Full suspension gravel, elegant and subtle: the new BMC URS LT


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With 20mm of hydraulically damped front suspension and 10mm of elastomeric rear suspension, the new BMC URS LT might not be as ‘long haul’ as its nickname suggests. But very 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 carefully incorporates surface-smoothing technology into its clean lines.

“LT stands for more capable in BMC parlance,” said David Heine, BMC marketing director. “The journey is relative.

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

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

The URS LT design, weighing 1250g, weighs about as much as these forks.

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

High frequency, HiRide

The URS LT front suspension is 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 have spent time studying the peculiarities of vibration on various parts of the bike encountered when riding over gravel.

“We looked at vibration, acceleration, efficiency – being the relationship between power and speed – and the interaction of tires and suspension,” said Stefan Christ, head of R&D at BMC.

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

BMC found that for riding on rough roads or light gravel, the peak frequency was around 30Hz. For the rough terrain for which the URS was designed, riders encountered an average peak of 25Hz.

The suspension has a single lock on top of the aluminum head tube. (Photo: Jérémie-Reuiller)

BMC has also tested other suspension products and gathered qualitative feedback from test pilots.

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

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

The suspension is a coil spring with a hydraulic shock absorber and a relief valve.

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

By measuring the vibrations at the bottom of the fork on the head tube, BMC was able to track the amount of energy absorbed by the suspension. When the delta between the two points was averaged over the entire frequency range, the HiRide suspension reduced vibration energy by 46%, Christ said.

The hydraulic damping system is designed for sag of 5mm, which can be adjusted with one of the three small top caps. Likewise, the suspension is adjusted for the rider’s weight using one of three spring-loaded weights. (Photo: Jérémie-Reuiller)

Similar to Specialized’s Diverge FutureShock system, there are several springs to customize the stiffness. In the case of BMC, there are three springs for different weights of riders.

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

There is a locking cap on top of the head tube and the headset compressor screws directly into the steerer, which can be cut up to 4cm to fit a rider’s favorite stack.

The 800g aluminum and steel rod bolts to the carbon rod. (Photo: Jérémie-Reuiller)

Advantages and disadvantages of elastomers

The URS LT retains the 10mm elastomer rear 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 World Championships, after XC riders asked for something to relieve high-frequency bumps when standing on the descents.

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

“This elastomer is designed for automotive use, with a wide range of weather conditions and an exterior rating of 10 years,” said Christ. “He naturally has a controlled rebound; it is a spring and a shock absorber at the same time. It can absorb energy. But on the front of the bike this material was not an option as we needed a bigger range of adjustment, and 20mm was too big for compressible material.

Off-road geometry and model prices

As with the original URS, the URS LT uses an ultra-relaxed 70 degree head angle – “we know this is basically a mountain bike, so it deserved an all-round geometry. field, ”Heine said.

Only Evil’s Chamois Hagar is softer – 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 shank (sizes S to XL have 70 to 90mm shanks).

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

The maximum tire clearance is 45mm.

This fork does have cable routing for a hub dynamo, however, should you wish to add some.

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 the SRAM Rival XPLR eTap AXS. BMC Carbon House Wheels are available 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)

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