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Discussion Starter · #1 · (Edited)
Just installed the BMR trailing arms to get rid if that damn wheel hop but a hole shot proved BMR wrong. Still have that damn hop. Any suggestions?
 

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I would also suggest the upper inner control arm bushing... I feel that is the biggest culprit.

One of the biggest reasons I think that is looking at the videos made of our stock rear suspension in action.

Here is one video that BMR put together of the stock 2010 Camaro rear suspension movement. The biggest deflections and movements all seem to be coming from the upper control arm.

But I agree that this complicated problem will most likely take multiple parts and tries at different combinations to completely eliminate

 

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Discussion Starter · #5 ·
Thanks all. Spoke to the guys at BMR--huge help. One of the biggest issues (as embarrassed as I am to say) is that I am still running stock tires. Also suggested the toe links and cradle bushings. Gonna try tires, then toe links and bushings.
 

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There is no one single mod that will cure wheel hop. Every car need cradle bushings. Add toe links and trailing arms, and it cures most vehicles. The more power you make, the more mods it will require to control the hop
 

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There is no one single mod that will cure wheel hop. Every car need cradle bushings. Add toe links and trailing arms, and it cures most vehicles. The more power you make, the more mods it will require to control the hop
This is main thing I try to convey to people when I talk to people about wheel hop. Wheel hop is very unique issue and there is no one magical part that takes care of the wheel hop issues these cars so nototriously have. Different cars take different parts depending on power level, transmission type, tires, road conditions, weather conditions, etc, etc. Due to this I really like to attack the wheel hop in stages to keep the parts and cost to a minimum. I generally recommend trailing arms and outer trailing arm bushings as the first stage because they are very affordable, the install isn't too bad, and they generally make a decent difference when it comes to wheel hop. If the trailing arms and outer trailing arm bushings don't do the trick I like to move on to the toe rods and rear cradle bushing kit because the rear cradle has to be lowered to install these parts so it is ideal to do them together. Axles will also help out with wheel hop but the price of them can be a hard pill to swallow so most of the guys we deal with hold off on them. Basically anything you can do to control movement in the rear end/rear cradle/rear suspension will help with the wheel hop.

If anyone is having wheel hop issues and would like to go over what they can do to fix the issue give me a call here at the shop and I would be more than happy to help you out.

Kyle
 

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As far as wheel hop goes there are much more important bushings/parts to worry about than that upper control arm inner bushing. Now I am not saying it isn't worth changing out because anytime you can get rid of unwanted movement you are going in the right direction but there are definitely things that should be done prior to worrying that bushing.



We are actually designing up a whole new part for that upper control arm that utulizes delrin bushings and gets rid of all movement in that mounting point. Not so much with the G8s but the Camaro guys making big power (800hp+) were requesting that we make something for them that worked better than the poly-urethane bushings at controlling the movement. I attached a picture of what we came with for them. For most customers the poly-urethane upper control arm inner bushing is more than sufficent.
 

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That piece looks nice..

Will it fit the G8?
How much?

The reason I am fixated on this bushing is that during autocross I am able the deflect my stock UCA bushing enough to cause tire contact at the front of my wheel arches (when running wider sticky tires).
 

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We haven't released pricing yet so I am not exactly sure what they are going to sell for. These will fit both the G8 and the Camaros so you should be good. This piece will definitely help with control the movement of the wheel/tire but I am not sure if it would completely fix it because the outer trailing arm bushing and toe rod also help control that movement you are having also. Do you have any kind of suspension work done?
 

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I started with your Sub-frame mount inserts, and after installing my choices of King HD SL springs and Bilstein shocks, I have been working on sorting out the rest.

I am looking at options that allow the controlled two-axis movement needed and I am not a fan of polyurethane bushings - no 2-axis movement and deforming/flow issues when pushed hard. For the toe rods - I am thinking about the GM 1LE/ZL1 part 22845487 - the factory style spherical bushings should be a good upgrade..

The trailing arm outer bushing is a hard one. I could go with your trailing arm with the spherical inner bushing but that still leaves the outer as stock or poly..
 

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I started with your Sub-frame mount inserts, and after installing my choices of King HD SL springs and Bilstein shocks, I have been working on sorting out the rest.

I am looking at options that allow the controlled two-axis movement needed and I am not a fan of polyurethane bushings - no 2-axis movement and deforming/flow issues when pushed hard. For the toe rods - I am thinking about the GM 1LE/ZL1 part 22845487 - the factory style spherical bushings should be a good upgrade..

The trailing arm outer bushing is a hard one. I could go with your trailing arm with the spherical inner bushing but that still leaves the outer as stock or poly..
The rose joints in the ZL1 toe rods are definitely an upgrade but the problem is that the body of the toe rods is still manufactured using stamped steel and is still prone to deflection under heavy loads.

As far as I know there isn't another option besides the poly-urethane bushings for the outer trailing arm bushings so you are kind of stuck there. I know that the factory outer trailing arm bushing allows a good bit of movement and changing it out is one of the keys to controlling movement in the rear. Changing that bushing alone helps out a good bit with wheel hop. We actually machine the spindles and install a spherical bearing in that mounting point with our new Camaro drag race brake/suspension kit but it isn't something that we offer on it's own due to the machining that needs to be done.
 

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An old post but I really must comment on the issues raised in several posts above. The geometry of the rear suspension is really an upper "wishbone" and a lower similar wishbone. The main problem is that these upper and lower arms do NOT pivot parallel to the car centreline. They pivot at an angle to the centreline hence are called semi trailing arms. Effectively the wheel will toe out as the suspension compresses. The tricky bit is that the upper L arm, effectively a wishbone, has a different trailing arm angle than the lower wishbone. This means that the spindle(knuckle) rotates as the spring compresses. The knuckle moves forward a bit and importantly the top part moves forward slightly less than the lower part. Hence the BMR video of a Camaro driving down a road looks as though there is massive rotation about the lower control arm joint. Reality is that the rotation is simply happening due to the semi trailing arm geometry mismatch top compared to lower arms.

Given that the knuckle moves forward ( about 12 mm) as the spring compresses, because the toe arm and the trailing arms are bolted to a cradle, it must cause the bushes to squish up, or the arms themselves must rotate slightly in torsion. That is why GM makes both arms weaker in one direction, to allow for the geometry change that must have twist either in the arm, or in the joints. Making both stiff is asking for trouble.

If solid, or stiff joints are used in the knuckle at the trailing arm, as BMR suggest for their dedicated drag car, than the knuckle cannot move to allow toe adjustment. For the toe arm to make any difference to the wheel, it must lengthen or shorten its length. The knuckle must then rotate slightly, and this happens about the control arm spherical joint. So if there is a rigid joint at the trailing arm in the knuckle, then the knuckle is stopped from making any toe change.

A similar distortion happens if stiff poly is used at all of these arm locations. The geometry dictates that there must be movement somewhere to allow toe change. The other very important geometry issue is that the lower arms, effectively a wishbone, pivots about a plane formed by connecting the midpoints of the inner joints. This plane is NOT parallel to the bolts at these inner joints. The pivot plane is at a considerable angle to these bolts. This means that as the wishbone rises or falls, it MUST deform the bushes, or else it will freeze up. Poly will take deformation for awhile, but not forever. Eventually it gives up and forms an oval shape. Rubber bushes will deform for a very long time, but their downside is that they allow movement, as indeed they must to obey the geometry.

Using spherical joints at the inner joints satisfies the geometry issue. However there must be at least one deformation joint at the knuckle to allow for toe adjustment. The issue of the twist in the toe arms and trailing arms due to the whole wheel moving forward due to the semi trailing arm geometry is satisfied if inner joints are spherical joints as the pivot plane is not governed by the bolt directions. The arms simply rotate nicely over their spherical ball.

So I take issue with the use of high duro poly at suspension joints. Poly is not like rubber and cannot take deformation for long before becoming oval. Poly joints are designed to rotate perpendicular to the arms, in the direction of the bolts through them. Once the arms pivot at an angle, you are on borrowed time before ovality becomes an issue. Seems good initially, but poly fails eventually.

All this means that the outer trailing arm joint should have some flexibility in it for toe change to occur. The inner joints would be great if spherical joints were used, but the downside of noise may be an issue. In Australia, exposed rod ends are not legal for road use due to rapid wear if dirt falls on the joint. Legal spherical joints need to have a rubber boot. The camaro lt1 toe arms, part number 22845487 have spherical joints, and the arms themselves are the same size to allow for torsion. However, if spherical joints are used, there is not a need to have twist in the steel arm.... I guess they just wanted to save money. Using these LT1 arms, at $70 each, seems a bargain.

There does not seem a way to have a decent outer trailing arm joint, but I would think a stiff rubber joint would be the best option, certainly better than poly. Wheel hop, we call it tramp over here, remains the biggest deficiency in this G8/VE/VF platform. I note that firms claiming success in curing the hop never mention the behaviour in wet weather. Hop is way more prevent in wet roads due to lower adhesion limits, and is the only true way to judge if the issue has been fixed properly. No wheel spin = no hop. Hence once you have traction it is not an issue. However, wet weather will soon determine if the suspension mods actually do anything. I find it frustrating that firms claim success in curing hop, but when pressed, all fail to explain why their "cure" still hops in that oscillating time between adhesion and wheel spin.

As a point of interest, the latest HSV GenF, that uses the G8/VE platform, uses the ZL1 engine and the ZL1 rear suspension. 4 bolts is all it takes to fit the rear cradle. It has the big/ small axles, the spherical joint toe arms, the spherical joint in the knuckle for the lower and top control arms too. It uses the rubber outer trailing arm joint, as per the above explanation. And it wheel hops too!!! The solution offered to hop, is the same as for the ZL1, and that is to use electronics to stop wheel spin, hence no opportunity for stored energy to release. The electronic throttle is closed down to maintain traction. BMW, and Mercedes do the same thing as none so far can come up with a mechanical solution to IRS hop. Check out hopnot.net for a better solution that seems to work for SRTs, in the wet as well.
 

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I have trailing bmr trailing arms and diff bushings. I need to get some cash for them. But no wheel hop here after the trailing arms and diff bushings
 

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Aussie, you bring up some interesting points about wheel hop and suspension geometry....some I agree with....some I don't. The good thing is that we are all entitled to our own viewpoints on the subject, and I certainly do appreciate the fact that you shared yours. FWIW, here is our viewpoint on wheelhop (as paraphrased from Chase at Apex Motorsports)....

Very simply put, wheel hop is just a rapid and repeated loss and recovery of traction. When your car begins to accelerate various bushings and suspension/chassis components in the rear of the car flex. Under normal driving conditions this flexing is negligible, but when the car is launched aggressively the deflection causes significant toe changes which reduces the proper contact patch of the rear tires. This leads to a reduction in traction and momentary wheel slippage which alleviates the toe changes and allows the rear tires to regrip. The vicious cycle then continues as the suddenly improved traction again results in flexing thus causing toe changes and leading to wheel slippage.

Getting rid of wheel hop is pretty straightforward for most 5th Gen Camaro and G8 owners. In our experience, by upgrading the components known to be responsible for the deflection with stronger/stiffer aftermarket units you will lock the rear suspension geometry in place and significantly improve traction and performance. The top components you will want to focus on are:

1) Rear Trailing Arms and Outer Trailing Arm Bushings - In many cases, upgrading to a stronger trailing arm and stiffer polyurethane outer trailing arm bushing is all it takes to resolve wheel hop issues on the average bolt-on car. The stronger rigid arm eliminates the deflection found in the thin stamped steel OEM arms, and the poly bushings reduces the flexing at the connection points under load. Spherical bearings on the inner connection point will function better, especially for high HP cars, but usually at the cost of increased NVH (noise, vibration, harshness). Here is a good thread about our available Trailing Arms.... http://www.g8board.com/forums/showthread.php?t=169657

2) Rear cradle bushings- The rear cradle is the structural member that the entire rear suspension and drivetrain are built on. It is essentially the foundation of the rear of your car. You can use polyurethane bushing "inserts" or a full bushing replacement to limit the movement of the rear cradle. The full bushing replacements function better than the inserts, but it is a much bigger job to replace them.

3) Toe rods- While the rear trailing arms are being installed it is a great opportunity to also upgrade the toe rods. Toe rods are responsible for maintaining toes settings of the rear wheels. Replacing the stock stamped steel rods and mushy rubber bushings with a stronger unit with polyurethane bushings or spherical rod ends further reduce flexing and improve grip, launch stability, and braking performance. Here's a good thread on our available toe rods....http://www.g8board.com/forums/showthread.php?t=165194

Two other components you might also want to consider, especially if you like hitting the 1/4 mile, are:

4) Inner rear upper control arm bushings - When launching and shifting aggressively these bushings have a lot of leverage placed on them. Because of that, the soft stock bushings flex severely permitting the rear spindles to counter rotate. By upgrading these bushings you will further decrease movement of the rear wheels and have more consistent and predictable load transmission to the rear tires. We highly recommend the BK039. It's a good idea to change these when upgrading the cradle bushings....a lot of overlapping labor.

5) Rear differential bushings - These bushings reduce movement of the differential contributing to an overall reduction in drivetrain deflection. You have to be cautious when considering which rear differential bushings to use. The harder you go the more likely you are to see increased NVH (noise, vibration, harshness) direct from the rear end. For those who have enough HP to justify upgrading the differential bushings, we recommend the BK024 Pro-Version bushings.

When available, we typically recommend the use of SuperPro Bushings for our G8 customers. They have a LIFETIME warranty on all their bushings, which is a direct reflection of their superb quality and performance.
 

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I am running a complete Zeta II Camaro cradle with BMR full subframe bushings and diff bushings. Also using BC coil-overs. The rest is stock low-mileage GM parts. I have no wheel hop - spinning, hooking, wet, or dry. I will upgrade to more BMR parts for strength and longevity as the budget allows, but for now it works great.
 
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