Max tire size?

I have a question I’m having trouble getting an answer to. I want to know if I can put a wider tire on my uni. The reason I’m having trouble is that I have no understanding about rim size vs. tire size. Does my rim determin how wide/narrow I can go? Obviously the frame is going to dictate how wide I can go as well but I have no idea what the rules are on clearances on the frame are.
Right now i have an 05’ 20" Torker DX with a 2.125 tire on it. The frame inside measurement is (about) 3-3/16". Can anyone help out a newb, please?

Ok, via the search I found out about bead size but I’m still unsure about max width vs. frame size. Is there a good rule of thumb to follow? If I have 3-1/4" I feel like a 3" tire might be too big.

You mentioned that it is a 20" DX. That simplifies things in that you don’t have a lot of choice. For the rim you have you need a tire with a bead diameter of 381mm which means you are limited to tires that are 2.5" wide (or a discontinued 2.6" tire I believe Monty made for a short time)

Personally I like to have at least 5mm (a little bit less than 1/4") clearance on either side of my tire. Not all tires actually measure up to their stated size, for example with 3-1/4" clearance you would probably be fine with a 3" Durro but would be rubbing with a 3" Gazz.

Ok, cool. Thanks. Now, short of using a string to figure out my rim diameter, how do I go about figuring that out? There no markings on the rim that I can see. I believe you when you tell me it’s 381mm but how do I figure this out on my own in the future?

Side question if someone will indulge me, is there any practical difference between a 2.125 and a 2.5 tire? As a trim carpenter, a 1/4" is a world of difference.

They make 20" Duros?

No, I was just talking in a general sense incase someone had a 24 or 26" frame and was looking at this thread and wondering about max tire size for their frame.

The '05 DX is a true 20", not 19 so a regular trials tire won’t fit. They make 2.5"+ cruiser tires but those often have flimsy sidewalls, smooth tread and may be off on rim diameter (I tried one and fully inflated could almost pull it off the rim w/ just my hands)

Frame width is no problem ur concern is clearance to the crown. How much u have? The widest tire made I’d consider trying is a 20x2.4 Onza Sticky Finger avail at UDC UK. I don’t know of anywhere u can get it in the US.

Odyssey makes a 20x2.35. I forget the exact model. It’s avail in the US.

Also please note that actual tire size often has little to do with what’s printed on the side. For height (distance from rim lip to crown), that dimension can change depending on rim width. The wider the rim, the lower the height (I know there’s a proper word for “height” but can’t remember at the moment).

Width is an even bigger factor of rim width, and may not be exact either. To make matters more difficult, even if you can measure a tire in the store, that still doesn’t help because it isn’t mounted on a rim, or might be mounted on a rim that’s a different size, or not inflated, etc.

So best bet is to find someone who has a tire they have already fit into your type of unicycle. Or be prepared to buy multiple tires…