bicyclebikes

yesterday i bought a new 2009 trek madone 4.7 with shimano ultegra components on it. I went for a short ride today and realized that there were some problems with the shifting. When i am in the big ring in the front, and the smaller ones in the back, the chain almost seems to skip on a couple of the teeth on the cassette. Also, when i am in the big ring in the front and the big ring in the back, the rear derailleur automatically shifts it down a couple of rings in the back. I am not sure what the problem is, but i know that the components are brand new.

DOS

The derailleur needs to be dialed in a bit better. Minor cable tension adjustment and maybe limit screw adjustments ought to do the trick. Since you just bought it, bring it back to the shop and have them make the adjustments.

wrk101

+1 One of the key advantages of buying new is after sale service. That's built into the price of a new bike. Take it back and have the experts adjust it for you.

mzeffex 

Yeah, get it adjusted. You shouldn't be in the big/big or small/small rings though.

joejack951

If you'd prefer to learn versus always needing to take your bike into the shop for minor adjustments, read up on derailler adjustments at www.parktool.com

You only need basic tools and a reasonable amount of mechanical sense to dial in a derailler properly. Most adjustments are simply a matter of tweaking cable tension though. Read through the Park site and watch what your bike is doing while shifting it on a stand (or upside down if you have no stand). Determine which direction the derailler needs to move to function properly then adjust limit screws or cable tension to get there. Assuming the shop you bought the bike from had a clue, you shouldn't need to touch the limit screws; they are typically set once and never touch again.

operator

Shouldn't or not, those gears can be adjusted to work properly.

joejack951

One needs to understand how to trim the front derailler in most cases though. The OP would be well served by reading through the tech docs at Shimano's site as well as the Park Tool help guide.

operator

Assuming the bike was even built properly, which is a very good assumption not to make. The standard cable length on those madones is with near certainty 100% too short for the rear loop. Assuming it was cut properly the OP is going to basically just want to tear down the entire cable system and readjust the derailleurs from scratch. Was the hanger checked for alignment? Again, new bikes out of the box with misaligned hangers. I've yet to seen hardly any bike shops putting out assemblies and assemblers worth more than 3 cents.

joejack951

I won't argue with that.

operator

I just checked a '10 madone this afternoon, pre-assembled by another shop.

1) All cable and housing either too short or too long
2) Cables crossing inside the downtube and crossed in front (what the ****?)
3) Barrel adjusters (not needed for rear), upside down
4) Derailleur hanger bent

We're not a Trek dealer so god knows how many crappily assembled bikes are floating out there. Use of the pre-cut shimano rear derailleur loop is almost a near 100% dead giveaway that it is too short and the person assembling it blows ass. For gods sake it was full Sram Red.

roberth33tiger

Is it possible, the chain is short also? (back shifting in big-big)

Kimmo 

Yeesh, that Kmart-style assembly is a horrible fate for such nice gear.

gbg

+1000000

mzeffex 

Honestly though, I could not understand the park stuff. Maybe I'm just incompetent, but I don't think it works for everyone. But now I work as a mechanic and it's easy.