You quoted me, wrote so much but you didn't relate to what you quoted from me.DRMousseau wrote:Actually, the preconceived notion is that of two balloons being pressed on sharp objects,.... one being grossly underinflated, the other being inflated to max capacity. The underinflated one will likely survive much better IF, it can stretch and shape about the object without damage. And the same is true of bicycle tubes,... which is why these tubes are in protective tires!thunderstorm80 wrote: Wait... So according to the stick-to-the-max-pressure approach, I understand that having a fat-Ebike with Surly blackfloyd's (2 6 x 3 . 8 ) so I can run them at 15PSI or lower is a very, very bad idea on roads?
I have built that E-bike so I can carry luggage around town and when going long distances like traveling - The super wide tires are cushioning your entire bike mass including the panniers - something which cannot be achieved with a regular bike. (Full suspension bikes can only have seat-post rack as it's their only sprung-weight storage space)
Their absolute max pressure is 30PSI but I plan to use them at 15PSI on good roads, and 8-9PSI on roads which are badly maintained.
So I understand that with that huge contact area, especially at the lower pressures, I should carry lots of spare tubes, hole-plugs (worms), seal-in-a-can, etc?
I thought before starting this thread that the super low pressure on the fat-tire will make glass and other sharp objects less prone to interfering with the tire - just like if you roll a beach ball on shred-glass vs sitting on the ball (increased pressure) while doing so.
THE PRIMARY PURPOSE of tires, is to provide an easily and economically repairable or replaceable bearing surface that is subject to wear and tear, while providing "shock" absorbing protection to the supporting wheel assembly and axle. Jus last night, I luckily repaired a damaged rim for the grandson's BMX,... the result of an underinflated tire that failed to fully resist the "shock" at a point of impact, that crushed the tire and tube, transferring the remaining energy into a point on the rim edge, and folding it over a bit. We were both surprised that it was reasonably repairable with serviceable satisfaction. While tire and tube were replaced, the possible cost of replacement to rim, wheel assembly, and/or the labor of re-lacing and such, instilled a sense of value in my grandson of the importance of proper tire inflation and closer regular inspection!
So is 15PSI or lower is a very, very bad idea on roads? No,.... unless other considerations of expected road surface, hazards, load, etc., suggest otherwise. Surly outright recommends the lowest listed inflation of manufactures suggested pressure range, with max rated pressure only to seat tires to the bead. That lowest keeps within the tire manufactures specs (liability protection),.. the minimum to maintain bead on SPEC RIMS at minimum expected loads, speeds, surfaces, etc., while providing maximum bicycle "product" protection(?) of major components (warranty protection). Will that pressure protect your rim against an unexpected pothole with a heavy load, or your axle and bearings against a high-speed curb smash??? Probably not, and nether will the warranty,... "typical" or "normal" use clause, ya know?! And tires are usually excepted with some exclusions too. But if your "normal", stay within Surly's guidelines, their warranty is protected!!! Now your low-pressured tires will be subject to a lot flexing and wear, internally and externally, and a shorter life,... but well within the tire manufactures warranty as well!!! And THAT'S what's most important to manufactures! But that doesn't protect YOUR investment and costs! And those Blackfloyd's aren't cheap tires!!! Nether are Surly rims!
Max psi of suggest tire pressure ranges is well within the limits of typical rim specs, unless brake surfaces are badly worn. It's also well within the limits of safety for expected maximum bike loads, temperature expectations, and speeds. "Fatter", bigger tires generally need less psi to meet those specs,... smaller, thin, "skinny" tires generally need a higher pressure range to maintain the safety needs expected.
Your choice of bigger "super wide" tires for cargo loads, is more a choice of "weight capacity". Bigger tires are capable of a greater weight load at a given inflation pressure than smaller tires at the same pressure and weight load, providing greater "shock" protection. So what's the lower limit??? eh? Should ya carry all that tube, tire and stuff for flats??? mmmm,.... should ya carry an extra rim or wheel assembly??? eh? I don't,... I jus keep my tires well inflated and stay hopeful, lol. No real problems yet.
My current road build under construction is designed with EXTREMELY heavy rear end load capability (hub motor, battery, adult rider AND adult passenger, plus extras? with mostly rear bias) ,... like max load in the near 400lb range on rear tire alone!!! I have many unique concerns here. No bicycle tire is truly capable of such loads and still provide the safety and protection needed as an e-bike. I also have unique considerations of rim choices, spokes (number, length, AND ga.), axle loads (length and dia), frame and dropouts, and jus SO much more! My choice of "super wide" tire has fallen into a 150/80x16" on a double-walled 20"x100 rim,... outside tire dia., is 26". Max rated pressure is 40psi@900lbs,.... I'll likely run about 20-30psi depending on MY load and what keeps the tire in a full profile for min rolling resistance. The heavy 5/16" tread alone (yup,.. run tubeless) should keep me pretty much "flatless"!!! LOL!!!
Regardless of the recommended pressure, most bicycle tires won't hold up to slashes and cuts very well, although some specialties DO have a special layer within, jus for such expected and often encountered incidents. Designed to limit the spread of cuts and tears and still maintain internal construction integrity.
And them dang "goat-heads", burs, thorns, spines and such,.... a heavy thick tread and tire surface is best! Anything else is jus "hopeful".
So here it is again: I want to know about the relation between the contact patch, the pressure and the width when talking about a Fat-Bike tire.
I assume there are a bit different considerations than regular tires. (Just like most fat-tires are squirming at their standard pressure while standard tires don't)
I want to know if it's more probable to get a flat on the road from a fat-tire (2 6 x 3 . 8inch ) at 10-15PSI, compared with a standard 29x2.1inch tire at 40PSI. (assuming both tires have the same tread pattern, same construction, same puncture resistant features, etc...)