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-   -   Switft grinding in 8th gear? (http://www.bikeforums.net/folding-bikes/567489-switft-grinding-8th-gear.html)

drewthat 07-28-09 10:34 AM

Switft grinding in 8th gear?
 
Is anyone else experiencing a chain rubbing / grinding sound when in 8th gear on their swift? I just got my swift a week ago and although I'm enjoying riding it, I find myself avoiding 8th gear because there is a rubbing sound coming form the chain.

At first I thought that the chain might be rubbing against the frame because of the small clearance between it and the frame, but I didn't notice any marks on the frame itself. When I took a closer look at the alignment between the chain and the cog, the chain is at an angle which is causing the teeth to make contact with the side of the link, rather than the center. I took a look at the crank wheel and there is a similar misalignment, causing the teeth to rub on the side of the chain.

Yesterday when I was riding downhill and quickly shifted into 8th the chain actually came off the crank wheel and fell between it and the guard. This happened twice on the ride, and I had to put the chain back on.

Any ideas on how to make the adjustment so that the chain stays on, and the grinding while pedaling in 8th goes away?

AEO 07-28-09 12:26 PM

use a 9 or 10sp chain.
use a longer/shorter BB spindle if the chainring doesn't line up in a straight line when in the middle of the cassette.
cut the chain to the correct length.

for single chainring setups you thread the chain in big-big combo and add 2~3 inches, which is then fed through the derailer when joining the two.

alternatively, take it to the bike shop, preferably one that deals with folders since they have quirks compared to full sized.

vmaniqui 07-28-09 01:35 PM

Quote:

Originally Posted by drewthat (Post 9370578)
Is anyone else experiencing a chain rubbing / grinding sound when in 8th gear on their swift? I just got my swift a week ago and although I'm enjoying riding it, I find myself avoiding 8th gear because there is a rubbing sound coming form the chain.

At first I thought that the chain might be rubbing against the frame because of the small clearance between it and the frame, but I didn't notice any marks on the frame itself. When I took a closer look at the alignment between the chain and the cog, the chain is at an angle which is causing the teeth to make contact with the side of the link, rather than the center. I took a look at the crank wheel and there is a similar misalignment, causing the teeth to rub on the side of the chain.

Yesterday when I was riding downhill and quickly shifted into 8th the chain actually came off the crank wheel and fell between it and the guard. This happened twice on the ride, and I had to put the chain back on.

Any ideas on how to make the adjustment so that the chain stays on, and the grinding while pedaling in 8th goes away?

did you buy the whole bike new from xootr ? i meant whole bike since they also sell frameset only. if you got it from LBS or xootr maybe it is best to check with them. you are still under warranty. if it's rubbing then there certainly is a problem.

i had the same problem but my case is cross chaining. i have a 2 speed FD and when it's on 39T i can't go higher than 4th gear (i have a 7 speed) if i do go higher then the chain will rub. i tend to avoid this anyway. if i want more speed i just go 52T and 11cog. but in your case, this is a brand new bike so different story.

drewthat 07-28-09 01:43 PM

Yea this is a brand new bike, I got the full bike from Xootr.

vmaniqui 07-28-09 04:22 PM

Quote:

Originally Posted by drewthat (Post 9372140)
Yea this is a brand new bike, I got the full bike from Xootr.


great. now you've got all the reason to call them and tell them that you have issue with your new bike. if i were you, i wouldn't touch it or work on it yet as you're still under warranty.

thanks,
vic

sqynt 07-28-09 09:22 PM

Quote:

Originally Posted by drewthat (Post 9370578)
Is anyone else experiencing a chain rubbing / grinding sound when in 8th gear on their swift? I just got my swift a week ago and although I'm enjoying riding it, I find myself avoiding 8th gear because there is a rubbing sound coming form the chain.

At first I thought that the chain might be rubbing against the frame because of the small clearance between it and the frame, but I didn't notice any marks on the frame itself. When I took a closer look at the alignment between the chain and the cog, the chain is at an angle which is causing the teeth to make contact with the side of the link, rather than the center. I took a look at the crank wheel and there is a similar misalignment, causing the teeth to rub on the side of the chain.

Re: Alignment. This is normal. Your chain cannot possibly be parallel with your cassette in every gear in a derailleur system. It should be the most parallel with your cassette when your bike is in third and forth gear. Similarly, the chain will not be parallel with the chainring with the closest approximation in third and forth gear. On my Swift, there is some minor rubbing between the chain and the bashguard/chainring guard when in 8th gear. This is most likely due to the fact that the bashguard is completely flat instead of having a slight contour that chainrings usually have. A 9 or 10 speed chain can mitigate this issue depending on how much run out you have. However, if your chainring has significant run out, this is a problem. Take it to your dealer if this is the case.

Quote:

Originally Posted by drewthat (Post 9370578)
Yesterday when I was riding downhill and quickly shifted into 8th the chain actually came off the crank wheel and fell between it and the guard. This happened twice on the ride, and I had to put the chain back on.

This definitely should not happen. Just to be clear, did the chain fall off the front chainring? And fell off between the front chainring and bashguard? I can't imagine that there is enough space between the chainring and the bashguard for the chain to fall into. Are the chainring and bashguard parallel to each other throughout the crank's rotation? If not, this needs to be reinstalled ASAP.

datako 07-28-09 11:41 PM

If it came in a box rather than from a lbs, then it is possible your derailleur hanger is bent from rough handling. They are designed to do this to protect the derailleur and usually can be straightened. Most lbs have the tool for this and it only takes a few minutes.

jakub.ner 07-29-09 06:08 AM

Check that your wheel is square in the dropouts and that your rear wheel axle has no play and is not bent. Anything that may make the angle of attack between cog and chain off.

drewthat 07-29-09 11:56 AM

Quote:

Originally Posted by sqynt (Post 9375383)
Re: Alignment. This is normal. Your chain cannot possibly be parallel with your cassette in every gear in a derailleur system. It should be the most parallel with your cassette when your bike is in third and forth gear. Similarly, the chain will not be parallel with the chainring with the closest approximation in third and forth gear. On my Swift, there is some minor rubbing between the chain and the bashguard/chainring guard when in 8th gear. This is most likely due to the fact that the bashguard is completely flat instead of having a slight contour that chainrings usually have. A 9 or 10 speed chain can mitigate this issue depending on how much run out you have. However, if your chainring has significant run out, this is a problem. Take it to your dealer if this is the case.



This definitely should not happen. Just to be clear, did the chain fall off the front chainring? And fell off between the front chainring and bashguard? I can't imagine that there is enough space between the chainring and the bashguard for the chain to fall into. Are the chainring and bashguard parallel to each other throughout the crank's rotation? If not, this needs to be reinstalled ASAP.

Yes it fell off the front chain ring, and landed between the ring and the bash guard.



Quote:

If it came in a box rather than from a lbs, then it is possible your derailleur hanger is bent from rough handling. They are designed to do this to protect the derailleur and usually can be straightened. Most lbs have the tool for this and it only takes a few minutes.

Yes it came in a box, and yes my derailleur hanger was bent. I had called xootr about it and got a new one shipped to me, and installed it. So that's not likely to be causing the problem I originally posted, because the one on there is new.

I guess I'll have to check the wheel alignment in the dropouts.

alpacalypse 07-29-09 05:37 PM

Do you have a rack or fenders installed? A bolt for my rear rack (threaded through the right dropout's forward eyelet) sticks through a bit and interferes with my chain in 8th gear. I've been meaning to get a shorter one for a while...

sqynt 07-30-09 01:03 AM

Quote:

Originally Posted by drewthat (Post 9378923)
Yes it fell off the front chain ring, and landed between the ring and the bash guard.

Something is not assembled correctly with your crank set. The cranks on the Swift are standard double cranks, with a bash ring fitted in place of the larger chainring. A standard width 8 speed chain should not fit in the gap between the chainring and the bash ring with a proper set up.

Post some pictures of the crank set and we'll see if there's something we can help with. Check to see if your chainring or bash ring have excessive run out. A plastic zip tie around the seat tube with the uncut length adjusted just above the chainring is good for that. A standard 8 speed chain is 7.2mm in width. I'd say run out over 4mm is excessive.

drewthat 07-30-09 01:38 PM

Quote:

Originally Posted by alpacalypse (Post 9381485)
Do you have a rack or fenders installed? A bolt for my rear rack (threaded through the right dropout's forward eyelet) sticks through a bit and interferes with my chain in 8th gear. I've been meaning to get a shorter one for a while...

I have the xootr seat post rack, so it shouldn't interfere. I did get the fenders, but I have not installed them yet, so it's not that either.


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