Carbonfiberboy 

Thanks to all for the many stoker stem threads and contributions. My 5'2" stoker has been complaining for a long time that her arms tire quickly when I ask her to get low on our medium/small CoMo Speedster. And I've been noticing that we pick up a good bit of speed on the flat when she does. I finally cut ~1.5" off the inside bit of our stock CoMo stoker stem and we both just love the difference. She's much more comfortable in all her positions plus we are noticeably faster. She now has a 3 cm drop with her stem slammed.

We kept her relatively narrow cowhorns, even though her hands rub my thighs if she grips the end of the bar. She just doesn't wrap her hand around and likes it fine that way. Narrower is aero-er.

Now I'm thinking about a fixed stem. How do we measure steeply angled stems? From the center of the captain's seatpost at the top of the stem to the center of the bars? I get 125mm for that measure now.

twocicle

Your measurement of 125mm (12.5cm) sounds quite short. Perhaps post a photo of it and your tape measure on it. Assuming you are using a typical CoMo/ControlTech style adjustable stem, those are 35degrees.

If your stem is indeed only 125mm, then there should be plenty of fixed stem options for you, but it also depends on where you are clamping on the seatpost and what type of seatpost you have as far as options to move the clamp position.

Just off the top (prelim suggestion), Ritchey makes a nice 30 degree stem. A 120mm/30degree stem would be just 2mm longer (closer to stoker) when mounted with the same bar height.

Regarding your stoker's arms getting tired when in low position with cowhorns... that would be due to requiring bent arms, whereas drop bars allow for using skeletal bracing which is not so fatiguing.

DubT

Are you suggesting that one should have their arms straight. That flys in the face of everything that I have ever heard. It is my understanding that you want at least a slight bend in your elbow so that your arms absorb shock and do not send that shock into your shoulders, wrists, elbows, etc. It does take core strength to support your torso so that you do not apply so much pressure to you hands/arms. Bullhorn bars can be adjusted so that the stoker is very comfortable.

Has something changed that I am not aware of?

wayne

twocicle

Would the term "straight-ish arms" aleive the consternation? Really though, yes I always heard the "slight bend" thing too and that certainly holds true for rough roads, but go look at photos of the pros for a good example of how to sit on a bike for 5 hours or more a day on normal roads. Typically the only time the arms are visibly bent is when lower in the drops.

Core strength when used properly is to stabilize the torso and keep a flat back, hips rolled forward. Using core strength to keep weight off the arms/hands for normal riding/roads is not correct. That would be a waste of effort. It works well for Roubaix/gravel roads, but will tie you up in knots if you try that all the time.

Carbonfiberboy 

Au contraire, I use core strength and bent arms 100% of the time. Longest single ride 18.5 hours, 15.5 saddle time. A fitter showed me how to use my core many years ago. A lot of it is being stretched out enough. Me and our tandem:
https://www.bikeforums.net/showthread...1#post12207030
I use the low_modified_hoods position a lot. Stoker's positions with the cowhorns are similar. For her low positions, she holds the bar-end and rests her wrists on the straight part.

I'll get a photo of our modified stem up soon.

Carbonfiberboy 

Here's the modified stoker stem. I cut it so that the inner part goes in as far as it can - it still hits the captain's seatpost. A 30° stem might put the bars a little lower, depending on the height of the seatpost attachment. This is the stock CoMo 29.8mm seatpost.

twocicle

Can't tell from the photo, but if the metric side of your tape is starting at the center of the post and at the top of the stem, your 125mm should be correct.

As your seatpost room is very limited and the seat clamp bolt appears to hang down, it looks like you are stuck with a 35 degree post. I was not able to find anything in the 125mm range for that rise angle.

Regarding arm positions, etc, I know I'm not describing myself very well today. Agree there are many positions as your linked post shows and I use those too. Just a bit head tired to word it better at the moment. My longest rides usually end by 6.5 hours. Last year the longest distance was a 112 mile Gran Fondo, but I was done in under 4:50. No 16.5 hrs on the bike for me thanks.

Carbonfiberboy 

Thanks for looking. I haven't been able to find anything either. That was a mountainous 400k.

waynesulak

Your positions look good to me and I commend your functionality. I suspect you do some stretching and core work off the bike.

Turbotandem

We have one of Bob Davis's few carbon stoker stems. I understand he is not really making them any more. Ours is about 215 on a belt drive length tandem, with a 5'-3" stoker using Profile base bars as seen on ritterviews photos. With replacement ti bolts the stem still weights in at 180-185g after weighting it last night. But still $360 to save 40g over the Onza/Trialtech no barigin on weight.

The trialtech or Onza stem, 180mm 35 degree also with replacement ti bolts comes in at about 230g (the bolts save 15g) for the $55 stem, $10 delivery, and about $15 for the bolts that gets us an $80 stem which we have on our CX tandem. When thinking about stoker position, a couple more watts power output from her, even if only because she is smiling, is more important than almost any weight savings.

We ride endurance, double centuries and what not, so comfort is important. A nice thing about the profile bars is that the horns reach is short from the upper position. Many bullhorn bars have very long horns that don't work well for a 5'-3" stoker. Her bars are about 3" above her seat. My bars are about 4" below my seat, but I am 6' so she is still mostly behnd me. One thing we do in time trials where area is important, is 1) change out the stem to a 140mm ritchey, 2) lower her position, and 3) rest her forearms on the bars and wrap her hands around the captains seat post.

Carbonfiberboy 

Thanks. Yes, quite a bit of both.

Ritterview

I found this gaggle of custom Ti stoker stems on a Google image search.

These are from True North Cycles, in Belwood, Ontario, Canada (so, not made in the USA ).

These titanium stoker stems were made for a customer that has a number of different tandems. The multiple lengths allow him to fine tune the stoker position for different riders.







I contacted Hugh Black at True North to ask him about these. He says they can be purchased at your custom length for $475. He didn't know the weight.

So, if anyone wants a very nice looking custom length stoker's stem in Ti, Hugh stands at the ready.

waynesulak

Those look great.

twocicle

I have been trying to coax my stoker to try bullhorns like the Profile Wing, but she is very set on having the dropbars for position variation and typically during a good part of our rides she enjoys zoning out in the drops and not bothering to look around... so I can't use that arguement. Since she is small at 5'2", the 145mm reach of the Profile Wing bars is likely too much of a stretch anyway (her current Ritchey Evocurve bars have a 83mm reach and 128mm drop) so they would require a longer stem to place the bullhorns closer to her and more in her reach range.

My motivation is to lose 290gms (50gms bars + 300gms stoker grips) by switching to those carbon bullhorns. If somebody made a proper set of lightweight stoker grips, I'd jump on getting those. Oddly, Cane Creek lists the pegs at 230gms, but when I weighed them it came to >300gms for the pair. Stubby computer mount style "stoker pegs" are not valid grips IMO.

Ritterview

How in heck does Cane Creek make those grips so heavy? These are more than SR EPS shifters, that have internals.




It might be up to you, twocicle, to show how to do DIY weight weenie stoker grips by gutting a pair of spent used shifters, and using mainly the shift lever body assembly. This might can use some old school drillium.




To make it really ww, you can attach the grips to the bar using carbon shifter clamps.

twocicle

Right. I was also looking at SRAM S900 brake levers (240gms) and trimming down the levers into stubs.

Much to my stoker's protests, I have ordered a Profile Carbon Cobra Wing bar for her to try out. We go through this every time I propose a change... like back when it was time to update her with "fat skis" she protested that she only knew how to use the skinny style, but loved the new ones on the first day.

We'll see how this goes with bullhorns and no drops. I'll work on her with the "vibration dampening" aspect of the carbon bars

colotandem

Another option that I was looking at for stoker levers is this, but not as light as the Super Record shift lever body assembly.
https://www.trpbrakes.com/category.ph...d=183&subcat=0

Turbotandem

FYI, I weighted the Trialtech stem last night. 180mm, 35 degree. WithOUT ti bolts I get 240g (on a Park scale that reads down to 10grams. Sorry I don't have a real gram scale) So I assume that means the weight is between 235g and 244g to read 240g on my scale. With ti bolts in place the scale reads 220g (so btwn 215 and 224g). That's under the online weight of 251g and likely lighter than a ti stem, if ths size and angle work for you. The 160mm would be just a touch lighter. Stem $49 from places like "expressive bikes" and others. Bolts about $15 save 20g. Plus shipping about $80 all in.

Ritterview

There are two 35 degree, 180 mm stems we've discussed on this thread, the Trialtech and the Inpulse Potence "R". A careful forensic image analysis reveals that these are different stems.

Pardon the large images, they are needed to spot the differences, which are most apparent at the stem bolts. The Trialtech has more of a circumferential buttress ringing the stem at the two bolts. The Trialtech also has a slight lip on the stem side of the handlebar opening that the Inpulse R lacks. The Inpulse R also has the fetching anodized red cap, which matches the red highlights on our bike, and my stoker likes that.

Inpulse R

Trialtech

Inpulse R

Trialtech




I ordered an aptly named Inpulse Potence "R" from Trials Addict in the UK.


When I receive it, it will be subjected to a rigorous and well-photographed weight analysis. The Trails Addict site lists the weight as 232 grams, somewhat less than is purported for the TrialTech.

Edit:

An owner of a 23-something pound Paketa tandem has no business not having a real gram scale The Park Tool Tabletop Digital Scale - DS-2 is $28.99 at Amazon Prime. You know what to do.

twocicle

I've had a chance to unwind and think more about what it was I tried to describe in haste during work hours. So today I did a quick search to locate a representative example and came up with this document with pages 10-12 depicting the gist of the position points I attempted to gloss over. Where the doc falls a little short is in the discussion of keeping a flat back and core strength. I would add that a good bit of keeping a stabilized position on a bike with very little effort can be attained by correct saddle position and angulation, plus a saddle that supports your pelvis in the forward tilt position. Then with the pelvis and back stabilized, there should not be a ton of weight foisted onto the hands and arms.

In the past I spent a fair amount of time with power meters and heart rate monitors testing various positions and finding what is the most optimum for me, and then validating that in formal performance testing. But as we all know, one size does not fit all. This is where I failed to make any differentiation in arm bend and what I have locked and drummed into my brain. My static back positions and bar height (tops & drops) does not require any significant arm bend when under average or light effort. While out riding the other day, I thought about it and concluded that the more effort I put out, the more my arms are activated and yes, bent. The ultimate effort and bend is of course - sprinting, and maybe 50% in headwinds.

John Cobb does a good job in his videos and docs describing efficiency and how pelvic/leg angles can help or hinder performance. He seems mostly dialed into Tri positioning, but I like reviewing his thoughts nonetheless. I totally agree with his points about how bending at the waist and not having sufficient pelvic rotation can close off the diaphram and inhibits breathing. Salient points like that would have been of much use to me back in the day, going back some 30 years ago.

Well, if any of this adds value and is of any use to anyone then great. Otherwise, well... chalk it up to just another bit of tripe.

Cheers.

Carbonfiberboy 

Agree. Here's a photo of us tooling along at 5 mph in the parking lot before the start of today's ride. This is after I cut 1.5" off Stoker's stock 35° CoMo stem, to her applause. Note the almost straight arms. Captain's new 17° stem is slammed. We do get down when we're going fast or hard, like the photos I referenced earlier, but not when it would be silly to do so. Getting aero is not so easy for short folks on standard road frames, but we do what we can. Our new positions are very comfortable for us.

Turbotandem

Note: I had our Bob Davis 215mm stoker stem off the bike last night and confirmed its weights as 180g. Lighter than I had remembered. And lighter than the 180mm trialtech stem. I went back and corrected the citations on its weight in my prior postings.

twocicle

That is an excellent weight for anything over 160mm. Can you post a photo of it too?

twocicle

You two are looking great in that position, the angles look spot on to me. It appears your stoker is not as far forward with her hands as she could be, so she may be cheating her arm position back toward her a little. If she finds she feels like there is not enough hand support and wants to brace more against the bar ends, you may want to slide the bars back a bit toward her w/o raising them.

I saw in your photos that you have very large-drop bars on the front. If you are very flexible (which most of us are not in this age group) then that may work well for you. I found that moving from a Deda 215 ergo bend w/145mm drop to a more compact 128mm drop design (Ritchey WCS EVOCurve) a very comfortable change. With the shallower drop, I can lower the bars so the tops are not as high, but still reach the drops with less hamstring strain than before. The Ritchey bars also have less of a reach than the Deda's I had, so a 1cm longer stem was needed to compensate - and that resulted in a better overall stretch without dipping so much in the process. At +50 years old, I've got to look more for efficiency and comfort than pure flat back parallel to the ground like a twenty year old... you know what I mean.

Carbonfiberboy 

Stoker likes the bars just where they are, so that's that. I never use the flat part of the drop bars, preferring the hoods with arm bend for that back angle. I go deep in the drops when descending or going really hard. Now that we have aerobars (see that thread), I will just use them for descending when I want my fingers on the brakes. Just my riding style. I don't like to have my forearms in the wind unless I'm just putting along. My bars won't drop any further, that's it. Thanks for the tips, though.