Decibel testing

NewYorkLuke

NewYorkLuke

Active Member
I thought I read in the past there has been decibel testing on exhausts prior to the start of the IBR. I did not see that being done at the 2025 IBR. Did I not see it or it is not a concern anymore. I only ask before I put an aftermarket exhaust on my bike
 
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Luke,

What I perceived was, if the odometer checker team could not talk over the sound of the bike, then you were going to have an issue.

-Mark
 
Issues regarding noise levels were handled prior to the start of this year's IBR, as were several other items that in the past were done the weekend before the start. You may have also noticed there was no fuel capacity testing because all that was done weeks or months earlier. The result was that instead of taking two days for the pre-start processing, it took one.

Ira
 
I had a good conversation with a member about this Saturday ( they were in this years IBR ) . One of the IBA staff asked why would anyone want to change their exhaust system.

Answer ;)
So I can change the rear tire / remove rear wheel on my BMW R series without having to remove the Hot / heavy stock can . The R / RT series one can not pull the wheel without pulling the end exhaust can. GS is up higher ,and not a issue.
Deleting a known failure point on BMW's the Flapper valve.

Also weight. Adding weight to a Rally bike one can gain back 20 to 30 pounds by exhaust change.
 
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Everything to do with the bike and all of our paperwork was done months in advance, all we basically had to do was check in, do an odometer check and attend a few meetings, the whole thing was simple and efficient.
 
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NewYorkLuke said:
I thought I read in the past there has been decibel testing on exhausts prior to the start of the IBR. I did not see that being done at the 2025 IBR. Did I not see it or it is not a concern anymore. I only ask before I put an aftermarket exhaust on my bike
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What bike, what exhaust?

@Ira - What is the current standard for exhaust noise for the IBR?
 
EricV said:
What bike, what exhaust?

@Ira - What is the current standard for exhaust noise for the IBR?
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There's an entire appendix devoted to the subject in the IBR Rules. Here's the first paragraph:

Consistent with the rally's interest sponsoring events that will not generate opposition from law
enforcement agencies or the general public, participation in the Iron Butt Rally will be limited to
motorcycles capable of meeting the requirements of the Society of Automotive Engineers (SAE)
Recommended Practice J2825 (Nov 2012). The requirements of J2825 limit the sound level of motorcycles
equipped with 3- or 4-cylinder engines to 100 dBA at a measurement distance of 0.5 meters (20 inches)
from the exhaust outlet with the engine running in neutral gear at 5,000 rpm. Motorcycles with less than 3
cylinders or more than 4 cylinders are limited to 96 dBA at a measurement distance of 0.5 meters with the
engine running in neutral gear at 2000 rpm. The position of the sound meter during testing is shown in Figure
1. Except for riders with motorcycles granted a written exemption, motorcycles that exceed the limits of
SAE J2825 will not be allowed to be used in the rally.

The current iBR rules is at


See Appendix B, Muffler Policy

Ira
 
Had to test the BMW R1250RS 20250813_154026.jpgwith Remus can / Black Widow header.
88 DB @ 2000 rpms
 
Yes the rules state about testing aftermarket exhausts but the aftermarket exhaust in question is manufactured to be legal for street use the whole world over. No "For off road use only" nor "May not be legal in some states" disclaimer anywhere. In other words it was a whole lot of hullabaloo about nothing. Now, after spending a whole lot of money, time and effort, would you risk being disqualified before you ever even started?
 
I would caution that street legal doesn’t mean it meets IBR rules or SAE recommended practices. Bottom line, if you want it to meet the IBR rules, test it to make sure it does. (As Russ did)
 
What I find interesting is the method of testing . In NFPA 72 when testing Audibility in commercial building for Fire Alarm the required height is 5' to hold the test meter. My meter is a certified testing meter for life saftey.

Who puts their ear at 20" away 45 degree angle ? Serious just picking up the meter to 5' and stepping back 2 feet the DB drops to the low 80's
I understand the IBA staff dont want a Open Kerker Meg or sawed off open headers ;)

1755175632288.png
 
EricV said:
It’s just a standard so testing results are repeatable and comparable. It doesn’t matter why. You can’t change the why, only the results.
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I understand that very well. Its more a comment of how Real World Life Safety Testing requirements has it in a realistic manner over a no-realistic form of testing . Since this topic is up its shed a little light on the subject.
 
In some circles, it may be a bit tacky to post a link to another forum, however...

AMA SAE J2825 EXHAUST Measurements Test

AMA SAE J2825 EXHAUST Measurements Test
www.cvoharley.com

Additional background info on the spec (without having to actually pay for the entire spec) seems to be here: https://www.cyclepedia.com/sae-j2825-standard/

If the AMA was involved in the development of the specification, then the test is what it is. In fact, see the post where a YouTube video is provided showing LE doing a in-the-field test of a motorcycle.

EDIT: This really seems to be a 'back east' issue. Honestly, I just don't recall checks like these happening in the 40-odd years I have been involved with motorcycles here in the west, unless it was a concerted effort by LE to enforce this at an event - think motorcycle rally.
 
In the 1964 case of Jacobellis v. Ohio, U.S. Supreme Court Justice Potter Stewart explained his definition of "obscenity" as, in part...

"I shall not today attempt to further define the kinds of material [...] and perhaps I could never succeed in intelligibly doing so. But I know it when I see it [...]"

Exhausts are the same thing in my opinion. We can argue all day about whether you should use this standard or that standard, whether it should be straight on or at a 45 degree angle, or whether it should be at 20 inches or 20 feet.

But in the end, if you have a loud motorcycle... you know it. No need to pretend like you dont.

Loud motorcycles are obnoxious, and I don't blame anyone who wants to enforce a rule to keep them acceptably quiet so as not to tarnish the image or reputation of the event.
 
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igneouss said:
You can conduct a reasonable test using a cell phone with a decibel app. Not conclusively accurate but good enough to know if you might need more accurate testing.
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If your asked by a Fire marshal about using a phone for a DBA test the answer is no sir . Phones are inaccurate . Being dropped , pocket lint in port and so many other variables they are not allowed in any type of certified testing.

Just a fyi I'm not concerned with my BMW's level . It passes
 
c10 said:
If your asked by a Fire marshal about using a phone for a DBA test the answer is no sir . Phones are inaccurate . Being dropped , pocket lint in port and so many other variables they are not allowed in any type of certified testing.

Just a fyi I'm not concerned with my BMW's level . It passes
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Screenshot_20250815_065723_Firefox.jpg
 
Shawn K said:
Loud motorcycles are obnoxious, and I don't blame anyone who wants to enforce a rule to keep them acceptably quiet so as not to tarnish the image or reputation of the event.
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What about all the children of the riders who's lives might have been saved by loud pipes??? Won't SOMEBODY think of the CHILDREN???
 
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