Yes, they tend to crack around the tops of the towers, they bend the bump stop area, & can rip the tie bar mounts backwards
The "Usual" or "Common" method is--->
Re-weld around the tops of the towers, but just "Stitch" weld them,,, (as in Sewing Stitch) as in-->inch weld, inch gap, inch weld, inch gap & so on...stiching helps stop them crack even further if/when they ever crack again (not that they will after you do all this tho)
brace those tower tops with 2 strips of metal that are placed along the front & another on the back of the tops of each tower,,, but long enough so that they can be bent down to meet the "upwards" part of each tower along the "INSIDE" sections,,, if you get my drift??? Doing That tends to stop "ANYTHING" happening to that part of the frames ever again.
it`s a leverage issue,,, the bump stop stops the wheel assy rising up & then the upper inner control arm """levers""" the inner pick up point down wards, pulling the tower down & away from the top caps that are mounted into the body. TRUE!!!
Also weld 2 triangular gussett braces into the tie bar mounts,,,one each side of each tie bar mount. Strong as an ox then & rally till the rest of the car is destroyed.
some people brace along the entire front crossmember too , but i don`t bother unless it`s had a bad whack there,,, &/or someone has been silly enough to hook a tow rope up from there & pull that forward. I`ve seen more than plenty of frames bent like that (doh!!!)
i`ve also known the hard core rally guys fabricate a fairly thick steel plate & weld it to their bump stop areas to help stop it bending & cracking in there as the previous guys photo shows,,, but hey, that`s for pretty hard core off road stuff & not really an issue for road use or even much of a reliabilty for the "Average" rally mini, but still it`s an option if you have issues there.
I`ve seam welded rally frames & speedway frames--> That is to stitch weld all around where all the plates that make up the entire frame meets in all places all over the frame,,, but havn`t bothered doing it for any road or bitumen track car frames at all, no real need as long as there`s 2 diagonal braces fitted, one either side from above the towers (near the shock mounts is good) down to the ends of the front cross members, all that helps torsional rigidity enough for circuit racers. But still, differnt people have different ideas.
I`ve also done seam welding & bracing on rear frames, but mainly for rally minis. Most circuit minis have more metal taken out of them for lightweight-ness (swiss cheese) than added to them
Long live your subframes
