Can 29er MTB frame assembled with 27.5er wheels?

[SportingGoods]

WTB TB is definitely a rear tire (fast rolling). The NN at the front made a great difference in control on the DH sections. Honestly, if my frame was wide enough I would use a NN in the rear as well. But 65 mm is the max that will fit.

My current dream bike is CS-M04 frame with Eagle drive train, Pike fork and 2 Nobby Nic. I am convinced that a short travel FS is ideal with 27.5+. But that's a lot of money (frame + drive train + fork + hubs) 

[Carbon_Dude]

After removing my wheels and taking careful measurements, I have updated my post #46. 

[Patrick C.]

Well, they are definitely fatter, but I have not had a proper ride yet so I can't tell how much difference it makes.  I ordered the HR740C rims from Peter at xmcarbonspeed.com and built them up with XT M8000 hubs and DT Swiss Revolution spokes.  Front tire is the 2.8 Nobby Nic, and the rear is the 2.8 WTB Trailblazer.  I got the hubs, spokes, and NN tires from Bike24.com- good prices and everything was correct.  Shipping time was a few days longer than a US store would have been, but it didn't delay anything. 

I considered using DT Swiss 350 hubs for these wheels like I did on my first set, but in the end decided to go with the XT hubs.  The M8000 freehub is 36 POE and about 30 g heavier than the DT Swiss 350; the XT front hub is also about 30 g heavier than the 350 counterpart.  Of course the big difference is price- the pair of XT hubs was under $70, or a little less than a DT Swiss 350 front hub.  The trade off here is about 60 grams for about $200.  I have not taken the hubs apart yet, but I plan to open them up and make sure everything is greased properly before I take a real ride. 



Building the wheels was about the same as the first time- this is only my second set, with about a year and a half in between.  It wasn't fast, but I can brag to everybody at the trailhead that I built these wheels.  (of course, I won't be bragging if I'm walking back )   I didn't run into any problems.  The given ERD number of 545.6 is good (though I question the significant figures)- I measured it at 546.  I had to dig quite a bit to get all the measurements for the XT hubs, but eventually found what I needed in Shimano's online manuals.  I used the DT Swiss calculator and ordered spokes before getting the rims or hubs in hand so I was taking a bit of a risk, but all of the given measurements were correct so the spokes fit.  I used 1" wide Gorilla tape with a couple of inches overlap on each side of the valve.  This leaves a bit of a gap on the edges, but it completely fills the center channel.





The rims both weighed in at 455 g.  The hubs were 170 g and 320 g, finished wheels were 790 g and 945 g, or 1835 for the set.  Tape, valve stems, and skewers brought them up to 865 g and 1025 g.  The 2.8 Nobby Nic is 825 g, the Trailblazer is slightly more (a little over 900) but apparently I didn't write it down. 

The 2.8 Nobby Nic is tight in front with a 2014 Rockshox SID.  Same in the back with the Trailblazer- your wheels better be true and dished properly.  Getting the tires on the rim was hard, but not unreasonably so.  No swearing was required.  They take A LOT of sealant- I put about 4 oz/100 ml of homebrew sealant in each.  I started with 2 oz in the NN and it wasn't holding, but 2 more seems to have done it. 



Geometry seems to be pretty much the same- I'm not confident in my BB height measurement, but it is very close.  The front fork angle (measured with the level on my phone) is the same with the 27.5+ in the front and the 29 wheel in the back as with both 29 wheels, so the final tire circumference is very close to the same.

Continental 2.4 X-King and 2.8 Nobby Nic comparison-




It started raining before I could take a quick ride through the woods- maybe tomorrow.

[Patrick C.]

Forgot to add, service from Peter was excellent as always.  I received the rims 2 weeks after ordering.  Well packed and protected.

[Carbon_Dude]

Great post Patrick C!  Thanks for sharing.  Another future purchase of mine will be a set of 40mm 27.5 wheels from Peter and some 2.8" tires.  Now that I know I can use them on either my -036 or my -057 (just like your frame).

Let us know what you gained in tire width and how much extra grip you feel.  Also, let us know your impressions of ride quality.  Those bigger tires should provide a noticeable improvement.

Lastly, what is your measured clearances front and rear?

[Bertzhong]

  you can do it ,  but what my sugestion is pleaes do not do like that. why the 29er frames be mounted with 29er wheelset ? because the control.
Honestly speaking, I used my 27.5er wheelset on my 26er frame, but it is not very comfortable to control it when you riding, especially when turning.
and like some guys said, the BB will be closer to the earth. it is easy to damage it .
anyway, it is a interesting idea.

[Patrick C.]

First ride was good-  I started with around 18 psi in the front and 20 in the rear, which was a bit too high as the bike was still too bouncy over roots and rocks.  I got a bit of tire rub in the rear after I hit the first rough section, and had to stop to re-true the wheel.  There is almost zero margin for error- I don't have a good set of feeler gauges to check, but I probably have about 1 mm on each side of the tire.  After a couple of adjustments I had no more problems with rub, and after lowering the pressure a bit it felt better going over roots and rocks- it's still rough, but the extra air volume definitely takes the edge off and smooths out the ride. 





The bike felt great- handling and grip were awesome.  Control is excellent- it feels very similar to the 29er wheels, but just a bit heavier to steer and lift the front wheel.

For the second ride (today) i decided to drop the pressure to 15 f /16 r which might be too low for me (200 lbs).  It felt great for the first two miles or so-  I was definitely taking rougher lines that I would have before.  So of course, I cut the rear WTB tire.  I did it on this rock, riding over the top of the three instead of going beside them.  As I hit the last one it didn't feel that bad, but I felt sealant spraying my leg right away.  The tire has a small puncture on the tread and a small cut on the sidewall near the bead.  There was no damage to the rim, but it looks like the tire got pinched all the way up to the rim.  I walked back to look at the rock and it doesn't look that bad- it has a bit of a sharp edge, but I must have been going at just the right speed over the wrong section.   







The tire wouldn't seal and I wound up walking back to the car, but it was less than a half mile so it was easier to just walk back than to try to put a tube in.  It held air, but any time I pumped it above 5 psi or so it would start leaking again.  Neither hole looks too bad, so I'm hopeful the latex will seal up overnight or the tire can be salvaged with a patch. 

So far I think the mid-fat tires are a nice change, but I'm not going to get rid of my 29er wheels.  They do look skinny to me now, though

[cmh]

Curious if the new Stan's race formula would have sealed that larger hole. Got some and started testing it.

http://www.notubes.com/Stans-Race-Sealant-Quart-P1977.aspx

[carbonazza]

"Comprised of natural material" means the ammonia smell is gone?

[Patrick C.]

Tire is holding pressure fine this morning.  Looks like I need a larger syringe or some way to get the chunks in there- I'm using the homebrew blend from this thread http://forums.mtbr.com/29er-components/best-tubeless-brew-406115.html , but the syringe I use to put it in through the valve won't suck up the largest chunks from the auto tire slime. 

[carbonazza]

I'm using the homebrew blend

You mean the receipt from 2008 ?-)

Since 5/04 I been running:
1 part Latex mold builder
1 part Slime tubeless
1 part cheap antifreeze
2 parts water

[Patrick C.]

Yes, a lot to go through in that thread

I didn't make any changes, such as adding glitter or mica.  I read through several pages but never found a definitive change to the recipe.

[Patrick C.]

I've come to the conclusion that the 2.8" tire on a 34 mm inside width rim is just too wide for the -057.  I had been switching back and forth with the 29er wheels, but was using the 29er wheels more due to concern about damaging the chainstays. At best I had less than 1 mm clearance on each side of the WTB 2.8 tire, and in many spots it was closer to 0.5 mm clearance.  I bought a dial indicator to put on my truing stand and got the rim to within 0.25 mm, but this combined with runout on the tire is just too much.  The tire rubbed through the paint on one side, but the black underneath is perfectly smooth.  I already got a couple of weep holes on the sidewalls, so hopefully the tire will wear out before the frame .

For anyone considering plus tires on an -057, get a narrower rim in the back.  I don't know how narrow you'll have to go- maybe 25 mm inside width?  Not sure if I will try to rebuild the wheel or what- anyone know what the biggest 'normal' 27.5 tire is? Or is there a new plus tire that really isn't?

I still like the feel of plus tires, and for anyone starting from scratch you should certainly consider plus.  With that said, I don't know if I would do it again.  Maybe if more in-between tires come out a 34 mm inside width rim will be perfect, but today it just doesn't fit.     

While I can tell a difference in the softness of the ride, I think that any improvements in speed were due to improving my skill- I never really ride 'on the edge'.  I don't care about having the fastest time, but with the plus tires it was absolutely easier for me to lean into turns and get a feel for how hard you could push it.  This has improved my riding on the 29er wheels, such that I feel smoother and can carry more speed through the turns. 

I'll continue to ride them, but will have to true them on the bike before every ride, and will not trust them on any long distance rides.

[Carbon_Dude]

Thanks for the update Patrick!  I look at the small amount of clearance I already have on my -057 with 30mm rims and 2.4" tires so I understand why you had only 1mm per side of clearance with 2.8" tires.

I would still consider getting a set of 27.5"x35mm rims and put them on my -036 like SportingGoods did, he said he has adequate clearance in the rear.  Or, I could upgrade my frame and wheels to go full on Plus size.

I still think 3.0" tires are the new standard and 2.4" tires will be for those that have older bikes.

[Patrick C.]

After more adjustments I now have spots worn through the paint on both chainstays.  For now it is just cosmetic (the paint is thicker than I thought!), but if I continue to ride these I'm sure I'll damage the chainstays eventually. 

I think I'll have to shelf these wheels until I get a 2.6 or 2.5 for the rear.  Specialized is coming out with a 2.6" Slaughter, which may be just what I need.