tire pressure for hardpack?

[FishMan473]

Heading into a fat bike race this weekend, and the snow has pretty well melted off. So we're looking at frozen dirt, some pavement, hard crusty snow and ice patches. To make a long story short, I'm looking for suggestions as to what PSI would maximize efficiency on hard surfaces (I weigh 170 lbs). I'm thinking maybe 12-15 psi?

[Schott]

I'd say more like 10-12, but it's always easier to take air out than put it in.

[nvphatty]

I'd say more like 10-12, but it's always easier to take air out than put it in.

12 may prove to be the magic dose.

[ozzybmx]

8-10psi depending on the tyres/rim setup. Theres no point asking really, you need to ride some beforehand and find when you get tyre squirm then you have went too soft so add 1psi and try that. If you pump them up too hard then you are losing the traction that fat wheels on dirt are all about.

Think about it this way, the difference between 8psi and 12psi is a 50% harder tyre, some might even say a 50% reduced footprint and grip.

[Johanneson]

Enough air so that bounce " tire bob" is eliminated.

[GT554]

I agree with Ozzy. What wheel/tires, tubes or tubeless? On my Pugsley I had Marge Lites & on hardpack I ran 8 psi rear & 7.5 psi front. On my Beargrease with tubeless Rolling D's I run 9.5 rear & 8.5 front. Any combo over 10 psi I'd think you would get to much bounce.

[FishMan473]

I'm more worried about low rolling resistance than traction. Of the 70 mile race about 40 are flat rail-to-trail. There will be some challenging climbs on the snow mobile trail, but my experience is that frozen soil is the next best thing to hero dirt.

I found 12psi in the front and 13.5 in the rear last night. Seems to roll pretty fast on the street last night so I'm going to give it a go!

[Brogrease]

Let us know how it went please and good luck!

[nvphatty]

I'm more worried about low rolling resistance than traction. Of the 70 mile race about 40 are flat rail-to-trail. There will be some challenging climbs on the snow mobile trail, but my experience is that frozen soil is the next best thing to hero dirt.

I found 12psi in the front and 13.5 in the rear last night. Seems to roll pretty fast on the street last night so I'm going to give it a go!

exactly, in your case traction and foot print are not the priority but to reduce resistance.

[GT554]

13.5! You're going to be bouncing like a bad check.

[nvphatty]

13.5! You're going to be bouncing like a bad check.

naaaaaaaaaa

[No_Roads]

13.5! You're going to be bouncing like a bad check.

Depends on how much you weigh. At 208 12 psi is pretty good for me for packed dirt. If I weight 165 I think it would be a different story. If it was really bumpy however the tire would be jumping a lot for me.

[FishMan473]

I ended up riding the race at 12 psi front, 13.5 psi rear. This was measured indoors before heading out in the cold, so it probably dropped a few PSI from that. It ended up being an excellent compromise for the race. The first part of it was quite rough, over hard-frozen old-field, corn fields, ATV trails. Then the rails to trails section that I though would be fast was mostly ice! Tires were low enough to provide some cushioning in the extremely bumpy fields, but I did feel a little bobbing in the tires when pounding it on pavement. For whatever reason my beargrease seems to bob a LOT.

In the future for hard surface riding I think I'll start out around 15psi and drop it if I feel like it.

[Sasquatch1413]

I weigh over 300 lbs and like 12 psi rear, 9 psi front for dirt riding. Thats on 27 tpi tires. Anything above that gets bouncy.

[ozzybmx]

I ride on nothing but singletrack and dirt, if my tyre pressures are out by 1psi i can feel it. 9-9.5psi on HuDu/trialtechs and 8psi Bud/ML. If its on the lower side the tyres get squirmy which is ok unless im going hard on fast corners, if its too hard the bike bounces.

[GT554]

For whatever reason my beargrease seems to bob a LOT.

In the future for hard surface riding I think I'll start out around 15psi and drop it if I feel like it.

You're wondering why your BG seems to bob a lot & you're going to run even more PSI You're going the wrong way. Just try 9.5 up front & 10 rear.

[FishMan473]

No, it bobs a lot at low tire pressure. I don't know why you would think a higher tire pressure would give you more pedal bob. I'm taking about pedal-induced bobbing on hard surfaces, such as pavement.

[Johanneson]

FishMan473 No, it bobs a lot at low tire pressure. I don't know why you would think a higher tire pressure would give you more pedal bob. I'm taking about pedal-induced bobbing on hard surfaces, such as pavement.

I'm with you Homey, and have been wondering the last few days if there is something strange and different about fat tires when riding in the Southern Hemisphere, Bermuda Triangle etc...

[alaskairhog]

too many variables so i dont even bother measuring except when i air up in the garage. otherwise it's just by feel. totally depends on trail conditions. i'm 160# and would say the highest i run in winter is 10-12 psi and thats if i am going to ride smooth groomed trails. of course if there is soft conditions then i let air out drastically. i ride 90 percent single track though so i'm probally mostly single digits. i let out enough air so that the bumps arent too harsh and making the tires bounce. the magic spot where you have traction and low resistance. basically my tire pressure is always different.