Modern bike sizing

Exactly, and I would wager the bike Steve is on in that picture is smaller in reach and wheelbase than a modern size small Nomad. According to my googling, the 2024 small Nomad has a 1209mm wheelbase vs. an 1184mm wheelbase on the 2007 V10. I don't know the reach length of the old bike because that wasn't a measurement anyone posted back then, but my 2014 XL V10 had a reach of 447mm so I'm sure the large 2007 was considerably shorter than that. And like the last commenter said, Steve annihilated on that bike and nearly won the overall that year. Looks like great cornering form in the Sea Otter picture to me.

In my experience, the downsides of a bike that are too small are more livable than the downsides of a bike that's too big. If a bike's too long it's an instant confidence killer for me on steep or technical terrain because I feel like I'm in plank position staring at the ground, whereas I can adapt pretty quickly to a bike that's too small and deal with the compromise. YMMV

Santa Cruz did a video on this a few years back. The results were Steve still straight up rips on the old bike, at the ends it was only seven seconds apart, but I expect that is a unique result to him. I highly doubt any current racer could replicate that result just because modern bikes are such a departure from the old ones.

Back to the original question....
I have played around with bike sizing based on different travels and what I want out of a bike. Im 6'1" and have ridden everything from a s3 Specialized to a XL YT Izzo and some stuff in between. I have a s4 Specialized stumpjumper (480mm reach) that we can use for the control bike. I have had the bike for around 1500 miles and have ridden it in a variety of terrain. On specialized's sizing recommendations I can be a s4 or s5. I went with the s4 because this is a bike I will ride on lower speed flatter trails and I wanted to be able to "play" around on it more. It worked really well for this purpose but as soon as I got on a XL YT Izzo (492mm reach) I felt super comfortable. I have not spent as much time on trails yet with the YT but I expect with some of the difference in geo I am going to really enjoy the ride and still have it be a playful experience.

I also have a large Commencal Meta am29 (495mm reach) and on that bike I feel super centered and planted. It is comfortable to push on reacts very neutral to inputs. I would describe it as riding "in" the bike where the s4 spec you are riding "on" the bike. The Commencal really just wants you to drop your heals keep your weight centered and go.

On the other end I have also spent some time on s3 specialized's (435mm reach) and while I can still get the seat post high enough and enjoy riding them, its a semi terrifying ride. With the bike being so much smaller really small changes in body position have large effects on weight distribution front to back. This is really noticeable mid corner where if you end up unbalanced it can push the front end or feel like you are going to tuck the front end and go over the bars. I end up having to ride so central it leaves very little room to roam because any change in body position really negatively effects ride characteristics of the bike.

I think bike sizing is preference but when you start going towards the extremes of your body size it really just stops being enjoyable. I would say shop for the reach and wheelbase you are comfortable with and adjust your controls to fit. Santa Cruz is most likely one of the most "conservative" brands when it comes to sizing as they tend to be a size smaller then other brands. A SC Large would be a Commencal Medium....

I would also seriously consider a mullet as they seem to sit a little more forward, if you look at front center as a percentage of wheelbase they tend to be more forward bias then a full 29. Other people with more knowledge can chime in on this but I believe most bikes are designed around a large frame and then adapted towards larger and smaller sizes from there, this is why you see companies coming out with multi sized rear ends now, also why people debate why stack does not increase proportionally to reach and wheelbase. So I would be a little worried going towards a small with just what compromised may have been made to package everything to fit.  A small and medium megatower have the same rear center most likely because you can't get that travel out of a 29 rear wheel with a shorter rear triangle.

Reach is nothing without Bar height, Normally id say stack but Spacers do the same thing.
Im 6ft currently on a merida one-sixty, It has like 498 reach which is massive compared to other bikes, But im running 30mm spacers and a 35mm rise bar and its spot on, vs other bikes i ran less spacers & longer stem.

 

My understanding was that it was especially the larger sizes that used to be too short. I‘m 5‘6“ and ride a size small with 430mm reach. Proportionally that seems in line with the longer reaches on size L and XL frames for taller riders. Obviously it all depends on body proportions and riding style too.

What's everyone's opinion on Lee McCormack's "Rider Area Distance" sizing?

Basically the distance from the BB to the center of the grips needs to be no longer than the height of your hands standing straight up (deadlift bar height).

Seems like stack tends to be proportionally pretty tall on smaller long travel 29” frames.

Is it correct, in general, to say that smaller bikes should be specced with lower rise bars and larger ones with higher rise ones to end up with a proportionally scaled riding position?

YES THIS OBVIOUSLY BIGGER BIKES SHOULD COME WITH TALLER BARS AND SMALLER BIKES SHOULD COME WITH SHORTER BARS AND IT'S CRAZY THAT IN 2024 MANUFACTURERS AREN'T DOING THAT YET

You could buy from a company like Propain that offers customization. 

Useless without the angle of the distance, so RAAD is what somewhat makes sense. You can have x RAD at 90° or at 0° (bars directly above the BB or horizontally in front of the B and the bike _FOR_ _SURE_ will not fit well. The angle metric changes that.

At the end of the day it's just the result of Stack and Reach, so it's just saying the same thing in different terms. The caveat here is that RAD looks at BB to bar dimension, not top of the headtube, so ideally the headangle, spacers, stem stack, length and angle plus bar roll, rise, up and backsweep play a role in it all. Then RAAD probably has a value. It will give you a meanigful result when evaluating different stem-bar combos and different spacer stacks under the stem.

If it's looked at in the BB to top-of-headtube way, then it's just Pythagoras applied to Stack and Reach.

It’s based on the grips so it takes stem length and all that into it.  The distance and its meaningful value is based on the ability to completely open your hips while not bending your arms to be able to put full power into the bike.  Like an Olympic lift.

A RAD of 750 is not the same as RAD of 750. Because one can be at angle 0deg and the other at 90deg. How open will your hips be with an angle of 90deg?

That's why I said RAD itself is useless and RAAD makes sense.

I don’t think the angle matters as much because the distance is based on a specific body position and the ability to apply power through the touch points.

its a bit fit metric not a bike design metric.

Then why does RAAD exist? 

Any kind of "use this system" to fit a bike should be made illegal - Ride bikes, find what you like, ride that. done.

Do different frame sizes fall under the "system" categorisation? 

I haven't read all the comments, but I'm gonna throw my experience out here:

I'm 1.91 m/6.3” tall and have been riding undersized bikes pretty much all my life, until more recently. I would describe my riding style as ”playful, but nothing crazy”, as in I like to manual a lot and bunnyhop as much as I can, but I am nowhere near Josh ”Loves Back Wheel” Bryceland. I have also broken my elbow 4 years ago, saw my left arm go the wrong direction, which made me way more cautious than before, a thing that I am still fighting/struggling with. So I am pretty average, maybe a tad above, I would say.

My last two bikes before I went to 29” were a 26” Intense Tracer VP in XL (i think it's a 22”) and a 26” Intense M9 in L (that is still larger than an XL V10 of the same year), which accepted 27.5” wheels and a 1 degree AngleSet. I still have both and I love them.

Since then, I have owned A. a 2019 Mondraker Foxy XR alloy in L (495 mm reach), B. a 2020 Specialized Demo S4 (465 mm reach), C. a 2020 Nukeproof Scout XL (475 mm reach), D. a 2022 Mondraker Foxy RR Carbon in L (485 mm reach) and E. a 2023 Rocky Mountain Instinct Powerplay C70 in L (482 mm reach). I sold the Nukeproof and the alloy Foxy and still have the other ones, plus a Cotic SolarisMax in XL, that I still haven't put together. Bear in mind that reach is the only value I have really paid attention to and I tried to keep my bar height consistent, but don't know it by heart. All my bikes are 29” and I don't care about anything else.

Before I bought the alloy Foxy I was juggling with sizes, as theoretically both XL and L would've fit. I rode an XL sized Mondraker ebike though and felt it was too much, couldn't pull a decent manual on it, or pop a bunnyhop. I had initial worries with these on the Foxy too, but they were blown away instantly. The bike felt just as playful as the old 26” Tracer. The only thing I changed from standard was a taller 40 mm Pro FRS bar, on the 30 mm stem. The next year, though, I changed a lot of my parts to new shiny Burgtec ones, that I coveted a lot, including the 35 mm stem, the shortest they have, paired to a Ratboy signature 40 mm bar. On the first ride I realised something was off and the entire behaviour of my bike changed: I couldn't manual, bunny, even suspension felt different. It made no sense. Then I noticed the only geometry difference I made were the extra 5 mm on the stem length. I went back to the old parts and the bike felt awesome again. I bought a Mondraker stem in 30 mm length and 35 mm diameter, so I can use the Burgtec bar. This is the bike I have spent most time on in the last 5 years.

It makes no sense writing too much about the Scout or the Demo. The Scout was way shorter than the Foxy, but it is a different beast and still felt nice. I rode it seldom, so I sold it. The Demo is the largest you can get and it was dirt cheap. I like it as it is. It feels shorter than the others, but has other qualities and the extra travel is obviously forgiving.

I had some initial concerns regarding the carbon Foxy, because the reach was noticeably shorter, but then again the head angle is slacker and wheelbase longer, so maybe it's a fine marriage... And it is! I put the 35 mm fancy Burgtec stem on it from the beginning, so I don't have extra adjustment issues. Love the bike and how it rides and suspension and everything. A lighter, better version of the earlier alloy Foxy.

The bike that brought me a mindfuck, though, is the Rocky Mountain Instinct e-bike. I bought it lightly used from my friend who is a shop owner and it has a longer fork than the standard one, a 170 mm Lyrik, paired to the 145 mm of rear suspension. I took me some time to get used to this bikes, whereas the Mondrakers were instant feel goods, including the Crafty e-bike that I rode for a couple of months before this one. At some point I was pretty bummed that I don't actually ”like like” the bike I spent quite some cash on. But one day it kicked in! And boy I wouldn't want to let go of this bike since then. It rides super smooth, even the suspension feels better than on the Demo, probably because of the added weight of the battery and lowered center of gravity. Since this topic is about sizing, I have had concerns with this bike too, but they proved to be in vain. The 482 mm reach is paired to a 42 mm Burgtec stem and everything is fine. Now the problem is that, since having this bike, I pretty much didn't ride my regular enduro bike anymore. Once I even rode out of guilt. I will probably sell it and buy a Slayer and if the Slayer will feel better than the Demo, I'm gonna ditch the Demo too.

My feeling is that sizes have settled these days. If in the past a lot of us were probably looking at big enough reach numbers and sizing up (hello Trek and Santa Cruz, how are you?), these days everything seems more balanced and it is more likely to find a bike that rides well in the size you should be having. I believe sizing up makes probably sense if you are racing and/or looking for speed. I feel like I am still in between sizes and I used to think a reach of 480+ is not enough, but the bikes I have proved me wrong.

Now should I get a Slayer in L or XL? Hmmm! )))

Cheers,
Mx

The reach is an important value for getting the right size bike for descending but won't hinder climbing if the reach is longer.

There's also the seat horizontal adjustment and the seated reach varies massively between bikes based on seat height and seat tube angle.

Going back to descending, I was giving this some deep thought the other day and believe:

there is an optimum centre of gravity somewhere between the 2 axles and I would imagine we all generally ride in this ,weight loading spread which will vary depending on terrain and descend angle, which part of a corner or shoot we are in etc it's dynamic.

Generally if the reach is longer people adjust their body position to suit and still keep the centre of gravity, when the reach goes too long, the only way back is to raise the bars up which basically has the same affect on the body position as reducing the reach. There's loads crap about geometry, but it's pretty simple, you need to be able to spread your load to keep within the centre of gravity.

Something i've found odd on some bikes, like the Gen 6 fuel, was the shorter headtube but longer reach...
Is the idea behind this purely for upsizing?

I also found the G6 fuel to have quite a flexy front end, This was on the Alloy version. The Merida I currently ride is the same short headtube and long reach but doesnt flex like that

Hi!! i thought you guys could help me since you are very into details. I’ve read the entire convo but it gets too confusing for me, I know you guys already asked some questions about this. 
I’m planning on getting a Demo (2023) but i am wondering what size… Size chart says i should be riding s2 but i’ve ridden s3 very comfy, I’m about 1’63m ~ 5’34 ft… last years i’ve been riding a mondraker summun (2021) size S and feels like the s3 so it’s quite big

Last week got on a s2 from a bike shop (but couldn’t ride it obviously) and it felt too small

The use I’m going to have is for racing and i’ve always heard that a bigger bike is better for it but yeah i am having trouble on deciding

Thank you guys!!

The reach and stack of the S2 Demo is very close to the Small Summon.  I'd recommend S2.  The S3 I would think would be hard to maneuver around in terms of lifting the front wheel.  I've found that on bikes with longer reach.  

On a downhill bike the key numbers to look at are reach and stack, this shows what it would feel like descending.  A trail bike I look as well to "Effective Top Tube", but doesn't take into account your seat height well.  

In my experience, the downsides of a bike that are too small are more livable than the downsides of a bike that's too big. If a bike's too long it's an instant confidence killer for me on steep or technical terrain because I feel like I'm in plank position staring at the ground, whereas I can adapt pretty quickly to a bike that's too small and deal with the compromise. YMMV

Can confirm this one about bikes being too large. 

Hi guys! Just coming here to say that I ended up getting a Demo s2 and I am so so happy about how it turned out. I don't feel it small, I feel it just perfect. Reminder, I am 162-163 cm, so anyone that comes after me with the same question has the answer Thanks to those who have helped! Means a lot.

That's awesome! Glad to hear it's working out for you. Great bike and it sounds like you're stoked.

6'3 +3 ape

2024 xl v10.8

2023 XXL nomad V6

2024 XL slash gen 6

About damn time after 23 years riding and racing DH that bikes actually fit...I made all bikes in past look like a circus bear riding a bike..Still plenty fast and moveable, but the extra room in cockpit is AWESOME..

Had the same though with similar sizing going to an XL Bird (525 mm reach) 5 years ago. Then downsized last year. Could likely go to an even smaller bike to be honest... 

Been riding 510-520mm reach bikes since 2016 after moving up from 450mm. Can't see myself ever going shorter. I'm 5'11'' (180cm) with regular arm length. Only thing I would like is longer chainstays (currently on 462mm) to make the bike more balanced. I plan on having a custom frame made with 480-500mm chainstays which should make the bike feel much better. I ride a 20mm stem so my effective reach is the same as 50mm stem with 480-490mm reach. Have tested -10mm and 10mm stems too both work well but 20mm feels best.