How can I improve the ride on the street?
 

So my never ending project car is on the road and the ride is a little harsh. The body mounts were replaced with the polyurethene type and contact with the ground is Kumho Ecsta AST 17" tires.
I am feeling everything on the road and was wondering how I can soften up the ride a little. Clearly I am spoiled driving my Silverado 1500 Z and understand its a 50+ year old car. Any suggestions welcome.

Detailed information on what your suspension is comprised of and what size tires and the pressure you’re running them at would be helpful.

The first thing that’s easy to do is to lower your tire pressures a bit, that can make a noticeable difference.

I need to double check the size but I believe they are 245/55/17 up front and 265 in the rear all with 30lbs. Suspension is stock replacement including the springs and I will check the shocks. I will check the shocks tomorrow but everything was installed new about 18 years ago. The car is garage kept.

17" wheels and harsh ride? Where's Formulabruce?

Maybe it’s time to switch to a 15” wheel and tire setup.

18 years ago you might’ve had a different vision or expectation of what you wanted from your car. Maybe the ride quality wasn’t much of an issue when you were younger, over the years things change.

Poly body bushings may be transmitting road harshness and vibration too.

If ride is a concern, going to a 15" wheel and tire setup will help.

The factory parts don't have a lot of NVH cushioning in them, typically placing steel springs, on steel spring perches etc. When you put a 17" wheel and tire on the car, by nature it will get more harsh as there is less sidewall to absorb shock.

If most everything on the car is about 18 years old, but otherwise "new." I would be looking at the suspension soft parts. The control arms may need new rubber bushings, going to rubber body bushings from the poly stuff will also help.

You can also get insulating rubber that mounts between the springs and spring perches. That will typically help with NVH, at the expense of a slightly higher ride height. Another area that is commonly overlooked is the steering system and especially the couplings between the column and steering box. You should have a rag joint here. Make sure it's in good condition as it's designed to dampen the road from entering the steering wheel. Likewise, if the drag link, idler arm, pitman arm and both inner/outer tie rods are in bad condition, not only do you get slop in the steering, but as the pieces rattle and clank together, those two will transmit to the driver through the steering wheel.

If the car has never been restored, take a look at the condition of the sound deadening below the carpet. Over the years this stuff gets hard, cracks and turns into cement. If it's never been replaced, it may be making the ride worse, not better. New insulation and sound deadener will help keep NVH from transferring to the driver through the floors and seats.

Definitely double check the sizes. A 245/55/17 would be nearly 28" tall on the front and there aren't any 265/17's in any profile available that I am aware of.

I'm running 235/45ZR17 front and 255/45ZR17 rears on my Firebird. I was running kyb gas a just shocks and had a very rough ride. I changed them out to QA1 adjustable and that made a huge difference

If you really want to improve ride quality, air suspension, it's not easy, nor cheap, but it is infinitely adjustable and will make most any car ride much better.

Air ride can even make a truck ride like a car. I converted my dually K3500 to air suspension. It's still able to haul the same payload as with steel leaf springs, but the ride is much less harsh, loaded, or unloaded.

My next street car will have air ride incorporated into the chassis without a doubt.

Kit for A Body cars $1500 :

https://www.ezairride.com/1964-1972-...Body_p_99.html

Ride tech has a kit to replace, spindles, tubular control arms, front and rear, matched sway bars, etc. roughly $6000:

https://ridetech.com/product/air-sus...972-gm-a-body/

That's how I'd improve my ride in an A body, but of course it's not everyone's cup of tea. Having already done a 1 ton dually it was a vast improvement over the OEM steel leaf springs.

17" tires and poly bushings aren't helping the cause but probably the simplest thing I'd do are some double adjustable shocks.

Easy to install and doesn't take much time, and the ability to dial in compression and rebound to your liking should make a big improvement in ride quality.

Not a cheap solution but an easy one. Things do however get more expensive from there the more you dive into it.

Road noises ought come from the rear axle, more than the front suspension. Not sure why.

The rubber discs for the rear Springs ought help attenuate loud road pavement. 4-link bar ends will dominate the road noise but may get relief while coasting compared to under accel or braking.

Anything lose enough to rattle and vibrate in the trunk and backseat ought be found out. Even the Decklid plys can be checked for delamination, and add the goop-glue to rejoin the plys. Package tray may be an amplifier of road noises so maybe the jute backed package tray provides relief.

So I am taking a deeper dive into the shocks and am curious about rear coil over shocks, specifically would they improve the ride? I really never put any weight in the car so I wonder how they would help the ride. Also are QA shocks preferred for a softer ride or are there others to consider?

QA1 are a top brand and excellent shock. Viking is one that's used a lot lately, maybe a slightly cheaper price point that seems to be good quality. I'm actually using a Viking coil over setup on a Vega build (QA1 doesn't make a kit for that car) There are other brands and options to shop as well.

I'm sure a rear coil over kit would help ride quality with the ability to tune and adjust different aspects, including spring rates.

This right here. Go back to standard rubber body bushings, most people who installed poly bushings on their ride regretted it, including myself. If the ride is still too harsh with rubber bushings, use a higher profile tire. Throwing money at customs/adjustable shocks and airbag suspension can get really expensive and probably still won't fix the problem. The whole point of body bushings is to dampen road vibrations, poly does the opposite.

I have poly body bushings and I would say a higher quality shock still made a big difference in ride quality.

I had cheap KYBs and the whole car rode like a log truck. I put much better Bilstein HD shocks in the front and it made a world of difference. The rear still has the KYBs and the back still feels rough.

I agree shocks are a big player. I've had some of the cheaper stuff and that has never proved to be great at ride quality.

Spent a lot of money trying different brands and found some improvement, Bilstein being one, but over the last couple years I've grown more fond of double adjustable shocks. Being able to tailor compression and rebound solves a lot of issues, but it gets pretty darn expensive.

Get rid of the urethane mounts & go back to stock

My experience as well.

There are a lot of suggestions to change wheels/tires and change the mounts back to the factory rubber. Im not saying those might not ultimately be the answer......However, wheels and tires are expensive, and body mounts are a pain in the butt to do.

You can buy 4 quality shocks for a reasonable price. I think my Bilsteins were about $80 each or so. Its not like having better shocks will hurt your situation even if they arent the complete answer. Where if you change body mounts you might find it makes no difference and you have to change the shocks anyway.

Haha!! The short version....
1. GM did NOT put large wheels and low profile tires on cars until they could " speed up" the suspension. They did this with a STRUT system.
2. Any old suspension in rubber A arm bushings, and leaf bushings, PINCHED tight and rusted in place, working with a coil or leaf spring are SLOW. and don't move much.
3. Real solution would be Global West Del A Lum bearings in the " A" arms and rear leafs and gas charged shocks, so the suspension could absorb what the Tires Can't. This solution uses existing original A arms etc.