[GoFastBrakeHard]

I got a set of HR5 Hellraisers and Continental DWS 06 AS tire, staggered. Since I put them on the car feels squirmy at WOT. It happens from a stop and when I'm at speed. Even if I'm on the freeway it feels squirmy when I hit the gas WOT.

I know squirmy is not an official automotive term. To better bescribe the sensation, when I go WOT it feels like the car acceleration is pulsating. Even though my foot is 100% down it feels like I'm bouncing the pedal from 95% to 100% and back and forth.

More details: Car is a 2018 Scat Pack, basically stock.

The RPMs stay consistent and do not pulsate, it's not the engine.

When driving normal the car goes in a perfectly straight line and I had the alignment check a few months and, front and back, and it was in spec. according to the shop.

On the back I have 315/35R20 Continental Extreme Contact DWS 06 All Season tires on 10.5" HR5 wheel. The tires grip so much better than the stock RSAs, it's night and day better, but the pulsing concerns me. The front is the 9.5" HR5 with a 275 Conti DWS 06. I dont think the staggered setup ia the issue.

The car was not squirmy before when I had the WRT wheels and stock RSA tires. I put 275/40 BFG Gforce Comp-2s on just the back before I got the HR5s and it was not squirmy then either. It did walk to the left pretty good when I was doing burn outs though. I'm pretty sure the rear alignment needed some work. I had a shop check, but it was not a specialty shop and they just said it was "in spec". I shouls have had them tell me the numbers. But the car drives straight under normal conditions and corners fine, it's only at WOT when it pulses.

The pulsing is mostly front to back. If there is any left/right wiggling I can't feel it, but that doesn't mean there isn't any, its just not as noticeable as the push-pull going on.

So, I'm thinking its something in the rear suspension. I know that having wider wheels and tire with a different offset will change the alignment. My first step is to take it a shop that does custom alignments and get that checked. If that doesn't fix it I'm thinking some of the stock parts are flexing, bushings or control arms. I might even need to get adjustable control arms to get the alignment I want anyway (0.5 camber in the back with just a little toe in, 1.2 in the front with just a little toe out).


Now for my questions:

• Has anyone else had this issue?
• Anyone think it might be something in the drive train and not the suspension.
• Does the Hellcat have the same rear control arms ans bushings as the Scat Pack?
• would a tighter rear sway bar help?

Any and all input is welcome. I have a good amount of knowledge with suspension but none when it comes to fixing issues like this.

Thanks.

 

[Nuke]

Stock suspension (springs and shocks/struts)? How many miles on it?

Normally a report of surging would lead me to declare its KR you’re feeling. Doyou have a tuner you could use to datalog some WOT operation with?

 

[Rocket Man]

are you using spacers on the rear wheels?

 

[Rockster]

I got a set of HR5 Hellraisers and Continental DWS 06 AS tire, staggered. Since I put them on the car feels squirmy at WOT. It happens from a stop and when I'm at speed. Even if I'm on the freeway it feels squirmy when I hit the gas WOT.

I know squirmy is not an official automotive term. To better bescribe the sensation, when I go WOT it feels like the car acceleration is pulsating. Even though my foot is 100% down it feels like I'm bouncing the pedal from 95% to 100% and back and forth.

More details: Car is a 2018 Scat Pack, basically stock.

The RPMs stay consistent and do not pulsate, it's not the engine.

When driving normal the car goes in a perfectly straight line and I had the alignment check a few months and, front and back, and it was in spec. according to the shop.

On the back I have 315/35R20 Continental Extreme Contact DWS 06 All Season tires on 10.5" HR5 wheel. The tires grip so much better than the stock RSAs, it's night and day better, but the pulsing concerns me. The front is the 9.5" HR5 with a 275 Conti DWS 06. I dont think the staggered setup ia the issue.

The car was not squirmy before when I had the WRT wheels and stock RSA tires. I put 275/40 BFG Gforce Comp-2s on just the back before I got the HR5s and it was not squirmy then either. It did walk to the left pretty good when I was doing burn outs though. I'm pretty sure the rear alignment needed some work. I had a shop check, but it was not a specialty shop and they just said it was "in spec". I shouls have had them tell me the numbers. But the car drives straight under normal conditions and corners fine, it's only at WOT when it pulses.

The pulsing is mostly front to back. If there is any left/right wiggling I can't feel it, but that doesn't mean there isn't any, its just not as noticeable as the push-pull going on.

So, I'm thinking its something in the rear suspension. I know that having wider wheels and tire with a different offset will change the alignment. My first step is to take it a shop that does custom alignments and get that checked. If that doesn't fix it I'm thinking some of the stock parts are flexing, bushings or control arms. I might even need to get adjustable control arms to get the alignment I want anyway (0.5 camber in the back with just a little toe in, 1.2 in the front with just a little toe out).


Now for my questions:

• Has anyone else had this issue?
• Anyone think it might be something in the drive train and not the suspension.
• Does the Hellcat have the same rear control arms ans bushings as the Scat Pack?
• would a tighter rear sway bar help?

Any and all input is welcome. I have a good amount of knowledge with suspension but none when it comes to fixing issues like this.

Thanks.

There are a number of things to consider.

One is the staggered setup can affect the effective caster angle of the front wheels. If the front tires/wheels are not as tall as the factory wheels/tires coupled with the rear wheels/tires maybe being taller this steepens the caster angle.

This can make the car twitchy. Caster is normally not adjustable so aftermarket steering/suspension hardware which supports caster adjustment could be required to bring this back into spec. Yes, before going this route the caster should be checked to see if it is within spec or not.

If you went with wider tires these are more prone to tramlining and this can make the car feel squirrely. With other cars which came from the factory with very wide tires more than once the tires were so affected by the road surface and manifesting tramlining that to me felt like a low tire. (No tire pressure monitoring system in these cars.) It felt so bad that I'd leave the freeway in order to check tire pressures were ok.

Also if the tires chosen do not have the load rating, tread hardness, etc., they may be simply inadequate to support the car and its weight. Just because tires will fit on the wheels and the wheels fit under the wheel wells doesn't mean the tires are suited for the job.

Also, tire pressures may not be ideal. Experimentation may be required to arrive at a suitable tire pressure for the staggered setup.

Added: To help arrive at the proper inflation pressure one can use chalk and chalk a portiono f a front and back tire tread surface. The chalking wants to be not only on the tread proper to extend a ways down both the inner and outer sidewalls.


Then drive the car and after a bit note the chalk.

If the chalk is gone all the way past the tread surface the tire is under inflated.

If there is a strip of chalk on the outer edge of the tread the tire is over inflated.

 

[trippytro]

One thing i noticed on my ride after i put my first set of REALLY sticky tires on the front, it was definitely more twitchy feeling, along with a plethora of suspension mods but thats unrelated to this topic...


Severe toe angle or camber angle can definitely make the steering more twitchy.


First things i would check:

-Wheels are torqued to spec
-PSI is to spec
-No suspension worn (control arm bushings or ball joints)
-Integrity of tires (possible to be out of round or a bubble somewhere not visible? Not likely)

 

[GoFastBrakeHard]

More info...

Car has 20K miles and the suspension is all stock (I have been under there a few ties and for sure stock). The prior owner put 18K of those mile on it for the year and a half he owned it, the condition of the car leads me to believe he didn't drive it hard (car was immaculate), he just drove it a lot, probably a DD. (I know he lived in Elk Grove, Ca. Probably commuted to Sac. but that's just a guess.)

I don't have a way to record KR but I was thinking about putting the stock wheels/tires back on to see if the pulsing goes away. If it doesn't go away then it's not KR. Although I don't think it is KY, I am not ruling that out yet. If I didn't put on knew tires this would be my first presumption, but it happened immediately after putting on the new wheels.

No wheel spacers.

The tires are 99% the same height as stock. (I looked it up on tiresize.com).

Tires, front and back, have higher load ratings than the stock tires. Although one thing I do know is the side walls are not as stiff as the stock RSA's. However, I have seen others with the same setup and they didn't have the same issue. I don't think the sidewall being softer is the issue.

I don't believe it is tramlining as I have tested on surfaces that I know are flat. The pulsing is very consistent regardless of the street surface.

I will play around with the tire pressure. This could help.

I am 95% sure it's the back and not the front. The steering feels fine. It feels like the back is bouncing a bit. Pulsing, bouncing, squirmy, hard to explain. But it for sure feels like it's in the back. I feel it in the seat, not in the steering wheel.


-Wheels are torqued to spec: Yes

-PSI is to spec: yes but there is some room to play. They are all around 34 psi when cold and warm up to 36/37. I'm actually thinking it might be a little high.

-No suspension worn (control arm bushings or ball joints): This I don't know. I will need to check. Now that I think about it I have been hearing what sounds like could be a worn bushing. Like an old truck goes over a bump and it creaks. I hear a squeak-squeak when turning and a slight change in road height (coming into the road that leads to my house is a 90 degree turn where the hight changes by a foot or so). I will for sure take a look. Bad bushing would for sure cause this issue.

-Integrity of tires (possible to be out of round or a bubble somewhere not visible? Not likely) This is a possibility but I haven't heard this being an issue with the DSW 06's. Not ruling it out yet.

Thanks for the help so far guys. I have some work to do. Still gonna get an alignment done regardless.

 

[Story]

Are the DSWs directional? Try just your old rears and see if problem goes away.

 

[forcedfedbug]

You didnt mention your drive mode. I have 315's in the back as well, and only drive the car in track mode. I have turned it off a few times though for 1-2 minutes while at a drive through and in normal mode my car does the same thing. In track mode no more engine pulsing. I never looked at that as in issue since I never drive in normal mode when it actually does that its my que that I didnt change it to track last time I turned on the car. I always thought it was because I went from a 275 to a much more sticky much wider tire and the traction control is not programmed for the car to be able to accelerate that hard and is kicking in. That is why it does not do it when in track mode as that is turned off. Not that that is your issue but your description is my experience with the car when in normal drive mode.

Ron

 

[GoFastBrakeHard]

They are directional. Only 1 side is the outside. Since my setup is staggered I can only rotate left and right. But I will try putting the old tires on.

I almost always drive in track mode. I will try the other modes but don't think that will be the issue.

My biggest issue is finding the time to work on the car. I'm on furlough but have had my hands full with the family: newborn and an ailing father, plus a 10 year old and a very, very needy wife.

 

[trippytro]

They are directional. Only 1 side is the outside. Since my setup is staggered I can only rotate left and right. But I will try putting the old tires on.

I almost always drive in track mode. I will try the other modes but don't think that will be the issue.

My biggest issue is finding the time to work on the car. I'm on furlough but have had my hands full with the family: newborn and an ailing father, plus a 10 year old and a very, very needy wife.

Even with your staggars setup, all the tires should read “outside” on the outside. If thats not the case, then they have installed the tires incorrectly on your wheels and no rotation will fix that.

 

[GoFastBrakeHard]

The tires are installed correct. First thing I checked when they got installed before I left the shop.

The place I went to is a top rated race shop. Planning to do the alignment there also. Dude is an old school racer. Not racing anymore. Roger Kraus. Raced a Corvette and F1 I beleive.

 

[trippytro]

The tires are installed correct. First thing I checked when they got installed before I left the shop.

The place I went to is a top rated race shop. Planning to do the alignment there also. Dude is an old school racer. Not racing anymore. Roger Kraus. Raced a Corvette and F1 I beleive.

Oh sorry I misunderstood i thought you said only 1 of your tires read “outside” on the outside

 

[GoFastBrakeHard]

Oh sorry I misunderstood i thought you said only 1 of your tires read “outside” on the outside

All good. Sometimes it's hard to explain so part of that was on me.

 

[A Guy]

The DWS06 are not directional, but they are asymmetric, so have an inside and an outside. I know that's what you meant though

A Guy

 

[GoFastBrakeHard]

The DWS06 are not directional, but they are asymmetric, so have an inside and an outside. I know that's what you meant though

A Guy

Yes, that's what I meant. But with the staggered tire size I can only rotate left and right. Worth the extra grip in the back, IMO.