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Reach and Stack

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.

Reach and Stack chart

Reach and Stack mtb geo

“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.