Honest question about 650b

[Poop~Ghost]

What's the difference between running a 27.5 rim with a lower profile tire and running 26" rim and a taller tire?

I have seen folks put 27.5" wheelset on my bike - 2011 Spec. Stumpy Elite and get just enough clearance to be fine on the rear triangle. I've run some big ass maxis that barely clears on the rear with 26" stock wheelset.

I'm mostly curious if there's a noticeable difference between those 2 scenarios.

[Anospa]

I noticed the same thing on Saturday. Someone was demoing a 650b RM bike and I held my front wheel up to theirs and with a 2.5 DHF on my bike, they were the same sized wheel. I think with an equatable sized tire on the 650b bike, it'd probably be an improvement, but otherwise its probably the same (when people try to stick 650b wheels and pinner tires on 26" frames).

When you get into a bike specifically designed to accommodate 650b wheels and tires, then its gonna change I bet.

[rideit]

The answer all lies in the tire size. My 650 tires are the same as a 2.8 DH mt bike tire, but about two pounds lighter....

[JeffreyJim]

Technically, there is. It comes down to contact patch and how that contact patch is coming in contact with the ground.

Think of it like this. Two skis are 190CM. One is 120 under foot (same as a 2.5" 26" tire) and one is 100 under foot (650b 2.3" tire) . Are they going to ski differently? (yes) I use this analogy because a 2.25ish 650b is going to be same in diameter as a 2.5" tire on a 26" wheel. Hence the length of the contact patch is the same, it just varies in width and tire weight.

Now, how much this translates to on trail performance is up in the air. To me, you put the fast guy on a 26" bike or a 650b and we aren't going to see a major difference in times between the two rigs. Its a great way for the bike industry to get more of your money though...(watch, I could be completely blown out of the water when I actually spend time on a 650b rig)

[marshalolson]

if you think a 2.1 xc tire and a 2.6 dh tire ride the same, just because they have similar outside diameters, then you are crazy!

the difference between wheel sizes lies in comparing like-sized tires. i.e. 2.1 vs. 2.1 and 2.4 vs. 2.4

[Anospa]

if you think a 2.1 xc tire and a 2.6 dh tire ride the same, just because they have similar outside diameters, then you are crazy!

the difference between wheel sizes lies in comparing like-sized tires. i.e. 2.1 vs. 2.1 and 2.4 vs. 2.4

Essentially what I was trying to say. Sticking 650b wheels into a 26" frame and running pinner tires detracts from that frame's potential if it were being run with adequate tries.

[JeffreyJim]

if you think a 2.1 xc tire and a 2.6 dh tire ride the same, just because they have similar outside diameters, then you are crazy!

the difference between wheel sizes lies in comparing like-sized tires. i.e. 2.1 vs. 2.1 and 2.4 vs. 2.4

But is that really the equivalence? 2.1 650b ~= to a 2.6 26"?

I thought it was less...

Edit: Check this picture. http://brimages.bikeboardmedia.netdn...05-600x376.jpg 2.1 wildgripper 26" compared to a 2.1 Neo-Moto 650B...to me, that's not a massive difference...

Edit 2: Some checking around and it sounds like a 2.3 neo-moto is pretty damn close to the same diameter as a 2.5 minion. (which a lot of guys run on their "enduro" or "trail" bike.) So again, is it different? Sure. Is it a massive difference? Not really...

[marshalolson]

Technically, there is. It comes down to contact patch and how that contact patch is coming in contact with the ground.

not to go too over the top with this, but to flesh out the analogy a bit:

the same width tires, with the same air pressure, will have a longer (by definition) and narrower (since you weigh the same, and there is a fixed amount of air pressure in the tires) contact patch on a bigger wheel diameter than the smaller one.

maybe the analogy would more be like in:
185cm 120mm ski (26")
187cm 110mm ski (650b)
190cm 95mm ski (29er)

so while that is still not enough info to have any idea how they will ride (rocker profile, flex pattern, etc etc) same goes for tires (casing, tread, etc).

if the bike industry actually wants the 650b stuff to hold, its on the tire manufacturers to offer real tire designs in real casings. 600g xc treads will not cut it. and really the tire dudes are the ones to loose. they are not selling anything new or reaching a new audience. every 650b tire they sell is robbing a sale from an existing model / mold. so yeah. 650b success and failure directly hinges on tire companies acting out of desperation about "loosing market share" rather than actual self-interest.

anyhow, i thought 2.1's on my stumpjumper ran best (BBG front, HM or BBG rear / in the desert) - i mean its basically a slack, long travel XC race bike. when i converted it to 650b, i stuck 2.1s on there...

but yeah, i posted a bunch of measurements a couple weeks ago. don't remember the thread. a 2.25 RR is about .25" larger radius than a 2.5 minion.

[Poop~Ghost]

Thanks guys, interesting stuff (at least to me).

[shirk]

Re Neo-Moto tires. I am pretty sure I've read that the sidewalls on the Pacenti Neo-Moto tires were intentionally a bit short to allow them to fit into more frames.

I recall seeing a picture of 2.35 Nobby Nic in 26-27.5-29 all side by side. But can't find it.

[lph]

marshall, tire seclection not withstanding, sounds like bike manufacturers are moving their selections towards 650b and 29er and, from what I understand, will even be phasing out the 26" selections. I heard from a LBS owner that giant will be discontinuing the anthem and trance in 26" and they giant reign will soon be released as a 650b.

is this accurate?

[shirk]

I heard from a LBS owner that giant will be discontinuing the anthem and trance in 26" and they giant reign will soon be released as a 650b.

is this accurate?

It actually makes sense to drop some of those bikes.

26 Anthem? It's a xc race bike, just go 29'er.

This is how I see the future going.

26 DH/DJ

27.5 Trail/AM

29 Trail/XC

[JeffreyJim]

not to go too over the top with this, but to flesh out the analogy a bit:

the same width tires, with the same air pressure, will have a longer (by definition) and narrower (since you weigh the same, and there is a fixed amount of air pressure in the tires) contact patch on a bigger wheel diameter than the smaller one.

This I agree with.

maybe the analogy would more be like in:
185cm 120mm ski (26")
187cm 110mm ski (650b)
190cm 95mm ski (29er)

This I don't agree with. As you increase the width of a tire, you also increase the amount of sidewall and the overall diameter of the wheel (we all agree on this).

Hence, why I say the "length" stays relatively the same when comparing a 2.5" 26" tire to a 2.2-2.3" 650B (long-ways-contact patch/diamter about the same) but the width of the contact patch changes. (obviously)

Its a silly distinction, I know, but I had to mention it.

End of the day, yeah, it is different. Not enough for me to run out and dump my 26"ers yet but hey, maybe I'll be shown wrong. After all, to me, the difference between a 66.5 degree headtube angle and 68 degree headtube angle is "like" vs "don't like". Point is, just because its a small tweak doesn't mean it wont matter...after all, small things can make a big difference...

[lph]

Feel the same way JJ.

I think I am pretty much gonna have to demo all future purchases. right now I am pretty happy with what I am riding. all bikes could use some tweaking, but I aint changing just cause the bike manufacturer wants me to.

the next move I make is getting rid of my Intense SS 1. it is a pig and I would like a capable 6" bike that can be taken on longer rides with some climbing. I do it on the SS, but don't enjoy it. Pending numbers on Giant Reign 650B, that or some other 650b might be my next 6-7" bike.

[marshalolson]

jeff-

i was refering to the same width tire at the same pressure.

look at the numbers man. the contact patch on a 2.5 minion is about 5% shorter than a 2.35 650b hans dampf.

[JeffreyJim]

jeff-

i was refering to the same width tire at the same pressure.

look at the numbers man. the contact patch on a 2.5 minion is about 5% shorter than a 2.35 650b hans dampf.

Ah, not disagreeing there. Just saying, using the ski analogy, assuming same width tire between the 3 wheel sizes, it'd be more like

26" = 185cm 110mm ski
650B = 189cm 110mm ski
29"= 195cm 110mm ski

(width stays the same, running length changes...but my analogy is pretty dumb anyway...)

[nickwm21]

if the bike industry actually wants the 650b stuff to hold, its on the tire manufacturers to offer real tire designs in real casings. 600g xc treads will not cut it. and really the tire dudes are the ones to loose. they are not selling anything new or reaching a new audience. every 650b tire they sell is robbing a sale from an existing model / mold. so yeah. 650b success and failure directly hinges on tire companies acting out of desperation about "loosing market share" rather than actual self-interest.

Good point, and the reason it took years to get good 29er tires...

sent from the future using my mind powers

[marshalolson]

Ah, not disagreeing there. Just saying, using the ski analogy, assuming same width tire between the 3 wheel sizes, it'd be more like

26" = 185cm 110mm ski
650B = 189cm 110mm ski
29"= 195cm 110mm ski

(width stays the same, running length changes...but my analogy is pretty dumb anyway...)

if you have a fixed tire pressure, and the contact patch is longer, and the bike/rider total weight don't change, then the contact patch MUST be narrower.

think about it. 200lbs @ 20psi requires 10sq inches for buoyancy, or 5 sq inches per tire if equally weighted.
if the contact patch is 5% longer (which it is for each wheel size, give or take), than the contact patch MUST be 5% narrower to maintain the same overall surface area.

so while the tire width does not change, the contact patch with the dirt does actually get narrower as you go for a larger diameter wheel.

[farmguy]

As a 650b owner, I can tell you there is a difference. I also have a 09 Spec Epic expert. My Jamis Nemis 650b is set up with American Classic wheels 1300+ grams, Racing Ralph's tires at 450 grams a tires. Epic is set up with Rocket Rons and DT swiss wheels. The 650b wheel size takes the edge off the bikes handling, you no longer have a "twitchey" feeling while blasting downhill, just enough of a difference for you to relax and let things go a little more. Can you go just as fast on a 26? Yep! Uphill, it depends on the trail, tight twisty technical stuff will favor a 26" tire as they are smaller and easier to turn, 650b a little tougher, 29'r tougher yet. I have done 2 races this spring, one course favored my 26, the next was a dream on my 650b. There are good and bad bikes being built regardless of tires size, just like skis, test ride before buying.

[JeffreyJim]

if you have a fixed tire pressure, and the contact patch is longer, and the bike/rider total weight don't change, then the contact patch MUST be narrower.

think about it. 200lbs @ 20psi requires 10sq inches for buoyancy, or 5 sq inches per tire if equally weighted.
if the contact patch is 5% longer (which it is for each wheel size, give or take), than the contact patch MUST be 5% narrower to maintain the same overall surface area.

so while the tire width does not change, the contact patch with the dirt does actually get narrower as you go for a larger diameter wheel.

Good point. Never thought it'd be enough to matter but I bet you are right.

[marshalolson]

This is how I see the future going.

26 DH/DJ

27.5 Trail/AM

29 Trail/XC

my personal crystal ball is:

DH(180+): 26" 2ply 1100g+ tires
long travel trail bike (150-180): 26" 750-1000g tires
short travel trail bikes(120-160): 650b 600-850g tires
XC race bikes(<110): 650b <600g tires
and the occasional oddball retrogrouch 29er hard tail

a 650b tire is about the same outer diameter as a 700c road bike wheel. a 29'er is SIGNIFICANTLY bigger than either. why anyone would want a wheel that is about 7% bigger than a road bike wheel on anything, unless its somehow more smooth, and less steep than a road is beyond my ability to understand and fathom.

[JeffreyJim]

my personal crystal ball is:


a 650b tire is about the same outer diameter as a 700c road bike wheel. a 29'er is SIGNIFICANTLY bigger than either. why anyone would want a wheel that is about 7% bigger than a road bike wheel on anything, unless its somehow more smooth, and less steep than a road is beyond my ability to understand and fathom.

This I fully agree with. My "XC race bike" is a hefty 26-27lbs (steel 29" hardtail). Still, I was always surprised that I was basically as fast on my 30-32lbs Mojo HD with smooshy suspension on steep long climbs. Why? I felt keeping that giant 29" wheel turning over & over was a whole lot of unnecessary work. You are basically accelerating and decelerating the whole time during a climb like that anyway. Never really having your forward momentum reaching a "critical mass" where you are maintaining much of any real 29"-advantage-laiden-speed.

I may throw a 650b wheelset on that bike. Just to see whats up. I bet it rocks... (and it'd make it L-O-W)

[phatfreeheeler]

I'm in Marshal's camp on most of this, except the 5% thing I like exact numbers. Assuming the same 2.35" tires on all 3 rims you end up with...

26 = Actual Diameter 26.7"
27.5 = Actual Diameter 27.7", 3.7% bigger than 26"
29 = Actual Diameter 29.2", 9.3% bigger than 26"

If they are going to call it 27.5 then we need to stop calling 26" 26 and start calling it 26.5...Stupid marketing BS trying to make something more than it really is. It's WAY closer to a 26er than it is to a 29er.

Along with Marshal's point that the contact patch changes in shape as wheel diameter increases, I believe it makes total sense that we should be able to run narrower tires and get similar feel during transition from center to outer knobs as wheels get bigger.

So using the same basic idea, I get that if you run a 2.35 tire on a 26er and want a similar transition feel, you could run a 2.25 tire on a 27.5 or a biggish 2.1 on a 29. Thinking about it this way I do feel like my 2.2 29er tires feel pretty good width wise, but they are Conti's and I've never used them on my 26ers before so I shouldn't read too much into it. On my 26ers I have settled on 2.35-2.4" actual width as my happy place to ride aggressively. I went with 2.2's on the 29er thinking that was plenty XC for a carbon HT, but maybe I am being overly safe on width to be as fast as possible.

[dfinn]

why anyone would want a wheel that is about 7% bigger than a road bike wheel on anything, unless its somehow more smooth, and less steep than a road is beyond my ability to understand and fathom.

I'm going to give the wagon wheels a try only because of what I've seen with my own eyes. Following the same rider, down the same upper mountain whistler trails, I was able to hold his wheel on his 8" dh rig, on his long travel 29er he was pulling away from me. Fast is fun, can't argue that.

[shirk]

my personal crystal ball is:

DH(180+): 26" 2ply 1100g+ tires
long travel trail bike (150-180): 26" 750-1000g tires
short travel trail bikes(120-160): 650b 600-850g tires
XC race bikes(<110): 650b <600g tires
and the occasional oddball retrogrouch 29er hard tail

a 650b tire is about the same outer diameter as a 700c road bike wheel. a 29'er is SIGNIFICANTLY bigger than either. why anyone would want a wheel that is about 7% bigger than a road bike wheel on anything, unless its somehow more smooth, and less steep than a road is beyond my ability to understand and fathom.

Wait what? I thought you didn't like the 650b. Or is it just that you like it in principal but waiting for good tire availability?

I agree with the above, but I think there will still be a strong 29'er following in the XC to light trail bike crowd.