Suspension Harsh Ride

PonyGTrider · Mar 20, 2026

Hi all,
My suspension details on my 90 GT are as following:
FRONT: Polyurethane stock control arm bushings, Eibach Pro kit progressive rate front lowering springs, Hotchkis caster/camber plates with spherical bearings, and Bilstein BSN-35-041392

REAR: Eibach Prokit progressive rear lowering springs, J&M lower control arms w/polyurethane bushings, stock upper control arm bushings, polyurethane
differential housing bushings, and Bilstein HD shocks BSN-24-021487

The issue I’m experiencing is that I’m getting fed up of an extremely harsh ride specially on the street and on long rides.

How can I improve the comfort of my ride quality? I forgot to mention that I have Yokohama Avid Envigor 245 45 17 all four inflated at 32 psi.

The handling is perfect with zero rolling but just too harsh.

I’m thinking the shocks and struts are extremely stiff!!!

What are you guys using? Maybe adjustable struts ?
I want durable struts and shocks, in the past I used KYB GR2 but they went bad too soon!!!!!p ease chip in your opinions and suggestions.

Thank you all!

gkomo · Mar 20, 2026

Interesting, I ran the pro-kit back in the day and thought it wasn’t too bad. Compared to my H&R Race springs (which are dog for street driven cars) they would almost seem ‘plush’. How old are the bilsteins you’re running?

Harsh rides are subjective though, what may seem harsh to you could be fine to someone else. That combo should be fine I would think even with the poly control arm bushings. Do you notice (harsh) bumps more in the front or rear?

You’re 100% sure the springs are the pro kit and not the sportlines? Pic of the car at ride height?

PonyGTrider · Mar 20, 2026

gkomo said:
Interesting, I ran the pro-kit back in the day and thought it wasn’t too bad. Compared to my H&R Race springs (which are dog for street driven cars) they would almost seem ‘plush’. How old are the bilsteins you’re running?

Harsh rides are subjective though, what may seem harsh to you could be fine to someone else. That combo should be fine I would think even with the poly control arm bushings. Do you notice (harsh) bumps more in the front or rear?

You’re 100% sure the springs are the pro kit and not the sportlines? Pic of the car at ride height?

The Bilstein I have are somewhat old but I drive my car only a few hundred miles per year.
The harshness happens both front and rear but maybe a bit more at front.

Now you made me wonder about which ones I have. I will double check the receipt to make sure and will post a replay with a confirmation.

gkomo · Mar 21, 2026

Based on the photos I would say those are the pro kit springs. Not low enough in my opinion to be the sportlines.

Any visible signs of leakage from the struts/shocks?

AeroCoupe · Mar 21, 2026

I ran the urethane bushings for about a week when I daily drove my Coupe. Absolutely terrible. This was with H&R Super Sport springs and Tokico Illumina dampers. Also had stock rear uppers and MM lowers blah blah blah. Put Moog rubber bushings back in the front control arms and in the rear axle and it was night and day difference.

Mustang5L5 · Mar 21, 2026

I have pro-kit springs and bilstiens on my SN95 and the ride is rather fantastic. Firm and certainly not harsh. Granted SN95 and Fox ride a little bit differently

However I think your issue is the poly bushings. One of the tradeoffs with them is NVH. You’ll get fantastic handling but at a cost.

I would actually start at the axle bushings and replace those poly bushings with rubber and see if that helps any. These 4-links are prone to bind when you put too much poly in them which is why MM recommends stock rubber bushings for the upper arms and in the axle.

86HO5.0 · Mar 21, 2026

x2 on the Poly bushings.

Front LCA bushings and axle bushings back to rubber is where I'd start.

PonyGTrider · Mar 21, 2026

gkomo said:
Based on the photos I would say those are the pro kit springs. Not low enough in my opinion to be the sportlines.

Any visible signs of leakage from the struts/shocks?

I believe they’re the Pro Kit and absolutely no leaky struts

PonyGTrider · Mar 21, 2026

Mustang5L5 said:
I have pro-kit springs and bilstiens on my SN95 and the ride is rather fantastic. Firm and certainly not harsh. Granted SN95 and Fox ride a little bit differently

However I think your issue is the poly bushings. One of the tradeoffs with them is NVH. You’ll get fantastic handling but at a cost.

I would actually start at the axle bushings and replace those poly bushings with rubber and see if that helps any. These 4-links are prone to bind when you put too much poly in them which is why MM recommends stock rubber bushings for the upper arms and in the axle.

Probably you’re right with these prothane bushings it gives me superb handling and no positive toe or deflection under hard braking and no rolling while turning at high speed.
So I might have to orderfrontblower control arms with stock rubber bushings

2000xp8 · Mar 22, 2026

Along with the poly bushings in the rear, I'd switch the front to coil overs and the rear to H&R springs. I couldn't believe how soft the H&R springs felt in the back compared eibach springs.

I think Superb handling is a bit of an overstatement, without at least a panhard bar, you are just getting the illusion it handles well, even though you are really just one slingshot across a highway from realizing this 4 link is ok to a point, then it's just dangerous.

I've got the suspension pretty much right where i want it, took years and thousands of dollars of parts and mistakes.

limp · Mar 22, 2026

My rule on bushings is any twisting movement and they get rubber, any others get poly...
Ordered some special material bushings from Australia for my C4 corvette suspension going on my 65 Restomod car.. Supposed to work like rubber, but be stiffer like poly but will not crumble and die like poly... We will see....

limp · Mar 22, 2026

View: https://youtu.be/Ah_F2Ydy_Os

86HO5.0 · Mar 22, 2026

I really like the SuperPro bushings in my Volvo 240. Excellent product, I think you'll be happy with em'.

limp · Mar 22, 2026

86HO5.0 said:
I really like the SuperPro bushings in my Volvo 240. Excellent product, I think you'll be happy with em'.

Good to know.. Thanks..

PonyGTrider · Mar 22, 2026

limp said:
My rule on bushings is any twisting movement and they get rubber, any others get poly...
Ordered some special material bushings from Australia for my C4 corvette suspension going on my 65 Restomod car.. Supposed to work like rubber, but be stiffer like poly but will not crumble and die like poly... We will see....

Sounds like a good idea

PonyGTrider · Mar 22, 2026

86HO5.0 said:
I really like the SuperPro bushings in my Volvo 240. Excellent product, I think you'll be happy with em'.

I will see the possibility of getting those if they make them for our application.
Thank you

PonyGTrider · Mar 22, 2026

2000xp8 said:
Along with the poly bushings in the rear, I'd switch the front to coil overs and the rear to H&R springs. I couldn't believe how soft the H&R springs felt in the back compared eibach springs.

I think Superb handling is a bit of an overstatement, without at least a panhard bar, you are just getting the illusion it handles well, even though you are really just one slingshot across a highway from realizing this 4 link is ok to a point, then it's just dangerous.

I've got the suspension pretty much right where i want it, took years and thousands of dollars of parts and mistakes.

That sounds like a good idea, probably I exaggerated on the superb handling but I feel the handling very good, firmly and responsive.
I have no idea on my front to rear weight balance, I have a 306 ci with twisted wedge heads stage 1 cam and TFS lower and upper intakes and the battery is in the trunk, so what would be the appropriate coil-overs and H&R rear springs should be? Perhaps some part numbers???
I just came back from a short test ride with all the tires 30 psi or air pressure and definitely it made a difference.

In this idea what could be a good tire air pressure on my Yokohama avid Envigor 245 45 17 ??? Some settings that don’t sacrifice much fuel economy and or cause an abnormal thread wear that could better the ride comfort?????

limp · Mar 22, 2026

PonyGTrider said:
Sounds like a good idea

Came to this conclusion after my first Poly suspension.... The squeaking was like chinese water torture..... Now we read about how the poly bushings actually can crumble away.... live and learn

PonyGTrider · Mar 22, 2026

limp said:
Came to this conclusion after my first Poly suspension.... The squeaking was like chinese water torture..... Now we read about how the poly bushings actually can crumble away.... live and learn

That’s funny, I pressed in those red prothane bushings around 15 years ago and not a single squeak in all of these years and still not crumbling at all, they still perfect.
There are an infinite variety of polyurethane bushings out there which I will never buy, some of them are hard as a rock and they are just garbage.
I use Prothane and Energy Suspension and they hold years without issues from control arm bushings and manual transmission mount and cross member bushings.

2000xp8 · Mar 23, 2026

PonyGTrider said:
That sounds like a good idea, probably I exaggerated on the superb handling but I feel the handling very good, firmly and responsive.
I have no idea on my front to rear weight balance, I have a 306 ci with twisted wedge heads stage 1 cam and TFS lower and upper intakes and the battery is in the trunk, so what would be the appropriate coil-overs and H&R rear springs should be? Perhaps some part numbers???
I just came back from a short test ride with all the tires 30 psi or air pressure and definitely it made a difference.

In this idea what could be a good tire air pressure on my Yokohama avid Envigor 245 45 17 ??? Some settings that don’t sacrifice much fuel economy and or cause an abnormal thread wear that could better the ride comfort?????

Just call maximum motorsports and ask them. They will sell you what you need.
I ran a red set of H&R springs, which probably means I had the "race" set, judging by pictures on their website.
Now I use torque arm specific H&R springs.

For the front I use 275lb springs on MM bilstein coil overs. I'd guesstimate 300 or 250lb springs would be just fine too.

Their parts do cost more money, just keep in mind it's a one time cost.
Don't quote me on this, but i also believe MM front control arms will work on the stock k member (just need the right offset). I wouldn't waste my time with new stock replacements if you goto coil overs.

Suspension Harsh Ride

PonyGTrider

gkomo

now i can hopefully expect to receive the shaft

PonyGTrider

Attachments

gkomo

now i can hopefully expect to receive the shaft

AeroCoupe

lube between the nut and the face. I know my lubes

Mustang5L5

That is…until I whipped out my Bissell

86HO5.0

Active Member

PonyGTrider

PonyGTrider

2000xp8

limp

wrap a little cheese around it and its a done

limp

wrap a little cheese around it and its a done

86HO5.0

Active Member

limp

wrap a little cheese around it and its a done

PonyGTrider

PonyGTrider

PonyGTrider

limp

wrap a little cheese around it and its a done

PonyGTrider

2000xp8

Similar threads

Suspension Harsh Ride

now i can hopefully expect to receive the shaft

Attachments

now i can hopefully expect to receive the shaft

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

Active Member

wrap a little cheese around it and its a done

wrap a little cheese around it and its a done

Active Member

wrap a little cheese around it and its a done

wrap a little cheese around it and its a done

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