Tyre Pressure Conundrum

[Zimmerframe]

Hopefully someone can explain this to me ..

On my previous hardtail with crap front suspension ... I was running an average of 1.2 (18psi) front and 1.4 (20psi) rear with DHF/DHRII and it felt right. If you hit a rock wrong, it would rim, but it generally good in all conditions. Any higher and it started feeling like you were riding a bowling ball - it just felt too hard. Lower and it felt squirmy.

On the Kenevo, with springy things at both ends .. With the Butchers, they felt generally good at various pressures, though if anything, better at higher pressures like 24/26 psi.

Now I'm on the E-wilds with a 2.6 front and a 2.8 rear. I made the switch as the Butchers felt severely lacking in any grip at all on anything which was hard and wet - they were fine in mud though.

In theory, I should be running lower pressures for more grip, but what I'm finding is that I feel like I have more grip running 25/27psi than 18/20 psi.

Is this just a psychological thing ?? or does the higher pressure help the tyre to actually bite in better and when it does slip, it maybe slides more predictably than when it's a lower pressure ???

 

[MitchF]

Snap mate, running E-Wild 2.6 on rear.
Doesn’t appear to be at its best below 20.
Settle at 22/24
Breaks traction briefly then grips , never actually gets out of control ?

 

[steve_sordy]

The stiffness of the tyre carcass has something to do with it. Less stiff needs more psi to get the same feel. Also the tread needs to be pressed into the trail at the correct orientation for best effect. Ever lower pressure does not automatically give ever better grip!
The tyre itself is part of the suspension and it has its own spring rate and damping characteristics, both of which will be affected by the tyre pressure. Add in the flex in the wheels, the frame, and your suspension of course, and you get a complex mechanism that is multiply damped and sprung. These all react with each other in ways that 45 years ago I would have been able to work out, but not now! What I know is that if you change one thing, you won't necessarily get what you think you will. Best go for a ride and have a good fettle!

 

[Zimmerframe]

These all react with each other in ways that 45 years ago I would have been able to work out, but not now!

Thanks Handsome Prince, it still amazes me that when you were 80 you could still calculate all these things.

It always amazes me with Mountain bikes how much more complicated everything is than you can ever possibly imagine !!

When's the next Tassel Tour ? Do you have a big one lined up for Xmas ?? I'm sure you'd be in the papers if you all dressed as Santa ! Assuming you didn't get arrested for being a mob of bulk discount highly mobile stripper Santas.

 

[CjP]

I found with the butchers 24 to 28 psi was my range that worked best.
Then I went to Maxxis dhr/assagai with cushcores and found 20 to 24 worked best.
Now I’m on black diamond eliminators with cushcores and 14 to 20 works best.

It’s crazy how much psi can change from tire to tire but as Steve said above, it really is like playing with different shock/suspension settings.

 

[YrianX]

Yeah, tire construction and thread counts for a lot. I would not say it's anything un normal the experience you are describing Zim.
And if you are lucky enough to like'em best at as hiogh as 27ish psi the better in terms of protection of rim dings etc

Ride what feels best for you mate, as always

 

[Pdoz]

In theory, I should be running lower pressures for more grip, but what I'm finding is that I feel like I have more grip running 25/27psi than 18/20 psi.

Is this just a psychological thing ?? or does the higher pressure help the tyre to actually bite in better and when it does slip, it maybe slides more predictably than when it's a lower pressure ???

disclaimer, this is coming from someone who measures tyre pressure with the mk 1 " itsaboutright" thumb ....

But if you're noticing more grip at higher tyre pressures doesn't that mean your suspension has too much rebound dampening?

 

[Zimmerframe]

disclaimer, this is coming from someone who measures tyre pressure with the mk 1 " itsaboutright" thumb ....

But if you're noticing more grip at higher tyre pressures doesn't that mean your suspension has too much rebound dampening?

Your guess is as good as mine.. or rather your guess would sound more knowledgeable than mine ? I guess with my limited experience that could make sense....

 

[outerlimits]

I found with the butchers 24 to 28 psi was my range that worked best.
Then I went to Maxxis dhr/assagai with cushcores and found 20 to 24 worked best.
Now I’m on black diamond eliminators with cushcores and 14 to 20 works best.

It’s crazy how much psi can change from tire to tire but as Steve said above, it really is like playing with different shock/suspension settings.

How do you rate the Eliminators over your old DHF Ass rear ?
I have been running the Eliminators for a while now and they are awesome on loose over hard, but a bit loose when in deep sand and loose gravel. Thinking of going chunkier on the front.

 

[Pdoz]

Your guess is as good as mine.. or rather your guess would sound more knowledgeable than mine ? I guess with my limited experience that could make sense....

easy way to find out - AFTER buying the new armour, back off the rebound dampening a few clicks and let us know. Better yet, have a mate do the adjusting randomly

 

[Zimmerframe]

Ass rear

Wrong forum again ...

 

[Zimmerframe]

easy way to find out - AFTER buying the new armour, back off the rebound dampening a few clicks and let us know. Better yet, have a mate do the adjusting randomly

Not even ordered the new armour yet Will give it a go tomorrow .. Looks like it's heavy rain all day .. Uhm ... do I lower the tyre pressure AND drop the rebound a few clicks to see if it's neutral .. This is why everyone should have an @Christian on hand to do their crash test dummy testing ....

 

[B1rdie]

I would say it depends on design. The size and space of the knobs. I had tyres that did the same and my bet is that the knobs recess into the soft carcass rather than into the soil.

 

[outerlimits]

I would say it depends on design. The size and space of the knobs. I had tyres that did the same and my bet is that the knobs recess into the soft carcass rather than into the soil.

So what you are saying is the harder they are the deeper the penetration of the knob. Iff too soft then it’s like a turtle poking its head back into its shell
Interesting ?
I think you have solved this knobbly question. ?

 

[CjP]

How do you rate the Eliminators over your old DHF Ass rear ?
I have been running the Eliminators for a while now and they are awesome on loose over hard, but a bit loose when in deep sand and loose gravel. Thinking of going chunkier on the front.

Ok so keep in mind I’m running Cush cores with the black diamonds. Also I ran one combination in wet weather as opposed to sunny dry weather so it’s not the best comparison but I have found the Eliminators to be a little skittish on the sand/gravel. Everywhere else they’re awesome. I did drop the pressure down to 15psi which made it pretty good but that particular place I ride is always slippery regardless of tire. Also I am getting quicker on said trails so it’s hard to tell if it’s the tire, the weather or just me pushing it more.
I’m gonna stick with them this summer and see how they handle the alpine parks.
The assagai front and dhf rear were a killer combo for the winter though. My only gripe is the ugly yellow writing. I know it’s cosmetic but I hate writing/stickers and yellow.

 

[CjP]

Not even ordered the new armour yet This is why everyone should have an @Christian on hand to do their crash test dummy testing ....

We’re all here to help each other out, I’m glad to provide such service.

Your more the crash test dummy though, I’m more the waste money trying to improve things that weren’t designed perfect from the start kinda guy.

 

[The Flying Dutchman]

Another option is to try a softer rubber compound like Maxxis' Maxxgripp but at higher pressures. I'm running an Assegai with DH casing in the rear at about 35psi which sounds like a lot but is surprisingly grippy and rarely breaks traction.

 

[outerlimits]

Another option is to try a softer rubber compound like Maxxis' Maxxgripp but at higher pressures. I'm running an Assegai with DH casing in the rear at about 35psi which sounds like a lot but is surprisingly grippy and rarely breaks traction.

I went away from the DHF because of a bit of lack of grip on loose over hard. That however was their Max terra compound. If I am going to change back to DHF I’ll try the softer max grip. Don’t care about increased wear on the front as my Eliminator has done 3500km now and still like new.

 

[55plusmxinsanity]

I, too, found the Butchers best at higher psi, 26-30. I now use Assegai’s on both my Levo and Stumpjumper and found that I prefer a stiffer sidewall feel and run them near 40psi and still get great grip and good roll on the mix of dry hardpack and deep sand that I ride.

 

[Rusty]

Tires are designed to run within a certain pressure range. For the e-wild it is 21.75/58psi.
Now, for the life of me I can't see why anyone would run anything other than street slicks at higher than 40psi. The Magic Mary is 17-38psi which I consider to be a more realistic pressure range. Maxxis Aggressor just has 60psi max, which I find very interesting.

As explained to me by a Dunlop engineer many .... many years ago was that tires are constructed to run within a pressure range for a reason.
The pressure range for a particular tire should reflect many things such as compound, casing construction, knob size & placement being the most important. With the correct pressure range a tire should allow the best foot-print to provide the best grip for the conditions the tire was designed for. With a softer compound for instance, a short knob, closely spaced or wide knobs will work better at the low end of the advised pressure range, but a long knob, a narrow knob or widely spaced knobs work better at the higher end of the pressure range.

Far too often I have been behind guys running low pressures "because we are running tubeless" and watched them squirm under braking and when pushing through corners. Going up several PSI more often than not actually gave them better grip.

 

[R120]

I run 2.6 E-Wilds front and rear, I am not obsessive about tyre pressures, but rear is circa 22psi with front a tad higher. I have run them sub 20 and they work ok, but I find that a bit more pressure gives them more bite in the corners.

 

[Gary]

FRONT higher???

I'm too strungover to even ask why

 

[Gary]

for the life of me I can't see why anyone would run anything other than street slicks at higher than 40psi.

I run 40+ on the rear if using single ply 26x2.35 Bling blings and exo 27.5x2.3 minion SSs
why? sidewall support and rolling performance
I also like a semislick to glance off rocks n roots n ruts rather than conform around them. exo/single ply isn't really up to that when things get pointy.or square.
I run around 40 with a DHRII too for the same reasons.
I don't want to take the 400g hit per tyre of DD nevermind 600g a piece for full DH casings. e bikes handle horribly with massively heavy tyres and wheels IMO

28-32psi is the sweetspot for front tyres for me (depending on the particular tyre and conditions). I don't ever run bigger than a 2.5 though

 

[Zimmerframe]

FRONT higher???

I'm too strungover to even ask why

Stoppies ...

 

[Gary]

I went away from the DHF because of a bit of lack of grip on loose over hard.

exactly where a DHF shines?
learn to embrace it's drift zone Daniel son

 

[Gary]

Stoppies ...

was finkin Surrey Hills nose bonks

 

[steve_sordy]

.............When's the next Tassel Tour ? Do you have a big one lined up for Xmas ?? I'm sure you'd be in the papers if you all dressed as Santa !............

I thank you for your enthusiastic support, but I do not want to bore people by running these guided rides too frequently. Two per year, in late spring and early Autumn is about right. The last one was by special request from a previous happy customer, and it just grew!

 

[R120]

was finkin Surrey Hills nose bonks

Jibber jabber init

Yes I like to run the back a bit softer, its probably all in my head but I like a loose rear end.

 

[Gary]

You're hurting my brain (moar)
rears break loose earlier (and more predictably) at higher pressures

 

[R120]

And your quite correct, its just how I like it - I find that more pressure on the front gives the side knobs more bite, and a bit less on the back gives more straight line grip.