DubT

I had been looking for a longer 30/35 degree stoker stem and found what I was looking for at two different places. I found them here: https://www.sjscycles.co.uk/ram-1-1-8.../?currency=usd, they have them in 150/165 and 180 lengths.

I bought a 180 X 35 degree one from this place: https://webcyclery.com/product/trialt...-stem-1969.htm, this shop is in the US.

I installed the stem and the carbon Profile bars and ended up with a weight reduction.

Here are the numbers. Alloy bullhorn stoker bars: 410 grams, Carbon Fiber Profile bullhorn bars: 216 grams. Ritchey 120mm 30 degree stem 160 grams, new Trial Tech stem 35 degree X 180 long 243 grams.

Total weight of the original = 570 grams, Total weight of the new = 459 for a reduction of 111 grams.

Weight reduction was just a bonus. Stoker is happier with the change. She was experiencing a little pressure in her soft tissue area and this change reduced that pressure.

I checked the weight of an adjustable stem and it weighs 370 grams, so I opted for the lighter Trial Tech stem.

colotandem

Agree. The Trials stems can work out well for a stoker stem. It is a great sollution when the captain is ummm... vertically challenged, because the low rise stems off of the back of a short captain's seatpost just leave the stoker handlebars too low and away for at least my stoker.

We have used a similar set up on our mountain tandem with an Echo trials stem.

I had a conversation with Andy from AM Pierce Cycles https://www.ampeircecycles.com/ when I was at NAHBS about custom stoker stems. He did some nice work on the tandem at the show https://www.ampeircecycles.com/galleries/tandems/ So I got to talking to him about mtb tandems and his well crafted stoker stem. He is open to doing custom stoker stems in ti or steel. He understands that there may be some demand for it. Obviously the ti would be $$$. But the steel ones might approach the cost of the trials stems (maybe, we did not talk $$). But the good part is that you would have options for different rise and lengths.

When we get our new tandem, I'll likely start off with an adjustable stem and get things dialed in. From there, we'll likely either do a custom stem or if we can find the right length in the trials stem, that could be an option as well.

Bottom line is that there is not a lot of options in the custom stoker stem world. I don't know if Bob Davis is still in the business, but carbon can be $$ as well. I did find one other place on the web and I'll have to dig it up and share. Not trying to derail this thread. But options in the stoker stem world (as many of us that have searched) are limited. If you have a tall captain, you can get away with a 130mm or 140mm straight or small rise stem, but it just does not work for us short guys...

FWIW, Webcyclery seems to have the best selection of trials stems here in the states. There are quite a few out of the UK, but with the GBP to USD conversion and shipping, it can be cost probitive. So finding something in the US is higher on my list.

zonatandem

Bob Davis can be contacted at BobDavis@coxnet.com
We have the first (2003) custom adjustable c/f stoker stems with 34,000+ miles on it.
BTW we requested/got a custom Ti glue-on for our mini garage door opener . . . neat and handy!
Bob is semi-retired but still busy doing tandem stuff.

twocicle

We have been using a fixed length 140mm/17degree stoker stem attached to my straight Thomson Elite captain's seatpost, but I have been dying to use the Thomson setback version in order to move the seat rail clamps further back on my saddle. The problem has been that bend in the setback post would interfer with our current stem clamp.

I went pursuing the option of using a 165mm/35degree/240gm stoker stem, that would move the seatpost clamp 5.5cm down the seatpost below the setback bend and all would be good. I posted a link and geometry diagram here.

Then, while riding the trainer last night I had something of an epiphany... why not mount a stem to the bent portion of the seatpost? Sure enough, using a 130gm 130mm/17degree stem attached about 1cm from the very top of the seatpost yields near identical reach at the same bar height, in spite of the -10degree slant remaining.

Wow, I almost made a 110gm faux pas there! LOL.

PS: Tongue in cheek humor intended. This talk is sort of like math jokes

budhaslug

Did you actually mount the stem to the bent portion? I have one of those posts on a different bike, and thinking about the straight geometric angle of the bend make me wonder if the stem and shim will actually make it around the bend. I wonder if you would have to open up the stem clamp in much the same way that I've occasionally had to stretch open an old quill stem to get road bars in and out.

twocicle

Yes I did mount a stem on the bent (upper) portion of the 27.2mm post. It worked out fine. The shim was a tighter fit over the bend than the 28.9mm (1.125") stem clamp, but neither was a problem and I did not need to expand the stem clamp at all. It was very easy. If you have a very long shim it may need some gapping, but in my case it is trimmed to 40mm - the same as the stem stack height.

BTW, for figuring out stem angles on the bent Thomson setback posts, they have a -10 degree angle in the upper portion. Adding that to your seattube angle (typically -17 for a 73 degree seattube) you would end up with -27 degrees. A 17 degree stem nets a -10 degree drop (sag). For our desired stoker bar height, I could not use a 30 degree stem as that is near horizontal and would again want to connect at the bend point.

The end result with the Thomson setback post is very simple and clean. We now have two lightweight Ritchey WCS 4-Axis stems: 1 - 120mm/-6degree for captain, and 1 - 130mm/+17degree for stoker. It actually trimmed a few grams in the process.

If a stoker has a lot of upper strength or puts a lot of weight on the bars, I would suggest sticking with the other option of using a long 35 degree trials stem mounted more at the base of the captain's seatpost. The trials stems are built to take a real pounding and the low mount point puts a lot less torque stress on the seatpost.

My stoker is 95lbs and punches with her thumbs tucked into her palms. If she jabs me, I ask her to do it again a little higher and to the right

Ritterview

I've been Googling stems, and under "180 mm stems" I found this from a site in Spain.

INPULSE "R" 180MM 35º STEM



The weight of 160 grams doesn't appear too likely, and they are now out of stock. There are other hi-rise, over-length stems, however.

Including this 170 mm carbon fiber stem.

waynesulak

So your stoker stem slopes downward 10 degrees. Wow and we have to get the stoker stem as high up as possible. I guess that is because my stoker weighs in only about 30 lbs less than me and has a pair of dumb bells under the bed that get a lot of use. Lets just say she really likes to wear sleeveless jerseys and always played 1st base in co-oed softball games.

Once climbing a local wall she was pulling on her bars and the stem rotated 80 degrees or so on my seatpost. That was interesting as I barely kept us up with her leaning over one way an me standing and leaning forward and over the opposite way. When I finally tried to sit I hit her bars.

We will stick with the trials stem and aluminum seatposts that can stand some clamping force.

twocicle

The Inpulse 180mm can be had here: https://www.trialsaddict.com/stems/20...0x35-stem.html
and is listed as 230gm., or directly from Inpulse here: https://shop.inpulsebikes.com/index.p...gory&id_lang=1


As for the Monty, good weight but the description says:
MATERIALS
Made of aluminum 6061 T6

maybe it's Faux Carbon?

twocicle

A Deda 20 degree would work ok, dropping -7 degrees, and mounting at the mid-point of the -10 degree area, but I am partial to Ritchey WCS stuff and in fixed stems they only have 17 and 30 degree in the higher sloped stems. There is always the adjustable Ritchey stem, but it's a tad heavier. Going the route of attaching high on the captain's post is definitely not compatible for everyone.

My simple theory regarding the key to a good stoker is to require an average power output value equal to weight in lbs. We don't race and she ain't no animal.

Hey, good topic to start a new thread... "Funny stories about stokers screwing up bars and seatposts".

waynesulak

Unfortunately power to weight ratio is not perfectly scalable.

Since we like most teams are a couple, power to weight is way down the list of my desired stoker attributes.

Ritterview

According to this site, it is...

I.D.31.8mm. Color black imitation carbon fiber.

twocicle

Hey, it's great to be imitated. But really?!

Imitation carbon fiber bikes are next?

Chris_W

We recently bought a 165mm, 35 degree stem from SJS Cycles in the UK. It put the bars in an almost identical position as we had with the adjustable stem, but with a decent weight saving.

zonatandem

Have seen an incredible paint job on a daVinci tandem that looked like carbon fiber at an Interbike expo years ago . . . great paint skills!

Ritterview

I am thinking of getting that 35 degree 180 mm seatpost to replace my stoker's adjustable seatpost, and save maybe 30 grams.

She has hers set at 215 mm (but its not like there was a fitting process). I set it back to 200 mm. I'll see if she notices. I'll bet she does, and there isn't any way she'd tolerate 180 mm.

I don't know the angle of the Calfee seatpost. I measured it on an iPhone app (SetSquare), and it came to 30 degrees.

DubT

This site shows it to weigh 232 grams, which is close to what the one that I bought weighs (243).

https://www.trialsaddict.com/stems/20...0x35-stem.html

twocicle

I suggest playing with this stem comparison tool: https://yojimg.net/bike/web_tools/stem.php. Unlike normal single/captain stem positions and 73 degree steerers (90 - 17), a stoker stem is backward facing so one must use a steerer angle of 107 (90 + 17) to get the proper results for a stoker setup.

Based on a 200mm 30 degree stem (ie: close to your proposed Calfee stem setup), a 180mm 35 degree stem would be 27mm less reach when the height is adjusted with -11mm spacers to equal your Calfee stem height (IRL the -11mm spacers means lowering the stem on the seatpost by that amount).



I can't see any way for you to get anything near the reach needed for your stoker other than by using an adjustable stem.

Chris_W

Here's another tool to help you figure out how length and angle combine to determine reach of a stem. When I went through this process, measuring the stoker's current stem and seat tube angle with an iPod Touch App, I had to get out some paper to figure out how all of the angles combined. As twocicle said, it's all backwards compared to how it would be if the stem was facing forwards on a fork steerer.

twocicle

The problem with simple charts is that they do not factor the adjusted reach value depending on where you mount the stem. ie: as you move a stem down it moves the bars away from you, and moving the stem up brings the bars closer. This is true for normal mounting on steerer tubes and for stoker stems mounted on captain's seatposts.

Using Ritterview's comparison above, the two stems have a 11mm bar height difference which necessitates moving the 35 degree stem down -11mm to give it the same bar height as the 200mm stem. At that adjusted mount point, the reach difference between stems is 27mm. However if you did not adjust the mount height (as most charts do) the reach difference would only show as 23mm which is incorrect.

Ritterview

I put the bar in to 200 mm, and we rode it today, and my Mrs. R didn't notice, and when informed, didn't mind. At 5'10" on a L/M frame, her position has been quite upright. I notice on her half-bike and when she adjusts the bike at spin that she isn't as upright. So, I theorize she might do okay with the handlebar forward and lower (which would be at least a little aero). Yeah, we should get a fitting, but I don't think that's not likely to happen.

I looked to purchase the InPulse stem at Trials Addict in the UK, and with $15 shipping it and tax(?) came to $70. That gave me pause. The price looked lower at InPulse, but it did not look to have a U.S. shipping capacity. I emailed InPulse, to tell them about the stoker market they are missing out on. Maybe a tandem retailer in the U.S. can stock it.

DubT

WebCyclery has the Trialtech in stock for $55 and is located in Bend Oregon.

Almost the same weight as the one you are looking at.

https://webcyclery.com/product/trialt...-stem-1969.htm

This is where I ordered ours.

Wayne

twocicle

Ritterview, it is interesting your 5' 10" stoker uses such a long (+20cm) stem setup while the stoker bar height in your pics appears to be identical to ours. I am curious what the stoker reach is from saddle tip to center of bars @ stem?

I should have refreshed my brain with the Calfee geometry chart. I forgot that while Calfee's headtube angle is identical for all models, the seatube angles vary depending on size. Duh on my part. Our captain's seatube is 74 degrees whereas Ritters is 73 degrees.

My 5' 2" stoker uses every bit of the reach available to her and is 100% stuck on using drop bars for the extra positions they offer. We have her saddle position and bar height (-1 cm) identical to her road bike which was setup by Andy Pruitt & clan in Boulder. The reach on her single is 48cm, but on the tandem the maximum we can feasibly use is only 44.6cm (our current stoker stem is a 140mm 17degree attached to a straight seatpost) afterwhich the bars tuck too close under my saddle. The tandem reach limitation has a benefit of helping to adjust her torso a little more upright so her head doesn't hit my jersey pockets, so we did not bother altering anything else to compensate for the closer reach. I believe Mark Livingood (TandemGeek) has a custom long stoker tube to address this typical reach issue.

DubT

One thing that has to be taken into consideration when you look at Ritterview's bike and also our bike is that we both use the Profile carbon bull horn bars rather than drop or the more common aluminum bullhorn bars. The Profile carbon bars have a pronounced drop from the center, the ends are over an inch lower than the center of the bar where they mount to the stem. When we had our fit a few months back we had the profile carbon bars and the fitter determined that my wife was reaching too far forward and down to reach the bars. We then installed a pair of aluminum profile bars that raised her up but she was still reaching a bit further than he recommended. Thus the new stem which actually places her a little more upright and further back than was actually recommended, but she was having some soft tissue issues and the new position has eliminated that aggravation. Comfort trumps power!

The more upright position allows stokers to see more than the back of the captains backside and allows them to do a little more sightseeing.

As noted I also observed that Mrs Ritterview was sitting a bit more upright than some other stokers. The important thing about stoker position is that they have to be comfortable and must be in a position where they enjoy the ride. If the position is not the same as their single bike but they are happy then that is the important thing.

My stoker does not ride a single bike which makes life simpler for me.
Wayne

twocicle

For sure it's the stoker's choice on position.

In our case she wants to disperse some weight to her arms the same as her single, plus she like being able to move from hoods to drops. Last year we started using semi-compact drops (Ritchey WCS Evo Curve) that are not as deep as the Deda 215 we prevoiusly had. The compact drops are easier on her tight tendons, while she still has the bar tops and hoods at the old height.

From a captain's point of view (mine) there is a big difference in cross-headwinds between when my stoker is on the hoods vs in the drops. When she is up on the hoods in this case, it feels like there is a drag parachute back there... and she is small too! Moving into the drops doesn't completely eliminate the crosswind drag, but it certainly does help and feel less brutal. Plus on winding downhills with tight corners, she knows to get into the drops because it is more stable with the lower center of gravity and it keeps her upper body from leaning the wrong way to any large extent.

There are a lot of times when she is head down in the groove and I have to remind her to sit up and enjoy the view too. The only time I ask her to move lower is in otherwise adverse conditions.