Front derailleur adjustment or bent chainring?

zuma

Hello

I have recently purchased a third hand Cannondale R600. (This is my first ever road bike and thought that I'd buy second hand and see if I get a taste for it.)

"The R600 comes with Shimano 105 STI Dual Control shift levers. The front derailleur is a Shimano Tiagra, and the rear a Shimano 105 SS. The crankset is a TruVativ Elita LR with two chain rings each bearing 39/53 teeth. The bottom bracket is a TruVativ ISIS spline. The rear cassette is nine-speed with a tooth range of 12-26. The chain is 1/2 x 3/32 inch."

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http://www.ehow.com/list_7315185_cannon ... tions.html


After the purchase I took it to a local bike shop for a service. They adjusted the gears, brakes and a overall safety check. All happy and good.

Riding it for the first time it seems as though the chain is rubbing on the front derailleur when in highest gear every two or three pedal turns. A "wobble" or a "shifting" of the chainring on which the chain is on can be seen at a few pedal turns getting closer to the derailleur and then returning to the normal distance to which it was adjusted at.

So I re-adjusted the front derailleur as per countless YouTube videos and online guides but still rubbing. So could it be that the chainring is bent? But the thing is that it is also happening when in the lowest gear too - so does that mean that both chain rings are bent?

I understand that if the gears are cross linked then there will be rubbing on the derailleur, but that is not the case.


Any advice will be greatly appreciated it!

P.S. Should've the local bike shop doing the service spotted (if there is) a bent chainrings?

nicklouse

highest gear every two or three pedal turns.

worn BB?

if adjustment or bent ring it would be at least every rotation. (or more)

needs hands on looking at.