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TRP G-Spec Trail SL Disc Brake

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Tested: TRP 4-Piston G-Spec Trail SL Disc Brakes

TRP, a legitimate contender in the disc brake game, delivers a solid product for trail riders with continued influence from Aaron Gwin.

Rating: Vital Review
Tested: TRP 4-Piston G-Spec Trail SL Disc Brakes

Aaron Gwin's impact on TRP has been tremendous, and the latest brake from the growing brand benefits from the technologies developed with one of the world's best downhill racers. Together they made the burly Quadiem brake, scrutinizing every detail along the way, and much of it bears a close resemblance to the new Trail SL brake you see before you. You'll find the same G-Spec lever blade and finned caliper body on both brakes, although the Trail SL gets mismatched piston sizes and its own lever body. How does that downhill pedigree transfer over to the everyday trail ride? After over five months of testing to ensure they're in it for the long haul, we're here to fill you in on the details.




  • Excellent in a variety of trail conditions
  • Linear and intuitive braking response
  • Firm but gently yielding lever feel
  • Impeccable consistency when bled well
  • Easy to use lever adjustment with positive detents
  • Adjustable banjo for a clean look
  • Excellent pad durability (metallic)
  • Can use competitor pads in a pinch
  • Pads don't rattle
  • Competitively priced brake system, replacement parts, and bleed kit
  • Easy to get a great bleed
  • Mineral oil brake fluid has a long shelf life, is non-corrosive, and is easily cleaned
  • All black!
  • Forces SRAM shifters into less-than-ideal position due to lever clamp interference and poor Matchmaker integration
  • Levers can't be flipped for "moto" style riders
  • Unable to independently adjust bite point and lever reach
  • Lengthy bedding process
  • The hose is on the exposed side of the caliper
  • Metallic pads work well but can be quite noisy
  • More noticeable loss of power than the competition when pads glaze
  • A little on the heavy side

TRP G-Spec Trail SL Highlights

  • Forged caliper with CNC cooling fins
  • Two 16mm and two 14mm ceramic/alloy hybrid pistons per brake
  • Tool-free and indexed reach adjust
  • Aaron Gwin designed aluminum lever blade
  • Mineral oil brake fluid
  • Compatible with Shimano I-Spec II, Tektro HD 3.6 adapter for SRAM Matchmaker
  • Weight: 312g (front brake, no rotor)
  • MSRP: $149.99 per brake
  • Rotors available in 140, 160, 180, and 203mm sizes (not included, $49.99-$59.99 per rotor)

Installation & Initial Impressions

All of TRP's rear brakes come prebuilt with a stopper in the hose, allowing you to tackle the task of internal routing with minimal fuss. Once that is done you simply trim the hose, attach it to the lever with the correct fitting, perform a quick Shimano-style lever bleed, tighten up those rotors bolts, and ensure the discs are clean before bedding in the pads. The front brake comes pre-bled with the lever attached.

For this test, we paired the Trail SL brakes with 180/203mm two-piece TRP-33 rotors on our 29-inch Transition Smuggler. The slots in the rotor remove water, mud, and debris from the braking surface while the two-piece design promotes heat management and stiffness.

With wet, muddy, wintry rides forecasted for the foreseeable future, we swapped the stock semi-metallic pads for TRP's full metallic variety right off the bat. As TRP notes, their copper-backed metallic pads are best for riders wanting maximum braking performance, more bite/power, the longest pad life, or when riding in wet conditions. Due to the hardness of the steel material used for the rotors, the bedding process takes a notably longer time than most brakes. Be ready to get your heart rate up as the brakes require anywhere from 30-50 go-fast-then-slow-down cycles to fully bed in with metallic pads.


Grabbing hold of the Trail SL brakes you're met with a solid feel around. The lever itself feels very sturdy since it doesn't spring outward and there's no play in the pivot. The hook shape is perfect for one-finger braking, cradling your finger nicely and ensuring you won't slip off when pulling hard. You can adjust the lever reach using the easy-to-turn knob with detents that you can feel and hear. Unfortunately, there's no way to adjust the bite point independent of lever reach, but amazingly both the starting position and bite point landed within just a millimeter or two of our preferred setup.

On The Trail

TRP's brakes have a very gradual power delivery that will feel different to what many riders are used to. This is because SRAM, Shimano, etc, offer brakes that provide a lot of power pretty quickly – often as a result of a cam in the lever assembly. TRP brakes, on the other hand, do not have a cam in the lever and are very linear in nature. As you pull the lever to the bite point there's less of the initially grabby braking hit that many are accustomed to, but as you squeeze harder more and more power is applied at a rate that will quickly become like second nature.

The harder you roll TRP's new G-Spec Trail SL brakes on, the harder they deliver. Thanks to a very linear and instinctive feel, the brakes offer a massive range of braking power that shines regardless of conditions.

In addition to the way the lever works, another factor that plays into the light initial feel and overall modulation is that TRP uses two 14mm and two 16mm pistons in the caliper. The 14mm pistons allow that portion of the pad to contact first before the pad area backed by the 16mm pistons follows. This light onset will have habitual brake users riding faster, and those who have mastered looking far ahead will love the ability to scrub just a little bit of speed when needed. The light initial power application is also quite beneficial in muddy and loose-over-hard conditions. The fact that the brakes aren't super grabby allows you to slow down in situations that may otherwise prove to be tricky – like over slippery rocks or roots – without your tires breaking loose.

"If you are wondering what the difference is between our downhill brakes and the new G-Spec Trail line just think downhill power tuned specifically for the wide range of speeds experienced while trail riding." - TRP

While they come on gently, there is always enough power on tap to get stopped in a hurry. Just squeeze harder. From a pacifier pull to hard and fast stops, the Trail SL brakes offer an incredibly wide range of power modulation in a short 3/8-inch lever throw past the bite point. When the lever really hits they have that perfectly bled, firm feel, and thanks to a bit of lever body flex they yield gently once you're really into it.

Only on very long, steep, sustained descents with lots of hard, consistent braking have we noted a bit of finger soreness due to the somewhat boxy lever edge and linear power delivery. Then again, these are "trail" brakes. We never experienced fade or spongy levers on these same brake-burning rides and things stayed remarkably consistent. The brakes feature ceramic/alloy hybrid pistons that help isolate brake fluid from the heat that's generated by friction, keeping them more consistent in the long run.

Long Term Durability

The brakes are still going strong after nearly six months of use in everything from wintry slop to dry desert terrain. Both rotors show very little wear, the black finish looks excellent, all of the pistons move freely, and there is no slop in the levers. We've also been very impressed with the life we've gotten out of TRP's metallic pads.

Curious to see how long the bleed would last, only late in the test period did we feel some slight inconsistency during repeated pulls of the rear brake lever. The front remains perfectly sharp and consistent to this day. As outlined in this TRP how-to, the full bleed process involves pushing mineral oil from the bottom up:

A basic bleed kit will run you $18 and contains enough fluid to last a while. For a quicker fix, a Shimano-style lever bleed is very easy to do while you repeatedly squeeze the lever. As shown at the end of the video, strapping the lever to the bar overnight will result in an incredibly solid brake feel.


Things That Could Be Improved

With power, modulation, consistency, and durability on lock, there isn't much that truly needs to be improved. Yes, there are some minor but livable details outlined in the Weaknesses section above. Our chief complaint is poor compatibility with SRAM shifters. With the brakes in their most natural position, interference issues exist when paired with a standard SRAM bar clamp. If you like to ride with your palms at the ends of your handlebars, you'll likely need large hands or a willingness to move your hand to fully reach the shifter. Due to the orientation and size of the TRP lever bolt and clamp the shifter ends up a bit more inboard than we feel is ideal.



TRP does state the brakes are compatible with SRAM Matchmaker using the included Tektro HD3.5 or HD3.6 adapter, but these adapters put the shifter in an odd forward position that is also tough to reach. The HD3.6 is the newer and better of the two. When asked if any efforts were being made to remedy this, TRP informed us that the Matchmaker adapter is on their list for a redesign in the future. Meanwhile, Shimano's I-Spec II shifters line up much better (or you can just hold out for that new TRP drivetrain).


What's The Bottom Line?

The harder you roll TRP's new G-Spec Trail SL brakes on, the harder they deliver. Thanks to a very linear and instinctive feel, the brakes offer a massive range of braking power that shines regardless of conditions. The control they allow is truly excellent when it's slick out and traction is hard to come by, and they're also up for the speeds you'll hit when hero dirt will let you do no wrong. Add in reasonably easy maintenance, consistent performance, plus the lever's sleek appearance and TRP has made a winner for trail riders.

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About The Reviewer

Brandon Turman - Age: 32 // Years Riding: 17 // Height: 5'10" (1.78m) // Weight: 170-pounds (77.1kg)

"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.


Product TRP G-Spec Trail SL Disc Brake
Riding Type Cross Country, Trail
Lever Material Aluminum
Mount Style Compatible with Shimano I-Spec II, Tektro HD 3.5 Adapter for SRAM Matchmaker
Rotor Sizes 140mm, 160mm, 180mm and 203mm
Rotor Mounting 6-bolt
Fluid Type Mineral
Colors Black
Weight 0 lb 11 oz (312 g)
Miscellaneous Weight for front brake, no rotor

Four piston forged caliper

2x16mm + 2x14mm hybrid pistons

Tool-free indexed reach adjust

CNC caliper with cooling fins

Aaron Gwin designed lever blade

Price per brake, no rotor
Price $149.99
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