This article is a description of how I set up the March 761 by Fly without a down force magnet.
I purchased a replacement lead radiator kit . This adds weight to the car to enable it to race as a car without any down force magnets .
In the kit is 2 molded lead radiators the same size and detail as the original plastic radiator. Also there are 2 rear tires made of Urethane. There is also a bar of lead which can be used to add further weight if necessary.
The radiator kit is made and supplied by Paul's Urethane tires of Canada. To purchase the kit just search on Ebay for Urethane Tires.
The conversion to a non magnet car is achievable in under an hour.
I removed the 4 retaining screws - three for the body and one for the rear wing. Note how the rear gearbox cover & nerf bar attach to the rear wing. I super glued the cover to the wing as it can flick off other wise.Also take note of the rear disc rotors and where they fit into the chassis. This is a bit fiddly when replacing body. The discs are retained by the stabilizer bar only . the discs have to be in correct position before replacing the body so the stabilizer can slip over them & hold them in place. It is tempting to glue the disc rotors in place but the come off with the rear axle unit . Gluing the rotors would make it difficult to remove the rear axle.
We are ready for the conversion. Remove the rear axle unit from the chassis by snapping the bearings carefully out of the chassis. I removed the tires from the rims. This has to be done carefully or rim damage might occur. I freed tire on the rim by pushing on the tire only to separate from the rim. Do not force on the rim - only on the tire. once the tire is separated place a 3mm flat blade screw driver in from the inside of the tire and leaver carefully on the rim to edge the tire of - do not hold the axle - hold the outside of the tire so no force is put on the hub to axle joint.
Fit the Paul's tires over the hub carefully again do not put force on the axle or the hub can split. The new tires go on the rims easily. Use four drops of Super glue around the inner & outer of the rim by lifting the wall of the tire to expose the rim edge. Apply the glue one position and one drop at a time & seat the tire each time.
I then true the tires as a unit on the tire lathe - this is necessary because of the small rim and large tire combination - all fitted so far were out of round until trued on the lath.
The next step is to remove the down force magnet near the rear axle. Push it to the rear of the car with a screw driver and it will slide out. Store the magnet away in case you need it in the future.
Remove the rear black plastic radiators by wiggling them . They are retained by a small plastic pin which usually breaks . If they had to be replaced they would easily glue back in place so store them away as well.
It is advisable to make a small jig from a block of wood and some nails or screws. The radiators sit in place if you place the body flat on the jig block the nails or screws are placed to hold the radiators vertically and in line with the sides of the body. Once the jig is correct use some epoxy glue to fix them in place. I put a fair bit of glue on the mounting tang and also where it buts up to the body edge. Leave the assembly until the clue is cured,
I did not use the bar of lead - I made a square on 2mm lead to fit in the chassis under the drivers seat. The lead fits between the 2 plastic "rails" that run along the chassis. It also fir between the motor and the display box mount screw hole. It must sit flat on the chassis floor or the body will ride on it.
When the radiator glue is set the body is ready to replace. Make sure the rear disc rotors are in the correct position with their pegs in the chassis hole before seating the body in place.
Replace the 3 body screws the fit the rear wing and gear box cover .
Ready to test. Give the tires a quick sand on 600 grit sandpaper and go for a road test.
The car has a sprung front axle which is a bit weak in the springs. So with maximum tire traction and fast corning the car tends to tip out on sharper corners some times. Without making the front axle fixed you can get away with a lower track power and sensitivity setting on the controller. Also a little less trigger at the bad spots helps. The car should settle down and reduce tipping after the tires loose their initial high traction being new tires. Adding more weight will only work to stop tipping if a lot is added and the car's speed will be reduced. That is one situation where a magnet in the front helps. The down side is that it will be very fast without any drift on corners and not as much fun to drive - the purpose of removing the down force magnet.
Further tuning may have to be done with weight, tires and braid but generally they are nice to drive after the conversion. Have fun & enjoy. - John