BIKE FIT: How to Size Your Mountain Bike! 

I think the best starting point is multiplying your height (cm) by 2.55 to get your reach. Then use RAD to further pinpoint your bike's size. For those of you that fall outside of the bell curve when it comes to arm and leg length to body proportions (any Michael Phelps out there?), some of the numbers here might seem a bit off--especially RAD, but bar width and crank length. If you would like to purchase a set of Catalyst pedals (best flats out there in my opinion), consider using this affiliate link. All proceeds I make from this affiliate link will be donated to local trail builders. You can try the pedals, and if you don't love them, you can send them back for a full refund. bit.ly/catalystpedals

Ok. after years of riding and trying to find solutions this video made more sense than anything I've watched before. Been wanting to upgrade my bike for a while but sit on the fence in fear of throwing money at what might work. it's not a cheap hobby. So cheers for the great video

Thank you verry much man! This is the best i'v seen on a bike sizeing so far!

Good stuff, similar stuff on Joy of Bike Channel. I'm glad i stumbled on these videos when I did. I just bought a MTB a few days ago and realized, after watching these that the reach and RAD of my bike was too long. This was confirmed in my riding as I really had a hard time bunny hopping, doing wheelies etc. I could probably have shortened the distance with a new stem and bars but I'd rather have a bike that fits right. Luckily I'm within my 30 days to exchange and will be reducing to a small which fits my reach and RAD measurements.

Brilliant punchy delivery. spot on

This is the info I needed to fit a new Salsa. Thx

Another amazing video. Thanks so much you have given me piece of mind I have chosen the correct size. Buzzing.

This Video is Gold thanks!

Tnx! this is actually great! Just what I needed!

I'm 70 and 5'9" tall. I am more interested in climbing (welcome to the Wasatch range!) have a relatively slow cadence and use a 30t oval ring. I tried a 165 crank and ended up with a little bit of Achilles tendon soreness. For me, my 175's work better. My wife has pretty long legs and for her, 170 (Vs. 175) has eliminated knee pain. I think she could go shorter, but I don't think I'm able to. Also, just to remain outside the bell-shaped curve, I find that having my bars at the grips about 5 cm above my seat reduces stress on my lower back and takes some pressure off my palms. As a data point, I can climb anything on Slick Rock except for one 4 foot section at the top of a particularly heinous climb and there's never a point at which my front end gets too light to steer. So, I think these guidelines are great, but you still have to be willing to deviate from them on a case by case basis. My RAD, reach, stem and bars all fall well inside these parameters, though.

Very good information! Exactly what I needed. Gr from 🇳🇱

with this measurement, it means that the longer hands you have, the lower your RAD is. The smaller your rad is, the smaller the bike. But yet you have a big reach, cause your hands are long. This is error prone.

Best video in the world on bike sizing ever!

I guess we know who will never be a sponsor. Lol. Thx for the great info.

thanks a lot man. this helped a lot

The best! Thanks a lot!

Very interesting. Thanks for a great video explaining proper sizing as everyone is different. I was fitted to an XL when based on height I’d ride a L. Now I feel as if I’m riding a canoe on the trails. Debating on getting a L or keeping the XL and upgrading in a couple years.

I find the measurement between the centre of my seat, to stem, finds the best fit. Reach is good, but when seated 85% of the time, stem length and seat angle has a greater impact on comfort and control.

Interesting breakdown but I think the BB height of a bike factors into the crank length. I like a 170mm but I'd almost have soil strikes with my current bike running those.

I'm 5'9" (5'10" with shoes on) and have an arm span of 6'3" so multiplying my height in CM by 2.55 has never worked for me when it comes to determining ideal reach. By the numbers I should have a reach of 446mm - 454mm, but based on years of experience I prefer a reach range of 460mm - 480mm. Interestingly the RAD figures seem to be much closer to what I prefer. Thanks for the info.

Apparently according to RAD, my bar width Max should be 866mm and my Min is suppose to be 826mm... I'm riding 800s! With shoes I'm 6'2" and my measured RAD is about 34-35ish inches on the bike riding a S4 Stumpy EVO in the slack and low positions with about 25mm of spacers and a 35mm stem and a 170mm Fox 38 giving me about 10mm of additional stack height. Arm measurement from floor to handlebar width was 33-35 at 800mm-860mm width. My arm length is a bit long at 77.5in (6'5") or 196.85cm. And, apparently I should be riding 178mm for my Min crank length with my 35in inseam according to the Enduro calculation of 0.2x889mm (182mm cranks according to the Max calculation). I'm on 5DEV 165s. RAD doesn't seem to work for me. I like a Large bike with a reach of 465-485mm The Stumpy EVO S5 was a bit too long but felt incredibly stable at speed, but hard to keep traction on the front wheel and slower in tight corners. My Stumpy EVO S4 feels good at roughly 470mm and I have more options with increasing stem length. A good balance of stability and nimble. The S4 Enduro with a reach of 480mm feels perfect and still has a wheelbase that doesn't feel long in corners. I believe in RAD and it works but in the end it's more feel with my obnoxious body type.

Best informative video I've seen, and a previous engineer, I look for tech videos. Well done!

I went n+1 two years ago when purchasing my bike with a reach of 470mm 😮 Im 173cm, and according to the RAD calculation, my bike reach should be ~440mm. Now Im wondering why I have hard time cornering apex! 😮 Thanks for the info… never had a bikeshop being able to explain that to me with a proper method using math. Thanks! 👍🏻👍🏻

this definitely has its limits, at least past the RAD part. I'm 6'6 with a 6'10 wingspan and 38in inseam, this would put me on 850-900mm wide bars and 185-190mm long cranks. I do agree with the reach and stack numbers tho, I prefer a 50mm riser on a single size down from what the manufacturer recommends which lines up perfectly with the RAD numbers. Probably a great bar/crank sizing video for "normal" sized people, definitely good for frame size!

Thank you for the detailed information about the bike fit. I'm a XC racer and I didn't found the crank length measurements for the XC format. You mentioned the downhill and enduro/trail formats but not the XC. Currently, I'm riding on 175mm cranks, 36T oval chainring and my height is 167 cm, i don't know what is the perfect lenght of the cranks. Moreover, I don't want my power transfer in pedal strokes to be affected.

Amazing discourse

Seems like I am pretty bang on

very comprehensive video

I didn’t liked to go biggest dropper, because the seat is below my knees while pedals level. Didn’t like that feeling and went back to old dropper

I'm thinking that RAD should be measured from BB to middle of handlebar grip since you are standing with your arms handlebar width apart

great vid bro. i keep telling people that their bikes are too big!! and cranks, omg.. "so we will put 170mm cranks on both the Medium, and the X-small.. what could go wrong?" - almost every big component maker out there.. me being right in the middle of most bike rec's @ 66" tall, i prefer to size down. my ideal reach is around 425mm and this isnt a rule always, as one bike is 420 and feels great while another is 453 and feels almost identical. STACK and stem and STA all play a role. and fwiw, most industry sizing standards are useless. i have an enduro rig with 155mm cranks and they are the most efficient of my 4 bikes, two others have 160 cranks and i can really feel the difference (30" inseam). *edit: i almost forgot!! if you consider MX and the fact that foot pegs are centered.. using shorter cranks on enduro and DH bikes place your feet closer together towards that center of BB, and it's quite interesting how this plays out. more control. easier whips. more steez. facts!

Hey, just talking to a bike fitter of 40+ years about the RAD measurement and the REACH calculation based on a persons height. He suggested that neck/head length needs to be discounted from the reach equation (height x 2.5) as they are not a factor in reach function of the rider. Instead he recommends from the sternum to the floor is the better, more accurate, measurement points. How does that sound? Sternum to floor X xx.x. Not sure what the xx.x number will be but see below for my thoughts. My height is also 175cm so using your calc height x 2.5 (175 x 2.5=437). My RAD = 820mm My Orbea RISE Medium Reach = 450mm so the bike is a bit long for me, but workable with swept bars etc. The RAD measurement confirms this on my bike as its about 20mm short of the string across the bars. My floor to Sternum = 143.5cm, so to get to 437mm (from the height x 2.5) then Sternum Val X 3 = 437. So does this number work better? I ask as the bike fitter said that those with long or short necks and funky shaped heads will introduce an amount of error into the calculation that can be removed by measuring the parts in the reach function only. Your thoughts?

What do you think is the better adjustment: Spacer height Stem Length Bar geometry When trying to fine tune R.A.D.

Crank length may depend more on foot size than on inseam; I personally know guy taller than me (180cm+) with super small feminine- looking foot (maybe US size 10 or less).

Hello and thanks for this interesting video, where does your formula come from ? The reach recommendation especially (height x 2,55) Thanks !

I love the pencil method. Very clever and appropriate. I just wonder why your not supposed to lift your heels to at least some extend when doing this. Cause this is what you do during lift of at the moment of full body extension. My RAD takes this into consideration.

Just discovered this video. I had question. Do you calculate your height with your riding shoes on?

Great tutorial! Out of interest, what size is your Orbea Rise? I'm 1.7m, similar to your height. If I look at Orbea's sizing chart, based on a personal reach of 434mm, I could fit on a small (425mm) or medium (450mm)? I currently ride a Scott Spark small which has a reach of 403mm with a slightly longer riser stem than stock, and without finding it cramped. The Spark does have a slacker seat angle than the Rise. Spark RAD is 82cm. My personal RAD is 78cm.

Hi there, I am new to riding. I received a mountain bike as a gift from a dear friend, (Giant Revel Aluxx 6000 / Diamond frame L, 29) and I will use it mainly, almost exclusively for urban riding. I am also 5'7'', and even though the frame is an L, I am trying to adjust it to my size. Do the methods described in this video apply for this use as well? Many thanks for your video and any advice would be most welcome. Cheers from The Dominican Republic :)

Can the measurement method from this video also be used for an XC bike?

I have reach of my height times 2.6 instead of 2.55. 470 instead of 460. i do feel the bike a bit long for me, and sometime my left hand go numb on long flat sections. I shorten the stem, rotate a little bit the handelbar. any other suggestions avoiding the numbness ?

Thanks for the video. By the way I make my coffee don't need Starbucks or wars

According to all these things I should be looking for a bike with a reach of approx 420 but because I have long arms my rad is only 720mm. If I used the RAD measurement I think I'd be on a kid's bike.

My rad matches my bike's rad and it fits like a glove. But it's got short chainstays and less travel than I want. So, I'm in the market for a new one with more travel but with so much of the selection online and not much available for testing, I'm wondering if anyone knows a formula to figure out a bike's rad based on its other numbers (geometry).

Makes you wonder why they put 170mm cranks on everything, even XS and S bikes often times.

Does frame reach formula only work for mtb? I tried it for my road bike and it's value exceeds the reach specs for all sizes... Reach on the xl frame is 50mm too short.

The top tube distance is irrelevant for descending? I'm buying a core 2 capra with a smmaler reach of 427 compared to my bike 430 my rad is good at 425 but the top tube will go from 610 to 563. So the bike is getting longer and bigger but the top tube is getting a lot shorter. is that a problem? important? I want to jump and ride DH

Is the idea and measurement for RAD for the casual rider or can it apply for a racing bike?

So i bought correct bike size S, M, L vs my height from Giant chart for 3K$, but all my dimensions are off? lol what to do now

Im 5'4" and i wonder if i can get a small 29 wheel MTB

Does the RAD calculation apply to eMTB? I’m 5’9” and according to Specialized I should ride a S3 but according to the RAD… the S3 is too big…?

Im 5'5 im used 27.5 medium frame with 460mm reach

What if I have short legs? should I get just the biggest bike I can safely use?

No issues with assembly for me ru-vid.comUgkxHL1v1R3NE5x4KiYfyt8dnQmyNYz7qi5L but I could see where some might benefit from using an experienced bike assembler/mechanic. I'm an older rider starting back after a 10 year break. This bike exceeds my capabilities and has been easy to get comfortable riding. I'm mostly on easy trails with almost no street riding and have not been disappointed with the performance of the bike. My fitness level is far below what I previously rode with and because of that the mileage is going on the bike slowly. While I'm losing weight slowly, the bike seems to tolerate my 220 pounds just fine. The bike has been used by several family members ranging from 5'5" - 5'9".

But I've seen plenty of very good or experienced riders who say they don't subscribe to the Lee McCormack theory of bike fit.

I just bought a new bike and I hate it. The store never fit me properly and now I can't return it.

determining the correct reach by multiplying your height in cm by 2.55 is very good way to buy a bike that is too short for you. Trust me, I have did that and it was a very costly mistake.

A ton to digest if you’re not an engineer.

another movie that caused problems for stores. Did you know that crank length do not depends only on standover? This movie causes more problems than good

What's this "bell curve" people are talking about? 🤔

According to suggested way to measure your “rad”, people of the same height but with longer arms should buy smaller size bike? It sounds illogical.

6 foot 175 mm over 6 foot 4 180s when you hit 50 years old go back to “little guy’s cranks “ 170mm the same as a 12 year old bmx champ. this narrator says “if i was 6 foot “ lol . Little guys go to great lengths to discourage 177mm cranks.

The RAD number is total BS. You can literally swap the REACH and STACK values of the bike and get the same RAD number.

My RAD is like 110mm short of the RAD on my bike but my bike fits me just fine wtf lol?