i am using a 25mm tubeless tyre. my weigh is around 57kg . currently i set my psi to like 75/80.
on rough tarmac/roads, i can feel the vibration quite bad . so how low should i lower? will 65/70 be good? or shall i lower more?
Thanks
Hereās a good starting point: https://silca.cc/en-au/pages/sppc-form and another: SRAM | AXS
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wow, nice to see you here GPLama, i subscribed to your channel. 
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Just experiment starting from one of the pressure calculators @GPLama has linked to. And donāt be afraid to experiment and try āridiculously lowā pressures. For comparison, I have 28 mm tires, weigh 74ish kg and I ride pressures between 55 and 60 psi. Note that the internal rim width is also a factor (25 mm in my case).
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Just experiment a bit, it depends on the tyres, the rims, riding style, and personal preference. When you go too low, cornering feels weird (unstable), and you might feel sharp bumps (like going up the kerb) too much. The noise from the tyre also changes, and it might feel draggy. When you go too high, riding feels harsh, you feel a lot of vibrations, and on rough surfaces, you feel like you bounce too much and donāt have much ground contact. At least thatās it for me!
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When I was 62kg pre my op and on tubes, Iād pump tyres up to around 85-90psi and leave them a few weeks before topping them up when they began to feel sluggish (or I was looking for an excuse for my lack of performance). Iād find that that happened below 60psi and I never suffered with pinch pātures (some folk can if they go too low). That Silica calculator I think suggests higher, if I have interpreted it correctly but Iād experiment and I suspect youāll be fine.
FWIW, now Iām around 60kg and run tubeless I rarely worry about psi and have found tyres to be be around 40psi before they start feeling sluggish.
Edit I just read what it is suggesting for my gravel bike (35-37psi) yet I am more confident and comfortable at 25psi. So I definitely would recommend experimenting.
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This is basically how Iāve landed at my pressures. For a road bike I might prefer the stable feeling in corners while on a gravel bike I might prioritize the vibration damping in a straight line.
The silca calculator will probably give you a good starting point.
For reference, I used to ride 25c tubed tires at 80+kg around 80psi. Now I run 30c tubeless at 80kg at 59psi. (both road bike)
I second the use of the Silca tyre pressure calculator. Iām running 20-25 psi less than I traditionally would having moved from 23 mm to 25 or 28 mm tyres depending on road surface.
Itās good to experiment a bit but that Silica calculator is close for me. 65 kg, 25mm with butyl tubes and I usually run high 70 psi on the front, low 80 psi on the rear. I used to run much higher (upwards of 100 psi) and got flats way more frequently than I do now.
I think the experimenting point is a lot more important when going tubeless. You have a much wider range of possible pressures than with tubes. Plus you wonāt flat if you get the pressure wrong, so experimenting is less risky.
It also depends on your bike/wheel setup. 80psi on 28mm tires on my Bianchi with CV feels much more subtle and comfortable than my commuter/gravel bike (lower price alu frame) with 50psi on 35mm tires.
And personally I really dislike the feeling of too low pressures while cornering on my road bike.