Hello, I've been struggling for some time with a KTM 150 SX wp ear, trying to use the pressure that the manual says, but I was unsure if it would actually be that value, or if my air pump is measuring it correctly.
The owner's manual asks that we use 120 psi in the suspension, but I'm still worried that this is correct (as the suspension is extremely stiff), so I decided to use another measurement method and ended up checking this:
When calibrating the tires using the wp air pump, there is a variation in the value presented by it and the manual meter
WP PUMP: 15 psi
Manual and Fuel Station Gauge: 20 psi
Manual and Fuel Station Gauge: 15psi
WP PUMP: 9.5psi
The question remains... which one should I trust? Hahahaha
sorry for my English translator
Air pressure of your forks are just a guideline. Adjust pressure until you are 1.5” from bottoming. You will be in the ballpark. As long as you use the same guage it won’t matter.
But how are you checking it? Some air will of course go into the tube of the WP fork pump, to fill that space up before pressure can be measured. If I remember correctly, it is a few psi.
So, I've already tried this process, but to avoid reaching this limit of 1.5 inches, the suspension becomes extra rigid...
Now I don't know if the 120 psi marked by the wp pump is correct or if it measures more...
If you analyze the difference of 26% more...
So, they say it takes 2 psi to fill the space in the pump tube, but the variation I identified with the gas station and manual measurement is 26%
I did the test with the car tire, if you use a wp pump, it shows 26 psi and at the gas station and manual it says 34 psi
The Shop
It looks to have some hours on it, WP pump. Would not be surprised if accuracy drops.
Borrow someone's at the track and fill the fork to 120 with same pump, then attach each pump back and see if there is a difference.
You can have 2-2.5 inch left on any modern fork. Specially WP, they are not setup to bottom out. If you set it to use full stroke or down to 1.5, my experience is that it will ride low in the front.
Start by telling us your weight, riding skill, and conditions.
120 psi is for riders down in the 120-130lb range running a softer shock spring. You are likely too soft and riding too low in the stroke at 120psi. Or else that 26% low reading has you actually running 151psi 😂 which is way too much for you.
I'll try to perform this procedure on 1.5 inches, to see if I can identify the problem.
Weight 176lbs I believe it is intermediate...
120 Psi with the wp pump, the suspension is exactly stiff, it barely drops 10 cm when flexing the front with the brake applied...
Using the calculation with an error of 26%, which would give 94.5 Psi on the wp pump, the suspension is very soft... But the problem is that it is already below the minimum that the manual asks for, which is 101 psi
I sent a video with some flexes of the front suspension with an action brake.
Update: I managed to test another air pump and mine actually has a measurement error
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