How to Address Common Evasions
Evasions usually stem initially from irritation or discomfort but they can very quickly become an ingrained habit (which is accentuated when the horse is tense) - the horse then learns lots of useful little tricks i.e. using the tongue to push down on the bit, popping it over the top, out to the side or crossing the jaw and grabbing the bit etc. For instance it is no longer common practice to start the babies off in a breaking bit (bit with keys) as this can encourage tongue evasions.
I receive many phone calls from people who are quite despondent as they cannot understand why their horse always goes brilliantly, but only for a short space of time, when they change into a new bit. If your horse has a sensitive mouth then this is quite understandable and you have simply got a pressure buildup which means that you need to be alternating between two or three different mouthpieces that use different pressure points. You will soon find at what point you need to change mouthpieces.
We don't all start with a clean slate. Some horses have not had their teeth done regularly, they may have been fitted with bits that did not accommodate their mouth conformation or they may have simply been neglected or abused. I have acquired many horses over the years with various evasions for numerous reasons. Many horses have bit issues caused by discomfort, for instance, some horses may cross the jaw to avoid an uncomfortable contact, they may open the mouth or use the tongue to lean and push down on the bit. In some instances, they will physically grab the bit between the teeth in order to reduce the pressure. If a horse is uncomfortable and a noseband is employed to shut the mouth, it will simply compound the situation as the pressure and subsequent discomfort will be accentuated.
Nobody knows your horse better than you and if for example, you apply a flash and your horse's way of going deteriorates this is because you have merely increased the pressure and caused further discomfort within the mouth. What you actually need to do is look carefully at your bit and what pressure points it is using. I have seen many instances where a flash has been employed in conjunction with a fat mouthpiece in order to stop the horse from opening his mouth. This has resulted in the horse not being able to swallow properly and often causes a horse to toss the head in order to do this. When I have removed the flash and used a thinner bit such as the 16mm Training Lozenge not only has the horses attitude and way of going improved but they have been relaxed and happy in the mouth so much so a flash is no longer necessary.
If you know that your horse's bit is comfortable but you do still need to shut the mouth (old habits die hard), then it may be worth trying a drop or grackle noseband - not all horses like the drop as it does sit lower down on the nose but it does not increase the pressure in the mouth to the same extent as a flash. A grackle is also preferable to a flash as it does not increase the pressure around the lips and mouthpiece to the same extent. It is legal for horse trials but not for dressage. This is another illogical dressage rule.