Road tyres vs "Street" tyres for charity ride on MTB Tandem Variation on a question that's been asked a few times.
For reasons, we have signed up to do a charity ride of ~80 miles on our super-cheap Viking Saratoga tandem. I've already made a few upgrades, mainly ergonomic, but was wondering whether I should bother changing the tyres.
I realise conventional wisdom dictates &quot;slicks&quot; rather than &quot;knobblies&quot; for riding a MTB on the road, but the tyres currently fitted are Kenda Kiniptions in 26 X 2.3&quot;, which the manufacturer describes as:

Excellent tire for urban assault or skate park use; equally versatile on hardpack race courses
Diamond shaped knob design wraps from bead to bead for sidewall protection and grip from all angles

We run these pumped all the way up to the recommended maximum of 80psi.
Now, I'm all for &quot;marginal gains&quot;, but the bike is already pretty heavy, so I'm not sure that lighter weight tyres would make things much easier - I think any potential improvement would be in rolling resistance.
Is there any tire around that would be a useful upgrade in speed? The rims are drilled for Schrader, so if Presta tubes (to allow higher pressure) were part of the solution, I imagine this would require some fiddly adapters.

UPDATES:
The rims are unbranded with no markings, so no idea of max pressure.
2 punctures in 50 miles a couple of weeks ago, and I have changed both tyres for Marathon Supremes. This has made an appreciable difference in cruising speed, more than I anticipated.
It's not the weight of knobblies that's the issue, but how much effort you have to put into deforming them with every rotation - the rolling resistance. The tyres you've got are certainly going to be slower than a wide semi-slick, like many touring tyres, but they'll be a lot faster than tyres designed for muddy trails. The ones you've got don't actually look too bad for road use. 

If you're going to make a habit of riding this bike on roads for decent distances, a tyre upgrade might be in order - you could gain puncture protection as well. As it's a tandem, note the weight recommendations on potential new tyres. 

Overall I suggest you run with what you've got, and if you think "that was good but I'd like to be a bit quicker next time" consider an upgrade. 

BTW Presta tubes don't inherently allow higher pressure, though they're more common on rims rated to higher pressure. Adapting is easy with a grommet but of no benefit to you.