The Cartrix GP cars are nice looking. But There is a few things that have to be done to get good performance .
The guide should be Ok for most racing if the braid is changed. I have found Slot Car Corner braid to be good for this application.
The most common problem is the pinion splits and becomes too loose to drive. I replace the pinion with a Plafit 9 tooth plastic and the problem is solved.
However before replacing the pinion I would suggest fitting a BWA 14.6k FC130 motor.These give a bit more power in most cases but not excessive The motor is a bout $7 and the pinion comes in a pack of 4 for $4.
Once the motor has been fitted & the gear mesh is correct place a drop od supper glue on the top of each side of each of the plastic motor bracket this is flowed to the end bell on one end and the can on the other. The four dots shouls be enoufg to hold the motor. They can be cut to remove the motor. Alternatively the motor can be wired in through 2 small holes drilled in the chassis alongside the motor can.
Next replace the rear tyres with DArt Canada or MJK Vintage Ninco. The original tyres are too grippy on most tracks & lead to tipping in the corners.
Also the tipping is due to the front axle being free to move up & down.I found an easy fix to this . I used the rear axle bushes to fit to the front. Plastic bushes salvaged from a Scalex car would do the job. I used the MJK plastic bushes.
First remove the body top and slip off one front wheel wheel. Slide out the front axle. Open up the hole in the plastic bushes to allow the axle to run freely - can be a bit sloppy. Get 2 of 3/32" axle spacers about 3 mm long. Slide a space to behind the remaining wheel . Slide on the two enlarged axle bushes then the final spacer and the wheel first removed . If the tyres are fitted to the rims & the rima are tight on the axle the front tyres can now be trued on the tyre lathe - using the new bushes assembled on the front axle.
The chassis with all tyres & wheels fitted can then be placed on a tech board. This will get the front axle height correct while the bushes are super glued to the chassis. Careful not let the super glue get inside the bushes & glue the axle. The glue is just to hold the bushes in place so it is not critical as the body top recess will hold the bush in place as well. However make sure the bush is attached to the chassis .
Make sure the axle is very free to turn and spins freely.
Use 2 of the Slot.it 2.2 mm brass body retaining screws to replace the body shell. Adjust the screws so the body is free to rock on the chassis . This may leave a slight gap along the join to the chassis . It is worth it though. The car will be a lot more smoother and better handling. It does improve the situation of de-sloting on FPR going up the hill on Blue lane.
Gluing the tyres to the rim is not necessary with the MJK tyres. The DArt are softer but you may be able to get away without gluing. Sand tyres to true and round the corners inside and out is important.
Lube the gears and the trunnion where the motor shaft runs to keep the mesh. Use the correct grease for the plastic gears. Lube the axle bushes front & rear. Also the motor bush on the can end - not the end bell bush as it may get on the brushes,
You should be right to do some quick laps now.
I did the same procedure to the Kurtis Offy . It does have some suspension links that get in the way.They either have to be either cut or removed to get the body to sit closer to the chassis . I left it a bit loose with the cap & will work on that later. The Offy runs well though and is clocking 6.7 secs on FPR green . The BRM P35 does 6.6 sec. Both have the BWA 14.6k FC 130 motor
The Lotus 16 still has the Cartrix motor and does 6.8 secs.
Those times are very close if not the same as the Before 70's GP Cars fitted with the BWA 14.6 FF slimline. So we may be able to mix them in races. if we wish.
The after 70's GP's with he same ff motor get down to 6.2 secs so they will have to run separate at this stage.a