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Old 07-17-2009, 08:34 AM   #1
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Default Suspension Question...what causes "hop" or "jump" when you hit a bump at higher speed

Ok so Iam going around a corner at about 75 that is on a 2 lane highway. The corner is a onramp bridge connecting 1 highway with another. The bridge is one of those segmented bridges that has connections that don't fit or line up perfectly thus causing bumps between the 2 parts joining together. So is it just perfectly normal that even on a high performance car such as the C5 corvette that when your going this fast (the speed limit said 65 for going around this somewhat sharp turn) that your corvette would hop or bounce out and give you a bit of a scare for stepping out and hopping over to the right a bit. I know it wasn't long that the car was in the air but it felt it. When it touched down, cruise kicked off, active handing enabled, and etc etc. I just didn't expect the car to launch and jump the way it did as there was no physical bump that I saw in the road? My car has 78,000 miles on it. Could it possibly be that the shocks are going? I tried bouncing the rear up and down and I don't get any type of bouncing or anything. I don't see any fluid from the shocks either. Are our shocks good to 100,000 miles?

Thanks
Jeff
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Old 07-17-2009, 08:56 AM   #2
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When I first bought my FRC, I had similar issues as you with my OEM Z51 shocks (they had 60K on them). When I pulled them off to install the Bilstein Sports, they seemed to have really good pressure still...That being said, the Bilstein Sport shocks did improve the hopping/sidestepping issue when hitting a bump while going through a curve...
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Old 07-17-2009, 09:19 AM   #3
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Quote:
Originally Posted by Gideon's_Test View Post
When I first bought my FRC, I had similar issues as you with my OEM Z51 shocks (they had 60K on them). When I pulled them off to install the Bilstein Sports, they seemed to have really good pressure still...That being said, the Bilstein Sport shocks did improve the hopping/sidestepping issue when hitting a bump while going through a curve...
"sidestepping"...EXACTLY! I knew there was a term for it...just couldn't think of it...thanks man!

Bilstein Sports huh...what did you pay for em? Did you notice any change as far as harshness of your ride?
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Old 07-17-2009, 09:49 AM   #4
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I paid $300 shipped...They are firmer than Z51 shocks...Once in awhile I think when I go over a particularly noticable bump that maybe they are a smidge too firm, then when I'm accelerating through a freeway entrance ramp I think "nah, it's great, wouldn't change a thing"...
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Old 07-17-2009, 10:12 AM   #5
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What tires are on the car? How old are they? Are you lowered? These things will also affect the ability of the car to handle mid-corner bumps.
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Old 07-17-2009, 10:15 AM   #6
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Originally Posted by TarHeelDan2001 View Post
What tires are on the car? How old are they? Are you lowered? These things will also affect the ability of the car to handle mid-corner bumps.
These three are the biggest factors.

Old tire and car lowered too much will hurt performance quite a bit
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Old 07-17-2009, 10:23 AM   #7
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Quote:
Originally Posted by XtremeVette View Post
"sidestepping"...EXACTLY! I knew there was a term for it...just couldn't think of it...thanks man!

Bilstein Sports huh...what did you pay for em? Did you notice any change as far as harshness of your ride?
you could use new shocks. However don't be supprised if this happens again on the same section of road. I think the traction control may have kicked in when the tire hopped. Go around the same ramp and this time turn off the traction control.
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Old 07-17-2009, 10:30 AM   #8
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Quote:
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These three are the biggest factors.

Old tire and car lowered too much will hurt performance quite a bit
Tires are fairly new Kumho Ecsta SPT XRP Runflats. About 80% wear left on the fronts and 70% wear on the backs.

Car has not been altered at all from the stock suspension setup other then it has a C5-Z06 rear swaybar, the front sway was the same thickness bar as the C5Z (I looked up the code). It has not been lowered.
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Old 07-17-2009, 10:37 AM   #9
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Quote:
Originally Posted by Jims79 View Post
you could use new shocks. However don't be supprised if this happens again on the same section of road. I think the traction control may have kicked in when the tire hopped. Go around the same ramp and this time turn off the traction control.
Yes traction control did kick in....

Quote:
Go around the same ramp and this time turn off the traction control.


Wouldn't that be a bad idea? lol
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Old 07-17-2009, 10:47 AM   #10
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Yes traction control did kick in....



Wouldn't that be a bad idea? lol
Not at all. If you like to drive your vette hard and want more control over the car turn off the traction. Have you ever driven an older high performance car or sports car that didn't have traction control. That's whats driving is all about.
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Old 07-17-2009, 10:51 AM   #11
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Quote:
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Not at all. If you like to drive your vette hard and want more control over the car turn off the traction. Have you ever driven an older high performance car or sports car that didn't have traction control. That's whats driving is all about.
Well yeh...but I like my car and in this case I think the traction control did what it was suppose to and kept control over the situation. Had it not been on...Iam guessing the sidestepping might have been complimented by possible oversteer to correct the problem when steering may not have been needed at all. As you have mentioned...these cars are not your older high performance cars (if you want to call them that). Either way...it was all good. Just trying to see if I can get it to better keep the tires to the payment.
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Old 07-17-2009, 11:35 AM   #12
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Quote:
Originally Posted by XtremeVette View Post
Well yeh...but I like my car and in this case I think the traction control did what it was suppose to and kept control over the situation. Had it not been on...Iam guessing the sidestepping might have been complimented by possible oversteer to correct the problem when steering may not have been needed at all. As you have mentioned...these cars are not your older high performance cars (if you want to call them that). Either way...it was all good. Just trying to see if I can get it to better keep the tires to the payment.
ROGER THAT! I drive w/my traction control on at all times. Just saying it also may have caused the reaction to the hop..
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Old 07-17-2009, 11:40 AM   #13
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Run flats have VERY STIFF SIDEWALLS. yes that will contribute to wheel hop
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Old 07-17-2009, 11:49 AM   #14
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SHOCKS!!!! My 02 ZO6 did this BAD! I can scare the crap out of you!

I changed to C6 ZO6 shocks. Problem SOLVED! im 100% happy. Gene Culley has them new for $245 They fit like OEM and are a very good upgrade!!

Check out this post for more info!

http://forums.corvetteforum.com/c5-t...or-the-c5.html

www.gmpartshouse.com Call Gene!!

Bill
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Old 07-17-2009, 11:59 AM   #15
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rear tie rods going bad can cause this too. not sure how common the issue is on street-only cars, commmon problem with track cars and may cause similar behavior.

yeah 80k is a lot of mileage for shocks
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Old 07-17-2009, 12:39 PM   #16
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Quote:
Originally Posted by Bill Curlee View Post
SHOCKS!!!! My 02 ZO6 did this BAD! I can scare the crap out of you!

I changed to C6 ZO6 shocks. Problem SOLVED! im 100% happy. Gene Culley has them new for $245 They fit like OEM and are a very good upgrade!!

Check out this post for more info!

http://forums.corvetteforum.com/c5-t...or-the-c5.html

www.gmpartshouse.com Call Gene!!

Bill
Funny thing, I read that post about an hour before getting hits from this post! Thanks Bill, I was going to PM you to get your thoughts but you beat me to the punch! You don't think the C6Z06 shocks are too stiff do you?
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Old 07-17-2009, 04:29 PM   #17
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NO! There fine for me but of course,,,I own a ZO6 so my assseatOmeter is NOT that sensitive to a rougher ride. There a little more firm than the 02 Z shocks but nothing to complain about. I had F-45 shocks on my 98 so,,,I cant compare stock Coupe/vert shock to the Z shocks.
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Old 07-17-2009, 05:00 PM   #18
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Quote:
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Run flats have VERY STIFF SIDEWALLS. yes that will contribute to wheel hop
Thats the bulk of his solution right there....

Had the same deal on the way to the former AFR facility....long sweeping on ramp / bridge that had a big expansion joint in it.....first time I hit that thing kinda purposely pushing my car in the turn a bit (and enjoying some lateral G's), it scared the crap out of me.....car hopped a few inches over and I was afraid I might lose it at that speed. It stayed in the line again but the pucker factor was big....LOL

I took that same turn every day with the same results (truth be told going a little slower....LOL) until swapping out of the runcraps.....went to Nitto' RII's at the time and no step out whatsoever on the same road and the same approach speed I originally hit it at after creeping up experimenting. Just felt like a normal bump but it didnt upset the suspension at all.

Ditch the tires and dont buy another runflat.....you will be glad you did and wished you had done it sooner!

-Tony
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Old 07-17-2009, 05:06 PM   #19
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I agree the runflats are the biggest contributor to your handling problem!
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Old 07-17-2009, 06:37 PM   #20
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BTW, your car may not have actually caught air. When you go over a rise you and your car get lighter and that decreases the available traction. So if you were turning and right at the limit going up the rise, you will lose traction as you go over the peak and your rear will step out a bit.

But yeah, if you have runflats and bad shocks this will only exacerbate the problem. The runflats are a joke and are downright dangerous if you're trying to use your Vette they way it should be.
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Old 07-17-2009, 06:37 PM
 
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