I saw off a piece of old handle bar about an inch or so long, then saw that in half to make two "C" shaped sections to shim with - also, if the bolts don't seem to be tightening without stretching, I replace them with 10.9 grade bolts and if the bolt heads are hard to get a wrench on due to the curve of the bracket, I put an extra lock washer under the head of the bolt to get a better grip on it with the wrench.