Genesis Rear end issues

[Shagglestein]

I'm hoping someone will be able to shed some light on an issue I've been having with my 2010 Genesis coupe. I bought the car about four weeks ago, a little while after buying it I started to notice that after speeds of 50 Mph and higher and more so the faster I go the car will sway side to side in the rear when letting completing off the gas pedal. I've brought the car to my local mechanic who has tried every adjustment he can think of to make it drive properly with no avail. Today I brought it to the Hyundai dealership near me and they're leaning on it being a issue with the suspension upgrades which was something my local mechanic has stated as well, however both were not able to say for certain that setting everything back to stock will solve the issue.

Adjustments made currently.
- Suspension made as stiff as possible
-Suspension made as soft as possible
- Checked for play in every component in the rear end as well as the engine, everything was tight.
- Sway bars were in good shape including the bushings.
- Had a alignment done on the car, with different adjustments being made.
- The dealership verified that they don't believe the issue to be attributed to the rear differential.

Currently the dealership is quoting the cost of setting everything back to stock with the hopes that that will fix the issue.

I wanted to see if anyone has had similar experiences with an aftermarket suspension, in the case I believe that the coilovers are the only after market piece, other than the rear tires which are an inch taller but I should know more in a couple hours.

Any help or suggestions would be appreciated.

 

[TinsleyC]

That's a tough one. I have zero experience with custom suspension, but since the car was altered there's no telling what all was done. Taking it back to stock is about all you can do. Hopefully there's not something else wrong with the car, like the drive train.

That's a risk you run when buying a modified vehicle. Maybe the seller can help explain what do was done. Good luck with it.

 

[Roc 5.0]

Though I have a 5.0R sedan, this maybe something to check out. Not even sure your coupe has this part: Rear Suspension Lateral Arm. My Gen slowly developed a rear end sway that became very intrusive and also developed a high speed(120+) hood vibration. 3 Dealers could not find it and blamed my various suspension upgrades: strut brace, front and rear suspension braces, etc. One alinement guy who, on the side designs and installs corvette suspension mods for street machines, looked at it and after much crowbar moves said it was that rear arm( drivers side). Only had less than 1/4" movement! Replaced it and that was it! A simple $48 part.

 

[Vortex951]

I'm hoping someone will be able to shed some light on an issue I've been having with my 2010 Genesis coupe. I bought the car about four weeks ago, a little while after buying it I started to notice that after speeds of 50 Mph and higher and more so the faster I go the car will sway side to side in the rear when letting completing off the gas pedal. I've brought the car to my local mechanic who has tried every adjustment he can think of to make it drive properly with no avail. Today I brought it to the Hyundai dealership near me and they're leaning on it being a issue with the suspension upgrades which was something my local mechanic has stated as well, however both were not able to say for certain that setting everything back to stock will solve the issue.

Adjustments made currently.
- Suspension made as stiff as possible
-Suspension made as soft as possible
- Checked for play in every component in the rear end as well as the engine, everything was tight.
- Sway bars were in good shape including the bushings.
- Had a alignment done on the car, with different adjustments being made.
- The dealership verified that they don't believe the issue to be attributed to the rear differential.

Currently the dealership is quoting the cost of setting everything back to stock with the hopes that that will fix the issue.

I wanted to see if anyone has had similar experiences with an aftermarket suspension, in the case I believe that the coilovers are the only after market piece, other than the rear tires which are an inch taller but I should know more in a couple hours.

Any help or suggestions would be appreciated.

Just seeing this thread. Out of curiosity what brand and model are the rear tires ?

 

[Roc 5.0]

I wrote to you about this. See above. Did you ever have it checked out? Rear Lateral Suspension Arm. Maybe your coupe doesn't have that design, but problem is similar..

 

[MYR]

I had the exact same rear-end sway issue on my Genesis Coupe at highway speeds (50+ mph), especially when lifting completely off the throttle — the rear would feel light and twitch side to side. After a lot of experimenting, here’s what finally fixed it for me:

Switched to good quality all-season tires instead of summer/performance tires. This gave me consistent grip in both dry and wet weather and reduced the “snap” feeling when letting off the gas.

Changed wheel setup to 17-inch OEM-spec size:

Rims: 17×7.0 or 17×7.5 inches

Bolt pattern: 5×114.3 mm

Center bore: 67.1 mm

Offset: +35 to +42 mm works perfectly without rubbing


Tires: 225/55R17 or 235/50R17 (both fit nicely and maintain proper rolling diameter). This size provides a slightly taller sidewall compared to some aftermarket low-profile setups, which improves straight-line stability and comfort.

Set tire pressure to 27–28 psi (rear). Slightly lower pressure than aggressive performance setups improves road contact and stability at higher speeds.

Added 40–50 kg (90–110 lbs) of weight directly over the rear axle — for example, sandbags or securely mounted weight in the trunk. This extra rear bias really helps RWD cars like the Genesis Coupe feel more planted, especially on wet roads.


After doing all of this, the swaying and instability completely disappeared — both in rain and dry conditions. The car now tracks straight and feels stable at high speed, even with aftermarket coilovers. Honestly, I’d recommend trying this before spending a big amount reverting everything back to stock.


---

Summary of Wheel/Tire Specs Used:

Rim: 17×7.0 or 17×7.5, 5×114.3, 67.1 mm center bore, +35 to +42 offset

Tire: 225/55R17 or 235/50R17

Pressure: 27–28 psi (rear)