i have a redline mxII with a ding in the top tube. any clues on how i could repair this before i have her rechromed?

Weld it in, grind it down, sand it smooth.

One of my dad's streetrod buddies has a tool that spot welds a "nail" to the bottom area of a dent. Then a slap hammer is attached to the nail and the dent is pulled out. After the dent is sufficiently pulled out, the nail is removed simply by snapping it off.This is probably the best dent removal process I've seen. Also, there is a program on TV called "American Hotrod" and it shows Boyd Cottingtons' crew using this tool. I've never used it for pulling a dent on a bike frame, but I will soon.

I'll post how it works when I try it out.

i could easi;y weld it up at work but am concerned about distortion etc. i like the sound of the slide hammer method. i think i will investigate this ( obviously on a much smaller scale than the rodder guys). cornfed, let me know how you go when you try it.

dont think the slide hammer gonna work those tools are for sheet metal not thick tubing like bike frames

cornfeds idea works perfect, i just had 5 dents taken outta my rl2011 using that same method
graeme

Fill the dent with Silver Solder. File then sand it smooth, then hit it with a scotch brite pad and send it out for replate....Good as new!

Here are some old school techniques for the repair. On the opposite side of the tube drill a tiny hole unless there is a vent hole already.Rosebud tip the area and use compressed air forced thru thevent hole it will pop it out. Be sure to have the dent facing directly toward the ground as the gravity tends to help in addition to the compressed air.It take skill but it works every time no distortion and you could scotch brite the rainbowed heated area.It is probably the pimpest technique ever done to tube work.You have to really work with metal that stress these kinda techniques to know .Just a good welder would never know even if they own their own shop.these techniques stem from aircraft builders aerospace.these techs were handed down from family members being in that kinda industry.Make sure you use the proper oxy acy gas mix never put the acy past 15 psi as it is very unstable also use the proper rose bud.i do not know what people on the board here have for equipment so the setting I would tell you will vary per brand holes in the tip etc. Good Luck and you will probably want to try it on some tube the same thickness with the ends sealed up.This will build your I got the balzs to attack it on the real deal.

Lotsa good ideas in this thread...here's what I have tried...
First, use a straight edge to determine if the tube IS BENT, and not just dinged, by placing it on the backside of the affected area. If it IS bent maybe none of what I'm gonna tell you will work given the gauge of most BMX tubing.
The stud welder idea others have expressed works to a point but the pins are weak (being intended for sheetmetal) and usually break off before an adequate pull can be reached. Better to use a spot welder (like a LENCO) with a "washer welder" attachment. This allows you to spot weld a 1/4" hole washer to the surface and use a more conventional slide hammer that does'nt slip to effect the pull. The washer also has a little more contact area which won't hurt. DEFINATELY do several light pulls and don't try to CroMagnon the ding out in one testosterone yank.
Another technique that I don't expect anyone else to know about unless they do bodywork is the "lead pull". This method would work best for larger dings and full-on dents. Take the paint off down to bare metal as with the first method and Tin the surface with a tinning compound from a good autobody supply store. It contains acid so handle accordingly. Once tinned the surface will be really shinney...solder one end of a stick of autobody solder or lead to the center of the dent. On larger dents us body and fender technicians wrap the lead over and form a loop and then solder the other end next to the first end. With this loop you can pull like a MoFo and the "washer" won't pull loose. Your biggest problem with this technique is being able to secure the frame while you're in pull mode.

I would'nt suggest welding the dent in as others have suggested. Often times this causes the affected tube to bend away from the heat source especially if it is slightly bent and you wind up with a concentric tube that's distorted along its length.
There are also aluminum frame blocks that us road bike freaks use to compress a tube round but I'm not happy with the results these produce.

As usual I applogize for my long-winded-as-always replies in this tech column...but the reality is there are generally several ways to accomplish what is essentially a metal working task. That's why there are good and crappy bodymen. I won't ever be accused of telling you what you "want to hear"...hey, there's always our good friend Bondo to come to our aid. Please post what you finally wind up doing so others can learn...even if it was a negative outcome.