While performing tests, dynos don't interfere with the engines performance and more importantly, don't do any damage to it.

Some of the things that may cause damage to engines are over-revving, excessive heating, shock loading or incorrect fuel or ignition settings.

If however your engine malfunctions after performing a dynamometer test, it's almost certain that the testing, if properly done, wasn't the cause of the damage.

It is more likely to damage your engine when you drive your car on the road than when you test it by the means of a dynamometer under controlled artificial conditions. You should always make sure that the dyno operator is a trained professional and that the dynamometer has an appropriate cooling system.

A 60 centimeter diameter fan is appropriate for a power run. It will prevent the vehicle from overheating.

However, you should keep in mind that dynamometer testing and setting up race cars and bikes require more controlled testing conditions. A bike or car that heats up after a few hours testing suffers from heat soak into the transmission, bodywork, engine block, oil, and so on. This interferes with the amount of power produced, and influences the accuracy and the objectivity of the performance test.

To make sure everything will go smoothly while performing your tests on engines, you actually need a wind tunnel in which you should manipulate your dynamometer. When you are driving on the road at full power there is a lot of fresh air that surrounds and cools the entire vehicle, and you should do your best to recreate some of these natural conditions when you perform your tests.

If your dynamometer or the place you go to in order to get your car or bike dyno tested does not have suitable working conditions or lacks an appropriate cooling system, it is not advised to perform any tests.

The problem concerning the damage done by dynamometers on the tires is more debatable. Tire manufacturers recommend dynamometer owners to replace tires after every test performed. They claim that the tires design is not intended for purposes like dynamometer testing and say that the heat or tire deformation could damage the interior structure. Due to these facts, they strongly recommend replacing the tires after testing.

However, this should be done more as a precaution, and if the tires are rather new, well designed dynamometers should not damage them. Just to make sure that everything is in order, remember to always check the tires condition after every test you perform.