9" Diameter Wheels

We had originally designed our drive chassis to be fit with the Andy pneumatic wheels. We’re now looking at these wheels on a drive train compared to the defenses and thinking that they’re rather small. We have 6 8" diameter wheels from earlier this wheel, but would prefer to find even bigger wheels. Our design constraints dictate that the biggest we can go as of now if 9.75" diameter with a 2 inch width. Does anyone know where to buy wheels between 8.5-9.75" in diameter and that have a 2" width? We need 12 if that’s possible.

First off, have you tested the wheels? I assure you that if you designed to use 8" wheels, you should try them out. Our team is able to get over the defenses with 6" wheels. Secondly, if you swap wheels, you’ll need to modify your Gearbox so you can keep a reasonable speed, so keep that in mind.

Our wheels our enclosed within the chassis so we’re pretty sure were going to hit the rock wall and stop with the Andymark wheels. The gearbox can be fixed rather painlessly if need be.

You could look into a system like Wildstang in 2012 to raise the front end and get the wheels on the defenses if space and weight allow.

Unfortunately our sheet metal chassis is set in stone at this point. We also only have three inches of clearance currently between our bumpers and the floor.

Bumper or chassis? Read the bumper rules carefully, they must be within the bumper zone.

Sorry I meant Chassis, the bumpers will be 4 inches above the floor. Thought’s on doing something like 1114’s 2012 chassis design?

Our team has run into a similar issue, as the 8" wheels are surprisingly small. Once our chassis was done, we realized we couldn’t get over the rock wall and moat, but by simply using flexible plastic “skid plates” on the front to reduce the angle of attack we were able to do everything as planned.

Soooo like 1/8th lexan? And you can get over the rock wall with this?

Mountain Board Systems has a 9" x 2" tire (9" is really about 8.5")
Unfortunately they have been wiped clean of their inventory it appears - and won’t have them until end of February per the website.

But we used them in 2012 and they provide nice customer service, suggest giving a call to them.

Yeah Lexan would work fine, we just used some random ABS I think and yes we could get over the rock wall with only 3" of clearance.

Assuming you guys are comfortable making/modifying hubs, Harbor Freight has an option:

They are listed at 8", but are closer to 8.5" IIRC. There’s a few Harbor Freight locations around Philadelphia (Sharon Hill, Norristown, Northeast Philly) if you want to inspect them in person.

+1 for the the Harbor Freight tires. They have similar grip to colsons and are between 8.5 and 8.75 inches in diameter depending on inflation. They also have the + of only being 8 dollars each. For hubs we grinded out the center bearing housings and laser cut some plates with a hex in the middle that bolted on with the pre existing hole patern. They are quite heavy however, so they may or may not be an option.

Harbor freight also sells the same size wheel as a castor with a black wheel. It is not nearly as grippy as the one linked above.

These are great if their actually 8.5". The color is an added plus. Would we be able to use the vexpro hex hub kit? We already own and were planning on using these. What is the width of those wheels?

Don’t know the width off-hand.

The Vex hubs won’t fit the wheel natively, but it could be adapted if you’re careful to ensure it’s centered.

The wheels are actually a lot darker than the photo on the harbor freight website. They are around 2.5 inches wide at the thickest point depending on load and inflation. Actual contact area is around 2-2.25 inches with the ground.Versa hubs could work but it would be difficult to mount them as the hubs are made of steel and the only mounting points are the bolts holding the wheel together. If I had to make hubs again I would ether 3d print them, cast them in a 3d printed mold or depending on if your team has a mill just drill the versa hole pattern and bolt a hub to it. Doing it by hand is possible but idd imagine immensely frustrating to get the hole pattern centered.

We have a CNC Mill and have already made Versa mounting hubs for our 7.5" wheels - made by McMasterr that have the exact same type of steel hub. I have no worries about making hubs. At this point my chief concern is the correct diameter and width. 2.5 inches at it’s thickest point is pushing it but I think we can fit it. If anyone has any extra wheels with a 2.5" width and 8.5-9.75" diameter we’d be happy to buy them from you. I’m hoping for pneumatic wheels but at this point we’re happy with anything we can get.


Look at the wheel assemblies. When you figure you get the wheel, tire, tube, bearings, and sprocket it isn’t a bad price per wheel. I also found similar wheels from light aircraft suppliers.

I went to their website but their sizing is confusing me. I’m assuming the size 3.00-8 is a 8 inch diameter wheel with a three inch wheel? Maybe you know better then me, but all their products seem to be this size.