Mini 4WD Setting Board: Measure Before You Tune
A Mini 4WD that “felt better” after you tweaked the rollers is not a setup. A setup is a set of numbers you can put back after a crash. A setting board and a few gauges are how racers record roller height, brake height, width and ground clearance so the next heat is the same car. Tamiya also says, in both the Official Regulations and Stock Class, that HG aluminium setting boards, setting gauges and pinion pullers must not be attached to the car. This page is the bench tool, the inspection box, and the log — not a millimetre recipe for every chassis.
What you are actually measuring
Four numbers decide most “it flew off” arguments. Roller height: how far the wall-contact wheel sits above the track, front versus rear. Brake height: how soon the sponge meets an up-slope. Overall width: whether the car still fits under 105 mm after you added stays. Ground clearance: the 1 mm official minimum, and whether a brake stay or a screw head is the thing that actually scrapes. Mass and length/height live in the same notebook: 90 g minimum including motor and batteries, under 165 mm long, under 70 mm tall. Write the chassis, the motor, the gear ratio, and the tyre diameter next to those numbers or the log is fiction. Inspection box: tech inspection. How rollers and brakes use those numbers: roller setup and brake balance.
The board is a bench, not a Grade-Up part on the car
Tamiya’s HG Aluminum Setting Board (the black version is catalogue item 95507) is a flat reference with the car’s outline and typical measurement stations. You park the chassis on it, read heights against a gauge, and put the board back in the pit box. Official Regulations and Stock Class (item 6 of the Stock modification list, added in the May 2026 red text) forbid attaching that board, a setting gauge, or a pinion puller to the race car; the Basic-MAX GP v5 equivalent is organiser-sheet wording, so check your event’s printed sheet rather than assuming it repeats Tamiya’s. If an inspector sees an HG board screwed to a stay, the original part shape is no longer identifiable as a setting tool used as a setting tool. Category: tools and maintenance. BMAX wording: BMAX rules 2026.
A repeatable pit log beats a memory of “a bit lower”
Use the same units every time (millimetres). Measure both sides. If the left front roller is 1 mm higher than the right, the car has a lean you will otherwise blame on the motor. After a jump landing, re-measure before you change anything else — sponge compresses, stays bend, screws back out. Malaysia’s humidity makes sponge brake height a living number: a setting that was legal and fast at 10 a.m. can drag by the final. Carry spare sponge and reset to the log, do not chase a new height every heat. The scientific version of this habit is one-variable testing. What to pack: pit tools.
False readings
A warped board, a board used on an uneven table, or a car measured with the body off (or on) inconsistently will give you theatre. Measure in the race condition: body on, batteries in, the same wheels you will run. Do not measure roller height with the car pressed down; Mini 4WD has no suspension travel in the RC sense, but sponge tyres and slightly loose stays will still squash if you lean on them. Worn rollers that have gone undersize will read as “low” when the real problem is diameter — Stock Class lets an inspector reject markedly small rollers, and most organiser BMAX sheets take the same view. A pinion puller is for removing pinions at the bench. It is not a stay.
The inspection box, restated as a checklist
- Width under 105 mm, including rollers and stays.
- Height under 70 mm, including body and any high-mount rollers.
- Length under 165 mm.
- Ground clearance at least 1 mm at the lowest screw, stay or sponge.
- 90 g or more, ready to run, motor and batteries in.
- Tyres 22–35 mm diameter, 8–26 mm wide, still attached.
- No setting board, gauge or pinion puller on the car.
Those numbers are from the Official Regulations as of this research. Recheck before the event. Local BMAX sheets may add wear millimetres (v5 is commonly quoted as 1 mm tyre/roller diameter change and 3 mm mass-damper hole span — per your organiser’s sheet, as no public v5 document confirms it).
Frequently asked questions
Do I need an official Tamiya board?
You need a flat, repeatable reference. The HG board is the part Tamiya sells for that job. A homemade jig can measure; it still cannot be mounted on the car, and an inspector does not owe your jig a calibration.
What millimetres should my rollers be?
There is no universal answer. There is a number that, on your chassis and your course, kept the car in the lane. Write that number down. Copying someone else’s millimetres without their chassis, tyres and track is how cars climb walls.
Can I leave a gauge in the body “just for the final”?
No. If it is on the car, it is a part. Setting gauges are named as prohibited on-car parts in the Official Regulations and Stock Class; the BMAX GP v5 position depends on your organiser’s sheet.