fietsbob

My speed is a comfortable pace, no matter which bike I'm riding.

nobody to show-off for.

Ghost Ryder

I look @ it this way:
By the time spring/summer comes round, I'll be in better shape.
My commuter is about 10lbs heavier than my road bikes, I feel like I climb the same speed, but feel the effort is being pushed.
I'll alternate with busy streets one day, & side streets the next.
With temps in the negative, I almost take the busy roads to avoid black ice.

FBinNY 

Weight has very little to do with maintaining speed. Discounting the effects of wind resistance and tire friction, Newton's 1st law of motion applies and no power is needed to maintain speed regardless of mass (weight).

Weight (or mass) come into play when climbing hills against gravity and/or accelerating where Newton's2nd law applies.

In hilly terrain or when there's lots of stop and go, added weight is a handicap, but not otherwise.

When comparing the differences between two bikes, the biggest difference will be in riding posture which affects wind drag. The next biggest difference will be tire drag, then lastly all the other factors like bearing drag and so on, but these are small by comparison.

agent pombero

Give me a carbon MTB and i guarantee my avg speed will be higher.

FBinNY 

Years ago (decades ago) when I helped sponsor a road team, I heard this kind of stuff (not carbon, before that) all the time. The effects of better equipment are marginal and while there might be debate over whether it's 1% or more like 5%, no expert could claim anything near 10% difference.

Ghost Ryder

Anytime I climb with a MTB, I end up in a wheelie.
The geo on most MTB's just don't work for climbing.

I still push hard on my commuter/tank
Like in said it takes more effort but it pays off in the end.

FBinNY 

Think about this for a minute. mtn bikes are designed for climbing steeper hills, trails and embankments than you'd ever get on the road. They'e also geared for the purpose, so does it make sense for the geometry to be wrong.

Probably one reason you're popping wheelies on the mtn bike is that the lower gearing gives you the leverage to do so.

Ghost Ryder

Really?
Why is it that most take the shuttle up, or walk it?
I always thought MTB were built to go down hill...

I find MTB geometry has your/my weight too far back, I'm almost sitting on the back wheel. Which is great for traction, but for climbing you need your weight up front/on top of your front hub on steep climbs. I stay seated on my road bikes, & stand just to stretch the legs out, or work a different muscle group.
Back to MTB's:
The granny gear helps for climbing, but I used the middle ring to climb. I love climbing, & spent most of my 20's in the mountains.
If you didn't already notice, I'm from a place with some of the worlds best trails/mountains.

FBinNY 

The reason so many people take the shuttle up, is that they're lazy and let's not kid ourselves, going down is more fun.

Anyway mtb geometry (not counting DH bikes) is general purpose, for both hard climbing and descents. Of course no one geometry can be ideal for both, so mtb, biking skill depends on weight shifting. Road biking also depends on weight shifting, but since the slopes, bit up or down aren't as steep, less shifting is needed.

The secret to climbing very steep embankments without shifting weight way forward or standing, is very smooth pedaling style. Strong riders sometimes have a tendency to apply power in short arcs rather than long ones. That means for the same average power, the peak torque will be higher.

Decades ago, we used to do a hill climbing teaching exercise by putting an apple or orange in a bag and tying it to the handle bar. The object was to climb fast without making the bag swing forward and back. It's harder than you think until you practice smooth pedaling.

Ghost Ryder

I have to try this technique!
Sound like a sound method to improve my climbing prowess.
Thanks for the tip!

I will admit climbing with a hardtail is much easier than a FS, & even better on full rigid/old school MTB's.

jowilson

My commuter/touring bike (everyone says its a freakin' truck though, a Cro-Moly 1993 Trek 800, weighs 30-35lbs bare and loaded for touring maybe 50-70lbs. My 1971 steel fixed gear bike weighs ~19lbs and I get to school about 10-15 mins earlier, even with a few red lights to wait at. My ride is 7.5 miles and it takes me ~30-40 mins to get to school on either bike.

So yes, bike weight has a noticeable impact on time, but other factors can affect commute time much more.

cplager

Oy. Once at speed, weight plays very little role on flat ground.

The difference between your MTB and road bike, if riding on the flats is almost entirely rolling resistance and aerodynamic drag. Weight matters for accelerating and climbing and then it's only total weight that matters (you + bike + stuff).

What you're describing is drag and not weight.

It would make as much sense to say that red bikes are faster than blue ones since your road bike is red and your mountain bike is blue.

JReade

Commuting on my MTB, my Road bike, and my Steel Touring bike. All with Bags (whether on me, or on the bike), and similar routes. Not much climbing to speak of on the ride.

Roadie is the lightest, MTB / touring bike are similar weights. I would track all my rides, and the fastest was my roadie, followed by my touring bike, and then the MTB. The roadie and touring bike were within 5 minutes of each other, which is one extra red light. The MTB was about 2-3 minutes later, so maybe 7-8 minutes later than the roadie. Why? 1. I could feel the lack of any aero. I'm a giant sail on that thing, plus knobby tires. 2. Gearing- My MTB has crankset with gearing of 42/34/24, with the cassette being 11-34 7 speed. the MTB was built for rapidly varying terrain, 42-11 was the tallest, and was a lot of work on that bike. moving up a gear or two, and you'd have a theoretical top speed of 21 mph, which is spinning out that gear... I'd exhaust myself trying to hold 18-20 mph in the taller gears, but spin out if I went up a few. Street tires instead of knobbies, a little better gearing, I cold see it getting closer to the rest of the bikes, but really, I'm putting this much money at a bike to get there 5 minutes sooner?

cplager

This.

Replacing knobby tires is one of the cheapest things you can do to make yourself a lot faster. (It doesn't makes sense to do this if you really ride your bike off-road).

And if you want to keep the mountain bike, clip-on aerobars can make a difference in aerodynamics (definitely wouldn't recommend those off-road). Bar-ends can help as well (if you have them setup to move your body forward).

rumrunn6

impressive calculations. I was gonna say something similar just from my gut. the actual time difference is negligible but a lighter bike will always "feel" more spirited

acidfast7

there is probably a placebo effect going on. however, i agree that riding should be fun and if it's more fun than that's not a bad thing

cplager

Most likely this is differences in rolling resistance. I swapped out 100 PSI Maxxis Detonators with tire liners to 95 PSI Schwalbe Kojaks without liners and my average speed picked up 1.5 mph (and I can't argue that none of that is the placebo effect). The bike feels faster now.