[TurnerCzar]

In a couple of weeks ive got a 45 mile race which is very hilly and am unsure of what tires to use , either Bontrager xr2 2.3 team issue front , xr1 2.2 team issue rear or Vittoria Barzo 2.35 g+ front and Mezcal 2.35 also g+ rear .
The Vittoria pair have a bit more tread but are they going to roll as fast as the Bontrager pair ???

 

[eb1888]

What inner width rims?

 

[Schulze]

I'd do Terreno G+ 2.1 rear, Mezcal 2.25 or 2.35 front.

 

[TurnerCzar]

23 mm

 

[eb1888]

23 means you will want more pressure. Nino uses 30mm and can run less pressure to get a lot out of tires like the XRs - he uses Maxxis now. XRs are designed by Frank Stacy for wide rims. I use 30 for the 2.2 at 14psi front or 18 rear. For a 2.35 I'd like a 35mm and try 13 or less front depending on rim hits. Wheels are expensive so I don't yet have that.
If you're running higher pressure for your rims you can look at the new XR3 2.4. It has a fast rolling low small knob center with a higher knob outer row. Depends on your terrain.
https://www.trekbikes.com/us/en_US/...m-issue-tlr-mtb-tire/p/27917/?colorCode=black

 

[LyNx]

You didn't mention what the actual terrain/trails are like :???: What's the trail surface like, is it going to be strictly hard pack, loose over hardpack, soft and sandy, more dirt or sand/silt based, rocks and/or roots, could it possibly rain??? :???:

If it were me and I didn't know what the terrain or conditions were going to be like, I'd opt for the slightly more aggressive Vittoria combo and be confident in knowing that they will handle a wide variety of trail conditions and even some moisture.

 

[TurnerCzar]

It's firm fireroad climbs and grippy rocky decents and the weather is looking pretty good

 

[jimPacNW]

fwiw I have 2.25 Mezcals fr and rr on my fs, it was very fast in our early winter/spring series. Those really do feel remarkably fast especially on hardpack and pavement, - I would run a pair of Mezcals if it won't be wet.
Just anecdotaly; I'm not a 'strong' road rider (within the group I mtb and cx with), but I think I got a 4th on a paved strava segment in our first mtb race of this season, -surprising to me given that road is not a strength for me, 2 retired (B) pros in the 1-3 spots, I passed a buddy on that road segment who can always drop me when we do road bike rides. I've been cynical about rolling resistance, but I'm now a believer in the Mezcal.