Flyguy
Well-known member
Let me say at the outset that my interest here is purely from an engineering standpoint. I have no bones to pick with any mfg or genre of bike. This topic became interesting to me as a side product of taking some tire footprints at various air pressures to maximize braking performance on a number of bikes.
It appears to me that the weak link in the performance chain is not brakes, suspensions or even engines. It is the 4.5 to 8 sq. in. contact patch of the tires. That's precious little contact with terra firma. Cars have the advantage of being able to utilize flat tread faces on their tires allowing much more contact area. Want more traction? Simple. Put on much wider, stickier tires and upgrade the suspension accordingly. Bike? Forget it. Going wider is not only expensive, you are limited to a very narrow range of acceptable profiles and actually get very little from upsizeing even if you do it right and use wider wheels. Being limited in the lateral acceleration that they can achieve, bikes rely on their overall narrowness to make the curve straighter to maximize cornering speeds rather than traction. Form is everything.
Horsepower is fun but it can quickly become your enemy. Denny Hulme said of driving the 1,200hp Porche 917 K3 that " you can punch it to the floor in top gear at 180mph and break the rear tires loose!" He said that driving it in the dry was like driving most cars in the wet. He used a variable boost control to limit power because it was FASTER! Now we are seeing the focus shift on leading edge racing bikes from power to traction devices. Traction controls and wheelie controls, which are really a power limiter of one sort of another, slipper clutches, and ABS brakes (street) are all aiming at allowing the rider to dance on the edge of the envelope more acutely as opposed to redefining the envelope. Recently we've seen Kaw utilize "flies" and Suzuki lead the way with multiple maps to limit power. Maybe they know something.
It seems to me that the 600cc class sportbikes are pretty much the top of the performance/hp curve. From here more power means more weight and tire abuse. Since that contact patch can't handle any more power in the turns or braking, riders of liter bikes have to make up for slower cornering speeds and longer stops with faster exits and straights. But this trade off is in favor of only top (or heavy) riders. The average guy is better able to take advantage of the lighter weight rather than the additional power and typically has faster laps on track day on the 600. The highly experienced and much practiced rider is probably just as fast on either. It takes the pro or elite street rider to take advantage of the prodigious output of the big bike and even then the difference is usually only 2 - 3mph (average). This is probably why the GP bikes were cut back to 800cc. I have not followed it but I would love to know what comparative lap times are on the 800cc bikes as compared to the old liter bikes. My guess is that they are about the same, or maybe even faster.
Anyone know?
Enter the 1,300cc sportbikes. Where we added 40-50 to get to 1,000cc's we now add another 110lbs with the same load capacity tires. Now we have enough power and weight to melt the tires and brakes in short order. In a 20 lap race the 600's would have them for lunch, forget the liter bikes. That would mean that these brutes are most at home on the drag strip. Now with the new '08 Busa there is so much power on tap that even the pro rider can't take advantage of it in standard form, calling it "unlaunchable". Seems Kaw asked themselves many of the same question I did but given their liability position elected to tame the bottom end of the tach to make their bike more user friendly to the masses. It's weight and upper end will still melt tires and brakes on the track and many cracked frames are coming to light (not sure if it's related) but those who want to ride it like a SV 650 can. Suzuki, in need of a leapfrog, chose to unleash the full rage of a 1,300cc high compression cannon on 7sq in of rubber. This could get ugly, in my estimation as 1:50 riders I see are "above average". 1 in 200 are "very advanced", yet 1 in 5 tell me they are well up to handling a liter bike.
Are we going way overboard on this power fix to the point we actually have LESS capability?
It appears to me that the weak link in the performance chain is not brakes, suspensions or even engines. It is the 4.5 to 8 sq. in. contact patch of the tires. That's precious little contact with terra firma. Cars have the advantage of being able to utilize flat tread faces on their tires allowing much more contact area. Want more traction? Simple. Put on much wider, stickier tires and upgrade the suspension accordingly. Bike? Forget it. Going wider is not only expensive, you are limited to a very narrow range of acceptable profiles and actually get very little from upsizeing even if you do it right and use wider wheels. Being limited in the lateral acceleration that they can achieve, bikes rely on their overall narrowness to make the curve straighter to maximize cornering speeds rather than traction. Form is everything.
Horsepower is fun but it can quickly become your enemy. Denny Hulme said of driving the 1,200hp Porche 917 K3 that " you can punch it to the floor in top gear at 180mph and break the rear tires loose!" He said that driving it in the dry was like driving most cars in the wet. He used a variable boost control to limit power because it was FASTER! Now we are seeing the focus shift on leading edge racing bikes from power to traction devices. Traction controls and wheelie controls, which are really a power limiter of one sort of another, slipper clutches, and ABS brakes (street) are all aiming at allowing the rider to dance on the edge of the envelope more acutely as opposed to redefining the envelope. Recently we've seen Kaw utilize "flies" and Suzuki lead the way with multiple maps to limit power. Maybe they know something.
It seems to me that the 600cc class sportbikes are pretty much the top of the performance/hp curve. From here more power means more weight and tire abuse. Since that contact patch can't handle any more power in the turns or braking, riders of liter bikes have to make up for slower cornering speeds and longer stops with faster exits and straights. But this trade off is in favor of only top (or heavy) riders. The average guy is better able to take advantage of the lighter weight rather than the additional power and typically has faster laps on track day on the 600. The highly experienced and much practiced rider is probably just as fast on either. It takes the pro or elite street rider to take advantage of the prodigious output of the big bike and even then the difference is usually only 2 - 3mph (average). This is probably why the GP bikes were cut back to 800cc. I have not followed it but I would love to know what comparative lap times are on the 800cc bikes as compared to the old liter bikes. My guess is that they are about the same, or maybe even faster.
Anyone know?
Enter the 1,300cc sportbikes. Where we added 40-50 to get to 1,000cc's we now add another 110lbs with the same load capacity tires. Now we have enough power and weight to melt the tires and brakes in short order. In a 20 lap race the 600's would have them for lunch, forget the liter bikes. That would mean that these brutes are most at home on the drag strip. Now with the new '08 Busa there is so much power on tap that even the pro rider can't take advantage of it in standard form, calling it "unlaunchable". Seems Kaw asked themselves many of the same question I did but given their liability position elected to tame the bottom end of the tach to make their bike more user friendly to the masses. It's weight and upper end will still melt tires and brakes on the track and many cracked frames are coming to light (not sure if it's related) but those who want to ride it like a SV 650 can. Suzuki, in need of a leapfrog, chose to unleash the full rage of a 1,300cc high compression cannon on 7sq in of rubber. This could get ugly, in my estimation as 1:50 riders I see are "above average". 1 in 200 are "very advanced", yet 1 in 5 tell me they are well up to handling a liter bike.
Are we going way overboard on this power fix to the point we actually have LESS capability?
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