sorry for not explaining myself correctly...you are right...it is for stiffness...by decreasing the distances between each weld (whether spot weld or not) you increase chassis rigidity. This can also be achieved using a cage, but it is bloody hard to build a cage around the front end. Thus seam welding is usually done around the front of the car, in and around wheeltubs, while the primary source of stiffness is a cage. You cant go past good seam welding, as a cage by itself or even stiff suspension can still tear seams apart.

i started this topic a while ago and now ive learnt not to do seam welding yourself, my mates mazda rallycar was done at home and everything was welded continuosly (no gaps), well when i managed to stack his car there was no play in the joints and instead of the front simply crumpling, there was bends in the inside panel and even at the base of the a-pillar and this wasnt excatly a huge impact, i sort of slid into a ditch and hit a log that was lying accross the bank on the other side of the ditch, the front corner was punched in and now we are cutting out a new front corner to weld onto his car, but anyway i reckon with all the joins being so rigid the force has been transmitted further into the car and rather than loosening up and bending joints, these are now too strong instead the material bends in funny places. ive since been told that you should never seam weld in front of strut towers, so this area acts as crumple zone, and the idea raised before about increasing number of welds and length of them rather than welding up everything sounds like a good suggestion too.

the 'proper' way of seamwelding, as andos said, is the weld about an inch then leave at least an inch and a half gap.

Chris I actually did do a bit of seam welding before I painted it white It was a pain to do as had to get rid of all the old paint ect. I basically just did around in my engine bay to stiffen up the struts and swaybar mounting and engine mounting ect. I didnt go overboard. My car has some cracks in the body nothing to major just the lead joins on the rear quarter to roof and top of front windscreen stiff susspension and circuite racing does it i have both my front and rear screen urethaned in to stifen the shell also teh 6 point cage makes a huge diference driving without either the strut brace or roll cage it feels very sloppy well compared to what im used too.
cya next week at the nationals (if its going)
Cheers Andrew

Does everyone agree that the benefits of seam welding outweigh caging and bracing of the car....I guess it would mean weight is reduced maybe??? By way of less bracing matrerials I dunno... just a wondering

Andrew are you still circuit racing??