The only 'safe' way to tell how low you can go is to put the bike on a stand, remove the bolts on the top of both fork legs and then press the bars down.A good way to check how much u can lower is to look at the dust marks on the forks in between the triple trees. This is how much play you have in lowering as your suspension hasn't been used in that area where the dust is. This will differ with each bike with various riders and riding styles. And if you lower the bike using less than the length of the dust area you shouldn't bottom out. Hope that made sense. :zombie:
The springs will then have someplace to go when you push the front end down and you will be able to bottom the forks. If nothing hits at that point, you're safe.
If you rely on the dust on the fork legs, all it will take is one big pothole to compress the forks more than they had before and WHAM, you've gone metal to metal.
Russ