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7am Backcountry ;- )
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Discussion Starter · #1 ·
Evening all,

Would like some thoughts on the magic PSI for aggresive XC/all mountain.

26" wheels 2.1" Continental Pro Verticals (more like 2.3" in reality)

I use 35 psi front and rear and have been doing for a while..

I read a winter tyre roundup which tested tyres at 25 psi and then 30 psi which seems low but I can imagine it would be more comfortable on the rough stuff and offer more traction?

What PSI do you go with and your thoughts on the comfort/traction VS rolling resistance. :)
 

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It kind of also depends on how much you weigh. Rolling resistance isn't as big as a factor for XC/AM than it is for road riding. You might want to consider tire pressure as more of a dynamic, that you adjust for the conditions. As you ride with different tire pressures, you can get a better feel for what will work best for you, depending on your riding conditions.
 

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I think you might notice a big improvement in cornering grip once the front tire is below 30psi, but the rear may not respond the same way and is more likely to pinch flat, so I usually run ~5psi less in the front than the rear tire.
 

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I apologize in advance for interfering in your thread but I have a question for anyone who can answer and this seems the appropriate place.

How does one get accurate, consistent tyre pressure with French valves?

I use a hand pump, compressor or large foot pump with Schrader fittings and an adaptor for the French valve.

I cut a couple of threads off the adaptor and sometimes get a reading, sometimes not. This occurs using different gauges as well.

Could it need more threads cut from the adaptor so the pump head makes contact with the valve insert? I think it touches but not sure.

Thanks.
 

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Just for kicks I tried running 50 psi on my xc bike for a couple of rides. The result was that the suspension (and the rider) had to absorb every little root and rock. On the uphill it felt to me like the bike was losing momentum on all these micro hits.

Since that experiment I've changed to a larger casing tire (2.2 race king) and I'm using stans instead of tubes. With this setup I can run 25 psi without fear of pinch flats or rim dings, and the difference in performance is huge compared with the small casing/high pressure setup. The bike glides over all those micro bumps without bucking and losing speed, and the traction is way better.

So for offroad I think that large casing, low pressure (and stans) is a win-win. Better traction AND better speed.
 

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The same principles apply on-road or off-road, in each case you want to get the tire to conform to the terrain. Obviously, on-road the bumps are much smaller, but you still can dial in the tire pressure to optimize between grip and rolling resistance.

In either case, one important lesson to be learned is that you don't just inflate to the maximum tire pressure listed on the tire sidewall. As you become more sensitized to feeling how the tires are rolling, you can adjust your tire pressure to balance out grip and rolling resistance as you desire for the terrain you are riding.
 

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7am Backcountry ;- )
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Discussion Starter · #15 ·
I've got to say running with 28 and the Heckler felt like an even better ride - if thats possible!

Can't believe i've run 35 for so long in the mindset it helped me roll faster LOL

28 front and back now, but I may go a bit lower up front as a test.
 

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There is no magic psi number imo. Its all relative.

The tires itself is a factor due to the knobs and compounds, then consider the rider's weight and bike setup (esp on the suspension)

I get away with 19 psi front and 22 psi rear on big volume tires without the pinch flat headaches. But after I re-setup the suspensions and switch out the rear air to coil, Im now running ~25 to 28 for faster rolling, yet tires still tracks almost just as well if not the same as when running the earlier lower psi.
 
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