Thunderhill Highside Turn 2 4/1/2018

[Smash Allen]

You’re confusing me here. LOL. ��. Initially you said OP gear was too low. Meaning he should of shifted up 1. Now you said his RPM too low, so he should of shifted down 1. Which one is it? OP states he was in 3rd doing 7-8k RPM. I’d assume he should of been in 2nd doing 8-9k RPM. Does higher RPM make the bike handle better or easier to get around corners or does RPM not matter at all?

for me (and my limited experience) i am riding s1000rr with 15/43 sprockets. i shift from 5th to 3rd for turn 1 and keep it in 3rd until exit of turn 6

run the highest rpm you can smoothly manage to maximize power to the ground. i could downshift coming into turn 9, but leaving it in 4th lets me (and my limited experience) go wfo sooner and thus put more power to the ground, ultimately going faster

 

[afm199]

You’re confusing me here. LOL. ��. Initially you said OP gear was too low. Meaning he should of shifted up 1. Now you said his RPM too low, so he should of shifted down 1. Which one is it? OP states he was in 3rd doing 7-8k RPM. I’d assume he should of been in 2nd doing 8-9k RPM. Does higher RPM make the bike handle better or easier to get around corners or does RPM not matter at all?

There is no set RPM that dictates the gear. An SV650 at 8-9k rpm is almost at redline. An R6 is barely in the power band. Don't over think this. Don't even look at your tach or speedometer for clues on what gear to be in. Look at the drive you get out of the corner. If it's slow, powerless, with no grunt, you need to get your rpms up, the gear down. If you get a great drive out of the corner, you're in the right gear. Forget rpms. I couldn't tell you what rpms I am in at any corner at Thill.

for me (and my limited experience) i am riding s1000rr with 15/43 sprockets. i shift from 5th to 3rd for turn 1 and keep it in 3rd until exit of turn 6

And that's the difference between a liter bike and a smaller bike. On my 1000 I will sometimes use one gear from T1 to T6, and often two. On my 750 I will always use two gears.

 

[stangmx13]

run the highest rpm you can smoothly manage to maximize power to the ground. i could downshift coming into turn 9, but leaving it in 4th lets me (and my limited experience) go wfo sooner and thus put more power to the ground, ultimately going faster

thats not entirely how that works. "power to the ground" is actually drive force. drive force is higher in lower gears with the same power output. so, its very possible that ull accelerate quicker in 3rd at 70% throttle than 4th at 100% throttle. and of course, power output is determined by both throttle position and rpm. since the rpms are higher in lower gears, u get what seems like a lot more drive force at less throttle.

ultimately, the amount of drive force u can use is limited by the rear tire. so if you rode perfectly, say 10% wheel spin for maximum drive, the better drive is largely affected by when the tire stops spinning. if the spin stops when u are still in 3rd and/or u never spin in 4th, 3rd was likely faster. if you can spin the rear through 3rd AND 4th, using 3rd probably wasn't any faster. but of course, we don't ride perfectly.

IMO, most of the time ppl go faster in the higher gear for 2 reasons:
1. the throttle response is less nervous at a lower rpm and the max drive force is lower. so they feel more comfortable, allowing them to use more drive force.
2. their roll speed is higher because there's less engine braking and they had to manage fewer downshifts.

 

[Smash Allen]

thats not entirely how that works. "power to the ground" is actually drive force. drive force is higher in lower gears with the same power output. so, its very possible that ull accelerate quicker in 3rd at 70% throttle than 4th at 100% throttle. and of course, power output is determined by both throttle position and rpm. since the rpms are higher in lower gears, u get what seems like a lot more drive force at less throttle.

ultimately, the amount of drive force u can use is limited by the rear tire. so if you rode perfectly, say 10% wheel spin for maximum drive, the better drive is largely affected by when the tire stops spinning. if the spin stops when u are still in 3rd and/or u never spin in 4th, 3rd was likely faster. if you can spin the rear through 3rd AND 4th, using 3rd probably wasn't any faster. but of course, we don't ride perfectly.

IMO, most of the time ppl go faster in the higher gear for 2 reasons:
1. the throttle response is less nervous at a lower rpm and the max drive force is lower. so they feel more comfortable, allowing them to use more drive force.
2. their roll speed is higher because there's less engine braking and they had to manage fewer downshifts.

all that makes sense and agrees with my understanding. poor move to reference turn 9 i guess since wheelie tendency is the limiting factor rather than rear grip (at least in my limited experience)

 

[afm199]

all that makes sense and agrees with my understanding. poor move to reference turn 9 i guess since wheelie tendency is the limiting factor rather than rear grip (at least in my limited experience)

Yes, T9 at thill is different than most turns because of the drop off exit, where wheelies come easily. I put an SV almost vertical there one day, being a bit over engaged.

 

[Sportbiker]

he was in race mode and his foot levered the rear off the ground

rain -> sport -> race -> slick (+/-7)

Gotcha. I keep forgetting that in those fixed modes, TC isn't adjustable on the fly. I leave mine in user-mode, program all settings same as Race mode & then adjust the TC setting as needed. (mine is the next gen)

 

[Fjr17]

Which tires were you running? If you were on street tires that could explain a lot why the tires spun at that lean angle.

 

[Alekos]

Which tires were you running? If you were on street tires that could explain a lot why the tires spun at that lean angle.

I was on Pirelli SC1(F)/SC2(R). Rear pressure was ~28 in warmers. The rear tire was at the end of its life on the left side (wear bars almost flush with rest of tire's tread), so that definitely did not help. It was my 4th track day on these tires and I knew at the beginning of the day that I would probably have to change tires but the tires did not show any symptoms in the first sessions of the day.

If you look at the video (at the 20sec mark), it is debatable what happened first: scraping my boot/peg and lifting the rear and sliding, or sliding the rear and that's why you can hear the peg scraping sound (both happen almost instantaneously).

 

[afm199]

however I added a tiny bit more lean as I came on the gas, .

That's is why you crashed.

It wasn't the tires, it was your technique.

 

[Alekos]

That's is why you crashed.

It wasn't the tires, it was your technique.

I was not arguing whether I made a mistake or not, by now it is pretty clear to me that my technique was wrong and I made a mistake.

The point about tires was just "had I had better tires would my mistake not resulted in a slide". I suspect it might have if I indeed slid before scraping, since that mistake in my technique could be more of a bad habbit (bad technique in general) rather than incidental, yet it did not cause me to crash before. Keeping in mind of course that the margin of error becomes smaller as speed and lean angles increase (as mentioned by others in this thread).

 

[sniper1rfa]

drive force is higher in lower gears with the same power output.

In theory, this isn't true. If the power output is the same between both gears, drive force will be the same.

That said, power output of an engine is load dependent, and engines will make more power with more load, even if the RPM and throttle position are the same.

So there are many cases where you actually will make more power, and thus accelerate faster, in a higher gear. This would be much more pronounced in lower gears than higher gears, so short shifting a bit is often going to be fastest in gears 1-4. Smoother power application in higher gears is a sweet bonus.

 

[stangmx13]

In theory, this isn't true. If the power output is the same between both gears, drive force will be the same.

That said, power output of an engine is load dependent, and engines will make more power with more load, even if the RPM and throttle position are the same.

So there are many cases where you actually will make more power, and thus accelerate faster, in a higher gear. This would be much more pronounced in lower gears than higher gears, so short shifting a bit is often going to be fastest in gears 1-4. Smoother power application in higher gears is a sweet bonus.

u have it backwards. in theory, what I said is true. in practice, there are more things going on. u cant get from Watts to Newtons through a drivetrain and tire without including the gear ratio and its torque multiplication. if torque is multiplied, so is drive force.

making more power != accelerate faster when u are comparing diff gear ratios. thats just wrong.

 

[sniper1rfa]

Power is not modified by gears. Power into a gearbox is always the same as power out of the gearbox.

Gearboxes trade torque for rpm at constant power (minus frictional losses).

The graph shows more peak power (and more torque) in higher gears.

Power is the only thing that matters for acceleration.

 

[stangmx13]

Power is not modified by gears. Power into a gearbox is always the same as power out of the gearbox.

I didnt say that.

Power is the only thing that matters for acceleration.

nope.

u rly should try to calculate drive force yourself.

 

[sniper1rfa]

I know this is pointless internet shit as well as totally off topic, but I'm really bored.

I've labelled the above graph with optimal shift points based on that dyno run (which is not entirely real life, but illustrates the point). Note how early you need to shift in order to produce the most power.

The 1-2 shift happens before you even reach peak power in 1st, because it's more beneficial to short-shift into second practically as soon as possible. All the other shifts happen far earlier than expected, and only shortly after peak power in a particular gear.



As for your 'drive force' thing. Horsepower = (Torque*RPM)/5252. You have a couple gear options for each wheel RPM - you want the one with the most power. Since the wheel RPM is the same (you're going the same speed), the gear option with the most power will also have the most torque (at the wheel, where it matters).

 

[stangmx13]

As for your 'drive force' thing. Horsepower = (Torque*RPM)/5252. You have a couple gear options for each wheel RPM - you want the one with the most power. Since the wheel RPM is the same (you're going the same speed), the gear option with the most power will also have the most torque (at the wheel, where it matters).

You are so close to understanding what drive force is. So since we want the most torque at the rear wheel for the highest drive force... and since a gearbox multiplies torque, that says what about comparing drive force btw two gears? Assume power&torque are the same since we don’t know the output for this theoretical bike.

Ya u are off topic. The only point of mine u decided to argue about was a theoretical drive force comparison. Uve now picked a weird vehicle to make a point about shift points. Yes, I know that the steeper power falls off after max, the more likely you’ll have to shift before redline. My race R6 gets shifted at 15.5k even though it’ll spin to 16.5k. Each shift differs by a little because the gearbox matters, but it’s only 200rpm max and I can’t set my shift light different for each gear.

 

[sniper1rfa]

You can test this, since you don't believe me. Take your bike, get it dyno'd in every gear and overlay the dyno plots for each gear as above (either power or wheel torque vs wheel speed, it doesn't matter - they're the same thing).

Then do two drags - one shifting at your normal 15.5krpm, and one shifting at the speeds indicated by the crossover of each dyno plot (which will have you shifting earlier than normal).

I bet you're leaving speed on the table, and by being in a higher gear for longer you're also dealing with more difficult throttle response than you need to. The folks you originally responded to are probably correct - a higher gear not only feels faster a lot of the time, it almost certainly *is* faster. The guy who said 'ignore speedo and tach when shifting' is easily the most correct response, because you should be shifting based on feel if you haven't done the above test with your particular setup.

 

[stangmx13]

where did i say i didnt believe u :facepalm

dealing with more difficult throttle response at 15.5k? wth are u talking about? its a race bike!! im only at 15.5k at WOT and then i pop the shift. and now you are advocating the butt dyno? OMG, stop

lets also acknowledge that the example plot u found is for a side-by-side that has 5 gears and only does 75mph. when talking about things where load, gearbox, and power matter a ton, u really picked a vehicle that differs dramatically from my bike and the OPs. u think the rpm drop from 2nd to 3rd is anywhere comparable btw that 4wheeler and my R6... unlikely. yes, the concepts still apply, but the amounts will vary considerably because of all the differences.