Did a Retul fitting on existing bike and it said I should go from 42cm to 38cm width on handlebars
I am 5'6" on a 52cm Trek Madone 6.2 with H2 geometry from 2 years ago
While the 42cm was too wide and made the bike feel too big I am not sure the 38cm I had installed is right either
Seems to line up shoulders square (rather than using the 42cm where my reach was too long) but also feels like I am compressing my shoulder muscles and arms may be angling inwards towards front wheel
I am more aero but not sure if I just have to get used to new position or it is really too narrow
Feels good in drops but when sit up cannot get hands in comfortable position on top of the bar (hands don't seem to fit without the outside of my palms pushed up against bars as they curve out to brake hoods)
My old Madone has 40cm and fitter thought shoulders still where angled outwards
Any thoughts?
How do you know what right fit should feel like?
Maybe what I was used too was too big and this is actually correct but will take getting used to

Ride what is comfortable. Maybe try a shorter stem on the 42cm. There is some aero advantages to skinnier but also some lung capacity i'd imagined from the wider bars too.

There is no law saying your shoulders/arms must be square! Go with the width that is most comfortable for you. If your saddle position/reach is correct then a couple cm on a handlebar is not going to hurt your fitting on the bike.

I'm a big rider. The theorists tell me I should be riding 44cm bars, maybe even bigger. Actually I prefer 40s, or 42 max. Nobody can tell you what will feel right to you.

Having said that, unless you feel your breathing is restricted because your chest is closed I'd give the 38s a try for a while if I were you. You might find that like me, you come to prefer a slightly narrower position. If after a few weeks you still don't feel right, move up to a set of 40s.

Thanks
Not sure yet if I feel breathing restrictions (chest is definitely tighter than on 42)
Biggest difference I noticed from comfort standpoint is hand position (feeling pointed in on hoods and no good place to put hands when sit up to climb a long hill)
Just checked and my old Madone and older Trek 2200 both have 40cm; always felt ok on those
Part of going narrower is hands were too spread out and wrists being restricted in drops
But now feel a little handcuffed when riding on hoods

"Chest restriction" has very little to do with bar width (unless its ridiculous narrow). It's more on how you position your arms.

Most are rules of thumb. A starting point for most. I went from 42 to 38 c-to-c. Won't ever go back.

Why did you change and what do you like about it?
Did it take time to get used to it?
Any issues at all?
What is geometry of bike and your size to see how it compares to me?
Thanks

So really, what's keeping you from trying a 40?

I did the fitting and just had the 38cm installed
Spent $300 on bars and $90 on install
Not ready yet to scrap that to go with 40cm to compare
On fit bike for short while it takes to do fitting and not moving felt good; but out on road think I am too narrow
Wondering what to look for as comparison points
Feel more in control of bike at 38 and more aero
But not sure about hand positions and if I am too narrow to breathe properly and really be able to push it on bike
Does anyone else have issue when sit up not being able to be comfortable with hand position but wanted narrow bars?

How long do you give a new change to bike fit in order to figure out if it is working?

I'm 5'8" 140lbs. Ride a 54cm Cervelo.

I test rode a bike with 40cm bars. To me it felt better almost immediately. My arms did not feel as spread out on the hoods. I did not lose any leverage when out of the saddle.

Only thing that I had to adjust to was the bike felt a bit twitchier at fist. I noticed it the first time I took my hand off the bar to reach for my bottle. It didn't take long to get used to it.

You need to trust the fit. Your body needs to get used the the new position. Give it a couple hundred miles.

Thanks for the feedback
I rode it again today and still feel narrow. Hands don't fit comfortably on top of bars and on hoods I feel my hands drifting to a more natural position which is outwards (almost like outer edge of thumbs on outer edge of hoods-or what another 1cm on each side might be)-also felt breathing was better in the wider position (or am I imagining this?)

Problem is that in drops I feel good

This change really started from being too wide at 42 and getting wrists caught in drops-plus not being able to reach brakes from drops

Fear if I go up to 40 I will have this issue again

What if I go to 40 and go with shorter stem and or turn bars up a drop-will this compensate for the wider bars so I don't have to reach so much?

I really wouldn't advise you to do this. You've just paid for a fit. You've given no indication that you are unhappy with it, other than suspecting that your bars might be a little too narrow. If you start messing about with stem length you're going to change how you are sitting on the bike, which presumably was the point of the fit in the first place.

I'd suggest going back to the guy who fitted you, tell him your issues and get him to take another look.

You already own two sets of 40cm bars, you said that they were comfortable, so swap one of those onto the new bike and try. If it's more comfortable than those shiny, expensive 38cm, you need to choose between comfort and shiny new. You could even buy some shiny new 40cm bars and E-bay the 38's. This isn't that complicated.

Finally, some sense.

I could probably swap the 38cm back for shiny new 40cm
Looking for feedback based on experience of what I should be looking for it the width fit and how long to give it to make this decision

I am far too big for this sport, I think, with my 60cm frame and 46cm bars.

If you went from 42 to 40 on a test ride and it felt great why did you go down to 38?
thanks

The old school of thought was to go narrow for more aerodynamics, then it was to go wider to open your chest so you could breath better, now it's who cares it doesn't matter! they both work the same, some pro riders chose one over the other simply due to how they like it. So go with what you like.

How hard is it to swap handlebars back and forth to compare the 2 widths?
With the tape and brake hoods/levers it does not seem like a simple thing

There is a lot of talk in this thread regarding handlebar width. The fact of the matter is that manufacturers measure their bars differently. I purchased a BMC SL01 that came with so called 40cm easton bars. The 40cm is measured at the bottom of the drop. In reality they are only 38cm cc at the top of the brakes. I needed to replace them to get closer to the 42cm that I have been fitted for.

In addition to the points you outlined above, some measure center-to-center at the hooks, and others go outside-to outside, which adds 2cm or so. A measuring tape can be useful when comparing width, drop, and reach for different bars.

These were both Bontrager handlebars so I thought the standard of the 2 points of measurement would be the same

I'm 5'6", ride a 52cm Madone, had a professional fit and moved up from 40cm to 42cm bars. The wider bars felt good from day 1, for me.

That being said, your comfortable position may not be the same as me. Go back to the LBS where you got your fit, explain how it feels, and let them fine tune you. If it's a good LBS, they'll help you dial it in correctly. My fit told me I needed a 80mm stem but I felt like I was stretching in order to reach the hoods. Went back in and swapped it out for a 70mm and felt perfect. As the stem was essentially NIB, they just swapped it out for me. Note that I'm not suggesting you change your stem, but just passing along an example of how we had to dial in my fit with an adjustment...

You paid good money for your fit; make sure that you feel comfortable with the outcome.

I like my bars to be the same width as my shoulders or on my touring bike a bit wider for better control of a loaded bike. I tried narrower bars years ago and my shoulder blades would start to pain after about 50 miles.

Some people say wider bars are more relaxing to ride with, the reason for that is because it's slightly easier to control the bike which is why I use wider bars on my touring bikes. And the reverse of that is narrower bars make the steering feel quick or twitchy, some racers like that feeling.

It is difficult to compare the two or three widths because it requires the time to swap the stuff. If your comfortable now then just forget it! You wouldn't have to tape the bars until you tested the new width, if you like it then wrap it, if not then remove the bar and try another. But you would still have to remove and reinstall the briftors and the bar, but the bar is easy with the new school stems.

If you decide to experiment don't go anymore then an inch wider or narrower then your shoulders. Just don't make a change due to trends, trends are stupid, if your comfortable now then don't bother changing.

If you think your bike is too twitchy, having trouble controlling it in high winds or passing semi's, can't ride it with no hands, then look into wider bars.