90 Degrees tyre Valves?

Not sure why did KTM only put a 90 degrees stem valve on the front tyre..

As I check and fill O2 about once a week I'd like to get one on the back as well to make it easier. Any reason not to?

Moreover, I'm always loosing some psi's on the front, about 2-4 every 1-2 weeks. Not sure why is that, but maybe I should put a new valve stem on it as well, just to tick this check box as well.

Are you guys familiar with the Ariete type? Any other?
TBH, really don't want to spend much on it. Found this, but I'm not sure if it's the same as what supposed to be the original:

Original looking:
http://stores.sportbiketrackgear.com/De ... k?no=10302

Less original looking and half the price:
http://www.ebay.com/itm/MOTORBIKE-MOTOR ... 337764eb43

And this guy:
http://www.r1-forum.com/forums/showthre ... ost5024106


And just to be sure, our's is a 8.3 mm, right?

I assume they only put one on the front because the valve is more fiddly to get at with brake discs on both sides. The back is easier to access but there's no reason why you couldn't put an angled valve on it.

Replace both stems to 90 degree and life will be less stressful when filling yr tyres.
I would choose the Ariets, very nice.

You fill your tyres with O2??