# Stoker stem questions



## bme107 (Jul 23, 2008)

First off the captain's seat post is 29.4 stock, which isn't a common size now days. If I replace it for something lighter/newer I guess I'd go with 27.2 and use a shim.

I'm wagering that we are going to need a stoker stem with far more adjustment (longer).
1. Is there a more commonly seen seat post clamp size size for modern stoker stems?
2. This is the stem I've got:








Will these "high rise stoker stem inserts" sleeve on to the end of the stem to give us more length?








From https://www.tandemseast.com/parts/stems.html left column 3rd row.
What is the proper name for these type extensions? (google doesn't reveal anything other than that one site)


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## Plum (Sep 14, 2004)

bme107 said:


> First off the captain's seat post is 29.4 stock, which isn't a common size now days. If I replace it for something lighter/newer I guess I'd go with 27.2 and use a shim.
> 
> I'm wagering that we are going to need a stoker stem with far more adjustment (longer).
> 1. Is there a more commonly seen seat post clamp size size for modern stoker stems?
> ...


I think those extensions are aimed at the telescoping type stems, similar to a control tech.

I'm in the same (exactly) boat you are, oddball sized seatpost with a matching oddball sized stoker stem attachment. My research tells me that there aren't any other 29.4 stoker stems out there, so I've pretty much decided to go the same route, 27.2 seatpost shimmed to fit the 29.4 seat tube, then throw a 28.6 shim on the seatpost up higher to take a more common 28.6 (1 1/8") stoker stem, like the control tech.

I'm running the stock GT setup for now, but the width of the stock clamp makes it difficult (if not impossible) to get anything but a straight or low rise bar in there. I tried to fit a profile bullhorn bar in there and couldn't get it past the first bend, even using the penny trick to open up the stemp clamp further..

I've also been looking on ebay for a 1 1/8" dirt jump stem to swap onto the stock stoker extension in place of the GT one, the stoker extension is 1 1/8", so any normal 1 1/8" ahead stem will fit on there, finding one as short as the stock is not proving to be easy (it's equivalent to about a 30mm stem) but there are tons of 45-50mm ones out there. Swapping one of those in will get me a removable faceplate at least, plus you could get one with some 'rise' that will work to get you some additional reach in a stoker configuration.

Plum


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## bme107 (Jul 23, 2008)

Plum said:


> I'm running the stock GT setup for now, but the width of the stock clamp makes it difficult (if not impossible) to get anything but a straight or low rise bar in there. I tried to fit a profile bullhorn bar in there and couldn't get it past the first bend, even using the penny trick to open up the stem clamp further..
> 
> I've also been looking on ebay for a 1 1/8" dirt jump stem to swap onto the stock stoker extension in place of the GT one, the stoker extension is 1 1/8", so any normal 1 1/8" ahead stem will fit on there, finding one as short as the stock is not proving to be easy (it's equivalent to about a 30mm stem) but there are tons of 45-50mm ones out there. Swapping one of those in will get me a removable faceplate at least, plus you could get one with some 'rise' that will work to get you some additional reach in a stoker configuration.
> 
> Plum


I hadn't even considered the issue with the pinch bolt stem. In the short term, once I get the reach set up properly, I figure I'll add a set of stubby bar ends to the stock straight bar for varied hand positions.

I like your idea with the DJ stem. Would a BMX stem work also? Not sure of their clamping diameters, but trying to expand your search with other ideas.

I know it may look awkward but maybe you could flip the stoker stem (slopes downward from the captain's seat post) and then install a more common 90-100mm mtb stem with a 20-30 degree rise. Mock it up if you've got a spare stem laying around. It's hard to visualize otherwise.


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## Plum (Sep 14, 2004)

bme107 said:


> I hadn't even considered the issue with the pinch bolt stem. In the short term, once I get the reach set up properly, I figure I'll add a set of stubby bar ends to the stock straight bar for varied hand positions.
> 
> I like your idea with the DJ stem. Would a BMX stem work also? Not sure of their clamping diameters, but trying to expand your search with other ideas.
> 
> I know it may look awkward but maybe you could flip the stoker stem (slopes downward from the captain's seat post) and then install a more common 90-100mm mtb stem with a 20-30 degree rise. Mock it up if you've got a spare stem laying around. It's hard to visualize otherwise.


If the BMX stem is a standard 1 1/8" stem, then yes, it should work as well.

You may well be correct, it may be a best fit scenario to flip the stoker extension down, then use a little longer (taller in this case) stem to locate the bars where they need to be.

Our tandem will likely be setup more like a gravel road/road touring cruiser, so a set of bullhorns or even h-bars would be a nice setup for the stoker to have a few positions. A removeable faceplate really opens up the options from a flared drop to a h-bar to a bullhorn, so that's likely the route I try first.

Plus, for around $15, I can try something and see if it works, compared to a control tech or similar stoker setup which will be (at minimum) around $75 or $80.

Plum


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## bme107 (Jul 23, 2008)

bme107 said:


> I know it may look awkward but maybe you could flip the stoker stem (slopes downward from the captain's seat post) and then install a more common 90-100mm mtb stem with a 20-30 degree rise. Mock it up if you've got a spare stem laying around. It's hard to visualize otherwise.





Plum said:


> You may well be correct, it may be a best fit scenario to flip the stoker extension down, then use a little longer (taller in this case) stem to locate the bars where they need to be.


I finally had the chance to mock this up with spare take-off parts.



























It would work if you could find the suitable combination of stem length and angle. Maybe an adjustable angle stem would be the best bet. As you can see the removable faceplate is key as you supposed.

In my case this will not work with the stoker stem pointing downward. In order for the stem to clear the top tube the captain's seat needs to be about 1" higher than is comfortable for me. If you've got longer legs and ride with more extension on the captain's seat post then give it a try. In the test pics I think that there is about 4.5" of seat post showing. With this combination of seat and rail height I only show 3.25-3.5" when properly fitted.

Hope this helps.


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## Plum (Sep 14, 2004)

bme107 said:


> I finally had the chance to mock this up with spare take-off parts.
> 
> 
> 
> ...


Nice work, nice to prove the theory out anyway, even if your parts aren't correct, at least we know it'll work now. A short DJ type stem would probably be better than the 100mm one you have, but if you need additional length, that would be the stumper..

Plum


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## Sam Jones (Feb 25, 2005)

Another option is to use the 2 dogbone extenders than maount to a short section of bar on the original clamp and then give you a 2" off set in any direction from that original bar position. This is very light and very flexible. They are about $40 from Tandems East, etc.


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## bme107 (Jul 23, 2008)

Plum said:


> Nice work, nice to prove the theory out anyway, even if your parts aren't correct, at least we know it'll work now. A short DJ type stem would probably be better than the 100mm one you have, but if you need additional length, that would be the stumper..
> 
> Plum


Seeing it really helps me. I guess other than showing it could work, the only real information this test revealed was that you need to be showing 4.5"+ of seat post to even contemplate the flip.
If you source a DJ stem please take some pictures for me.



Sam Jones said:


> Another option is to use the 2 dogbone extenders than maount to a short section of bar on the original clamp and then give you a 2" off set in any direction from that original bar position. This is very light and very flexible. They are about $40 from Tandems East, etc.


Sam, can you link me a specific page from their site?
I browsed the forks/handlebars, stems and stoker comfort pages of their site and cannot find dogbone extenders. Their search engine reveals nothing or takes me to actual dog bones. I'm trying to formulate a mental picture of your suggestion.


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## Plum (Sep 14, 2004)

bme107 said:


> Seeing it really helps me. I guess other than showing it could work, the only real information this test revealed was that you need to be showing 4.5"+ of seat post to even contemplate the flip.
> If you source a DJ stem please take some pictures for me.


BME, I am looking at something similar to this. Not much change from the stock dimensions, but it gets me the removable faceplate..

I would be running the seatpost-clamped 'stem' extension (the stock unit) in the up position, opposite of the way you had shown. This stem could be flipped around to either move the bars slightly closer or farther from the stoker.

Plum


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## Sam Jones (Feb 25, 2005)

This is a link to the picture of what I call a "dogbone" at precision tandems

https://precisiontandems.com/cat_pics/smasx50.jpg

This is how they list it. I think Tandems East has it for $40? but not sure becasuse I didn't see it on thier new site but you can call them. I have them on all my captains bars to get the height up for my old back :>)

The short tube goes where you current handlbars are mounted and doesn't require a 2 bolt bar attachement (once you get the old bar our :>)

STEM EXTENDERS STEM RISER STEM RAISER 
MOVES HANDLEBAR IN ANY DIRECTION FROM THE ORIGNAL POSITION 
Handlebar Riser -- works with 25.4 bar and Stem 
ASX-50 - 50mm Bridge, Permits a 2" arc of adjustment in any direction $50.00


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## bme107 (Jul 23, 2008)

Thank you both for the pictures and info. Seems there is hope after all at a reasonable price.


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## Plum (Sep 14, 2004)

*Success*

Ok, finally got around to this again, have the 'new' stoker stem ordered and installed, seems to work like I expected.

My wife and I sat on the bike last night, at first blush, the stoker compartment seems awfully short on real estate, pretty cramped. The captains cockpit is shorter as well, but at least there I can go longer with a stem or a drop bar and get some length back, but the stoker is kinda limited by the size of my ass.

The new stem is shown as far back as it goes, and even with the additonal 'rise' (which actually results in 'reach' in this orientation) the bars are still under the rear of the captain's saddle.

Plum


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## bme107 (Jul 23, 2008)

Where did you get the stem and what are the specs?

Yes, the stoker compartment is a bit shorter on this old bike than newer designs. It's one of the reasons I'm running the captain's seat about an inch farther forward than I typically might. My wife is 5'-4" so the 17" stoker position is actually a bit big for her in height, but the length turns out to be OK.

I got a cheap aftermarket handle bar for the stoker that ads about an inch to each side. Previously with the narrow original bars if she raised a thumb she'd goose me. It's tough to find a stoker bar with rise or any type of sweep that won't feel like it's encroaching on the captain. Maybe one of those off-road drop bars that sweeps out as well as down? Then again her chin may be in the small of your back.

Did you have the original integrated seat post clamp cut off and squared up when you were doing the rest of the frame work?


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## Plum (Sep 14, 2004)

The stem is an ebay special, 1 1/8" steerer, 25.4mm bar clamp, under $20 delivered, here's the auction for more:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=370369642640&ssPageName=STRK:MEWNX:IT

The bar clamp width on this stem is pretty wide, so if you have a bar with a narrower 'buldge' in it for the stem clamp, you may run out of real estate, most of the bars in my stash are wide enough, including a h-bar, midge bar and a regular aluminum ritchey force bar.

My wife is around 5'-4" as well, so our bike is tall for her, but the stoker compartment is still on the short side. Our bike is pretty close to road bike sized for each of us, with the exception of the stoker compartment..

We were actually planning on either flared drops or a set of titec h-bars, but I can't see them working with any more forward extension from the clamp area, I think they'd be in my hamstrings with the forward extension.

A setback post with a seatpost shim might be a possibility to add length to the stoker compartment, but we'll give it a shot this way first before we throw more money at it..



bme107 said:


> Where did you get the stem and what are the specs?
> 
> Yes, the stoker compartment is a bit shorter on this old bike than newer designs. It's one of the reasons I'm running the captain's seat about an inch farther forward than I typically might. My wife is 5'-4" so the 17" stoker position is actually a bit big for her in height, but the length turns out to be OK.
> 
> ...


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## Plum (Sep 14, 2004)

bme107 said:


> Did you have the original integrated seat post clamp cut off and squared up when you were doing the rest of the frame work?


Forgot to answer this, the stoker stem extension is as I received it, squared and capped originally as far as I can tell.

Appears to be identical to yours by the photos.

JP


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