Hey Guys: Hope this isn't a re-post. Since purchasing my HP-4 on 8-1-14, I've loved the engine and brakes. I've hated the handling. (only person in the world that doesn't like it, right?) At 205-210 in gear, the suspension has been unduly harsh, transmitting every road irregularity through the bars and frequently bouncing me a good ten inches out of the seat on what should have been minor bumps. As delivered, front and rear preload were full soft. Based on an article in Sport Rider magazine, I set the the forks at -5 and the rear at -4 compression and rebound. Huge improvement but no real joy when riding fast. I've always suspected the recommended tire pressures for the Pirelli Super Corsas were way too high. When racing, pressures were always in the 28-32 range. There was one thread here where someone said Nate Kerns recommended 27-27 on the track. A quick search brought up this info:
Diablo Racer.com • View topic - Pirelli Tire Pressures
"These pressures are general pressures for both DOT's and Slicks. Pirelli works with pressures in the only truly accurate way and that is once the carcass has been heat soaked. You should think twice about any tire tech or vendor that simply tells you to set cold pressures and be on your way. This goes for all tire brands. There are way to many variables in working simply from cold pressures such as ambient temp, track temp, humidity, track surface, cloud cover, nitrogen and the list goes on. The best way is to start with a base cold pressure of around 29psi front and 26psi rear. Warm the tires as suggested in the Tire Warmer Post and then set the pressures once again coming off the warmer.
The range for the front tire is 30-34psi and the rear is 25-28psi. Pressures should be checked everytime the bike comes off the track. Record the prssures and adjust if needed to get final hot pressure. Once this is done, you can allow the tires to cool to ambient and check cold pressures to get a good base number for the you and the bike on that day at that track. Be sure to keep an eye on track temps. It's amazing what even some clouds can do!
[URL=http://s603.photobucket.com/albums/tt119/orionmot/?action=view¤t=_DSC1931.jpg] [/url]
Tuning the tires:
This is not an exact science but here are some good hints. The range of the front is 30-35 hot. A higher pressure will give the rider a firmer feel under breaking and turn in but the level of grip tends to decrease as the pressure increases. The tire will feel more precise and offer more or even too much surface feedback. Pressures on the lower side will offer maximum grip but will feel less precise on turn in and may tend to move around more under breaking. Most riders tend to prefer 32-23 as a true hot pressure. Riders who prefer running the tire in the higher end of the pressure range should consider testing a harder compound tire at a lower pressure. Riders who tend to run the front tire in the lower pressure range should consider testing a softer compound tire at a higher pressure. People are often mistaken in thinking a harder compound tire has a stiffer sidewall or different carcass when really the main difference is that a harder compound is exactly that. It's harder and tends to move around less on the actual carcass giving the feeling of a stiffer carcass or sidewall. Keep in mind that the stiffer set up could also cause chatter.
The rear tire should be run in a range from 25-29psi. The tire may start to spin and feel greasy above 30psi.
Ideal pressures for sprint racing tend to be around 26psi Hot! The chasis may need some work if the tire feels squishy to the rider at these pressures but set up and correct it. Keep in mind that the squishy feeling of a soft pressure will go away as the tire builds heat and the pressure rises during a session or race."
I'm going to try the 29 front/ 26 rear cold recommendation tomorrow. I'm hoping now suspension adjustments will do some good without the ridiculously high 36/42 ( probably 40/46 hot) recommended by BMW. Hopefully this will help anyone else struggling and considering the 6K move to Ohlins front and rear.
On a side note, I never liked the geometry with the zero spacers. I installed the +3mm ride height spacers. I plan to raise the forks 1-2 lines on the triple clamps as well.
Diablo Racer.com • View topic - Pirelli Tire Pressures
"These pressures are general pressures for both DOT's and Slicks. Pirelli works with pressures in the only truly accurate way and that is once the carcass has been heat soaked. You should think twice about any tire tech or vendor that simply tells you to set cold pressures and be on your way. This goes for all tire brands. There are way to many variables in working simply from cold pressures such as ambient temp, track temp, humidity, track surface, cloud cover, nitrogen and the list goes on. The best way is to start with a base cold pressure of around 29psi front and 26psi rear. Warm the tires as suggested in the Tire Warmer Post and then set the pressures once again coming off the warmer.
The range for the front tire is 30-34psi and the rear is 25-28psi. Pressures should be checked everytime the bike comes off the track. Record the prssures and adjust if needed to get final hot pressure. Once this is done, you can allow the tires to cool to ambient and check cold pressures to get a good base number for the you and the bike on that day at that track. Be sure to keep an eye on track temps. It's amazing what even some clouds can do!
[URL=http://s603.photobucket.com/albums/tt119/orionmot/?action=view¤t=_DSC1931.jpg] [/url]
Tuning the tires:
This is not an exact science but here are some good hints. The range of the front is 30-35 hot. A higher pressure will give the rider a firmer feel under breaking and turn in but the level of grip tends to decrease as the pressure increases. The tire will feel more precise and offer more or even too much surface feedback. Pressures on the lower side will offer maximum grip but will feel less precise on turn in and may tend to move around more under breaking. Most riders tend to prefer 32-23 as a true hot pressure. Riders who prefer running the tire in the higher end of the pressure range should consider testing a harder compound tire at a lower pressure. Riders who tend to run the front tire in the lower pressure range should consider testing a softer compound tire at a higher pressure. People are often mistaken in thinking a harder compound tire has a stiffer sidewall or different carcass when really the main difference is that a harder compound is exactly that. It's harder and tends to move around less on the actual carcass giving the feeling of a stiffer carcass or sidewall. Keep in mind that the stiffer set up could also cause chatter.
The rear tire should be run in a range from 25-29psi. The tire may start to spin and feel greasy above 30psi.
Ideal pressures for sprint racing tend to be around 26psi Hot! The chasis may need some work if the tire feels squishy to the rider at these pressures but set up and correct it. Keep in mind that the squishy feeling of a soft pressure will go away as the tire builds heat and the pressure rises during a session or race."
I'm going to try the 29 front/ 26 rear cold recommendation tomorrow. I'm hoping now suspension adjustments will do some good without the ridiculously high 36/42 ( probably 40/46 hot) recommended by BMW. Hopefully this will help anyone else struggling and considering the 6K move to Ohlins front and rear.
On a side note, I never liked the geometry with the zero spacers. I installed the +3mm ride height spacers. I plan to raise the forks 1-2 lines on the triple clamps as well.