Harsh Ride Quality: Low Profile Tires or Stiff Springs Or Camber Plate or All Combined

My Foxbody Mustang rides a bit harsh for my tastes; mostly over sharp edged bumps (drain covers cracked pavement etc).

It's been a very long time since I've driven a stock Foxbody Mustang but I don't remember them being especially harsh but it's been 30 years since I've driven a stock one.

The springs H&R 490lb front & 250Lb rears with Koni single adjustable dampers and 275/40-17 Falken RT660 tires. 

The car also has camber plates so I know that adds to the NVH but again the car seems a bit harsh over sharp edge bumps. Note I'm not expecting it to ride like a Rolls.

Any thoughts or opinions would be welcome.

Tires and dampers are usually the biggest offenders. Camber plates can probably magnify the effect of the dampers.

I usually find harsh over small bumps but decent ride over larger bumps to be some combination of too much compression damping, stiff tires, or too much friction somewhere in the suspension.  Stiffer tires will transmit more of a shock to the suspension and car.  And if the suspension can't start moving easily or quickly enough then small, quick hits don't get absorbed well. 

The camber plates probably don't help either.  I've found that if you hear an impact more (less noise isolation in the suspension) it tends to feel worse even if the motion is the same.  Some kind of brain trick. 

First place I'd look for that is dampers, especially when they're adjustable. Have you already played with that at all?

I've generally found camber plate bearings to be when good, and loud (not just harsh) when not.

As I understand it, the motion ratios make those very much *not* stiff springs.

In reply to Driven5 :

I just barely started playing with the damper adjustments.

rslifkin said:

The camber plates probably don't help either.  I've found that if you hear an impact more (less noise isolation in the suspension) it tends to feel worse even if the motion is the same.  Some kind of brain trick. 

I suspect this is the case for me as well.  

When I drive the same roads in my wife's 23 Santa Fe, her car doesn't seem as bad, you still feel the hit but it's not near as loud.

I am trying to take into account the Mustang is 40 year old technology.

Most of the Extreme Summer 200tw tires have lousy ride quality as a trade-off to performance -- and it gets worse as the tread wears down. 

The move is to use the soft-riding Conti ECS 02 for street performance.  And you're in luck -- they come in your size.

That's what I use for the Triple Threat ND for long trips.

Are suspension bushings stock or poly?

In reply to Andy Hollis :

Thanks Andy; it's nice to have a tire expert at our disposal.

This will be a hard one to narrow down, given that the last Fox body mustang rolled off the assembly line 32 years ago.  I have chased suspension and tire things on cars for months only to find that it was a wasted body mount bushing allowing the subframe to whack on the body, or a steering rack bushing causing a rattle I feel in my steering wheel.

I often use the example of my dad's new-ish dually truck.  It gives the overall impression of a supremely smooth ride.  In truth, it's punishing, but GM did such a good job of reducing the N and V in the NVH equation that it gives the illusion that it's not H.  The reality is that they're all tied together in the ride's experience, and any one of the letters can make you sense any of the other letters.

I know you're savvy enough to know the difference, but I might suggest some mindful time trying to feel/hear/taste where it's really coming from.  (ok, maybe not taste).  I find that a real intentional investigation into a logical approach to paying attention to things helps narrow it down before throwing parts at something.

I think we have an easy opportunity, though.  Since you have adjustable valving on the dampers, maybe dial them way down to see if things change/improve.

I think Fox body Mustangs are awesome and I was among those who welcomed them with enthusiasm when they came out.  They were a great improvement over most of the other cars that the US automakers had been selling through the '70s and early '80s.  

However, they were still pretty crude by today's standards and were clearly built to a price and their link to the Fairmont was pretty short.  All of that is to say that they never rode all that great and adding performance tires, stiffening the suspension and eliminating the upper strut bushings will only make it worse.

My suggestion is to play with tire pressure and shock settings to get it as good as you can on the street and then just enjoy it for what it is and don't try and make it something else.

Curtis73 (Forum Supporter) said:Since you have adjustable valving on the dampers, maybe dial them way down to see if things change/improve.

Yep.  Besides swapping tires, this is the other thing I do for prolonged street use.  Makes a world of difference.

My first thought was tires given the description. Drop the pressure and see if the behavior changes - it's fast and easy and cheap to try.

APEowner said:

My suggestion is to play with tire pressure and shock settings to get it as good as you can on the street and then just enjoy it for what it is and don't try and make it something else.

That's the plan.

I knew these were crude going in; that's part of the charm for me.

So I actually drove the car to work today and it's actually decent on a variety of roads. I wouldn't want to daily drive it in this trim that's for sure.

The main road between my house and Las Vegas Motor Speedway is pretty torn up and there is construction on Las Vegas Blvd just before the Speedway so that really brings out the worst in the car. The car spends the majority of it's time driving from my house to the Speedway.

As suggested I shall play with tire pressures and damper settings.

As long as the spring rate isn't too much for the damper, I'd adjust the Konis.  And or swap out the bumpstops, they also make a difference.

And, imo, small turns make a difference.  I've just dialed the Miata in now that it's back on the Konis, and they really do a nice job on some of the crappy roads about town.  425/336 springs, so higher than stock spring rates. 

I think you can get it there, even on some of the bad roads.