Speed Balanced Geometry: Transition's Approach To Creating Better Mountain Bikes 27

Bellingham's best bike partiers question everything, put it to the test, and come up with a better handling ride following what may be Transition's nerdiest endeavor yet.

Transition Bikes isn't a brand that crams marketing jargon down your throats. If anything, their outlandish videos laugh in the face of corporate tactics. The company is made up of great riders who simply want to make the best bikes they can, and they're determined to have as much fun as possible while doing it. "Party in the Woods" is their mantra, and every ride with the crew is a reminder of why we all love bikes so much.

It's clear that they are resistant to standards that aren't proven, so if it's a feature on their bikes it's something they've thoroughly tested and truly believe in. That's why when Lars Sternberg and Sam Burkhardt invited Vital to come see what their "R&D Program" had been up to, we knew it'd be good.

Lars 'N Bars hard at work testing a prototype 29er using Speed Balanced Geometry.

Within minutes of arriving at their headquarters in Bellingham, Washington, we were off on a ride with half the company to sample some of the incredible Pacific Northwest trails that play a major role in shaping their bikes.

Two and half years ago they embarked on a journey that would ultimately lead them to their latest creation – Speed Balanced Geometry, or SBG for short.

Questioning The Status Quo – Experiments In Fork Offset

"In the search for a better handling bike, we started by asking some simple questions. Why are mountain bikes becoming longer and slacker? The obvious answer is stability. Why is this good? It makes the rider feel safer and creates a more stable chassis at higher speeds or on steeper terrain. Longer and slacker comes at a cost, however, and that cost is realized at slower speeds or flatter terrain where the front wheel is too far ahead of the rider. This inhibits the rider's ability to properly weight the front wheel. What if it were possible to have a mountain bike that did all of this well?"

Longer and slacker comes at a cost, however, and that cost is realized at slower speeds or flatter terrain where the front wheel is too far ahead of the rider. This inhibits the rider's ability to properly weight the front wheel.

One can dream, and dream they did. Inspired by some experiments by Chris Porter, a man known for wild concepts and pushing the boundaries of geometry, Lars and Sam began an extensive test cycle with over 15 different variations of fork offset and frame geometries.

Custom one-off CNC crowns were provided to Transition for testing purposes. They feature a shorter offset than normal.

"Why, you ask? In the last five years, your mountain bike has changed in in many ways. Your wheels have likely gotten bigger. Your frame has gotten longer. Your head tube has gotten slacker. Your suspension has improved. Your stem has gotten shorter and your bars have gotten wider. And you likely have a remote dropper seat post opposed to a straight post. Your components have improved in ways that have allowed you to ride easier, farther and harder. Yet, the there are some things that haven't been updated with the rest of these improvements. One of these things is steering trail."

'Trail' is defined as the horizontal distance from where the front wheel's contact patch "trails" the point where the steering axis intersects the ground. It's a function of head angle, fork offset, and wheel size. All vehicles need trail to ensure that the steerable wheel is stable. The farther the wheel's contact patch is behind the steering axis, the more stable the bike and slower the steering; the closer, the less stable and quicker the steering.

'Offset' is the distance from the steering axis to the front axle. Part of this measurement is a result of offset at the crown-steerer unit and part is in the fork dropouts. Shortening the offset of a fork lengthens trail, and vise versa.

Current trail figures fall between a regular set of parameters depending on wheel size and bike suspension travel. The thing is, this range of trail is based on an old legacy of 26-inch bikes with outdated geometry...

"Trail is one of the dimensions that relates to particular steering feel and handling characteristics. Current trail figures fall between a regular set of parameters depending on wheel size and bike suspension travel. The thing is, this range of trail is based on an old legacy of 26-inch bikes with outdated geometry; steep head tube angles, shorter reach and top tube, longer stems and skinnier handlebars. Why shouldn't this evolve with the rest of your bike?"

The Result – Speed Balanced Geometry

Listen in as Lars explains the basics of SBG and how Transition arrived there.

Five Key Components Of SBG

The SBG concept incorporates the following five key changes from their current models:

Increased frame reach – "The SBG system utilizes frame reach measurements that are longer than Transition's current models."

Slacker headtube angle – "This allows the fork to absorb impacts better on all angles and positions the front wheel further forward in relation to the handlebars. As you approach obstacles in the trail a steeper head tube angle has a more vertical suspension path. This reduces the fork's ability to properly absorb impacts and generates deflection. A slacker headtube angle positions the fork at a better angle of approach to absorb impacts which reduces deflection. Additionally, slacker headtube angles reduce dive while increasing rear wheel grip under heavy braking."

Steeper seat tube angle – "Steeper seat tube angles aid in climbing traction and reduce seated sag when climbing. These two changes bring the rider more forward in the chassis into a more central location between the front and rear tire contact patches, which greatly increases traction."

Shorter stem – "The system is designed to be used with a 40mm stem, which equates to a modest increase in total reach when compared to Transition's current models which use 50mm stems." "We do think there's a little magic by keeping stem length very close to what your fork offset is."

Shorter fork offset – "SBG is designed to be used with a fork offset that is shorter than traditionally used per wheel size. The shorter fork offset brings the front axle more rearward and under the rider which further increases front tire traction. This works in unison with the shorter stem length to provide a more direct steering input and dramatically enhances connectivity to what is happening with the front wheel. The shorter offset also brings the front wheel more under the rider which balances the effects of a slacker head angle. The SBG system creates a longer trail figure than standard, used in a way that eliminates the negative side effects."

Transition stresses their holistic approach to steering geometry, which is a complex balance of the bike’s head angle, rider weight bias, overall wheelbase, front center, fork offset, and trail. Changing one number will affect all the others.

"We don't really feel like forever longer is better... You need to find a balance between stability and agility. If you took just an old bike and went up a size it would be more stable, but you sacrifice somewhere else."

What we went for was trying to improve the balance of the rider in the bike. Basically being able to lengthen the bike a little bit to gain all of the good stability attributes, and then bring the rider a bit more forward in the bike.

"What we went for was trying to improve the balance of the rider in the bike. Basically being able to lengthen the bike a little bit to gain all of the good stability attributes, and then bring the rider a bit more forward in the bike. Not just longer and slacker which just puts you continuously further back behind the front wheel. Bring the rider's mass a bit more forward, more centrally located over the front and rear wheels which will improve front wheel traction. All of that stuff goes back to creating more confidence for the rider."

Introducing The Sentinel

Transition will roll out the brand new Sentinel in Fall 2017. It's a long travel 29er built around the SBG principles.

Key geometry numbers for a size medium Sentinel, including the shorter than normal 42/44mm offset. Many 29ers run a 51mm offset.

Do The Claims Hold True? Proof Through Back-To-Back Testing

To put Transition's claims to the test, we not only met up with them on their home trails in Bellingham for a two day pedal fest on many of the area's best trails, but also took a prototype 2018 Patrol home for some back-to-back testing. This is where things really came to light.

The setup: Two bikes. One with SBG and one without. Both the same model. Before setting out we ensured that both bikes were as close to identical as possible. We used the same handlebar brand, rise, sweep, roll, bar height, sag values, pedals, and tire pressures. The bikes also used the same wheels, brakes, dropper post and lever, drivetrain, etc. As many variables as possible were eliminated.

We then headed to the lifts, completing eleven runs while swapping bikes between each lap. Trails included a mixture of some very steep pitches, technical bits, tight high-speed singletrack, wide open fire roads, as well as flow trail terrain with jumps and a variety of berm types. After lap four the various benefits of SBG became much more apparent, and each time we'd go back to the "old" bike we'd note another subtle shortcoming. 

Seated, the bikes are almost identical when it comes to bar position. On gently winding singletrack the two bikes also often felt very similar.


There were three main areas where SBG really shined for us:

Calmer Cornering

We were consistently able to corner in more control and with more speed. From slight chattery turns on the fire road to long sweeping berms, every corner on the new bike feels as though you're making a smoother, more perfect arc that requires less attention. On the traditional design, cornering often felt like being in a car and not looking far enough ahead, making multiple small steering corrections along the way. With SBG we no longer felt like we had to micromanage the front end as it required fewer rider inputs. Turning the bike felt calmer in every sense. Just enter wide, lean in, and the magic happens. The bike feels as though it leans in earlier and easier, and carving through bermed turns is an absolute treat on the new ride.

The fact that Transition has gained the manufacturing support of FOX and RockShox, the two major mountain bike suspension players, says a lot.

"I started playing around with less offset on my 29er about three years ago. Our cross country race teams have been racing on less than 51mm offset on their 29ers for quite some time and it got me wondering how it would feel on a 150mm travel 29-inch FOX 36 fork. On the specific bike I was riding at the time I was looking to shorten the bottom bracket to front axle and this was an opportunity to try it out. It got my balance on the bike more centered and I learned in the process it allowed me to corner more with my core and hips and less with the arms. I also started noticing more equal pressure and traction on the tires when cornering. Coincidently, some of the other internal test riders at FOX started their own experimenting, and chatting over a beer after a lunch ride one evening we all had the same ride feeling and conclusions. But we did find there was a magic formula (we didn’t know what that formula was and still don’t claim to), and we couldn’t just bolt it on any bike and prefer its characteristics. Head angle, chainstay length, reach, etc, all had either positive or negative effects depending on the bike.

It turns out Lars and the Transition crew had been brainstorming about the effects of less offset and requested some test samples. After receiving the prototypes and conducting some initial testing we got together and discussed it further. They put the work into finding that overall bike geometry that met a ride characteristic they were after. You really can’t bolt it onto any bike and have an improvement. In fact it could make it handle worse. As riders, our body naturally tries to find the balance point between the tires for the best traction, and moving the front or rear axle relative to our center will have an effect of shifting our weight bias. Some of our internal test riders actually didn’t prefer less offset when we installed the forks on their bike. A couple of years ago we conducted the experiment with Tracy Moseley, who is one of our best test riders, her first comments were, "Wow, it made my bike feel smaller and I think I need to go up a frame size." So that was a lesson that the rest of the bike might need some changes to go along with it. I personally run [a shorter] 44mm offset on all my 29er test bikes at the moment." - Mark Fitzsimmons, FOX Race Program Director

"There is obviously a lot more going on with Transition's new geometry than just the offset. The different offset is only a component of their new design philosophy. But it was important nonetheless. In general the numbers will tell you that less offset gives you more trail. In my experience, it gives greater overall stability on the bike while at the same time creating great front wheel traction. In general, when using shorter offset forks and longer reach frames I have felt that the area I have to work in as far as body movements is a little larger for a given size bike, but also without sacrificing any responsiveness when I need it in tight terrain situations." - Ariel Lindsley, FOX Product Development

R&D at its finest. How SBG was born.

What's The Bottom Line?

If you dig into the science behind bicycle steering geometry you're likely to only get more confused. Fact is, the precise factors impacting this grey area are still largely unknown. Perhaps it's fitting then for Transition to have discovered an excellent combination of frame geometry and components through extensive R&D out on the trail. Was that research and development? Or riding and drinking? Sometimes they're one in the same... In this case the end product is fan-freaking-tastic. In our opinion, Speed Balanced Geometry works better than what is currently on the market. It's an honest and innovative attempt to further mountain bike capability by focusing on little details that truly matter.

As Transition put it, "What does this ultimately mean for you? More control, more confidence, more party."

Visit www.transitionbikes.com for more details.

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About The Tester

Brandon Turman - Age: 31 // Years Riding MTB: 17 // Height: 5'10" (1.78m) // Weight: 175-pounds (79.4kg)

"I like to have fun, pop off the bonus lines on the sides of the trail, get aggressive when I feel in tune with a bike, and really mash on the pedals and open it up when pointed downhill." Formerly a Mechanical Engineer and Pro downhill racer, Brandon brings a unique perspective to the testing game as Vital MTB's resident product guy. He has on-trail familiarity with nearly every new innovation in our sport from the past several years and a really good feel for what’s what.

Action photos by Skye Schillhammer


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