I installed SRAM Rival on a bike last weekend.

I now have about 100 miles on it, quite like it, except for the rattle.

Left hand brake lever/ shifter has a rattle. If I take my hand off the brifter - it rattles, put my hand back on, or wrap a finger around the lever, no rattle.

Anyone else had this? If so, what is the fix???

One Possibility: Did you replace the front brake cable and housing when installing the shifter? Does the cable make any sharp bends? It sounds like the front brake may not be putting enough tension on the cable due to a fouled cable or light spring tension in the brake. A lack of tension may allow a bit of slop in the shifter resulting in a rattle.

Another area to explore is the plastic plate that puts tension on the brake housing where it exits the hood. If the two little screws that attach it are loose, it may cause a rattle? :confused:
Good luck!

So, you installed your parts on your bike? Did you put the cables in the brake levers? If one lever rattles and the other lever doesn't, then there must be a difference between the way the brake cables are installed. Did you check to see if the cable head is properly seated, and that you have the cable head on the correct side of the cable yoke inside the brake lever blade? My guess is, if you look at the two brake cable heads inside the two brake levers, you see one is sticking out further then the other. and the lever that is "loose" is the one that has the cable head improperly installed, and sticks out furher from the yoke.
SRAM shifters do not rattle, the design of the system prevents that.

Thanx for the replies folks - Brake cables are properly installed.

I have installed enough of 'em over the years to be sure I've put them the right way in in the cable yolk.

Baffles me.