The wheel hop in my stock 2012 GT/Brembo is killing me. Been doing quite a bit of searching through old threads (2006-2008 or so) and came across some people mentioning that the stock GT500 lower control arms cured a bit of their wheel hop problems. But I haven't seen any recent threads on this and was wondering if the 2011+ stock GT LCAs differ from the GT500 LCAs?

Alternatively, any recommendations for aftermarket LCAs that don't create more NVH? Even most of the aftermarket LCAs with poly bushings seem to create more noise based on the threads I found...

 

Springs and high quality dampers will cure most of your wheel hop ailments as well. People with Steeda Sport springs and Koni yellow dampers have reported a firmer ride, but actually rides better over bumps.

But otherwise yeah, any aftermarket LCA that will fix wheel hop will slightly increase nvh...that's just the name of the game. Worth it IMHO.

 

I figured the same, but doesn't a drop require either adjustable LCAs or relocation brackets?

 

A mild drop - about an inch or only a little more - does not really require you to do anything else in most cases. Your 'launch' geometry actually improves slightly over what it is at the stock height and I suspect that this is more the reason for mild lowering improving 'hop' situations than the springs being stiffer. At this small amount of drop, the hole locations on the available relo brackets may actually be a little too aggressive for overall driving.

In a little more detail, if you're mostly a straight-line enthusiast and don't ever take corners particularly hard you can probably live with them just fine. But if you're at all into hard cornering, lowering the axle side LCA pivots too far will tend to make the car's handling "loose" and you won't be able to put the power down quite as soon coming off the corners. Maybe think about how you drive through an Interstate on-ramp with tight turns here.


Better dampers will help, but in order for the shocks to get involved with resisting hop - the hop has to already be happening.


You'd use adjustable LCAs to correct pinion angle or axle squareness issues once you know that you have them, and since these can be added separately from springs/shocks there is no need to rush into this.

Poly will squeak (eventually) and has a separate downside if you ever corner with much enthusiasm. This can be 'crutched' with some careful bushing modification that probably reduces their life, though poly bushings should really be considered 'wear parts' anyway. Rod ends and most sphericals tend to eventually rattle or possibly clunk, so I guess the price of improving this aspect of performance still comes down to more maintenance being required.


Norm

 

I disagree that your launch geometry improves. Your geometry does change, and it changes in such a way that you don't get the weight transfer you used to which results in more wheel spin.

Lowering the car and the resulting rear suspension geometry and reduction in weight transfer if you have stock control arms results in a reduction of the loads on the rear suspension that produce the suspension bushing deflection associated with wheel hop, hence wheel hop tends to go away and you are just left with wheel spin. If you dont have a lot of horsepower and/or a sticky tire this could result in a slight traction improvement, but in most cases it will not.

The underlying cause of wheel hop is really the rear trailing arms and their soft bushings. Whenever I get a customer on the phone trying to resolve a wheel hop issue I immediately suggest a set of rear lower arms. For most people this alone will take care of 90 to 100% of their wheel hop issues.

If there is still some wheel hop left then we get into changing the upper 3rd link to reduce the bushing deflection that is left, plus you can dial in pinion angle while you are at it.

Also in our experience you can actually improve corner exit by relocating the lower arm in a lowered application, but only if you relocate it back to a location that is basically the original stock location, but not lower than stock. If you take it past the stock location (lower it too far) then the handling does suffer as you describe, in addition if you take it too far you can introduce wheel hop under severe braking. Not a good thing at all.

 

LCA replacement generally is the first line of action, it's a relatively simple modification and does not have to involve anything else, and you won't get any argument from me with respect to the downsides of OE bushing compliance. Normally I even suggest it first, but since OP seems to be somewhat "on the fence" with regard to this option, I thought I'd wait for more information.

I don't mind buying or recommending parts once I'm comfortable enough that they're an appropriate solution for the situation.


If you plot antisquat against ride height the curve bottoms out at just over 1" lowering and then rises again. What I'd take this to mean is that the initial squatting of a 1" lowered car - that you're going to get anyway - starts improving the A/S from the get-go rather than throwing some of it away first as what happens with a stock ride height car. The differences aren't huge, I get the A/S to be just over 32% dropping to just under 30% in the first inch of squat with a stock ride height car, and 29% improving to just under 31% in the first inch of squat at 1" drop. But I think you'd rather the A/S to be increasing slightly in bump as a sort of stabilizing mechanism with respect to the squat motion itself. This is the effect I was getting at, which by itself should have some minor effect on the hop.

I realize that a lower CG height means that there will be slightly less rearward load transfer. However, the actual change in terms of vertical tire loading is only a few lbs, less than 35 lbs per g of forward acceleration at a 1" drop if my quickie math is anywhere near right, or about a 1% effect. Kind of on the same order of magnitude as the difference between 30% and 32% A/S, I'd think.

I think we're mostly on the same page as far as the handling side benefits of LCA relocation goes, just that we're at different places with respect to identifying if/where the relocating bracket details would provide benefit. I suspect that for rear axle roll steer purposes at only a 1" lower ride height you'd end up with the new relo bracket holes pretty close to the OE holes without a whole lot of metal left between them.


Norm

 

Thanks for the great info in this thread. I am on the fence about lowering the car, since I barely get up my driveway without scraping (I have to take an extreme angle, and if I mess up, I will hear minor scraping).

I suspect the stock GT500 LCAs won't make that much of a difference vs. stock GT, so I'll probably look around a bit more for aftermarket LCAs. Steeda chromoly ones look nice, but have heard contradicting reports of NVH increase.

 

Ok, I'm not a suspension expert like Norm or some of others on here. But I had the hop, and hated it (my '08 GT Must.) I tried first the LCA's - I got some J&M poly/poly ones (chose J&M because of the 3-piece poly bushings they use, which threoretically allow the bushings to sort of swivell some, which allows the rear axle to properly articulate-an issue with most poly/poly lCA's) well that reduced the hop quite a bit but when I did still get it, it seemed even more violent due to stiffer bushing material.
I then tried UMI poly/roto-joint LCA's. these did not recuce the hop more, and they also added more ride hashness over bumpy roads.
So I replaced the UCA with a poly one (J&M again) , went back to my J&M LCA's as well and now NVH is near stock, and all wheel-hop is gone !
So try geeting you some LCA's first and for the street get poly/poly. I think probably the J&M or the Steeda. Then get a poly UCA if that does not cure it all.

 

The GT500 pieces probably won't eliminate a severe case of hop, although they'd probably delay the onset of it a bit. Follow the best parts of Hoss's experience (and what's more or less the conventional wisdom) and first see if the LCAs alone are enough. Go straight to the UCA swap if they aren't. Sneak up on the solution, and when you've got one, stop.

Plain, unmodified poly bushings in rear control arms will increase NVH, but to break it down a little finer may help the decision process some.

Noise will mostly be the squeaking that most poly bushings will eventually develop, and sometimes a mismatch between the fasteners and the factory chassis holes is to blame for a clunk. There are perhaps a couple of user mods that can reduce or nearly eliminate the N.

Vibration will be more along the line of more road texture being transmitted into the chassis. Kind of like running a little too much tire pressure or driving on roads that used more of the slightly larger gravel sizes. The 'V' is there, but in another car with quite a bit of poly in the suspension I've never found this to be particularly intrusive.

Harshness is more from hitting larger pavement defects like cracks, patches, and potholes. Not much you can do about this except try not to hit them.


On edit - if you're much into hard cornering (or autocross or open-tracking) poly bushings may not be suitable from an understeer/oversteer handling balance perspective. They will shift more of the lateral load transfer rearward, which tends to make the handling "looser". (You'll likely hear "lateral weight transfer", which isn't exactly true except for fluids and other loose things that slosh, rattle, or bounce around in their containers.)


Norm

 

I would certainly expect each impact to be transmitted much more noticeably once you do manage to get a hop going. Whether the hop is in fact more violent comes down to whether or not more energy gets stored in and released from the two UCA bushings alone than from all six rear axle trailing arm bushings. I don't know the answer to that one, and it gets further muddied by however much energy gets stored/released in the motor mounts.


Norm