Measuring RAAD on a bike
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.
Focus on 1) buying the correct frame size and 2) making a perfect RAD. Lots more details in Dialed and on the www.llbmtb.com site, as well as ridelogic.bike.
Once that’s handled, your bike will likely feel great.
I hope this helps!
I don’t see the pictures
Hi, that is strange. They are definitely here. Try re-loading the page.
Looking at the comments and pictures in Dialed that I have just purchased I can’t determine if the RAAD angle is the line angle from the centre of the crank is measured to the centre of the head stem cap or to the centre of the handlebars or centre grips? Advise please.
The RAD line goes from the center of the bottom bracket, along the frame, to the intersection of the grips. To see how I measure it on a bike, see this video:
RAAD is the angle of that line relative to level.
Does this help?
Thanks Lee, very much appreciated. To make it absolutely clear for myself, I assume you can use the same string line angle you use to measure ‘RAD’ distance, i.e. bottom bracket centre to 1 cm below the string line.
PS: I have also bought your book Mastering Mountain Bike Skills – love your work.
Yes. Or use a yardstick, which will be easier to lay a phone along.
Thank you for the kind words!
Watched the latest video on measuring RAD – very cool! I measured at 36” (on the money). I measured my HT and FS bikes and amazingly enough they both came out at 34”. You mentioned short is ok… my question is how short is too short? 2 inches seems like a lot. However, at 6’3” I’m riding XL’s so not a lot more I can do other than play with bars, stems and spacers to extend RAD. Thanks Lee!