How to calculate the widest tire my uni can use

Hello and happy unicycling to you all,
After finally finding out that my QU-AX QX series aluminum unicycle is actually a 26" rather than a 27.5" unicycle, and successfuly mounting my Magura HS11 hydraulic hub, I now wonder how wide of a unicycle tire I can put on this unicycle. On the used marked here, I have found a couple of 2.5" wide tires for $30.00 Canadian, and I also found a couple of 3" wide wheels (complete rims, tubes, 3" tires) for $50.00 Canadian. I think I’d like to go as wide as I can because:

  • I want to begin to learn how to ride mountain trails (or really rough hilly ones at least)
  • I want a wheel that has a good circumference for my commutes ( a wider wheel will offset the fact that now I am using a 26" wheel instead of the 27.5" wheel I had before I found out my unicycle was actually meant for a 26" rim)

So, with my google-fu, I cannot really find specifications for maximum tire size for this unicycle. I did find this tire calculator which helps a bit.

Oh, right now I have something like a 1.95" tire mounted on about a steel rim with an outside width of 39mm, I am guessing (big?) the rim wall thickness to be about 2mm per side, so the inside rim width is about 37mm. If that is correct, I should be able to put a “plus” size tire on this rim according to this chart by WTB. Even if not, if, I bought the 3" complete wheels, I could always build another wheel again based on the rims of those wheels for my unicycle.

Here is a picture of my current setup. I measure 86mm between the forks (inside), that is plenty of room for a 3" tire even if there is some wobble due to a slightly untrue wheel, although I managed to true it quite well. The dimension that I am probably most concerned about is between the top part of the tire and the frame. The distance between the bottom most part of the flat crown - inside is 86mm. Yes, right now I have a 1.95" wide tire mounted as you see in the picture:

Anyway, I am up for suggestions / help.

Dawson

You don’t need much clearance on the top, maybe a couple of mm because at some point you’ll suck mud up there. It’s the tire width that is trickier. I’ve found that it’s easier to get tire rub on the side knobs than you would expect. Ideally you’ll have >8mm on each side. If your frame is 86mm then 86-8-8=70mm which is roughly a 2.8" tire. I’m guessing a 3.0 (76mm) will end up rubbing because it will only have 5mm on a side to play with and the wheel moves that much under power climbing a hill, back pedaling, or even just free mounting. Every uni that now comes with the Duro Crux rubs under power because the amount of frame and wheel flex is too great, even for the KH that popularized that tire by specing it!

Thanks for this advice. I am starting to lean more and more towards the 2.5" tires, besides, I think from what I’ve seen 3" tires are getting harder to find, but 2.4", 2.5" not as much.

Dawson

Indeed, I’ve tried plus tires plenty and have settled on 2.6" as my favorite muni width. It’s wide enough to float but still carves turns well and easily

1 Like

Thanks. I neglected to put in my question, but the 2.5" are Kenda Nevegal 26 x 2.5 DH, the 3" tires were not a brand I recognized at all.

In theory you are right but in reality I dont think it will work well (assuming the tires actual width will be ~3" when mounted / inflated). You need more clearance if you dont want to have frequent tire rubbing when pushing it. I have a KH27.5 that has 103mm between the forks and with a ~3" tire I had occational rubbing and that is with a fairly stiff wheel build and a carbon rim. I also have a M4O Handle saddle and obviously that is very stiff and makes the softest part of the setup (the frame) flex when pushing it. So maybe it will work but I think I would go for a 2.6" or similar.
Also very wide tires can feel somehow sluggish in my opinion but it depends if you are trying to float over a lot of roots at low psi or you want a more responsive tire for use in easier terrain.

Thanks so much for responding, that is helpful. I am very much a beginner on rougher trails having spent most of my 400 km, or so, on this unicycle riding to the office and back, or on smooth surfaced paths.
Dawson

that 103 is actually 96mm. I don’t know why the width of the top of the fork matters to anyone but KH advertised it. In another post from years ago KH himself said the current frames are supposed to be 96mm between the blades. FYI. It’s still not wide enough IMHO if you want to use the Crux that the KH comes w/ complete. Marco told me that the L M4O are 105mm between the fork blades. That’s better if you aren’t brushing the fork w/ your ankles

1 Like

Thanks for the info. I had no idea that the actual width was lower than advertised.

I rode this fork for about 10 years. 26x 3.0 tires fit well. I tried the following tires: Vee Tire T-Fatty 26x 3.0, WTB Ranger 26x 3.0, Surly Dirt Wizard 26x 3.0, ONE4ALL MUni Tire 26x 3.0

The fork is high enough so that you can also clamp an SKS Grand D.A.D mudguard under it. At least that was possible with my fork

1 Like

Hello, Thanks so much. That is great news. I am currently looking at a Surly Dirt Wizard (26x2.75 120 TPI), and some local used tires (26x2.5 Kenda Nevegal), and a couple of complete wheels (3", but I the brand and tire model is not so clear to me).

I tried the 26x3 120tpi Dirt Wizard and immediately took it off and ordered the 60tpi version. It was just too floppy and flimsy, at least for my moderate muni riding. 60tpi was great.
When I went to order a spare they were down to, I think, 40tpi in the current model, which might be too much of a good thing.

Thanks @MrImpossible, I am really just beginning on the Muni side of my unicycling adventure. About all I can do right now is rough trails, gravel, grass, that kind of thing, not really any serious downhill, and I don’t have a lot of speed. (But I do have a brake at least ha ha). I am probably going to go with the used tires that are locally available for dirt cheap, the 26x2.5 Kenda Nevegal … I have no idea what the TPI rating for these is, but it is likely 60 or lower. I guess my original question was that I just like to know thngs like how wide of tire could I go if I wanted to? (not having seen any specs for my uni). Then there is the practical thing and the cost … and I am leaning heavily on just going a bit wider than I have mounted on my uni right now …from 2 to 2.5! (But I am also rueing having to go from 27.5 to 26 rims because I have now put on magura rim brakes and I have only discovered through this forum that what I thought was a 27.5" frame turns out to be a 26" frame … so I am losing a bit of diameter on my rubber … that in part was also why I was thinking about wider becasue it would give me more rubber circumference)

Dawson

Best advise dont over think. If you have access to used tires cheap buy a few different sizes and try them. Lots of over thinking goes on around here. The good news is your brake is lining up and will work, that was the hard part. I cant tell you how many 29er tires are hanging in my garage i purchased new at full price trying to find the right one. Found it!

Thanks @Bug72 Thanks for the encouragement.

As for overthinking, though, I can’t help it. That is the way I roll - engineering training, and just the way I think I guess. Also, I ask questions here because people answer them and have good answers, like yours. I suspect a lot of people on this forum are used to getting great answers and so they also ask, and it might come off as overthinking too.

Dawson

When the subject of tires comes up whether it be brand, model, width, pressure excetera you will get alot of conflicting advise and you can think and rethink till the cows come home,. It is just one of those topics that is very subjective, what one person likes another hates. I agree that throwing questions out here is the way to go, I seek advise here all the time. You are in a unique situation where you have access to several used tires at a low price. I say grab a few and try them out. I’m an artist and my ways of thinking are polar opposite from those of an engineer that’s probably why I have a garage full of 29er tires, instead of just one on my uni best of luck in your search.

Hi there, so I take it you have become an expert on tires based on the wide variety you have. I agree with you that each person will have a different take on what they like based on personal preference, riding style and riding conditions. Although my undergrad degree was in engineering I did a Masters in Linguistics and Exegesis and through that and many other experiences in life I have come to find the artist in me as well. I believe everyone has an innate creative nature / ability in them. So, as an example, even as a teen that was steeped in the scienes, when I made a radio or computer, I wanted to not just make it functional, but beautiful. (So it was an early form of sculpture for me). Hey, have a good day!

Dawson

My apologies I certainly didn’t mean to insult you and I’m certainly not an expert on tires but quite the opposite . Point bing I have bought a lot of tires not suited to me before I found the right one. I was trying to encourage you to take a chance and grab up those used tires and give them a try. Best wishes

Oh, hey. I didn’t take it like that at all. I actually was quite encouraged, I was just engaging conversation. BTW, I did just buy them today. (Two tires for 30.00 Canadian). I rode my mountain bike (unicycle with a training wheel about 11km to meet the seller, and then back. I could use my paniers to put the tires into thus saving a trip by car. (I try very hard to only use my legs to get around rather than a car)

Here are a couple of photos:


I’m very happy with it, and I can see that there is still room to “grow”. I have my eyes on a Surly Dirt Wizard (26x2.75) for when these tires give out. But, one reason I didn’t end up buying that bigger tire is that it costs more than twice as much as the two tires together, albeit one has about 75% trread, and the other about 50% tread.

So, I gave it a short spin after putting it together … but I need to go and eat pretty soon - it was a fasting day today.

Have a great day, and enjoy your riding!
Dawson

Probably my next upgrade is a handle saddle by mad4one. Or maybe I will build a saddle using just the base? I probably won’t do that for a while, I still am not very good at holding onto the bumper yet.

1 Like

You now have a good tire to practice with. If you really enjoy it you will buy the Dirt Wizard 26x 3.0 (60tpi). He’s just better. In German one would him
“Eierlegendewollmilchsau” call egg-laying wool milk pig