Please help me with advice - tyre pressures

[Labrador29]

I own a 2019 Giant Trance e-mtb +1 Pro. Have done approx. 6500 kilometres on it in 21 months.
Front Shock is a Fox 36
Rear Shock Fox Float DPS
Front tyre - Maxxis Minion DHF 27.5 x 2.60. (Tubeless ready)
Rear tyre - Maxxis Rekon Exo 27.5 x 2.60 also tubeless ready.
I think I have my shocks set up correctly for my riding weight ( 95 kg with day pack), but can't seem to get my tyre pressures right.
Mainly ride Grade 2-3 dry hilly single tracks, some tree roots now and again, some loose small rocks, and the tracks do get a bit rough now and again from the heavy use.
Now and again we are riding over riverbeds with little water but plenty of fist sized stones.
To get to our mountain bike park, we are riding around 7 kilometres on a concrete pathway.
I have tried 17-18 psi in the front, with 20- 23 psi in the rear for the past year, but I think the handling should be better. To me it feels too soft and steering not that positive.
This past week it was suggested that I try 25psi Front and 30 psi Rear. Tried it out today over 30 kilometres, and the steering felt lighter and more positive, but the rear felt too hard and 'bouncy'.
Can anyone help an old fella out with some experienced advice please.

 

[aja07]

Try this as a starting point (I found it pretty close to correct)
Schwalbe Pressure Prof

Also if the rear is too bouncy your shocks rebound may be too fast, try slow the rebound down a couple of clicks.

 

[flash]

A 7 psi change in tyre pressure is enormous. Lower/raise one tyre 1-2 psi and go for a ride. Tyre casing also makes a big difference. An EXO casing will squirm around at lower pressures more than a DD casing. Lately I've become a fan of an assegai up front (maxx grip) and an aggressor out back. 18 up front and 23 the the rear. But both in DD casing. I'm about the same weight as you and ride what seems in similar conditions or maybe a bit more rocky and rooty, but usually dry and dusty.

Also if you're riding on concrete to get to the park you might want to carry a small pump and a digital tyre gauge. Pump 'em hard for the "commute" and the set to a lower pressure at the park. Repeat for the way home.

Gordon

 

[steve_sordy]

Fist job is to get a Topeak D2 digital tyre pressure gauge. There us no point in spending time getting the right tyre pressure and not being able to repeat it, +/-1psi can make the difference.

Whatever tyre pressure you start with, if you are not happy, then change it until you are happy. Don't just ride what others tell you. You have gone from what you say feels low at both ends to what you say feels OK on the front but too hard at the back. OK, drop the pressure in the back until you feel happy.

Bear in mind what @aja07 says about the suspension. Tyres are one part of your overall suspension and cannot be ignored.

 

[Mikerb]

you dont say whether you are running tubeless or not. If not, going tubeless would be a good start.
Obviously both terrain and your riding style impact on the optimum tyre pressure to run front and back. As far as terrain is concerned you either set pressures for the primary section of a ride or accept a compromise...or you could change pressures for different sections, but that is a bit OTT in my book!
In term of riding style, if you are mostly out of the saddle in the ready position, that will be different to a ride where you are mostly seated. For the latter , more of you body weight is over the back wheel tyre, for the former your weight is more evenly over the BB and you choose when you weight either the front or back.
As others have said make small changes and use a decent gauge. An extra 2 PSI on a tyre at 20 PSI is a 10% increase!

 

[MinusPrevious]

I run approx 27psi front & rear & call it a day! Works for me on our hard packed So.Cal soil

 

[Rusty]

I would suggest starting around 26psi front & 27psi rear as a starting point. Move up or down in 1 psi increments until you get the feel you want. Usually I find about 2 psi higher in the rear seems to work best but a couple guys I ride with are the same F/R or just 1 psi difference.

As @steve_sordy says, get a decent guage as small increments can make a differnce.

As a matter of interest, we tested 4 different floor pumps recently - a Topeak JoeBlow Sport Floor, Giant Control Tower 3 Floor, Bontrager Charger Floor & a branded one. There was 3-4 psi difference between them, which is a lot and to be fair to all - none of them matched the pressure shown on the Blackburn digital pressure guage we used to cross reference. That guage when referenced against several other high end units proved to be pretty accurate.

Also something to remember is that suspension set-up will make a difference too. It is all about getting the balance correct.

 

[steve_sordy]

Ref @Rusty 's post above abut the variability across different pumps. Earlier I recommended the Topeak D2 digital tyre pressure gauge. I am not making any claims about its accuracy, although I have no reason to doubt it, what I would say is that it is repeatable. I carry my D2 in my backpack, so it is always available.