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Old 08-03-07, 10:48 PM   #1
Funyet
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Downtube FS chain is skipping - how to fix?

I got a Downtube FS 2007 on eBay at a very decent price. I just got around to trying it out today. The chain skips often in 4th gear. I realize Downtube suggests a look by a bike mechanic. Before I spend the $$$ on an inspection can someone tell me what might cause this and how I can make adjustments? I'd rather put more than a couple miles on the bike before going to a mechanic.

Thanks
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Old 08-04-07, 06:26 AM   #2
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Check out Sheldon Brown's website for adjusting rear derailers.

http://sheldonbrown.com/derailer-adjustment.html
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Old 08-04-07, 01:21 PM   #3
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And especially check whether the dérailleur hanger is bent.
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Old 08-04-07, 05:00 PM   #4
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You might need a new chain and rear cassette.
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Old 08-06-07, 09:46 AM   #5
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If you read about my DT experiences, you'll know that I went through this exact deal. It can be fixed. The derailleur hanger is probably bent to some extent. Get a big crescent wrench on it and get it straight.

Take the JUJU rear derailleur and shifter off the bike and throw in the nearest, largest body of water. Buy a SRAM derailleur / shifter combination. Put on the bike. Problem solved.

I know it sucks to do that to a brand new bike. I got my upgrades off of Ebay. I picked up the X.9 (very short cage) derailleur and X.0 shifter for about a total of $120. I put them on myself to save the LBS fees. Know that a derailleur will not be perfectly straight through it's entire range of motion. I've got it dead straight in the middle gears and a little off the piss at each end. It's worked perfectly since I put it on.

Besides _awful_ shifting, my bike was throwing the chain about once per 1/2 hour ride, sometimes more. I couldn't use 9th gear because that was an automatic thrown chain. Anyway, putting the SRAM stuff on the bike has transformed it. It shouldn't come any other way.
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Old 08-06-07, 10:34 AM   #6
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I picked up the X.9 (very short cage) derailleur and X.0 shifter for about a total of $120.
Fat Boy:

I'm surprised that you got the short cage derailleur for the 11-32 tooth cassette. Did you really mean short cage? If so, does it indeed shift properly all the way to the 32?

Thanks,
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Old 08-06-07, 10:34 AM   #7
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Did you need a new chain or chainrings or did you just replace the cage and shifter?
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Old 08-06-07, 11:01 AM   #8
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Fat Boy:

I'm surprised that you got the short cage derailleur for the 11-32 tooth cassette. Did you really mean short cage? If so, does it indeed shift properly all the way to the 32?

Thanks,
I have never tried the specific example myself, but I have gotten a 105 cage derailer to work with a 30t cassette and a triple up front.

With a b-screw adjustment (do SRAM derailers possess such a thing?) and a single chainring up front, I would think that it would work. Especially if the derailer is designed for MTBs.

-G
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Old 08-06-07, 11:23 AM   #9
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The short cage SRAM can actually handle a 34 tooth big-wheel on the cassette. Getting it to work was a snap, really. The total amount of 'chain wrap' that it can handle is 30 teeth. 32-11=21. I'm running a 53 tooth chainring, so if I really wanted to, I could theoretically have another dual chainring setup with a 44 tooth chainring as the 'granny'. To go with a larger spread between chainrings, I'd have to go to the medium cage. Rear derailleurs have to take up the slack in the chain. If you are only running a single chainring, the short cage is a no-brainer as no cassettes are large enough to cause a problem.

I've never had a shifting setup that was as sharp or precise as what I have for my DT. If I were Yan, this would be an upgrade option on all DT bikes. Maybe make a 'stripper' version with the JUJU stuff on it, but then a nice version with SRAM X.9 or X.0.

I'm guessing he would have happier customers in the long run.

I got my stuff here: http://cgi.ebay.com/SRAM-07-X-9-Rear...QQcmdZViewItem

Last edited by Fat Boy; 08-06-07 at 11:32 AM.
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Old 08-06-07, 11:27 AM   #10
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With a b-screw adjustment (do SRAM derailers possess such a thing?) and a single chainring up front, I would think that it would work. Especially if the derailer is designed for MTBs.

-G
Yes, they have one, but I didn't touch it. I set the cable tension (with the adjusters in the middle), High and low stops. Get on and ride.

I spent more time getting the hanger tweeked in than installing the derailleur and shifter together.
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Old 08-06-07, 11:31 AM   #11
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Did you need a new chain or chainrings or did you just replace the cage and shifter?
I had already installed the 53 tooth chainring to get more gear on the big end. It didn't have anything to do with making the shifting good or bad, though.

I did change chains when I stuck the 53 on, because I noticed that the chain the DT's are delivered with are a cheaper 8-speed chain as opposed to the 9-speed chain that it should have originally been delivered with (poor spec'ing of components, IMHO). I got a Shimano chain on closeout for less than $20.
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Old 08-06-07, 11:33 AM   #12
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Fat Boy:

Thanks for the clarification. It makes sense now.

I had put some SRAM X.7s with trigger shifters on my DT Front Suspension and was really happy with it also. Very snappy shifting - huge benefit for relatively low cost. Trigger shifters are so much better than grip, IMHO.

Apologies to OP for the thread hijack...Back to the original topic, my vote is for a bent derailleur hanger also.
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Old 08-06-07, 04:02 PM   #13
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I agree that a SRAM X7 set up will be nicer, but it might not solve your problem.

The hanger could be bent, or, more likely, the cable could be snagging. My Downtube had a terrible snag that wasn't cured by lubing it, but lubing did help. You might save yourself more money by going to the LBS, but I would check and lube the cable housing (see Sheldon's section on this) and eyeball the cage and hanger. If the latter, you can pound it straight quite easily.
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Old 08-06-07, 10:42 PM   #14
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I've always been a trigger shifter type of guy, but I have to admit, I'm kinda diggin the grip shifters. Especially the X.0. If I have a steep uphill that has caught me out, I can grap about 5-6 gears _real fast_. Being that I'm using my whole fist instead of just my thumb, there's no question about whether it'll go into gear, either. My next real mountain bike is probably going to be a gripshift. Who woulda thunk it?

The SRAM shifter that you have to run with SRAM derailleurs have teflon coated wire. This alone takes a lot of the snagging out of the shifts.

Have we confused you enough, Funyet?
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Old 08-23-07, 05:02 AM   #15
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The hanger could be bent, or, more likely, the cable could be snagging. My Downtube had a terrible snag that wasn't cured by lubing it, but lubing did help. You might save yourself more money by going to the LBS, but I would check and lube the cable housing (see Sheldon's section on this) and eyeball the cage and hanger. If the latter, you can pound it straight quite easily.
One thing to check on them is after you fold it make sure that the cable isn't looped where it folds and that the cable goes back into the guides along the backside. This happened to me and I didn't see it wasn't in one of the guides on the frame in the backside. Question has it EVER not skipped and if it was ok once then check all these things said from the group. Of course by now I bet you got it fixed.

Scott
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Old 08-23-07, 06:23 AM   #16
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Aren't you glad you didn't take it to the shop?

You should get a tune-up on any bike you purchase after 50-100 miles anyway. DT uses a lot of no-name parts, so I'd go with the recommendations to replace the rear derailleur and get a name brand (e.g. SRAM).
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Old 08-23-07, 07:39 AM   #17
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Aren't you glad you didn't take it to the shop?

You should get a tune-up on any bike you purchase after 50-100 miles anyway. DT uses a lot of no-name parts, so I'd go with the recommendations to replace the rear derailleur and get a name brand (e.g. SRAM).

I just got this bike (40 miles in 3 days)so it did ride correctly once anyway then I took it out on the trails and folded it showing it off. Afterwards it skipped. So I checked the cable route and sure enough it wasn't right. I also fell out of the holder near the shifter so with all this it says CHECK the cable route after folding. Which might sound a little basic but some of us are so eager to play with the new toys we overlook the simple stuff.
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Old 08-23-07, 10:17 PM   #18
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First thing I would do is check chain length. I have had three Dahons, and they all had chains that were too long.

Once I got them to the proper length, I never had a problem with drops or skips. If unsure, Sheldon's site or the Park and other maintenance books should point you in the right direction.
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