Physics question.

Being a light rider at around 140 pounds I can run pretty low low air pressure and not bottom out much if ever. But I also find that pressures high enough to not bottom might be too low not to have the tire roll. I tried 2.8 on a 30 mm internal rim and found 12 to 15 fine for not bottoming but I was washing out in corners presumably because the tire was too wide for the rim at those pressures. Using my 2.5 pressures solve that but then fat tires become pointless because the size of a contact patch is dependent upon psi and load. 

So I’ve had a few rides now on the Tannus tubeless inserts and last night I slid out on the front a couple times I think because 13 psi is too low. So I’m wondering if even with the insert I need psi closer to what I use non insert? I would have thought being a light rider I would encounter less sideways g forces than a heavier rider? At my weight maybe inserts are kind of pointless? Not particularly happy with inserts at the moment. 

Rode my hardtail today that has Dissectors and no inserts. It seemed to corner just fine. Maybe it’s just my riding capability is not conducive to inserts. Might be some inserts for sale soon.

12-15 PSI?

Posted by: ReductiMat

12-15 PSI?

Yeah.

Sorry, but my mind is blown that 12-15 PSI can handle any weight.  Maybe it's time I come down from 35...

So, I guess the questions are: Why exactly are you messing with fat tires and inserts if you never really had a problem before??

If I could get away WITHOUT using inserts, I definitely would! You are lucky! That said, I'm curious about the Tannus inserts you have. I'm currently running Cush Cores and love them - but the huge weight savings with the Tannus have piqued my interest. I've just heard conflicting reports about how much sidewall support they actually provide. I do find it hard to believe that the Tannus could provide anywhere near the same support as the full blown Cush Core.

P.S.: Nobody is cornering very quickly on 2.8" tires. It's not really what they're for.

I’m not using fat tires anymore. That was a pretty short experiment that lasted a month. I listen to people I trust but none of them are as light as I am. i was encouraged to try fatter tires by bigger guys. I read a lot about people saying inserts are a game changer so I thought I would try them. Used them in 2.5 Assegai EXO. My initial impressions were positive after a wet ride on the inserts. But once things dried out and speeds went up a bit I found them less impressive. My times according to Strava and my own perception was that they weren’t making a difference. There’s some proportionality thing where me on a 2.5 is proportional to 2.8 for my friends who may be somewhat fleshy. By the same token I’m thinking maybe at 140 pounds an insert is at the limits of benefits. I think may at a certain psi it’s too low no matter how light a person is for harder cornering.

I feel that below a certain pressure the side knobs don’t penetrate the ground anymore but rather get pushed inside the deformed tire profile instead BY the ground and therefore don’t grip in corners. 

This is especially true on round tire profiles, or wide tires on not so wide rims.

I don’t feel a huge benefit with inserts in my front tire, but flat without a beefy insert in the rear tire.

I tend to not ride crazy low pressure, but settled around 22f and 26r on 2.5 Maxxis WT EXO or EXO+ 29“ tires at 75kg without clothes.

Yes the only thing pushing knobs into the ground is tire pressure so for a lighter rider going to a really big volume tire can be counter productive. OTOH a lighter rider is getting the same "big volume" tire benefits as a heavier rider with a smaller volume tire. Inserts can help keep a low pressure tire on the rim and give it some structure, but that doesn't change how hard the knobs are able to push against the ground as that's pretty much all tire pressure.

I've been using Pepi's Rokline yellow noodles (100 gm with valve in 29") with narrow light semi knobbies (2.25") on narrow rims (22mm inside) for xc and bikepack racing at 12-15 psi for my 150-155lb (and I don't add more pressure when I add ~20-25lb of bikepack gear).

The Pepi's are round and take up most of the lateral volume inside the tire.  They begin to form to the inside shape of the tire and squish down into the rim channel, which makes them a real bitch to get off, but they have lots of lateral support even at 0psi (repeated rim tape problems until I sanded the rim bed) so they act like a run flat tire system.

When moving faster than 20 kmph on coarse railway ballast or smaller washboard, the tires seem to have very little rolling resistance (almost like smooth hardpack gravel).  I usually finish a ride with what ever bike I'm on by coasting down a short incline and seeing how far I can coast around the perimeter of a gravel playing field and find that I coast further than with 2.35" nobby nics with no liner and wider rim, other peoples 27" wheel bikes, and my road bike with 32mm all road tires.

The narrow semi knobbies with noodles work pretty well down rock slabs (like middle Crippler), wet roots and bermed corners, but not so well on marbley off-camber corners.

Weight per wheel is ~100-150 gm lighter with 2.25 semi knobbies (Ralphs and Rons Snake Skin), noodles and 22mm rims, compared to 2.35 nobby nic snake skin, no inserts and 26mm rims. 

Maybe inserts/noodles will let you use smaller volume tires?

I’m selling the pair for 125. It’s in the Buy and sell under wheel parts.

https://nsmb.com/classifieds/view/509/

Facebook has a whistler bike parts buy and sell group. Things seem to sell quickly on it. I recommend posting there if you can.