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uneven Ultegra crankset(18 posts)

uneven Ultegra cranksetBryan
Oct 2, 2001 9:54 AM
I just put an Ultegra crankset on my bike, and i noticed that the large chainring seems to waver back and forth depending on the pedal position about the axis. I was wondering if there is any fix for this problem. Is it alright to try and bend the offending part of the chainring into plane? Perhaps a rubber mallet? thanks for the help.
more likelyD'Ohhh!!!
Oct 2, 2001 11:10 AM
it was installed incorrectly
re: uneven Ultegra cranksetDave Hickey
Oct 2, 2001 11:55 AM
It might not be warped. When I first installed nine speed Utegra rings, I thought the same thing. It turned out the ramps on the chain ring gave the illusion it was warped. It was not warped. Double check and make sure it's installed correctly and measure against the front derailleur cage before you start to hit it with a mallet.
Danger Will Robinson, Danger!grzy
Oct 2, 2001 1:31 PM
If you don't get the splines lined up correctly you run the real risk of trashing them.

Remove the crank, inspect all splines (BB and crank arms) look for mangled bits of metal. If nothing's mangeld consider yourself lucky, Remove the dust/retaining cap in the crank arm with a pin spanner wrench (or the tips of a pair needle nosed pliers). Reinstall the crank arm while sighting down the hole and lining up with the BB and install retaining bolt being careful to get the thin washer located correctly, torque to 50 to 70 N-m and install dust cap.

If your splines are trashed take the whole works to a good LBS to see if it can be salvaged.
Grzy's right!nee Spoke Wrench
Oct 2, 2001 5:13 PM
Shimano's design of crankset splines and self extracting rings has been good for the replacement part business.
Grzy's right!Bryan
Oct 2, 2001 6:53 PM
I had the parts installed by my buddy at the LBS. I just realized that the front derailleur was tuned in such a way as to avoid this "wobble," of the large chainring, which I should add is quite small, maybe 1mm. I was just very displeased with the performace, so I was wondering if my wrench toting friend was not the greatest mechanic.

I removed the crank via the self-extracting fixing bolt, and saw no signs of wear. It seemed as though the splines were aligned just right.

I was wondering if the cap is not threaded quite right, could this cause the whole crank arm to be malaligned?

I was also wondering if the Ultegra component could ever be tuned so that most gear combinations are valid?

It seems that about three per chainring cause derailleur rubbing.

Also, has anyone experienced a chain line, i guess it is called, that allows the chain to occassinally hit the large chainring?

thanks again for the help.
Tweaking Gearsgrzy
Oct 3, 2001 10:35 AM
Good news on your splines!

Back to your questions: 1st I don't know about your mechanic bud - hopefully he's learned much on other people's bikes ;-) It's not rocket science so he should be competant. there will be some "runout" on cranks from time to time. When they're new there isn't much, but with use and abuse they can develop some. This is a big reason why DA is so much more expensive than Ultegra - the stuff is more bomber. Typically the chainrings can be changed and the runout goes away, but if you've wanged the crank arm then obviously this won't work. Next thing to look at is the BB. Is it still installed correctly? An Ultegra/105 BB is a no brainer, but a DA unit requires some fiddling to get it just right (like XTR). These things do have some tendancy to loosen up over time. Yanking both crank arms and loosening the LHS cup is required to verify nthe RHS (with a torque wrench). then torque the LHS in. Finally torque on the arms - the setting of the dust/remavl caps will have no effect on crank arm set. Assuming your bike came built and you didn't start witha project bike one should assume that the correct BB length and chainline are in place. However, stranger things have happened. If the chainline is out your shifting performance will always suffer. Ultimately an Ultegra double setup should be able to be dialed in such that it is totally silent in ALL gears. This is the goal and it's possible with patience and systematic technique. A triple won't be perfectly silent when crossed from big/small or small/big. Mostly with the chain in the large CR since there isn't a "half-shift" in this position. It's very possible and likely that you don't have your front STI shifter indexed correctly - it's the same shifter for the double and the triple and you can be using the two main positions on the high end (top position won't have the half-shift) when you should be using the two main positions on the low end (both positions have the half shift). Getting the shifting on a road bike setup is similar to a MTB, but not quite the same. Many wrenches who primarily work on MTB's will miss some of the finer points. It requires patience to get it just right, but it's much easier to learn if someone shows you some of the tricks in person. If you're "heavy handed" it's going to be a challenging learning expereince. Setting the bike up in a nice stand really makes things super easy - you can tweak things all day. The Shimano instruction sheet is a good place to start - see if your LBS will let you copy or even have one.
Tweaking GearsBryan
Oct 3, 2001 11:44 AM
Grzy,
Thanks for all the info. I took it down to the LBS and got it tuned very nicely. There is a little rubbing from Large/Large and Small/Small, but it's covered in the gear ratio overlap so I'm not too worried.

Through this thing I've learned a lot about my drivetrain, and I wanted to thank you for your help.
I guess now it's time to spin, so happy riding.

-bryan
Kewl!!grzy
Oct 3, 2001 2:32 PM
You're on the path to learning all about the care and feeding of your drivetrain - a pretty handy skill to have when miles from anywhere. It's also very satisfying to be able to maintain your machine. Ultimately it takes patience - so if it's not going well, walk away and come back later - or go visit the guys at the LBS. You'd be surprised at how much info they'll provide if you ask AND listen. It also helps to throw them some business, even when you could get it elsewhere for less, and occasionally drop a nice cold quality six pack of good brew with the boys in the back.

I'm not sure of your setup, but I'd be a little surprised if you couldn't get all of that rubbing to go away. One thing that makes this impossible is if the front der. pivots are worn or a pivot screw is backing out. Lightly grab the cage and wiggle it in and out - if there's any real play then investigate. I once went through 4 front der.s (2 used & 2 new) before we got a good one for my buddies new ride. A cheap way for a quality stand is to get the Ultimate BOLT ON bench stand. Same quality jaw mechanism and pivot, but without the height adjustment of the portable stand - plus it's around $70.
Completely normal...TJeanloz
Oct 3, 2001 10:18 AM
I'd say that about half of all good chainrings are warped a little bit. It's totally normal. This was discovered when we had a particularly observant customer complain about a wobble in his new Dura-Ace chainring. We then put each of the D-A chainrings we had in stock flush agains a piece of glass to see how flat they were. And we were astonished that none of them was perfect. So, the answer is that they come like that new, and it may bother you, but it is not technically a problem.
Completely normal...grzy
Oct 3, 2001 10:39 AM
Realize that typical glass isn't always that flat. A granite surface plate is better for measuring flatness. However, your point is well taken. It's hard to keep stamped plates of metal nice and flat since some residial stresses are relieved and others are not. Hopefully everything ships within the defined specs.
Completely normal...TJeanloz
Oct 3, 2001 11:11 AM
I'll recommend to my old boss that they get granite countertops for the shop. Maybe we'll do walnut cabinets while were at it; I mean, with the rampant overcharging that all LBS' are guilty of, we should have only the best.
Hah!grzy
Oct 3, 2001 2:07 PM
I DO realize that you guys at the LBS are all getting filthy rich, but there's an easier way. A true granite surface plate is a special thing and not anything like the stuff you put on counter tops. They are as percise a piece of measuring equipment as a set of fine calipers. They come in all sorts of sizes, but they're always several inches thick and are checked and calibrated on an annual basis. They are quite heavy. Having said all this it would be very easy to buy a smallish reasonably priced surface plate to be used only for measuring. Check out a machine tool supply place or one of the many mail order places. Poke your head in a machine shop and ask to see their surface plate. Maybe they'll let you place somethings on it to measure - and you can keep all that $$$ you're raking in.

You could probably place something that is perfectly flat on your glass surface and be tempted to think that it's not flat. Ever seen window glass from an old house and notice that it's thicker at the bottom than at the top? Glass is more like a very stiff fluid in some respects - it flows.
Not really on the glass flowingbikedodger
Oct 3, 2001 2:59 PM
Grzy,

Window glass does not flow at the temperatures seen in houses. The older houses used glass that was uneven in thickness and the glass was installed with the thicher end at the bottom.

http://www.urbanlegends.com/science/glass_flow.html

Mike
http://www.glasslinks.com/newsinfo/supercooled.htmbikedodger
Oct 3, 2001 3:04 PM
Hmmm...grzy
Oct 4, 2001 8:54 AM
I followed the interesting links but was disturbed by the ending. One urban legend is dispelled with another - if we could just find an window glaizers' manual from the 1800's that instructed them to install the thick end along the bottom we'd have conclusive proof. Yet this conclusive proof isn't there....

Guess I should've slept through science class that day.

I guess my orginal point is that if you want to measure the flatness of something you don't place it on a piece of glass that's part of a display cabinet - for a variety of reasons.
Hmmm...TJeanloz
Oct 4, 2001 9:03 AM
It's a point well taken, but in the real world, we work with what we've got, which is not necessarily the perfect tool for the job.
Hmmm...grzy
Oct 4, 2001 1:43 PM
Sure - you run what you've got. It is helpful though to be aware of the limitations so that proper conclusions can be made. Glass is reasonably flat, but recently I've been spending a lot of time at work inspecting glass (quartz actually) components and these things are all over the place - even after being machined, ground and lapped. I actually reject a lot of stuff b/c it's not flat enough - and I'm talking several thousandths of an inch. The granite surface plate is what we use to reference the glass ware. A lot of the problems occur due to the heat used for annealing and welding - not exactly room temp. to be sure.