Riding within your limits is easy advice to take when your reading a forum. It's harder to follow that same advice when in the middle of the adrenaline/excitement of a brisk group ride. If you feel like you might be taking chances...YOU ARE. Slow down. All it takes is 1 blown curve to ruin your day. Smoothness leads to speed, not the other way around. The fast guys don't look smooth by accident. They know what they are doing. Don't attempt to match their pace if you don't know the proper technique. Ask them for tips before the ride, at gas stops, etc and practice. 7 or 8 years ago CORE went through something similar. There were suddenly a lot of new people showing up to groups rides. Rides went from 3-5 people of similar skill levels that were used to riding together...to 6-8 (or more) people with different levels of experience that didn't know each others riding habits. Despite pre-ride talks...there were a bunch of crashes mostly by new people that got caught up in the moment and got in over their heads. A few learned from their mistakes, most never came back. It was frustrating. Ride Leaders: It's very hard for a ride leader to tell if someone is riding beyond their limits. You can only see so much form those tiny, buzzy, mirrors. I think the leader is responsible for setting a predictable pace, pointing out debris, and counting bikes at stops and that's it. The leader can't control the right wrist or ego of those riding behind. An experienced sweep is VERY important when the group is not familiar with each other. The sweep needs to speak up when it looks like a crash is coming. I've asked more than a few riders to calm down during a group ride...some listen, some don't. I've also left plenty of rides because the group dynamics weren't right.