Witterings

What would most people run their tyres at for 60% road / 40% gravel on a 29er if you just want to leave them at one constant pressure rather than adjusting for the different surfaces.

The gravel tracks are all fairly flat terrain with longish turns without any real bumps / roots etc, up until now I've kept them around the 50 psi for better road characteristics and am going to experiment a bit but thought I'd ask others 1st.

Hondo Gravel

I run my 29er at 50 psi for paved roads and gravel. 35-40 psi for off road. I tend to like higher air pressure than most riders.

rumrunn6

FWIW ... I don't have a 29er, but I adjust pressure based on expected terrain. & I have adjusted pressure mid-ride when trails have changed significantly

Kapusta

I guess it would depend on the tires.

Bigbus

What size 29rs are you running? On my 27.5- 2.25's I run around 35psi and on my 2.35's I run a little higher, more in the neighborhood of 50psi, especially if I expect to be on more hard packed surfaces that day because the larger tire absorbs more terrain than the narrower tire and as we all know, higher pressure equates to less rolling resistance.

Witterings

The tyres are Smart Sam Plus 2.1's

Bigbus

You will definitely notice a difference in handling on the gravel with that narrow of a tire if you lower your pressures. I would experiment by starting at 30 on a sidewalk near you and see how it feels. Once you find the lowest pressure that doesn't create much drag on a hard surface, it will probably be the best pressure in the gravel for you. 50psi must feel real squirrly in loose gravel with that narrow of a tread. Especially considering your tire height (29).
Of course, these are my thoughts based on real world experience for me. What works for some is ridiculous for others.
Good luck.

Kapusta

Huh, that is a tough one. If these were slicks (or semi-slicks) I would say run them much lower than you are currently, as you would likely lose little (if any) speed on pavement but gain a lot of traction/comfort on gravel.

However, looking at that tread (with the continuous center tread that give way to widely spaced knobs just off center), it looks like the lower you run the pressure, the more you come off the consistent center tread and on to the widely space knobbies which will slow you down a lot on pavement.

You are just going to have to experiment with lower pressure and see what happens. There is really no way to know or predict without experimenting.

Witterings

Certainly as you say there is the center thread designed for less resistance on road and theoretically making it a good tyre for mixed riding ... I guess it's just balancing the comfort off road against the resistance on road, I've dropped them down 10 psi to 40 so will see what difference it makes as I'm out tonight and glory be no rain predicted .... a 1st here for a while

Kapusta

Yes, I think you are right, it is a good design for mixed riding, if that mixed riding includes some particularly soft, muddy conditions, or some small loose stuff.

RubenAlonzo

im at 35 for my Scott Aspect 970

manc

Why does nobody mention rider weight when talking about tyre pressure?

roccobike

On packed gravel I run max pressure on 29ers,. around 60 to 65 PSI. It's all about speed on something that smooth. I'm running a 2.1 Michelin Wild Racer on the rear and a 2.2 Specialized Fast Track on the front.
On loose gravel, I'll lower the pressure to around 50 PSI, but take into account that the only loose gravel trail around here has some climbing so the lower pressure is needed otherwise I'd ride it with more pressure. On single track, I try to run at around 35 PSI on tubeless, 40 on tires with tubes.

Kapusta

Because this is the internet and you don’t need to have a clue what you are talking about to post answers to questions.

Talking about tire pressure without talking about rider weight is like talking about shoe size without talking about the size of your foot.

dplevy81

Are you running tubeless?? If not, you definitely should be. with tuneless tires 30lbs ish is a good all around number for someone my size (175lbs) at least.