subtlez28

iTrader: (15)

So Jeremiah, If I am understanding you correctly...I completely agree.

My way of thinking is the primary time they (SFCs) take force on is during a hard launch, when the floor is being forced to lift the front end. Under braking, then the force should be primarily on the roof and side structures. During hard cornering and bumps when torsional force is applied, SFCs may help some but not make a night and day difference. The only way to really make a big difference in the rigidity of the car is w a roll cage, due to the triangulation used, and the multiple tie in points. Merely strengthening the middle of the floor is NOT the "end all, be all".

I think too much is expected of SFCs as they only attatch to 2 or 3 points. The rear LCA pocket is a good tie in point, especially when it attatches to both sides. But how much can be expected of the relatively small pieces of sheet metal the front and middle points bolt or weld to? Basically they only strengthen one plane. And one plane, no matter how strong, does not resist torsion very well.

I'm not an engineer, and this is mainly my common sense talking. Am I nuts?

Who's with me?

jb442

iTrader: (4)

I'm with ya! I'm definitely nutz. But I have have been thinking about the SFC's and these 'dimples' too.

IMHO, it seems to me that installing SFC's may increase the likelihood of developing these dimples in your quarter panels. Now, before I get flamed , here's my reasoning behind this thought:

Without SFC's and without a roll-cage, the car is not as rigid in the center portion of the chassis so it has some "give". The forces of a drag-launch on slicks, for example, will put a lot of load on the rear and center portions of the chassis. Since the center portion has a bit of "give" it will effectively reduce the amount of torque/load on the rear crush-zone components of the chassis.

With SFC's in place (and still no roll-cage), the center portion of the chassis is stiffer, and will effectively force (or isolate) more load on the weaker crush-zone in the rear of the car, of which the quarter panels are an integral part. The only way I can see around this, as Jeremiah has stated, is to tie in the rear portion using a roll-cage.

Ok... Who's with me on this?

subtlez28

iTrader: (15)

jb442 I'm with you. I am also pretty sure many will disagree (with us).

I didn't know about the crush zones in the rear but it does make sense!

I can see how SFCs would actually contribute to the dimple issue. I also think this increased rigidity in the floor is what makes for the harsher ride w SFCs.

Seems to me SFCs are probly best suited for a drag car as launch energy may be lost as the floor pan gets flexxed a little upon front end lift. The diff seems to me to be minor. But, I'm not a drag racer....pulling a front sway bar for the launch advantage seems way extreme to me. I'd like to see both the front bar removal trick and SFCs tested to see what (if any) gains become of them.

cowboysfan

I belieive you all make good points. my opinion here is installing sfc only stiffens lower car but not above that. example. piece of paper is flat u connect one bar on each side, now picture that been the floor of our f-body, O.K engine/suspension on one end and axle/suspension other end. hard acceleration will lift the front however there will be an arch only cause u are asking the sfc to remain stiff but, it can't support all that wait so cause the applied tq is comming from the rear wheels and quarter panel are part of frame is create a distortion. so w/ no sfc and stock car you get dimples, once u start adding HP/TQ it it will only increase distortion that it will crack upper end of qtr panels. I've seen that from a guy who only installed 3.73 gears and would race on street. so I believe sfc will not stop dimples or roll bars, just the way the car was built is going to happen. can be minimized but not prevented. again just my .02



fuerzaws6

Empatho

iTrader: (16)

I havent checked for dimples on my Z, and if I don't I'm planing on getting a 6 poing roll cage in the near future to help with this problem

RevGTO

iTrader: (12)

I think what Jeremiah says makes a lot of sense. In all the discussion about SFC's, crush zones have not been mentioned, and yet they are designed into every modern car. It would seem to me, though, that if rough roads and the like contribute to the development of the creases and dimples, weight transfer on a dead hook would have the same effect.

As I posted in the other thread, my experience is that I had creases on each of my quarter panels - the one on the right was 9" long. It actually crimped the metal at the wheel well edge; above that it grew more subtle. The one on the left was at a 45* angle to the ground and very subtle, but about 6" long.

I installed SFC's solely for the purpose of curing this and had the car PDR'd. After last season at the track, they have not come back. However, I do have fresh dimples on top of the quarter panels.

The thing I noticed more than anything else after installing the SFC's was a drastic increase in ride harshness. I wanted to uninstall them immediately but cutting through the welds would have been near impossible, and otherwise, it would have left a mess. I had to go to soft tires to compensate.

Although others have said this sarcastically, I'm being serious: the main reason I keep them, besides the difficulty of getting them off, is the ease of jacking up the car with them. If you change wheel/tires a lot, it comes in handy.

fa63

I think I will make an attempt at instrumenting one of my Camaros to see how much deflection occurs in the unibody at certain locations. I don't have SFCs on any of my cars right now, but I kind of want to put an end to this discussion, so I might do a before and after. It would include data from the street, strip and road-race course (Sebring, im my case, which is very bumpy).

I will post up when I get a chance to do this; just finished my graduate work at Georgia Tech and starting a real job soon. A real job will let me have my weekends to myself again, so I hope to do this sooner than later.

01badz28

iTrader: (5)

Here is my $.02 on SFCs:

I had a 1996 V6 Camaro (hard top) for about 5-6 years. It never saw a track, and I kept it bone stock. By the time I got rid of it (around 60K miles) nearly every interior panel rattled, and the car had the rigidity of a limp noodle going over bumps.

When I got my 2001 Z28 (t-top), I drove it for about 10K miles before putting on GW 2 point SFCs. I noticed an immediate increase in the feeling of the car. IMO it felt a lot stiffer, and it cured a couple of dash rattles my car was developing. Now with 60K on the odometer, and three autocross seasons later the car is still very solid. I know the arguments against putting them on the car, but I think mine have made a real difference. They also make for handy jacking points.

Sadly though, my car has the fender dimples. Its not a show car, so it doesn't really bother me.

01pewterbird

Just curious if any of you guys think the way you jack the rear of the car up has anything to do with the dimples. Meaning lifting one side at a time verses lifting it from the center.

RevGTO

iTrader: (12)

Unless you have SFC's you can't really jack from the center ... if you have them, I don't think it matters.

ModGod

iTrader: (1)

Ok....How can I say this and maintain my masculinity??
Can someone please post pics of their dimples?
I'm really struggling to figure out what I'm looking at in the two pics..even after reading the posts a couple times!

Thanks!!

jb442

iTrader: (4)

Do you mean just jacking up the car from underneath the differential? That should have no effect. Jacking up the car one side at a time on the subframe? That might, but I really don't think that would do it either.

01pewterbird

^^ yeah thats what I meant. Because I lift the rear one side at a time and not from the differential, so it had me thinking. Although i think i'll lift from the dif from now on.

Carlos01SS

iTrader: (4)

So check this out, I had 2 dimples on the left rear fender, they were about 2 inches south from the edge of the rear hatch, been there before I bought my SFC's which was about December '04...

I spent the past 2 days off and on polishing the **** out of my black paint, put on a coat of NXT wax, and low and behold, I got 2 MORE dents

ModGod

iTrader: (1)

Nobody's got any more pics???

01pewterbird

Carloss01 I got about a dozen on my driver side and none on my passenger side. They are so subtle that i'm probably the only person who can see them. ModGod, they're so subtle they can't realy be caught on camera.

01pewterbird

[IMG][/IMG]
Here is a shot of the exact area and you can't realy see any. Within that area there are about a dozen or so dimples. Guess its something i'll just have to deal with, no sense getting it fixed if they're going to come back.

Carlos01SS

iTrader: (4)

That's what I'm thinking!!!

I figure I'mma gonna buy that silly suction cup denter popper thang and give it a go, as the indentations are not with wrinkles, so that tells me they should pop right back out if I were to from the inside.

01pewterbird

^^ I don't know if i'd mess with that, could wind up making it more noticeable.

subtlez28

iTrader: (15)

I've read here on LS1tech that people have used paintless dent removal w success on these dimples. But I would leave it to a pro.