05 GT Rear suspension advice for compliance and sway feeling

tw557

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I have an 05 GT that has Roush shocks and struts and ford racing lowering springs installed. Everything else is stock from what I can tell other then GT500 front LCA. The front feels very good to me very quick steering and decent over the rough back roads. I also have gt500 wheels on at 19 x 9.5. 255 40 front and 275 40 rear. I just have trouble getting used to the rear feeling of always swaying so much until it sets into the turn or even quick movements on the highway. I tried jacking the air pressure up to 45 just to firm it up but didn't feel a lot of change. Would a better pan hard bar or brace help? Would LCA's do anything for this? Also the ride is not too good over the rough stuff in the rear. If a quick dip in the road it seems to jolt me more then a bump up. In general just doesn't feel planted. Reminds me way too much of my old 82 gt. I assume a better set up shocks is in order. My other car is an Ecoboost mustang with Ford Racing shocks, struts and springs which really handles remarkably well and very good over the same bumps. I guess the IRS has me a bit spoiled but I am sure the 05 can be better. Just open to any advice.
 

rocky61201

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The list of suspension upgrades is a long one so I'll keep it simple and give you one thing that is often overlooked and cheap. Since you have lowering springs make sure you have the proper jounce bumpers in the back or cut yours down if the stockers are still in there. A hard jolt and bottoming out of the rear suspension will unsettle the rear end in a bad way. Also check the angles of your control arms and that the rear axle is centered since you have lowering springs. Adjustable control arms, pan hard bar, and lower control arm relocation brackets are the only way to bring everything into proper spec.

I don't have it installed, but everyone raves about a watts link setup.
 

sman247

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I have a watts link along with every other suspension mod you can have. The watts link made the single most difference on my car out of any mod I've done with the exception of my Whipple. It changed the car completely. LCAS are more for traction when taking off such as at the strip. If your looking for better handling I would spend money on a set of sway bars before LCAS.
 

tw557

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I did cut off the top of the bump stops. That did help. Also from left to right the axle is centered within 1/16 with stock panhard which I was surprised. I'll look at the lca angle too. The watts link does sound very interesting. Would a panhard bar and brace do much for the sway I feel. It's not a lean but a swag from side to side that bothers me.
 

RocketcarX

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The shocks and struts are prolly wore out. Check to make sure you cut enough off the bump stops, that was going to be my first suggestion as well, so I'll echo what what was already said.
 

Pentalab

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I did cut off the top of the bump stops. That did help. Also from left to right the axle is centered within 1/16 with stock panhard which I was surprised. I'll look at the lca angle too. The watts link does sound very interesting. Would a panhard bar and brace do much for the sway I feel. It's not a lean but a swag from side to side that bothers me.

The watts link will eliminate the back end flailing back and forth as the suspension goes up /down. I use the white line watts.
My guess is your oem LCA's bushings are trashed..and probably your oem UCA. Front end of oem uca is rubber. Back end of UCA ends up on the oem rubber bushing, that is on top of the differential..... if the one on the differential is trashed, the car will flail about, ditto with rubber bushing at front end.

I tossed all that junk, replaced with BMR lca's, and adjustable BMR UCA..and mating BMR UCA mount. My axle was not centered after lowering, so replace the oem PHB and oem PHB with the BMR on car adjustable PHB and mating BMR PHB brace. With all the oem rubber bushings out of their, the car is solidified.

I use Roush front + rear sway bars.. + roush struts/ shocks / springs. The oem front / rear sway bars leave a lot to be desired.

The BMR PHB + brace works superb. I later replaced it with the WL watts link, which works even better.

I suspect your car being a 05, has the various oem rubber bushings long gone trashed.... it's now 13 years old. How many miles on it ?
 

a-train

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My low mileage 2006 just got a refresh...

I run American Muscle Deep Dish Bullitts 18x9(F) and 18x10(R) with 255/45(F) and 285/40(R) tires. Everything else suspension wise was stock.

I just did the following within the last few weeks...
Tokico HP struts/shocks
FRPP Street Springs
FRPP Upper Strut Mounts
FRPP Jounce Bumpers
2005-07 Mustang GT -2 Camber Bolts
Roush Adjustable Upper Control Arm
Roush Lower Control Arms
BMR Adjustable Panhard Bar

Then got a fresh alignment.

The rear end seems so much more solid now. I'm in the Pittsburgh, PA area and on sections of road where the back end use to get all unsettled...smooth as can be now. The rear end suspension work did wonders for the car.

I also added cams and exhaust too. While I love the extra power, I'm happier with how the suspension turned out. Night and day. The way the car should have come from the factory.
 

tw557

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My Gt has 80000 miles .I have no idea when the shocks and springs were installed. They look like new. I just went under and looked everything over and tried prying around on the joints with a pry bar. I really didnt see much movements. I put a new bmr brace on I got dirt cheap. I figured it really can't do much over stock. I was surprised to feel a little more firmer sway. I guess I'll keep chipping away at upgrades. Not sure I can justify a Watts link but I'll try control arms, panhard bar and sway bars. I'm wondering if maybe I didn't put on firm enough tires even though I felt this with the stock gt500 tires too. I also am less concerned with power upgrades as compared to a sharp handling. Since not a daily driver it is a fun project car to try these suggestions. Thanks.
 

RocketcarX

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My Gt has 80000 miles .I have no idea when the shocks and springs were installed. They look like new. I just went under and looked everything over and tried prying around on the joints with a pry bar. I really didnt see much movements. I put a new bmr brace on I got dirt cheap. I figured it really can't do much over stock. I was surprised to feel a little more firmer sway. I guess I'll keep chipping away at upgrades. Not sure I can justify a Watts link but I'll try control arms, panhard bar and sway bars. I'm wondering if maybe I didn't put on firm enough tires even though I felt this with the stock gt500 tires too. I also am less concerned with power upgrades as compared to a sharp handling. Since not a daily driver it is a fun project car to try these suggestions. Thanks.
The swap bars aren't necessary, they will on increase ride harshness on a street car. The control arms are the best place to start to nail the rear end down if the shocks look nice.
 

tw557

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Yeah I'm not too concerned about the sway bars. I don't have an issue with lean. Just rear swagging. I figured lca's were just for wheel hop and acceleration issues. It's just weird. I can push sideways on my suv or old saturn and get them to swag back and forth a bunch but don't feel it on the road. But they do lean a lot more then the gt. I had wondered does the camber that IRS has help with the swagging also.
 

RocketcarX

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Yeah I'm not too concerned about the sway bars. I don't have an issue with lean. Just rear swagging. I figured lca's were just for wheel hop and acceleration issues. It's just weird. I can push sideways on my suv or old saturn and get them to swag back and forth a bunch but don't feel it on the road. But they do lean a lot more then the gt. I had wondered does the camber that IRS has help with the swagging also.
an IRS would have less "swap" because the links run perpendicular to the road instead of parallel. Side to side instead of from to rear like a Mustang.
 

tw557

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I took a ride on my one road that has some 2 ft wide sink seams from where they put drainage pipes. The rear hit so hard as i went over them at speed. The ecoboost is fine. It is lowered about 1.5" also. I did check and I have only about 1.5" bump stop clearance. I already cut the top head off. Can I do more? I'm still surprised the panhard brace helped a bit on that twisty road.
 

Norm Peterson

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What tires have you had on your S197? Mfrs and tire models, please.

One thing you may be feeling is a consequence of staggering the tire sizes. Your rear wheel & tire setup is not as stiff laterally as the front, so you could be feeling "relative movement" due to sidewall distortion, where the rear wants to move more between the wheel and the ground than the front does.

Personally, I think your car is too low for good/great handling over the wide range of road conditions you're likely to encounter. And I think you'd be better off on your '06 with a top-shelf set of 255/40's all around.

It's deja vu all over again for me here . . .


Norm
 

tw557

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Norm,
I have gt500 9.5" 19 wheels with 255 40 on the front and 275 40 Bridgestone RE970AS. This is certainly a concern I have with the tires. The front are stretched tight and the rear sidewalls are very neutral. These tires got good reviews for handling but I now wonder if I should have gone for summer UHP tires. I might need to try and swap the front to the rear to see how it feels. I did pretty much have this same feeling with the factory GT500 tires that were old and worn though. They were 285 35 goodyear F1's. What springs would you recommend for a slightly less lowering drop and what brand or style of rear lower control arms? I think I saw somewhere you once talked about some arms great for the strip but could bind up in the twistys.
 

Norm Peterson

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Let me start with the notion that terms like "stretched", "squeezed", "pinched", etc., should be defined with respect to the tire size's measuring width wheel rather than visual appearance (which tends to be subjective). On that note, I'll go along with the 255's being stretched (only slightly so; I wouldn't be the least bit bashful about putting 255/40's on max-recommended 10" wide wheels)

For your 275's, "neutral" is a pretty good description as long as you realize that that implies a more balanced combination of driving/riding factors then what you're chasing as soon as "better handling" is what you really want. The 285/35's should have been inherently stiffer laterally than the 275/40's, but on 9.5" wide rims they were half an inch below measuring width, which gives away some of that stiffness.

It's possible that in rapid maneuvers, you're hitting the bumpstops hard enough to spike the load on the outside tire, which would make it run at a higher slip angle. That's separate from the older tires perhaps being heat-cycled out.

Your tire choice probably needs to consider whether or not this car needs to be driven in cold weather (or snow), and whether or not you're willing to run one set for "3 seasons" and a second set for the winter.

In a corner, the car will roll (duh), while the axle more or less doesn't (actually, it does "roll" a little due to load transfer compressing the outside tire a bit and letting the inside tire un-compress from its static weight position). This difference in angle needs to be accommodated in all three rear control arms, preferably without inducing large loads and greater load transfer. The OE solution is soft rubber bushings with shapes (and holes /voids) that permit this motion without developing much force. Anything stiffer needs to allow all of the sliding and rotations between individual components inside the joint.

Right now, my car has BMR's handling spring kit that was specifically for GT500 applications (about 20 ln/in stiffer than their current GT/GT500 handling spring kit). And I did shim the rear up by about 3/8". For rear LCAs, I've got a set of Currie 'Currectrac' LCAs that feature a Johnny-joint at one end and polyurethane at the other. I DIY-modified the poly to make the arm work even more freely. www.scandc.com if you're interested and if Marc can still get them (he's mostly a GM intermediate guy).

I'm going to try to avoid typing things twice.


Norm
 

46addict

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These tires got good reviews for handling but I now wonder if I should have gone for summer UHP tires.
I'm seeing this "UHP" acronym being mentioned here and elsewhere on the internet. I don't know if Tire Rack's tire categorization has gotten contagious or if this is the new way of labeling tires now. But going by this scale I would not stop at "UHP" if summer tires are in the cards. Go with "max performance" if you're looking for tires that perform.

What springs would you recommend for a slightly less lowering drop and what brand or style of rear lower control arms? I think I saw somewhere you once talked about some arms great for the strip but could bind up in the twistys.

What Ford Racing springs are on it now? The P-springs are rated for 1" lowering front and rear. Steeda Sports will even out the stock rake, with 1" lowering in the front and 1.25" in the rear. Control arms with poly bushings on both ends will tend to bind up while cornering. So guys typically recommend poly bushings on the chassis side and rod ends on the axle side.

I guess I'll keep chipping away at upgrades. Not sure I can justify a Watts link but I'll try control arms, panhard bar and sway bars. I'm wondering if maybe I didn't put on firm enough tires even though I felt this with the stock gt500 tires too. I also am less concerned with power upgrades as compared to a sharp handling. Since not a daily driver it is a fun project car to try these suggestions. Thanks.

With your new shocks and the addition of a panhard bar, I can't see the other items helping much with the lateral slop you're talking about. The next step would be to add a Watts link, IMO.
 

01yellerCobra

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How much could a bad axle bearing affect this? Or maybe a worn C clip not holding an axle in place? I know the brake caliper will only allow it to move so much, but could it be enough to cause the floaty feeling?

I only ask because I had a bad hub bearing in my IRS that caused the same feeling. I could tell when the tire leaned over in the turn. It caused some sketchy feelings in the middle of a turn.
 

tw557

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I am afraid that I might have compromised too much on my tire choice. The car never sees snow and rarely rain but will see 30 deg days if the roads are good and clean. Because of the low temp driving at times, decent reviews and a great price I purchased these. The mention of the 275's as being neutral is because not mounted on the rim they measured right on 9.5". Sidewall felt reasonably stiff. The odd thing is I can push back and forth on my SUV or old saturn at the trunk and really get is swaying in the garage. The mustang barely moves. On the road the suv and saturn don't have that swagging feeling but the whole vehicle is leaning side to side and the front feels soft. I might just bite the bullet and get some Max Performance tires and put these up on Craigslist.
The springs I have are the "K" springs. I could put a spacer on top of the spring also. It would help with my hitting the bumpstop issue.

Norm, I will look into the springs and lower control arms you have mentioned. I will need to look over the website you mentioned above and I am always into DYI mods. The control arm selection for road handling is probably my biggest area I was looking for advice before I just went out and bought the cheapest most solid arms and then felt other issues arise. Then I'll start thinking about what shocks will work. There is such a contrast of what I hear works for some and not others. Some love the strange 10 way adj and others only love the Koni yellow. And then all the non adjustables in between. At least I'm not bored with the car, always something to try. One day I'll get this right.
 

tw557

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How much could a bad axle bearing affect this? Or maybe a worn C clip not holding an axle in place? I know the brake caliper will only allow it to move so much, but could it be enough to cause the floaty feeling?

I only ask because I had a bad hub bearing in my IRS that caused the same feeling. I could tell when the tire leaned over in the turn. It caused some sketchy feelings in the middle of a turn.

This is a good thought. I had this same feeling but to a much worse extent when the rear wheel bearing went bad on my SUV. I haven't noticed any odd sounds or loose feelings as I have done brake pads and put wheels on and off but I wasn't looking for problems either. Ill need to jack up and look a like harder.
 

Norm Peterson

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I have no basis in experience for opinion with respect to Strange shocks, but I am under the impression that their emphasis has traditionally been on drag racing.


Norm
 

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