I’m enjoying the book Dialed: the secret math of a perfect mountain bike setup and really appreciate the MTB specific and rider-centric approach to bike fitting. I was wondering if you can guide me toward how to accurately measure my RAAD? There’s plenty of info in the book on how it should be set, but I’m not clear on the best way to measure it. Any recommended tool? Protractor devices and angle finders are generally not very long and would likely lack precision if trying to measure from the center point of the bottom bracket.
My RAD is prefect, surprisingly, with a fully stock bike (Large 2021 Epic EVO), so I’m afraid to tinker with the wrong adjustments and just end up messing up my RAD by trying to dial in my RAAD. Any tips on accurate measuring would be greatly appreciated.
Thanks in advance!
Thanks for buying Dialed, and for reaching out.
RAD is Rider Area Distance, the distance from your bottom bracket to your grips. This is the A1 most important aspect of a dynamic MTB fit.
RAAD is Rider Area Angle in Degrees, aka RAD angle. This is the angle of your bike’s RAD relative to level. A higher angle brings your bars closer and higher, which is usually great for technical handling. A lower angle sends your bars farther and lower, which can feel better for seated climbing. XC bikes tend to be about 56 degrees. All-around trail bikes are usually about 58 degrees. But the numbers aren’t super important.
If the frame is the right size for you, and your RAD is perfect, the RAAD will be fine.
I assess RAAD when I’m modeling a bike in the rider/bike calculator at www.llbmtb.com, but these days I never measure it on the bike. It’s really hard to get a good number and, like I said, if RAD is good all is good.
The best way I’ve found to measure RAAD: Take a photo of the bike from a long distance away with a strong zoom. This flattens the perspective, like photos in bike company sites. Once I have that, I measure RAAD in a graphics program.
Once that’s handled, your bike will likely feel great.
I hope this helps!