Another tyre thread - Pirelli Diablo 200/55

[twodear]

Last weekend I took Otis to the track for the first time in 6 months. Saturday was practice and Sunday had one qualifying session and three races (in my class anyway).

Saturday was not too helpful, there were rain showers, it was cold and windy and the existing Pirelli SC2 Diablo 120/70 front and 190/55 rear were toast from the previous track sessions as well as sitting around gathering dust.

A local dealer had set up shop to sell, mount and balance tyres for the race weekend. When I went to replace my tyres I was told that Pirellii is phasing out the 190/55 and we're expected to use the 200/55.

????whats with that?

I took the option of the 200 section SC1 rather than the 180 section, more on the flip of a coin since either choice would be a compromise.

As it turns out, the 200 section worked out okay. I was worried that in the least there might be clearance issues with the swing arm (no rear hugger to worry about) and that the tyre warmers wouldn't fit.

As far as performance - very good is all I can say. Having said that, merely being new tyres would be the majority of that in comparison with the ones that came off. I never touched the cylinder heads down so it is most likely I wasn't trying hard enough to give them a really good test.

For the day (cool track temp of about 25deg C) and my limp non-ballistic riding style, 29 PSI rear and 34 PSI front was good for the morning - some balling on the very edges but a dimpled surface everywhere else. In the afternoon 31 PSI in the rear took care of the slight amount of what looked like a melted surface.

Next time, I might go to slicks or Metzler Racetec K1 or K2 - quite a few faster guys were giving good reports on them.

Opinions please?

[Noblehops]

Pressures sound high for track/race use. But admittedly it's been a while. Who advised those numbers?

N.

[twodear]

There is always heaps of advice in the paddock but in general they were all over the place. I tried to find a general concensus. Guys using slicks were down to 22 PSI but most others with treaded tyres were in the same range I was using. There may also be some difference in pressure gauges.

I need to add that these are hot pressures with the tyre warmers at 75 deg C.

At the end of the day, pressures were a result of trial and error. Cold tearing was occuring at higher pressure and there were beginnings of melting at lower pressure. The Pirelli guy looked at mine and said the surface appearance was right, so stick with what I had. They gave very good and confident feeling. None of the slippy/slidey from the day before.

[poldar12s]

Originally Posted by twodear

Guys using slicks were down to 22 PSI but most others with treaded tyres were in the same range I was using. There may also be some difference in pressure gauges.

I need to add that these are hot pressures with the tyre warmers at 75 deg C.

This track thing always confuse me. You mean hot pressure 34 front and 29 or 31 psi at 75 degree C (=167 degree F) for rear. I measured my hot pressures for mine after 180 miles of freeway and canyon. 40 front and 44 rear. It means I wouldn't get friction like you on the track during my aggressive canyon ride. For rear, it is more than 10 psi different. Perhaps another reason to go slower.

[twodear]

I'm guessing that your tyres are probably more for touring and high mileage rather than the soft compounds used for the track. I don't expect to get 500 km out of this set.

40 and 44 sound okay for the highway for normal tyres and should give the best compromise for in regards to life and grip.

[poldar12s]

Yeah, think so. But, its good to hear about the hot pressure. When I want to ride hot, I may take out air about 5 psi from front and 10 from rear to see any difference at canyon. Before long freeway ride, I should put air back though.

I'm curious whether your tire pressure will further go up while riding beyond 75 degree C though. Done any measurement?