Besides the accordian effect, it's also never a good idea to leave too big of a gap between you and the ones in front of you. Gap as in a space big enough for a car to slip in. I've done many charity rides and it Does happen. They usually don't stay there long, intimidation, police, etc, they usually find out real quick they screwed up.the accordin effect is horrid on big rides. be very careful about other riders.