Metzeler Roadtec Z8 - which ones?

[pulsar2]

Today I went out for a ride in a very moderately hilly road section and found myself lacking confidence leaning the bike into turns. I felt very less traction on the rear and kept running wide on each turn, even when it was just at 25-30Mph. This might be a newbie mistake as well, but the tires are probably stock ones and it is a 05 model(Dunlop tires). So, I want to get new Metzelers Z8, but which ones?

I found the following ones from Revzilla.com :

Front : Tire Size: 120/70ZR17 E 58W
Rear : 180/55ZR17 O-Spec 73W

These two cost more than the other options in the same size, so I have the confusion. Which ones to buy? And, what does the O-Spec and the E stand for in these two option?

 

[FrozenBiker]

This is what the mfg has to say about that:

The best wet performance in the Sport Touring segment
The wet weather handling of motorcycle tyres and especially the braking performance in wet conditions, is becoming an increasingly important feature demanded by the rider. This rider requirement occurs especially if it suddenly rains and a high level of security is needed. Metzeler has decided to develop the new (M) and (O) specifications to provide motorcyclists the latest technology in terms of wet grip by retaining a high level of performance in all other areas. The rear tyre of the specifications (M) and (O) has a bi-compound mixture. The rubber compound in the central section of the tread area, depending on the tyre size, is on average 45 mm wide, with a 70% silica content specifically designed for higher mileage and stability at high speeds. The tyre shoulders comprise of approximately 88 mm on each side of the profile and have a 100% silica compound, which increases dramatically the chemical grip in the wet and reduces sliding under all conditions. The front tyre also consists of a 100% silica compound.

Source: http://www.metzeler.com/site/com/products/tyres-catalogue/Roadtec-Z8-Interact.html