I have a 2014 Surly Pacer with Shimano 105 components that I want to convert to a flat bar set up. Any one out there with some input regarding flat bar handlebars? I've looked at SRAM and Thomson. Is there much, if any, difference in comfort between aluminum, carbon fiber and titanium? Also, what rapid fire shifters work with the 105 setup? I appreciate any input. Thanks.

You'll probably need new derailleurs that match shifters. I converted my wife's sora bike. I used sram mrx comp twist shifters. They are the only ones I found that are compatible with road derailleur and even such the front shifter only works as friction shifting. Not ideal but it works. Mountain bike and hybrid shifters have different cable pull than road derailleur.

Let me google that for you This question is asked at least once a week...

What makes you think a flat bars are going to be more comfortable than drop bars given the geometry of the bike won't change?

To be fair OP never mentioned anything about comfort other than asking if carbon, alum or titanium bars would be more comfortable than another.

But seriously, Pacer with 105 is a nice bike. If OP wants flat bars I would sell that bike and buy a hybrid. Probably get enough in the sale of the Pacer to pay for a decent hybrid as they are cheaper than road bikes

I admit I did infer from his question about the comfort of different bar materials that the driving force for the conversion would be to make the bike more comfortable to ride.

Which, in the absence of geometry changes, it probably won't. In fact, there's a good chance the loss of multiple hand positions on the current drop bars will make the bike less comfortable.

Thanks to all for the input. Regarding the material used for the handlebars, it was in regards to whether or not one material was more comfortable than another. I am a newbie trying to find my way in all this. There are so many choices no matter what component you are discussing. My thoughts re the flat bar was that it made sense to me that a more upright seating position would be a bit more comfortable. But I know nothing about frame geometry as it relates to seating position. I've much to learn.

In response to the thought that loss of multiple hand positions available on the current drop bars would make the ride less comfortable, are there those out there who have made this conversion and found that that thought to be true? For myself, the drops are never used and the flats, because I'm pretty broad across the chest and shoulders, are too narrow. I don't feel in control when I'm on them so I'm basically on the hoods all the time.

The point of hand positions is that when you start riding longer distances you'll need to change positions to stay comfortable. Drops give you at least 3 positions.

It's possible your bike just doesn't fit you right or it's possible that you just need to ride more and get your body conditioned to riding the bike. Did you buy the bike form a shop and get fitted by them? If you want to be more upright you there are some changes like flipping stem to face up (if not already) and/or putting more spacers beneath the stem to raise the bars a bit. Drop bars also come in different widths. Most bikes are sold with something neutral like 42 cm that will work for the greatest majority of people but if you have very broad shoulders you might need wider set of bars. The hoods are where most people spend most of their time. That gives you a neutral wrist position that will be comfortable for long ride. I like to ride on the flats of the bars when I'm doing long climbs or long flat straights (basically times when I don't have to worry about turning or braking)

I would look to fine tuning the fit, and getting a wider set of drop bars before going to the considerable expense of switching to a flat bar. And if you can't get comfortable on your Pacer, sell it and buy a hybrid.

I was not fitted in the bike shop, no. Not other than seat height. The bike was ordered. There wasn't one in stock. Tweaking the fit sounds like it should be my first option as the cost of the conversion is pricey, given how much I already have into the bike. Raising the stem to attain a more upright seating position makes sense. I'll look into the wider drops as well. Thank you very much for the input.

A more upright position can be more comfortable - that's for you to find out.

But a more upright position comes from bike geometry and how the bike is fitted - saddle height, saddle fore/aft position, stem length, stem angle, bar height, even bar width. Unless it's really wide, a straight bar is going to be pretty much the same as being on the tops of drop bars, only with your hands wider.

Don't worry about what anyone else is riding. Everyone is different. This is probably the best "bike fitting" summary out there:

How to Fit a Bicycle

I don't know of anyone who has converted a drop-bar bike to a flat bar and regretted doing that because the bike became less comfortable - in fact, I don't know of anyone who's done that conversion at all. But I do know a LOT of riders who started with flat-bar bikes and moved to drop-bar bikes because the flat bar became uncomfortable on longer rides.

But then there are some who can ride a double century on a flat bar bike with no problems.

Here is a list of the things required to convert to flat bar...

Handlebar - Carbon or Titanium has the best feel, steel next, aluminum last.
Stem - your choice but you'll need a new one as your position on the bike will change.
Grips - Ergon's GP series are awesome. Highly recommended.

Now for the fun stuff.

Shifters - Since you have road derailleurs, you need to run the Tiagra shifters (Product)
Brake Levers - Shimano Tiagra levers will allow you to adjust for the pull of a road caliper brake (Product)
All cables/housing on the front of the bike will need to be replaced.

I've converted a few bikes like this, including my wife's Madone 4 series, after she had a pretty serious bike accident. It works perfectly and is so much fun to ride! As stated above, fit is the most important thing for comfort, and regardless of flat or drop bar configuration, you'll want to address any fit related issues first.

Everything I've ever read has stated that the Tiagra road shifter works better paired with a mtb FD, although the only official word from Shimano is to use the matching FD (FD-Rxxx). I've read plenty of posts in which someone was complaining about the road/drop FD not working with the Tiagra flat-bar shifter.

I've personally built several of these conversion, most recently with 5700 105 Front and Rear Derailleurs and the Road FD shifts perfectly paired with this shifter set. There is a trim click that mimics the one found on the STI shifter which could cause some issues if not setup correctly. I actually find it a bit smoother shifting on the FD if anything...

Since I just finished my EM build, I got bored and started to mod my Nishiki. Went with whatever bar I had laying around (in this case, a butchered 48cm aluminum bar). As for shifters... friction goes with everything.

Thanks for the link on How to Fit a Bicycle. My current drops are 42cm in width. In talking with my LBS, and taking into account my shoulder measurement and need/desire to sit a bit more upright, I'm going to alter my drop bar setup by using 46cm width drops and increasing the angle of the stem and see how that works out. Thanks again to all for your input.

My thought too. Some people want to be more upright, but I suggest keeping the bars and get a riser stem if that's needed.