Planet 9

I hate how bad the wheel hop in my CS is. Just trying to take off even remotely quick results in wheel hop. I never had this in my 99' C2 and it's really irritating.

Is this a suspension issue? Suspension geometry issue? Is not having an LSD what's causing this? I've never had a car that did this so I hope there is a fix or solution to this.

Hmmmm..... I've never experienced any wheel hop. But I might be launching differently than you. Or maybe the tires have something to do with it. I have Michellin PS2s. How about you?

I remember reading in Car & Track that if they did a clutch drop from 4,000 RPMs they would get a good launch but lots of hop. Is this what you're doing? I've never dropped my clutch, and don't plan to either.

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Gator Bite
PCA Cayman Register Advocate

I've tried it a couple times and you get wheel hop with PS2's. I think the reason versus your C2 is there was a lot more weight on the rear tires in that car. These days I have no need for a fast launch, fast through the apex well that's another story.

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Nitto NT-01 on Stock 18's (track), 19' Sport Design (street),PSS9's,Pagid RS-19,GT3 Seats,GT3 brake ducts, GT3 front Control Arms, 6pt Harnesses,Heigo Rollbar + TC Design Harness Bar,Remus Catback,Softronic Flash,Rennline pedels,Sharkwerks/Safecraft Extinguisher

19" Carrera wheels with PS2's. I never drop the clutch at take-off. I would say I am trying to launch around 2,500-3,000 RPM with a quick clutch release.

Bridgestones - 'Hop' - I am Told........... From Low to High Revs................

As a 'Sad Fat Old Git.... Clutch Control, Solves All 'Take Off' Issues...

Learn Your Rubber.......... Enjoy...................

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Cheers Karel



'Power is Nothing - Without Control..........'

I've had that happen to me once in that RPM range. Launching at higher RPM's has prevented it from happening to me again.

Our stock suspensions are a compromise that does not include much concern about how the car behaves during drag strip launches.

Wheel hop is the result of the tire moving relative to the chassis and changing the toe angle. You are losing/gaining grip in a viscious cycle as the tread's attack angle changes. You can play with the throttle to limit wheel hop, but you are giving up putting as much power to the ground as you might otherwise be able to. (Ugly sentence nominee 2009)

LSD helps but eventually your wheels will hop without suspension changes that might make your car undesirable in other ways.

High RPM with LSD will lay down a nice strip of rubber and then hook up and go more smoothly. Imagine your tires are the clutch plate and the ground is...the other thing. LOL. The flywheel? I need more coffee.

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2007 Speed Yellow Cayman GT 2.7 (retired)
2008 Guards Red Cayman GT 3.4
"Carpe Cayman"

I've experienced axel hop on the street and the track. Both times starting from a stop and NOT dropping the clutch... rather a slightly harder clutch engagement and then dropping the hammer. The clutch would be fully engaged and heavy gas applied between 3k-4k rpm. I run PS2's on 19"'s and in both cases the PASM was ON and the Sport Chrono Sport Mode was ON. Can't seem to reproduce without Sport Mode OFF.

This is a strong clutch! LOL.

+1. Big time. When I cared about such things as 1/4 mile times & trap speeds Porsche always equalled axle hop, so this doesn't surpise me. Axle hop is so potentially damaging to your vehicle my advice is to avoid it at all costs. It can rip your drivetrain apart.

In the dry, get rolling and then nail it in 1st gear. If you want to nail it in the wet get an LSD or a TBD, because I understand even a base Boxster or Cayman may hop just by flooring the throttle in the wet from a rolling start in 1st gear.

Dave is right - there's a lot of design subtlety that goes into avoiding axle hop on a launch. I remember reading about GM altering the diameter of one of the rear axles on the ZR1 to avoid a resonance that was causing axle hop. In the old days we just put on a torque arm.

Why is it that when you mention wanting to "launch" or "take off quickly" everyone assumes you're trying to drag race or run the 1/4 mile? This is not the case and there is nothing wrong with trying to launch quickly off the line.

That being said I've done everything I can do to minimize the axle hop when wanting to launch the car quickly but it seems that just leaving quickly at around 1500 RPM and then getting on the gas is the only way to do it smoothly. This isn't something I do a lot of but it is something I've been irritated with for some time.

Does anyone know if having wider rubber in the back would help? My 911 had 285's in the rear so maybe having the extra meat back there for added grip would help?

I launch my car hard and fast, but my style doesn't result in any wheel hop.

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Gator Bite
PCA Cayman Register Advocate

Nick:

285s would let you accelerate faster without any spin, but if you get spin, it'll still do the axel tramp thing...only harder with potentially more damage to your half-shafts and/or transaxle.

I smell opportunity here...Traction bars for Caymans!!! Maybe start a drag racing class for them? I wonder how they'll run on nitrous?

LOL.....

Sorry for the misunderstanding. I got carried away, fondly remembering running my first sub-13sec quarter mile. But back to business...

Anything that changes the way the wheel/tire/suspension/axles respond will alter the situation. More tread might change the onset, but could increase the amplitude of the hop. Stiffer adjustable shocks with coilovers would be my first thought, because you could experiment with so many factors.

Odd that your C2 didn't hop. The auto magazines complain a lot about RWD Porsches, and I've witnessed 993-997s hopping on the street.

AWD is the real ticket for a fast start.

I doubt that would solve the problem - as sixisenuff said, it would ultimately be harder on the hardware. Another thing - more rubber in the back would do is exacerbate the understeer already dialed-into the cars from the factory.

brad

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22-year PCA Member
PCA DE Instructor

Fastest cure is to increase tire pressure. It is my experience that root cause is the aft part of the tire contact patch giving up grip before the front of the tire patch. That forward motion of the reaction point causes the torque vector to move in front of the axle which results in an upward force component that compresses the suspension, reduces the load on the tire which spins a little bit until the suspension shoves it back down with enough force to re-adhere to the surface. An LSD will help by limiting the amount of tire spin between adhesions, but will not totally prevent - even a full lock diff. And when you get both tires hopping together, you really know it. And alternating hop will rattle your teeth. I have had wheel hop especially on semi-dry surfaces with both PS2's and Pirelli PZeros 19's. The characterization was not different with the 2 tires. At AX school, I was hopping at 36psi but had no hop at 40 psi. I have also not experienced wheel hop when spinning a tire going around a sharp turn, probably because the tire is unloaded and the contact patch is small from front to back. I think the bottom line is that our suspension is designed for track work, not hole performance. I know darn well that first gear was not ratioed for dragging.

You can see the precursor to wheel hop with a big, low pressure slicks under really hard acceleration. Sometimes you can see the sidewall deformation wave going forward from the bottom of the rim to near the tire tread face. I'm sure that in slow motion during a hop, you would see the deformation wave move toward vertical as the tire slips and the axle rises and then reform and slant forward as the tire re-adheres. It is also a function of suspension components and geometry. Back in the day (late 60's, early 70's), we used 50/50 shocks as stiff as we could buy them to prevent hop. I used to joke that I was going to replace my shocks with iron rods and let the hysteresis in the bushings supply the damping. I also would mount my shocks leading the rear axle and that seemed to help. It probably helped less than driver performance factors, but I felt like I was doing something positive.

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Kenny

2006 Arctic Silver CS 6M, PASM, Sport Chrono,, short shifter, 19" wheels, Pirrelli tires, Milltek Catbback, Softronic SRP and 4.2 Flash.

Hey Kenny,

Fascinating explanation of hop - thanks! Please keep sharing the wisdom.

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2007 Cayman S, Arctic Silver
Gone but not forgotten: 1980 911SC
PCA San Diego Region

I have had hop issues from the beginning and this is what I have found so far:

1. The amount of hop depends on how warm your tyres are. Cold tyres make it really bad and is one factor you have some small control over.

2. Sure you can do a wimpy takeoff and avoid it.

3. You can dump the clutch and still get it. But if it does it best to back off for reasons already mentioned.

4. My 295mm R spec tyres on the rear did not make it go away.

5. I can do some "number 11s' where both wheels spin in balance and you may or may not still get hop. ie LSD would not have helped in that case.

6. Another Cayman S owner with coilovers gets hop and it seems the problem is more so than mine.

7. The road surface makes a big difference to the amount of hop.

8. I have had some (small) hop powering through corners.

Yes, it would be good to get rid of this hop. I can be pretty bad if you let it.
In many sporting events we have a standing start and have seen the 997s' do it as well.
Anyone with PASM care to comment

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2010 Cayman S, special build.

A Diff, weather LSD or TBD solves most of the problems relating to wheel hop/tramp as does solid gearbox mounts...

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Email: allan@motordrive.com
Group Buys: http://motordrive.com/acatalog/Cayma...roup_Buys.html

Tire sidewall plays a role in this too. If you're sitting on 19s, that may be part of the problem. My drag racing buddy advises that more sidewall allows the tire to absorb some of that bounce and dampens the wheel hop.