Have you ever tried this with other ramps? 
Some are flat out dangerous.  And some have surfaces that may as well be like climbing a frozen glacier.

Come to RAGAN EQUIPMENT to see and buy ramps that you can use safely.   The design and materials used
will provide you peace of mind as you drive your 400+ pound lawn tractor up into your pickup truck bed.

Sometimes it is the litle things that count.  Let us show you.  Price?  Very reasonable.  Especially for you and your loved ones safety.