In one of my Sanglas bikes, I noticed -one year after i bought it- that the front wheel was reversed. Being a twin disc, somebody put it in reverse and the arrow was facing backwards. I reversed it but, to be honest, I could not tell the difference in handling.
Recently I have laced a wheel to replace the front wheel of my Suzuki GZ250. I wanted a stubby front tire and installed a 130/90-15 -just like the rear wheel-. The tyre said "for rear wheel only".... until I dropped unintentionally an angle grinder with a sandpaper disc on it :-)
The bike handles perfectly, I would say even better than with the original 110/90-16 tire. Somebody told me that these things happens when front and rear wheel are the same - the geometry is not altered when the bike leans.
I'm pretty sure there is a lot of technology and design in the tyre carcass manufacturing, but from outside, they are just a round piece of rubber, and if a thread pattern is good to evacuate water when installed in the rear, it shouldn't be less effective when installed on the front. Only the ply layout should make a difference in order to withstand acceleration -rear- and braking -front-, and that's the reason why some wheels have the arrows pointing away from each other depending on whether they are for front or rear use. If you are not riding like hell all the time, I think you could be good enough mixing front and rear tyres.
