Ninja H2 Understeer - ZX Forums
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post #1 of 12 (permalink) Old 10-06-2019, 10:11 PM Thread Starter
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Ninja H2 Understeer

Here's a vid to show highlight a problem that I will have to address for next season.


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post #2 of 12 (permalink) Old 10-06-2019, 10:33 PM
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Quote:
Originally Posted by Turbo329 View Post
Here's a vid to show highlight a problem that I will have to address for next season.

I have always been taught that a bike that won't finish a turn needs more trail. My 07 GSXR750 track bike is famous for it. Can you raise the front or lower the rear a little? I went with lowering the forks all the way down in the triples and putting on an Attack triple with a different insert to push the forks 1mm forward. Problem solved.
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post #3 of 12 (permalink) Old 10-07-2019, 09:04 AM Thread Starter
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Quote:
Originally Posted by 57x View Post
I have always been taught that a bike that won't finish a turn needs more trail. My 07 GSXR750 track bike is famous for it. Can you raise the front or lower the rear a little? I went with lowering the forks all the way down in the triples and putting on an Attack triple with a different insert to push the forks 1mm forward. Problem solved.

Great points. I'm definitely sending this clip to my tuner and we're going to run the geometry numbers for sure. This is definitely causing me about 3-4 seconds per lap. Once I get this sorted I'm hands down one of the fastest guys on this track. I can feel it.

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post #4 of 12 (permalink) Old 10-08-2019, 10:45 PM
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Another one to look at is what my H2 SX had. The H2 SX has ~139mm rear travel instead of what is the normal 120mm on many sport bikes. I could not get sag on my bike no matter how I tried thinking it was the standard 120mm sport bike travel. Once I adjusted to the standard 1/3 of travel sag (40mm vs ~46mm) all was good. I almost changed springs but knew something was off. I understand that the H2 and H2 SX have the same swingarm travel, but please confirm. I am very happy now with the correct sag.
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post #5 of 12 (permalink) Old 10-09-2019, 10:46 AM
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Turbo, where is your sag set? Could it be off considering the travel on these and therefore the shock is not in the sweet spot?
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post #6 of 12 (permalink) Old 10-10-2019, 04:30 AM
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I experimented with suspension settings on my old ZZR 1200 and I found understeer and running wide was induced by going really soft in the rear where the rear would squat and the front extend, so I would think stiffening the rear and raising the tubes in the trees would help. Seems like dropping the tubes would do the opposite.

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post #7 of 12 (permalink) Old 10-10-2019, 07:52 PM Thread Starter
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When my tuner sets my suspension I tend not to ask him questions. hahahahahah He does it for me at the track, then I go out for a session and come back in. I want to assume that it's at 30mm as that's the standard recommendation.

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post #8 of 12 (permalink) Old 10-13-2019, 01:32 PM
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Raising the yokes (dropping the fork tubes) will increase the trail, but will also increase the rake and that will make it run even wider. Less offset in the yokes will help, but making the front longer and more stretched out won't. Quite the opposite.

Try bending a chopper with extended forks and raked-out neck around a tight bend and you'll know what I mean. They have tons of trail.

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post #9 of 12 (permalink) Old 10-13-2019, 04:09 PM
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Quote:
Originally Posted by Hammerhead View Post
Raising the yokes (dropping the fork tubes) will increase the trail, but will also increase the rake and that will make it run even wider. Less offset in the yokes will help, but making the front longer and more stretched out won't. Quite the opposite.

Try bending a chopper with extended forks and raked-out neck around a tight bend and you'll know what I mean. They have tons of trail.
That's the other extreme of trail HH. You don't want either extreme. And the raked out forks have an issue on corner entry more than corner exit.

I'd agree on most Kawasaki's to never raise the front, but the only way to make most Triumphs and Suzukis turn is to add trail. They have too little. Everyone seems to follow Dave Moss. Look at his write up on his Speed Triple. The only thing that helped it finish a corner was to raise the front of the bike and it still sucked. He finally gave up on the bike and sold it. A friend has it now and it will probably be parted out.

Trail is easy to measure. There is a ton of details online where the sweet spot is. I'm not telling you that you have too little trail, but rather measure it and confirm.

It also could be you are too hard on the gas on corner exit and the speed is pushing you out. Twist of the wrist describes this. Maybe a little more trail braking, combining brake and throttle initially at apex will keep the bike's attitude correct to slow the push after apex. I read an article too long ago on Stoner's corner technique that worked for him where he tended to break the back end of the bike out on corner exit to help him finish the corner. It's hard on the tires for sure. I know I don't have the ability to slide a corner exit. I can trail brake in, but the thought of throttle and brake on exit just freaks me out.
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post #10 of 12 (permalink) Old 10-13-2019, 06:00 PM Thread Starter
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Quote:
Originally Posted by 57x View Post
It also could be you are too hard on the gas on corner exit and the speed is pushing you out. Twist of the wrist describes this. Maybe a little more trail braking, combining brake and throttle initially at apex will keep the bike's attitude correct to slow the push after apex.
I thought this could have been the case but honestly, I only barely cracked the throttle and it pushed wide. In the video I was knee over the grass and still went wide. You could see my rear wheel even squat on the straight away more than usual. I think the problem is mostly with the rear suspension.

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post #11 of 12 (permalink) Old 10-13-2019, 06:04 PM
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It is a long damn swingarm
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post #12 of 12 (permalink) Old 10-13-2019, 07:18 PM
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Quote:
Originally Posted by 57x View Post
That's the other extreme of trail HH. You don't want either extreme. And the raked out forks have an issue on corner entry more than corner exit.

I'd agree on most Kawasaki's to never raise the front, but the only way to make most Triumphs and Suzukis turn is to add trail. They have too little. Everyone seems to follow Dave Moss. Look at his write up on his Speed Triple. The only thing that helped it finish a corner was to raise the front of the bike and it still sucked. He finally gave up on the bike and sold it. A friend has it now and it will probably be parted out.

Trail is easy to measure. There is a ton of details online where the sweet spot is. I'm not telling you that you have too little trail, but rather measure it and confirm.

It also could be you are too hard on the gas on corner exit and the speed is pushing you out. Twist of the wrist describes this. Maybe a little more trail braking, combining brake and throttle initially at apex will keep the bike's attitude correct to slow the push after apex. I read an article too long ago on Stoner's corner technique that worked for him where he tended to break the back end of the bike out on corner exit to help him finish the corner. It's hard on the tires for sure. I know I don't have the ability to slide a corner exit. I can trail brake in, but the thought of throttle and brake on exit just freaks me out.
The too much oomph on exit theory has validity. Several years ago, Marquez and Pedrosa were side-by-side coming out of the infield and onto the main oval at Indy when Marquez's peg caught and disconnected Pedrosa's rear wheel sensor cable. Upon exit, Pedrosa hammered it, and instead of getting smooth, electronically-controlled acceleration, he got a huge highside (the extreme of running wide) when the power hit.

If you were to tear the outer parts off a current Harley tourer, you'd notice that the steering head is AHEAD of the tubes/axle center rather than slightly behind, and this provides enough trail to make one of those whales manageable at parking-lot speeds.

It may be a pig, but it's a pig with a rocket in it's ass!
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