Dodge Challenger Forum banner
  • Hey everyone! Enter your ride HERE to be a part of October's Ride of the Month Challenge!
1 - 17 of 17 Posts

·
Registered
Joined
·
7,683 Posts
Discussion Starter · #1 ·
I suppose that question pretty well answers itself, when talking about lateral transfer, as when hard cornering, right?...lower car, less weight transfer, more even grip by the tires?

Does the same apply in the longitudinal direction when launching hard?...lower car, less weight transfer, less variation in launch traction (for better or worse)?
 

·
Registered
Joined
·
1,103 Posts
If you have a car with limited traction tires, yes, jacking up the car helps the weight transfer. If you have gigantic slicks in back you can keep the car as low as you want, but if traction is a problem, getting the car up a bit and loosening up the front suspension can help throw more weight on the back tires when you launch.

Bill
 

·
Premium Member
2009 Challenger R/T
Joined
·
8,919 Posts
when you lower the car you change the trajectory of your suspension so for instance using springs only this will hinder your launch and not allow the car to squat you lose your weight transfer. Now if you were to use adjustable coil overs that you can change the dampening you can set the rear to about a 50/50 ratio and loosen up your fronts to replicate a 90/10 or 80/20 front shock this will aid in your weight transfer, also if you have a heavy sway bar up front this will hinder you in the quarter mile.
 

·
Registered
Joined
·
7,683 Posts
Discussion Starter · #4 ·
To clarify a fine distinction...I wasn't trying to say that lowering the car gives you more launch traction. What I was really trying to say is that the launch traction is more or less the same, regardless of how you launch. The alternative scenario is if you have a car that squats more (because it is not as low, or more jacked up in the back), there is a certain sweetspot to launching that will maximize traction...too much/too quickly, and the tires go up in a spin vs too little/too late and you miss that point where the weight transfer to the rear facilitates maximum bite to the pavement. Somewhere in the middle, the planets line up and the full powder keg of engine fury makes it to the ground to blast the car into motion...am I right?
 

·
Registered
Joined
·
7,683 Posts
Discussion Starter · #5 ·
So where I was really going with this is...do you think weight transfer at launch has an effect on the emergence of wheel hop (reducing or increasing)?
 

·
Registered
Joined
·
7,683 Posts
Discussion Starter · #6 ·
C'mon, people...I just implied a provocative theory on wheel-hop. Nobody's interested???
 

·
Registered
Joined
·
491 Posts
I like your posts but I don't have much to add to your theory.

If you are bottoming the suspension I can see were the rebound would want to start hop.Unloading the tires. So from your other post a lowered car could cause it more. Esp if the car has alot of rear camber from lowering.

I have a 2011 srt I don't think I have hop but I don't try and break loose the tires every chance I get.

Smooth is fast in my world.
 

·
Registered
Joined
·
7,683 Posts
Discussion Starter · #8 · (Edited)
Thank you for replying to my topic!

See the idea here is that the lower you go, the less weight transfer there is on launch. Hence, there is less force on those back wheels, than would be if there was a dramatic weight transfer effect. So if the wheels have a natural tendency to hop under load, there is less force to keep them pushed to the ground, and the hop emerges.

I also agree that camber may also contribute to the phenomenon, as well, especially if there is even further camber gain on deflection from weight transfer. It's setting up for an automatic energy release event when the tire reaches its traction limit while in a significant at-camber state. Then after the energy release, the suspension unloads, the camber goes back to the static value, and the tire regains grip. If engine load is still present, the tire ratchets up again until the camber reaches a threshold where the traction falls off, and the tire breaks loose again, and so on...
 

·
Registered
Joined
·
515 Posts
You're half right. Wheel hop is cause by energy buildup and release, but it's in the cradle bushings not the springs.

Under acceleration the pumpkin tries to rotate in the opposite direction to the tires. Since it's attached to the cradle, the whole cradle moves until the bushings have stored enough energy to pop the tires loose. Just like leaf springs winding up from a ( to an S shape under acceleration. Since the springs are also attached to the cradle, lowering won't have much if any effect.

Weight transfer is affected more by spring/shock rates and suspension design than by static ride height. But this won't help with wheel hop until the cradle bushings are firmed up. Chrysler puts a lot of rubber in the suspension so you get a smooth, quiet ride.

There's a reason the Drag Pak uses a solid axle with a 4-link.
 

·
Registered
Joined
·
7,683 Posts
Discussion Starter · #10 · (Edited)
...but what are things that can make it more prevalent vs less prevalent short of replacing the whole rear end with a solid axle and totally different suspension? ;) I don't think anybody has come up with a sure-fire solution to stop it outright, yet. Sometimes a tweak works, sometimes not, and sometimes it only gets as far as reducing it a bit. I'm told the Mustang even suffers from wheel hop (albeit, at a higher threshold of abuse). So even a solid axle may not be the way out of wheel hop, either.

Weight transfer is affected by the distance between center of gravity and the roll center, isn't it? That is why lowering a car affects weight transfer. It reduces the distance, hence a reaction force acting through a shorter "lever" to rotate the car (wheelie style). It will also reduce the down force on the rear tires at launch, and that might have been just enough to keep wheel hop at bay. That's the idea I'm working on, at least.

Shocks and spring rates can change the amount of deflection that occurs, but not necessarily change the amount of weight transfer, itself.
 

·
Registered
Joined
·
515 Posts
With IRS it's super complicated. These cars have a 5-link rear suspension (5 links per wheel so I guess it's really a 10-link). Without knowing the exact dimensions and vectors of each link and the pitch center and CG, you're flying blind. This is the kind of thing that Chrysler engineers spend months on. Link lengths and mounting points are fixed so it's kind of academic anyway. The underlying cause is cradle movement. If the cradle was welded to the floor you'd have a lot less hop.

Back to bushings for a minute: Let's say the bushings can absorb 300 lb-ft before they rebound (pulling a number out of my butt). You have a choice then, either launch easy or reduce traction. Put a couple of donut spares on and you'll have plenty of spin but no hop, because the tires slip before the bushings reach their torque limit. You're trying to achieve this by weight jacking instead. The problem with that is that you aren't doing anything to the soft bushings, which is where the problem is in the first place. They're going to hop when they get that 301st lb-ft regardless.

Wheel hop is one of the compromises they made in the design process. Compare the number of buyers who say "not having wheel hop at the drag strip is very important", to the number of people who say "I want a smooth quiet ride." That's why there's rubber back there instead of Heim joints.

I think your first step should be a bushing kit. Anchor the cradle to the body as solidly as possible. That alone will probably take care of the wheel hop. Then and only then can you work with weight transfer to optimize your launch.
 

·
Registered
Joined
·
7,683 Posts
Discussion Starter · #12 · (Edited)
Yes, I think many have already tried the bushings and solid-mount cradle approach with varying results. They also note that it is the most obvious thing to correct as a first step. So I don't think that has turned out to be a slam dunk fix, as was expected, or it would simply be the solution to eliminate wheel hop...with no excuses. It's just the most obvious thing to address, if wheel hop is battering-up hardware back there, but I don't get the impression that it is the sure-fire solution, at this point.

So that is why I am premising that lowering and weight transfer effect is the other half of the battle there. You get enough weight transfer back there to press the tires to the ground, then the tires will have much less chance of breaking traction and then chattering (it's a natural negative feedback mechanism at work). A taller sidewall to provide more "give" after sudden load couldn't hurt, either. It will facilitate more time for weight transfer to fully establish, before the tires attempt to really pull forward. What exists now is nearly instantaneous, forward traction (sticky, modern-optimized compounds + low sidewall on a 20" wheel) before the weight transfer can even setup. If the car is lowered (or just the standard height of the SRT suspension), then there is already a reduction in weight transfer effect on top of that.

I am curious if anybody had the experience where wheel hop got worse after lowering the car...
 

·
Registered
Joined
·
515 Posts
So what you really want is more anti-squat. And this is where it gets tricky, especially with IRS.

This page: Tuning 4 Link Rear Suspensions for the Drag Strip will show you how it works with a conventional 4-link. But we don't really have longitudinal links. You may (or not, looks hard) be able to fudge some "virtual" links by looking at where the goofy diagonal and transverse links pivot and get a rough idea of anti-squat from that.

So here: Megan Racing we have a page on body roll. Specifically, how body roll relates to lowering. Which helps very little on the drag strip, but the physics are what's important.

You may be able to figure out what you need from these, but you'll probably need either an engineer or a computer to help. Possibly both.
 

·
Registered
Joined
·
7,683 Posts
Discussion Starter · #14 ·
Well, I'm not really looking for it, personally. I'm just putting the idea up for consideration by those who are experiencing severe wheel hop. :)
 

·
Registered
Joined
·
627 Posts
So of I lower my car I'll have less traction?
 

·
Registered
Joined
·
7,683 Posts
Discussion Starter · #16 ·
Not necessarily less traction...there will be less variation in traction (due to less weight transfer) after the car is lowered.

...but more importantly (in the context of this topic), less weight transfer means less force pushing the wheels into the ground (when they need it most), which may be enough of an effect to allow wheel hop to readily emerge into an oscillation.
 

·
Premium Member
2009 Challenger R/T
Joined
·
8,919 Posts
Yes, I think many have already tried the bushings and solid-mount cradle approach with varying results. They also note that it is the most obvious thing to correct as a first step. So I don't think that has turned out to be a slam dunk fix, as was expected, or it would simply be the solution to eliminate wheel hop...with no excuses. It's just the most obvious thing to address, if wheel hop is battering-up hardware back there, but I don't get the impression that it is the sure-fire solution, at this point.

So that is why I am premising that lowering and weight transfer effect is the other half of the battle there. You get enough weight transfer back there to press the tires to the ground, then the tires will have much less chance of breaking traction and then chattering (it's a natural negative feedback mechanism at work). A taller sidewall to provide more "give" after sudden load couldn't hurt, either. It will facilitate more time for weight transfer to fully establish, before the tires attempt to really pull forward. What exists now is nearly instantaneous, forward traction (sticky, modern-optimized compounds + low sidewall on a 20" wheel) before the weight transfer can even setup. If the car is lowered (or just the standard height of the SRT suspension), then there is already a reduction in weight transfer effect on top of that.

I am curious if anybody had the experience where wheel hop got worse after lowering the car...
Yes let me explain and what type of car 2009 RT M6 STP car came with nivomats... first mod was 2" lowering springs Tien and upgraded sway bars 285/40/20 tires great on the street the cars rear was so firm that she wouldn't squat and transfer weight at the track which caused excessive wheel hop this was in the summer of 2009, 2nd setup to help correct this was to change out and put on adjustable end links, adjustable sways and changed out the shocks to SRT Bilstiens results were vastly improved ride and handling also the car saw improved launches at the track but wheel hop still occurred street and track (tire changed to a 295/40/20) when I went to the track with a 18" DR my wheel hop went away... We also noticed that the car would squat but was still pushing the front and back down to quick...
I had the opportunity to spend time with Greg from Petty's Garage and got educated as to why I was having trouble at launch so I had them change out all of the rear cradle bushings, end links, complete front end bushings also, we installed the X-treme XA Coil-Overs ect... final outcome was no more wheel hop on the street or the track I have run Nitto NT05 and NT05r 315/35/20 currently running a Vredestein 315/35/20 the car squats nicely and keeps the weight to the tires, when I go to the track I set my rear at whats equivalent to a 50/50 shock rate, the fronts I loosen up (back off) so that I get the lift and weight transfer (estimated 80/20) I have improved my 60' to a consistent 1.8 with street tires... should be interesting once I get a chance to run the 28/10/17 Hoosier's :guiness:
 
  • Like
Reactions: randycat99
1 - 17 of 17 Posts
Top