My bike came with a 110mm stem but when I swapped to campy, the shifters are longer than shimano so it makes my stretch out more, just a little but makes a difference (im sure campy users can chime in).

How much of a difference will switching from a 110 to 100 or even 90 cause?

I thought about 100 but not 90 because I think 90 will be too short but I do not have stem experience.

I often place my hands right before the shifters but when I get out of the saddle I feel normal on the shifters.

BTW, my bike has a Look HSC 4 fork on it, it uses a 31.8 correct?

Not that hard - 10 mm, just shy of 0.4". It'll be at a bit of an angle, but nothing to worry about.

Some claim that changing your stem by 20 mm makes a large difference in steering/handling, but I've never found any large effect either through geometry (math) or practical experience.

Are you saying that it will be fine if I swapped for a shorter 100mm stem and 10mm would provide sufficient difference?

While I can't help you with your shimano to campy question (all campy here), you can always look into a handle bar with a shorter reach and or a shorter stem. I use the new FSA shallow drops on my Lynskey L3 and on my 555. I can't remember what size your 555 is but it has been quite the challenge getting my 555's fit to match my Lynskey. B/c of the STA I ended up with a 20mm setback post and a 105 length stem vs. a 25mm post and a 110mm stem on my Lynskey. Had I gone with a small I'd have probably could have used a 25-30mm setback post with my normal 110 stem. I would have had more spacers than I prefer but than again I'd have more seatpost showing (have about 7" now). Just curious what size frame did you go with and what's your cycling inseem/height?

I can't answer that for you. 20 mm is a rather large difference, 10 is obviously only half as much. If you aren't sure, guess, and go online and get the cheapest stem you can find. You should get one for $20.

I ride a 55cm Look, 31 to 32in inseem, 5'11 to 6ft tall, I have long arms for my body. When I got my bike professionally fitted, the fitter said that I am fine with the setup and if anything I can swap to a FSA shallow drop handle bar but that means that I will have to rewrap my bars, buy a shallow drop, etc. It will be easier just to swap the stem.

I have to say that when I ride my bike with the 110mm stem, it does not cause pain or any issues. For sure, I do not want to change anything and have a problem occur.

Try to measure the difference in the reach between the campy and shimano levers. That might help some.

This is assuming you like the previous position though...

edit: pm me with your results, I am debating going 10mm or 20mm longer. I was also wondering how much I would feel either one...

It's easier to swap out stems than handlebars.

Sliding your levers up and tilting your bars down has the effect of bringing the levers closer in.

But you lose the position you like... That would be one of the last things I would do.

Or borrow one from a club/teammate buddy. I literally just picked up a Forte one for $20 to see the difference. If it does then maybe I'll buy a nice one. If it doesn't atleast I know. At $20 I don't feel bad biting the cost or returning it.

I was thinking of doing the same thing until an lbs owner told me otherwise... see other thread.

got link? quite a few threads from your profile

When I buy a quality stem like the CF Ritchey one I have, I'll get it from my LBS, they may of even lent me one, but I work next door to Performance and for $20 it's was just cost/time efficient for trying it out.

I'll see if I adjust to the setup as is.

I had a 110 stem on my Wilier Cento and always felt like I was reaching a little too far. I hesitated putting a new stem on as I didn't think that 10mm would make that much of a difference.

I was wrong. The 100 feels so much more natural and it made what resulted in a massive difference. I noticed no change in steering feel. 90mm stems seem to be a last resort for fitting, and generally if your frame was seriously oversized when you bought it.

Another change that I made on the Cento was the type of handlebar. Some bars just reach further forward, and I was able to bring the brake hoods that much closer by moving from a Ritchey Logic to a Ritchey Streem.

One more thing that you could try before switching stems is to move your seat forward a little more, too. That is the cheapest option of all these

That's good advice - I'd take it one step further and say just buy both and figure out which you like better. I have accumulated so many stems over the years in various lengths and rises and it really helps when setting up a new ride. If you don't get too worried about weight, you can find them truly dirt cheap on ebay, and have the luxury of logging enough saddle time with them on the bike to really make a good decision. Then once you have it dialed, you can pony up for something a little swankier if it suits ya.

It's really hard to talk about stem length because it's entirely subjective to everything about you and your bike in specificity. You really need to try different stems out for yourself.

Yea I might try out a 100mm to test it out, Thanks for the help!

You might try the dreaded fleabay for a stem. I got a new 110 and a 100 Easton EA50 for $12.00 each, buy it now, delivered from a dealer "Abaxo". I say several others from other guys as well.

They make 105's as well if you need to dial in your fit even more in that range.

My LBS's all have "fit stems" which you can put on your bike while on a trainer in their shop. Ride for a while, change angle and reach. You might be surprised at how obvious the sweet spot is.

Also, one of the LBS's (at least) has a whole rack of take off stems that they let you use for a while to test, assuming you ultimately buy one from them.

If you're the guy who's LBS says you can't use non-Deda stems w/ Deda bars, find another shop, preferably with both of the above ways of deciding stem length and angle.

OP you did not state what the stem angle of the original stem was? You may be able to get a shorter reach by changing to a stem with a different angle keeping the stem at the same length. Assume you were comfortable in the original position and you have enough miles to make that statement.

I chose a different stem based on where my hands wanted to rest on the bars. I felt like I was reaching just a bit for the hoods, but felt natural with my hands just ahead of the forward bend, about 2 cm back from the hoods.

I got a 2 cm shorter stem, moving the bars to meet my hands. Felt great after that.

2mm shorter? Where did you find this?! AHha

Probably the same place where you saw someone say "2 mm".......

This seems backwards to me. I have Shimano 9 and Campy 10 and the Shimano shifters have the longer reach.