Question on tubeless tyres and psi

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Luca199
Posts: 60
Joined: Thu Mar 18, 2021 4:43 pm

by Luca199

Hi all,

I have GP 5000 TL 25mm on a set of campagnolo bora ultra wto 45 (with 19mm internal rim width, 26mm external rim width).

I’m currently running the tyres at 80-85 psi on London roads and outside (Surrey, Kent etc). Body weight is 82kg, system weight is roughly 9-10kg with saddle bag and water bottles, so let’s say 92kg overall.

Which pressure would you run these tyres at? Is there a psi difference I should take into account between short ride (up to 100km rides), medium (100-200km) and long distance (200+ Km rides)?

I’m currently enjoying the 80psi mark as they seem much softer and to roll much better, however I wonder whether or not I could go as low as 75psi (or even further?) on 25mm tyres. I wouldn’t want to run into trouble….

What’s your advice/feedback? Also, I’m thinking of changing tyres as my current ones are quite worn out. Worth sticking to gp 5000 TL or should I try the schwalbe pro one TLE latest version (Addix compound) 25mm? I’ve read mixed reviews on the latter, including issues with air leakage and puncture problems…

Any thoughts? Thanks so much!

mikemelbrooks
Posts: 345
Joined: Wed Jun 16, 2010 10:58 pm

by mikemelbrooks

I am much the same weight 76kilos and run my 25mm gp5000s at around 70psi. I forgot to pump them up when I was going out on a group ride and when I got home there was 40psi in them, but I tend to be quite light on equipment.

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DaveS
Posts: 3922
Joined: Fri Mar 24, 2006 1:26 pm
Location: Loveland Colorado

by DaveS

Try the pressure calculator at zipp.com. It suggests 77 front and 82 rear. If your bike has room, I'd try 28mm tires. I only weigh 61Kg and run Michelin power road tubeless with pressure in the sixties. Rides great.

With 28mm, the recommended pressure would drop to 66 and 70.

It also pays to insure that your pressure gauge is accurate. The gauge on my old Silca pump was off by about 8 psi, so I replaced it with a much larger and easier to read 0-100 psi gauge.

tjvirden
Posts: 540
Joined: Sun Nov 22, 2020 9:21 pm

by tjvirden

I've ridden a lot in Greater London + Kent/Surrey in particular. I find there's the full range from occasional perfect surfaces, to truly dreadful. Into Kent and Surrey, you have presumably discovered that there are many short, but fast descents, some of which have very bad surfaces in places. On the dreadful bits I think you'll be pushing your luck at 80 psi.

Personally, at 80Kg all-up, I'd run the 25mm TL (on a 19mm internal) at about 85f/95r, but I think a bigger tire is a better option on these surfaces.
An acquaintance of mine runs the 25mm TL at 65psi on the same roads, but at an all-up weight of about 70Kg.
Last edited by tjvirden on Mon Jun 14, 2021 12:01 am, edited 1 time in total.

MikeD
Posts: 1000
Joined: Thu Dec 11, 2014 9:55 pm

by MikeD

Try the Silca tire pressure calculator.

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Miller
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Joined: Thu Sep 21, 2006 8:54 pm
Location: Reading, UK

by Miller

There's no inner tube to pinch flat. Tubeless is very tolerant of low pressures.

OnTheRivet
Posts: 732
Joined: Sat Jul 24, 2010 9:41 pm

by OnTheRivet

Miller wrote:
Sun Jun 13, 2021 10:35 pm
There's no inner tube to pinch flat. Tubeless is very tolerant of low pressures.
I live in one of the most affluent areas on the planet (recent move) and the roads are attrocious, tubeless is a savior here. Between the glass and potholes I probably would have gotten a dozen flats a year. Last weekend descending a pretty fast downhill road I'd ridden many times before there was a sudden large pothole in the apex, caught me out clanked both rims HARD, easily would have been a double flat with tubes. Stopped, inspected tires and rims, good to go. Friend with me who still runs tubes could not beleive I didn't flat.

Stats
Weigh 63.5kg
Tires 28mm GP5000's at 60psi Rr/58Psi Fr

tjvirden
Posts: 540
Joined: Sun Nov 22, 2020 9:21 pm

by tjvirden

Miller wrote:
Sun Jun 13, 2021 10:35 pm
There's no inner tube to pinch flat. Tubeless is very tolerant of low pressures.
! Oh no, not this again :-)
Tubeless is indeed tolerant of lower pressures.
If you're pottering about, then pinch flats won't even be a thing with tubes and low pressures.
High speed on bad surfaces (hard things, particularly edges) means risk of pinch flats.......even with tubeless tires. Dented and/or cracked rims as well.

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Miller
Posts: 2764
Joined: Thu Sep 21, 2006 8:54 pm
Location: Reading, UK

by Miller

tjvirden wrote:
Mon Jun 14, 2021 12:06 am
Tubeless is indeed tolerant of lower pressures.
If you're pottering about, then pinch flats won't even be a thing with tubes and low pressures.
High speed on bad surfaces (hard things, particularly edges) means risk of pinch flats.......even with tubeless tires. Dented and/or cracked rims as well.
I don't get any of that so it's you, not tubeless. You should stop crashing through potholes.

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hartmannce
Posts: 59
Joined: Mon Sep 14, 2020 5:13 pm

by hartmannce

I run my GP5000TL 25с at ~75psi front and ~80psi back. Previously I rode them on much lower pressures, like 55/60 psi front/back, but started noticing more sidewall wear and scratches. Then, on one sportive, I got a sidewall cut in the rear tire, I believe because of the small pressure (forgot to pump the tires that morning). When I got home checked the pressure in the front tire and had something like 40 psi in it. So it was comfy, but short-lasting😅
So, the trick here is to do some test rides, and to make sure that on flat straight road your tires do not roll on the sidewalls.

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