27.5x4.5 is actually in the vicinity of 31" diameter. It is slightly larger than a 26x4.8 Surly Bud as the Bud just clears a Bluto fork, but the 27.5 Barbegazi rubs.
The whole 27.5 fat is pretty much a marketing gimmick as it is only slightly larger (.75" or so diameter/ .375" radius) than a 26" fat tire. It is nowhere near as big as the 1.5" size difference suggests. In fact the 27.5x4.0 Hodag is so undersized it is smaller in diameter than some 26x4.0 tires.
Personally I’d go with 26" fat as it will allow you to run a lot more different tires and you aren’t stuck with a few options (three Bontrager and one Maxxis) that may or may not work well for uni. Unicycle handling is way too tire dependent especially with fat tires to limit yourself to a few choices.
Ooops, I forgot to subtract the standard 2.0-inch tyre size.
So a 27.5 wheel (outside diameter with a 2.0 tyre) will have a rim ISO size of 548 for the rim and tyre bead diameter, according to the UDC (UK) website:
27.5 inch = 548mm, which is 21.9 inch, plus 4.5 tyre (x2) = 31 inch overall diameter.
26 inch = 559mm, which is slightly bigger at 22.3 inch plus 5.05 tyre (x2) = 32.4 inch diameter.
Now I am really confused.
On the plus side - the 27.5 x 4.5 should fit, with it being a smaller rim diameter (if the UDC-UK figures are correct), and a smaller outside diameter overall.
"As if bicycle tire sizing wasn’t already confusing enough, wrong-headed marketeers have recently tried to popularize a fourth designation for the 584 mm tire size!
They are trying to get people to call it “27 five,” as if it were halfway between the MTB “26-inch” and “29-inch” sizes. (Get it? “five” actually is supposed to mean “point five.”) Actually, this size is closer to the “26-inch” (ISO 559 mm) size than the “29er” (ISO 622mm) size, and even smaller than the “27-inch” (630mm ISO) size found on older road bicycles. I strongly urge readers to resist the foolish jargon, and to use either the traditional “650B” designation, or, better yet, the internationally-standardized 584 mm designation. "
The UDC-UK website has the numbers mixed up at 548mm - hence the confusion
The hatchet frame has 40mm clearance between the Kenda Juggernaught 26x 4.0 tyre (98-559), to the top of the frame.
35mm of that extra height should be usable.
Across the top of the tyre, there is 135mm width (=5.4-inches so plenty of frame width), increasing to to the widest point a little lower down, appx 6-inches wide at 150mm.
So from what I’ve gathered, 27.5x4.5 Barbegazi fitment on the hatchet frame shouldn’t be an issue.
(Thanks for crunching the numbers reeny/saskatchewanian/paochow)
I really would prefer the widest rim on the market.
27.5" x85mm (wild dragon ii) is listed on nextie but under specifications, it’s listed as a 26
27.5" x 65mm (black eagle ii) is listed as 27.5/650b compatible.
Does anyone know of any other options (80mm-100 mm 27.5 rims are probably a year or two out of the mainstream market from what I’ve gathered)
My other concern is the strength/durability of a 32h carbon rim in a muni application. Nextie has an option for the larger atomlab torque nipples. Is that something I should consider? The last thing I need is having my new 1000$+ uni grenading itself after its first UPD.
As for the argument that there are more options if I go the standard 26" fatty route. Yes, there are, but if I’m going custom uni route, why not be the one of the first guys out there with a 27.5 fatty? After all, none of us unicycle to blend in.
That being said, I’m just trying to do my homework first.
You can’t innovate if you are uninformed.
crazyunicyclerNJ (or others):
Curious how you would compare the 26x5 to the 29x3. I’m trying to use this tire for paddling through deep sand. The 29x3 does well if I can build a bit of momentum, but if the sand is really deep or churned up it finally ends up digging in and stopping me.
Does the 26.5 float way better than the 29x3? Any other differences? Any thoughts on a 26x4?
I actually prefer the 29 where I ride as I like the larger size. I ride a lot of technical trails, the 26x5 is good on it and cushions a lot more. i had more difficulty with larger obstacles likely because I had a lower tire pressure and the tire deformed more to go over it than the 29x3.
What I did notice also was my 29x2.25 vs my 29x3 (completely different unis) is that the 29x3 was more forgiving when you didnt get your line right in the technical part, the 26x5 even moreso sometimes, but was easier to get stuck between 2 rocks
Regarding Unisomniac’s idea of a 27.5++ Hatchet, there is the SUNringle Mulefut 32H-hole 80 mm (75 inner width). It’s the same brand they use on the 27.5 Hatchet only 30mm wider. Price isn’t bad, either.
I’m thinking about buying a Hatchet and having a build with this rim (US UDC has 125mm 32 hole disc hubs in stock). Then I could use the 3.8 Maxxis Minion FBR or the 4.5 Barbegazi and I’m sure there will be many more options to come. I was tempted to get the 26, but just like the 27.5 wheel size so much more (I have 26 and 27.5 Oracles).
I’m not sure why this hasn’t been done yet (even by UDC) but maybe I’m missing something.
A big wide single walled rim doesn’t exactly inspire confidence during any kind of impact likely to occur during the type of riding that this sort of setup might be used for.
The Hatchet is a new product. It makes better business sense to market it with a smaller (read stronger and cheaper) rim and tire combination with the ability to upgrade later. Cramming the biggest tire that can fit, and potentially rub in adverse circumstances, on a rim that really isn’t designed to support the entire weight of a rider over rocks and drops would likely tarnish the reputation of the hatchet as a product, as well as increase the price.
If we had more demand and, as a result, more market support for the 27.5" tire size, you would see a double walled 27.5x100mm 36H unicycle specific rim and the entire fat tire catalog produced in both 26" and 27.5"
Maybe some day, but right now, the less than 100 people globally that might be interested in, and have the money to purchase a 27.5 FatUni specific setup, are far to niche to warrant a new product.
For what its worth, I had trouble with the MuleFut 50 bending upon a minor rock hit. I imagine the 80 may have the same strength (or lack) as the 50. This could’ve been a fluke, but thought Id mention. I’ve ridden the Duroc, Marge Lite, and the Rabbit Hole rims a lot and never had bending issues with either of those ( of course they don’t come in 27.5).
Thanks for the info. I really don’t know that much about them. I do know it’s the same rim Trek uses on the 27.5 Farley 5 and 7’s MB’s. Several months ago, I did mention to UDC US that they should make a fat 27.5 rim like the 26 80mm and the response was they just might, whatever that means. I may wait another month or 2, but not much longer. I’m surly not getting any younger and the 27.5++ keeps calling me.
Bortananger also makes the 27.5 x 3.8 Hodag, although not sure how good it is. A 3.5-3.8 tire on a 27.5 would be ideal for most muni all year round here in New England—fast, good cushion on trails, and good for snow. Thanks again for the rim info—it does make me pause.
Such a big investment, haven’t pulled the trigger yet. But UDC US said they are hoping to have a batch of 27.5 Hatchet’s with 80mm rims and 4 inch tires out in April or June.
That would be great! I just got the Hatchet with a 26 inch 4.8 tire. I have been thinking of getting a second tire for the summer. I was planning on building a 27.5 by 3 (or 4). I wonder if they will sell the individual already built wheels? Or I guess I could buy the parts for a build.
I am confused; read somewhere that the Hatchet frame won’t take the 32 Nimbus nightrider tyre as it is 32x2.25 rather than the 32x2.125 given in the Hatchet spec.
Has anybody got experience with this?
According to my simple maths, the stock tyre
Maxxis Minion 26x4.8 is 102-559 in size, so 559+2112=783,
whereas the Nimbus night rider 32x2.25 is 57-686, so 686+257=800,
when the ⅛ inch smaller raiser tyre Kent 32x2.125 would be around 686+2*54=794
So, the Nimbus tyre is 6mm too big, of which 3mm would be lost frame clearance.
Given that this would be for road use, will a Nimbus tyre really not fit a Nimbus frame so that a cheap Walmart Kent tyre needs to be imported from North America to actually run a 32” wheel in a Hatchet frame?
Any advice would be much appreciated before I make a costly purchasing mistake.
Well, it’s a funny olde world… spurred on by the other current Hatchet/rim thread which we both posted on, I thought I’d better pull my finger out and stop the procrastination.
So I ordered a Hatchet frame yesterday and it came today (usual great service by UDC UK…). It also so happens I have a 32" Oracle with the stock Nimbus Nightrider tyre.
As they say, the proof of the pudding is in the eating, so I’ll take the wheel off my 32" Oracle and try it in my Hatchet frame and post a photo of the result. That should be pretty definitive.
So I thought I’d best go and try this this morning before other things took over. As you can see below the 32" wheel from my Oracle nowhere near fits the Hatchet frame. It looks like it is at least 15mm from the bearing seating in the housing.
Just for completeness, this is with the tyre pumped up to 65psi (max stated pressure), just to be sure it was fully inflated.
