New posts

650b+ on rear only

Dec. 5, 2016, 10:17 p.m.
Posts: 1172
Joined: Feb. 24, 2017

thanks Mike. those dimension differences may just have put the kibosh on the idea. i do look forward to demoing the Fuel EX plus with the 2.8 minions though. buddy says it's the bomb, sees no downsides.

Dec. 6, 2016, 6:56 a.m.
Posts: 985
Joined: Feb. 28, 2014

You can see the death of 3" tires starting to happen already, as people realize how shitty such a large tire can be. The industry is going 2.5-2.8 because those sizes actually hold some merit.

Dec. 6, 2016, 10:14 a.m.
Posts: 8256
Joined: Nov. 21, 2002

Alright. Here's a few rough measurements and specs on the wheels.
29er. Easton ARC 30 rims, Minion DHF 2.5, diameter to top of tread ~746 mm
27plus. Easton ARC 35 rims, Minion DHF 2.8, diameter to top of tread ~713 mm
275. Nobl TR38 rims (31 mm ID), Minion DHF 2.5, diameter to top of tread ~708 mm

Give or take a bit in the measurements, I didn't do it with digital calipers… But I think you get the idea. Pretty huge difference between 275/27plus and 29. When I first measured, it kinda surprised me that companies are offering bikes that are 29/27 plus compatible, when really I think they should be 275/27plus. But I bet things would change quite a bit if you change rim widths, go to bigger 3.0 tires, etc. Lots of variables!

I hope this helps.


This is great info, thanks

WTB Frequency i23 rim, 650b NEW - $40

Dec. 6, 2016, 4:49 p.m.
Posts: 0
Joined: Dec. 27, 2002

Noting the delta in radius is a much better way of looking at is as we're interested in Bb height change, fork clearance, frame clearance

29er. Easton ARC 30 rims, Minion DHF 2.5, RADIUS to top of tread ~373 mm (16mm more than 27+)
27plus. Easton ARC 35 rims, Minion DHF 2.8, RADIUS to top of tread ~357 mm (3mm more than 27.5)
275. Nobl TR38 rims (31 mm ID), Minion DHF 2.5, RADIUS to top of tread ~354 mm

But yeah, wow I kinda think this is wrong. 29 and 27.5+ have to be closer than this

Dec. 6, 2016, 6:54 p.m.
Posts: 4300
Joined: June 24, 2010

To add to the numbers conversation, it's key to note that the actual difference in diameter between a 27.5 and a 29" rim is 38mm (584 vs 622 respectively). The radius is half of that, 19mm. In order to get the same outer diameter from wheels with a 19mm difference in radius, the tire has to be that much (3/4") taller.

So of course the difference between a 29x2.5 and a 27.5x2.8 is going to be significant – even if those tires measured up exactly as the label says, the 27.5x2.8 is still about 11mm smaller in radius. Then you consider the 2.8" tire will be run at a lower pressure, and your bottom bracket comes down even more.

Now that said, 2.5 is a big tire, more than the average person rides, even on the Shore. Call it a 2.3 and the 11mm mentioned above becomes 6mm. I'd be willing to bet a lot of people have 6mm too much sag in the rear end of their Shore-style suspension setups.

Personally I like the feeling of a low bottom bracket, though some bikes along the way have taken that to the extreme. Whether or not your frame can handle it depends on your own preferences and the numbers in the bike itself.


Dec. 7, 2016, 12:22 a.m.
Posts: 2248
Joined: April 25, 2003

I've run really fast rear tires and grippy front tires in the past (mostly for racing) and although it works I'm gravating to tires that behave more similarly these days and it seems way more fun for fun type bikin'. Normal miner tire up front and big tire in the back sounds like too much of a miss-match to me, and kind of a backwards one at that. Slidey fast back end/grippy slower front end combo is good. grippy draggy rear/fast (relatively) washy front combo sounds terrible.

Similar style and size tires/smaller diameter rear? I bet you'd be on to something there (it's been done of course) but you better get the numbers right or you'll jack up your rides "finely tuned" geometry and have a shit heap in place of your previous sweet rig.

Dec. 7, 2016, 8:10 a.m.
Posts: 48
Joined: June 16, 2007

flattire - Like I said, I didn't measure with digital calipers, but I don't think I'm out by more than 3 mm. Even if the errors go the opposite directions, that's still only 6 mm. And I don't think I'm out by that much. But go measure for yourself, I think you'd be surprised.

morgman - I've got a 2.3 Aggressor mounted; I'll measure that tonight. But just from memory, I think the difference will be more than 6 mm radius to the 2.8 plus tire. Then add sag… I agree on the BB height until you get the extremes. I thought the Primer cornered a little better with the plus wheels vs the 29's. BB height, wheel size, and grip all change though, so take that with a grain of salt.

Dec. 7, 2016, 9:42 a.m.
Posts: 2248
Joined: April 25, 2003

Digital calipers would be a terrible tool for measuring bike tire diameter…:)

Dec. 7, 2016, 9:49 a.m.
Posts: 15019
Joined: April 5, 2007

By normal 29er tires I was talking about siz, 2.3-2.5" tires: DHRII, DHF, Magic Mary etc. Not 2.25 Ardents, Racig Ralph's. And not 29+ dumbo rubber.

Since the 27.5 rear / 29 front is gaining usage why not go further?
Increase your traction in the rear. Front wheel traction of 29". Lack the vagueness I found with 27.5+ front. BB drop and slackening won't be as extreme. Motor up anything your legs and lungs can handle with new found rear wheel traction.

Why slag free swag?:rolleyes:

ummm, as your doctor i recommend against riding with a scaphoid fracture.

Dec. 7, 2016, 10:42 a.m.
Posts: 5635
Joined: Oct. 28, 2008

Anyone riding plus size tires on the shore right now (in the snow/ice?) Seems crazy to me but I had to ask. Fatbike might be fun on the easier runs tho?

I guess I am asking because I wonder if plus size is the goldilocks size for winter conditions or once the white stuff is down it's fat bikes or nothing.

Clearly, I haven't ridden in this stuff before with my 29er or 26er tires of maximum 2.3 width.

Wrong. Always.

Dec. 7, 2016, 11:02 a.m.
Posts: 48
Joined: June 16, 2007

I went riding last night with 2.8 Minion DHF's on my Primer last night. Awesome sauce. I was able to keep going quite a bit easier than my buddy with 29 2.3 Minion DHRII's… Airing down to 12.5/14 psi front/rear in the plus tires probably didn't hurt either. ;)

Dec. 7, 2016, 12:14 p.m.
Posts: 2412
Joined: Sept. 5, 2012

how about a couple images of the 2 tires side by side ?


Dec. 7, 2016, 1:28 p.m.
Posts: 26382
Joined: Aug. 14, 2005

A bit of tyre nerdery.

Forum jump: