Chain Skipping

I have the Shimano Dura Ace 7800 group on my Litespeed Vortex. About 1000 miles ago, I began to experience occasional chain slip on the chainring and the chain riding above the teeth of the rear cassette. The slippage increased over time.
I had a new chain installed yesterday (2300miles). According to my wrench, the chainring and cassette are fine. The RD is not bent. The chain is new. Yet, I'm still experiencing chain slippage and above teeth action on the cassette. I've meticulously checked the frame and fork for cracks...nothing.
Two thoughts and a question come to mind...
1. I've shifted gears during heavy load (on inclines) a couple of times over the miles. I know this practice to be a no-no, so it doesn't happen often, yet I'm thinking maybe something is bent on the RD that my wrench can't see.
2. I took ill suddenly 4 years ago and I stored the bike without it's wheels on a repair stand, hanging by the seat post, with the front fork hanging below the chain stays so as to minimize stress points.
Now, I ordered my custom frame with one of those lugs located inside the right seat stay to secure the chain during shipping. I utilized that lug; meaning that the chain and RD were under whatever pressure that position created for a period of 2 years while I was off the bike.
Question...Is it possible that the tension spring in the RD is weakened because of whatever pressure the RD was under for the 2 years? I've tried adjusting the "B" tension screw on the RD which adjusts the vertical position of the RD in relation to the cassette, but it doesn't (didn't) help.
So I'm turning to you; fellow roadies who may have experienced the same problem. What was your solution?
Thanks for your replies.

Hi, I'm not a mechanic, and perhaps you know more than I do, but I will give you my thoughts. I doubt it's either of the things you've mentioned. First of all, and I'm sure this is not the problem, but is it possible you have a 9 speed chain instead of a 10 speed chain?
Also, does the skipping occour in more than one gear? It sounds like your derailuer/shifter is not in sinc with your cogs. I would try very small adjustments of the barrel adjuster (in both directions) on the rear derailuer until you achieve the quietest/smoothest sound/operation of the shifting while on a repair stand. You can also make small adjustments to the barrel adjuster on the downtube while riding. These are micro adjustments that will help line-up the derailuer with the cog at each position of the shifter.
Also, make sure your cable is routed exactly as it should be, and connected to the correct side (top or bottom) of the fastening nut on the rear derailuer.
Hope it helps. Good luck.


I have the Shimano Dura Ace 7800 group on my Litespeed Vortex. About 1000 miles ago, I began to experience occasional chain slip on the chainring and the chain riding above the teeth of the rear cassette. The slippage increased over time.
I had a new chain installed yesterday (2300miles). According to my wrench, the chainring and cassette are fine. The RD is not bent. The chain is new. Yet, I'm still experiencing chain slippage and above teeth action on the cassette. I've meticulously checked the frame and fork for cracks...nothing.
Two thoughts and a question come to mind...
1. I've shifted gears during heavy load (on inclines) a couple of times over the miles. I know this practice to be a no-no, so it doesn't happen often, yet I'm thinking maybe something is bent on the RD that my wrench can't see.
2. I took ill suddenly 4 years ago and I stored the bike without it's wheels on a repair stand, hanging by the seat post, with the front fork hanging below the chain stays so as to minimize stress points.
Now, I ordered my custom frame with one of those lugs located inside the right seat stay to secure the chain during shipping. I utilized that lug; meaning that the chain and RD were under whatever pressure that position created for a period of 2 years while I was off the bike.
Question...Is it possible that the tension spring in the RD is weakened because of whatever pressure the RD was under for the 2 years? I've tried adjusting the "B" tension screw on the RD which adjusts the vertical position of the RD in relation to the cassette, but it doesn't (didn't) help.
So I'm turning to you; fellow roadies who may have experienced the same problem. What was your solution?
Thanks for your replies.[/QUOTE]

have you tweaked the cable tension yourself while you're riding (have some jagwire cable adjusters on my levers).. sometimes that's all it takes.. just a slight tweak and everything is everything.. you can try to get it right on the bike stand, but i find to get it perfect i need to teak the tension on the road.. then run through the gears to see what's up..

Top Ten Causes For Chain Skipping-:

CHAIN SKIPPING, or slipping of the chain while pedaling or shifting, is a common and annoying problem. Usually it happens while riding uphill, or under heavy pedal pressure, and results in fatique and loss of power - if not an outright accident!!

*Here are the top ten causes of CHAIN SKIP>>>>

Improper cable tension to the rear derailleur Fine tune the cable tension using the handlebar barrell adjusters so that the chain is centered on each cog on the rear cassette when it shifts


Worn or sticking cable This is a prime suspect in chain skip and often overlooked, so remove and lubricate your cable or replace it


Loose cassette Your rear cassette is loose on the hub and needs to be tightened


Worn, bent or broken teeth If your rear cogs are bent, worn, or missing teeth, this can cause shifting trouble - inspect, and repair or replace.


Dirty chain, kink in chain or rusty chain Your chain should be cleaned and lubed as one of the first attempts to correct a shifting problem - free any tight links, and scrub clean with a brush and then lube and remove excess


Damaged freehub body The freehub body coveys the energy from the cassette to the hub - it connects the two - and if it is starting to strip or is excessively worn, you will get lockup or chain skip


Debris in cogs Clean the rear cogs well and remove any debris or material that could be clogging them up


Bent derailleur cage or hanger Check the rear derailleur hanger and cage to see that it is not bent, and in the proper chainline


Loose hub If the rear hub is very loose, the bike might not shift properly - so check the hub for wobbling or side to side motion


Wheel not centered in dropout Make sure the rear wheel is centered in the rear frame dropouts before tighteneing the quick release or axle.

Chain length Your chain may be too long ot too short and cause shifting problems - also it may be excessively worn and require replacement.

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Thanks to everyone for their responses. Since my original post, the problem had increased in frequency. I tried adjusting the cable tension adjuster, had the RD checked for proper alignment, even replaced the chain w/a new CN-7801 10 speed chain. Nothing helped!
I returned the rear hub to my LBS and they got Shimano to replace my rear hub body. I'll pick up the new unit in a day or so...I'll keep my fingers crossed.
I also intend to lube the shifter cables (in about 5 minutes) as they have not been attended to since I've purchased the bike.
Again, thanks for all of the great suggestions.
Be safe on the road.

VRob

My guess is that your cassette is worn out. You could ask the LBS to try a new cassette next. They usually last up to 10K miles, or two chains for me, but we all have different riding environments.

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