January 15, 2026
Description
First, the name. G is for Gaub, or Greg, whichever you prefer. S is for Samson, as in Dennis Samson. His original design for a rotating sanding drum machine for whole axles (e.g. pressed on wheels) inspired this design to a great extent. It was with his input and feedback, along with others in the community, that this machine was finally realized as shown. I also owe thanks to Giacomo Verlini, aka JamieG from Sweden, for his design for the sanding sleeve drums that I have used for this machine. You can find his Tyre Truer MKIII for slot cars 1/32 and many other great models on his Thingiverse page. Also, Check out Geoff997's remix if you want to build a self contained machine with integrated power and speed control!
Key Features of the G&S Tire Grinder
Trues both tires at the same time
Standard 1/32 bushings snap into axle carrier, and V-shape allows smaller or larger bushings or bearings to stay in place
One motor turns all axes
Only four screws to remove/replace the entire sanding spindle for different grits
Single screw to adjust tram at any time, using a spring loaded bearing carrier.
Spring loaded axle carrier to allow "grind and release" truing methods with ease
Indicator knob for precise repetition of tire diameters as needed
Consistent tension of o-rings due to idler pulley design
O-rings can easily be moved side to side to accommodate various axle configurations
Distance between sanding drums accommodates most 1/24 and 1/32 wheels/axles
Sanding surface cannot contact axle pulley or o-ring
Join the Facebook group to share tips and tricks, build photos, make suggestions or ask questions. https://www.facebook.com/groups/gstiregrinder/
Setup and Use Video:
Click here for the Setup and Use Document (PDF).
Rubber Band (O-ring) Replacement Video:
This machine is provided free to download, print, and build your own. The license is Creative Commons, Attribution, Non-Commercial, Share-Alike. From a practical standpoint, that just means no one else is allowed to market or sell the files, plans, prints, or completed machines without my express permission. Credit to my project must be given any time the machine is shown or shared. Since I'm releasing it as open source, the "Share-Alike" part of the license means that if you design a machine that is derived from this design, you must also share it as open source with the appropriate credit to me. If you are contacted by someone to print the parts as a printing service, you have my permission to do so, but you cannot advertise that you are printing the parts for sale. I reserve the right to market and sell prints and/or machines until I am no longer able to do so. Pricing for prints/kits/machines can be found below.
All of the parts are designed to be printed on any FFF (filament) 3d printer with no need for supports. PLA can be used, and is preferred, for the majority of parts due to its rigidity. Parts that are subject to friction heat, such as the pulleys and sanding drums, should be printed in PETG, or similar high temperature material. The largest piece, the base plate, measures 168x120mm, and so should be able to be printed on most machines, even many of the "mini" printers. The Case Base Plate and Case Lid are slightly larger, but are not required for the function of the machine, only if you want to have a protective case for travel/storage purposes.
BOM (links are non-affiliate Amazon)
1x - RS-540 DC motor (35T-55T such as for RC trucks and crawlers)
Most parts can be printed in PLA, but there should be at least 4 perimeters (1.6mm thickness) and most parts should have a strong and dense infill, such as 30% Cubic.
The round/pulley parts should be printed in PETG or other high temp material, with a random seam position to reduce a “lump” from an aligned seam. The small pulley for the motor, and the split pulley for the slot car axle should also be printed 100% infill because they will split easily if not solid.
Written and Illustrated manual: G&S Tire Grinder Assembly Manual
Video guide:
Update 2026/01/14 - I adjusted the dimensions of the pulley storage on the base. Use the set screw to hold them in place if loose. Also added a pocket to the inside of the cover so that spares and parts can be put in there without them interfering with the grinder going into the cover. I use a ziplock sandwich bag for the stuff, then fold it up and put it into the pocket.
Update 2025/01/23 - Added a split pulley for 1/8" axles as well as bushings for 3/32" and 3mm axles, since double-flanged 3mm bushings pretty much don't exist, and those new to slot.it (and other) cars might not have spare 3/32" bushings for those axles.
Update 2024/12/29 - Added Spindle Clamp L XL, which adds 2mm to the adjustment toward the wheel, for when a machine build needs more than the original amount.
Update 2024/12/14 - Added simple thumb screw model for the EZ-Tram screw. It should be press-fit onto the head of the m3x10mm socket head cap screw used for the EZ-Tram adjustment screw. This should not interfere with the usable adjustment amount.
Update 2024/12/01 - Thickened the tabs for the pulley storage on the base plate. Added material around the hole for the bracing screw on the axle bracket, as over-tightening can stress the part and encourage failure. Also removed deprecated parts to avoid confusion.
Update 2024/10/24 - By request, I made the motor shaft hole in the motor pulley go all the way through. This will help with alignment when using motors with longer shafts than the one I originally used.
Update 2024/08/07 - I accidentally purchased aluminium spacers rather than steel, which have a slightly smaller OD and don't fit snugly into the Indicator Base part, so I made the hole smaller and uploaded an alternate part. If you got an aluminium spacer and don't want to use glue to hold that in, print the alternate part.
Update 2024/07/06 - New and improved tramming system. using two stiff pen springs on the left side, allowing adjustment up to 2mm above or below center. The two m3x6mm screws below the bearings are no longer necessary, and one more square nut and m3x10mm screw is needed. The BOM has been updated to reflect these changes. The idler pulley was also updated to add wider flanges at the end to try to prevent the bands slipping off the end.
Update 2024/06/30 - Added friction fit storage for one each of the split pulleys to the base plate. Look for Case_Base_Plate_v2 and print that instead of the original version.
Update 2024/03/17 - I was asked to work out the actual change in dimension according to the indicator knob. Here's the math:
The 1/4-20 bolt is 20 threads per inch, so thread pitch is 1/20" (0.05" or 1.27mm).
The ratio of center points (axle and knob pivot) to the axle bracket pivot point is 1.226, so the wheels move that much more than the knob does.
Multiply 1.27mm by 1.226 and we get 1.55mm per full knob rotation, or 0.13mm per whole number.
There are 72 notches, so each notch would be 0.0215mm.
Update 2023/11/15 - Added rotation direction arrow to Spindle Pulley and updated the 3mf that included it.
Update 2023/07/15 - Designed a hard shell case/cover for the machine. This required a slightly larger base, which is 100% compatible with the other parts, so can be replaced easily if you already have a machine with the original base.
Update 2023/06/26 - Redesigned the sanding spindle legs and clamps to facilitate tramming. For machines where the spindle was far from parallel to the axle bracket, the previous design did not have enough tolerance to tram them. The new design works better for that purpose, but does add two more M3x10mm screws and two more square nuts to the BOM. The old spindle legs and clamps were removed as deprecated.
Update 2023/06/08 - Redesigned split pulleys with square nuts for better holding power. Added one more square nut to the BOM.
Update 2023/05/26 - Changes to printed parts for better print quality and machine assembly. Added square nut to Motor Pulley for better security. Also “branding” of a couple parts.
G&S Tire Grinder Pricing (not including shipping) If you want prints or hardware from me.
Fully assembled and tested machine, ready to get to work is available from 132slotcar.us.
$100 - Complete kit of parts including all printed parts and hardware.
$50 - Printed parts only.
$60 - Hardware only.
$30 - Hard shell case
$25 - Sanding Spindle only (prints and hardware).
PSU not included. Shipping extra. International orders welcome.
To place an order, PM me here, or email me at [email protected]
License:
Creative Commons — Attribution — Noncommercial — Share Alike
MrFlippant
