Targa Chassis Stiffening?

[AZAirCooled]

What options are available to stiffen the "chassis" on a targa?

I am not building a race-car for the track. I might never even put it on a track (did that when I was younger). Just looking for improvement on the street. Occassionaly, when no one is looking (hopefully), I drive it like it was on a track.

Putting a roll bar in the car is a last resort for me and I might even rather have the flex. However I would consider one depending on the style. Street car remember. For example I have chosen rubber spring plate bushing replacements.

I am already aware that I could sell the car and buy a coupe so any open-air haters/"bench racers" can keep that one to themselves.

Thanks,

Bob

[Danny_Ocean]

I have seen cabriolets with a bar mounted across the rear passenger compartment, just behind the driver/passenger seats. It looked very similar to a trunk-mounted strut bar.

[attamz]

Our host sells a targa body brace which is supposed to do something along these lines. I have never used one so I can't tell you how well it works.

[wwest]

Targa, stiffen...??

My '78 seems more than "stiff" enough.

[AZAirCooled]

I also have a 1993 Mustang GT convertible that I had "sub-frame connectors" welded on. It greatly reduced the "chassis" flex.

[lindy 911]

I think a roll bar / cage is the only real option. You might want to do some research on this topic as one very respected race driver actually preferred the flex of the Targa to the handling of the coupe. Just a thought.

Lindy

[na2ub]

Best bet is to box the rockers. There are some picutures floating around here, but basically this stiffens the longitudinal rocker area by welding on some additional metal from the footwell to slightly behind the door jam, along the inside rocker. This stiffens the middle of the car, where it is lacking stiffness. I will probably do this myself one day. Other than a full cage, I don't really see any other way to significantly stiffen these frames.

[5:04]

Originally Posted by na2ub

Best bet is to box the rockers. There are some picutures floating around here, but basically this stiffens the longitudinal rocker area by welding on some additional metal from the footwell to slightly behind the door jam, along the inside rocker. This stiffens the middle of the car, where it is lacking stiffness. I will probably do this myself one day. Other than a full cage, I don't really see any other way to significantly stiffen these frames.

this helps a lot, it has the same effect as seam welding but without having to strip thr car.


This is similar to what na2ub is talking about if I'm not mistaken.


The best option is to reinforce the frame rails. This would make a night and day difference.

[TroyN]

As noted the only way to really stiffen a targa are a cage (at least a 6 point, the 4 point won't do much) or frame reinforcements. I felt a noticeable change after putting in a strut brace and a harness bar that tied the 2 b pillars together. I did those targa bar braces and they made no noticeable difference for me.

[Doug&Julie]

I know it defeats the purpose of a Targa, but has anybody done a permanent connection between the Targa bar and front windshield? ..effectively making the Targa top a giant, removeable sunroof? Would this make a majore difference or is there still too little structural support between the Targa bar and the lower body?

Thx.

[AZAirCooled]

Best bet is to box the rockers. There are some picutures floating around here, but basically this stiffens the longitudinal rocker area by welding on some additional metal from the footwell to slightly behind the door jam, along the inside rocker.

This sounds like what I (old car guy new to old 911's) would think needs to be done. Its the front to rear structural rigidity that is comprimised in a Targa or cabriolet. The "Fox" body Mustangs are uni-body and Ford rivited in rocker reinforcements on convertibles. But it was not enough. The "sub-frame" connectors that guys welded in connected the front "frame rail" in the pan to the rear one on each side. These old 911's weight less and the floor pan is much narrower so mabye reinforcing the rockers only is enough. I searched this forum for "box the rockers" and didn't find it/them.

Anybody know of how -to threads, photos, or aftermarket "fixes" that have been successfull?

Thanks, Bob

[TroyN]

I'd had a similar thought. I used to track my targa and would notice a pretty big difference in stiffness even with the stock floppy top on or off (I always tracked w/ it on) so I bet if you could figure out a way to mount some kind of x brace or such between the header and the targa bar that would help a lot and avoid having to do a full cage.

[500_19B]

This is a post in a thread on structural reinforcement that might be of interest (it shows inner sill reinforcements):

Structural Reinforcement

[tcar]

Originally Posted by Doug&Julie

I know it defeats the purpose of a Targa, but has anybody done a permanent connection between the Targa bar and front windshield? ..effectively making the Targa top a giant, removeable sunroof? Would this make a majore difference or is there still too little structural support between the Targa bar and the lower body?

"Too little structural support between the targa bar and the lower body?"

No, plenty, it's a real, live roll bar.

Ideally targa bar to windshield top is the best idea if you could. To add a 'roof' structure. You'd probably want to put in a diagonal or an 'X'.

Or a cage would do the same thing.

The problem with the targa and cab is that there's no structural link between the front suspension 'tub' and the rear suspension 'tub' except the pan.

Boxing rockers can make the pan a little stiffer, so that helps a little.

A strut bar in the front (or the rear) doesn't help this.

Pelican's 'Targa body brace' actually helps slightly; it's noticable.

I keep thinking there might be a way to make the targa top somewhat structural. Stock, there's a slight bit of compressive resistance, but zero tensile (those are just pins on the back edge of the top and side latches at the front. If you could put real 'pull' latches on the front and rear of the top and a diagonal in the top, it might actually help.

My restored 69 VW beetle vert was a little stiffer with the top up than with it down, I'm guessing due to some (a little) tensile resistance.

Anyway.

[AZAirCooled]

The problem with the targa and cab is that there's no structural link between the front suspension 'tub' and the rear suspension 'tub' except the pan.

This is what the "sub-frame" connectors (sold by many companies) were on the lowly 5.0 Mustangs. I will be surprised if there is no such fix already engineered for the older Targa & Cab 911's. There were so many available for the Mustangs that there was benefit to researching the best one. I went with weld-in round tube ones (very strong).

[byfdinky]

This is all I thought we need for our Targas

[AZAirCooled]

Our host sells a brace like that. Did you put it in since you've owned the car? Can you feel the difference? Can you see the difference when you jack up the car?

I was thinking something under the car from front to back would be more effective.

Are your rear seat belts factory? Mine doesn't have any.

[byfdinky]

I bought these used on ebay, They do not interfere with the stock seatbelt
mounts. I installed them along with a strut brace when I first got the car. Do not really have a stasting point to compare. It just seemed to make sense to help keep the Targa tighter.

[j911brick]

I race a targa and I have done some experiments with models. As suspected, the weak spot is the drivers compartment, between the doors. Without a full cage you really can't solve this problem. The next best solution is an additional floor and rocker layers (basically doubling the thickness of these sections), but that's not cheap or easy. The factory fiberglass roof is better than the soft roof, but still not great.

[Doug&Julie]

Originally Posted by tcar

"Too little structural support between the targa bar and the lower body?"

No, plenty, it's a real, live roll bar...

But essentially a big hoop with two (potentially weak) bolt in locations (where the Targa bar meets the body) as opposed to, for instance, a welded in cage with X bracing. My concern with welding a connection between the top of the Targa bar and the front windshield is this connection point. I suppose that would be fairly easy to reinforce. Anyway, I wouldn't rely on just the Targa hoop to protect my noggin' if I did any serious track work!