Starting on my suspension looking for insights

[Dana Pants]

I agree. The sense of not knowing what the rear is doing is very disconcerting and hurts the confidence big time.

I’m not picking on you specially, but this thread has me scratching my head.

It’s obvious what the rear end is doing and what it should be doing IMO... which is sliding those rear tires around the turn.

Usually the problem is the driver is hanging out in the no-mans-land between sliding and sticking and the confidence just isn’t there in this region. So either slow down to stick or speed up to slip and the “problem” goes away.

Sponsored

 

[K4fxd]

Dana this is your disconnect.

The car will oscillate without the tires sliding. This will happen at low G forces on a long sweeper curve.

Say tire grip will allow 120 MPH, the oscillation will start at 75 MPH. Giving the driver no confidence.

Once again, if I was going for a pro seat I would push past the oscillation, but I am not so I will stop pushing the car since I don't want to crash. I've done enough of that learning in my youth.

I would never put a stock GT mustang on a track with other cars.

 

[NightmareMoon]

Dana this is your disconnect.

The car will oscillate without the tires sliding. This will happen at low G forces on a long sweeper curve.

Say tire grip will allow 120 MPH, the oscillation will start at 75 MPH. Giving the driver no confidence.

Once again, if I was going for a pro seat I would push past the oscillation, but I am not so I will stop pushing the car since I don't want to crash. I've done enough of that learning in my youth.

I would never put a stock GT mustang on a track with other cars.

Sounds like a bad wheel bearing, or poor tires for the application. That's the only time I've had the car oscillating noticeably without breaking traction was when a hub went out, and it was very sketch.

Soft springs and shocks in the base car, and lack of a good rear diff can't help the confidence, but I'd argue its a combination of those factors and tire choice as well. not just the rear suspension bushings.

I've done 20+ track days with a PP1 and no rear subframe mods. I'm pretty familiar with how well the car can work w/o taking that specific step. Its a good mod, but not as critical as getting some of the other things sorted IMHO.

 

[K4fxd]

You have a PP1 and are commenting on a Base car.

I have a base car and the steeda IRS braces solved 90% of the trouble. I changed the rest of the bushings and added the full stop the hop kit because I like to race.

 

[TeeLew]

It’s obvious what the rear end is doing and what it should be doing IMO... which is sliding those rear tires around the turn.

The rear *shouldn't* be sliding. It should be completely stable and slightly overpower the front laterally. This excess grip you can use for longitudinal load (braking or throttle, as the case may be).

Having said that, what *should* be is often not what you get. Stock the rear squirms around and is otherwise vague. It's certainly not what anyone asks for. There's a reason I changed all the bushings on the car by ~1700 miles. It communicates to the driver much better this way.

I guess I've just driven enough stuff with blown bushings, leaky shocks and bald tires that I'm just kinda willing to put up with it. Then again, I've crashed my fair share of shit, too, lol!

 

[TeeLew]

At my age 58, and experience, I know how I want a car to feel.
...
I would love to flog a 350R

You're an old fart like me. We drove stuff *alot* worse than this. If you're anything like me, you made some poor decisions and good memories in the process.


... And you bet on the 350R. That'd be a hoot....until a GT4 shows up....

 

[Norm Peterson]

Dana this is your disconnect.

The car will oscillate without the tires sliding. This will happen at low G forces on a long sweeper curve.

Say tire grip will allow 120 MPH, the oscillation will start at 75 MPH. Giving the driver no confidence.

It's a lot easier to see that as being a problem unique to perhaps a few cars rather than something common to all of them. It would have had to show up in Ford's own test driving. I'm not getting this oscillation thing being everybody's complaint, and I'm not picturing where the necessary force variation might be coming from.

First place I'd look would be at the bushings that your added bracing has relieved of most of their locating duty, though that still doesn't identify what's causing the oscillation.

It's really not enough for me to simply know that some 'fix' worked (for this or any other problem); I'd really want to understand better exactly why it worked.


Norm

 

[K4fxd]

I'm pretty sure it was bushing deflection. I've seen YT videos of how the rear subframe moves around while driving.

I am real sensitive to the way cars feel.

 

[Norm Peterson]

I'm pretty sure it was bushing deflection. I've seen YT videos of how the rear subframe moves around while driving.

I am real sensitive to the way cars feel.

I realize that bushings are going to deflect and distort. But for bushing deflections and distortions to vary (and result in oscillations/resonances), something about the forces applied to them must also be varying in order to get the vibrations started.


Norm

 

[K4fxd]

Yea, that does get my mind spinning.

I will just have to be satisfied I have fixed it on mine.

 

[TeeLew]

It's a lot easier to see that as being a problem unique to perhaps a few cars rather than something common to all of them. It would have had to show up in Ford's own test driving. I'm not getting this oscillation thing being everybody's complaint, and I'm not picturing where the necessary force variation might be coming from.

It's primarily the driver's hands and/or feet. Of course, there are bumps & oscillations in the road, but that's generally more biased towards high frequency content.

 

[K4fxd]

I can assure you in my case it was not the driver.

What I will do is find another base 17 and test drive it to compare.

Sponsored