Its been a while since I've posted anything F1 specific - been spending to much time and angst switching between TC, F1 and 1/12, but I DID do a little mod to my trusty F109 a little while back and thought I'd finally post it.
The kit side springs in the F109 are woefully soft, the 3Racing option springs not much better, and the other side spring mods I've seen make it too easy to loose the springs. I was going through my parts box from my RM-01 and I found a spare set of the side spring retainers from that car (also on the F104 VrII). I'd read somewhere that when people use Team Associated side springs on the RM that the retainer doesn't hold them, but I decided to see for myself anyway. Turns out I must have different springs to everyone else or they are doing something wrong because every set of Associated springs I had clipped on securely. So I decided to see if there was a way to use them.
First thing was to remove the kit spring collars from the rear pod. They are of no use from now on so either chuck them in the bin or the spares box. Next I had to remove the grub screws that hold the pivot pins for the top/battery deck and remove the arms and pins. With the pins removed the grub screw hole goes all the way through so a long grub screw is required. I had some 25mm ones in my spares. This allowed me to screw it all the way through and then screw the retainer onto the end. Just be careful you don't over tighten the plastic retainer. Clip the spring onto the retainer and the easy bit is done.
The next job is to shorten the 2 pins that the "battery arm" and thus the top deck mounts on. The Dremel came out for this job. Thinking back on it, its probably not necessary to cut them at all but it looks neater if you do.
With the long screws going all the way through where the original grub screw was, there is no way to hold this pin so the only solution is to glue it. There is plenty of plastic for everything to grip to, so some Loctite Superglue did the job. So far its held fine despite being battered around in the combined Mini/21.5 TC class I have to run in to get some F1 track time. Put everything back together making sure that nothing binds and its pretty much done.
The long grub screws now serve as tweak screws so I adjusted them as required. On the track everything is working together fine and no lost springs as of yet.
Its hard to say if this mod has helped the car other than for convenience because I've also changed to using longer links. As it stands the car is hooking up nicely with Shimizu F3 fronts and R1 rears on the grip challenged home track. Usually I've been using TRG Superion rears that offer more grip, so something is working right.