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Is this too low PSI?

Old 03-27-23, 10:39 PM
  #1  
Symox
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Is this too low PSI?

I have a Poseidon Redwood (which I ride as a light MTB) with 30mm external/26mm internal tubeless ready 650B rims. With 2.6 tires Im finding with my weight (155lbs) and bike weight (about 30 fully loaded) that 18psi rear and 12psi front gives the most comfort without bottoming out, no burping on turns or getting squirmy on my rides. This is while running the tires tubeless.

I think I have to get to 8psi before rolling resistance is affected and 7 ish psi before handling gets impaired with this setup.

with that in mind and 47psi max for these Panaracer tubeless ready tires, what are your thoughts on 18/12 R/F psi? Is it likely Im in the sweet spot or too far from it?

Im new to tubeless and just want to double check with more experienced riders

ty for your insight
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Old 03-28-23, 05:09 AM
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staehpj1
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The bottom limit is probably when they burp or you get rim strike. That said optimum can be based on different ride criteria. Where I usually ride I can't get anywhere near that low without rim strike even with careful riding. There are lots of roots where I ride and I run a lot of air (30# F, 36# R) to avoid bottoming. I usually let the pressure drop quite a bit before pumping and find that I just adjust by picking my lines more carefully. When I air up I quickly notice that my speed for my morning loop is immediately substantially faster. I don't think it has anything to do with rolling resistance, but I subconsciously take slower lines to avoid bottoming out and having rim strike.

Given that, I can get a slower more comfy ride on softer tires or ride faster and get jolted and rattled and blast over the sharp edged stuff. That may not be the typical choices, but that is what I have found on the trails I ride with the setup I use. Personal preference could make someone choose either.

There are other trails that I sometimes ride that I prefer the lower pressure for and don't think I take a speed hit for the lower pressure. I don't ride there often enough to have real data though.

Bottom line... As long as you aren't getting pinch flats or burps choose a pressure that gives the ride characteristics you like, but lower isn't always better.
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Old 03-28-23, 07:43 AM
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Originally Posted by staehpj1 View Post
The bottom limit is probably when they burp or you get rim strike. That said optimum can be based on different ride criteria. Where I usually ride I can't get anywhere near that low without rim strike even with careful riding. There are lots of roots where I ride and I run a lot of air (30# F, 36# R) to avoid bottoming. I usually let the pressure drop quite a bit before pumping and find that I just adjust by picking my lines more carefully. When I air up I quickly notice that my speed for my morning loop is immediately substantially faster. I don't think it has anything to do with rolling resistance, but I subconsciously take slower lines to avoid bottoming out and having rim strike.

Given that, I can get a slower more comfy ride on softer tires or ride faster and get jolted and rattled and blast over the sharp edged stuff. That may not be the typical choices, but that is what I have found on the trails I ride with the setup I use. Personal preference could make someone choose either.

There are other trails that I sometimes ride that I prefer the lower pressure for and don't think I take a speed hit for the lower pressure. I don't ride there often enough to have real data though.

Bottom line... As long as you aren't getting pinch flats or burps choose a pressure that gives the ride characteristics you like, but lower isn't always better.
excellent reply ty
in reading your post I realize I dont ride very fast through the rough stuff. In fact I ride the brakes lightly the whole way downhill on the rough as it would just be too much for me. Im not trying to win any speed records but just have fun while being safe.
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Old 03-28-23, 11:34 AM
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Duplicate thread

Something you didn't like about the answers when you posted this before? same same
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Old 03-29-23, 01:01 AM
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Originally Posted by shelbyfv View Post
Something you didn't like about the answers when you posted this before? same same
actually yes, people were complaining why a gravel bike had such wide tires so I figured going to a forum where people are more likely to ride wider tires was more appropriate.

if I could go back, I would have only posted the question here

Last edited by Symox; 03-29-23 at 08:18 AM.
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Old 04-07-23, 09:27 PM
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Update

Im finding 14/12 R/F psi to work well on local mountain trails. Silca calculator predicts 13/12.5 for my setup on rough gravel and 18.5/18 for tarmac

i definitely prefer the low psi for trails. Way more comfy and great climbing traction. Im a convert of tubeless for mtb!
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