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Reach and Stack - Oh good, it has been a while without another new standard to learn

mandown

mandown

Poopdeck Repost
Jun 1, 2004
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Transylvania 90210
Saw this today and thought I should pass it along. :clue:

http://www.pinkbike.com/news/08ReachStackStandard.html

December 18, 2008

News Source: Transition Bikes
In a joint effort between Turner and Transition bikes, a new standard for mountain bike frame sizing has been introduced. This new standard is based around reach and stack measurements, and is intended to clarify bike fit across bike models and brands.
The evolution of mountain bikes has made the old system of top tube and seat tube based sizing irrelevant. The wide range in seat tube angles and bottom bracket heights can create a situation where one bike could feel longer or taller than another frame with the same measurements. Once a rider is in a standing position, the fit and feel of their bike's cockpit is determined exclusively by the handlebar and pedals. Finding the specific geometric relationship between those two points is the only way to accurately compare the fit and feel of different bicycle frames.

“I was really stoked to get the call from Sam at Transition Bikes regarding a new method of measuring mountain bikes, especially those used for technical riding like our DHR. For years I have not listed a top tube measurement for the DHR as I knew it was irrelevant in comparing the fit of our bike with other brands,” says David Turner. “The great thing about this sizing method is that anyone with a piece of string with a weight on it and a measuring tape can accurately measure their current bikes. The rider can then compare their current bike to any brand using Reach and Stack and know exactly how it will fit without even riding it.”

The horizontal distance from the bottom bracket center to the top of the headtube centerline is referred to as reach. The vertical distance between these two points is known as stack. By comparing the reach and stack on different frame models, the rider is able to identify exactly how their bike will fit and feel on the trail. This system eliminates any uncertainty created by the seat tube angle, and forever drops the need for “actual” and “effective” top tube measurements. The reach and stack of a frame is the most important sizing information for a freeride or downhill rider but it is extremely valuable for trail riders and XC racers as well.

“I was aware that Turner was using the reach number to size their DHR, but under the name cockpit; so I approached David Turner with the idea that this should be an industry standard measurement,” said Sam Burkhardt from Transition Bikes. “Dave expressed interest in adding a vertical component and going forward with an industry standard. We chose the terms reach and stack after Kris Wehage from E.13 Components pointed out the use of the same measurements in the Time Trial and Triathlon communities. Rather than create a new name, we felt it would be easier for manufacturers and riders to adopt the system using existing names.”

Turner and Transition bikes encourage all mountain bike manufacturers to include these numbers on their specification charts for consistency in the industry, and to aid rider's looking for the best possible fit for their body type and riding style.

 
Prettym1k3

Prettym1k3

Turbo Monkey
Aug 21, 2006
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In your pants
After working in the bike industry for a little over a year, and selling all sorts of bikes, this is fantastic.

Way to go Turner and Transition!
 
gemini2k

gemini2k

Turbo Monkey
Jul 31, 2005
3,526
117
San Francisco
Wow, Finally. Me and other have been talking about this forever. This has to be like the single nicest change in standard ever.
 
buildyourown

buildyourown

Turbo Monkey
Feb 9, 2004
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South Seattle
Stoked said:
front-center measurements have been around...am i missing something?
Click to expand...


Front-center sucks for mountain bikes because they are tied to headtube angle. 2 bikes with the same F-C and different HA, will have drastically different cockpit sizes. It works great on a road bike where almost every bike is 72 deg. Mountain bikes are anywhere from 71-64 these days.

I knew Turner had been advocating for this for awhile. It's good to see other people getting in line. Way to be Sam.
 
Jeremy R

Jeremy R

<b>x</b>
Nov 15, 2001
9,698
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behind you with a snap pop
Great idea.
The best thing about this standard is that does not cost any money to use it.:brows:
They are not trying to sell you anything extra, they are just trying to give riders correct numbers so they can make a decision on which bike suits their needs.
 
Westy

Westy

the teste
Nov 22, 2002
54,394
20,186
Sleazattle
Sweet.

Actually I think it would be easy to develope an application that would allow someone to get whatever measurment they want from a bike frame. Kind of like a little CAD program.
 
D

davep

Turbo Monkey
Jan 7, 2005
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seattle
Jeremy R said:
Great idea.
The best thing about this standard is that does not cost any money to use it.:brows:
They are not trying to sell you anything extra, they are just trying to give riders correct numbers so they can make a decision on which bike suits their needs.
Click to expand...
exactly!!

It does not require you to buy two different headsets or lock you into OEM forks(E2), a new set of cranks(hammerschmitt, flytrap), new hub (15mm fork), etc, etc...


Just a simple way to measure and compare frame sizing for the riding that 'we' do.
 
G

General Lee

Turbo Monkey
Oct 16, 2003
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Jeremy R said:
Well, the Reach Around was already taken.
Maybe you have heard of it.....
It is the new Lahar Reach Around frame.
You give him $2000 and that is the least he could give you.
Click to expand...

he would if he didn't need both hands to stuff your money in his pockets as fast as he can. And as if that isn't bad enough, he doesn't cuddle and he doesn't return your calls either.


new standard (the first standard really) is a fantastic idea. no excuse for bike companies not to get on board.
 
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ohio

ohio

The Fresno Kid
Nov 26, 2001
6,649
24
SF, CA
It's a great move and I definitely agree a more accurate measure of bike size, however I think it was a bad move to tie the measurement to plumb and level. Put a longer or shorter fork on there and the numbers change, making it tough for someone to compare frames without whipping out the pythagorean theorum.

I would have used the actual distance from BB-center to HT-toprace-center (the hypotenuse of reach and stack) and the angle of that line from level (or plumb). That way if you change forks, the distance (size) stays the same and only the angle (rider position) changes.
 
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8

819

Monkey
Mar 12, 2003
143
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I think it's a great idea. It would be nice if they went even further and measured BB height/wheelbase/headtube at suggested sag (yes I know everyone has their preferance on sag, but I'd imagine the bike was designed around a given amount of sag).
 
D

dw

Wiffle Ball ninja
Sep 10, 2001
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MV
ohio said:
It's a great move and I definitely agree a more accurate measure of bike size, however I think it was a bad move to tie the measurement to plumb and level. Put a longer or shorter fork on there and the numbers change, making it tough for someone to compare frames without whipping out the pythagorean theorum.

I would have used the actual distance from BB-center to HT-toprace-center (the hypotenuse of reach and stack) and the angle of that line from level (or plumb). That way if you change forks, the distance (size) stays the same and only the angle (rider position) changes.
Click to expand...
I agree totally, I like the idea of this measurement that you propose, and things like it have been discussed many times between many frame engineers. I use the BB center to top cup measurement (I call this upper downtube length), along with the top cup to wheel center (roughly AC height+lower stack+head tube length) coupled with front center to give a triangle of feet to hands to wheel center. This allows somewhat repeatable and easily measurable geometry that can be used to compare bikes using varying AC height forks. I used this method when I designed the Type 6 SSO, which was a 6" downhill bike with identical ergonomics to a Sunday. If you looked at the head angle/ tt/ etc.. geometry on paper you would say it was totally different, but when comparing the UDT length etc.. and riding the bike, they are very similar.

It's a step in the right direction, and I know that you will see more of this type of thing from several manufacturers in the future.
 
G

General Lee

Turbo Monkey
Oct 16, 2003
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i agree with you DW, but can you imagine a bike shop employee trying to describe that to the average joey? seems like the current suggested 'standard' is at least a bit more user friendly, the downside is that it is really only useful when comparing bikes with similar fork ac height. so all the dh bikes might be compared to each other, and all the 6" trail bikes might be compared with each other, but comparisons across a range of different models isn't going to work out too well.

do you think, though, that if the stack/reach standard catches on we will eventually learn to differentiate the measurements between different models much like we already do in terms of bb height, head angle, wheelbase, etc on dh, freeride, and trail bikes?

for dh we should just have the 'sunday' standard. since just about everyone has ridden one it can be the standard and other frames geometries can be described in terms of their deviation from it. Dirt does it already, but with the 224 :cheers: (obviously i'm just kidding)


**edit. out of curiosity sake it would be interesting if people measured their own bikes this way and we could start a thread with the stack/reach of some of the more popular frames already on the market. would certainly be easier than waiting for the bike companies to do it.
 
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L

limitedslip

Monkey
Jul 11, 2007
173
1
ohio said:
It's a great move and I definitely agree a more accurate measure of bike size, however I think it was a bad move to tie the measurement to plumb and level. Put a longer or shorter fork on there and the numbers change, making it tough for someone to compare frames without whipping out the pythagorean theorum.

I would have used the actual distance from BB-center to HT-toprace-center (the hypotenuse of reach and stack) and the angle of that line from level (or plumb). That way if you change forks, the distance (size) stays the same and only the angle (rider position) changes.
Click to expand...
 
Spunger

Spunger

Git yer dumb questions here
Feb 19, 2003
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805
Jeremy R said:
Great idea.
The best thing about this standard is that does not cost any money to use it.:brows:
They are not trying to sell you anything extra, they are just trying to give riders correct numbers so they can make a decision on which bike suits their needs.
Click to expand...
Thats exactly what it is and thank god some other companies are picking up on this. Everyone knows how frustrating sizing a bike can be. And once you've made that purchase it's yours once you build it up.

Information is always good. Might save someone from making a mistake sizing up a frame.

I wish they would do the same for wetsuits. I just got a new one but tried on 5 different brands which all fit differently, where a L in one is a XL in the other. They need a standard as well :)
 
O

Old_Sckool

Monkey
Jun 5, 2007
187
0
Funny how times change. I got in a HUGE flame war 4 or 5 years ago on MTBR.

A question of what length toptube came up on the downhill forum and I commented that the TT didn't matter as much on a DH bike, what was important was the downtube measurement, since this determined cockpit size for a standing rider.

Very few people got it. It turned into a massive multipage thread 10 to 1 arguing how wrong I was.

Based on this thread, I'd say it looks like people get it....now.:cheers:
 
RUFUS

RUFUS

e-douche of the year
Dec 1, 2006
3,480
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Denver, CO
Old_Sckool said:
Funny how times change. I got in a HUGE flame war 4 or 5 years ago on MTBR.

A question of what length toptube came up on the downhill forum and I commented that the TT didn't matter as much on a DH bike, what was important was the downtube measurement, since this determined cockpit size for a standing rider.

Very few people got it. It turned into a massive multipage thread 10 to 1 arguing how wrong I was.

Based on this thread, I'd say it looks like people get it....now.:cheers:
Click to expand...
I cry BS.
That never happens on the information super highway.
 
EVRAC

EVRAC

Monkey
Jun 21, 2004
757
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Port Coquitlam, B.C., Canada
My only complaint is that these are terms used already to describe stem and headset geometry. I thought for sure from the title that this would be a new stem measuring standard.

The days of 90mm by 10 degree rise should have died when stems stopped being made from welded tubes. This is especially true for bolt on stems. They should be specified by rise ( parallel to the steerer, above the crown ) and by reach (perpendicular to that). It would clear up a lot.

Oh, well.
 
SuspectDevice

SuspectDevice

Turbo Monkey
Aug 23, 2002
4,161
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Roanoke, VA
Dan at www.slowtwitch.com has a whole database of Stack and Reach measurements for tt and tri bikes. I think he coined the term 5-6 years ago. The nice thing about doing it this way vs. bb center to top headset center is that you have a measurement defined by 2 points. It'd be nice to see it catch on for gravity stuff.
 
ohio

ohio

The Fresno Kid
Nov 26, 2001
6,649
24
SF, CA
SuspectDevice said:
The nice thing about doing it this way vs. bb center to top headset center is that you have a measurement defined by 2 points.
Click to expand...
Errr? Both methods use the same two points AND reference vector (level or plumb). It's the difference between measuring the legs or the hypotenuse...
 
Sam B

Sam B

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Nov 25, 2001
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SuspectDevice said:
Dan at www.slowtwitch.com has a whole database of Stack and Reach measurements for tt and tri bikes. I think he coined the term 5-6 years ago. The nice thing about doing it this way vs. bb center to top headset center is that you have a measurement defined by 2 points. It'd be nice to see it catch on for gravity stuff.
Click to expand...
Exactly. That is where the name came from. I did not know if slotwitch actually coined the term, but clearly they advocate their use. It is a bit unfortunate that the term stack applies to stems, etc as well, but oh well...

And yes, reach and stack are not the only numbers that matter, probably not even the most imporant in how your bike handles. They are more logical than top tube length and headtube length when combined with CS length, wheelbase, head angle, etc.

And yes, some people get hung up on this one - axle to crown does change the data. But it changes head angle, wheelbase and everything else. Always need to know what a-c was used for the numbers.
 
SuspectDevice

SuspectDevice

Turbo Monkey
Aug 23, 2002
4,161
368
Roanoke, VA
ohio said:
Errr? Both methods use the same two points AND reference vector (level or plumb). It's the difference between measuring the legs or the hypotenuse...
Click to expand...

Do they? I'm a bit undercaffeinated and over distracted, and leave trig to other people, but how is the measurement of ONE line defined by two endpoints the same as the measure of two lines from an intersection?
 
D

davep

Turbo Monkey
Jan 7, 2005
3,276
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seattle
They are the same as the two lines intersect at a 90* angle (plumb and level in this case) and thus the two lines define the diagonal exactly. They are the linearly independant components of the diagonal based on the coordinate system imposed on the frame.
 
G

General Lee

Turbo Monkey
Oct 16, 2003
2,860
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The 802
SuspectDevice said:
Do they? I'm a bit undercaffeinated and over distracted, and leave trig to other people, but how is the measurement of ONE line defined by two endpoints the same as the measure of two lines from an intersection?
Click to expand...
as long as i've know you when are you not undercafeinated and overdistracted, Mickey;)

as for the trigonometry, it's more like basic geometry. brush up on your pythagorean theorem to see how all three measurements (stack, reach, and bb to hs) are all expressions of the same thing. and have another espresso.
 
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G

General Lee

Turbo Monkey
Oct 16, 2003
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The 802
davep said:
They are the same as the two lines intersect at a 90* angle (plumb and level in this case) and thus the two lines define the diagonal exactly. They are the linearly independant components of the diagonal based on the coordinate system imposed on the frame.
Click to expand...
man, where were you 3 weeks ago when i had to teach A squared + B squared = C squared. that definition would have made 13-year-old heads explode.
 
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