hero419

bike specs...
07 Specialized Allez elite triple
FRONT DERAILLEUR Shimano Tiagra, 31.8mm clamp, bottom pull
SHIFT LEVERS Shimano Tiagra, 9-speed STI, flight deck compatible
CHAINRINGS 52x42x30t

I was told by the sales person that there are "half" shifts. Is this true? I know they are there and I use them, what I mean is, is it a design necessity?
Is it that way to create less noise from the front derailer when shifting the rear derailer?

Why is it that I can take out my snow bike (old, old Scott ridged mountain bike) and not have any problems with cross chaining in any gear. By the way, the Scott gets the least amount of maintness of the three bikes I own, is covered in grease and road grime, I am the second owner and it is beat up beyond beat.

any who, How do I shift this bike without looking like a fool making all kind of grinding noises while shifting my $1000+ road bike in front of friends with 500 mountain bikes with road tires that shift smooth.

Yes I am the only one in my area that I hang out with that owns a road bike.

I am trying to word this without getting beat up over it but I think it is impossible.

the beef

'Half-shifts', also known as 'trim', are a very important feature on road bike drivetrains. Some gear combinations cause the chain to rub against one of the plates of the front derailleur, so yes, you'll need it. It's not a question of maintenance or anything like that - it's just what you have to do.

If it helps to glance down at your front derailleur while riding, then do it. Either way, you'll son get a feel for when you need to trim, and it won't seem so complicated.

hero419

Why is it important on a road bike and not a mountain bike?

crydee

I don't think there is any trim adjustments on triples.. I might be wrong

hero419

If there isn't, then I have a bad combo of parts!

curiouskid55

Should work near flawlessly, if it doesn't take it back where you bought it and make them adjust it until it does.

rankin116

There is on mine. At least what I think is meant by "trim". In the middle chain ring, there are basically two place the FD sits, described as a half-shift, like the OP said. Depending on where I am in back, I use different "trims" on the FD, but only when on the middle ring.

JMT114

+1

Psimet2001 

Ride a well adjusted road bike long enough and you will understand.

hero419

Understand that a mountain bike works flawlessly without it? (trim)

martytardy

"half-shift" or "trim" is a necessity on road bikes. Could it be because the large chain-ring, often a 50 or 52, is just plain bigger than that on mountain bikes, usually with a 42? That's how I see it. I just bought my '05 Cannondale R500 1.5yrs ago and just barely learned about the "half-shift" about two months ago. I can't tell how thankful I was when I learned about it and how much it has helped my riding. I'm still working on getting the feel for the half shift going up towards the big ring, but have the half shift going down from the 52 to 42 (middle) ring downright downpat. I used to get SOOO MAAADDDD that I could only use like 4-5 of the largest cogs in back with my 42 up front. Luckily I lost my temper when I learned about the half-shift function.

roadnsnh

I have a Tiagra triple. There are trim clicks (half shifts?) for both the granny and the middle ring. None for the big ring.

Leland

Mr. Beanz

Freaked me out man! I bought my wife a roadie then took it in for the tuneup. The shop dude said to my wife,"let me check your trim!" should have seen her jaw drop!

martytardy

HAH HAH HAH!!!! Hillarious!!!! No offense to your wife. Since I just learned about the "half-shift" 2mos ago, if even that long, I just learned it was called "trim" tonight reading this and other posts about the same subject.