[BobSaabit]

For those who added an upper strut bar... without adding anything else at the same time so you can quantity the specfic improvement... did it make a big difference?

I'm thinking of making up one of the types below. It comes out of a UK group where there are a few guys making them up (have been for years now) and they rave about them. It look much more significant than the GS bar from a structural point of view. I'm wondering if it's worth the effort for another incremental improvement i.e. how big is the increment on this one?.

I'll have to pay for the welding since I don't... but I could do the basic cutting and grinding and probably be done at a reasonable cost.

 

[qwikredline]

Here’s the thing. Both Saab and the GM delta small car platform ( engineers learned from SAAB engineering ) have the strut towers close to , and welded into the firewall structure. Strut bars hung off three 8 mm self tapped boats each side in this case are good for hanging decals and making yourself feel important. Look at the E BMW or Gen 6 Camaro with strut towers a lonely pylon sitting in space and you will find factory strut bars. In this case SAAB made such add ones useless. My take. Reinforced by structural analysis BITD

 

[Jeremy R.]

Qwik, are you saying that the NG900 and 9-3 already have a good enough strut bar, or that the design of the car is so crappy that adding one doesn't provide any benefit? I looked up the 6th generation Camaro, and I can see that the strut bars on those cars just connect the strut towers. They don't attach to the firewall.

 

[jvanabra]

I suspect that it's tough to know what the point was most cars. Although there are certain elements to "good car design," trying to infer whether something like a strut bar is "perfect engineering" or "decorative" or some spot in between is borderline impossible without some really advanced tools. I mean, you know GM is a penny-pincher, but I'll bet if they thought the Camaro would sell better with "strut bar look" they'd throw one on without hesitation, regardless of functionality.

I think with the NG900 Saab was trying to make the best of a bad hand and they knew couldn't deliver their experience without a bar... The NG900 was an old budget platform going up against ground-up designs like the 3er and C-class. I'd think that a) if Saab put it there it's 100% critical, and b) once it was decided it had to be there, it was designed to hit the point of diminishing returns (but no further). I'd think "more strut bar" is pushing you past the 80/20 rule, and you'd have to be in a very specific situation to take advantage.

Personally if I had one, I'd probably put it on. But I wouldn't spend a dime to add one. It'd be among the last things I'd consider purchasing, if I'd ever purchase one at all.

 

[qwikredline]

read what I wrote. please. thank you

" Look at the E BMW or Gen 6 Camaro with strut towers a lonely pylon sitting in space and you will find factory strut bars"
"SAAB engineering ) have the strut towers close to , and welded into the firewall structure."

 

[Jeremy R.]

I don't have my NG900 in front of me, but I don't think that the strut towers on the NG900 and OG9-3 were close to, or welded to, the firewall. That may be true of the 9-3SS and the 9-5, but I don't think that's true of the NG900 and OG9-3.

 

[jvanabra]

It's not. The factory bar shares two bolts with each strut and two (IIRC) bolts with the false bulkhead.

The 9-3SS has no strut bar whatsoever … probably because it's a properly designed unibody. OH SNAP!

 

[qwikredline]

My reference is the picture in the OP

 

[qwikredline]

Btw bolts make for a lousy joint anyway and ( again picture only OP for reference ) the bolts on the strut mount are weak although the design of the bar in the picture anchored in the firewall is good practice Overall In the OP picture that strut bar is a waste of effort imho

 

[jvanabra]

That's a modified stock NG900 bar. Not sure where it comes from... maybe GS?

 

[BobSaabit]

I don't have my NG900 in front of me, but I don't think that the strut towers on the NG900 and OG9-3 were close to, or welded to, the firewall....

Correct: The NG9-3 at least has them up against the firewall. Instant bar.

That's a modified stock NG900 bar. Not sure where it comes from... maybe GS?

Yes, modified stock bar. Some guys in the UK are making these up ad hoc. Not for sale except to friends. GS's bar is a little different and has less structure:

 

[BobSaabit]

I drive a 'vert. I haven't yet installed my subframe brace (very soon). See below for what the edges of my fenders look like from body flex. Note that the hood to fender gap is 4-5mm, yet it clearly must be closing from flex. So, maybe I need to figure out some way to measure this movement, see what the subframe brace does to reduce it, and then see what an upper brace can do. If you drive a vert then you know about the cowl shake... apparently it's more movement that I'd ever guess.

I did some reading over the last couple hours. Our strut design is going to transfer all the load directly to the shock tower as you hit road imperfections (or even just corner... but I don't think you hit those limits on the public roads). But, a bump is going to turn the tower into a spring of sorts, denying the suspension the chance to handle the road and moving the wheel/tire off the pavement or to a less favorable position. So if the upper brace helps stop that by sharing the load to the other tower, it would be good. Meanwhile, I still have my cowl shake issue. Don't know if it will help with that.

I think the best location for an upgraded brace would be a bar across the engine attached to the front & top of the strut tower (best) or welded to the front of the other bar. Since the factory bar is bolted to the firewall, you'd gave a nice triangulation of tower position. Unfortunately the engine is sort of in the way, so it might not fit and/or it might have to be removed for some services. Still, if it had to come off to remove the valve cover... no big deal.

 

[jvanabra]

Personally I am dubious that anything you can reasonably do to the front end will fix cowl shake. That's a byproduct of not enough structure behind the windshield, not a lack of structure in front of it. The c900 had massive sills to combat cowl shake, there was no additional structure up front compared to a hardtop.

Scuttle shake - Wikipedia

en.m.wikipedia.org

The strut bar and (I assume) subframe brace are there to help the front suspension work right... Prevent camber changes that are so dramatic with the NG900 body.

I know Nick claims his brace does reduce cowl shake, and maybe it does by improving the connection between the front of the car and the front bulkhead, but I think at best what it might do is reduce the little shakes in exchange for making the big ones worse as they will be FULLY transmitted to the weakest part of the car.

 

[BobSaabit]

I agree with most of what you say... but if the cowl shake is attempting to move the bar and the bar is connected to the firewall (a rigid structural member, then it should fight back and reduce shake.

I know people have reported reduced cowl shake after adding one or both of these, but what that really means, I don't know. If it feels like less shake and it's more stable, then it hits the goals. Maybe that's accomplished with less side to side changes via reinforcement. A stiffer suspension is improving handling but making this problem worse when you hit larger bumps.

But obviously nothing is going stop the car from bending in front of the firewall. In fact, after putting my NG900 'vert on jack stands I found that the doors didn't close properly (windows hitting the roof seal). The body was bending in the middle. The 9-3 doesn't seem to suffer from that but I'm not sure why - I don't know that it has anything more substantial in the rockers.

I'll do some highly subjective testing and find a good washboard curve area if I can to do some pre brace testing. Then I'll do the subframe brace. Eventually I'll do an upper brace and check again.

If anyone has any ideas on how to scientifically test movement while on the road, sing out. I'm thinking that maybe aluminum foil scruched to fit in the side hood gap might be a crude way to measure... it should compact down to almost nothing in the current config in view of my paint damage. With a brace, perhaps it will compress less. But, maybe there's a substance that would better measure that gap closure. With a lot of time and learning I could light beams and sensors to measure inner fender to inner fender movements, but it's not worth that time. Also, it took a lot of miles to get where it is - it might not compress except on the largest of road issues.

 

[BobSaabit]

Oh, there is this scheme if you want to really fix a 'vert:

 

[jvanabra]

I think you have something else going on... I have had a lot of 9-3 convertibles and never seen that sort of interference. Remember cowl shake happens because the firewall (and windshield) are disconnected from the seats and passenger compartment.because there is no roof to triangulate them together. The hood should be moving in lockstep with the front end (and windshield). That it isn't suggests it's misaligned or the hood or front pin is sloppy.

 

[BobSaabit]

Jvan: Interesting points... but it is evenly aligned. The car has never been in an accident. It's not a rusted (weak) unibody. The only thing I can think of is perhaps the hinges allow too much movement. I'll check that. I thought it might be the stiffer springs (they may increase the front end flexing as the suspension doesn't absorb as well). But it was already wearing in that area before I put stiffer springs in.

Looks like it's time for a poll!

EDIT: The flex of the front end unibody on these (up and down, side to side) is well known... when the load hits on one side, you're going to get twisting. Nature of the beast... and the reason some people say the subframe brace can't help much. But, I think it helps reduce the side to side variances... and fixing the unibody requires that body long brace above.

 

[BobSaabit]

Hey Jvan: A quick check just found that one of the rubber bumper dohickeys that keep the hood buffered closer to the hinges is subtley broken. Maybe the hood wear is a symptom of that... fermented by the cowl shake. I will replace it and see if it reduces movement.

 

[BobSaabit]

Update on the hood wear - Fixed the upper rubber thingy. But, the plastic clips near the front of the hood were still in place and looking good. I don't think there's any way the hood is actually contacting the fender. Also, there's no wear on the hood surface, just the fender edge so I can't imagine it's abrasion from the hood. It's got to be some kind of weird road wear... dirt coming up and abrading in that groove via road winds or something like that. So, that's a false indication of anything.

On the idea of a bar, it really looks like there's room for a triangulated third bar across the front of the stock strut support. The stock bar takes a little upward hike coming off the left tower and I think a bar running straight from that height would clear the intake pipe. It might have to make a little bend around the oil cap. It would also have to come off to service the intake pipe, but in view of the number of times I have to do that, I'm not concerned. As an alternative, perhaps it could be bolt on to the stock bar.

 

[qwikredline]

A couple of things. Convertibles are a big issue. Imagine this: take a cardboard box tape it up. Pretty decent structure. Heck you can even ship things in a box that way and the stuff arrives Un damaged. Now take that “box “ and cut a hole for the radiator. Slit the rear of the box for a trunk. A few slits on the sides for four doors. Box is looking pretty darn weak. Now cut the top off. It’s a convertible. Your box btw is junk.

now consider that convertibles are generally made off sedans and the engineers do their best. But it’s not an easy task. Many convertibles run huge X braces underneath. C4Corvette for example. That red bracing I bet helps that convertible.

Another thing no matter how good the structure is the day you drive the car off the lot brand new that structure is wearing out. SAAB did a darn decent job on structure. It crash tests very well. But impact crush structure and torsional rigidity are not friends.

strut towers welded into firewalls don’t need strut bars.IF they worked and provided torsional resistance the strut bolts would break off. Just as an aside.

a Saab 9.5 has front fenders that are so soft in vertical load you can bend them up jacking the car if the jack plate catches the lower fender. If that happens it’s an easy fix: press vertically dorm on the fender with the hood open. FIFY.

the best you can do is avoid potholes keep your suspension in good order renew OEM subframe bushes and stay away from poly bushes. Convertibles ? Only drive on dry sunny days. Last longer that way

my take