You got the Grid Trail. That casing is thicker than the Grid and Control casing. The Control I believe is the lightest casing. I have the 2.35 GC in the Control casing and the 2.4 Purgatory in the Grid casing. At my 145lbs...I use 16F and 18R. I also have some Maxxis DHF 2.5 and Dissector 2.4, with the alphabet soup casing. I think its the lighter trail casing. I run about 2 psi less than my Spesh tires.

Both sets of tires are on i30mm rims.

You can experiment running lower pressures. "Our GRID TRAIL casing is a step up from GRID with more reinforcement, delivering better handling at lower pressures."

 

Thicker tires have more support from the rubber, and absorb more energy as it flexes. This means they need less support from the air inside of them, which means for a similar "level of support/feel", they need less pressure than a thin tire casing (which derrives more of its support from the air inside of it, rather than the rubber).

The most compliant ride/energy efficient ride is going to come from a thin tire casing and supple tire. This is basically what road racers do, they want as thin/supple a tire as they can, so it can waste as little energy from deformation/etc as possible. Mountain biking deals with impacts though (or, a heck of a lot of them compared to road riding) and this is why as trail speeds increase, and the size/force of impacts increase, we get thicker and thicker tire casings to give more support/protection from impacts, without needing like 100PSI.

So thicker tire casings are good when you want impact protection from things like rocks/roots/etc that would damage your rims. But that extra energy means that it takes more energy to pedal around. Which means people tend to try to balance their tire casing thickness with their needs. If you're needing incredibly high pressures in your tires to keep from damaging your rims/keep the tires from squirming in the corners, or getting lots of punctures its worth going up in casing thickness. Conversely, if you feel like you're pedaling around boat anchors, and running super low tire pressures, you might be able to get away with lighter tires.

 

+1 on what ocnLogan says.

Next to that, your inner rim width vs your tire width plays a role as well. As that also defines the tire pressure you can ride, plus the support that the tire gets from the rim. Typically you want your tire/rim width ratio as close as possible to 2:1. In that case you can ride a thin casing still on low pressure without the squirm. And is the need for a thicker casing less needed.

 

Which Vittoria tyres are you used to? I have Mezcal XC Trails on my hardtail, and a Purgatory Grid T7 and Ground Control Grid T7 on the FS bike (BTW the Ground Control doesn't come in grid trail, only grid). The casings feel pretty similar to me, but the rubber on the Spec tyres feels softer.

You can try lower pressures for sure. The pressure difference between your front and rear tyre seems massive to me.

 

Yep, back off the pressure 2oai for a start.

I agree with Holly. 7psi between front and rear is massive. I'm usually 2 to 3 pai different.

 

Yep, back off the pressure 2oai for a start.

I agree with Holly. 7psi between front and rear is massive. I'm usually 2 to 3 pai different.

Not sure if it is my setup or riding style but I can get away with lower pressure in the front but not the rear. When I start dropping the rear it gets squirrely.

 

Don't just back off a little on your pressures. Back off in steps until you get a rim hit going through the trail segment with the most difficult surface. Take a gauge and hand pump with you.

 

I'd lower pressure until I reach one of:

1. rim strikes per above
2. the tyre doesn't support you, and gets "squirrely" as you describe

 

In the road riding world, suppleness is affected by the threads per inch. I don’t know how that translates to the MTB world, but the Mezcal XC is 120 tpi while the Ground Control T7 is 60 tpi.

 

OP - Also keep in mind T7 is a more durable rubber. I tend to use their T9 on the front for the best grip and the T7 out back for better efficiency/durability.

 

I guess I’m on the fringe with a 10psi difference front to rear? I run my tires at 12psi front (DHF 2.5wt MaxTerra exo) and 22psi rear (Eliminator 2.4 T7 grid trail) on 30mm rims. That’s the absolute lowest I can go in the back without strikes, and to me the front still seems a little too bouncy at 12psi. 185lb rider too so I’m not a tiny person.

My point is that looking at it on paper is all subjective, the best way to get it dialed is ride and experiment. I bought a nice pump with a gauge accurate at low pressures to help dial it in.

IMO, higher volume tires let me get WAY lower than I was used to in the narrow rim 2.2 tire days.

Terra Floor Pump

In 1988 SILCA noticed the growing MTB market in the US and began developing a high volume pump with low pressure gauge to meet the needs of this completely new category of bicycle.Named the Terra, it was the first of it's kind, high volume, low pressure specific pump for larger volume tires...

silca.cc

 

I guess I’m on the fringe with a 10psi difference front to rear? I run my tires at 12psi front (DHF 2.5wt MaxTerra exo) and 22psi rear (Eliminator 2.4 T7 grid trail) on 30mm rims. That’s the absolute lowest I can go in the back without strikes, and to me the front still seems a little too bouncy at 12psi. 185lb rider too so I’m not a tiny person.

My point is that looking at it on paper is all subjective, the best way to get it dialed is ride and experiment. I bought a nice pump with a gauge accurate at low pressures to help dial it in.

IMO, higher volume tires let me get WAY lower than I was used to in the narrow rim 2.2 tire days.

Terra Floor Pump

In 1988 SILCA noticed the growing MTB market in the US and began developing a high volume pump with low pressure gauge to meet the needs of this completely new category of bicycle.Named the Terra, it was the first of it's kind, high volume, low pressure specific pump for larger volume tires...

silca.cc

Props for the high quality pump.

I’m interested in what you mean by bouncy??

I’m also interested in what pressures the Wolf Tooth pressure calculator recommends

is it possible that your fork isn’t well set-up or has a serious issue?

 

My question is by running a thicker casing should this allow for lower air pressures? If so what gives a more compliant ride thin casing and higher pressures or thicker casing w/ lower pressures?

Depends on how fast you're going and how much you weigh. You can think of it like a spring and damper system (because it is). The heavier casing tire has more damping. Supple tires work best for lower speeds. As speed increases you need more support. Increasing air pressure will give you more support but you end up with a high spring rate (pressure) to damping ratio. This will feel bouncy, harsh and uncontrolled. This is where a heavier casing and a bit lower pressure will feel less harsh and more controlled. So it's an optimization thing where you want to match the tire casing to the type of riding you do.

I'd drop the pressure in your new tires and see how low you can go. If they end up feeling too heavy, slow and dead you'd probably be better off with a lighter casing.