New Chain and cassette - still skips under load

[Fredwina]

I just recently replaced my chain and cassette.
I runs fine (doesn't appear to have skips) execpt under load
the chain is a 9 speed shimano 105. The Rear dr is an Ultegra triple
I sized it using the method on park tools website - wrap it around the large cog and big Chainring without threading it through the RD.
The main reason i'm thinking that I got the length wrong is that I can't get it to skip on the Big ring, I haven't tried the granny yet. the Chainring have about 18,000 miles on them and are begging to show some wear.
Should I just be more patient, or seek professional help? I've done this a couple of time before, but I can't remeber having this much of a problem

[Trek420]

Howdy, define "under load" You're not shifting while climbing are you?

Good thread here:

http://forums.teamestrogen.com/showt...=load+shifting

[Fredwina]

Howdy, define "under load" You're not shifting while climbing are you?

Good thread here:

http://forums.teamestrogen.com/showt...=load+shifting

Nope, It does starting off from a light or going up hill.

[maillotpois]

Are you sure the cassette is on tight? If so, then I bet the chain is too long. Your worn chainrings shouldn't make the cassette skip.

I'd seek professional advice.

[DebW]

Is there a slightly stiff link in the chain from installation? The wrong sized chain shouldn't make it skip unless it is inadequately tensioned by the derailleur. If the chain is tensioned in the small-small combination you should be OK there. To check for excess wear on the chainrings, look for sloppiness of chain around chainring, or chain not seating firmly to the bottom of the teeth.

[agrsgrl]

Where does it skip? In the front or the back? You could try adjusting the indexing, but it sounds like maybe your front chainrings are worn. Have you checked for bent teeth or things like that?