptoms of a stretched chain.Originally Posted by dalmore
The OP says chain makes grinding noises after shifting, but he doesn't say anything about the chain "skipping" or "jumping". The hallmark symptom of a stretched/worn chain is that when you apply too much force to the pedals, the chain loses its grip on the cog and suddenly slides over the top of it. This doesn't cause problems in shifting the chain, it only causes problems when pedaling. Furthermore, chain wear *almost always* is more of a problem on the SMALLER cogs. This is for at least two reasons:
(1) The smaller cogs have fewer teeth than the large cogs, so they get worn out faster because their are fewer teeth to spread out the wear
(2) The smaller cogs have fewer teeth than the large cogs, so there are fewer teeth for the chain to grip
Sheldon Brown has a fabulous article on chains, with a section explaining what exactly causes "chain and sprocket wear" (the two basically contribute to each other in a vicious cycle): http://www.sheldonbrown.com/chains.html#wear
Thanks that's helpful. I appreciate it.
Personally, I think you should have just stayed with this and watched the direction the thread took.Originally Posted by fadetoblack6902