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Gravel Gear

Sleek and subtle, full-suspension gravel: The new BMC URS LT

Front suspension reduces vibration energy by a claimed 46 percent, averaged across the spectrum of frequencies encountered in gravel riding.

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With 20mm of hydraulic-damped front suspension and 10mm of elastomer rear suspension, the new BMC URS LT isn’t perhaps as ‘long travel’ as its moniker implies. But very much unlike the few gravel bikes with suspension forks — or the Niner full-suspension gravel bike with a shock in the main triangle — the URS LT tidily integrates the surface-smoothing technology into its clean lines.

“LT means more capable in BMC parlance,” said BMC marketing manager David Heine. “Travel is relative.”

Indeed, compared to standard, rigid gravel bikes, any amount of travel is longer travel. Compared to the current crop of gravel forks, 20mm is still on the shorter side.

RockShox’ new Rudy XPLR gravel fork has 30mm and 40mm options. MRP has 40mm of travel in its new gravel fork, as does Fox in its current 32 AX (a newer model is in the works).

The URS LT design, at a claimed 1,250g, weighs about as much as those forks.

BMC collaborated with HiRide on the 20mm suspension that is tucked inside the head tube of the URS LT. (Photo: Jérémie Reuiller)

High frequency, HiRide

The URS LT front suspension was the culmination of a four-year collaboration with HiRide, an Italian suspension group that has worked with Pinarello in the past.

Both HiRide and BMC spent time studying the particulars of vibration on various parts of the bike encountered when riding gravel.

“We studied vibration, acceleration, efficiency — being the relationship of power versus speed — and the interaction of tires and suspension,” said BMC head of R&D Stefan Christ.

With accelerometers mounted to various points of the bike, BMC test riders rode a test track to quantify different types of inputs.

BMC found that for rough-road to light-gravel riding, the peak frequency was about 30Hz. For the rough terrain that the URS was built for, riders encountered an average peak of 25Hz.

The suspension has a simple lockout on top of the aluminum steerer tube. (Photo: Jérémie-Reuiller)

BMC also tested other suspension products, and took qualitative feedback from test riders.

“Our goals were to be able to absorb high frequencies, and be tunable,” Christ said.

The end result was a cartridge inside an aluminum 1.25in steerer tube, which is bolted with a steel base to the carbon fork. “We wanted carbon fork legs because the material absorbs high frequency so well,” Christ said.

The suspension is a coil spring with a hydraulic damper and a blowoff valve.

“We have a damper because we want to absorb energy, not just have a spring,” Christ said.

By measuring vibration at the bottom of the fork on the head tube, BMC could track how much energy the suspension was absorbing. When the delta between the two points was averaged across the full range of frequencies, the HiRide suspension reduced vibration energy by 46 percent, Christ said.

The hydraulic-damped system is designed for 5mm of sag, which can be tuned with one of three little top caps. Similarly, the suspension is set for rider weight by using one of three spring weights. (Photo: Jérémie-Reuiller)

Similar to Specialized’s Diverge FutureShock system, there are multiple springs to customize stiffness. In BMC’s case, there are three springs for different rider weights.

The system is designed for 5mm of sag, which can be slightly tuned with three different preload caps.

There is a lockout cap on the top of the steerer tube, and the headset compressor threads directly into the steerer, which can be cut down by as much as 4cm to fit a rider’s preferred stack.

The 800g aluminum and steel upper is bolted to the carbon lower. (Photo: Jérémie-Reuiller)

The pros and cons of elastomers

The URS LT retains the 10mm of rear elastomer suspension used on the original URS.

BMC first used this design — which it dubbed Micro Travel Technology (MTT) — in 2015 on cross-country bikes. Ralph Naf raced the design at the 2014 worlds, after XC racers asked for something to take the sting out of the high-frequency bumps on when they were standing up on downhills.

The 10mm elastomer MTT carries over from the original URS. (Photo: Jérémie-Reuiller)

“This elastomer is made for automotive, with a huge weather range and a 10-year outdoor rating,” Christ said. “It naturally has controlled rebound; it’s a spring and a damper at the same time. It can absorb energy. But at the front of the bike, this material was not an option because we needed a bigger tuning range, and 20mm was too big for a compressible material.”

Offroad geometry, and model prices

As with the original URS, the URS LT uses an ultra-slack 70-degree head angle — “we know that this is basically an off-road bike, so it deserved off-road geometry,” Heine said.

Only Evil’s Chamois Hagar is slacker – at a whopping 66.7 degrees. Most gravel bikes are in the 71- to 72-degree range.

It also comes in four sizes, with a long top tube and a short stem (sizes S to XL get 70-90mm stems).

Rubber protectors at the down tube (which is semi-common) and the fork ends (which is not) also continue from the original URS.

Maximum tire clearance is 45mm.

This fork though has cable routing for a hub dynamo, should you want to add on.

There are two carbon models, the $7,999 URS LT One that comes with SRAM Force XPLR eTap AXS and the $6,299 URS LT Two that comes with SRAM Rival XPLR eTap AXS. BMC carbon house wheels comes on both.

Stay tuned for a full review in the coming days on the URS LT One.

The BMC URS LT One with SRAM Force XPLR eTap AXS. (Photo: Jérémie-Reuiller)