Mission Possible – Schumacher Mi4

Track test
For the track test we headed to a wide open test track to make use of the enormous power the 5.5T motor, in combination with the 7.4V LiPo pack, offered. We stayed with the kit set-up for the first couple of packs to get used to the car and the track. Due to the high track temperatures we used LRP’s VTEC 30R tyres that suited the track quite well. Due to the open layout of the track we first geared the motor 22/85 which gave tons of top speed but we felt it was better to go down one tooth on the pinion so we ended up 7.92 overall. The CS speedo offers a total of nine different power programs. Three of them are Stock motor programs for increased power. Programs 5 and 6 offer reverse for added ‘bash-ability’ for fun classes and program 1 to 4 are pure modified settings with soft to aggressive throttle curves. We started with program 2 which is a medium setting offering good acceleration and very good throttle control.

With a ride height of 5.5 mm at front and 6 mm at the rear the Mi4 had a good balance but lacked grip a bit. This was due to the dusty surface and we hoped it would cure during the day. With the spool/solid axle up front the Mi4 also lacked a bit while turning into sharp corners. We tried to cure this by mounting the shocks in the second inner hole. This made the suspension feel more progressive, giving the feel of slightly reduced grip on corner entry but in fact steering comes up mid-corner resulting in more overall steering and therefore exactly what we were after. Te get a bit steering into the corners back, we lowered the front inner ballstuds with the help of a 1 mm washer. At the end of the day we also laid the rear shocks more by mounting them one hole further in. This seemed to give more rear end grip corner exit but this wasn’t really reflected by the laptimes but we where very happy with the performance of the car so far.

Conclusion
Schumacher’s new Mi4 touring car is a very nice piece of kit with nice details like the new spur gear assembly and a clever steering set-up. Quality is top-notch but the tight fitting between the pulleys and the outer rings is a bit of a let down as it was a pain to get his part of the build done. In terms of specs the Mi4 offers a lot of value for money but we would have liked to see maybe a second pair of shock pistons or at least an optional set of pivot blocks to change the suspension geometry. But to be frank the kit setting is a very good starting point and you get some spare (thinner) Quik-Klips to alter the wheelbase in smaller steps as well as an assortment if different shims and washers for the toe and roll centre/link mount settings.

Specifications
Scale: 1/10
Chassis: 2.5 mm carbon fibre
Upperdeck: 2.0 mm carbon fibre
Drivetrain: fulltime 4WD
Differentials: spool/ball differential
Suspension: independent double wishbone
Shocks: alloy/oil filled/coil over spring

Dimensions
Length: 355 mm
Width: 187 mm
Wheelbase: 254 – 262 mm
Track – front: 162 mm
Track – rear: 162 mm
Weight: 1260 gr
*Stock set-up with wheels as tested

Equipment
Car: Schumacher Mi4 [racing-cars.com]
Motor: CS Electronic CS Magnetic 5.5T [cs-shop.de]
Speedo: CS Electronic Rocket Competition [cs-shop.de]
Battery: Speed Passion 4000mAh 25C LiPo [speedpassion.net]
Body: Mon-Tech TCR [mon-techracing.net]

Performance Tips
Differential/Spool – We had our problems to fit the outer rings to the diff and spool pulleys. The fit was extremely tight and the only way we could attached the rings was by cooling the pulleys down in the refrigerator and heating the rings up with a hairdryer. We then put the ring over the edge of our workbench (so 50% of the ring hung over the bench), pressed the pulley half the way into the opening and then while still pressing the pulley down we slid the whole assembly forward so the remaining part of the pulley was pressed into the ring.
Differential/Spool pt. 2 – The manual shows small shims that attach between the diff/spool and the bearings to eliminate axial play. We recommend to leave them off as a small amount of play ensures a free spinning and non binding drivetrain.

Motor – When attaching the motor make sure you have enough clearance between the motor can and the spur gear. This especially applies to the ‘ring’ for the bearing that most of the brushless motors offer. Also make sure that the motor shaft does not get in contact with the (LiPo) battery as this can occur if you slide the motor all the way through the motor clamp.
Screws – Use a medium thread lock on all screws that attach to metal parts to make sure they do not get loose.
Differential – Use a good quality lube on the diff and thrust bearings such as Associated Stealth lube (diff) and Associated Black Grease (thrust race).
Shocks – Associated Green Slime (or similar products) help to seal the lower cartridge and also make for super smooth and consistent shock action. If you want to know more about how to build the perfect shock watch the first part of our ‘Pro Tips with Gilles Groskamp’ video here.

Wires – Make sure the power wires coming from the speedo do not rub on the front belt. To avoid this we wrapped them with shrink wrap and also glued some thick foam pads underneath the top deck to press the wires down towards the battery pack.