Print and care | Rim Reader

One bracket, one wedge

The bracket is a solid 15 mm slab with a tray for the phone. A fixed rail along one long side and an end stop at the FRONT end hold the phone in a corner. A window in the rail leaves room for the buttons on the phone’s right side, and a channel under its top end leaves room for the camera bump.

Four prongs, one at each corner, are the only parts that touch the wheel. Each has a rounded nose, so it makes the same contact on the rim’s lip every time.

The wedge drops into the gap on the phone’s left side. Pushing it toward FRONT clamps the phone against the rail and the end stop, and it stays put until you pull its tab.

The empty bracket from above at an angle, showing the tray, the rail with its window, the end stop with FRONT engraved, the camera channel and the four prongs, with an orange wedge beside it — The bracket and a long wedge. The window in the near rail is for the phone’s right-side buttons; the slot across the tray is the camera channel.

Sizes and weights

Bracket: 210 × 120 × 15 mm slab; 210 × 184 mm across the prongs; walls 17 mm above the floor of the tray
Prongs: Four, reaching 32 mm past the edge to clear the tire’s sidewall; 14 mm wide, 8 mm tall, rounded 7 mm nose
Phones: 67 to 91 mm wide in their case; up to 15 mm thick including case and camera bump; the tray is 172 mm long, and longer phones may overhang the open end
Wedges: Two sets of eight: long (140 mm) for phones with no buttons on the left side; short (40 mm) for phones with buttons there. Each wedge covers 3 mm of phone width.
Markings: FRONT with an arrow either side, engraved on the front end; the wedge’s width band engraved on its top
Material: PETG, about 225 to 345 g for the bracket and one wedge
Design: Version 1.7.0

See the parts pulled apart

The bracket, wedge and phone pulled apart, showing the tray, rail, end stop, camera channel and the four prongs — Bracket, wedge and phone, pulled apart.

See all sixteen wedges

All sixteen wedges in two rows: eight long wedges and eight short ones, each a size thinner than the last — The long set (behind) and the short set (in front), eight sizes each. You print only the one that fits your phone; the wedge finder tells you which.

Print settings

Material: PETG for every part
Nozzle and layers: 0.4 mm nozzle, 0.2 mm layers (it also prints on a 0.6 mm nozzle with 0.3 mm layers)
Bracket: Back face down, as the file comes. 4 perimeters, 8 top and 8 bottom layers, 30 to 40 % gyroid infill
Wedge: Standing as the file comes, 100 % infill: it carries the clamping load
Supports: None, anywhere
Bed: 220 × 220 mm or larger; the bracket and a wedge fit on one bed
Brim: None on a textured PEI sheet; use one on a smooth or cold bed

Optional: 0.12 mm layers for the first 10 mm of the bracket give smoother prong noses. A large flat PETG slab can lift at the corners on an open printer; a brim and an enclosure help.

The print files will be published when the app launches. What’s coming

Print it in PETG

PLA and a hot car don’t mixPLA softens at about 55 °C. A PLA bracket left in a hot car can take a set with no sign you can see, and every reading after that is off. Use PLA only for a bracket that never leaves the house.

Care

Two colours. Print the wedge in a different colour from the bracket, so a missing wedge is obvious.
Before every use, check for cracks, looseness or wear, and don’t use a bracket that has any.
Keep the prong noses clean and undamaged. They are the measuring surface. Keep them off the tire’s rubber.
Temperature. The bracket is meant for 5 to 50 °C. Push the wedge again once it has reached the outdoor temperature.
After a drop, a reprint or a new phone, run Bracket Calibration again.
Before the car moves, take the phone and the bracket off the wheel.

The camera version

A second version of the bracket has the camera channel cut right through, so the phone can scan the VIN or the tire label without coming out of the bracket. It is about 30 g lighter. Use the standard bracket for measuring.