Stiffening Chassis on a gen3 or 4 roadster SRT10

[Aevus]

Hello everyone,

I'd like to have your input on possible solutions to get a stiffer chassis on the gen3 or gen4 convertible.

At this moment, I have ACR's sway bars front and rear and coilovers with Swift springs (front 12kg/mm + rear 14kg/mm rates), poly engine and trans mounts, car has 36,000miles and still feel pretty tight for a 2005.

However, I think there is some flex coming from the chassis (little flexing sounds with one wheel on a curb) and most importantly it feels a bit soft on the racetrack and I don't feel it's because of the suspension or the bars, but I might be wrong of course...

So is any of you have experience on the topic?

[JonB ~ PartsRack]

Your stock coilovers assumed, at 15+ years and 36K miles are softer than OE.

And remember OE 03-06 G3 shocks were designed a bit softer for OE stiff-sidewall RUN CRAP TIRES.

Coilover time?

[ViperSRT]

Your stock coilovers assumed, at 15+ years and 36K miles are softer than OE.

And remember OE 03-06 G3 shocks were designed a bit softer for OE stiff-sidewall RUN CRAP TIRES.

Coilover time?

Jon the springs he quoted are pretty stiff. 670F and 780R lb/inch. Doubtful any concerns are due to the coil overs, assuming reasonable damping settings.

[Steve M]

What is your intended application for the car?

If it is just going to be a race car, you could add a cage which I'm sure would stiffen everything up. Beyond that, I'm not sure what you'd realistically be able to do that would make a difference.

You have to keep in mind that the Gen 3 was only available as a convertible until 2006, so the frame was already made to be plenty stiff enough to accommodate. It is also not a unibody car, so things like subframe connectors like you'd see folks use on older F-bodies and Mustangs to stiffen up the chassis won't apply.

The frames on these cars are pretty beefy IMO...yeah, there's going to be at least some flex in there, but definitely not as much as a unibody car. On my old Camaro (unibody construction), if you lifted the car near one wheel, only one wheel came up off the ground. When I do the same on the Viper, both front and rear tires come up off the ground.

I'd check to make sure things like the belly pan fasteners are all tight...basically do a nut/bolt check with the car up in the air to make sure nothing is loose under there.

[Aevus]

BC racing co's
installed 3-4 years ago, less than 15,000 miles on them.

I know I could (should?) upgrade to 3 or 4 way adjustable co's but it's a roadster, not some drag or racetrack beast

[Aevus]

What is your intended application for the car?

If it is just going to be a race car, you could add a cage which I'm sure would stiffen everything up. Beyond that, I'm not sure what you'd realistically be able to do that would make a difference.

You have to keep in mind that the Gen 3 was only available as a convertible until 2006, so the frame was already made to be plenty stiff enough to accommodate. It is also not a unibody car, so things like subframe connectors like you'd see folks use on older F-bodies and Mustangs to stiffen up the chassis won't apply.

The frames on these cars are pretty beefy IMO...yeah, there's going to be at least some flex in there, but definitely not as much as a unibody car. On my old Camaro (unibody construction), if you lifted the car near one wheel, only one wheel came up off the ground. When I do the same on the Viper, both front and rear tires come up off the ground.

I'd check to make sure things like the belly pan fasteners are all tight...basically do a nut/bolt check with the car up in the air to make sure nothing is loose under there.

Ok, thank you Steve for the tips

[Aevus]

Yes I had the somewhat low quality springs that comes with BC racing kit (10/12kg) and replaced them with Swift 12/14kg and I'm very satisfied now. Somewhat firmer but comfier than before. I wouldnt go with stiffer springs though, unless I have 3/4 way adjustable co's

[pokeyl]

This will help.
https://driveviper.com/forums/threads/25244-RPM-Roll-Bar-Install?p=396688#post396688

[txrunner]

These cars are roadsters (built to be convertibles) so the frame is plenty stiff unlike traditional convertibles (start as a coupe). I can jack up one side & lift the front wheel up with little / no flex.

**Just re read your post & see that you are tracking the car so your needs are different. Sorry for the post***

[TKO MOTORSPORTS TEAM]

The roof on a viper doesn't really do much because there isnt much there ,so convert or coupe the chassis stiffness isn't going to change all that much. The chassis stiffness on the viper is ok to start with adding a properly designed and built cage does help. If you track your car alot a cage is a very good idea but does kill the idea of c convertible. Your probably not feeling chassis flex at the track. More then likely its shock dampening, springs, and control arm bushings. Really comes down to what exactly you feel and what the car is doing and then make changes based on that.

[pokeyl]

I can hear the 6 point bar lock up under cornering loads. The swing out arms are loose and rattle under no load.
It's only a tiny amount and I am not good enough driver to feel the difference.

I can feel tire pressure changes/alinements and adjustment to the Moton shocks. As stated above!

[TKO MOTORSPORTS TEAM]

I can hear the 6 point bar lock up under cornering loads. The swing out arms are loose and rattle under no load.
It's only a tiny amount and I am not good enough driver to feel the difference.

I can feel tire pressure changes/alinements and adjustment to the Moton shocks. As stated above!

If your control arm bushings have excess play with no load ( at full droop) under load that slight bit of play will be amplified. Since you have some experience on track and can feel shock and tire pressure changes you would definitely feel a difference with new bushings. Control arm bushings and most suspension components kinda work under the old saying "you didnt know how bad it was until it was right".

[pokeyl]

Shoot me a PM for bushings price? Thanks


If your control arm bushings have excess play with no load ( at full droop) under load that slight bit of play will be amplified. Since you have some experience on track and can feel shock and tire pressure changes you would definitely feel a difference with new bushings. Control arm bushings and most suspension components kinda work under the old saying "you didnt know how bad it was until it was right".

- - - Updated - - -

[LCatGA]

Any resolution. I'm looking at the same thing - 2008 Roadster and would like to take handling as far as I can without sacrificing street comfort.
Looking at bushings, adjustable sway bar links and stiffer sway bars. Did anybody tried to build engine compartment crossbrace like in Gen V or adapt Gen V one?
BTW what good streetable coilovers at reasonable price are recommended?

[TKO MOTORSPORTS TEAM]

Any resolution. I'm looking at the same thing - 2008 Roadster and would like to take handling as far as I can without sacrificing street comfort.
Looking at bushings, adjustable sway bar links and stiffer sway bars. Did anybody tried to build engine compartment crossbrace like in Gen V or adapt Gen V one?
BTW what good streetable coilovers at reasonable price are recommended?

Best way to stiffen chassis is a proper cage but if your concerned with comfort a cage might not conflict with your idea of comfort. TKO control arm bushing kit, tko adjustable sway bar links both great idea for performance improvement. Larger sway bars not really necessary the factory sway bars will work just fine. As far as coil overs go you get what you pay for. TKO, Penske are at the top of the list for performance, reliability and customer support. Moton, bilsteins are you next best bet. Stay away from the cheap import coil-over kits