Bosch Purion - Tire Size Setting - Odometer and speed display when changing tires


New member
Local time
12:47 PM
Mar 7, 2022
My buddy and I both own Trek Powerfly 4s (his is 2021, mine a 2020). Both our bikes run Bosch motors and Purion controllers. In advance of a longish road ride, we each swapped out the stock 2.3" mountain bike tires for Schwalbe road tires. He went for a 60mm tire and I went for a 50mm. The sidewall on his tire is taller than mine, so effectively his wheel diameter is larger than mine. As a result, my bike displays speed and distance covered as approximately 10% greater than his, even though we ride the same actual speed and same distance.

Question, is there a way to adjust the Bosch Purion controller to take into account different tire sizes in calculating speed or distance?

(Apologies if this question has been asked and answered. I searched but could not find it.)
Usually settings give small increments for wheel size, unfortunately they often do not identify exact increments used. If possible, reduce wheel size setting by approx 10%. If settings are not available, or increments not small enough, you could either get an aftermarket speedo or else learn to live with it.
I cannot find access to settings. My Trek bike uses a Bosch Purion system. If anyone knows how to access settings, I would love to hear from you.
Read your manual or call your dealer. You paid extra for this "feature".