I just got an HPI RS4 MT for Christmas/birthday, and finished the
chassis assembly about .5 an hour ago... after about 15 hours total of
assembly here are my first impressions...
Over all the chassis was VERY easy to put together. All parts fit
perfectly... no filing or drilling was needed. Hooray for HPI's quality
control department... no missing parts at all. As we all know, new kits
can suffer from missing / defective parts, and parts that don't fit
correctly. (Usually a kit manufacturer will have to make a running
change to the kit to remedy the situation). This was not the case
with the MT... ALL RIGHT!! In fact, there are actually a few extra
screws and E-clips included in case you loose something.
I guess the most difficult part was inserting the roll pins into the
rear drive axles. When new, these can be very tight, but with
persistence (and vise-grip pliers) I got them to fit in nice and snug.
The gear diff's are identical to those found in the nitro RS4
sedan. They use a series of steel bevel gears to convert power to all
four corners. As with any other gear diff, it's important to pack the
gear case with as much grease as possible. This provides some damping
motion and prevents the diff from free wheeling during hard cornering,
as the chassis will want to pick up its inside rear tires.
Chassis parts appear to be molded out of two different plastic
compounds. A soft, flexible, poly-plastic is used for bumpers,
bulkheads, body mounts and other components that will be subjected to a
high degree of impact. This material appears to be very similar to the
plastic Tamiya uses to mold the TA02 sedan body mounts, and should be
very durable in a collision.
The other material is a hard lightweight composite... similar to the
stuff Associated uses to mold the B2 chassis tub. This is used for the
chassis tub, front end brace, A-arms, and other areas where durability
and rigidity are important.
The A-arms are especially impressive... talk about durable!! Ive never
seen so much webbing and cross-member bracing in a set of 1/10 A-arms.
The arms themselves are HUGE... 9.5 CM from pin to pin on the rear, and
8.5 cm for the fronts!! Fortunately the overall width is the same as my
RC10-T2... so MAYBE the 2WD truckers will let me run with them.
Also included is a pair of aluminum hinge pin braces for both the front
and rear suspension. These fasten to the hinge pins and prevent them
from doing the splits during a hard impact to the A-arms. This is a
pleasant surprise, and is unusual for a kit in this price range.
The kit includes 4 plastic bodied, oil filled shocks. Unfortunately HPI
only includes a set of #1 pistons for all 4 corners. I guess Im
accustomed to sets of pistons that can be used to tune things to track
conditions. In the stock configuration, the only way to change damping
is by changing shock fluid. HPI does offer a trick set of Teflon
pistons, with varying hole sizes if you want to pursue hop-ups. The
shocks themselves are very smooth, and should perform well at the
track. The shock shafts are the high point of the shock assemblies. I
was expecting some cheapie black colored shafts, similar to the ones
that came with my nitro RS4... but wait!!! HPI done good by including a
nice set of polished silver shafts.... ALL RIGHT!!
The steering system (like the HPI Sedans) is smmmoootthhh, and pretty
slop free. The bearing kit I purchased is sold by Top racing , and
includes BBs for the steering bell cranks. BBs in the bellcranks may
seem like a waste... but I strongly believe they increase the smoothness
of operation and increase the responsiveness of the system. The stock
set-up includes nylon bushings. The set includes a top notch servo
saver built into the bell cranks... this is the same unit thats
included in the Nitro RS4. Time will tell just how well it performs in
the heat of off road battle. One major weakness is the center drag
link. Like its sedan brothers, it consists of a cheapie Z Bend link.
RATS!!! this just wont do!! So I replaced the link with a Lundsford 1
turnbuckle and a pair of Rocket City swivel ball joints. Now this
thing rocks!! (and is way smooth)
The drive system is as smooth as the steering. As I mentioned earlier,
Ive added full ball bearings... this is a must for MY kit... even at
$60 for the BB kit (OUCH!!). Just for comparison, I first assembled the
kit with the bushings... Man, NO WAY!! Things just werent smooth
enough for my liking. (remember, Ill probably be racing against a field
of Losi XX4s... Only bearings will do!!... unless all the Losi dudes
care to replace their bearings with bushings... yeah right!!). With the
bearings in place the kit was very smooth... it practically free wheeled
when pushed across the floor, whereas the bushings would bind things up
instantly. As with any other RC car, bearings should be the first Hop
up for this kit.
The kit includes a killer slipper clutch. Its very similar to the
Associated slipper, except the pressure spring is not as stiff. This is
a good thing (IMHO). With my Associated kits the slipper spring is so
stiff that you can lock things up SOLID when compressed only about 1/2
the way. The HPI spring is much more gradual... much less sensitive.
One quarter turn on the HPI slipper nut is equivalent to about 1/8 a
turn on my Associated slippers. To protect the slipper and gears from
debris HPI includes a nice gear cover that is secured in place by
snap-in clips. The cover looks to be effective... Ill judge its
performance later at the track.
The kit includes some really nice HPI V-groove truck street tires and
chrome 5 star wheels. For racing Ill be using Pro-Line Stubby Ts at
all 4 corners. I don't know about this one... any 4WD racers out there
care to offer some "tire selection" advice??
As for electrics... I loaded up the best I could afford... A Tekin 420
G2 ESC passes the current to a Reedy 14 turn triple, DS machine wound
Mod. A cirrus SC-60 MGBB servo handles the steering, and a standard
Airtronics receiver tracks signals from my Airtronics XL2P radio. As
for packs, Ill be running various 6-cell sticks... anything from
trinity Zip packs to Max Cell matched 1700 SCRCs. I also have an
illegal trinity midnight, (I hot rodded it with ball bearings and H
cut lay down brushes ) I might drop this in the MT just for kicks.
CANT WAIT TO RACE THIS BEAST!!! Ill post a performance evaluation
soon after my first day of racing. If you have any further
construction/design questions... please post or E-Mail me.