Seam Welding vs. Cage...

[winstontj]

The more I get into this madness the more I realize that putting a cage in a perfectly good sunroofed roundie that will never see the track is a bit foolish. I do however want to stiffen & strengthen things up as much as possible as well as reduce a bunch of weight. I am only considering the cage because I see it as a safety device and a way to keep the car together if I reduce weight, add power, etc.

How much does seam welding help? If I were to seam weld most of the chasis and strengthen areas like shock towers & rear subframe & diff mounting points will that make a huge difference over stock? The car is going to need a bunch of work to get it into acceptable condition so I'm not opposed to doing a few mods like welding in rear strut bar or reinforcements.

Does anyone have any experience with both seam welding AND a cage - and how much of an improvement does just seam welding offer? Should I consider a half cage or is that a total waste of time? Back seat is not important but I would like to have the space where the back seat was.

Thanks all...

[bmw1602.com]

yes i did seam weld my car before it got the cage.

i'd have to day it would help, along with the cabrio braces in the front.

.........but a cage or a roll bar you would feel ALOT more.

it makes a huge differnce.

[racebmw]

I agree, but it depends what you want. My car is a full-on GT 3 race car.

My car is seam welded and has a full cage and it is very stiff.

Stock 2002's are very flexible, notice how poorly the doors fit when you jack on the stock jack points.

For a suspension to work properly it has to have a stiff structure to work against. Otherwise all the upgraded suspension does is make the car flex more.

My Alpina had a roll-hoop in it that went behind the front seats and tied into the seat belt mounting point on the door pillar. It helped a bit but if you want to do a major suspension upgrade you need to tie the pick-up points into something stronger than the body.....

Of course if you just want a nice street car - don't waste your time.

[winstontj]

I agree, but it depends what you want. My car is a full-on GT 3 race car.

My car is seam welded and has a full cage and it is very stiff.

Stock 2002's are very flexible, notice how poorly the doors fit when you jack on the stock jack points.

For a suspension to work properly it has to have a stiff structure to work against. Otherwise all the upgraded suspension does is make the car flex more.

My Alpina had a roll-hoop in it that went behind the front seats and tied into the seat belt mounting point on the door pillar. It helped a bit but if you want to do a major suspension upgrade you need to tie the pick-up points into something stronger than the body.....

Of course if you just want a nice street car - don't waste your time.

Of course I want what I can't have... the best of both worlds. I may look into a half cage/hoop OR just seam welding, stiffening and really beefing up suspension mount points.

How much does seam welding stiffen up a shell? Is it noticable? Worth it?

[racebmw]

My racecar was already seam welded and had a cage when I bought it. So I can't comment on the difference that seam welding alone would make.

All I remember is thinking the racecar was unbelievably stiff compared to my street 2002 Alpina. The street car was very flexi compared to the racecar.

Remember that 02's were designed before R compound tires existed so they were never intended to have the kind of suspension loadings we take for granted today.

Today's R compound tires have more grip that 1970's racing tires did.

So if you are going to put R compound tires on the car and track it I would do something about stiffening it. If you aren't going to do any of those things then just leave it.

Drive it, enjoy it

Jeff

[TMK-001]

How about if I run something like Ground control coils, stregthened front and rear subframes, strut tower braces, standard rubber bushes... should I stress about too much flex? I just spent a mint on paint and want a good fun street car that I can take for a rip on the track when I feel like some fun - I dont want cracks and saggy doors after giving it a fair go on the track...

Cheers,

Todd

[racebmw]

I think you will have lots of fun with your car as it is as long as you don't put really stiff springs in it. Relatively soft springs combined with stiff sway bars are a great compromise for most tracks. Teaches you to be a smooth driver too.

The only time you will notice a problem is if you should get in a car that is seam welded and has a cage. Then you will realize there is a whole other world of handling possibilities. But the car is no fun to drive on the street after you do all that stuff. So just enjoy your car....

Jeff

[Marty]

There's a real good thread on seam welding right now on WWW.Hobartwelders.com dealing with the various techniques and how to clean embedded seam sealer out of the joints before welding.

[NickVyse]

There's a real good thread on seam welding right now on WWW.Hobartwelders.com dealing with the various techniques and how to clean embedded seam sealer out of the joints before welding.

thanks Marty. Here's a link to the actual thread:

http://www.hobartwelders.com/mboard/showthread.php?t=24465