Tamiya BT-01 track performance

[Eric Bloodsmith 25]

  Over the holidays I built up my BT-01 Supra in the Front Motor Rear Wheel Drive config. I neglected to take any WIP photos, but it was a pretty simple build thanks to Tamiya's great instructions. The body stickers have two sets for the early and late type of the supra JZA80, with very different looking headlights. I went with PS-22, racing green, backed in PS-12 silver. I am very satisfied with the paint job but you gotta take your time with the front bumper area and go with thin coats. It's a bit difficult to get in all those nooks and crannies. I use some vinyl around the body post holes to prevent scratches.

  One of the major upgrades I did for this chassis is swapping to all hex machine screw hardware. It took >60 m3*10mm screws and a handful of m3*8mm and m3*12mm screws. I used a cutting tap from my LHS. Tapping all the screw holes into the hard but brittle PC-ABS plastic meant I could reuse those threads again and again without issue. I want this chassis to drive for many many years.

    I swapped out the stock 70T spur for the TT-02 68T high speed spur. If you want to use any other spur with the BT-01 I highly recommend it, just know that you have to swap the regular button head screws in the motor mount, holding on a side bracket, for countersunk screws so the spur mount clears them. I used an xacto knife at an angle to carve out the counter sinking. Just keep checking with the screw to see if it is flush before continuing to carve.

  I used the MB-01 bearing set from Tamiya. They're all shielded bearings, but for an on-road car, they should be fine. I also equipped the TT-02 oil filled shock set. The friction shocks it came with are all right, but since the step screws needed for them are self tappers, they had to be swapped out. Oil shocks definitely helped in the uneven parking lot. One thing to note when using the TT-02 set is that it comes with 6 ball studs that work fine, and two balls with threaded centers and long grub screws to mount them in, which are a slightly shorter length. You'll need 1mm of shims or additional ball studs on each of those to line the shocks up perfectly.

Other than that, I mounted my Dynamite 20T 540 motor I used in my DT-03 last summer, and some budget ebay tires by Acekeeps since I didn't want to wear the stock ones out. On my asphalt driveway, these tires gripped up very well. I drove on a circuit like this:

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Just 5 waterbottles used as pylons for this track. Even with these cheapo tires, since they come with foams and are VERY soft, they grip super well. I haven't setup any laptiming for this yet, but I figured out laptrax and got that to work today, so expect to see this rig in Postal Racing this month.

    The BT-01 feels very well balanced. It requires very little braking to transfer enough weight onto the front tires to make sharp turns. I was able to keep it pinned at 80% through the straight only letting off to 60% for the corners. It felt really nice carving up the track. The ~60/40 weight split front to rear is very noticeable. The front end has SOOOOOO much authority once you load it up that I swear I could hear the rear end slip out a little when I was cornering really quickly.

    Now, for why I put this post into the racing section! I took both this BT-01 and my 3racing M4 M-TC with a Lotus Europa shell down to my local carpet track for a race day. Naturally, the high grip black carpet made for a pleasant ride. However, neither chassis fit into any class so little racing got done with them. I did fit a transponder though and had a lot of fun getting my lap times down. The BT-01 started the day feeling very floaty. It turns out the soft tires I went with were shifting side to side under the rims. I purchased a set of USGT belted tires and went back to the track. The much firmer tires made the car feel more planted on the track. The raised battery above the driveline did make it feel a bit top heavy, and it was prone to traction rolling on this high grip surface. I managed to get my laptimes down to a flat 15.0 seconds, only 0.8 secs off the 25.5T TC class.

Now for the 3Racing M4, a belt-driven 4wd mini sized TC. It can be 210mm or 225mm, short and medium M-chassis sized. I had it setup in 225mm with a torque tuned motor for my Lotus Europa Special shell which garnered many glances from the crowd of competitive racers. It has a spool up front, an oil diff in the rear, and a boatload of toe in up front with the stock setup. That toe in helps with high speed cornering, letting me get down to a 15.4 second lap. I ended up staying on throttle for most of the course, only letting off very slightly. It has the motor mounted to the rear and handles kinda like an MR chassis. Settling down the rear end at low speed was a challenge, but the track was in more of a high speed layout anyway.

Racing is fun, but I don't really like strict classes, especially stock motors. My local offroad track opens back up in April, so expect to see some race reports as I challenge 2wd mod with my DT-03 once again!