[alien too]

I was looking for advice on which wheel size I should go with.
I will be doing marathon races on it.

 

[Hurricane Jeff]

If I were building a custom or had a choice of tandems with each wheel size, I'd go with the 27.5" size. I ride a 27.5er single bike and am totally sold on the size. With a tandem, you already have slow steering in which a 29" wheel is just going to make it even handle slower.
On my Ventana El Testigo, it has sliding rear dropouts that can accommodate 27.5" wheels, just need a fork to seal the deal.

 

[ds2199]

Wheel size on a tandem

If I were building a custom or had a choice of tandems with each wheel size, I'd go with the 27.5" size. I ride a 27.5er single bike and am totally sold on the size. With a tandem, you already have slow steering in which a 29" wheel is just going to make it even handle slower.
On my Ventana El Testigo, it has sliding rear dropouts that can accommodate 27.5" wheels, just need a fork to seal the deal.

I will add that having a larger diameter front wheel is a big deal relating to a tandem mountain bike. Way moreso than a single bike. I would agree that 27.5 might just be the perfect balance of wheel sizes for single mountain bikes, but for a tandem, where you can't lift the front wheel, the larger diameter wheel (29") has an advantage. Slower handling may be a consequence of riding larger wheels, but I'll take the trade off so that we can roll over certain obstacles that were problematic on the 26" wheels.

To be clear, I don't think there is a "right answer", only personal preferences. For the riding that we do, even if I had a blank slate and were building a new custom tandem, I would certainly choose a 29" front wheel and likely the rear wheel as well (but I suppose 27.5 would be just fine).

For reference, we have owned 26" Ventana ECDM, 29" Fandango and 29" Ventana ECDM.

 

[Hurricane Jeff]

The rollover of a 29er wheel and all the subsequent info about the bigger wheel being faster is only partly true(trust me, I've done my experiments on single bikes).
While true, on a tandem, your not easily going to lift the front wheel over obstacles, your either going to unweight the front end as much as possible, or just ram into them.
I would never ride an off road tandem with nothing less than 5" travel fork, preferably 6"+, so the fork takes up a lot of the impacts.

In my testing on wheel size, while not totally scientific, my results had the 27.5" wheels faster in just about any condition, the only area that the 29er was or seem faster was on climbs with "baby head" sized rocks.
I've been in way too many discussions on this and was told that there is no way it could be this way, "because bigger is always better" i was told, my findings have found otherwise.
I'm not trying to start a debate into which wheel size is best, your results may vary, just thought I'd share my results.

 

[ds2199]

The rollover of a 29er wheel and all the subsequent info about the bigger wheel being faster is only partly true(trust me, I've done my experiments on single bikes).
While true, on a tandem, your not easily going to lift the front wheel over obstacles, your either going to unweight the front end as much as possible, or just ram into them.
I would never ride an off road tandem with nothing less than 5" travel fork, preferably 6"+, so the fork takes up a lot of the impacts.

In my testing on wheel size, while not totally scientific, my results had the 27.5" wheels faster in just about any condition, the only area that the 29er was or seem faster was on climbs with "baby head" sized rocks.
I've been in way too many discussions on this and was told that there is no way it could be this way, "because bigger is always better" i was told, my findings have found otherwise.
I'm not trying to start a debate into which wheel size is best, your results may vary, just thought I'd share my results.

Good info. I'm not interested in a debate either.

FWIW, I don't ride trails that would require a 6" travel fork, nor could I even stand over such a bike if it had 29" wheels.

What I like about this forum, is hearing advice from real world users.

Someday, maybe I'll get to ride a 27.5 tandem and have a real comparison. In the meantime, I'll live vicariously through those who have.

I do agree about unweighting the front end of the bike and I know it flat out works better with the 29" wheel vs. 26" wheel. I have no real world experience with the 27.5 on a tandem.

 

[Hurricane Jeff]

ds2199, neither do I have the experience riding a 27.5" or 29er tandem. All my tests have been done on single bikes, in which I own at least one bike of all 3 sizes.
I have found the 27.5" bike to be better is just about any situation.
My Ventana El Testigo has sliding rear dropouts, which can accommodate a 27.5" wheel, I would still need a fork that would work on that size to make it work, which I hope to do soon.

 

[ebnelson]

I was looking for advice on which wheel size I should go with.
I will be doing marathon races on it.

Front suspension or full suspension? In my opinion the 29er is best for both, but for a hardtail the 29er even more so. We have been using the Ergon CF-3 on the road bike to smooth out the stokers ride. I used to use this seatpost on my hardtail single and loved it. Our marathon racing tandem would be a 29er HT with CF-3 seat post and some sort of high range 2x10 or 11 gearing. Our ECDM FS 29er is built up and reliable at 42lbs. It could be a couple pounds lighter with the right parts. A carbon HT could easily loose 5lbs over the aluminum FS.

 

[PMK]

There are a bunch of various factors and really it does just depend.

The biggest factor is the terrain and local riding. These are where the decisions are made, but what works for one on the West Coast, may fail on the East Coast, yet be better in those Colorado mountains.

Also, the riders themselves have a lot to do with it.

Really it does just depend.

PK

 

[mactweek]

I'd like to see a tandem that could take 29 x 3" knards or maybe the upcoming wtb 27.5 x2.75 tires that are coming soon. I love the rollover on these fatter tires and more rubber on the ground is a good thing. You could also run a bit less tire pressure which gives a hardtail a better ride.

 

[TandemNut]

I think the thing most folks don't take into account in the newest, best-ever, end-all wheel size of the month is that the relative weight and wheelbase of a tandem is roughly 1.5 or more times that of a single. Both factors, from a physics standpoint, would favor bigger wheels.
We've ridden 27.5" and 29" ECDM's back-to-back on the same trail, and the 29'er is smoother, and seemed faster, or it seemed that we weren't working as hard. We will do the same experiment on a more technical trail, which might favor the 27.5.
In most real-world settings, I believe bigger is better, provide the geometry is designed around the challenges associated with the respective wheel size.
And yeah, I've been thinking about a Fandango version that would run the Knards and other 29x3.0 tires. That would be cool!

 

[rockman]

Resurrecting this old thread. I'm giving up the ghost on my old 26" Santana Rio and I'm curious now 6 years later if this thread is still relevant wrt wheel size.

Having had a El Saltamontes and El Ciclon a decade or so ago, I'm thinking about a Ventana ECDM. I still ride a 27.5 Turner RFX but love my 29r Evil Offering. I get the point in this thread about rollover with the bigger wheels but maybe 27.5+ might be more maneuverable on techy trails. Can you run both wheelsets on a ECDM with a 29" fork? Any feedback appreciated.

 

[ebnelson]

Resurrecting this old thread. I'm giving up the ghost on my old 26" Santana Rio and I'm curious now 6 years later if this thread is still relevant wrt wheel size.

Having had a El Saltamontes and El Ciclon a decade or so ago, I'm thinking about a Ventana ECDM. I still ride a 27.5 Turner RFX but love my 29r Evil Offering. I get the point in this thread about rollover with the bigger wheels but maybe 27.5+ might be more maneuverable on techy trails. Can you run both wheelsets on a ECDM with a 29" fork? Any feedback appreciated.

The bike can fit 27.5”x2.8“ and up to 29”x2.6“. The 29 option gives a bit more pedal clearance and the 27.5” option has a bit lower center of gravity for stability. We use 29”x2.6” for clearance, but it comes down to where you will be riding and also what standover height works for your team.

 

[rockman]

The bike can fit 27.5”x2.8“ and up to 29”x2.6“. The 29 option gives a bit more pedal clearance and the 27.5” option has a bit lower center of gravity for stability. We use 29”x2.6” for clearance, but it comes down to where you will be riding and also what standover height works for your team.

Thanks for the reply! Maybe I'll stick with the idea of having two wheelsets then especially if there is no difference in frame geometry with regard to wheel size. And perhaps over-fork it with a 150 for ramming over obstacles. Trails are rocky in my neck of the woods. Lots to ponder on a 70" wheelbase bike.