If you've built a beetle bot and you are having issues with it I will teach you how to fix it in this instructable. There could be many things wrong with it, including: the SPDT switches aren't working, one motor is faster then the other, or it's too top heavy. What ever the reason I'll do my best to show you how to fix them. If you have any questions that I didn't answer, write them in the comments and I'll do my best to answer them as soon as possible! : )
Step 1: SPDT Switches
If your SPDT switches aren't sensing it when it hits something don't worry about having to take them off then re-glue them because there is a simpler way!
1) look at your heat shrink, and make sure the actual motor shaft isn't touching the ground ( if it is, thats a big problem)
2) shrink your heat shrink over the end of the motor shaft ( just like jerome said, if you don't have tires you can't drive )
3) Also check your batteries, they could be almost dead so the SPDT switches won't hit as hard, therefore the motors won't turn.
Step 2: Motors
A problem you could have encountered is the motors are going at different speeds. They may not even be going at different speeds at all, it could be that the third connection is not connected very well causing your motors to not reverse, or it could be if the motors are at different heights to the ground. To fix that you don't have to re-glue the motors unless you didn't have any of the problems below.
1) first look at your heat shrink and make sure it even on both motors
2) Check your back wheel and make sure the paperclip is bent sideways, make it straight
3) Check your batteries because if there is 1 battery for each motor while going forward, and one is dead they are definitely going to travel at different speeds, although when in reverse they should be fine
4) if you didn't have any of those problems you are probably going to have to re-glue your motors so that they are at equal height to the ground.
Step 3: Top Heavy?
You might have noticed that your beetle bot could be top heavy. Jerome gave you some ways to fix it, but I think the easiest way is to just bend the paper clip with the wheel up, but not enough so that the battery holder touches the ground. That will cause it to tilt up a little so it won't fall over because it is top heavy. If you didn't want to do that then then you could attach a heavy weight or magnet near the end of the battery holder, the only problem is that it could slow down your beetle bot.
Step 4: Ready to GO!
Your beetle bot should now be ready to go explore! The SPDT switches are working, the motors are going the the same speed, and it doesn't fall over from top heaviness!!! Again if you have any question write them in the comments.