29 inch front wheel on a 650b bike?

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29 inch front wheel on a 650b bike?
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flag blackmountainsrider
Posted: Dec 15, 2016 at 3:42 Quote
I'm toying with the idea of trying a 29 wheel on the front of my 650b orbea rallon. I love this bike, it's fast and composed allready, but I love the big wheels on my xc bike. (Whyte t129)
I was wondering if anyone on here has tried anything similar? I can see it being the best of both worlds.
The orbea currently runs a 160mm fork with a very low bb. My issue is whether to get a 160 or 150 mm air shaft to try in my 29er pike.
It will only really be used for 'enduro' type riding where I'm not bothered about speed on the ups or easy flat sections.

I also don't care too much for jumps etc.


What do you reckon?
Has anyone else done anything similar?
flag zsandstrom
O+
Posted: Dec 15, 2016 at 8:01 Quote
I think it depends on the reason that you like the big wheels on your XC bike. If it's because it feels efficient and smooth, then you might be disappointed with your new setup. That efficient, fast, smooth feeling has a lot more to do with your back wheel than your front, which it doesn't sound like you're going to be changing. Even assuming that both wheels change size, the characteristics that you enjoy about your XC bike probably have more do with with geometry and suspension differences than wheel size.

Sorry to rain on your parade, there. But if you're not going to be satisfied until you've tried it, I'd see if you can find someone who'll let you borrow a matching fork and wheel for a day just to see what happens.
flag Xorrox
O+
Posted: Dec 15, 2016 at 14:32 Quote
I’m trying this very thing on my Scott Genius 720. I'm going to see if I can get any kind of ride in here on the snow tonight with the new 29er front end but realistically I won’t know the real pro’s and con’s until I get some proper rides in once the snow is gone.

Here is what I know so far:

If you change to a 29er fork with the same travel and the same tire size as you have on your 27.5” bike right now, your front end will now be 30-35 mm higher. Your horizontal reach (on flat ground) will decrease and your vertical stack height will increase. Your bottom bracket height will increase around 10-15 mm as will your stand over height. Your head angle will become roughly 1.5 to 2 degrees more slack. Your wheelbase will also increase. You may be able to drop your BB back down somewhat with shock offset bushings if these work with your shock and linkage arrangement, but this will make your head angle even more slack. You could compensate for the slack head angle with an offset headset run in the steeper direction such as those made by Works Components and you may be able to compensate somewhat for the higher handlebar height by going to no spacers under the bar, flipping your stem upside down if it is angled up or replacing riser bars with flat bars.

So, given all that above, why did I want to try changing my bike other than the need to constantly tinker? Here is what I hoped to accomplish:
1) Greater resistance to going over the bars on steep, rough downhill terrain with a more centered riding position in these conditions. (Currently on my bike I’m always hanging way over the back which can make it hard to turn).
2) Better ability to roll over things, hopefully both downhill and uphill and at both low and high speed.
3) Maybe (if I’m lucky) having a slightly smaller rear wheel will somehow make it better in turns as some of the reviews for the Foes Mixer 27.5 / 29er Trail and Enduro bikes talk about.
4) Maintaining the strength, stiffness and quick acceleration of a 27.5 wheel in the back with the rollover capability of a 29er in the front.

I can’t wait to see how this experiment turns out.
flag blackmountainsrider
Posted: Dec 15, 2016 at 23:26 Quote
Thanks to you both for the replies.

Zsandstorm , it is maybe partly what you say, but I also find it incredibly capable, fun and fast going down technical trails which are normally the territory of bigger bikes. I can only really attribute this to the bigger wheels as it's far more capable than other 120mm travel bikes I've used.

I guess I'm hoping dome of this will rub off onto the Orbea.

Xorrox - interesting points you've made there. I hadn't thought about a couple of them. I have a friend who is running this setup on a nicola and he loves it. I'd love to hear your thoughts.

I'm going to set the pikes from my xc bike to 140mm, as i have an air shaft and this will keep the same axle to crown, and only increase the front end height by 20mm. If I like this I can then maybe think about buying a 150mm air shaft.


I'll report back.
flag yeti-monster
O+
Posted: Dec 20, 2016 at 13:25 Quote
I had a very similar discussion with a motorcycle enthusiast. It turns out all categories have toyed with it. Especially successful in motor cycle endurance off road. Paris Dakar stuff.
flag Xorrox
O+
Posted: Dec 27, 2016 at 19:51 Quote
I finally had my first real ride on my 2015 Scott Genius 720 with a new 29er front, and my existing 27.5 rear. To review, this is what I did:

- Replaced the 27.5" 160mm Pike I had on the front (stock was a 150 mm Fox 32 Evolution) with a Boost Rockshox Lyric Dual Position Air 160 mm 29er fork with a 29" DT Swiss EX471 rim and Magic Mary.

- At the same time I removed the after market 1.5 Degree slacker Works Components headset I had put in previously and put back the stock head set. The net result with the taller front end but steeper headset was a slightly slacker front end (around 65.5 degrees after the new 29er front end). The stock Scott Genius had quite a steep head angle to start with which helped out with this.

- Finally, I removed the 750 mm wide 25mm riser bar I had on previously and replaced it with a 785 wide 13 mm riser bar and removed a 10mm spacer under the stem. This lowered the handlebar height by roughly 22 mm which helped to offset the roughly 30mm rise from the longer Axle to Crown fork length and larger tire diameter. The wider bar theoretically should also help move my weight balance forward very slightly similar to changing to a longer stem without the negative side effects. I also moved my seat forward as far as I could (roughly another 10 to 15 mm).

So, all that said, here is what I noticed on my first real ride. Keep in mind this ride was on easier fast and flowy trails versus my North Shore home trails which are slower and more technical. I'm still waiting for the the snow to melt at home so I was happy to get any ride in.

- First of all, I have to say that I haven't seen any down sides to this modification yet. This might not be the most positive first comment but I was really afraid that I would actually make the bike practically unrideable in some situations which would be a major downer after spending all the time and money planning and executing the modification. The first thing I noticed is how big the front tire looked when I was riding but I soon got use to it and otherwise it felt really natural. The longer, lower bar postion and further forward seat all combine to very closely mimic my previous body position and balance on the bike.

- I also noticed that climbing over smaller rocks and rock ledges seems to be easier. I can now focus on making sure the rear tire does not get hung up as the front seems to roll up and over things better without getting too light. I'll have to verify this once I can ride at home and see how it climbs over all the roots on our climbing routes there.

- The front tire seemed very responsive and neutral, almost more so than with my previous set up. This makes some sense because even though the head angle has gotten almost 0.5 degree slacker (even with removing my previous 1.5 degree offset), the new fork has significantly more offset. Also, the longer bar provides more leverage which balances out the higher forces required to move the larger tire.

- (Edit 2016 03) Another thing I noticed when plowing into rocks, roots and other bumps at high speed is that the front wheel / front end tends to be pushed up and over these more rather than compressing the fork. Part of this is probably down to the fact that I still haven't got the Lyrik DPA as buttery in the first part of the stroke as my very broken in Pike DPA was but I think this is also due to the higher front axle path. This trait is good and bad:
On the positive side the front end feels very lively and playful when popping off small trail features and is less likely to get hung up or send you OTB (one of the biggest positives and one that I was counting on when I did this modification). The possible down side is that you have to focus on weighting the front end in situations where you need to keep the front end planted while going over rough terrain for some reason. I didn't really notice any issues with grip because of this though and it also seemed to help lift the front wheel over diagonal roots that would have previously deflected the front wheel to the side. After a couple rides I had adjusted to the new handling feel and actually nailed a number of PRs on my fourth day of riding.

- The single largest difference I can point to is a slightly more centered riding position, especially through fast corners. Previously I really had to hang off the back of the bike to get it to turn but now for some reason I can stay centered and the bike just seems to turn more naturally. Also, previously the sweet spot between front and rear grip was really hard to find while now it seems easier to find this balance point. This is pretty subtle though so I really will have wait to get back on my home trails to get a better feel for the differences.

So, currently I'm still on the fence if this was all worth it but generally speaking I'm happy with the changes and will have to do testing under more conditions to get a better read any benefits and / or downsides.
flag nathan010
FL
Posted: Jan 2, 2017 at 10:41 Quote
Some pictures of before and after? Toying with a 29er front on my orange alpine.
flag Xorrox
O+
Posted: Jan 2, 2017 at 17:14 Quote
nathan010 wrote:
Some pictures of before and after? Toying with a 29er front on my orange alpine.

This is not the best comparison as the pictures were taken with completely different background and positions but here is what I have right now:

Bone stock with 150 mm Fox 32 fork and 2.25" x 27.5" tires/wheels:
2015 Scott Genius -Stock with 150 mm Fox 32 fork and 2.25 x 27.5 tires

With 160 mm Rockshox Lyrik fork 29" x 2.35" front tire/wheel and 27.5" x 2.30" rear tire/wheel:
2015 Scott Genius 720 - 29 Front Wheel with 160 mm Lyrik Fork

The difference is actually more subtle than you expect.
flag Xorrox
O+
Posted: Jan 3, 2017 at 20:50 Quote
Better Comparison:

2015 Scott Genius - Bone stock with 150 mm Fox 32 fork and 2.25" x 27.5" tires/wheels:
2015 Scott Genius -Stock with 150 mm Fox 32 fork and 2.25 x 27.5 tires

2015 Scott Genius - With 160 mm Rockshox Lyrik fork 29" x 2.35" front tire/wheel and 27.5" x 2.30" rear tire/wheel:
2015 Genius 720 160mm DPA Lyric 29er front 27.5 rear
flag ledude
Posted: Jan 3, 2017 at 22:14 Quote
From my experience; a 1.5" increase in wheel size equates to approximately 20mm in travel needed.

26" wheels 180 mm fork
=
27.5" wheels 160mm fork
=
29" wheels 140mm fork

the decreased rollover resistance of larger wheels decreases the amount of travel required.

This allows you to minimize the numerous amounts of change to your over bicycle's geometry.

A 29er won't need as slack of a head angle. Using a travel of 20mm less allows you to maintain the same approximate stack, reach, wheelbase etc.

Most importantly, you won't make your climbs even more shitty by climbing with a floppy front end.

Consider this:

a 2017 Fox Float 34 27.5 140mm has an axle to crown of approx. 529mm
a 2017 Fox Float 34 29 120mm has an axle to crown of approx. 527mm
flag nashwillis
Posted: Jul 12, 2017 at 9:39 Quote
Any update on how you like this set up?
flag tremeer023
FL
Posted: Nov 12, 2017 at 9:09 Quote
Just stumbled upon this forum so sorry for the late message but I've been running 29 front and 650b rear (semi-plus) since March this year on a 2017 Ragley Mmmbop.
Frame is a 650b but with good clearance and designed for 150mm fork. I'm running a 29r 140mm rs Yari with 30% sag.
Front wheel is 29 with 30mm id rim running Schwalbe hans dampf 2.35 (actual 2.45 - 2.5), and rear is 650b with 35mm I'd rim with wtb breakout 2.5 (actual 2.6ish).
Rides great like this. My only complaint is with the 51mm offset fork but that's the only option with the Yari, I'm nitpicking though.
I'll try and get some pictures posted if I can figure out how to on my tablet.
flag troydevinci
Posted: Dec 2, 2017 at 8:02 Quote
Did this to my troy but with a Fox 36 9er and a 35 internal rim and a2.8 dhf with the usual bar changes 18 psi it's insane.it 27.5 plus.rim diameter is 28.5
flag sdken
Posted: Dec 4, 2017 at 10:22 Quote
blackmountainsrider wrote:
I'm toying with the idea of trying a 29 wheel on the front of my 650b orbea rallon. I love this bike, it's fast and composed allready, but I love the big wheels on my xc bike. (Whyte t129)
I was wondering if anyone on here has tried anything similar? I can see it being the best of both worlds.
The orbea currently runs a 160mm fork with a very low bb. My issue is whether to get a 160 or 150 mm air shaft to try in my 29er pike.
It will only really be used for 'enduro' type riding where I'm not bothered about speed on the ups or easy flat sections.

I also don't care too much for jumps etc.


What do you reckon?
Has anyone else done anything similar?

I haven't done this but I don't see any problems doing it if you're okay with the geometry changes. Foe's Racing sells their bikes like this, 29 front, 27.5 rear.
flag allstatecdl99
O+
Posted: May 15, 2018 at 13:34 Quote
I was rebuilding a rear wheel for my 27.5 anyway so I put a 2.8 bontrager chupacabra and tossed it on the back of my Santa Cruz Superlight 29er. Only did 1 ride yesterday but it was awesome! Now the advantages/disadvantages of this setup will probably differ by bike. For the SC Superlight which is a XC build with 100mm rear travel I thought it was a great setup.

First off, the wheel just felt snappier and accelerated quicker from standstill which was to be expected. The rear wheel is probably a good inch lower than the front at this point but the added slackness feels great. I found myself taking some new sketchy lines on some of the steep down of my same local trails. There is 1 short but very steep roller that makes my rear tire start to come off the ground as I go down it with the 29 inch tire out back....this setup kept the tire grounded on the same roller. Sweet!

The bike is just more comfortable under by butt and the suspension effects of the plus tire make for a smoother and FASTER RIDE. Yes I went a lot faster yesterday...safe to say I went down 1 gear my whole ride. A couple technical uphills felt easier going up. There were a few technical sections I didn't clear because I was in too low a gear going into them and couldn't get the power down fast enough. That is what I noticed...I was in lower gears more of the time and going faster...so much so that it actually revealed the vulnerabities of the old front 29er tire I have been using that is need of replacement. This tire is worn and looks like it needs to be replaced but really hadn't given me too many problems so I have still been running it. Well yesterday the faster speeds made me want to change my front tire more than I have ever felt the need to and its because I was going faster.

Final point, I am running 120mm fork up front and as I mentioned its 100mm in the rear. The plus tire out back really seemed to balance the bike very nicely with the 120mm front and the added slackness kept the bike nimble.

I'll say it again, I can see how every bike geometry may not benefit the same for this setup but for my Superlight it has been a sweet upgrade I look forward to riding for a while. Picture posted in my profile.
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