New CAT on the block – Schumacher CAT SX

Track test
Because of the freezing temperatures in Northern Germany we took our CAT to an indoor off-road track. While preparing the car we already changed the soft kit suspension set-up to a stiffer one with the help of 35wt oil all round, red Schumacher springs (#U3396) on the rear and grey springs (#U3391) up front. After having a look at the multiple set-up sheets on the Schumacher homepage we also installed the medium rear swaybar as found in the #U3380 – Rear Roll Bars kit. Beside that everything else was left as found in the kits instructions and we even left the Mini-Spike 2 tyres on the buggy. Ground clearance was adjusted with the universals at level all round. The first run was very promising. With the Speed Passion 5.5T motor and a 17 tooth pinion gear, acceleration was very controllable while having decent speed on the medium length straight. The rear of the car felt excellent and very planted but the front definitely lacked a bit of “pack”. Damping was too soft and the springs felt too light too.

For the next run we changed the oil to 37.5wt oil and moved the shock to the middle hole wishbone. The front of the SX felt much better now. Very controllable with less chassis roll in tight corners. Since we did not had a front swaybar at hand we changed the grey Schumacher springs for blue Associated 2WD front springs which further added some stability while cornering. We also changed to Schumacher Mini-Pin tyres all round with the inner and outer row cut as these offer more traction on carpet. The buggy felt perfect at this stage with one exception: the two darn washboard sections. After looking at other 4WD buggies we came to the conclusion that we needed more droop as well as more ground clearance. So we detached all four shocks from the car, unscrewed the shock ends by two full turns and reattached them without changing their positions. We also raised the ride height so the bones become level with the surface. The buggy was now much more forgiving over the washboard section but we feel that the car needs some weight to excel. This is backed by the fact that we heard of some CAT SX drivers who added weight to their LiPo equipped cars on very rough tracks as it seems that the weight savings the LiPo technology offers not always result in faster lap times. Sometimes a car needs to be ‘heavy’ to ‘feel’ right. Speaking of feelings: the fact that the motor rotated in the same direction as the tyres really helps controlling the car while jumping.

Readers of the multiple internet forums might have noticed that at first the CAT SX suffered from breaking differential outdrives. Although we raced ours on a high grip surface with many jumps we did not manage to break one. It is likely that our review car was equipped with updated outdrives of the new batch which should solve the problem.

Conclusion
We are quite sure that the Schumacher CAT SX is one of the hottest tickets for the upcoming racing season. The buggy handles very well, is complex yet easy in terms of set-up and we look forward to race it outdoors. The LiPo retaining method may not be of everybody’s liking but the performance as well as the parts quality is top notch.

Specifications
Scale: 1/10
Chassis: 2.5mm carbon fibre
Upperdeck: 2.5mm carbon fibre
Drivetrain: fulltime 4WD
Differentials: ball differential
Suspension: independent double wishbone
Shocks: alloy/oil filled/coil over spring

Dimensions
Length: 367mm
Width: 247mm
Wheelbase: 282-284mm
Track – front: 213mm
Track – rear: 208mm
Weight: 1615gr
*Stock set-up with wheels as tested

Equipment
Car: Schumacher CAT SX [racing-cars.com]
Motor: Speed Passion Competition 2.0R 5.5T [speedpassion.net]
Speedo: Nosram Matrix ISTC [nosram.com]
Battery: Robitronic LiPo 5200 25C [robitronic.com]
Charger: Robitronic Overloader 2 [robitronic.com]
Servo: Futaba S9402 [futaba-rc.com]
Receiver: Futaba R603FS [futaba-rc.com]
Tyres: Schumacher Minispike 2 [racing-cars.com]
Body paint: Ginga Paint [gingapaint.com]

Performance Tips
> The steering bellcranks can develop a bit of slop around the ball bearing with time. A tip we got from Schumacher factory driver Ralf Missel is to ‘glue’ the bearings in with light threadlock.
> Sometimes the M3x4 screw that hold the outer slipper plate can come loose when not carefully tightened with thread lock. We also saw solutions that use a M3x10 grup screw and a 3mm wheel nut.
> The idea of fixing the LiPo battery pack with the help of two carbon plates is quite a tricky one as you have to buy several in case you would like to use more than one LiPo pack. In case you do not use flat case packs like the one from Core-RC or Robitronic you will have to make some sort of brace to fit and secure the pack properly. We found a very useful thread on oOple with helpful tips to cure the problem. To make sure the connectors or wires of the speedo and battery do not interfere with the middle drive belt we put some self adhesive foam under the plugs to give the Deans connector the needed clearance.

Review by Sebastian Suerstedt