Reach and Stack : A Good Idea
There are a few guys already doing this… but many more should be. Introducing reach and stack based sizing for mountain bikes (especially gravity ones). Expect to see many more companies on board, you should too if you’re a bike manufacturer. Details inside.
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 are encouraging 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.
For more information on reach and stack, or help in understanding the new sizing standard please visit:
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makes a heck of a lot of sense!!
Great idea!
Looks like Banshee is on board too:
http://bansheebikes.blogspot.com/
Great idea!
good idea, for a while now, MTB Rider magazine in the UK has been publishing downtube measurements, which if you remember your basic trigonometry are basically the same thing.
having said that splitting out reach and stack is more accurate, top marks
Glad to hear they’re making a big rider-conscious step towards fit-sizing.
I am sure once people realize how much sense this standard makes, Tony Ellsworth will claim responsibility.
Sam, and Dave: Great idea to work towards this as a standard.
[...] PinkBike - Sick Lines - DeclineMag [...]
er..as long as they still make a ‘Medium’ im game.
I hope this excellent idea is going to be the breakthrough of a new measuring method. The next step then has to bring an equivilent solution with height and reach for saddle position.
Cheers
Stefan
I’d make a correction. On picture provided in this arcitcle there are 2 main points reach/stack are calculated from:
1) center of head tube’s top edge
2) center of BB
I’d suggest a slightly different system:
1) center of head tube’s bottom edge (and you should take into account that different frame manufacturers use different types of headsets so measurements for integrated and conventional will be a bit different, I measure from head set’s bottom edge)
2) center of BB
This way it will be easier to compare reach/stack when frames have different head tube lengths. Anyway, you can always add more spacers if you need them.
I use this “corrected” method since last year. Very effective.
[...] Som goda grävande journalister har vi mätt cykelns geometri i stället för att bara kopiera från tillverkarens webbsajt. Vinklarna och måtten i tabellen nedan är uppmätta med de enhetsdäck vi valde att montera för grupptestet i Spanien, Maxxis Minion DHF 2.5?. Vårt testexemplar var storlek L/XL och passade testryttarna som varierade mellan ca 180 till 190 cm. Den enda andra storleken S/M blir väldigt kort med ett uppgivet effektivt överrör på 549 mm. För den som vill läsa mer om de relativt nypåkomna måtten reach och stack finns sådan information här (länk). [...]
[...] Vinklarna och måtten i tabellen nedan är uppmätta med Maxxis Minion DHF 2.5″ och med Magic linken i normalläge. Vårt testexemplar var storlek 18″ och passade testryttarna runt 180 - 185 cm. För den som vill läsa mer om de relativt nypåkomna måtten reach och stack finns sådan information här (länk). [...]
[...] Vi har i vanlig ordning mätt cykelns geometri i stället för att kopiera från tillverkarens webbsajt. Vinklarna och måtten i tabellen nedan är uppmätta med de enhetsdäck vi valde att montera för grupptestet i Spanien, Maxxis Minion DHF 2.5?. Ur tabellen nedan går det att utläsa att vårt testexemplar i storlek M har ett för storleken kort överrör och kort hjulbas. För den som vill läsa mer om de relativt nypåkomna måtten reach och stack finns sådan information här (länk). [...]
[...] Siffernörden med gott minne märker att siffrorna i tabellen stämmer precis med vad Canyon publicerar så när som på två saker: styrvinkeln uppger Canyon till 68,5 grader, avvikelsen på 0,2 grader ligger inom felmarginalen för vårt mätverktyg. Vikten är enligt Canyon 12,85 kg utan pedaler och vårt exemplar väger 13,16 kg, en skillnad som inte förklaras av kedjestagsskyddet vi monterat. Ur tabellen kan konstateras att vevlagerhöjden är ganska låg. Det ger en låg tyngdpunkt för cyklisten vilket är gynnsamt på många sätt men minskar markfrigången och ökar risken att slå i pedalerna. Hammerschmidt eliminerar det första problemet men man får passa pedalerna i stenig terräng. Canyons system för storleksrekommendation PPS (länk) rekommenderar medium för mig och jag instämmer. Som oftast är jag dock på gränsen mellan medium och large och antagligen hade en large med kortare styrstam funkat även det. Det kan vara intressant att veta att på ramstorlek medium är maximal sitthöjd 76 cm med originalstolpen. För de intresserade finns mer information om måtten reach och stack (länk). [...]
Great idea. Wonder if it will actually take off?
After all we are still using the Penny Farthing system for measuring our gearing - gear inches.