How much difference does driving w/o a washer make, if any?

[Eatmyclutch]

While doing a brake swap my bonehead decided to lose a washer(too lazy to take off the other side, probably the most time consuming part of the swap). Here the pics:
http://i32.tinypic.com/35ldop3.jpg
http://i32.tinypic.com/2i0degk.jpg
http://i26.tinypic.com/211otp3.jpg
If anyone know the size, it'd help much.

[My5ABaby]

I always just take the bolt to a local hardware store/Wal-Mart/Lowe's/Autozone/whatever and find a washer that fits. :dunno:

[orion84gsl]

Just measure the diameter of the bolt and take it to your local hardware store. Or take the one on the other side to a hardware store and get the same one.

[Kentetsu]

Should be a lock washer. Find one to prevent it from working itself loose going down the road...