I just started commuting with a mountain bike with slicks, and have been spinning through gears. LBS said I can increase chain ring from 42 to 44 teeth. Would this be worth the expense for the performance?

I'd be tempted to go even higher. If it has a Shimano front derailer and he said that because it is rated for 44, it can actually handle at least two teeth more. You'd feel more of a difference going up to a 46 than you would just going up two to 44, which I suspect you'd hardly notice. It's quite likely you could move up to a 48 without changing front derailers too.

Of course, the other thing you can do is change the rear cassette. If it isn't an 11- something, you can get more high speed cruising by moving to a cassette with an 11 tooth cog as its smallest.

I have one bike with 44 and one with biopace 48 and there is definitely a difference. The thing to keep in mind is what your primary terrain is. If you have flatter terrain or extended downhills, the higher gear can have an advantage. If the hills are sharper or steeper a 44 will be decent. The place where the higher gearing can be nice is descending hills. A couple mph faster on the top end if your legs can push it.

No. That's only a 4.8% increase in your top gear. By comparison, if your two smallest rear cogs have 11 and 12 teeth, that last jump with your current gears is an increase of 9%. So moving to a 44t chainring would be like adding only a half gear more.

What pedals and shoes are you wearing? Do you have any idea what your cadence is? I would expect your top gear to be about 99 inches, which would put you over 26 miles per hour if you spun at 90rpm. 26 mph is plenty fast for most commuters (double what many of us average). If your 99 inch gear isn't enough, I think your first step is seeing if you can increase your cadence -- it sounds like you're either very strong with a really fast, clear route or you're not spinning the cranks very quickly. Clipless pedals and cycling shoes are IMO the easiest way to facilitate spinning.

It would make more sense to replace your crankset (which I assume is something like 22-32-42) with a 26-36-48 crankset (plus get a correspondingly longer chain) than to merely switch to a 44t big ring. Moving to 26-36-48 would increase your top gear by 14.3%, nearly as much as adding two higher gears.

That's less than a 5% increase.

Wow...great info. Darn--just bought a new chain too. Can a chain be extended or just buy a new one?

Plug the numbers into a gear calculator, like Sheldon's. That should give you a better idea of what type of (if at all) upgrade would be practical for your goals. My OEM is 42x11 on 26x1.5" slicks and I still can't spin fast enough to hit top speed. I can cruise at 20 mph with minimal effort- assuming the wind, traffic, and stop lights cooperate .

Next cassette , get one with an 11t High gear, if you can.. that will up your top gear.

Definitely change the cassette instead. It makes a world of difference. I'm running a 34-11 9spd cassette with a single 39T drive chainring and I can't spin it out in 9th unless going down a very steep hill and that puts me at around 30mph which is getting too fast IMO. the 34 makes climbing easier.

I'm swapping out a 42/52 double to a 36/48. Rear cog is 12/34. That should make a huge difference. But from 42 to 44... I wouldn't do it unless I just happened to have a 44 in my bin.

This! Its all here in this answer. A big top gear makes it fun to blast downhill, it should never be used for level ground cruising. Spin, spin, spin...

I have a big ring of 45t and a center ring of 42t so I see the comparison every time I shift and in your case I don’t think the 2t change would be enough to notice. In my case I have a wide spaced cassette that gives me maybe a 10% jump between gears and having that slight change in between fills the gap. But if I only had to have one it wouldn’t really matter much 42 or 44.

The suggested crank replacement above sounds like a better way to go.

I had a 42 on my commuter mtb. Hated it. Changed out for a new crank with a larve 48 and its great. I don't use the top 2-3 gears often, but its good to have them. I noticed that a 21 speed drivetrain benefits a lot more than a 27.With the overlap between the middle and large rings I often forget which chainring I'm spinning unless I meet a long downhill.

I run a 10-speed 46-38 Cyclocross front and 9-speed 11-34 cassette. It works great for ALL terrain...especially the flats.

I just found a 48/36 crankset to replace the ancient 1982 swaged 52/42 on my commuter. That kind of range is pretty good on flats, but it also depends on the rider, weight of the bike, road conditions.

I know I very seldom got to use the 52 chain ring...

I'd be tempted to track down one long enough that when you made it small enough for your new set-up you'd have enough left over the lengthen the one you have. Some places that sell chains online list the lengths. You'll need a new chain in a few thousand miles anyway. Better to replace the chain as soon as it is worn rather than have the worn chain wear out the more expensive cassette and chainrings. If you don't have one, you'll need a chainbreaker, which is a good tool to have anyway, and a masterlink. I tend to carry a chainbreaker (as part of a multi-tool) and a spare masterlink anyway.

Our road tandem had a Truvativ Elita Triple (30/42/52) and a 9sp (12 - 27) cassette. Tandems aren't the best climbers because of the difficulty in getting out of the saddle. A 26T granny would have been an improvement but I figured as long as I was going through all the trouble why not a 24T. An FSA 24T has graced the inside position of our triple crankset for a couple of seasons. The rear cassette is unchanged. The 24/27 is more than enough to get up the steepest hills. A 24/32 IMO will require some super fine bike handling due to the extremely low forward speed from that low a gear. Or are you riding a tadpole trike? Mind you, our 24/27 is turning a 700C wheel so the resulting gear is even higher than if you used the same combination. If we can spin that, so can you.

I don't know where you are from but the "accepted" way of expressing gear ratio's in most of the free world is "gear inches". A lot of information was conveyed just by stating the chainwheel tooth count and the rear sprocket tooth count but to seal the deal you compute the gear inches and look like you really are a gearhead. The Sheldon Brown calculator can help. Nice post anyway.

H

Putting a handkerchief under your helmet would be a good idea on those hot sunny days...