RAD is the new Reach: How to Size Your Mountain Bike

Let's take a look at RAD (Rider Area Distance) and Reach. Should we size up or down on our next mountain bike? I think the best starting point is multiplying your height (cm) by 2.55 to get your reach. For me, 171cm x 2.55 = 436 mm reach. Use the RAD to then further pinpoint your bike's size.

CREDITS....
Pink Bike's Jack Moir clip:

Joy of Bike (where I first heard about RAD):

Pink Bike's Grim Donut (the ultimate bike of the future!):

My setup...
Frame: Orbea Rise (medium)
Suspension: Fox Float DPS Factory (140mm)
Fork: Fox 34 (140mm)
Drivetrain: Shimano XTR
Crank: e*Thirteen Carbon (with red Loctite)
Brakes: Shimano XTR
Bar: Oneup Carbon (760mm)
Grips: Revgrips Pro RG5
Dropper: Fox Transfer Factory (150mm)
Saddle: Selle Italia SLR Boost SuperFlow
Wheelset: Race Face NEXT-SL TLR Carbon 29"
Front tire: Maxxis DHF EXO+ 2.5
Rear tire: Maxxis DHR II EXO+ 2.4
Mudguard: RRP Proguard Bolt On Mini
Pedals: Oneup Aluminum

For the love of mountain biking!

[Hexsense]

On XC bike, I found that slight RAD+ can work well for seated position as well. But it require you to set RAAD really low to get to the RAD number.
Meaning, very low bar. Like, using 0 rise bar and FSA Drop stem or Syntace Flatforce on thin headset cap with no spacer.
If you set up the bike with tall bar and shorten the reach until you get to the RAD. Seated riding position feels way too cramped.
So, instead of shorten reach to reduce RAD, lower stack reduce RAD as well. But it straighten the arm which is more comfortable.
Still, setting up position at RAD makes my saddle slam rearward than I'd like. So, I set up slight RAD+ which allow my saddle to be a bit more center on the rail while seated comfort is still good.

[mossy.trails]

I am in a very similar situation and have almost an identical RAD to you (774mm) but I am just under 5'6" interestingly. I currently ride a small Marin Alpine Trail 7 but it does feel a little small for the bike rad is about 800 or thereabouts so 'technically' big for my RAD. I'm looking at getting an emtb in the summer and can say with certainty that RAD or no RAD...I will not be getting a bike any smaller, I definately feel that for trail speed cornering and front-end stability, i'd rather be a little more stretched out as at the moment I tend to get a bit nosey and forward in corners. Reach on my current bike is 430. I'll be looking for something in the 440-450 range.

[BowzKnows]

I am glad I found your video. I feel like my current daily, a med 21 commencal clash had made me biased to long reach bikes. I am looking at altitude powerplay and my Lbs only has small. I am 170cm and the small range ends at 170 cm so I have been thinking all week if the small is what I want but the reach is 40mm shorter... I'm going to try and see what this math says I need. Great video and explanation thanks!!

[mike_millard]

I am about 5'10" and have a rad of 825mm. My current bike which I am selling as a reach of 480 and a rad of about 845 mm. With the 64.5 ha, a 77° sta. and the long reach the bike excels at going fast in a straight line over rough terrain. The problem I have with it is when it comes to cornering. Before my current bike I had a bike with a 430 reach and a 75° sta, it cornered great but the riding fast through technical terrain was challenging. The new bike I am getting has a reach of 458 and a 76° sta. so I think this will be a great compromise. Also I specifically looked for a bike that did not have too steep of a seat angle, I find 75°-76° is the sweet spot between climbing in and out of the saddle. With my 77° the nose of the saddle hits the back of my legs while climbing sometimes. I hope you are recovering well and riding as soon as spring hits.

[ej_drew]

i think the rad measurement can only go so far bc you can have a long reach and low stack height (and vice versa) and still end up with an uncomfortable bike that can have your weight displaced wrong. however if this is paired with joy of bike's approximate reach calculator (height mm x 2.50) then you might stumble upon some good fitment. i personally use the pythagorean theorem between stack and reach to know if a bike will fit and knowing bar height and stem length can be manipulated i can understand how the bike is going to feel based on the right triangle stack & reach form and what attributes it offers.

[Plasmo]

Great RAD discussion. One thing to add. Wear your MTB shoes when measuring the RAD. I noticed you in low stack thongs, so I recon you missed 10mm of RAD there.

Im 175cm with 870 inseam, so all legs. I bought a used Large Rise (because the online charts said L = 170 - 185). I couldnt get the bike to turn in tight switchbacks and was constantly running wide mid corner, no confidence in the front end grip. My RAD = 810mm. When measured against the Large I was 35-40mm short in the RAD measurement. I then bought a used RISE in Medium as that is 24mm shorter (450mm) in the reach than the large (475mm). My RAD is still on the short side even on the medium. So to fix this I have to get more sweep in the bars. The medium feels like I am better able to push the front into the ground in corners to load up the tyre. I am wondering what a SMALL would be like.

I recon I have been on bikes too big for me for most of my 14yrs on MTBs.

[PsyCrriginal]

Trying to make sense of commenters saying that a 'RAD' bike is too small, and i have a thought. I'm 188cm with longish limbs, reach on my bike is 485mm (almost perfect, 188x2.55), 40mm stem, 800mm bar with more than average sweep. My 'rad' is spot on, so it makes sense that the bike works so well for me, and i LIKE a stable bike. So im figuring all these comments saying a 'RAD' bike is too small or unstable is because of other factors, like chainstay length, suspension setup, saddle position. My stays are 445, seat slammed forward, and my sus is relatively soft/sagged but with high compression.. the bike is super stable and i have plenty of cockpit space.. and i pedal all day on it. Heck maybe ppl are using bars that are'nt wide enough so not getting that space that theyre looking for. In any case, 'RAD' for me is spot on and the bike is great, and ive been ridin for 20+ (aggressive AM Enduro and DH) years if that puts any strength behind what ive written.

[RCKING]

Rad is basically terrible. My last bike was technically bigger then my “ideal” rad and was still tiny. Shorter bikes are great for pump tracks and hopping around but be realistic do you want a “playful” bike when your riding down something out of your comfort zone or do you wanna feel safe and in the bike? Sense moving to my large geometron It’s been nothing but benefits on everything from the skull to boogie nights. A year later of owning it and I’m considering selling it and up sizing to an xl or possibly an xxl. But hey sizing is preference.

[Adventure-MTB]

Hello my RAD is 851mm and my bikes RAD IS 787.5MM smaller CAN be good do you think 63mm short is too much ?

[Cata]

I'm about 170cm, wanted to get the mondraker Raze but it's 450mm in reach for the S size -_-. Can't find a decent bike with a decent reach for my height... 😥

[rolffuchs]

I guess it is about riding preferences. Like me, I prefer more longer rides, I have long legs and a shorter bike feels really uncomfortable for me and with 84 cm inner length and Length of 5.8 it is always difficult with this really short seat posts, because there is not much left and I have to go for a 420mm.

[magnate]

Nice video! Were you running stock stem and handlebar when you measured the RAD? If not, what are you using? I’m trying to figure out what the RAD is of a stock medium Rise.

[ArmaniFlyHigh]

to me a enduro bike should have a good stack hight, reach and most of the endurobike have a 64 HA. My setup. XL framset from Raaw MadonnaV2 and a pike ultimate upgrade whit a 160 debonair Yari spring + C1 and offset 42mm as it stands 170mm and on the back i got the push 116 coil from push industry 205x65....okay, before this setup i had a Kona Process 153 Medium and it was not the right style of bike for me sinds the stack hight was to low and at some parts of the trail when the bike is collapsing, feels more like a Small bike...the more travel the bike has the more in it will collaps. then again...depending on your ride style.

[ottinsv]

My RAD is 810, my bike is 840, it's a medium frame. I have adjusted everything to increase the size [I, m 5’”9), I always feel cramped. I ordered a size large Giant trance 29 3.

[EMTBonsai]

It's all in Lee Mccormacks book Dialed it was him who discovered the RAD his own method that's now getting out to bike shop's for correct sizes and ignore manufacturers size guides

[-NewDay-]

I sized down because the staff guy said I’d be a xs in Liv bikes. He didn’t have me test ride a bike so I hope it fits. It’s being put together at the bike store

[RobertFullStop]

I'm at the very top of size M, but have long wingspan and went for size L on my 460 mm reach 2023 Marley 275, which has a top tube of 629 mm - 620mm being top tube length on a M size Scout, which is what I would get for a 29in aggressive hatdtail. I feel I'd prefer longer reach for enduro and normal reach for trail riding. Considering both bikes have similar top tube lengths, I shouldn't feel too different. Any thoughts?

Great video 👍🏼

[ciervo]

I'm 5'10. 840 mm inseam and 840 mm RAD. Orbea Oiz L frame is just spot on with 446mm reach and around 840 RAD. Feels great!

[darrinkulyk]

Im the same size as you and bought a Med everything is Adjustable 😎

[rmack]

So my rad is 879 my reach with the calculation is 459
The rad using a triangle calculator on a med dread is 774 with 461 reach and large 794 with 484 reach (I do understand that’s without the rest of the cockpit) idk if those other numbers help or hurt because my reach def say medium but my rad says large!? Which number in your eyes is more important? My current bike is a pole Evolink (I do want a bit smaller) with a 480 reach and a rad of 809! I also understand maybe forbiddens might not fit! I have no opportunity to demo