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2004-2007 Cadillac CTS-V General Discussion Discussion, My Rx8 Had no wheel hop? in Cadillac CTS-V Series Forum - 2004 - 2007; ...
  1. #31
    Silver Baron's Avatar
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    Thumbs up Re: My Rx8 Had no wheel hop?

    Quote Originally Posted by miscreant
    I still forget to point out that the CTS-V features a Nivomat rear shock. For anyone who is familiar with Sachs'/Boge's Nivomats, they are not *that* great of a shock, and I *wonder* if the inherent "self-adjusting" nature of the Nivomat doesn't lead to some serious PLANTING problems.
    Finally, someone is making sense.

    After all that “IRS is more prone to wheel hop” or “high torque creates more wheel hop” nonsense.


    The culprit are our self adjusting rear shocks.



    It’s a simple but vicious cycle: car starts - weight shift to the rear - rear springs try to level car – become harder – loose traction – become softer - regain traction - get harder again - etc…



    I am pretty sure the new shocks are not self leveling or very differently valved. Now, did Cadillac know about it? Most likely, but for the better or worse, the self leveling feature was deemed more important than the ¼ mile launch capability.

  2. #32
    Cal
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    Re: My Rx8 Had no wheel hop?

    Looks like I will be one of the first (maybe the first on here) to install the FG2. I will give everyone a report once done. GM says they are intended for handling and not wheel hop but we can see if the stiffer shocks do anything.


    Incidentally, the car has independently mounted shocks & springs on the rear. The springs do not 'coil over' the shock. If anyone cares. Noticed it when putting new tires on.

  3. #33
    globed70 is offline Cadillac Owners Enthusiast
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    Re: My Rx8 Had no wheel hop?

    OK, I've sat on the sidelines and observed....

    1. The compromise IMHO is between handling, launch, AND ride. Do you really think that GM was going to put a Caddy on the road that rode like crap.... so they go for handling.

    2. I agree that the performance comparisons should have Erred on the conservative... 4.9 or 5.2s would not discourage most of us. I think GM was plain stupid for taking the best possible one off run.

    3. Wheel hop is present on plenty of cars, but to be honest, the V is worse... you would expect, in order of revs: 1. bogging the engine, 2. wheel hop, 3. spin. In the case of the V, spin is just not available as an option. And the hop sounds horrible.

    4. In 99% of all situations the hop does not come into play... but many buyers expect to be able to smoke the tires... and I don't think that is unfair to expect from 400 lb/ft torque.

    5. GMPD says the FG2 shocks weren't designed to deal with wheel hop... but it will be interesting to see if they help.

    6. The V does an AMAZING job of puting power to the ground in rain or shine, handles great, and I hope that buyers look beyond the occasional wheel hop and realize the merits of the V. As a former M5 owner, it is equivalent IMHO.

    7. Blaming torque for wheel hop is not really acceptable... in fact, a sudden delivery of torque should help spin the wheels. And there are plenty of torque monsters with IRS with lesser hop problems... think Viper or AMG.

    8. The M5 may have a bit less engine torque, but gear multiplication makes it equivalent when the tires meet the road.

    Take care, Dan.

  4. #34
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    Re: My Rx8 Had no wheel hop?

    My two cents:

    IRS is not the best setup for drag racing. If all you want to do is get the best launch go for a 4-link, a 9" - coil overs, etc. The CTS-V isn't designed for drag racing...IMHO. Or, check out the guys who go 325 in the 1/4 mile.

    Now, if you want to go road racing..........IRS rules.

  5. #35
    JEM
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    Re: My Rx8 Had no wheel hop?

    Quote Originally Posted by GNSCOTT
    Can't figure out the quote feature so please excuse.

    First what is the M5's torque curve? I'm sure it is alot smoother than the V's. Not a BMW expert in the least, but don't they rev higher and with the V being faster would leave me to beleive the V's torque comes on quicker.
    The M5's S62 engine's variable cam timing (60 crank degrees of movement, independently on both intake and exhaust) which gets it to 85% or so of peak torque by 2000RPM. It's almost fun to drive it around like a diesel sometimes, keeping the revs between 1500 and 2000, just 'cause you can...

    Factory redline is 7000RPM and there's not much to be gained by pushing it past that. It's actually a pretty mildly-tuned engine - for a 5-liter 32V V8 it's got the same valves (smaller than Nissan, etc. 32V V8s), same port sizes, same exhaust manifolds (a compromise to allow 'decking' the car on the standard 5-series production line at Dingolfing) as the 282HP M62TU from the '99-03 540i, X5, '99-02 740i, etc.

  6. #36
    Cal
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    Re: My Rx8 Had no wheel hop?

    I just figured out what IRS meant, I feel dumb for posting about the shock/spring layout now.


    Anyhoo...I will report my findings based on FG2 and Michelins, but I am not going for a package if the car doesn't need it to do what I want to do...road.

  7. #37
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    Re: My Rx8 Had no wheel hop?

    Personally, it kinda erks me that alot of people here want to blame ONE thing on the wheel hop problem.

    "No, blaming IRS is nonsense."

    "No, blaming Torque is nonsense."

    "No, blaming the shocks is nonsense."

    I for one do not think it is merely one thing at all.

    IRS IS, I say again, IRS *IS* prone to wheel hop, much more so that a solid rear axel setup, because one side of the suspension is not connected to the other.

    Torque is absolutely a player in the wheel hop equation. If you put a 150hp 4 cylinder in the CTS-V, would you still experience the same level of wheel hop? No way. When the Torque, or *twisting* starts, the tire begins to twist down, causing loading on the suspension which causes rebound. If that torque is so great that you have not started moving (just spinning the tires) and the suspension begins to load and unload (remember that the centrifugal force of the wheel spinning will amplify the loading and unloading of the suspension), you can get wheel hop (suspension bouncing), no matter WHAT suspension you have.

    The CTS-V sufferes from wheel hop because of the following problems, listed IMHO in order of effect:

    1) Torque
    2) IRS
    3) Shocks
    4) Runflats

    To try to blame only one is rediculous. To try to FIX only one, that makes sense. But my guess is with the lowend torque the V has, Wheel hop will ALWAYS be there at some level. I'd look at #3 and #4 to find the improvements/solutions.
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  8. #38
    globed70 is offline Cadillac Owners Enthusiast
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    Re: My Rx8 Had no wheel hop?

    Quote Originally Posted by miscreant

    The CTS-V sufferes from wheel hop because of the following problems, listed IMHO in order of effect:

    1) Torque
    2) IRS
    3) Shocks
    4) Runflats

    To try to blame only one is rediculous. To try to FIX only one, that makes sense. But my guess is with the lowend torque the V has, Wheel hop will ALWAYS be there at some level. I'd look at #3 and #4 to find the improvements/solutions.
    You can actually expand your list to include:

    5) Bushings
    6) Suspension geometry

    And agreed, it is no ONE thing...

  9. #39
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    Re: My Rx8 Had no wheel hop?

    I've been on the sidelines too, reading about the wheel-hop problem even before I pick up my V, and I've been asking myself, is this really a "problem" for me? Correct me if I'm wrong, but isn't this a problem only if someone is trying to beat 5.1 secs in 0-60? There's nothing wrong with that, don't get me wrong, but if I'm not laying rubber, is this a real problem for me?

    Thinking this is the case, I'm more concerned about the faulty oil temperature sensor if the so-called "flash" isn't able to correct the problem -- because I can see myself on a track pushing the tach and this might be enough to trigger that problem.

  10. #40
    GNSCOTT is offline Cadillac Owners Connoisseur
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    Re: My Rx8 Had no wheel hop?

    Thanks Jem. Always wondered what their numbers were


    as for this.... I agree that the performance comparisons should have Erred on the conservative... 4.9 or 5.2s would not discourage most of us. I think GM was plain stupid for taking the best possible one off run.

    Where did you get the information that caddy did this once? I was told that they were able to get to 4.8 multiple times and that they pulled a 12.9 a couple of times and multiple 13.0's. This was a post from a GM employee who was there when it was being tested. I'm sure those numbers could be duplicated by a good driver with many launches under his belt. Kinda hard to go by a magazine driver who has launched the car 10 times if he's lucky. This just keeps pushing me to get my car to the track.

  11. #41
    Cal
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    Re: My Rx8 Had no wheel hop?

    Not to thread-jack, but the oil temp problem seems to occur only on the FIRST hard driving lap(s) you put it through. After that, it goes away even through harder (and hotter outside temperature) sessions.


    I did 4 25-min (approx.) runs on a very technical road course. It binged through most of the first run, did not bing at all through 2-4 even when I got on the car HARD.

    Shrug.

    I'll ask again: anyone know of bushings for this beast? If the IRS is part of the problem then the FG2 kit may not help.

    AND TO REPORT:

    Michelin Pilot Sport XL = no apparent change in wheel hop. I cranked her to 4-5k rpm in first and eased off clutch... whump whump whump whump. It may help a bit, but definitely not a solution.

  12. #42
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    Re: My Rx8 Had no wheel hop?

    Quote Originally Posted by Cal
    Not to thread-jack, but the oil temp problem seems to occur only on the FIRST hard driving lap(s) you put it through. After that, it goes away even through harder (and hotter outside temperature) sessions.


    I did 4 25-min (approx.) runs on a very technical road course. It binged through most of the first run, did not bing at all through 2-4 even when I got on the car HARD.

    Shrug.

    I'll ask again: anyone know of bushings for this beast? If the IRS is part of the problem then the FG2 kit may not help.

    AND TO REPORT:

    Michelin Pilot Sport XL = no apparent change in wheel hop. I cranked her to 4-5k rpm in first and eased off clutch... whump whump whump whump. It may help a bit, but definitely not a solution.
    XL? Why did you get the XL? XL tires are VERY stiff on a vehicle under 4000lbs (not to mention you typically carry a higher psi as well). I'm not sure the XL tires would have been an effective sure anyway.
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  13. #43
    Cal
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    Re: My Rx8 Had no wheel hop?

    I have them around 32psi at the moment, still haven't taken anything out from Pocono. I got XL because the car is around 4k lbs. When I re-order I'll remember that, I couldn't find any solid details on whether to get XL so I got them due to the fact I knew the car was heavier.

    I got them for handling not as a solution for the wheel hop, but it's good to finally get a little info on them. They did remarkably at the track, so I'm not sure what to say in that respect.

    Note: I went to Michelin's site, Tire Rack, noone can tell me what the heck the difference is and what XL is actually FOR. The tires are sized for the car, I don't know too many SUVs that take a tire that size. If someone could find me an explanation that'd be great.

    Anyhow, if someone wants to try regular Pilot Sports be my guest. I think they are $200 cheaper than the XLs.

    These look fun, but not on Tire Rack.

    http://www.michelinman.com/catalog/t...tml?source=mid

    3rd edit:

    Has anyone tried slicks or racing (track) tires?

  14. #44
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    Re: My Rx8 Had no wheel hop?

    Are the XL's more for heavy vehicles like a SUV?

  15. #45
    JEM
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    Re: My Rx8 Had no wheel hop?

    Suspect you'd find the XL specced for the Benz S-class. Probably overkill for the CTS-V - it's not that heavy.

    Here's the XL rated ContiSportContact 2 Vmax if you plan to go 360kph: http://www.conti-online.com/generato...2_vmax_en.html

    There's a tire engineer's rule of thumb as to vehicle weight as a percentage of tire load rating for best performance, but I can't recall what it is...

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