 Anyone can put sportbike tires on a sportbike......but only a real Two Wheel Freak would put sportbike tires on a sport-touring bike! Well a slightly misinformed editor might do the same thing but still.........
I am referring to Pirelli's brand new sportbike tire the Diablo Rosso. Before they even hit the market, before even much information was known about them, 2WF was offered a set to review. I was told at that point (by a third party and not directly by Pirelli) that they should work fine for the FJR and would be better than whatever I currently had on the bike. Strong words considering I was about 2k miles into a new set of Avon Storms and couldn't praise them enough.
So off came the Storms and on went the Rossos and everything was bright sunshine, little birds singing, flowers in a meadow, and butterflies cavorting in the air, right? Well.....not exactly.
See, right after I put the tires on, more info was released by Pirelli which clearly showed that the Rosso was NOT a sport touring tire but a tire meant for a sportbike. Hmm....what to do, what to do. Should I do the sensible thing and take them back off and put them on a sportier bike? -OR- Should I do the real Two Wheel Freak thing and leave them on and see how well they actually perform when they are completely out of their element? This kind of thinking is like the all-star football or basketball player playing baseball; almost never works out too well. So it doesn't usually work for athletes, but would it work for tires?
Tire construction today is so high-tech that in most cases tires are designed specifically for a certain weight bike (or weight range), certain riding styles, etc.. Gone are the days of picking your next tire based upon looks or what's cool. Every manufacturer produces a certain tire for a certain purpose and/or bike type. In Pirelli's case they actually break it down even further by what percentage of time the bike will be used on the track vs. street. Pirelli lists the Rosso as a tire for a sportbike that sees mostly road use and occasional track days (around 25% or less of track usage).
What I wanted to know was how much of the "this tire fits this and that tire fits that" talk was based upon actual design limitations and how much was just marketing mumbo-jumbo.
Well I got my answer pretty quickly and can say that, at least in this instance, tire fitment talk is based on design and not marketing. That being said I was still pretty impressed by how the sportbike tires reacted on a sport-touring bike.
First (and really only) negative thing I noticed was the squirm. Any time the bike was leaned over at any speed the tires would wiggle. Slow u-turns; wiggle. Medium speed sharp corners; wiggle, wiggle. Medium speed sweepers; wiggle, wiggle, wiggle. High speed sweepers; wiggle, wiggle, wiggle, wiggle....well ......you get the idea. The tires never broke traction or did anything untoward, I could just feel the sidewalls flexing under the load. OK so obviously when a tire manufacturer says that the tire is made for a certain weight range they aren't kidding. What impressed me the most was that even though the sidewalls were flexing the actual contact patch stayed planted. Feedback was almost non-existent due to being overwhelmed by the flex but that is to be expected. 
About this time is when 2WF was invited to the Pirelli Night Dragon press release in Daytona Beach. While speaking to one of Pirelli USA's higher-ups (is VP high enough?) I mentioned that I had just put the Rossos on an FJR. His eyebrows went up so fast I thought they were going to fly off. After explaining the slight pre-release information gap and how they were doing so far, he told me to let Pirelli know what kind of mileage I got out of them as they never tested them on that heavy of a bike. I of course felt honored to be Pirelli's guinea pig and agreed to pass that info along.
After getting back from that press launch I decided to put the tire pressure up to 40/40 instead of 34/36 and see if that would eliminate the wiggles (from the tire NOT the children's TV show). This was suggested by a couple of Pirelli Tire engineers and since I was already torture-testing their design beyond it's limits I thought I'd at least listen to their suggestions.
Turns out that at slow speeds the higher tire pressure did indeed settle the tires down and took care of the sidewall flex. Strangely enough, while the high-speed sweepers also smoothed out with the higher pressures, the mid-speed corners, while infinitely better, still exhibited some sidewall flex. I'm sure that an engineer, rocket scientist, or theoretical physicist could explain the reason to you better than I could (because I can't) so I won't even try.
I've put about 2k miles on the tires now and I feel comfortable with getting the FJR over enough to once again start grinding the peg feelers (what's left of them) while cornering. Tire feedback, even in those mid-speed corners, has increased dramatically and I have yet to feel uncertain about traction since maintaining the higher tire pressures.
One of the most impressive aspects of the tire is its ability to inspire confidence when the road is less than dry. I'm the first to admit that I am a wuss on wet roads. The Rossos are as good (if not a little bit better) than the best of the tires previously mounted to the bike. It's actually a little freaky how these tires, even when ridden at a moderately fast pace (about 1/2 of a dry road pace) stick to the wet road and return decent feedback and unquestionable control.
Which brings us to the big question; would I buy a set to put on the FJR again. I think the answer is clear; No probably not. It is abundantly clear that the tire isn't designed for the FJR and therefore does leave room for other tires to blow right by in most categories.
What I do find amazing though is the rank I would give these tires out of all the tires I have used on the bike to this point.
1) Avon Storms
2) Avon Azarros
3) Pirelli Diablo Rosso
4) Metzler Z6
5) Metzler Z4
Third place out of a field of five different tires in a class that the Rossos have no business being in is pretty impressive. To me that says more about the performance capabilities of the Pirelli Diablo Rossos than if I had put them on a sportbike and reviewed them that way.
So if these tires were an NBA or NFL player he wouldn't be the best on the field but he would be good enough to keep the outfield from slacking off and make the pitcher earn his pay. Which, when you think about it, is more than a lot of dedicated baseball players can say.
So if you are riding a bike that doesn't see a lot of track time or doesn't need the top-of-the-line Corsa III's, you owe it to yourself to check out the Pirelli Diablo Rossos. Heck, if they work so well on an FJR just think how good they'll work on a bike they're actually made for!
For more information and to get all the technical bits head over to Pirelli USA.
For more tire talk and feedback head on over to our Pirelli Diablo Rosso Forum
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