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Old 04-21-2017, 06:05 PM   #1
abyzzim
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Violent vibration/wheel hop during understeer

My car drives fine under normal driving; however, during spirited driving and cornering fast will cause a violent vibration/wheel hop whenever the car understeers (the understeer itself is generally caused by my poor driving skills ). This happens for both left and right turns. Also, the path of travel during this violent vibration/wheel hop understeer is also quite straight, not a curved path.

What could be the cause of this?
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Old 04-30-2017, 12:42 AM   #2
KYLE323I
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Check your struts to make sure they aren't blown. If they haven't been replaced they most likely need to be. Also check to make sure your sway bar links are still connected.

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Old 04-30-2017, 08:45 AM   #3
Geo31
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Quote:
Originally Posted by abyzzim View Post
My car drives fine under normal driving; however, during spirited driving and cornering fast will cause a violent vibration/wheel hop whenever the car understeers (the understeer itself is generally caused by my poor driving skills ). This happens for both left and right turns. Also, the path of travel during this violent vibration/wheel hop understeer is also quite straight, not a curved path.

What could be the cause of this?
The previously mentioned poor driving skills.

You're literally driving the tires off the car. Could be a lot of mechanical things, but one thing for sure is you are turning the wheel when the front tires are not able to turn the car. Slow down before turning.
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Old 05-01-2017, 01:40 PM   #4
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The previously mentioned poor driving skills.

You're literally driving the tires off the car. Could be a lot of mechanical things, but one thing for sure is you are turning the wheel when the front tires are not able to turn the car. Slow down before turning.
Could it be that the tires I have on now (Maxxis MS300) are not very progressive? Because I'd like to think that I am a better driver than when I had my previous tires (Dunlop LM703). As of now, I do know how to load up the fronts during cornering and trailbrake to help the car rotate, but back when I didn't even know how to load the fronts and trailbrake, the Dunlop tires would squeal and understeered in a curved path everytime I understeered. Now with the Maxxis', when I do understeer, there is no squeal but a loud jarring vibration that can be heard in the car and can be felt through the steering wheel (and the car understeers quite straight too)...

Sorry for the weird questions, I am still new at performance driving and am trying to learn both theoretically and in practice.
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Old 05-01-2017, 02:46 PM   #5
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The tires could be absolute junk and I'd still say it's driving. You are simply over-driving your tires, and not in a small way. Your attempts at trail-braking are probably contributing to this in a major way.

If your car has a mechanical malfunction, unless it is severe, proper driving should eliminate the problem. Fixing mechanical issues will increase your grip level, but not fix the driving. Over-driving your tires is almost always a driving issue.
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Old 05-01-2017, 08:21 PM   #6
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The tires could be absolute junk and I'd still say it's driving. You are simply over-driving your tires, and not in a small way. Your attempts at trail-braking are probably contributing to this in a major way.

If your car has a mechanical malfunction, unless it is severe, proper driving should eliminate the problem. Fixing mechanical issues will increase your grip level, but not fix the driving. Over-driving your tires is almost always a driving issue.
Ahhh, I see. I think I get it now. I'm over-driving the tires... meaning that over-driving is with respect to the specific tires' grip level - in other words, I have to learn the grip limits of my tires.

Yes, my attempts at trail-braking are novice at best, and this violent understeer happens when I overcook the corner entry speed. There was one time; however, that I managed to cure the understeer through left-foot braking. Although the priority should still remain to prevent understeer from happening rather than curing it when it happens. Thanks Geo31!
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Old 05-01-2017, 09:06 PM   #7
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Glad to help.

You are trying techniques that are WAY beyond your skill level. This is not said to disrespect you. Everyone starts with the basics. I learned through kart racing and then progressing. Many here participate in open track days. I don't know if you have that opportunity, but here, novices get instructors. It really helps people learn the process.

If you want to do some reading, the classic text is The Technique of Motor Racing by Pierro Taruffi, although I'm not sure it's in print anymore. Otherwise, another good text on the subject is Bob Bondurant on High Performance Driving.
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Old 05-02-2017, 01:32 AM   #8
abyzzim
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Glad to help.

You are trying techniques that are WAY beyond your skill level. This is not said to disrespect you. Everyone starts with the basics. I learned through kart racing and then progressing. Many here participate in open track days. I don't know if you have that opportunity, but here, novices get instructors. It really helps people learn the process.

If you want to do some reading, the classic text is The Technique of Motor Racing by Pierro Taruffi, although I'm not sure it's in print anymore. Otherwise, another good text on the subject is Bob Bondurant on High Performance Driving.
I'll look for those references. Thanks again!
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Old 05-03-2017, 12:11 PM   #9
Geo31
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Oh, one other thing I'd suggest.

Google: Friction Circle

In short, friction circle theory holds that your tires only have so much grip and it can be used in a straight line (acceleration and braking) or sideways (cornering) or some combination there of. When you transition from straight to sideways and back, you have to give up some traction from one vector to use it in another.

I am always conscious of this every time I get behind the wheel, but especially on a race track (I NEVER try to drive at the limit on the street).
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