Hybrid commuter to casual MTB

[Twilkes]

I used a Kona Dew for commuting for years on 32mm slicks at 90psi and it was fine for that - if I put some bigger rugged tyres on it would it serve as an occasional off-road bike? Currently it digs a trench into anything except hard ground and doesn't cope with stones/gravel at all, tyres should help with that but it's also quite high and upright - would MTB geometry be much different? What size tyres should I go up to if I want to ride it on roads to get to a trail, i.e. mixed use?

https://2014.konaworld.com/dew.cfm

 

[CanucksTraveller]

f I put some bigger rugged tyres on it would it serve as an occasional off-road bike?

Yes, it's absolutely perfect for it.

would MTB geometry be much different?

No. What you have is perfectly good for riding muddy tracks, it just has the wrong tyres at the moment.

What size tyres should I go up to if I want to ride it on roads to get to a trail, i.e. mixed use?

Whatever the clearance allows, maybe have a chat with your LBS on that, or check the Kona website spec to see what the max clearance is, and go with that.
Lower your pressures when you feel mud is on the agenda.

 

[Shreds]

32mm slicks.....digs a rut?

Most bikes will do so in soft mud but on gravel....I would be happy with 23mm. Of course a lot depends on other factors such as looseness of gravel, rider weight and speeds. Can you enlighten us?

 

[Twilkes]

Sorry, sinks into anything remotely soft, bounces off stones/gravel. I'm guessing the latter is just the high tyre pressure but if I'm going to buy new tyres I'll probably get something bigger that naturally runs at a lower pressure, rather than running thinner tyres at a lower than recommended pressure.

100kg.

 

[Shreds]

Good on the weight...... Schwalbe do a range of knobbly cross tyres as do other manufacturers. Good ones are not cheap though.

Whether you could adjust your v brakes to accomodate other wheel sizes I dont know?

Managed to use smaller differing ones provided there is clearance on 700c bikes and they have disc brakes but thats a whole different ball game.

Just run the tyres at a slightly lower pressure and they should be ok, even if they wear faster and are more prone to punctures.

 

[rockyroller]

the wider the tire, the more flotation you get. I like having 3 bikes, road 25mm tires, hybrid 45mm tires & MTB w/ 2.25" (57.15mm) wide tires. & I can make use of even wider tires! it's like deciding what kind of shoes to wear after looking out the window. aside from tire size tho is tread & pressure. it's amazing the differences all those variables can make

related: big fan of buying pre-owned stuff except for tires

 

[SkipdiverJohn]

It's the unit ground pressure that determines how much sinking into surfaces will be a problem not tyre pressure. That depends on rider weight, bike & luggage weight, and weight distribution on each wheel. All things being equal, a rider & bike weighing twice as much as another rider & bike needs tyres twice as wide. It's pretty much a non-issue for light riders, especially kids - since smaller bikes ridden by lighter riders have proportionally wider tyres. As you go up the frame sizes, and the typical rider gets heavier, the tyres get proportionally narrower in relation to the load they are carrying.
At my weight of 14 stone plus bike, so a 16+ stone overall tyre load. I find 2" wide MTB tyres the only practical size for riding dirt & grass surfaces after wet weather when the ground is very soft. The OP plus bike is going to be at least 18 stone, so even worse!
With rough but firm surfaces, tyre sizing is just a question of rider comfort and safe loading limits, not getting bogged down. I doubt the OP will be able to cope with soft mud on that bike at their weight irrespective of tyres. Compacted stone & gravel it will cope fine with so long as the tyres are tough enough.