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Discussion Starter · #1 ·
So I'm not new to biking, but after years of wasting money on light maintenance I'm trying to understand all this about mountain biking. I've always been a "just give me a bike and I'll ride it" guy.

Anyways I'm obviously not fully understanding PSI. I have converted all my tires for my gravel and mountain bikes to tubeless and love it. But I'm seeing basically 2 types of PSI levels that a re significantly different between what the side of the tire says and what people are saying.

I'm abut 210 lbs year round. On my gravel bike tire walls, PSI says 50-70. Tires are 700c x 38. I'm going on a road ride on a very hot day, pump it up to the 70 (thinking on pavement they will help me roll better) and 30min into my ride my back tire pops, bam like a shotgun. I walk the rest of the way rolling my bike and get home and and notice my front tire is also off the rim. I'm looking online and it says for tires similar to that size your PSI should be about 40 or so, 35 - 45 range.

Obviously I overinflated my tires. I'm also seeing on the mountain bike forums people running the PSI considerably lower than what the side of the tire says. So I guess I'm hoping someone can make me understand this and that the "recommended" PSI on the side of the tire is complete BS.
 

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Discussion Starter · #2 ·
Dam really sorry guys if an admin can move this to the wheels and tires section I would be much appreciated

EDIT: I got my answer on another post. We can delete of lock this thread to rid it
 

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I weigh 180 and run my 38c gravel bike tires at 45-50 psi (with tubes). Scaling up a bit for your weight, 55-60 psi doesn't sound too unreasonable - assuming it's within the inflation range set by your manufacturer. That said, the way to set pressure is more by feel: If the tires are rock hard and you feel every seam in the road then your pressure is too high. If the tires squirm and try to tuck under in corners then you're too low. When trying a new wheel/tire size some experimentation is usually required to find the right pressure for you.

Edit: These numbers can change quite a bit if you run tubeless or go with a wider rim width. My 45-50 psi number above is with inner tubes and and old style 19mm inner rim width
 

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So I'm not new to biking, but after years of wasting money on light maintenance I'm trying to understand all this about mountain biking. I've always been a "just give me a bike and I'll ride it" guy.

Anyways I'm obviously not fully understanding PSI. I have converted all my tires for my gravel and mountain bikes to tubeless and love it. But I'm seeing basically 2 types of PSI levels that a re significantly different between what the side of the tire says and what people are saying.

I'm abut 210 lbs year round. On my gravel bike tire walls, PSI says 50-70. Tires are 700c x 38. I'm going on a road ride on a very hot day, pump it up to the 70 (thinking on pavement they will help me roll better) and 30min into my ride my back tire pops, bam like a shotgun. I walk the rest of the way rolling my bike and get home and and notice my front tire is also off the rim. I'm looking online and it says for tires similar to that size your PSI should be about 40 or so, 35 - 45 range.

Obviously I overinflated my tires. I'm also seeing on the mountain bike forums people running the PSI considerably lower than what the side of the tire says. So I guess I'm hoping someone can make me understand this and that the "recommended" PSI on the side of the tire is complete BS.
Somethings are not quite clear.

Does the gravel bike have tubeless? Also what rims and tires?
 

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I also have four gauges, two hand held, one on a Silca pump, and one on a compressor… they all read wildly differnt…as in nearly a 2x difference between the lowest and highest. Hard to say which is most accurate, so perhaps your gauge was not reading accurately.
 

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hmm

On my road bike I would run them at 110 to 120. You exploding tire was likely a puncture unrelated to the PSI.

On my 29er I run 35PSI.
What width tire you running? My days of >100psi are long gone. 28c tires @ 70psi max all day long. I wouldn't run more than 80 even with 26c but I am kind of a lightweight these days.

38c tire I'd probably run more like 35 or maybe 40psi but if I were #210 I might go up to 50 or so? Just a guess. 70 is too high for sure but the OP's tire didn't blow because of that. Must have been bad tires, flawed installation, crappy rims or something else not pressure related.
 

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I'm only very slightly lighter, fully clothed and with bike tools, etc, could easily exceed 210. With my Rene Herse tires, on road, I use 55 psi rear, 45 psi front. On gravel or rough roads, I go significantly lower with both. This is with tubes. Tubeless allows one to go even lower. If you have supple tires, you don't need to pump to the max to have low rolling resistance.

As others suggest, you might have simply over-inflated them due to a faulty pressure gauge. With those sized tires, they should feel slightly squishy when fully inflated, not hard as a rock. That's the whole point of running wide tires on road.

I would never try to pump these up over 60psi. I could see them blowing off the rims at 70PSI, especially if they are hookless rims. If your gauge is misunderestimating, you are even more likely to have this happen. If you have carbon rims, check for damage.
 

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Magically Delicious
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Tubeless and they teravail cannonball 700c x 38 mm (durable)
I can find nothing on the OEM Teravail Canonball website that mentions these are tubeless or tubeless ready. Perhaps I missed it.
OP didn't state anything about the rims or who makes them.
However the specifications appear to offer a 40-70 PSI range.

 

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Discussion Starter · #14 ·
I can find nothing on the OEM Teravail Canonball website that mentions these are tubeless or tubeless ready. Perhaps I missed it.
OP didn't state anything about the rims or who makes them.
However the specifications appear to offer a 40-70 PSI range.

Yea if you click on the rim compatibility tech page at the bottom of the specs paragraph it talks about the tubeless system.
 

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This is actually a really good PSI question, because the answer is so confusingly complex.

The PSI on the side of the tire is based upon a decades old government required safety test that is still required today. It starts with mounting the tire WITH a tube onto standardized width rims that are narrower than modern rims. And then they do this:

"After inflation to 110 percent of the recommended inflation pressure, the tire shall remain intact on the rim, including while being tested under a load of 2,000 N (450 lbf) in accordance with the rim test, §1512.18(j). "

"The bicycle shall be ridden at least 4 miles with the tires inflated to maximum recommended pressure. Travel shall include riding the bicycle five times over a 100 foot course of wooden cleats 1 inch high by 2 inch wide spaced every 6 feet. The bicycle shall be ridden over the cleated course at a speed of at least 15 mph with the rider firmly seated."

What does that mean for PSI on a modern width rim, running tubeless, with a liquid sealant working it's way into the bead surface as it tries to seal leaks? Nobody really knows. And tire companies can't put anything but the standardized test results on their tires even if they knew the answer. So the only answer is to ask other folks on the internet what worked for them, and then experiment and see what works for you.
 
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