WHAT IS THE RIGHT SIZE MOUNTAIN BIKE FOR ME? Two bikes identical in every way but size. 

As an engineer and self-proclaimed nerd, I'd have loved for this to be a double-blind study. Where you, the rider, didn't know what size you were riding on any given run (maybe M twice in a row without you knowing it, for example). Without being double-blind, it's *incredible* to me that your DH average was within a second between all four runs, and your jump lines within FIVE HUNDREDTHS! Even your subconscious bias (ex: small *should* feel more playful) wasn't able to change your times. That's statistically just insane to me! At least you know you're a consistent rider!

It's crazy to me that you can feel the difference so much. Thanks for putting this together. You guys are truly making a difference in so many ways...

I'm grateful for all these videos, you guys kept me from buying another bike that was the wrong size. I'm 6'4" and had been riding an XL Trek and something just felt "off" it had been years since I rode a bike and just assumed it was me being rusty. Until I did all the measuring and calculations based on things I had seen in your videos. Now I'm riding a Pivot Firebird 29 in a Large and it feels amazing and its noticeable in my riding and progression how much better this bike is for me.

I'm a total nube in this sport and this channel has taught me so much and answered so many questions I was afraid to ask.

This is the best MTB channel on youtube, hands down.

Alex: Another winner! Thank you! A couple of thoughts from this 74-year old MTB'er in the peanut gallery. Agree that the manufacturer suggested size charts are interesting data points, but not nearly as helpful as getting your butt in the saddle on a bike and actually riding it. With the availability of demo bikes being low right now, being able to do a test like yours or even demo two bikes for comparison is problematic. Hopefully that will change next year. I appreciated your final rating criteria: cornering, jumping, climbing, fun. I'd add descending also; but to me the most important is FUN. FUN for how you ride, where you ride, etc. Pretty subjective; but the "laugh and smile" factor, not speed at my age, is why I ride. Rule #1 = FUN!! Thanks again! :-)

Just a shout out, thank you for these videos. As a newbie over 40 your content is gold. Please keep them coming.

A priceless video for all joy riders. Joy is not just about speed, it's about the whole riding experience. Once again, I salute you sir.

Great way to determine what bike you enjoy more. I like that you were able to ride the bikes back to back and not just one size for a week or two and then switch parts over to the other size. Thank you Alex for the video. 👍

You guys are doing one helluva job on the channel. It could not come at a more "fitting" time for me as I dump and take a loss on a frame that is way too long for me yet I am right in the middle on their size chart. Keep up the good work!

I recently purchased a 29er and requested M size because of the 5'8" height. Accidentally, they gave me 15.5" size which translates to small S. Incidentally, I like the ride better than many bikes before it on the actual size M. Thanks to your vid, it explained a lot that getting smaller frame is ok even if you are a medium size.

Awesome video. next time my mate says I'm sh*t at cornering I've got a new excuse up my sleeve. "well clearly my bike is too big!"

You stole my joy, I was planning on winning the small Rascal. haha. Great content as always. As a 50yo recently returned to MTB, these videos have been great and inspirational. You and Lee keep up the great content.

This is one of the most useful reviews that I've seen. It is nice to see this test and the results as I'm a rider that has to pick between 2 sizes.

Alex, as usual, fantastic video. I love the way you think about things and show the difference. This will be something I explore with my heavyweightsmtb channel. Because size does matter. Keep up the awesome content. Ride on!!

So good!!! It’s like info I’ve wanted to know for years now. Great comparison!! Thank you!

Greatest content ever……that just answers soo many of my questions…. Thx 🙏🏻…. I know that test took a lot of input ….!!!!! Really appreciate wat u do to get this content to us!!!!!! Just brilliant 👊🏻

I have a large 29r and checking my knuckle, I’m RAD+ by 2cm. So I lowered the bars and going to try it. A quick road test gave me the ability to wheels and ride it out some ( I have never done that before lowering my bar stack height. What’s amazing, is that Without even knowing this great info a year ago, I checked my grasp angle and realized I needed swept back bars. That change lined up my grasp angle better and also swept the 780mm wide bars back slightly which gave me relief from numbness and better control. Keep the great content coming brother and thanks

Watching these videos are a great start. But nothing beats the real experience of visiting your local bike shop n try it out yourself. Night and day difference between watching n real experience.

Really loved the filming, the time stops and the ease of explaining you guys do

Just wanted to let you know how great your content is. I finally found a bought a medium Specialized Chisel and much of my decision was due to your videos and tips. Now I’m wanting to get the manual down. I know you stepped back to get centered and work on what matters most- you. You guys are great. Look forward to any activity on your channel.

This has literally been the most helpful video series that I have watched … I’m new to mtb with a bmx background and couldn’t figure out why all of the bikes that were recommended to me at 6ft tall were so long and cumbersome

As a 6'3 dude, I like the skills building different bike sizes can give. My XL Stumpjumper is stable and makes me feel like driving a monster truck, as I can take on anything. And on the flipside my DJ is one size fits all, makes me feel like if Spiderman was on a bike; fast, able, and willing to fly!

for dramatic reasos i would like to say sth like 'i didnt know, that i needed your channel so bad' or sth like this, but i already knew thtat i was pretty much done with most of the other popular youtube mtb channels. but anyways i am super happy to have discovered your channel - I LOVE IT! ^^

This is by far the best bike sizing related video out there! It really is. Simple yet comprehensive and practical! Great job Alex 👏

Would have been cool to make this a double blind randomized trial to minimize bias:) then get feedback knowing what you were riding. Loved this bike test. Rad!!

I learned more about how to pick a size here in this video than watching 15 videos for up to an hour!!! Thanks!!

I love these videos.. Completely changed the way I set up my bike! Not only, but I have realized that I like smaller frames and mullet style geo. Next bike I buy will be a medium.

My gosh this makes me feel better about my size small Revel Rascal (I'm 5 8.5 with long ape index!) What a handy video for me! Thanks!

Love your channel as it has helped me so much! The bike fit videos with Lee have been so helpful. - Jordy

I’m a size down from the manufacture recommendation and your observation about the ability to change lines quick is spot on. I’ve found that bot up and down if a line isn’t working, I can almost pick up the bike and place it on a new line. I always thought this was due to weight of the bike but size makes sense.

thank you for both videos you did. That helped me a lot to choose a proper size for me.

Great video! Your channel helped me to decide what size bike to get earlier this year. I was between and large and medium and opted for the medium.

A very practical and real time approach🤘rock on!

I can so relate to this! I'm mostly between L and XL and I always found the smaller bike to be so much more fun! When asking in forums I'm always getting told "at your size you need to go with XL!", but I don't think anybody ever really compared sizes for him/herself... Joy of bike. Truly my favourite channel at the moment! Keep it up! 🤙🤙

I am 5'10 so right in the middle as well. I started riding in the late 80s and always went with a 16.5 or 17 frame size. I ride super twisty east coast single track and have always felt like the smaller frame size was the best choice for fit under those conditions. I have recently returned to mtb and lucked up on a Jamis hardtail. It is listed as a 15" frame size but feels massive compared to my old Bridgestone MB3. I would not want any bigger. Keep posting! I learn something new every time I watch.

I enjoyed this video. I'm almost 71 yo. I have been riding a medium Giant 29er hard tail for a couple of years. I'm 5'- 9". I love the bike, but recently bought a small Talon 2 hard tail with 27.5" wheels. I haven't been on the trail yet. Planning to go tomorrow. Hoping for that playful ride with more line choices.

To me, the best innovations are simple and often obvious. I expect the big boys of RU-vid, AND perhaps the industry will be playing catch up with you on this one. Kudos and thank you!

Great video! Thanks for doing this test, it was very eye opening! 🤘🏽

Great video. I'm always in-between a med and large, but I buy the medium as I feel more comfortable and at home on them. Looking forward to the give away

Nice video! I'm 5'7 and never tried a small... thanks for this great info!

new subscriber here from philippines awesome what a nice comparison on size got love this content...keep it up...thanks man💪

Great video.. I'm 5'6" and have always road M frames. Purchase a Yeti SB130 LR Medium and didn't like it at all, felt huge and I was just along for the ride. Went to my current bike Revel Rascal in a small and love it..

Great video Alex and was good to hear your comments as you rode if you have the time or interest it would be cool to hear how each would go with a longer and shorter stem (ie. go shorter on the medium and longer on the small). That would potentially give them the same RAD but with different wheelbase length and slightly different rider CoG fore and aft.

Really great video. As I'm watching I am thinking....yeah, he's going with the small. On one of the downhill runs you said the small was so much fun. "The Joy Factor" wins out. (there...coined a new term)

Im 5’7”. I just put money down on a Pivot trail 429. Dealer told me I’m definitely a medium. After doing a lot of research including this video, it seams that I should be on a small

Great vid, as always! Your comments about the DHF and precisely why I opted for the Assegai. I didn't necessarily NEED the grippiest tire in the world, but I don't like the "no mans land" between the center and outer treads that most tires have. At "mid lean" those tires aren't confidence-inspiring. The Assegai bridges that gap nicely and I've been really impressed with it. Consistent grip from center to edge! Personally, I don't really notice it rolling much slower, either. Might be worth considering?

I think you’ve touched on a critical point there about bike reviews. What one rider would call nimble and playful in a given size, a smaller rider on the same size may call it a sled. Lee’s RAD concept makes it easier to choose a size, for me I need to adjust the mindset that now I won’t always buy a L frame, as I’m more suited to medium with modern geo. I like Specialized’s concept of frame sizing: match it to your riding style rather than body dimensions. All very interesting stuff. Another great video!

Your videos on sizing were a real revelation to me. I ride an old school geometry XC rigid rig and I've always sucked at wheelies, manuals, bunnyhops, jumps and basically everything that involves one or two wheels in the air. Even on previous bikes (all kinds of them) these techniques were kind of impossible for me, although I'm 38 years old and I ride since my teenage years. Blue, black trails, XC racing - not the fastest guy out there, but doing fine. Wheelies and manuals - nope, not happening :) And since I'm an addicted follower of Joy of Bike since the beginning I thought "Well, maybe you are riding the wrong size, old man!" I'm 184 cm tall, which means 6.04" (real, lol) which puts me in the L category by all manufacturers' standards and is what I actually ride. So I measured my RAD number by the guidelines in your video with Lee (shoulders out, wrists down, look far ahead etc.) and it came out 88 cm. And guess what? The frame I ride right now is... RAD minus squared (84 cm) :) Which convinced me once again that I should NOT blame the bike for being a disaster at wheelies and manuals and just go on with my lifе, accepting this truth. Keep up the good work, guys. This is one of the best MTB channels out there by a mile. Greetings from Bulgaria :)

Joy Of Bike channel is my mtb physic+formula+logic GURU.hope this channel came grew up every day and hope one day i can be master for all what you guys teach....keep it up guru 💪💪💪💪 by the way im your student from malaysia 🇲🇾🙋🏻‍♂️

Watch all your work,never commented before,you and Lee do such a GREAT JOB,still riding in the mountains at 63,not your average Huckleberry Hound, I've learned from you trmembous amounts of life and bike skills,but I just love the NEWTON- METERS,ISH,,,,USE IT ALL THE TIME,,,,,

At 5’6” and always between a small and medium frame, this is pure gold, thanks!

Legend. I'm on the verge of a S (27.5) canyon stoic size range and the M has the 29s. I've been a complete mess on what one to buy. It was the fun tick for the small frame that's sealed the deal.

I'd like to see a video of you trying these bikes out on some technical climbs to see how that affects your assessment. While I'm all for fun-sizing my bike and do plan to size down from the manufacturer chart on my next ride, most of us need to pedal our bikes on parts of our favorite trails. Flow and fun come easier on the downhill, but we sometimes need more room on the bike to turn the pedals to generate the speed needed to have fun in the rough stuff when gravity isn't pushing us along. It would be interesting to see what sort of compromises are required when you ask more of your trail bike. Maybe you'd land on a small with a longer stem, after going back and forth from the downhill/jump courses to an adventure ride trail.

I love all your sizing videos, I've been saying the same thing for years. Can you do a video on crank lengths, because I got a feeling they are to long as well. great job guys keep it up!!

I love that you ran this comparison. As someone living in an area with as much uphill pedalling as downhill playing (distance, but time??? 4:1!!) I would have loved more commentary and analysis on the pedalling aspects/difference/compromises of small vs medium to help understand this bike sozing conundrum the bike manufactures are trending these days. Thanks for another great video.

Great video guys. At 5'9 I ride a 27.5+ hardtail, and a DJ (my wife sends her love to you Alex, be warned she may to punch you when we meet because of THAT purchase haha) would love some day to have a 29er full suspension. Love the channel brothers...

As a new full suspension rider size was confusing ,at 6’1 also stuck in the middle.watching your sizing videos changed the balance an feel of being center ,thanks for your help.rad saved me from making a x large mistake .

I'm a DHR 2 front and rear kind of guy, but I recently tried the Assegai up front on my full sus. Definitely an Assegai guy now! Corners like no other!

Thanks for the video! I just purchased a new 2021 small Rocky Mountain Altitude A50. The shop guy tried to talk me out of the small 😂. I’m almost 5’8” 168lbs. My bike of 8 years is a Medium 2013 Rocky Mountain Altitude 730, well maintained and upgraded over the years. (RAD adjusted, which made it way more fun) The 2013 medium is the same size as the new small. The shop guy didn’t believe me till I brought my old bike 🚴 in and put it side by side. He was cool, but, was really skeptical of my size choice. (Based on my RAD). I couldn’t be happier! Thanks 🙏🏽 Namastoke

Everyone who rides a bike should be subscribed to this channel right here! Really beneficial information presented with wit and humor in all your vids. Thanks for what you do!!👏🙌

Iam so glad I saw this video. You nailed it with this one. Thank you

Super cool stuff. I'm 6'5" so it's usually XL size and hope it works because the XL is usually too small by the numbers but I get used to whatever I have and have joy because I am riding my bike. If I was a sponsored racer I could get the exact bike for my size but I'm not. I have 1 bike and it has to work for everything I do so, I'm happy with what I have. I got my bike from Fezzari and they did a really good job customizing it to the measurements I sent them. After your R.A.D. video I figured out my R.A.D. and checked what my bike was and it was really close, stock from Fezzari.

Great video - I wish I saw this before I bought my Revel Rascal. I'm 6'7" (201cm) and my body rad measurement is 37". I bought an XL Rascal after a very short demo ride. I relied too much on the size charts - they claim an XL will fit riders up to 6'7". This is far from truth. Even with stem and bar adjustments I cannot get the stack/reach measurements where needed.

Great video! This comaprison would have been even more interesting if he rode the other manufacturer recommended size (Large) on top of these 2 to see how the current sizing trend would have held up against the smaller bikes. But hey I quess I can't have it all.

Wow awesome video. I've really enjoyed all the content. Also I thought I recognized the trail - last time I was out there I rented a bike and rode that same trail system. Good fun.

Fascinating… love your work.

I'm at 5'3" and riding M size hardtail bike...Where else I should be riding S size bike. I crash few courses specifically going downhill curve and always thinking maybe it's because I'm a newbie... But this video explains it why... Maneuvering a bigger bike needs a little more technical. On the other hand, it's true tho going uphill and riding on light gravel is really fast and fun. Maybe I need to sell off my M size bike and do a bit saving to get another S size. As of now I just ride what I have... Great Video and explanation...

Really awesome test. I realized after riding M for 7 years that a S is actually what I need to reach that Stoke factor (despite everyone and the bike shop recommended my going for M). Easier to hop, pop and wheelie for me. Most of all more fun! Love your channel and the totally different vibes you bring. Cheers from a 53 year old mountain biking VC ;)!

I too am on the cusp in regards to size. I wish I would have saw this video prior to buying my medium carbon frame. Unfortunately until I find a time machine, I'm stuck with the medium. There is no way my boss (aka wife) would allow me to buy another frame for the foreseeable future. I am now using RAD to make the necessary adjustment to dial in my fit. I thoroughly enjoy your videos. You and Lee compliment each other with your skills and knowledge.

Agree with you on the medium. All the number times show small but your feels said it was the medium that was fastest in many situations. That tells me the medium was the bike with the feels even though the small had the quicker numbers. It would be interesting to know what stems were used and what bars, were they 20, 25, 30mm heights, this will shorten reach on them too. Lee even says the fork travel increase will shorten reach as well but these both seemed to have the same travel. Good work on this video.

Easily one of my top three favorite mtb channels.

No matter what size, as long as you fit your bike to your rad. Its good.!

I honestly didn't know if you guys actually rode trails. I started thinking about it and its the first time I can remember seeing you guys record on a actual trail vs a more park or pump track

I'm 5'11" and ride a large Rascal. It almost feels small to me. Everyone has preferences. Nice bike.

I went for RAD minus on my current steed early in the year. Now I know how much all my previous bikes have been fighting me, cramping my Joy. Thx

This has been extremely helpful to me, especially the reach/RAD data. There is one aspect of bit fit that you have not addressed which is an issue for us taller/longer legged riders (6'3"/36" inseam). By your formula, my max bar width is 838mm, my ideal reach is 47.7 cm. I measured my RAD and it came to approx 82.55cm. What this showed was that despite my height/inseam, the new Trek sizing of recommended XL would never fit me properly in their RAIL eMTB (65 yrs old, need ride duration more than intensity of effort). But the L frame seems to fit these measurements well. However, what is missing is the impact of the seat/pedal distance when adjusted to give the most effective/effecient stroke. A too short distance robs power, increases joint/muscle strain, pain, and the potential for injury. Getting it 'right' makes the ride perfect from leg comfort/stress/pain perspective. The downside is that, for me, this results in a relatively high seat position when the post is full up / adjusted for my fit. This shifts/puts much of my weight constantly on my hands which gets uncomfortable/painful pretty quickly. I've been working through an evolution of 'parts' trying to address this. I just changed out the stock Bontrager stem (70mm) for a PNW Ranger v3 stem with 30m reach and changed out the handlebars from the relatively flat stock to the PNW Ranger bar v3 with 30mm of rise. I haven't had a chance for a test ride yet, but my 'sit' test seems to show that it will make at least some difference. Some guidance/examples on how to approach this type of fit issue would be helpful with some demo of how some of these changes (bar rise/stem length, etc) can effect the weight shift issue.

Thank you for this!!

Great eye-opening video, thanks! You should also try testing a few different stem lengths to see if you can feel a difference.

I agree with the miojox. Great channel.

thank you for your hard work to put out awesome content! btw Yoann Barelli from Gorrila Gravity put out a two sizes of the same bike not too long ago, decent vid but i liked yours better.

Love your vids. Keep them coming.

At 1:25, sick trail,nice riding, great camera work. Wow.

Great work Alex!!

Great video! I pulled the trigger on a medium rsd middlechild and should receive it in the near future. I would probably still have made that decision. I'm 5'9" as well and have gorilla arms too. The adjustable chainstay should help me get rowdy even on the medium. I'd still love to take home your "extra" bike though... FS is not something I've ever tried and it could be a game changer!

Great work and info guys! Thanks for sharing that! What would also be interesting is to set up both bikes to have the same RAD and then test. What do you think? Nama-stoke 🙏🤙 Robert

Yoann Barelli has a pretty cool video about size testing on his bikes. He set up his guerilla gravity size 3 and 4 as identical as possible and then took it to the trails to test out. I love that GG has their sizes in numbers; S/M/L/XL gives folks a lot of bias to start with picking sizes. At 5'11", I'm almost always either solidly in a L per a sizing chart or sometimes borderline M/L (which can be tricky to decipher), but with a lot of today's bikes, I'd be happier on a M for trail riding. FWIW, I'm at 74.5" wingspan, so arms are a little "long". I think it makes sense that long arms works well with a shorter bike, it's just a little counter-intuitive.

I was surprised to see that elapsed time was your primary criterion. I guess I don't understand the obsession that MTBers have with speed. OTOH, I am obsessed with fun. That would have been my primary - and only - criterion. I wish MTB rentals weren't so expensive. If I want to try two sizes of 5 different bikes, it will cost me $1400!

Awesome! This (along with your other RAD fitting vids) just locked in my choice for my next enduro bike. I'm 172cm and am picking a small (436mm reach) over a medium (457mm reach). The manufacturer recommends the medium but the numbers just seem long for my height. All because of the qualitative stuff...I couldn't care less about 1-2 seconds on a lap. Great post here. Thanks.

You set this up well and I enjoyed watching it. Wild to think that such a small change is so tangible. Ever change the stem on the one you kept to see how that compares to a change in frame?

Alex, i've been wondering the same thing about sizing as you have, and i think just as you did, the best thing is to probably ride them back to back. I'm 5'7" and ride a medium Giant Trance 29er, which is on the low end of a medium. I feel really comfortable on the bike, but i've often felt i should have a smaller one. I usually find it pretty difficult to pop the front wheel, whether it's to do wheelies or just to get over an obstacle, and i feel going to a small might fix that. Planning on testing both for my next bike.

Having said it'd be fun to see the channel out on the trail, want to confirm that it is fun. Very. And really nice camera work. One quibble, we are riding right along with you. But the banner (indicating which bike your on) at the top of screen is downtrail right where we are trying to look. Scary! Bob (husband of Amy)

Good stuff! Thank you!!

I think this is a much more balanced approach and viewpoint than your other videos. “The numbers that work for you”. As opposed to the viewpoint that all manufacturers are leading riders astray and sizing is completely incorrect. I hope you enjoy the bike and good luck raising money.

great video. as for tyres; leave those maxxis behind and get you a set of schwalbe nobby nic and since you‘re rather light go for the 2.35 width

What a great video, sizing has always been a bit of black magic to me.

this is unrelated to rig size but I'm curious about steps you take to avoid biker's elbow. I ride daily so the pain never really fully leaves.. it seems to be exacerbated by any movement involving pulling back sharply on the bars (which is pretty much everything! hops, jumps, wheelies, manuals). a video or short with some practical tips on how to prevent or treat this would be huge. anything to keep me outside on two wheels a little longer.. love the channel! you break things down in a way that's so easy to consume and apply. appreciate what you do big time

Wow! Awesome video and discovery.

Just found your channel and went through all the sizing videos. Love the last bike that I bought (admittedly a LONG time ago ~15yrs) was “sized” to me at the shop by asking me “does the top tube dig into your crotch?” if no then go up a size, if yes go down a size. Looking at getting back into it which is where I found the channel; thanks for all the information on the new sizing of bikes. Although surprised there isn’t a video on crank length.

Loved your vid here! Very well said and done 😎