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Discussion Starter · #1 ·
I was just introduced to the concept of rider area distance (RAD) on Jeff Lenosky's YouTube channel. RAD is the length from bottom bracket to handlebar. It's the hypotnuse of the triangle created if you connected the stack and reach to form a triangle.

The RAD idea was first proposed by Lee Likes Bikes (LLB) who has proposed the formula: RAD = rider height * 4.47

Supposedly with MTBs getting longer RAD numbers are getting out of whack.

I'm 5"10" and ride a size M bike. The bike manufacturer's chart say 5'10" overlaps with L so you'd think M would be a little small. But my RAD is a 791mm and my bike measures 844.5mm from BB to bars.

Lenosky says he agrees with LLB for full suspension bikes but actually likes his hardtail shorter than what LLB's RAD suggests because of the way a hardtails suspension makes it longer whereas the full suspension bike's suspension makes it shorter. That would make my hardtail that's already too long even longer.

I was just curious to see what other people thought about this RAD concept and how their RAD and actual measurements compare.
 

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I have a long torso in relation to my legs so I wonder if this captures it better
 
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Even if long enduro bikes had similar RAD, their long wheelbases would make techniques require more force to pull off. That's part of the benefit of the long wheelbase, to make the bike more numb to input forces, like a rock or other obstacle smashing into the wheel. When the bike feels calmer, you feel like you have room to go harder.

The bike is built to be optimized towards a certain kind of riding. Building around a # like RAD, HA, ETT, STA, or whatever has its own trade-offs. If I downsized because the RAD was too long, it'd probably compromise the seated position's comfort, perhaps leading to excess pressure on the hands and butt. Since the RAD is correct, I'd and the reach is familiar, I'd be left to blame something like the steep STA or maybe accuse modern geo as going the wrong direction since it makes choosing a bike with proper RAD in your size very hard.
 
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Discussion Starter · #4 ·
Even if long enduro bikes had similar RAD, their long wheelbases would make techniques require more force to pull off. That's part of the benefit of the long wheelbase, to make the bike more numb to input forces, like a rock or other obstacle smashing into the wheel. When the bike feels calmer, you feel like you have room to go harder.

The bike is built to be optimized towards a certain kind of riding. Building around a # like RAD, HA, ETT, STA, or whatever has its own trade-offs. If I downsized because the RAD was too long, it'd probably compromise the seated position's comfort, perhaps leading to excess pressure on the hands and butt. Since the RAD is correct, I'd and the reach is familiar, I'd be left to blame something like the steep STA or maybe accuse modern geo as going the wrong direction since it makes choosing a bike with proper RAD in your size very hard.
I think one of the points Lenosky makes is the recent fascination with long and slack, enduro-influenced geometry has made it harder to find bikes that fit in a traditional, well-rounded sense. Too much enduro-specialization sacrifices all-around performance.
 

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Not necessarily. Bikes have longer reach, but stems are shorter too. 35-50mm stems are the norm, compared to 80-90mm a decade ago. And even longer before that. This ~40mm difference is in the ballpark of the difference in reach.

RAD is an approximation, reach + stack to the handlebars paint a more accurate picture. For example, on one of my bikes my the bar was too high, not RAD too long. Shorter stem would have the opposite effect of lowering the stem (but they both would have the same RAD effect).
 

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I think this is way to serious a bike related topic to be in the OC. I'm now going to have to go off and check all of these dimensions to see where my latest build sits. Although completely different geo to my hardtail, I sized the frame so that I could keep seat clamp to centre of bar and bb to centre of seat clamp the same as my hardtail without the use of an offset post. I have achieved that and yet the two bikes assume completely different seated feels.I'll come back with more detail later.

Other than that, all I can say is all of my bikes have always been RAD to the MAX
 

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I think the height based formulas aren't accurate enough. There was a video Lee was in where he showed how to measure RAD directly and I found this much more useful because it accounts for everything (height, arm length, inseam, etc). At 6'5" my calculated RAD is way smaller than my actual RAD. I was surprised to find that my gigantic XXL Santa Cruz is about 1" below my RAD. Also, his bar width calculation says my max bar width would be 860mm!

 

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I've watched these videos and like everyone here got to thinking how does my current bike fit me? Well I did the ladder test and the RAD equations and my bike came up pretty much spot on. My bike felt like a great fit from the first day of building it. Now I think these equations are good for your average trail riding especially tech and tight switchback trails. Which are my typical trails, I find that for where I ride a wheelbase of less than 1200mm is the best. Now for fast flow trails I could see a longer wheelbase and reach being more advantageous.
 

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In reading both threads I see a consistent misunderstanding of what RAD is and how to measure it. I bought the book "Dialed" and it definitely explains this in detail.

That said, the book includes recommended reach measurements that are outdated. Reach is relative to the seat tube angle and older bikes at 72*, for instance, have shorter reach than a 75* STA new bike with longer reach.

RAD is simply the distance between BB and the top-center line of the handlebars. Regardless of your bike design, it's supposed to be the same. RAAD, or the angle of your RAD, is adjustable considering whether you are a DH or XC rider, but RAD should be the same.

In studying the book I shortened my stem to a stubby 35mm AND threw some backsweep in to get down to the shorter RAD I needed on a bike with 505mm reach. It feels great--the idea is that your bike is more maneuverable and you have some slack in your arms to handle terrain and cornering better. Too stretched out and you can't control the bike adequately.
 

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I think the height based formulas aren't accurate enough. There was a video Lee was in where he showed how to measure RAD directly and I found this much more useful because it accounts for everything (height, arm length, inseam, etc). At 6'5" my calculated RAD is way smaller than my actual RAD. I was surprised to find that my gigantic XXL Santa Cruz is about 1" below my RAD. Also, his bar width calculation says my max bar width would be 860mm!

I suspected my bike was a bit long from how it felt at pump tracks and flat corners and stuff. So I did the on the bike check by paying super close attention to this part of the video of where the knuckles are supposed to be (behind the middle of the grips) and how to do your posture with the on the bike check, and confirmed that my knuckles were about 40 cm below the center of the grips:

I think the on the bike check is the best way to go to see if your bike setup is too long vs all the measurements and multipliers, as you can't mess anything up except your posture. I used barstools with some plastic beneath the pedals to prevent damage. Once you are convinced by the on the bike check, and want to move forward, I found that measuring my height really carefully in cm made a difference for the next step, because I had rounded up my height in inches and stuck with that number for a long time, even though it wasn't quite right.

For me, the multiplier formula for RAD is a few mm too large vs the on the bike check, but there is "rider and bike calculator" available on his site if you sign up for a free month that agreed with the on the bike check pretty closely, and helps you pick out a stem and handlebar if you can use the handlebars that people have measured setbacks for (some good ones for me there). I swapped to a 30mm stem and 15mm rise handlebars and the bike feels easier to corner and hop, and it felt fine on a steep loose trail. But, I had waited until my stock handlebars and stem were 3 years old, and I wanted to replace them anyways for safety, since they had hit the dirt many times.

As far as the recommendations for bars over 800mm in width for people a few inches over 6', he answers this question a lot, and says that bigger number is just a max for people, and usually people go a little bit below the max, like with RAD. I went with 800mm instead of the ~830mm recommendation, even though 820mm bars exist, because I couldn't find a 30mm stem that was rated for more than 800mm bars.
 

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I think mtb "fit" is a scam. Bikes fit trails to a pretty large degree.

Crazy low, slack bikes pop up around the time that flow trails get huge. Low bb's rip on flow trails. "Back country" used to be kind of popular, and a 14" bb was great for crawling over huge rocks on an unestablished trail.

If OG nasty slow chunk trails get popular again, someone will "revolutionize" fit again and bikes will change. We'll all wonder how we ever rode LLS bikes.
 

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Rippin da fAt
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I think mtb "fit" is a scam. Bikes fit trails to a pretty large degree.

Crazy low, slack bikes pop up around the time that flow trails get huge. Low bb's rip on flow trails. "Back country" used to be kind of popular, and a 14" bb was great for crawling over huge rocks on an unestablished trail.

If OG nasty slow chunk trails get popular again, someone will "revolutionize" fit again and bikes will change. We'll all wonder how we ever rode LLS bikes.
Have to laugh at the whole thing...

Frankly, my slack, high BB bike with a stack that doesn't require slumping over to grip the bar does me dandy! I hate the hell out of having to call AAA to get a bicycle that high centered on a speed bump in front of the corner package store...
 

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43yo noob recently began jumping and such, all very tame small stuff. Working on manuals and wheelies. 6'3" on XL Hardtail that was rad+ by the recent joy of biking video approach. I went with a shorter stem, bars with more back sweep, and moved some of the spacers around. Ended up slightly rad- and I am enjoying the change. No issue feeling cramped in cockpit pedaling and am able to generate noticeably more torque. Will I fiddle with it some more, yeah that's part of the fun, but count me as a rad fan.

On related note, did anyone notice how high Lee kept his seat when working the technical climbs in the video this week? I realize his understanding and ability is 1000x mine but that's not my approach to those sorts of things. Get that seat out of the way :) I'm probably using 10x more energy while he's 10x more successful lol, but still, drop the dropper for more chi bud.

Joy of biking videos have been solid for me in my learning stages.
 

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My RAD is about 80cm actually measuring myself. One bike is just about spot on...the other bike is about 1cm short. I measured my GF and she is about 78cm. The RAD on her bikes are both about 81cm.

The thing is that out of the four bikes in the garage...the one that has the longest reach...measured the shortest. All bikes have a 50mm stem. The Ripley V3 LS and Spesh Stumpjumper (411 and 413) both have fairly short reaches...but both have the longest RAD. The V1 Evil Following (feels like it fits me best) has a 419 reach and Banshee Spitfire V2 has a reach of 430. All bikes are mediums.

I'm also thinking about trimming my bar down from 760 to 740.
 

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I'm going to have the unpopular opinion about reading what you someone says in a fit that works for everyone. it doesn't fit everyone. Everyone is built differently.

If you're interested in getting fitted, go pay a reputable fitter for mountain bikes and get fitted for your bike. This way they can SEE you and how you move. Not just plug in random numbers from a formula online and this is your fit.

The RAD concept fit is a one-size fits all, and does not take into account any mobility issues you may have, weird things that go on with your body, nor does it take into account a seated bike position. I know, because I've done this with Lee before (had several in-person sessions with him, including the whole step ladder thing), and it still ended up not benefiting me. Lee's got a good idea, but it doesn't match a lot of the newer geos, so he suggests sizing down. I ended too crunched up, which did nothing to help my spine or hips. Don't assume that this is one-size that fits you. He looks for specific movements on the bike, but he doesn't watch the way your spine and hips behave on the bike even when you do this in person. Nor does every person my height want to run 740mm bars and a 40mm stem, ugh.

Full disclosure: I like Lee, and I think he's a fantastic skills teacher. He taught me how to pump, and helps me refine other things (I have another clinic with him in a couple weeks). But I did tell him he's not allowed to ever talk bike fit with me, so we agree to disagree on his RAD principle.
 

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I'm going to have the unpopular opinion about reading what you someone says in a fit that works for everyone. it doesn't fit everyone. Everyone is built differently.
Fitting a bike is very much like trying on shoes. The size charts, construction, style, value, and reviews might all seem right but you don't really know anything until you slip 'em on, lace 'em up, and take a couple steps.
 
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