PromptCritical 

I have a Santana tandem with a 31.8mm threadless fork steerer tube. I'd like to raise the handlebars a couple of inches.

Does anyone have a source for a 31.8mm headset extender? (The forks are carbon (including the steerer tube), so it's a no-go on modifying them like I did on a previous tandem).

Cheers, Mike

Duragrouch

Due to carbon steer tube, it's a definite no on an extender that fits inside the carbon tube; It must be clamped outside, and with all normal precautions. Just be aware this will place more moment (torque) on the steer tube than the original setup, in all directions, like forward with weight on handlebars, left and right when climbing out of the saddle, etc. Use caution, get advice, preferrably from carbon fork experts, which is not me.

There are lots of higher stems (including adjustable hinged) that may preclude the need for an extender, but the same cautions apply.

FBinNY 

It's not that a CF steerer couldn't take the load of an internally expanded stem riser ---- as long as it's not overly tightened.

The problem is much simpler. These stem risers are made for steel steerers with 1/16" wall thickness, so 1" for your bike or 3/4" for B a 1" fork. CF forks often have thicker walls, so the IDs won't be right.

Measure your fork's ID, then shop for the adaptor accordingly. And if you find one go easy on tightening it.

Duragrouch

I definitely see your points (good as usual). But if they have a threadless stem, don't they need an extender that clamps on the outside of the steer tube, just to load the headseat properly? Now, with that on the bottom, and then an upper that's 1-1/4"/31.8mm for the stem to grab, don't ask me how they preload the headset, except for just pushing down on the extender and then tightening the clamp.

FBinNY 

Yes, I was half asleep when I posted that, but it could be worked around by a decent tinkerer. OTOH there are some external riser adaptors out there that the OP night consider.

Duragrouch

Reminds me of the following, crazyguyonabike, Bike Friday, original part to preload headset broke, appeared too fragile, he worked with a local mechanic to devise a means of preload and clamp, 3 pics:

https://www.crazyguyonabike.com/doc/...size=large&v=1

https://www.crazyguyonabike.com/doc/...size=large&v=1

https://www.crazyguyonabike.com/doc/...size=large&v=1

bboy314

That’s a tough one. I’ve never seen a 31.8 stem riser, and all the risers I’ve seen caution against using with carbon fiber steerers. I’d be considering a different style of handlebar.

Crankycrank

I couldn't find any 31.8/1 1/4" risers either but this may be useful if you want to try to find a stem with enough angle to raise your bars 2" more. Stem Comparison Tool | yojimg.net Plug in the numbers of your current stem and determine what angle and length stem you need to get the right setup.

PromptCritical 

The supply of 31.8mm stems is very limited and none would work for me (I'm short in the torso). I thought of a couple of ways to modify a stem (cut and weld with an inner sleeve) that would be pretty simple.

Duragrouch's comment has me concerned. I want to raise the bars about 2" (they are currently about 2" forward and 1" above the steerer tube. I weigh 235# and my stoker #135. Is that modification going to add an unacceptable level of torque on the steerer tube?

Should I just bite the bullet and have a steel fork made?

Cheers, Mike

veganbikes

I would get a different fork. I wouldn't use a steerer tube adaptor at all especially not on carbon fiber. There are plenty of forks to be had but I would look at something specific for tandem usage.

Iride01 

Riser bars will get you 1˝" more height on the current stem and steerer tube length. There might be some that go more. I haven't looked in a long time to see what is out there.

PromptCritical 

I think the new fork is the best idea. Carbon kinda scares me. I had a bad experience with a Trek Madone......

Thanks everyone!

bboy314

If you can find an appropriate tandem rated fork “off the shelf” with a 1 1/8” steerer, you can use headtube reducers made by Problem Solvers to make that work with a 1 1/8” headset, and have many more choices of stems to use. I bought such a fork from Co-Motion bikes in Oregon a few years ago when I needed one.

grumpus

It might be easier to use one of these

then you don't have to mess with the stem/steerer interface.

PromptCritical 

Hmmmm, that looks interesting. Any idea where I can get one? I googled the name on the side of it and tried some names and descriptions of it, but didn't find anything

PromptCritical 

Yeah, I'm headed down that path but $$$$ Yikes!

bboy314

Does your bike have rim or disc brakes? When I was in need of a fork, I also contacted House of Tandems in Houston, TX. They had some really nice carbon Woundup forks on sale for a great price - because they were rim brake only (canti studs if I recall). Granted this was a few years ago.

grumpus

Here's one. I don't think there's an actual name for these, and the description just gets them mixed in with stem risers and adjustable stems.

Duragrouch

A good idea, but a couple things to be aware of:
- "There's no such thing as a free lunch" (Heinlein); Whether you raise the handlebars via a riser, or inclined stem, or hinged stem, or that device (known as a handlebar double clamp or double stem), same position equals same moment for the same force.
- The problem I find with double clamps is a) they mount closely on each side of the stem, which is exactly where my aero clip-on bars mount, and b) if mounted further outboard instead, they require handlebars with a very wide area of stem clamp diameter, hard to find, so the double clamp or aero bars would be clamping in the transition area between the center and the sides, so a tapered diameter, which you can't clamp to.
- Some of those double clamps look awful lightweight in structure, hollowed out in the middle, and both brackets will be subjected to not only bending, but torsion when climbing, and for the latter, ideally, the clamps are a "closed section" to be stiff. The one I've seen made by Tern and comes on some of their bikes, looks more stout (even though technically, still not a closed section), and you can adjust the tilt in seconds:

https://www.mybikeshop.com.sg/shop/b...n-andros-stem/

Crankycrank

Why not contact Santana. They know a thing or two about building quality tandems and fitting all types of riders. They can also recommend on whether their fork steerer can handle various stem heights and lengths and may even offer a riser of some sort. Contact Santana - Santana Tandem

Andrew R Stewart 

This! Santana even use to offer a riser adaptor for their customers, I've installed a few when I worked at Allstar in Raleigh. I've also installed one for a second level of handlebar mounted accessories (before Minoura brought out their version for accessories).

Unrelated to the riser designs is that when I see riders wanting so much change in handlebar positioning I think that the basic size/nature of the bike is no longer matching the changing rider's needs well. While bike can and are modded to better fit our aging bodies there can be a point when the changes are no longer keeping up with our needs. I see riders wanting to continue running drop bars (as an example) but need really high and close positioned bars to not be reaching out too far when on the brake lever hoods (and by then likely never use the drops for more than fast straight downhills). Generally I suggest flat bars, with the proper controls to match, as a first consideration. It's too bad that the interchangeability between flat and drop bar levers,brake/shift controls, has become so little with the "demands" of more integration and brand/series specific specs design direction we're going in. This makes keeping older bikes up to date with their rider's changing needs harder to do. Andy

grumpus

The one I linked to above doesn't seem to have those problems - it's offset so shouldn't take much more space than a regular stem, and although hollow it's forged, not milled from solid. It wasn't easy to find among all the cheap Chinese stuff.

PromptCritical 

Yes, this is exactly my situation. I'm not as flexible as I once was and the original cockpit causes next pain and triggers my carpal tunnel. I've called Santana and they aren't interested in any kind of modifications, which given the number of lawyers in California, I can understand.

I'm going to break open the wallet and buy a new fork.

Thanks for everyone's advice.

Cheers, Mike

t2p

supply of 31.8 stems is limited ???

I don’t agree with or understand this statement

how high do you need to go ? more than the two stems pictured above ?

bboy314

31.8 is the steerer dimension for this particular bike, not (necessarily) the handlebar clamp.