(By Alissa de Vogel)

Last night the San Francisco Bike Messenger Association hosted goldsprints to kick off this weekend's Quake City Rumble race series. Gestalt Haus was generous enough to let their space be taken over by dozens of bike messengers, piles of roll-top backpacks, and unstable heaps of bikes outside.

Goldsprints is a type of bike race where competitors go head-to-head on stationary bike trainers in front of an audience. The bikes are hooked up to a computer that measures the riders' speed and projects their progress up on a screen for the crowd. Since the bikes are balanced in a fork stand, the riders only need focus on pedaling as fast as humanly possible for a short period of time. Last night, participants raced to 4 miles; since most riders averaged 48-55 miles per hour, the races are short and sweet lasting only around 20 seconds. A fantastic time was had by all, despite some technical difficulties that kept one of the bikes from registering speed properly.

Here's a rundown of other Quake City Rumble races, rides, and parties happening this weekend. All races are open to all types of bike and riders of all abilities:

Friday 6/29

• Registration: If you plan on competing in any races this weekend, come on down and register at Pushbike (22nd & Shotwell) tonight from 6-9 pm. The $25 fee gets you registered for all applicable races, beer, barbeque and a QCR t-shirt. Afterparty with drink specials at Benders on 19th & South Van Ness. (Some individual races may have an additional registration fee)

Saturday 6/30

• Ladies/Trans QCR Race: Begins at 12:00 pm at Potrero del Sol (25th & San Bruno)

• Dumptruck Race: Begins at 3:00 pm at Potrero del Sol

• Sardines Time Trial: Begins at 5:30 pm at Potrero del Sol

Sunday 7/1

• Mountain Lion Race: Begins at 12:00 pm at Potrero del Sol

• Barbecue: All day at Marx Meadows, sponsored by Norcal Courier, Zoom, Godspeed, Cricket, Espresso, Center City Delivery, Spirit Courier, Cupid, and Docket Rocket.

More info: www.sfbma.org or Facebook.com/quakecityrumble