Dialing in your bike setup step 1: Make it RAD

 

 

This article is adapted from the book Dialed and ran on Pinkbike. It lays out the most important aspect of mountain bike fit and setup.
I hope you find it helpful!


When it comes to mountain bike setup, the most important measurement is the distance between your bottom bracket and your grips. I call this the Rider Area Distance (RAD).

We want your bike RAD to fit your body’s size and proportions. When your RAD is dialed, two great things happen:

1. You have optimal arm range for bike handling: descending, braking, cornering, pumping, dropping and all the fun stuff, and

2. You can generate maximum torque for power moves: sprinting, steep climbing, pumping, manualing, hopping and wheelie drops.

While RAD seemed like my own brilliant idea, other people have been thinking this way.

bigquotes Q: Shouldn’t we be measuring bikes in a different way? For instance from pedals to grips?

A: That’s how Sam Hill measures his bike, he gets on any bike, no point telling him any numbers, he just gets a tape measure and measures feet to bars, and if it makes sense, then he’s happy, and away he goes. I do think that’s the only true measurement you can work off.

– Ali Beckett, mountain bike designer, in International Mountain Bike Magazine

 

Sam Hill piloting his custom Blueberry 2018 Nukeproof Mega.

In this video post on Pinkbike, the crew at Vorsprung Suspension calls RAD “spread.”

bigquotes “This is what really determines how big your bike feels. How spread out you are between your hands and your feet.”

That’s pretty rad.

What exactly is RAD?

RAD is the hypotenuse of a triangle whose other two sides are the reach and stack of your entire cockpit, from the bottom bracket to your grips.

The components of RAD are:

• Frame reach

• Frame stack

• Height of spacers under your stem

• Tallness of your stem’s steerer clamp

• Handlebar rise

• Handlebar setback. This is probably a new term for you. Setback is the horizontal distance from the stem clamp to the grip. Someday we’ll all know the setbacks of our handlebars.

Finding your ideal bike RAD

Your ideal bike RAD is determined by your body’s size and proportions, as well as your handlebar width, crank length, pedal thickness, shoe thickness, phase of the moon and, by extension, the grunion run.

My book Dialed and site www.llbmtb.com provide several ways to determine your optimal RAD and calculate your ideal bike setup.

Dialed: The secret math of the perfect mountain bike setup.

Here are two more methods:

1. If you love your current bike, measure its RAD. When you shop for a new bike, try to match that number.

2. Use a simple multiplier. The multipliers below assume average proportions, sweet spot handlebar width, height-appropriate crank length, and average pedal and shoe thickness. While these recommendations are not gospel, they are good starting points for most people.

If you’re male, multiply your height in centimeters by 4.47

If you’re female, multiply your height in centimeters by 4.60

At 174 cm tall I get a RAD of 778mm. My bikes are within a few millimeters of this number.

Warning: These multipliers will give you shorter RADs than you typically find on fashionable bikes. Bikes have gotten longer but people haven’t.

Adjusting your RAD

Q: How close to perfect does RAD have to be?

A: The closer the better.

We can of course ride a wide range of bike setups (we’ve been doing it for years). As your bike RAD gets closer to ideal for you, your bike will start to feel better. When you get to the last 10mm, then the last 5mm, then to perfect, something clicks. Your bike just feels right. You climb technical trails easier and shred technical downhills harder.

When bike RAD is too long, you reduce torque and reduce control. I’ve set up about 1,000 riders, and 95% of their bikes had too much RAD. Most riders don’t know any better.

When bike RAD is too short, you reduce torque and increase control (to a point). Some downhill and freestyle riders, who need more range of motion than peak sprint power, have RADs that are “too short.” This is common among tall riders. When it comes to RAD, a bit too short is much better than a bit too long.

You can adjust your bike’s RAD in a few ways:

Reach. Change the stem length or use a handlebar with different setback.

When Specialized sent me a medium 2017 Enduro Öhlins Coil (thank you!), it was 20mm longer than my last medium bike. A SQLab 30X handlebar has extra backsweep and setback, which shortens the cockpit and makes the bike fit perfectly.

Stack. Move spacers above or below your stem. Change to a stem with different rise. Try a handlebar with different rise.

Frame size. This is the last resort. These days, as frame reaches get longer, many riders should consider a smaller size. By the way, it makes sense to measure before you buy.

If your frame is the correct size and your RAD is perfect, your bike will handle great.

That said, you can dial in your bike even more by adjusting the angle of your RAD relative to level. I call this your Rider Area Angle in Degrees (RAAD). We’ll talk about that next time.

I hope this is helpful.

Lee

47 replies
  1. leroy holmes says:

    Hi Lee,

    When measuring RAD from a birds eye perspective i.e. looking down at the bike from directly above is RAD measured from the bottom of the “T” to the top centre of the “T” or is it to the top left or right? (Bottom of the “T” being the bottom bracket. Centre of the “T” being equivalent of where handlebar meets stem.) Does that make sense?

    Reply
  2. codyish says:

    Do you think your simple multipliers apply to XC racing setups as well? I ride a relatively trail-style position and riding style for XC – but then I checked the RAD on my XC bike it wasn’t even close – I’d have to go down a full frame size, and that might not even get there.

    Reply
    • Lee says:

      1) A traditional XC setup is a lot longer than what’s ideal for bike handling.

      2) Many bikes these days are too long for their riders. Too long, again, for ideal handling.

      I’ve worked with XC racers who set their bikes up in the Dialed method, and they are very happy.

      Reply
  3. James Groves says:

    Hi Lee

    This is such great information thank you!

    Your reach calculation of 2.5 x 185cm puts me at a reach of 462.5. My Vitus Mythique L has a reach of 462.37. So went for this based on this. Now the bike is here.

    First time trying to work out what my RAD measurement would be, on the Vitus it comes as 900. My rad using your calculation at 827. Any suggestions on how to loose upwards 6cm off of this?? Time to buy the book me thinks! 🙂

    Reply
    • Lee says:

      Hi!

      Shorten the stem ad lower the bars. And get the Dialed book or join llbmtb.com or check out the bike setup lessons at ridelogic.bike.

      Reply
      • James Groves says:

        Thanks so much Lee! I will have a play and check our your resources.

        Also feedback from the UK, your recent content on JOB is incredible!

        Reply
  4. RC from SC says:

    Amazed! I rode too small of a bike for the last decade. I recently bought a new larger bike without trying it first, and proceeded to change my stack stem and bar based on feel and a lot of deep thought. It feels good to me but I have never been fitted or even advised about optimal fit. Just beginning to read about it now.

    Tonight I find this and I measured myself again and my RAD. Insanely stoked to find my bike RAD is DEAD-ON to this calculation. (Within 2mm as best I can measure)

    I spent months thinking and tinkering to arrive at this fit and here you have it solved already for me. It’s brilliant! I needed this confirmation so much. I’d been contemplating going to a bike shop to check my fit to see if I’m missing any range of motion. Well no need for that now! Super stoked to find this and your courses I can’t wait to buy them!

    Reply
  5. Jeremy says:

    What would be the best way to buy from online retailers…ie: YT, Canyon…etc? The geometry charts are frame size measurements not incorporating stem, spacers, handlebars…et al?

    Thank You

    Reply
    • Lee says:

      Hi Jeremy,

      Here are two cool options:

      1) For q quick estimate, multiply your height in cm by 2.5. That’s your target frame reach in mm. Get as close as you can without going over.

      2) For way more precision, use the rider/bike calculator at http://www.llbmtb.com or ridelogic.bike (Dial in Your Bike – Pro). This thing lets you model all aspects of the frame, stem, bars and spacers. You can make sure the setup is perfect before you spend money.

      Good luck!

      Lee

      Reply
      • Chris says:

        Hi Lee,

        Using your numbers my Rad is 438 this falls almost perfectly between a Large and a Medium frame reach of the bike Im looking at. I have no idea what to do now

        Reply
  6. Joshua Miner says:

    A friend just sent a video where you discuss your RAD concept (we’ve been talking a lot about sizing, since we are both buying new bikes soon). I can’t figure out how it could be possible though… I’m a pretty average medium-sized guy (5’7” without inflation), so using your calculators, I should be on a bike with a reach of around 362 and a RAD of between 644 and 659. I just went and measured my 2 current bikes that I have what I consider to be pretty dialed in after years of riding (mostly gnarly old-school XC stuff — no flow no gravity as much technical uphill climbing as possible). Both bikes have a RAD of 795 on the nose. The 2017 Trek Top Fuel is a M/L with a reach of 443 and head tube angle of 70° and the 2018 fully-rigid Heller Bloodhound (with 27.5×3” wheels) has a reach of 423 and hta of 68.5°.

    I just cannot understand how what I think of as a “perfect” riding position is significantly more than 100mm longer/larger than your suggested RAD. I know you said most XC bikes are set up too long, but this is like a whole other universe! I guess I’d have to find someone’s XC bike with a shorter RAD to try out, since I don’t think there’s anyway I could get mine down to the 650 neighborhood with stem/handlebar adjustments.

    Thoughts?

    Reply
    • Joshua Miner says:

      Oops — math error! My “recommended” reach would be 425 and my RAD would be around 765 — still quite a bit shorter than my “ideal” 795.

      Reply
      • Lee says:

        Joshua,

        A 795mm bike RAD might not be ideal, but it’s what you seem to be used to. Mobility, skills, riding style and bike fit all work together.

        Those videos are super basic and pared down. You can learn all the details — and get access to the sweet rider/bike calculator that lets you run various scenarios with your bike — at my site http://www.llbmtb.com. For a free month use the code JOYOFBIKE.

        Please check out the site (it’s free; why not?). If you still have questions, post them there.

        Lee

        Reply
        • Josh M says:

          I got myself set up yesterday with a height x 4.55 RAD (swapped my 100mm 6° rise stem for a 50mm with no rise) and tried it out. It did feel good in some ways — mostly it allowed me to lower my saddle about a cm, which was nice), but I noticed the steering felt overly responsive while doing technical climbing. Maybe something I could get used to? Maybe I’ll just split the difference and try to get a bit of a best-of-both-worlds experience. Thanks!

          Reply
  7. Arno says:

    I’m 190 cm with 87 cm inseam (tall with short/average legs) and regardless of the brand, I’m always in between sizes. It’s a nightmare for buying a pair of pants, let alone a bike! It’s funny how Canyon’s size calculator puts me on a size L, but when reading the geometry charts I should go for XL. And it’s confirmed when calculating my reach (475). But apparently Canyon is known for advising shorter bikes.

    Reply
  8. Raphael M says:

    Hi Lee,
    First of all, I love you and Alex on Joy of Bike! So much so, in fact, that I bought your “Dialed” book to give me the best understanding of MTBing, especially sizing!! So my dilemma is, with the bike shortage and increased demand on all bikes, I put down a deposit on a Medium 2021 Giant Fathom 29 2 (smallest available size at any LBS in my area), whose reach is 445 mm and RAD is 765 mm. In contrast, a Small Fathom 29 2 has a reach of 426 mm and 753 mm, which is closest to my ideal reach of 420 mm and RAD of 751 mm. My question is: should I settle for the Medium or hold out for a Small, which may not be feasible until next year? I know if I settle, I can try to fit the bike to my ideal numbers by decreasing stem length from a 40 mm and get higher rise/backsweep/upsweep of 20 mm/9deg/5deg (setback) as well as possibly more spacers. Any recommendations on specific stems, bars, other things to be able to get the Medium Fathom closer to the numbers of a Small Fathom? Thanks!

    Reply
  9. Anonymous says:

    Hi Lee,

    First of all, what a great article! As a new mountainbiker (ridden since 1 year), the information is very helpful for us to get the sizing dialed. I am planning to buy a new bike and as you mentioned; most of the new bikes are getting longer. I am 162cm tall any my inseam is 73,5cm. According to your calculation factors, most of the Small Frame Size bikes are too long/big for me.

    I have 2 bikes to choose from: Bike A has 395mm reach and Bike B has 414mm reach.
    My height times 2,5 results in 405mm of reach. Due to the fact that we can change the RAD by adjusting the stem, spacer and handlebar, which bike is better suited for me? Bike A or Bike B?

    Many thanks and a lot of appreciations.

    Reply
  10. Risky Mountazea says:

    Hi Lee,

    First of all, what a great article! As a new mountainbiker (ridden since 1 year), the information is very helpful for us to get the sizing dialed. I am planning to buy a new bike and as you mentioned; most of the new bikes are getting longer. I am 162cm tall any my inseam is 73,5cm. According to your calculation factors, most of the Small Frame Size bikes are too long/big for me.

    I have 2 bikes to choose from: Bike A has 395mm reach and Bike B has 414mm reach.
    My height times 2,5 results in 405mm of reach. Due to the fact that we can change the RAD by adjusting the stem, spacer and handlebar, which bike is better suited for me? Bike A or Bike B?

    Many thanks and a lot of appreciations.

    Reply
  11. John Castro says:

    Hello Lee,

    I’m in a bit of a pickle. I’m a new rider and will now upgrade my bike to something more capable.
    I’m 195cm tall, but most of it it’s legs (really long legs).
    I measured my RAD while wearing my bike shoes and simulating the tall stance as if I was standing on my bike, and it came off as 93cm (930mm).
    When I calculated using your formula: 4.47 * 195 = 872mm.
    And my ideal reach would be: 2.5 * 195 = 487.5mm

    The two bikes that caught my eye have the following reaches:
    YT CAPRA size XL reach 480mm and size XXL reach 500mm
    Propain Tyee size L reach 471mm and size XL reach 491mm

    Which one would you pick as being ideal for my body specifications?

    Thank you so much in advance,
    Greatings from Portugal

    Reply
    • leelikesbikes says:

      Hi!

      Based on your measured RAD (and assuming it is accurate), I suggest running the longer bike — the Capra.

      The best way to model a new bike is with the rider/bike calculator at http://www.llbmtb.com. You can input numbers for head angle, reach, stack, stem, bar and spacers, and the calculator tells you the exact RAD for that setup. Do this before you buy, and you can buy with high confidence.

      Rip it up!

      Lee

      Reply
  12. Bill says:

    Hi Lee,
    I have been doing your quick estimate calculation for target reach (188×2.5=470). For the trail bikes I am researching (Specialized / Rocky Mountain / Norco) a Medium frame is in the 450s and a Large frame is in the 480s. Given your suggestion to get as close as you can without going over, do I change my focus to a Medium frame? I guess I am wondering is there a number that is too low from the target reach number? Thank you for your shared knowledge and insight.

    Reply
    • Lee says:

      It’s like The Price is Right.

      Get close without going over. When you go shorter you have lots of options: short and high, long and low and everywhere in between.

      When you go longer, you’re stuck with long and low.

      Reply
      • Dakhil says:

        After playing around with the math all night, I have come to realize exactly what you’ve stated here. Once you go too long in the reach department, you can only lower the bar to get the proper RAD, which could mean an uncomfy seated position and thus a poor compromise. The closer you are to the ideal reach, the less you end up fiddling with other geometry terms. I get higher stack, a less stretched out seated position, and an ideal standing position.

        Thanks a ton for this info! Cannot wait to try it out!

        Reply
  13. TaNec says:

    Hello Lee,

    I would like to ask how much is too much RAD. My Nomad v4 has RAD of 840mm, while my perfect is as measure is 795mm. I think it is very plus plus rad, but what would be the accepted plus RAD without changing frame size?

    Reply
  14. Wayne says:

    Hi Lee,
    I measure my actual RAD as per your video marking the wall and it comes out to be 860mm, my old giant reign is 855mm and fees good.
    I’m 182cm and using the 4.47 multiplier gives me a RAD of 813mm
    Using the calculator on your site once signed up give me a RAD of 804mm

    What do I aim for for new bike purchase?

    thanks
    Wayne

    Reply
    • Lee says:

      Make sure you make an *ACCURATE* measurement of your personal RAD. Almost everyone messes that up and reports a number that’s too big.

      Once you have that number, and you know it’s solid, use the rider/bike calculator inside our member site http://www.llbmtb.com to model the bike in full detail. You enter head angle, frame reach, frame stack and stem/bar info, then you tweak those numbers until you get the setup you want — and you buy with no risk.

      If you like, we can help you 1:1.
      https://www.llbmtb.com/product-category/bike-setup/

      Reply
  15. Rok says:

    Hi Lee,
    I am 187 c tall. I measured my Rad against the wall and its 89cm (guess I have long legs and short arms). As per reach calculator my ideal reach would be 475-480, which would put me on size L for most bikes. While even most XL size bikes would be to small based on my measured rad. So I do not know what to do.

    Reply
  16. Dalton says:

    Bicycles will never go out of style. However, buying a bike is not an easy task because you have to consider many things, like knowing your inseam measurements for the bike. When you are trying to measure your inseam for bike size, you can start by browsing through the inseam measurement chart with its respective bike sizes to find your future bike!

    Reply

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