[bikinson]

Hello everybody. I would like to hear your opinion about how modern bikes are getting longer in reference to their suggested rider size, specifically in the reach and wheelbase measurements. I am also curious if anyone has heard of the bike fitting measurement called RAD (rider area distance) that Lee Mccormack invented. These two ideologies seem to be at odds, so I think it would be great to hear your personal preference of bike length for your specific body type.


I know that every rider has a different anatomy, muscular structure, and riding style, which is what interests me. It seems that "modern" geo favors downhill, straight-line, stability, while RAD favors maneuverability and control. Please list your height and bike measurements (reach, wheelbase, size) along with any objective, subjective, anecdotal, scientific, or empirical analyses regarding length and sizing for the community to digest.

 

[Fleas]

More here:

https://forums.mtbr.com/general-discussion/lee-mccormacks-perfect-bike-setup-1094401.html

-F

 

[bikinson]

Hmm yeah, that thread is pretty similar to what I was asking. I guess I was more curious on how much reach is desirable for everyone, given their specific height (and not so interested their actual RAD measurements). But thank you, I will enjoy reading through that!

 

[Harold]

I think if you want to get the information you're after, you're going to have to create a specific survey with the specific questions you want answered. You just won't get anything useful from people who are just free-forming the answers.

For that matter, I'm not even sure I know how to answer your question completely the way you want. I have two mountain bikes.

medium Guerrilla Gravity Pedalhead, reach is 451mm but I can't give you the other numbers because they're based on a 120mm fork and mine has a 140mm fork
medium Salsa Bucksaw, reach is 436.7mm but again none of the other numbers are exact because I'm using a slightly longer fork than stock

I'm 5'8 with a longish torso and long arms. Both bikes feel good. I look for some level of balance between stability and control and I feel like I am in that ballpark with both of these bikes. I don't dwell on numbers when it comes to fitting a bike. I focus on what feels right. So I haven't calculated RAD for any bikes I own. The whole concept seems rather contrived, anyway.

 

[s-master]

medium Guerrilla Gravity Pedalhead, reach is 451mm but I can't give you the other numbers because they're based on a 120mm fork and mine has a 140mm fork
medium Salsa Bucksaw, reach is 436.7mm but again none of the other numbers are exact because I'm using a slightly longer fork than stock

To be honest, RAD measurement doesn't change with different size fork. Same frame, longer fork, shorter reach, higher stack, but RAD is the same.

 

[Harold]

To be honest, RAD measurement doesn't change with different size fork. Same frame, longer fork, shorter reach, higher stack, but RAD is the same.

No, but that's not what OP asked. He wanted reach, wheelbase, and size.

 

[vikb]

Please list your height and bike measurements (reach, wheelbase, size) along with any objective, subjective, anecdotal, scientific, or empirical analyses regarding length and sizing for the community to digest.

Asking for Reach without asking for Stack is pretty meaningless as Reach depends on Stack so two bikes can have the same Reach, but be different sizes due to varying Stack values.

 

[bikinson]

Stack would be cool to know too. I said reach and wheelbase because these can vary a lot and are not easily changed (whereas seat post related measurements and stack can be adjusted with an Allen wrench). But honestly, I was just interested in what sizes/dimensions people are riding nowadays, and how they feel about these sizes/dimensions. So I welcome any information riders wish to provide!

 

[vikb]

Stack would be cool to know too. I said reach and wheelbase because these can vary a lot and are not easily changed (whereas seat post related measurements and stack can be adjusted with an Allen wrench).

Stack is a function of the bike design and never changes once the bike is built. You define Reach by the frame's Stack you can't really understand Reach if you don't have Stack as well.

 

[Phillbo]

6'4" riding an XL ...

 

[33red]

Forget about new, old.
My legs are way too long.
My bikes are way too long.
I reverse seatpost to shorten the frame.
When that fails, i cut frames then glue back.
620 mm handlebars.
Ya i am not average but with a good position i go up, down and turn.
The idea is 95 % is about the rider, frame BS is if you hope
your bike will turn u in an expert.

 

[bdundee]

Stack is a function of the bike design and never changes once the bike is built. You define Reach by the frame's Stack you can't really understand Reach if you don't have Stack as well.

This^^^

 

[planetx88]

Reach and stack are important, but I find that some perspective is important in understanding the fit of modern bikes that seem to all be converging on steeper seat tubes, and slacker headtubes.

I am 5'11" riding a gg megatrail v3 with a stated factory geometry with a 482mm reach for a size "3", basically a large. Below are numbers comparing bikes I have ridden in the past few years, plus a pole stamina 180, just for fun.

5010 v2 LG- reach-445, stack-605, tt-621, seat angle-73.8
Evil Calling MD- reach-440, stack-601, tt-603, seat angle-74.8
Evil Wreck LG- reach-455, stack-611, tt-640, seat angle-72.8
GG MT size 3- reach-482, stack-627, tt-625, seat angle-77.1
Pole stamina LG- reach-510, stack-645, tt-630, seat angle-80

So reach and stack are important, but steep seat tubes can skew reach numbers longer without representing a stretched out riding position. In a lot of ways, thats the whole idea behing this "foreward geometry" trend. top tubes remain nearly unchanged, while they are pushed foreward by steep seat tubes. Another way to look at this is if I shopped for bikes on reach/stack alone, shooting for 440mm/610mm zone at 5'11" (which has fit well on previous bikes), I would concievably be looking at a small Megatrail or Pole, and even a Medium in the new v2 Hightower or Yeti SB150 would be a touch big.

That is a very long winded way of saying reach/stack can be important, but are not entirely how we should size bikes. My personal belief is pushing a rider forward more closely replicates an "athletic position," putting the rider in a more dynamic and comfortable position, but maybe not for everyone.

 

[bdundee]

That's why when I'm looking at a frame effective top tube is just as important at least for myself and my type of riding. A bike is a sum of all numbers and just can't just summerized by just a couple of measurements.

 

[bikinson]

What about when you’re not in the seated position and top tube is irrelevant? At what point is the extended reach and wheelbase overkill? At 5’10”, I’m unsure if I should be around 450mm/1200mm or 470mm/1220mm. I’ve done test rides but without a lot of experience it’s difficult to evaluate in that short amount of time.

 

[bdundee]

I'm 5'9.5" on a medium offering and with around a 450mm reach with around a 1200mm wheelbase and a 50mm stem ( I have long legs and arms) and it feels great from the tight singletrack as well as park riding. I also spent the last couple of years on a Kona Wozo with about the same geo but higher stack. Now with let's say an Ibis Ripmo with roughly the same numbers ( lower stack and a tad shorter tt) felt cramped seated. For me Ibis bikes have always felt smaller than their numbers show and I'm thinking some of that has to do with stack height.

 

[vikb]

That's why when I'm looking at a frame effective top tube is just as important at least for myself and my type of riding.

I size bikes based of eff TT and Reach/Stack. I need them to fit me well seated and standing. I don't have an exact magic formula, but I use existing bikes to get a feel for what I am comfortable with. Then between stem/bars/steerer spacers I can fine tune the fit once I have the bike at home.

What about when you're not in the seated position and top tube is irrelevant?

 

[Harold]

What about when you're not in the seated position and top tube is irrelevant? At what point is the extended reach and wheelbase overkill? At 5'10", I'm unsure if I should be around 450mm/1200mm or 470mm/1220mm. I've done test rides but without a lot of experience it's difficult to evaluate in that short amount of time.

Top tube length isn't irrelevant when you're in a standing position. It's not the focus at that time.

Honestly, there's not enough information presented here to say what you SHOULD be riding. Figuring that out requires more information about your body than just your height. Do you have a longer torso, or longer legs? What is your arm length? How flexible are you? How is your core strength? Those things are all going to affect what feels best to a rider, especially when you're in a standing position.

Mountain bike fitting has some wiggle room. What matters is that it's comfortable. If you have less experience, dwelling on the numbers is going to add to confusion. And for that matter, if you have more experience, dwelling on the numbers can be exhausting, too. What matters is that it's comfortable. Forget the numbers for a minute. If both bikes feel good, you're comfortable on them, and you like them, then you should just pick one. Buy it, ride it for awhile, and get to understand it deeply. It'll inform you for later. Maybe you'll decide after awhile you don't like it. Maybe you'll decide after awhile you love it. Maybe you'll be somewhere between and want to try something a little different anyway.

If you can't separate yourself from the numbers and want to buy something that's "perfect" then go pick a custom framebuilder and spend the money.

 

[vikb]

.... and I'm thinking some of that has to do with stack height.

Yes. And that's exactly why looking at Reach separate from Stack makes no sense. You can get two bikes with the same Reach, but different Stack measurements that fit quite differently.

 

[Fleas]

Maybe a little OT... but maybe helpful....

https://www.ridefatbikes.ca/fat-bike-stack-and-reach#sr-1

-F