GT0131

Hi all, looking for some help.

Car is a 2017 Mustang GT Fastback. I'm trying to improve the ride quality.

Suspension is stock except for

- Lowered springs all round . Vogtland which drops the car about 25 millimetres (1 inch)

- Whiteline thicker adjustable sway bars front and rear

Driving on an uneven surface the car rocks around like a boat at sea and is harsh . Sometimes you feel like your teeth are gonna fall out. It is very sensitive to changes in road surface and going over speed humps you know about it

I'm not sure whether it's because the lower springs don't match the factory shocks, but I don't want to go to the expense of changing them if it's not gonna fix the problem. I'm also not sure if the sway bar has contributed to the issue at all, but can't see why it would

Thanks for your help

Pete

DarrenGT

just out of curiosity, what tires are you running? size ?

Bert

I think it is probably because the springs are too much for the struts and shocks -- meaning: the spring rate of most lowering springs is higher than the stock springs. This is needed to firm up the ride, and because you would be bottoming out all the time due to the reduced suspension travel, if the springs weren't stiffer. Because the springs are stiffer, the original struts and shocks don't have enough damping to keep them under control; so on rebound the car bounces or jumps.

The stiffer anti-sway bars could be contributing to this a little also. They effectively increase the spring rate on the outboard side, when going around a corner. I think that would be a relatively minor contribution though.

So -- I think you probably need new struts and shocks, that have more damping and are well matched to those springs. I don't know exactly which struts/shocks those would be, but have heard that Koni STR-T are generally pretty well matched, also Bilsteins are supposed to be a pretty good match for most lowering springs.

And generally the ride will be stiffer with the lowering springs, no matter what, there is no way around it. But it should not be bouncing around like crazy.

houtex

Yep, new struts and shock are in order like Bert says. Check this out:

https://www.rockauto.com/en/catalog/...ion,strut,7584

Notice the different struts needed for different makes of Mustang. 18-19 inch wheeled coupes, 20" convertible... crazy. All because Ford wants that ride to be smooth as it can be, so they make the shocks to help get the car back to stock ride height. So when you deprived them of their inch of travel, they can't figure it out and you get that bouncing around.

I found this out on my '06, and they're still doin' it, looks like. Dang thing bounced around like a ping pong ball over things when I did the 1" drop but didn't replace the shocks/struts. After a bit, I finally got the Koni SRTs and tada, problems solved, car rides like it ought. Stiffer, lil' rougher, you feel more of the road, let's be honest, but at least it doesn't bottom out and bounce like a pogo stick anymore.

For what that info's worth. Have a good one, and welcome to the forums!

m05fastbackGT

I can also confirm that as well from personal experience.. OEM dampers just don't have adequate valving to handle the shorter length of lowering springs which can often affect the travel distance between the damper and spring during rebound. When my car still had the OEM dampers paired with the Eibach pro lowering springs, the suspension felt like it was bottoming out every time when going over uneven road surfaces and bumps. Since swapping out the OEM dampers for Koni yellow adj dampers, they resolved the bottoming out issues of the suspension right away.. Therefore, I would also highly recommend making the switch from your OEM struts/shocks to those designed specifically for lowering spring applications.