tyres - MTB vs commuter/slicks

I've got 27.5" MTB knobbly's which came standard on my MTB (Schwalbe Rapid Rob). I spend most of my time riding on paved paths and roads so the MTB big knobbly tyres are probably losing efficiency.

However, I'm curious what would happen to my top speed if I swap them over to commuter/slick tyres. Obviously they will be more efficient overall generally, but they will have a slightly smaller rolling diameter than the large knobbly's.

which will likely win out, the improvement in efficiency/reduction in rolling resistance or the reduction in rolling diameter, or do you reckon it would be negligible and I'm being pedantic!

thanks

http://www.ebikes.ca/tools/simulator.html

Be sure to adjust the vehicle parameters settings to simulate a slightly smaller but better CR along with a slightly larger tire but with worse CR.

My personal experience was not much difference. The aero resistance is the killer, but smooth tyres are a nice ride on the perth bike paths imho. I put on conti tourers with thorn proof tubes as my rapid robs seemed a bit thin.

You should see a nicer feeling ride on the pavement without the knobs. But much better efficiency would require riding slower, with less air resistance.

For example, the racing tires used by the guys in a big bike race will coast wonderfully, and they will hide from the wind in the peloton most of the day. They will see a huge difference if they switched to a tire with more rolling resistance. The key thing here is they are hiding from the wind.

But you have your motor, and more power than most race sprinters put out, and no hiding from the wind. Rolling resistance of your tires is now a very small % of the equation for you. However, if you still want some knobs for the occasional dirt road, and a smoother feeling ride on the street, look for a knobby tire with a solid rib down the center of the tire. it can zig zag some, but look for a rib. This will help it roll easy when you aren't leaning the bike on pavement.

On my lontail cargo bike, I just find a balloon type beach cruiser tire works fine for me. it has some short knobs, for moderate riding on dirt roads, but still rolls smooth.

I have used Schwalbe Mudy Mary and Crazy Bob tyres and I really liked the Crazy Bobs on pavement. Smooth ride good cornering and some dirt was also possible (not for mud)

Edit: not available in 27.5 sorry

Looks like you ride a hardtail. I get a lot of comfort from my balloon tyres and they have quite a rolling circumference. They are designed with running soft in mind, so put a lot of rubber on the ground. This seems to be helping with their endless mileage. The big apple is the common one, so there is some keen pricing to be found.

iirc they rate rolling resistance 1-5 and these are in the right fifth. Surprising for a big tyre. Very supple. I find forest trails no issue in any weather. It has to be fairly extreme for me to loose grip. Which is usually nailing it up a slope most people push their bikes up. Getting a bit of wheel spin in the process is something I consider fun.

I agree with dogman. I seldom approach the range of my batteries, so efficiency is not a big deal.
And, it's been my experience that changing tire sizes(not whl. size), doesn't change top speed that much. And I don't run at top speed anyhow.
What matters to me is ride and handling, and flat resistance.
On the pavement, far and away smooth tires are better as knobbies tend to squirm around.
But right now I am battling flats, almost always thorns.
I have tried about every combo of tires, tubes, extra thick and Slimed and the best combo for me is small, tall knobbies with a quality extra thick tube.
The thorns won't go thru the knobs and all the way thru the extra thick tube and the remainder of the tire surface doesn't really come in contact with the riding surface and doesn't pick up the thorns.
To run smooth tires, I need to go with Slime and\or tire liners and I don't care much for either.
So for now, I run semi-knobbies and live with the squirminess.
The thorns and thrash in the road is mostly a result of the monsoons flooding the roads and I am hopeful in another month or two, the roads will be clean and I can go back to my CST Cyclops I perfer.