Both items show what's called motorpaced racing.
Basically the bicycle riders draft behind the motorcycles.
Both the bicycles and motorcycles are made specially for that particular sort of race.
Before motorcycles there were paced races where the riders were behind other bikes with usually two or three riders. From the 1890's till around 1910 paced races were very popular. Speeds around 40 mph, and rather dangerous. Many of the riders moved on to auto or motorcycle racing, or flying airplanes at air shows. Especially after a horrible accident in Germany where the pacing motorcycle crashed into the crowd at speed and caught fire. Airshows despite the apparent risk were actually safer and more profitable since the plane didn't need to actually fly to earn appearance fees.
Motorpacing remained popular through the 30's, usually as part of a six day race, and is still hanging on although there hasn't been a world championship for a few years and it's not usually part of a typical large track race.
Depending on where the bikes are run, some pretty insane speeds can be reached. At a very large track or an auto race track 60+ isn't unusual. And the current world record is 166.944 MPH.
http://www.youtube.com/watch?v=A5wmkXu_v2k
"Normal" motorpacing here.......
http://www.youtube.com/watch?v=JLTf1_SN8MQ
I own two motorpacing bikes, One from the 1980's the other from probably the 1920's. Here's the older one.
The small front wheel helps get the rider closer to the motorcycle, and the backwards front fork both shortens the bike and makes it less likely to crash if you get too close and hit the motorcycle. The motorcycles have a roller on the back as well.
The older bike I have was crashed at one point, and converted to being a normal bike. It took a bit of hunting to find the parts.
The picture is really a nice one. I think I've seen it before. Many of the pictures were used for several years for postcards and photos. A really big one is unusual. I may have a copy of that one on my computer somewhere, If I can find it. I might also have the riders names along with it.
Steve B