# 29-26" Trex T900



## Bimmer74 (Jun 9, 2013)

Hi all,

I have a used Trek T900. My 8-year-old daughter and I ride it on the local gravel and paved bike-paths. 

I'm interested in 29" wheels for a smoother ride, and I'd prefer big hydraulic disc brakes to the rim brakes. 

A 29" wheel/tire is impossible in the rear, obviously, and I'm not ambitous enough to add a disc in the rear, either.

On the other hand, it occurs to me that I could easily replace the front fork with a disc brake-ready rigid 29" fork. Then I'd just need a wheel/tire and a front brake. 

I understand that it would slightly change the geometry, but that seems insignificant. 

Thoughts?!


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## geronimo2000 (Jan 12, 2014)

1) do you really think that 29" wheels will give you what you want? have you experimented with tire options to see what you can do without modifying the bike?
2) are you certain that you can't fit a 29" wheel in the rear? Most hard tail MTB-style bikes sold with 26" wheels will take 700c/29" rims with enough fiddling - but with reduced clearance your tire options get slim
3) if you're only going to have one disc do you really want it in the front? even with a heavy steel fork you'd stress that frame in ways it wasn't meant for
4) why spend hundreds of dollars on a new fork and disc and front rim only to end up with a franken-bike that you'll have to put back to original before you can sell it? wouldn't you be better off monitoring craigslist for something that gives you what you really want and putting your money there?


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## Bimmer74 (Jun 9, 2013)

Good questions, Geronimo...

1. I'm not sure. I do know that if I'm changing out the fork to upgrade the brakes or to change the wheel size, then I'd might as well do both. 

Right now the bike has Serfas City Drifter tires on it, and they're fine on pavement but hopeless on gravel. I haven't tried any other tires, but would put 26" MTB tires on it, eventually. 


2. No way. There's only about 3/4" of clearance at the narrowest point. 


3. Yes, in the front. That's where most of the braking is power is. The rear is REALLY light with only my 80# daughter back there, and we spin the rear tire on gravel and easily lock it up braking. 

Once nice thing about the tandem: it's super stable, even hard on the front brake. 


4. I had figured $50-70 for the fork, $75ish for a complete brake set-up, and $100ish for a new wheel... I guess that's $250ish, total. I won't do this lightly.

Anyway, that's a helluva lot cheaper than buying a different tandem bike... the decent ones start at $1,300 or so. 

Craigslist is a non-starter, because I live in the middle of nowhere.


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## geronimo2000 (Jan 12, 2014)

so, with your kid on the back, you are going to trust a $50 fork? at least get one that is tandem rated so that you can sue the manufacturer when it fails. it's hard to do an endo on a tandem, but the way to do it is to have your bike be light in the rear and then put all your braking power up front. 

I've used the Serfas drifter tires on a tandem and found them okay off pavement but changing the width and the tire pressure will make a big difference in how it rides and handles. I'm skeptical that you're going to get a smoother ride with a bigger wheel - it isn't going to be smooth on gravel no matter what wheel you run and to get smooth on pavement you'll get the best results with a narrow hard tire. You might want to ride it for a season or two with a variety of cross/knobby tires and see if you're really into riding tandem. One way or another you're looking at compromises and you just have to be careful that you don't head down a path that ends up with you spending a bunch of money without getting you what you want.


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## Bimmer74 (Jun 9, 2013)

geronimo2000 said:


> so, with your kid on the back, you are going to trust a $50 fork? at least get one that is tandem rated so that you can sue the manufacturer when it fails...


A steel Surly or Kona fork designed for MTB should be pretty bomb-proof, right? They're under $70...



geronimo2000 said:


> You might want to ride it for a season or two with a variety of cross/knobby tires and see if you're really into riding tandem...


Oh, don't worry, we're into it. We've had the bike for several months, and we love it.

My daughter scoffs at her "half-bike" now...


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## geronimo2000 (Jan 12, 2014)

Safety Recall


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## Bimmer74 (Jun 9, 2013)

Oh, $hit. Thanks for pointing that out! 

I wouldn't buy a Surly fork, anyway, because I want post-mount brakes, but this is a good heads up...


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## geronimo2000 (Jan 12, 2014)

on their website FAQs Surly says:

"Which Surly fork is rated for tandem use?
The Instigator: http://surlybikes.com/parts/instigator_fork/ That is all."

Since that is a 26" fork you likely don't want it. I don't see where Kona gives specs or limitations on its Project2 but personally I wouldn't put it on my tandem without having them tell me that they would stand behind it for that use.

Even with a lightweight stoker you likely have 250-300 pounds including the bike and you can accelerate to 40-45 mph really easily. You definitely don't want to take a shortcut on your fork because if that fails it can be catastrophic.

Does your frame have a thread less headset? If you have look for a threaded, tandem rated fork that's going to limit your options and upgrading to a new headset is a few more $$$


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## moabjason (Apr 26, 2010)

*29er front*

I have a gt quatrofoil, we put a surly instigator fork with bb7 disk brakes, I was able to get a 3.0 knard tire






on a 29er rabbit hole rim. With that combo on that bike I have no toe rub. It rides a little high but I don't care.


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## Bimmer74 (Jun 9, 2013)

Surly, re: the Instigator fork: 

"Tandem and dirt jump rated.... One or the other, of course. Not meant for dirt jumping on tandems."


LOL... 

Anyway, looking at MoabJason's, a 29er would fit easily...


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## Trails4Two (May 12, 2008)

*slightly?*



Bimmer74 said:


> Hi all,
> 
> I understand that it would slightly change the geometry, but that seems insignificant.
> 
> Thoughts?!


My two bits: I tried something similar on our Cannondale (26" with 100mm suspension to 29" with 100mm suspension). I am not particularly sensitive to geometry stuff, but I hated the change. It really made the steering floppy, and I didn't trust the handling with my child's well-being at stake. I don't really think a 29" wheel is going to give very much benefit by itself and not enough to risk messing things up.


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## Okayfine (Sep 7, 2010)

What kind of space do you have in your fork for a wider tire? Easiest path is to change the tires to something more suitable for light off-roading, then see how much further you want to take the spending.

I understand the desire to upgrade the braking, but that can also be done with new/different pads, deglazing the rim, new cables, etc. Given the team weight and use, I don't think discs are required. We have a road tandem with rim brakes and are able to back that thing down in a hurry from speed at 360lb team weight.

If you do change the fork, sticking with 26" wheels (and fork to match) would be the way I'd go. A nice big front tire will provide some impact damping all on its own. Might be all you need.


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## moabjason (Apr 26, 2010)

I used a surly instigator fork, it seamed to have enough rake to prevent toe overlap and the height was right. We swapped to disk brakes so that I could use my surly 50 mil wheel with a 3.0 tire off of my fat bike or a standard 29er wheel or any sized wheel and not have to be limited by rim brakes. 
The fork was pretty cheap and I used mechanical disk brakes. We just wanted to upgrade to a modern fork and have some choices for wheels. The 3.0 knard tracks through the dirt and sand awesome and you don't have to worry about the front tire loosing traction during braking.


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## Fleas (Jan 19, 2006)

Surly Instigator fork with 203mm BB7 works fine. When we hauled the trail-a-bike the combined weight was 460#. THAT's a lot of braking stress on that fork. It didn't flex as much as my 490mm rigid steel fork on my 29er did.

However, I didn't use a 29er wheel on the MT1000 - very flip-floppy like Trail4Two said.

-F


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