I don't have a link but I recall that someone did a study that revealed that there was no safety improvement from loud exhaust and the only way to improve motorcycle safety was increasing visibility with high-visibility vests.
In my state there are no helmet laws so I always find it amusing that the "loud pipes save lives" crew are the same who wear no helmets or any other protective gear.
In my state there are no helmet laws so I always find it amusing that the "loud pipes save lives" crew are the same who wear no helmets or any other protective gear.