losing 2 seconds on Pirelli tires?

Jo Rhett jorhett at fastlizardracing.com
Mon Oct 4 15:06:07 PDT 2010


In 2007 and 2008 I ran Pirelli tires all season.  I was quite happy with them, but we were always fighting issues with tire wear.  1/2 a pound difference here or there and I'd burn great big wear regions into the rear tire.  In 2008 Pirelli completely screwed me for $3k in tire contingency money.  So I left them and went to Bridgestone.

I swapped from Pirelli to Bridgestone slicks at lunch.  Right away, first session on the Bridgestones, I went half a second faster than I had all day on Pirelli.  We added some rear compression to get the rear tire grip and I dropped another 1.5 seconds in the 2nd session.  Sweet.

I never, ever had any tire wear problems with the Bridgestones.  In fact, I had to get really good at keeping a tire log because the tires would just go-go-go.  Once I realized I had done 2 solo endurances, 3 sprints, 12 practices and 4 days (7 sessions each) at track providers on the tires and the grip was still good.  Not great -- swapping to new tires gave me back 1.5 seconds instantly, but yeah I had to keep a log to know when to swap tires or I'd ride them way too long.

So why am I going back to Pirelli?  One thing was availability -- Bridgestone wasn't at all the tracks (although this may be fixed now).  The second was that Bridgestone doesn't have a DOT 160 rear tire.  The only thing they can give me is a street tire -- which has awesome tire life, but starts giving up grip and bids to toss you on your head on the 6th lap.  (I thought it was just me until I found 2 other reviews of the tire which said the exact same thing)

I really don't want to run Bridgestone on one bike and Pirelli on the other, so I full went back to Pirelli.  (I also got some personal assurances that the tire contingency thing wouldn't happen again)

I felt good on them right away, and they seemed to hook up as well as I remembered.  We ended up reversing the suspension change, dropping rear compression to get rear tire grip, but that makes perfect sense.  The only gotcha is... I've lost 2 seconds. On both bikes, at two different tracks.

I went to Pirelli first on the Superstock mid-day at Buttonwillow.  I went back out and was immediately 4 seconds slower.  I dragged that back to 2 seconds, but can't seem to crack that wall.  I figured it was in my head, but the next morning I went out on Pirelli slicks and also lost 2 seconds.

Then I went to Thunderhill and was also 2 seconds down there.  Comparing the lap times in my log made me realize the consistent 2 second difference (I didn't clue in right away).   I spent 4 days in late June working with Moss, et al to try and make the tires work better and I never recovered the 2 seconds.  They feel fine, I have no discomfort on the tires, everything seems up to par... but I'm 2 seconds down.

Paying attention to the tires and how they ride, my best guess is that they aren't delivering as much grip as a pick the bike up and drive out of the corner.  I noticed that even when railing out of a corner with the throttle wide open (ie turn 6 or turn 15 at Thunderhill) I never had to worry about running off the track.  They never pushed me out that hard.

Anyone out there got any clues about how to make the Pirelli deliver?   I'm done with surgery drama and back on the bike Oct 13 at Infineon, so I'm hoping to find something I can try to make the tires deliver.

-- 
Jo Rhett /  velociRaptor Racing
#553 WERA



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