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Two Brothers M-2 Carbon Fiber Exhaust Review

Two Brothers Carbon Fiber Exhaust Review
A Rugged/Sweet Sound Just Shy of Obnoxious
wBW Quick Look by Rick K. for webBikeWorld.com
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Also: BMW F800S Blog

Part 2: Two Brothers P1 Power Tip Review
Part 3: Two Brothers P1X Power Tip Review

Background

I'll confess: like many other motorcyclists, I like the sound of a hearty exhaust note.

But also like many others, I don't want to overdo it.

I was warned that the Two Brothers M-2 carbon fiber can would be too loud but it's actually not, at least on this bike.

For example, it doesn't seem as loud as the FMF muffler on the Suzuki DR650 (Blog) I owned...although I guess that's not saying much.

So here's a quick look at the easy installation and a sound recording and video of the results.

The stock BMW muffler weighs 6.2 kg (13.6 lbs.) and at around 4,000 RPM it pushes the sound meter to 76.6 dB at idle and 86.6 dB at a distance of 6 feet.

The Two Bros carbon fiber exhaust weighs just 1276 grams (2 lbs., 13 oz., albeit without the adapter) and runs 88.7 dB at idle and 98.6 dB at 4,000 RPM.

That's a massive 4.9 kg difference; around 10 lbs., counting the pipe adapter.

Two Brothers also sells a P1 and P1-X "Power Tip" insert, said to reduce dB by 3-4 or 7-8, respectively. I ordered a P1 to see if it makes a difference and I'll report back on that also.

wBW Video: Two Brothers M-2 Exhaust Sound Comparison

Part 2: Two Brothers P1 Power Tip Review  |  Part 3: Two Brothers P1X Review

Installation

I had never installed an accessory exhaust on any motorcycle before, so I wasn't sure how involved it would be. But on the F800S, it couldn't be easier. The instructions that come with the Two Brothers kit are pretty good, with color photos.

On the F800S, it's a simple matter of removing the single bolt and disconnecting the clamp that holds the stock muffler to the exhaust pipe under the bike, just in front of the rear wheel. The stock muffler has an attached length of pipe to bridge the gap, but the M-2 exhaust has a separate connector pipe so that you can swap out the muffler when or if necessary.

Remove another bolt from the hangar in back of the passenger foot peg and the BMW muffler can be removed. Be careful though, it's heavy!

Installing the Two Brothers M-2 is more or less a reverse of the procedure. The only instruction I didn't follow was the guidance on mounting the Two Brothers V.A.L.E. (Variable Axis Locking Exhaust) adapter. This consists of two half-moon shaped pieces of aluminum that connect the exhaust can with the short adapter pipe.

According to the instructions, the V.A.L.E. pieces are supposed to be loosely mounted on the end of the M-2 exhaust first, then the adapter is supposed to fit over a flange on the short exhaust pipe adapter.

I could not get everything lined up by doing it this way, so I mounted the V.A.L.E. pieces after getting everything else loosely attached and aligned. I loosely fitted the short adapter pipe to the BMW exhaust manifold pipe using the clamp, then hung the M-2 using the supplied clamp that fits the BMW exhaust hangar bolt, then finally added the V.A.L.E. sections.

Get it all aligned as close as possible -- be sure to look at the M-2 exhaust can from the rear of the bike to make sure it's oriented correctly and then tighten all the bolts.

Here are some quick pics and an .mp3 sound file:

Two Brothers Exhaust
The F800S with stock exhaust and the Two Brothers M-2 kit on the floor.
Two Brothers Exhaust Parts
Here's the M-2 kit: Exhaust can, adapter pipe, hangar, the 2 V.A.L.E. pieces (black), bolts and high-temp gasket sealer.
Two Brothers Exhaust Ends
The M-2 canister ends. The carbon fiber version was the only Two Brothers exhaust I could find for the F800S; apparently the exhaust for this motorcycle is no longer being produced, although there may be one that fits. But the M-2 in aluminum, titanium and carbon fiber is still available for many different motorcycle makes and models.
Two Brothers Exhaust Inside
Here's a look inside the exhaust -- a straight shot, for sure!
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BMW F800S Exhaust Junction
The junction on the F800S where the manifold pipe meets the exhaust pipe.
Two Brothers V.A.L.E. Connector
The Two Brothers V.A.L.E. Connector fits the exhaust pipe to the can.
Two Brothers Exhaust Hanger
This is the hanger that comes with the Two Brothers exhaust to fit the BMW.
Two Brothers Exhaust Tip Close-up
Looks pretty racy, no?
Two Brothers Carbon Fiber Exhaust Weight
Here's the M-2 carbon fiber can on a postal scale in antiquated pounds (left) and grams (R).
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BMW Stock Exhaust Weight
The BMW stock exhaust felt like a ton of dead weight in comparison, here shown at 13.6 lbs.
Two Brothers Exhaust Installation
Job completed, time to ride!
BMW F800 S With Stock Exhaust
The F800S with the stock exhaust.
BMW F800S With Two Brothers Carbon Fiber Exhaust
Looks racy, yes! Sounds good too. Here's an .mp3 file with an on-the-road recording (.zip format, monaural).
Conclusion

The Two Brothers M-2 carbon fiber exhaust looks good and sounds good. It appears that the only type of M-2 canister still available for the early F800-series is the 005-2530407V carbon fiber version I installed, which lists for $549.95. I found this one at "Fly-n-Cycle" on eBay for $395.96. They're getting hard to find for the early F-series and I'm not sure if the fitment is the same for the new F800GT and F800R.

Power differences? Who knows. The dyno chart that came with the exhaust shows very little difference over stock and I say there's no one who can really tell if the Two Brothers exhaust makes a difference. It's all about the sound...

Part 2: Two Brothers P1 Power Tip Review  |  Part 3: Two Brothers P1X Power Tip Review
More: BMW F800S Blog

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wBW Review: Two Brothers M2 Carbon Fiber Exhaust
Manufacturer: Two Brothers Racing
List Price (2015): Varies
Types: Sport, V-Twin, Off-Road.
Made In: U.S.A.
Sizes: Fits various motorcycles.
Review Date: January 2015
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Your Comments and Feedback

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From "M.S." (January 2015): "I just read an article about mufflers and saw that you used a real dB meter. I was wondering if you have a dB meter on your iPhone and if you ever compared the two. Thank you for all you do."

Rick's Reply: Actually, I'm an Android guy. I downloaded the Smart Tools Sound Meter v1.6 app from the Google Play store, it has a calibration feature. If I calibrate it to run close to the Extech meter, it's fairly accurate but only with a steady (non-varying) sound.

If the sound is variable, like revving the bike, the app meter seems quite different than the Extech. So apparently with a steady sound, you can get them to read close but probably the tiny mic port on a cell phone limits the amount of variation. If it's calibrated, the app sound meter should come close to correct for holding and recording max sound levels though.


From "S.M." (January 2015): "As someone who has a F800GS, this review is of very close interest to me. I am thinking of getting one of the two brothers exhausts, mainly for the cost benefit and the weight savings.

The stock exhaust looks like a bazooka, and mine probably needs repacking after 3 years and 30k miles. I get 86db at idle, and 94 at 4k rpms on the stocker, using a free app on the phone. It's not Harley loud, but something I don't want to rock.

You don't sound like someone from the loud pipes clan, and I feel your take is probably the most objective when it comes to Two Bros.

I've seen YouTube videos that say that the power tip does bring in the claimed db drop. You have a more professional gig to measure the sound output, I am looking forward to see how much the P1 improves - both in the measured drop and more importantly in the perceived drop. If I go Two Bros, my choice is the P1x tip, I very much like having a quiet exhaust."

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