What tyre pressure with downhill tyres?

[jxrx]

Title says it all really, I've ditched the Maxxis DHR2 DD rear tyre (well destroyed it on a ride really) and the Assesgai EXO+ Maxxgrip front tyre and instead mounted Continental Kryptotal Downhill Supersoft front and Soft rear tyres, both 2.4" wide. I not particularly fussy with checking my tyre pressures going by feel most often. Now I need to know as it's a new setup. I'm on a Canyon Strive:On with Gen4 CX motor which weighs around 25kg with coil shock and I'm 92-94kg with my riding gear on.

I thought to start at 22psi front and 25psi rear, what do you recommend?

 

[Greg Watts]

Title says it all really, I've ditched the Maxxis DHR2 DD rear tyre (well destroyed it on a ride really) and the Assesgai EXO+ Maxxgrip front tyre and instead mounted Continental Kryptotal Downhill Supersoft front and Soft rear tyres, both 2.4" wide. I not particularly fussy with checking my tyre pr...

That's a sensible starting point, and honestly not far off what the DH-casing reviews out there land on - I'd just nudge the rear up a psi or two given your numbers.

For context: reviewers running the Kryptotal DH casing at much lighter weights (150lbs/~68kg, dry dusty rocky trails not unlike what you'll get on gritstone) settled on 23psi front and 26psi rear on an ebike setup, and found I typically ride 23psi front and 26psi rear and I weigh 150lbs or so, with our trails always trying to find the best balance between traction on dry and dusty conditions but because it's super rocky you need enough pressure to protect against rock hits. Another reviewer at 60kg found weighing just 60 kg in full riding kit, 22 PSI in the rear and 20 PSI in the front was still on the cautious/high side for bike park use.

You're carrying a lot more system weight than either of those - 92-94kg plus a 25kg Strive:ON with the coil shock is a serious amount of static and dynamic load through both wheels, especially the rear with the motor and coil mass sitting low and rearward. DH casings do let you run genuinely low numbers safely (that's the whole point of them - thick, well-supported sidewalls), but at your combined weight I'd start:

• Front: 22-23psi.
• Rear: 26-27psi.

That's basically your plan with the rear bumped a touch, purely because rear-wheel loading under braking and motor torque on an eMTB this heavy punishes an under-pressured rear tyre more than a front one - pinch flats and rim strikes tend to show up rear-first. Given it's dry and dusty at the Peak right now you could dip a psi or two lower than you would in wet/loose conditions for extra grip, but keep half an eye on the rim after a rocky lap or two - if you're seeing dents or the tyre's squirming under hard cornering, add a psi rather than chase grip at the expense of your rim.