# 69er-ing a tandem...am I crazy?



## tamjam (Jan 23, 2004)

I am going to be buying a 1996 Otis Guy beam MTB tandem from a buddy. Back in the day when it was made for him, it came with a non susp corrected rigid fork 390mm a-c and JP Morgen hydraulic flex stem. I will get those parts with the purchase. Several years ago he put on a Marzochi Bomber DH double crown fork instead which I just don't think suits the bike well, and it has jacked up the front quite a bit. 

Since I have been fully converted to 29ers for the past 3 years, I am not that excited about riding a 26er again, even in tandem form. So that got me to thinking I could put a non susp corrected 29er fork & burly wheel on the front and 69er it. I have been talking to Walt about the fork, and he says he could do a fork with 420mm a-c, and he thinks it's a cool idea. 

So I'd be adding ~1" which I know on a single bike will slacken it by approx 1 degree, but given the long wheelbase of the tandem, I doubt it will really make much difference. Anyhow we'd add about 10mm worth of rake to the fork as an attempt to offset the higher front. Of course the BB be slightly higher, but that's ok.

Cut to the chase already I know...this is my first tandem. I am just wondering if I am missing anything here. I know 29er tandems exist, so it's not like the concept is completely bunk. A 29er wheel can be built up plenty strong to stand up to the added stress/abuse a tandem will put on it, it's only me & my son afterall, so we're not talking 400lbs worth of riders...and I have no doubt Walt's fork can take it. 

My goal is to smooth out the ride of the front with the larger wheel, and not have to deal with the added weight and complexity of a huge DH fork that I have no idea how to tune. Also I expect this will see a bit of pavement time in addition to dirt, which a rigid fork would be better suited for. 

Just let me know if I'm crazy or missing anything....


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## banks (Feb 2, 2004)

do it.


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## mikesee (Aug 25, 2003)

banks said:


> do it.


For a change, Banks-a-rama flipped the coin and got the right answer.

I concur completely--do it.

MC


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## 1spd1way (Jun 30, 2006)

*Do it*

I took my Cannondale mtn tandem and put 700c tires and wheels on it for the road. Same fork. Wheels fit front and rear. (I know it has become a road tandem...) We (bike shop guys and I) put the front wheel on first to see how it would look as a 96er. To be honest, we could hardly tell the difference. Didn't ride it, just wanted to see. Should have taken some measurements.
Let us know how you like it.
Mikesee, how close to Leadville are you? My son (Eastcoaster) is going to Colorado MTn College and I am shipping out a bike. Spec. Big hit or Carver 96er?


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## sparrow (Dec 30, 2003)

See about using a 20mm through axle and setting the thing up for a big 203mm hydraulic disc, like a Magura Gustav DH or an Avid Code, etc. All the braking is up front on tandems. Make it meaty for better control, eh? 

Or just slip a dirtjump fork on there (most of the Marzocchi DJ series, Rock Shox Argyle, etc) and stick with a 20mm through axle 26" wheel. Probably the same costs as a custom rigid 29er fork.

The 1" (or even more) lift won't bug ya with either option. It's like driving a truck anyway.


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## sparrow (Dec 30, 2003)

Oh, and dig around here:

http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/

about QRs and discs on tandems. Applies to half bikes as well, but a 20mm through axle makes any question of QRs and discs a mute point.


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## tamjam (Jan 23, 2004)

sparrow said:


> See about using a 20mm through axle and setting the thing up for a big 203mm hydraulic disc, like a Magura Gustav DH or an Avid Code, etc. All the braking is up front on tandems. Make it meaty for better control, eh?
> 
> Or just slip a dirtjump fork on there (most of the Marzocchi DJ series, Rock Shox Argyle, etc) and stick with a 20mm through axle 26" wheel. Probably the same costs as a custom rigid 29er fork.
> 
> The 1" (or even more) lift won't bug ya with either option. It's like driving a truck anyway.


Right now it is set up with a Marzocchi Mr. T QR20 DH fork...with like 130mm travel...it is a serious fork. So it's got the 20mm axle thing going already, and I was going to have the 29er rigid fork done that way too (Walt's done a few that way already). The front brake is a Hope 04 4-piston hydro with a 180mm rotor, which will get moved over to the rigid fork.

Maybe I should figure out how to tune the fork so I can firm it up a bit, and see how it all feels. But in the end I love the feel of a rigid 29er fork on the type of trails this bike will be ridden on, and I think the way it is set up now is overkill. But then again, this is the opinion of a guy who has zero tandem riding experience.


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## tamjam (Jan 23, 2004)

sparrow said:


> Oh, and dig around here:
> 
> http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/
> 
> about QRs and discs on tandems. Applies to half bikes as well, but a 20mm through axle makes any question of QRs and discs a mute point.


Been there done that...Salsa Flip-off skewer...Avid BB7 disc...rigid fork with no lawyer tabs...me flat on my face on the dirt...wife freaking out...me getting scrubbed and sewn up an hour later at Marin General. Pics of my face all stitched up are on my old PC whose hard drive froze so they're gone. I've learned my lesson already, and will stick with the 20mm TA on the front of this tandem. Thanks for the reminder. :thumbsup:


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## sparrow (Dec 30, 2003)

I'd never had a disc-wheel ejection with normal QRs and no lawyer tabs, but I've seen some loose and crooked wheels on mine and other folks' bikes on rides, or shorty after a ride, maybe on the verge of ejection? maybe not... but better safe than sorry. I bet it won't be long before XC race forks have carbon or ti, or super duper Air-Met 20mm through axles or some sorta similar fool proof system (but then they will make a better fool....).

That MR T does sound like a raked out overkill fork for the bike. And that HOPE should be plenty of brake. Tandems have really good braking, crazy almost, on the front wheel if you've got the traction.


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## twobytandem (Oct 18, 2006)

*29er Tandem...absolutely!*

We've had a 26" mtn tandem for some time and it's truly the most fun off-road if you are both into it and willing to cooperate. We run a Pike w/20mm and have to agree that's the only way to go just for the greatest strength and stiffness.

Now...I keep toying with the idea of building up a Viscious Cycles Jeepster w/the suspended rear end...but how in the world to get my lovely wife to see just how *cool* it would be.

I'll let you all know when I figure that quandary out... 

My favorite idea though is to have Davinci Designs build a one-off 29er tandem w/their independent pedalling system on it, truly the way to go for a tandem. With the much smaller diameter of the "rear cogs as front chainrings" you'd have HUGE clearance under the beast!


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## aosty (Jan 7, 2004)

Crazy?

We tried but couldn't find someone at SO to loan us a 29er front end......


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## Bells Brewery MTB (Dec 27, 2005)

*Been done and raced*



mikesee said:


> For a change, Banks-a-rama flipped the coin and got the right answer.
> 
> I concur completely--do it.
> 
> MC


http://www.printroom.com/ViewFoundP...up_id=59&stype=0&sword=028&tcount=33&scount=5

Eppens from Iowa raced their Crackondale tandem with a 29er front end rigid at this year Ore to Shore....

www.oretoshore.com


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## grawbass (Aug 23, 2004)

tamjam said:


> So I'd be adding ~1" which I know on a single bike will slacken it by approx 1 degree, but given the long wheelbase of the tandem, I doubt it will really make much difference. Anyhow we'd add about 10mm worth of rake to the fork as an attempt to offset the higher front. Of course the BB be slightly higher, but that's ok.
> 
> A 29er wheel can be built up plenty strong to stand up to the added stress/abuse a tandem will put on it, it's only me & my son afterall, so we're not talking 400lbs worth of riders...and I have no doubt Walt's fork can take it.
> 
> ....


I've also been thinking of trying this with my 26" tandem. The angles with slacken much less than a single bike.

One thing you need to keep in mind about a tandem is the stresses that they apply to wheels is much different than on a single bike. 300 lbs of total rider weight on a tandem will stress the wheels much more than a 300 lbs rider on a single. One reason is you simply cannot lift the front wheel to go over logs and whatnot. The wheels are also stressed more in turns.

Personally I would not run a front disc wheel on a tandem even in 26"


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## grawbass (Aug 23, 2004)

sparrow said:


> All the braking is up front on tandems.


Sorry, but this is not correct. Actually tandems have a more even front/rear braking distribution than singles. If anything, all the braking is up front on a single.


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## grawbass (Aug 23, 2004)

twobytandem said:


> My favorite idea though is to have Davinci Designs build a one-off 29er tandem w/their independent pedalling system on it, truly the way to go for a tandem. With the much smaller diameter of the "rear cogs as front chainrings" you'd have HUGE clearance under the beast!


That system is the whip. Would make for much less complaining from the stoker.


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## Soupboy (Jan 13, 2004)

get ur did


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## sparrow (Dec 30, 2003)

grawbass said:


> Sorry, but this is not correct. Actually tandems have a more even front/rear braking distribution than singles. If anything, all the braking is up front on a single.


Having loads of single track tandem riding under my belt, a tandem's front brake is far stronger than a single's front brake. Didn't say anything about front/rear bias, just that the front brake is very very strong on a tandem. You can haul a tandem to a stop with a good powerful front disc brake (when you have good traction). As with any bike, the front brake is critical. On a tandem, maybe more so than on a single. All that extra weight a tandem has, coupled with the long wheelbase that helps prevent an endo, well, if you've experienced it...


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## sparrow (Dec 30, 2003)

*Tried one?*



grawbass said:


> That system is the whip. Would make for much less complaining from the stoker.


The independant stoker pedals is a bad deal on tight and obstacle strewn singletrack. The stoker hits far more stufff, as they can't see what's coming. More rugged the trail, the less value their system has. On wider trails, fire roads and road riding, it is pretty slick.


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## grawbass (Aug 23, 2004)

sparrow said:


> Having loads of single track tandem riding under my belt, a tandem's front brake is far stronger than a single's front brake. Didn't say anything about front/rear bias, just that the front brake is very very strong on a tandem. You can haul a tandem to a stop with a good powerful front disc brake (when you have good traction). As with any bike, the front brake is critical. On a tandem, maybe more so than on a single. All that extra weight a tandem has, coupled with the long wheelbase that helps prevent an endo, well, if you've experienced it...


Ok, my bad. I guess I misunderstood you because you said "all the braking is up front on tandems" which sounded like front/rear bias thing.


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## grawbass (Aug 23, 2004)

sparrow said:


> The independant stoker pedals is a bad deal on tight and obstacle strewn singletrack. The stoker hits far more stufff, as they can't see what's coming. More rugged the trail, the less value their system has. On wider trails, fire roads and road riding, it is pretty slick.


No I haven't tried one, but I'd like to some day. I was thinking smoother roads and whatnot, although it seems like the stoker would have time to adjust their cranks after feeling the front wheel hit something, regardless of whether they saw it. I don't know though, I've never stoked. I guess a large rock that just missed the front wheel might cause problems though.


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## sparrow (Dec 30, 2003)

Grawbass, yeah, just the REALLY tricky skinny trails where the stoker wacks things.

But, to the OP, 96er that thing, but then we gots to move this thread to the "other" forum that no one looks at!


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## twobytandem (Oct 18, 2006)

*Tandem wheels*

We run our 26" tandem with a Phil front and Davinci V22 rim with the 20mm Maxle setup. No complaints at all about stiffness and/or toughness and we've whacked quite a few obstacles head-on that have stopped the tandem cold, even twisted the handlebars a bit w/out warping the front. Oh, we run an Avid 203mm disc so dish is a given for that. Properly built and tensioned wheels are a must, do not skimp on components or expertise when it comes to tandem forces.

Now, that all being said, I just don't know what the dynamics of the 29er front would do to the overall "toughness" of the wheel. Maybe someone with experience in these matters or practical knowledge can help out.

However...no waaaaay would I think of running a 29er or even 69er tandem w/out the 203mm option up front at least. Tandem-dynamics and a fearless team = ludicrous speed most of the time when the trail points downwards  Ask my trusty stoker...she's NUTS!


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