The sound of your pipes

Loud pipes save lives! I believe this strongly, and have written a couple of times on the subject, and I went as far as sewing a patch with these words on my cut. Like zillion other bikers I guess.

But loud pipes can also kill all fun we have, and I do not mean extremly loud pipes that give you a headache after some hours. No, the fun is killed by eager law enforcement officers, who – for whatever reason motivates them-, do what they are allowed to do, enforce a law some politicians drew up on their desk to please their electors in hope of reelection.

With european harmonisation, a concerted effort by Brussels to remove all elements of fun and risk from our lives, the laws harmonise to the smallest denominator, that is never a compromise, but goes right down to the strictest values of limits. And to remain “important” politicians, they periodically review these limits, and adjust them to even stricter values. Its a vicious circle.

Enough ranting, lets look at some facts…

There is no legal noise limit for motorcycles (plural), there are individual noise limits for each bike, which are different from bike to bike, from car to car, and they are written in the individual registartion documents. They are even glued as a stickler on to the frame of our Harleys for everybody (and the police) to see.

Check this out: my 2011 Sportser 883R can be as loud as 96dB(A) at 2,985rpm, while, my 2010 Road King Classic may only produce 86 dB(A). Knowing that a increase of 10dB is a doubling of volume, it remains a mistery to me why Harley registered my Road King with 86dB, while the Sportser can pass with 96. More worrying, the bikes of Chapter friends on other 96ci V2s show usually 93-94 dB, not my meager 86.

The 2011 Sportster 883R:


The 2010 Road King Classic:

I would appreciate if Harley-Davidson does us all a favour and homologises our bikes to the highest value possible, as this will make it much easier in our individual “negotiations” with law enforcement around. And it just does not make any sense that some 96ci engines are limited to 86 dB(A), while other can go up to 93-94 dB(A).

But the hard fact remains: if you create a noise louder then these levels printed on your bike or your papers, your bike does not comply with its registration document and has to be removed from the road.

There are 2 factors that can influence your future on the road:  a) can the actual noise your pipes make be accurately measured, and b): is the cop in front of you a nice cop.

Unfortunately, most often these 2 questions must be answered with NO. Noise measurement is more complex then speed measurement, and is therefore not exactly accurate. Some police in my home countries therefor take the average of 3 measurements, half a meter behind the bike at a 45 degree angle, and give you a allowance of 5dB(A). Then comes the nice cop bonus, though nice cops are rare cops. Remember, they stopped you for no good reason, just because they didn’t like your freedom. So you will most likely be considered too loud, your bike is not road legal anymore and has to be modified. Its all about the money…

Now be careful: if you disagree with the measurement, the friendly policeman will most likely agree with you, and remove your pipes as evidence for scientific testing in a laboratory with lots of white coat scientists. Remember, you just committed mass murder, bombed parliament and stole half the gold reserves of his country. Now you have no bike and no pipes and it all starts to be really expensive. My advise is trying to be a very nice biker to a hopefully nice cop, and agree on some compromise. Maybe you were in a group and others are louder, and he is happy with a couple of scalps for his belt only. In any case, try to keep your calm and agree of getting your bike towed to the next dealership for correction of the problem, best with its pipes still attached so they can be modified.

Be creative, but never run. Remember, you are most likely in a foreign country…


One Response to “The sound of your pipes”

  1. Dre van Holland Says:

    To start with : all bikes have to comply with the same sound level (can be different though for very small bikes) as part of the homologation test.

    The value that you find on individual bikes or models are so-called reference values (different sound in dB and different engine speed in rpm).
    These are used to link a (simple, stationary, one engine speed, no engine load, measured closer to the exhaust) road side measurement with the official homologation test (more comprehensive, driving-by, changing engine speeds and loads, gear changes, with running chain etc. ! measurement farther from and at changing distance to the moving bike……).

    The road side measurement is subjected to some rules to be valid (like not standing next to a big building’s wall), but still the tolerance is (has to be) pretty big, like maybe 5 dB, to compensate for the less controllable test conditions of such a road side measurement.

    So, if one model produces 80 dB in the oficial homologation test, it can produce 86 in the road side measurement, whereas another model can produce 92 dB (still without the say 5 dB tolerance). The reason is that the different models are just different, like small high revving 4-cylinders and big low revving V-twins (all with original exhaust ! ).
    Therefore, the reference value that you (and the police) find on the different bike models are different. And typically higher than the (same for all) homologation value, just because you are closer to the exhaust, like at only half a meter.

    The fact then, that some bikes (with original exhaust) seem (!) to produce more sound (sometimes noise….) when driving on the road, has to do with the fact that the homologation test may be performed under different conditons than of actual road driving.
    That in turn can be different for the different models (are they racing or touring bikes ?).

    So that’s why the exhaust flap is closed in the official test, and so again the reference value may be lot higher than the silent homologation value.

    With aftermarket exhaust, the reference value will stll be used by the police………. so with removed flap (I won’t mention models….), you may be “silent” in the police test (flap would be opened anyway, so the reference value is high), but not anymore if you would perform the official homologation test !

    I have notice one thing, which is that even the offcially released bikes of The Company have become louder in the recent years. Not a lot of course, but very noticeable. The mid-1990’s exhausts had become really silent (and sensitive to corrosion!), but already at the (latest) turn of the century the exhaust (rumble) had become louder (sound design knowledge had grown), whereas sound level rules had become more stringent (and come to a stop since then !).

    This also had to do with the improved trade-of between exhaust note (that we like) and mechanical noise (that we do not need…), which are measured combined, but heared differently by “us”.

    Of course the aftermarket or after sales exhausts produce far more or maybe better sound in case you might need it………..

    By the way, did you know that during the sound development, the bike stays in one position, and the measurement microphones are moving…. instead of the bike in the homologation test ?

    You can develop inside, and not bother with wet road conditions that would influence the measurement, or make it invalid….. this saves development time etc.

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