BIKE FIT: How to Size Your Mountain Bike!

Go by the numbers! Frame, Bars, Stem, Cranks, Dropper, Brakes! Reach & RAD! Fit your mountain bike to your body.

0:00 Intro
0:59 Frame: reach
1:27 Frame: RAD
2:25 Bars: width
3:28 Bars: backsweep
4:21 Bars: rise
4:46 Spacers
5:09 Stem
5:42 Cranks
7:37 Dropper
7:45 Brake Rotors

Music:

#mtb #mountainbike #bikefit
For the love of mountain biking!

[IDoBlues]

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.

[nicolajerbas]

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

[joeshawcroft]

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.

[therealridedmc]

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.

[jp]

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

[lynnbattista]

Best video in the world on bike sizing ever!

[Rawkus]

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.

[bikedude]

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! 👍🏻👍🏻

[kayakutah]

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.

[mircea]

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.

[FoxInAFoz]

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!

[followthegnar]

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.

[bellarogers]

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.

[butchl]

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

[todd]

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

[mikestivers]

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!

[tx_reaper]

What do you think is the better adjustment:

Spacer height
Stem Length
Bar geometry

When trying to fine tune R.A.D.

[MaverickMeho]

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

[BowzKnows]

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

[ZippidyMTB]

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.