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Car hopping after spring install.

This is a discussion on Car hopping after spring install. within the Suspension and Handling forums, part of the General Help category; I just put a set of eibach Prokit springs with Bilstein HD shocks on my 2000 WS6. I did it ...

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    Member DarrenWS6's Avatar
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    Car hopping after spring install.

    I just put a set of eibach Prokit springs with Bilstein HD shocks on my 2000 WS6. I did it in phases over 3 days. First I put the rear shocks on with stock springs late one night. Felt ok driving next day. Then I put the rear springs in with stock front suspension. The rear end hopped quite a bit going down a flat road. Perhaps I'm not used to lowering springs but I don't like how it felt. Now I have the front assemblies in and the car is completely lowered. It feels better but the back end still wiggles up and down going down the road, all speeds, in throttle or just coasting.

    I have 2 point subframe connectors awaiting installment along with an adjustable Panhard bar. Will the Panhard bar help with the wiggling? I know it aligns the rear end but I just don't feel that's the issue since it occurred after putting the rear springs in.

    I was expecting to not need adjustable LCA yet, but could this be the issue? Changing the ride height setting stress in the factory arms being too long?

    Google search renders too many random solutions so I thought it best to explain my exact situation. I wouldn't call this 'wheel hop' as I haven't tried a hard take off. This is just under normal conditions.
    2000 Trans Am WS.6 M6

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    Spaz is My Mentor SMWS6TA's Avatar
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    Changing the ride height also effects the pinon angle. Adjustable Torque Arm is the only way to re-align the pinon to the correct angle.

    Wheel hop issue - Are you using the stock shocks? With lowered aftermarket springs you're going to feel more of the road then you would with oem springs. Most lowered springs are much more stiffer which transmits road vibrations into the car. You'll think it's wheel hop but it's most likely just the road is not as smooth as you think.

    The pan hard bar just aligns the axle to the body to prevent side to side motion. As the suspension compresses it tries to keep it centered.

    LCA's and a aftermarket Torque along with a good set of shocks & springs deal with wheel hop on hard launching. The SFC's help in preventing body flex that our cars suffer from by the design of it being a uni-body. When you upgrade the suspension it stiffens the car so you'll feel more of the road.
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    Senior Member raynor139's Avatar
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    Like scott said sounds like you need an adjustable torque arm. On smooth roads mine still rides good but you can feel every small bump. If it's hopping around like you say the torque arm isn't at the correct angle.
    Mods - Lid, Skip Shift Eliminator, MGW shifter, UMI SFCs, Founders Lower Control Arms, Founders Panhard Bar, Founders Adj. Torque Arm, UMI Torque arm mount, MWC Drive shaft safety loop, KONI Yellows, Strano Springs, Strano Sway bars, UMI Upper and lower A Arms, 160 thermostat, TSP headers and TSP true duals Monster stage 2 clutch, racetronix fuel pump, Strange S60 rear axle and tune by Frost.

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    Spaz is My Mentor SMWS6TA's Avatar
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    Not to mention it's a piece of flimsy stamped steel at best.

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    We can measure the pinion angle, Darren. I have a digital level and we can see what things look like under there.

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    Member DarrenWS6's Avatar
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    Thanks for responses folks.

    Quote Originally Posted by SMWS6TA View Post
    Changing the ride height also effects the pinon angle. Adjustable Torque Arm is the only way to re-align the pinon to the correct angle.

    Wheel hop issue - Are you using the stock shocks? With lowered aftermarket springs you're going to feel more of the road then you would with oem springs. Most lowered springs are much more stiffer which transmits road vibrations into the car. You'll think it's wheel hop but it's most likely just the road is not as smooth as you think.

    The pan hard bar just aligns the axle to the body to prevent side to side motion. As the suspension compresses it tries to keep it centered.

    LCA's and a aftermarket Torque along with a good set of shocks & springs deal with wheel hop on hard launching. The SFC's help in preventing body flex that our cars suffer from by the design of it being a uni-body. When you upgrade the suspension it stiffens the car so you'll feel more of the road.
    Great. That's money I was hoping to not have to spend just yet.

    I'm not positive it is wheel hop. My understanding of wheel hop is the rear violently shaking under hard throttle. The back end of the car just bounces quite a bit. Up and down rebound motion. I know 5he new springs are firmer but the hopping/wiggling was not expected. It's not with the stock Decarbon rear shocks. I first put them in the car with OEM springs. Rode fine, a hair firmer. Then I put the rear prokit springs in and that is where the hopping came into play. The rubber osolators are in correct and the bottoms of the springs are firmly on the axle when the car is on the ground. If it really is the road not as smooth as imagined then I'm not too sure this lowered thing is for me haha. Or at least I should get the Strano springs.

    Thanks for the info I appreciate it.


    Quote Originally Posted by pajeff02 View Post
    We can measure the pinion angle, Darren. I have a digital level and we can see what things look like under there.
    Excellent, hopefully in a couple of weeks. Until then I'll go easy on it.

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    Member DarrenWS6's Avatar
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    I installed my adjustable Panhard bar Wednsday evening. Spent some time adjusting and centering it with the body. I believe I have it dialed in just right with measurements. Drove the car yesterday. I can feel the better control of the back end. I never really thought of how much the rear end can move around in these cars but I am very impressed how much more controlled the car feels.

    It doesn't hop as severely as it did before, but it still does. My research sums it up to this being an issue until I get the torque arm and possibly LCA.

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    I'll go on my own and say it has to do with those shocks are probably not valved correctly to work with the spring rate of the new lowering springs. The pinion angle being off is certainly a concern and will cause a misalignment of the yoke to the driveshaft under acceleration though. What you're describing is shock or spring related imo, or a combination of both.

    Do you know what the spring specs are compared to OEM?

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    Member DarrenWS6's Avatar
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    Quote Originally Posted by 35th-ANV-SS View Post
    I'll go on my own and say it has to do with those shocks are probably not valved correctly to work with the spring rate of the new lowering springs. The pinion angle being off is certainly a concern and will cause a misalignment of the yoke to the driveshaft under acceleration though. What you're describing is shock or spring related imo, or a combination of both.

    Do you know what the spring specs are compared to OEM?

    Sent from my SM-G900V using Tapatalk
    Not off hand. The issue did occur after the rear springs were installed though.

    The front is almost too low, I love the height and gap of the rear however. Looks perfect to me. I will also admit I hate how it rides. Went on a 50 mile ride yesterday with the girlfriend, we both hated it. I understand with lowering you will sacrifice some ride quality, but this makes me almost makes me hate driving the car. It is too firm. I may look into going back to stock for now for the drivetrain sakes and getting Strano springs later on along with doing things more properly and prepared.

    Here are a couple of photos.

    Before:


    After:




    Last edited by DarrenWS6; 07-05-2016 at 07:54 PM.

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    Moderator 35th-ANV-SS's Avatar
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    Front does look a little lower than what I'm used to seeing, but the rear looks perfect.

    Are the Bilstein shocks adjustable at all, or just the one setting?

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    Member DarrenWS6's Avatar
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    Quote Originally Posted by 35th-ANV-SS View Post
    Front does look a little lower than what I'm used to seeing, but the rear looks perfect.

    Are the Bilstein shocks adjustable at all, or just the one setting?

    Sent from my SM-G900V using Tapatalk
    As far as I know, there is zero adjustment to the Bilsteins.

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    I have a set of aluminum plates we can slip under the front mounts to raise you up just a touch. Need to check that pinion angle...

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    Member DarrenWS6's Avatar
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    Quote Originally Posted by pajeff02 View Post
    I have a set of aluminum plates we can slip under the front mounts to raise you up just a touch. Need to check that pinion angle...
    Spacer effect, I didn't even think of that. Good idea! Any evening good this week you thinking? Or next? I'll be busy this weekend so probably not good for me. Also anxious to do the SFC install. Let me know!

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    I have a car coming this evening and am keeping tomorrow open in case the weather is decent. Not sure about Friday evening yet.

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    Did you get any solution yet? FWIW I had stock springs and Koni shocks and that improved handling a LOT but was a nice ride. I recently put Strano springs on with the same Koni shocks. It is firmer than before, noticeably, but I am OK with it, as it's an autocross car. My wife rides in it so little that she says she doesn't notice that anything was changed, its always a firm ride for her. It's not 'bouncing' like you said. But I also did not even change my torque arm or lower control arms, but did add a Watts link. The right shocks help a lot, but if too stiff springs are paired with weak/soft shocks, it'll bounce around. Springs/shocks need to work together.

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    Moderator 35th-ANV-SS's Avatar
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    Get that adjustable torque arm in there and get that pinion angle corrected.

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    Member imprtkillr2810's Avatar
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    I installed Koni str-t shocks on mine with strano lowering springs, 3 point subframe connectors, and LCA relocation brackets. If you went lower the LCA relocation brackets will help out a ton with traction and its something that people forget about.



    Front:


    Rear:
    Last edited by imprtkillr2810; 08-05-2016 at 09:41 AM.

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    Member DarrenWS6's Avatar
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    Quote Originally Posted by SuperMacGuy View Post
    Did you get any solution yet? FWIW I had stock springs and Koni shocks and that improved handling a LOT but was a nice ride. I recently put Strano springs on with the same Koni shocks. It is firmer than before, noticeably, but I am OK with it, as it's an autocross car. My wife rides in it so little that she says she doesn't notice that anything was changed, its always a firm ride for her. It's not 'bouncing' like you said. But I also did not even change my torque arm or lower control arms, but did add a Watts link. The right shocks help a lot, but if too stiff springs are paired with weak/soft shocks, it'll bounce around. Springs/shocks need to work together.
    I haven't done anything yet but I am betting it is the torque arm issue. I am planning to order a UMI full length arm ( on-car adjustable ), relocation bracket to get it off the transmission, and a driveshaft safety loop. Probably in a few weeks. I also will grab adjustable lower control arms.
    pajeff02 likes this.

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    Looking forward to having the silver lady back on the lift... should be an easy install. I think I have a bolt kit for the torque arm that I did not have to use -- let me look for that.

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    Member DarrenWS6's Avatar
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    Slight update.

    So I broke the passenger rear bump-stop by bottoming out on a pothole a couple weekends ago. Research lead me to the Energy Suspension bump-stops for Jeeps are a replacement for our cars with some minor metal grinding. I bought them and installed them ( grinded off the tab, painted exposed steel matte black ), put it on the ground and took it for a drive. All of the hopping is all gone. The OE bump-stops were so long ( awkwardly long in fact ) that the whole time I had these springs in the car the rear end must have been touching the bump-stops, if not, at least a 1/4" or so away from contact. So this explains the ambilateral wiggling/hopping the car was giving me under normal driving conditions, and horribly under harder driving manners. The UMI Panhard bar I installed helped reduce the issue a little bit, which made me sum it all up to a bad pinion angle among other's suggestions.

    The pinion still needs set I know, I have a UMI full-length torque arm ( adjustable ), and a relocation bracket for it. Also am planning adjustable LCAs with relocation brackets. Car is going to have a lot of nice red UMI pieces under it before winter.
    Last edited by DarrenWS6; 10-06-2016 at 01:46 PM.
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