Two Brothers S1R Exhaust System Honda GROM 2014-2015
  • Two Brothers S1R Exhaust System Honda GROM 2014-2015 - Carbon Fiber
  • Two Brothers S1R Exhaust System Honda GROM 2014-2015
  • Two Brothers S1R Exhaust System Honda GROM 2014-2015
  • Two Brothers S1R Exhaust System Honda GROM 2014-2015

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This product is legal in California only for racing vehicles which may never be used, registered or licensed for use upon a highway.

Two Brothers S1R Exhaust System Honda GROM MSX125

The Two Brothers S1R Slip-On Exhaust represents a step into the future for TBR. The S1R exhaust features a carbon fiber sleeve highlighted by a natural aluminum outlet and stamped, spring-mounted inlet for the ultimate durability. Like most TBR mufflers, the end cap of the S1R exhaust is constructed of magnesium and features a non-stick teflon coating. However, that is where the similarities end.

The aggressive design of the end cap is reminiscent of the modern jet engine making this exhaust move at mach 1 speeds while standing still. The carbon fiber sleeve of the S1R exhaust system is made of a 33 million modulus rated carbon fiber that is impregnated with high temperature resin, under very tight tolerances. Thirty-three million modulus rated carbon fiber can be considered the Goldilocks of carbon fiber , it has strong structural properties without being overly stiff and brittle, making it just right.

The sound produced by the S1R is deep and throaty thanks to its spiral-wound perforated core technology. The rubber-lined, natural finished aluminum muffler clamps feature an aggressive angular design and cutouts to reduce weight. The mid-pipe is constructed from .035” thick 304 stainless steel. After a few heat cycles the 304 steel turns a golden amber color, the hallmark of quality stainless. Of course an exhaust can't be all show and no go, that is why the S1R exhaust is track-tested and dyno-tuned to offer the best performance package.


  • Fully-serviceable in the event of damage, routine maintenance or the occasional repack
  • Aerospace high-temp carbon fiber
  • Stamped spring-fit inlet
  • Optional P1 and PX1 sound inserts available (sold separately)
  • Optional anodized bolts kits available (sold separately)
  • Made in USA
Unit Stock Exhaust Two Brothers Max Gain
Max Power HP 8.65 9.5 + 8.5%
Max Torque ft-lb 7.64 8.04 + 8.5%
Weight lb 11.15 5.65 - 5.5


4.9 / 5
Bang For The Buck
5 / 5
5 / 5
5 / 5
Ease Of Install
4 / 5
Fit & Finish
5 / 5
5 / 5
This Product Fits:
Grom MSX125 2014, 2015
Product Style RevZilla Item # Manufacturer Product # Availability
Carbon Fiber / Full System 935688 005-3740105-S1 In Stock: Ships within 24 hours


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5.0 / 5.0
2 Reviews
5 Stars
4 Stars
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1 Star
Bang For The Buck
5.0 / 5
Bang For The Buck
5 / 5
A great upgrade for the Honda Grom!
Overall I really like the stock look of the Honda Grom and never planned on making too many mods.

When I saw the Two Brothers S1R Exhaust System, I thought it enhanced the look of the bike without radically changing any lines / characteristics. The choice of materials used and the simplified mounting really gives the bike a more premium feel. The carbon fiber looks sick in real life.

My only concern was I did not want something obnoxiously loud. There are videos posted online of the sound you can expect from this exhaust, but it is hard to judge the volume.

Luckily, it is just right. The exhaust is louder but not extreme. It has a really gnarly growl to it. I feel like the noise definitely matches the Honda Groms attitude.

The Grom definitely feels like a new animal with this exhaust installed. I feel like the chart is accurate with its performance claims.

What the chart can not summarize is how the new exhaust sound will also make you feel like you're going faster. Its truly awesome.

I without a doubt recommend this product. I feel it brings the Honda Grom to the next level in all aspects an exhaust system can ( sight, sound, performance).
February 25, 2014
2014 Honda Grom MSX125
Bang For The Buck
5 / 5
Two Brothers Exhaust Honda Grom
Excellent Product. 15 minute install and that is including getting the tools out and putting them away. Significantly lighter then the OEM exhaust. The sound is fantastic and after a couple wide open freeway runs the bike easily broke into the 60mph range, routinely touching 65+ mph. Really opened the bike up and the sound is amazing!
March 10, 2014
2014 Honda Grom MSX125
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