Can 29er MTB frame assembled with 27.5er wheels?

[final forum]

Peter by any chance could we get some pictures of the rear tire clearance. Would love to see how much room he has left over.

[PeterXu]

Finally he sent me couple of pictures.

And this is what he said: 

Hi Peter, the 29" 40mm rims
Are working great. I mounted the chupacabra 29x3.0 tires on them for
My wife's bike, a carver gnarvester which
Is designed for 3.0 tires.

I am attaching a few pictures of the
Clearance on the CS-256 with the
27.5x40mm rims and the WTB trailblazer
Tire ( 27.5x2.8 )
The clearance works but is pretty
Tight. The width of the tire is 66mm
And the internal width of the bottom
Chainstays is 70mm so you end up with
About 2mm on each side.
It works but a frame with wider chainstays

I hope these information would be helpful

[Carbon_Dude]

Thanks for posting those pictures Peter!  Looks a little tight but not that bad, I'd run it on my bike if I wanted to try out the 650b wheel size.

[SportingGoods]

Hi guys,
I'm going to test it on my 29er hard tail. Just one question, would you go with 40 or 50 mm rims (external width).
I'll go with the WTB 2.8 tires, Reba fork and my rear spacing is >70 mm.
I'd be tempted to give the 50 mm a try but I'd like to collect your feedback first. What would be the benefit of both width?
Any idea?
Thanks!

Peter, do I qualify for a discount if I'm the first one to qualify the 50 mm setup and report on the forum ?

[bxcc]

70mm is going to be tight if doable at all. The 2.8 Trailblazer is 66mm wide on a 29mm internal rim. I'm going to try it on the 062 frame once it arrives. My rims are 29 internal.

[SportingGoods]

Agreed, it looks like 43 mm rims would make 70 mm wide tire. Too tight.
It looks like 35 ID is the best option.
I need to make accurate measurements front and rear.

And what about a mix? 43 ID front / 35 ID rear.
Would this show any benefit over a full 35 ID?

[SportingGoods]

Me again!

Just ordered the 35 ID wheelset (EDITED). I am really excited to give this a ride, all reviews say what I need: it's a lot of fun.
I'll still save my regular 29 inch wheels for proper XC racing but will most likely use these semi-fat most of the time.

I'll post pictures and review

EDIT: too excited, 40 is the OD, not ID. Actual ID is 35.

[bxcc]

Great! keep us posted. Which frame are you running and what tires are planning on going with?

[SportingGoods]

I am planning on the WTB Traiblazer 2.8. This will go onto a Flyxii (love that name) FR-202 frame.
I have double checked the rear clearance and it looks like 72 mm on the wide point of the tire (the frame is not straight). This should provide 3 mm clearance on each side of the tire... hopefully!!

One key point I have not mentioned before: I don't run single chainring but double. I anticipate that I'll need to tune the rear derailleur a bit to prevent it to rub the tire

[SportingGoods]

Here we go! I have finally received my 35 ID 27.5" wheelset. First I want to thank Peter from Carbon Speed for the amazing logistic support. Way superior to what you would expect from a local shop.
Anyway, my wheels came in very well packaged, in one piece, this week.

I have already set up the front wheel (I am running out of Notubes tape to seal the rear rim, coming up tomorrow). I have done my first ride today (yes, front 27.5+ / rear 29) and I am VERY surprised. Over the exact same trail 2 days ago I have been quite faster uphill and same speed downhill (pretty steep and technical trail in the Alps). I expected the opposite.
My feeling was that I had a gain in control uphill as the fat tire absorbs everything, but I had not realized that it enabled me to go faster. I did not feel the 200 g added weight over my 29" wheel. Downhill, I had a lot more stability as the speed generated a stronger gyro effect then 29" wheel (again not sensitive at low speed uphill). I could really take lines a lot more straight without being bounced in every direction like it sometimes feel with my light 29" wheel. Still I was not faster! Maybe I lack here the rear wheel.

I'll keep you updated as soon as the rear wheel is setup. I'll highlight how it fits in the frame and with the rear derailleur.

In the meantime here some comparison between 2.8x27.5 WTB Trailblazer on 35ID and 2.25 Nobby Nic on ZTR Crest. See the nice contact patch, and nice profile of the tire on these rims...

[SportingGoods]

Final!!!! You can call me Happy Man It fits even better then I thought at the rear. 5 mm on the left, 4 mm on the right. That's just a rock solid setup. I plan on keeping the WTB 2.8 at the rear (a fast large tire) and bump up the front to a larger, more grippy 3" when the offer will be better (ideally a Nobby Nic, but a Rocket Ron would do it).

Final built


Drive side, see how the rear derailleur nicely clears on the granny (actually better then with 29" wheel as 27.5+ is a little shorter). 4 mm space. Left side, a safe 5 mm spacing.

[bxcc]

Awesome setup. Thanks for the pictures and measurements. What is the clearance between the chainstays on that model? I plan on getting the Trailblazers for my 062 frame once they are back in stock. Right now I am building it up as a 29er but will swap to the 27.5+ setup when the trail bike goes down for winter maintenance.

[SportingGoods]

Well, it is hard to give a number for frame clearance. As I mentioned before the chainstays are not parallel. On the widest point of my 29" tire (ZTR Crest with 2.25 Nobby Nic) I seemed to have 72 mm. But the 27.5+ being a little shorter, the widest point is closer to the wheel axle so I get a little more clearance then I thought.
Also, it will depend on the profile of the tire. The position of the wide point of the tire will vary.

Anyway, I don't plan to up the rear. I like it safe as it is. But I will definitely get a larger front tire when I find what I want (model, price).

Also, it is a total 400 g added to the bike over the 29" setup. It's totally worth it.

[Carbon_Dude]

SportingGoods, thanks for your posts!  You've got me really interested in purchasing a set of 27.5 x 35mm ID wheels and throwing them on my IP-057 with some 27.5+ tires.  After demoing a few fat bikes, I think I like the in between tire sizes better for the trails in my area.  Those fatter +tires should roll over the rocks and roots very nicely.

[SportingGoods]

Let me try to describe how it feels to ride 27.5+.
1/ With the right (high quality) equipment it is not slower then a good set of 29 wheels. I have done again the same loop I did last week (a short 9 km but very tough and technical loop, uphill and downhill in the Alps).
Full 29 on 8/31: 38"57'
29 rear, 27.5+ front on 9/3: 36"18'
Full 27.5+ on 9/7: 34"33' (I know, it's an amazing difference that needs to be connected to my desire to perform on those wheels, but still, what a difference).
With the front 27.5+ I was faster uphill, same downhill. With Full 27.5+ I am faster both uphill and downhill.
2/ Feeling is in-between 29 hardtail and a long travel full suspension. Right in the middle. It is the exact amount of comfort you need uphill (to climb over roots, rocks). It is NOT enough to enable hard jumps like a full sus would do. From a control stand point, they are different too, a lot of control through grip at low speed (uphill), and a lot of control downhill thanks to the stronger gyroscopic effect (it was a little odd at first, you need to get used to it).

I was used to get people look at my bike, amazed to see a no-brand bike; now I get a double dose with these tires that no-one has ever seen before.
So, I highly recommend it to anyone who wants to push a hard tail further. Still, if you want to ride really hard, a full sus is the only way to go.