Ritterview

I just received the Inpulse R 180 mm, 35 degree stem. 230 grams with steel bolts. Bolts weigh 32 grams, and so sans bolts, 198 grams. If Ti bolts save 20 grams, it should come in then at 210 grams.



How do I know what size and thread Ti bolts to order, and wherefrom should I order?

DubT

You might try these guys: Call them and describe what you need.

https://www.imperialbikeco.com/catego...Ti-Stem-Bolts/

Turbotandem

We adopted the cobra wing bars last year. After a few rides she loved the wide riding surface as much "softer". And the horns are quire short. At first we had to wrap the bar all the way to the stem to cover the rim where a stoker might get accustom to hooking her thumb. But after a while we backed off the tape and have it more on the horns and less on the upper.

Turbotandem

Ti bolts will come in at helf the weight of steel. So expect to save 16g on 32g of steel bolts.
I went to a local long term hardware store and had them size the bolts. In the case of trial tech M6x20mm with a captured washer. While the Ritchey are M5. USA Ti on ebay has a great assortment of 6 bolt stem sets. Some say "for Ritchey this or that". Some sets just say "stem bolts". I've also ordered from some UK suppliers but they take a long time. The bolt length is measured from the tip to the under side of the head. That is, don't include the head in the length. It should not matter a lot if you get tapered head or not, but the tapered look better.

twocicle

We had our inagrual ride with the Cobra Wing on Saturday. I was Linda's first ride with a cowhorn style bar and she liked it... a lot more than her new and very firm Terry seat which she had not ridden outside until then. The Cinelli cork tape wrapping ended up going from bar ends to just around the bend corner, leaving the middle hand rests bare carbon. It too no less than 3 times changing the wrappings (and one entire package of wasted cork tape) until she finally approved. Still not sure she likes the feel of the bare bar, but definitely likes the look. TBD.

Ritterview

Removed the Calfee stem, and replaced it with the Inpulse R stem. This provided an opportunity to weigh the Calfee adjustable stem. 255 grams is pretty good for an adjustable stem, the Inpulse R saves only 25 grams, almost an ounce (28.35 grams). I'll have to philosophize that the proverb many a little makes a mickle is archaic, so it must be true.

Turbotandem

You'll have to custom paint the new stem to match. Ahh, but that will add back much of the 25g!

Does the new stem meet the length you had set on the adjustible?

Ritterview

More weight painted? Not if I strip it, and have it Ceramikoated!

I haven't analyzed the length and rise yet. Its a skosh closer in to the seatpost than the Calfee at its shortest, as evidenced by the Garmin 705 on the handlebar not fitting between the bar and the saddle anymore.



Edit:
This is what it had been like, with the stem all the way in. Looks to be up to an inch further in. Stoker may not tolerate this. I think that when I say something is more aero, she hears it as fiendishly contorted.

twocicle

... and even more weight to add with a computer mount extension. EGAD, another 20gms!! LOL


We now have the Thomson setback post for both captain & stoker + a 130mm/17degree stem for the stoker. That stem is mounted high on the captain's seatpost, 1cm above the bend in the setback post. This places her reach nearly identical to what we had with the straight post + a 140mm/17 degree stem. Current photos posted here.

My stoker is very lightweight and doesn't muscle the bars. Probably a good thing because with this setup I can fairly easily bend the Thomson seatpost side to side as I perform a little post-install "stress test". The seatpost is inserted far beyond the "minimum" line on the post, so that should not be a factor here. There are other more stout seatposts with setbacks that I could use, but I do like the Thomson posts and have quite a few on hand... so I'd like to stick with these.

Has anyone ever broken a captains seatpost due to side-to-side stoker bar stresses?

Turbotandem

Never broken a seat post. But the standing rule of thumb is that carbon seat post manufacturers do not endorse the mounting of stoker bars to the post for that reason: potentially breaking the seat post.

Turbotandem

215mm bob davis stem photo as requested. Stem is 180g +-4g

bradcycles

That Garmin 705 isn't very weightweenie-ish. You can save about 50 grams by switching to a garmin 500. It will be much easier to install than your new seatpost.

Ritterview

The Garmin 705 is an indulgence. It replaced an ANT+ Bontrager Node, (20 grams lighter than the Edge 500) which is now on Mrs. R's half-bike, but could be returned if we ever need weight weenie mode.

Carbonfiberboy 

Put stoker's Garmin on a Bar Fly. My stoker really likes the shorter stem. Closer to ordinary road position, which is more comfortable on long rides.

uspspro

I finally found what I was looking for!

150mm, 17 degree stem.. and it's light! -- ~149g



We used to have a 150mm fixed stem with 6 degree rise. The reach was great but the drop was slightly too much. We switched to the beefy Control Tech adjustable stoker stem, which was better but on the verge or being too high. I'm hoping this new stem works perfect. I calculated the rise to be about perfect, and the reach to be a few more mm than before, very close to her single bike fit.

They sell these on Fairwheel Bike, but only up to 140mm. This comes straight from Taiwan.
https://www.ebay.com/itm/ws/eBayISAPI...m=140937076504

twocicle

Nice find.

With my setback Thomson seatpost and the new Profile Wing stoker bars, we are currently using a 140mm/17degree 3T ARX stem @ 148gm. In order to provide better arm angle/support, my stoker needed the Wing bars a little closer and lower than the drop bars were. I think we have it dialed in now.

A new stem coming out is the 20 degree Deda Nine, designed for 29er angles. This stem will have a max of 140mm, which should be ok for us and allow me to mount it about 8mm lower on my seatpost (the upper bent section) and maintain the current bar height. The net reach will be just a couple mm shorter than our current 140mm/17, and based on the Deda Nine 110mm weight my guess is the 140mm should be equal or lighter than the 3T.

https://www.dedaelementi.com/index.ph...mid=89&lang=en



Again, working out the angles (including the +10 degrees for the setback post) and reach using https://yojimg.net/bike/web_tools/stem.php

UPDATE: CAUTION ON DEDA MEASUREMENTS. Deda stems come up a little short as they apparently measure along the top of the stem (photo above). ie: their "140mm" actually measure more like a 135mm Ritchey/3T.

Rambetter

I'm in the market for an adjustable stoker stem, if any of your have taken off yours and replaced it with a fixed one. Seat tube is 27.2 and handlebars are 26.0. Need about 180 - 200 mm.

twocicle

Cement filled or lead lined?

Turbotandem

A tandem friend in wy suggested Dean Bikes in Boulder Colorado makes nice ti stems for their custom ti bikes. Since john at Dean Bikes lives literally thru the party wall of my town home I talked to him. Indeed Dean Bikes is excited to make them in any length and angle and custom clamp sizes such as 27.2 seat post, in ti and around 180g for $250. For longer stems thicker gauge ti tubing is used. 2-3 Weeks fab and delivery. My Wyoming friend has one already in the works. Contact dean bikes directly.
John and Ari at Dean Bikes are both up to speed on the stoker stem. Pictures below

twocicle

Sounds like a very good value for a Ti stem. I had looked at stems from Ti Cycles Fabrication of Portland, OR, but those are $335 for custom fixed length stems (ie: non-production) and $550 for a Ti adjustable (only 193gms, w/26mm bar clamp, and only a 9cm max length!) on their perpetual eBay posting ("make an offer" results would be slightly less).

Update on the Ti Cycles eBay posting noted above, received this response to my inquiry about the adjustable stoker stem length:
Still, I doubt their prices would be anything near feasible, or that of Deans Bikes.

Ritterview

At Weight Weenies, there has been a useful thread for tandems on 150 mm stems. Some pro riders are using smaller frames but longer stems. For example, Taylor Phinney, with an Arx II Team, that's listed on the 3T website as available in 150 mm. Its claimed weight is 120 grams in 110 mm.



Taylor Phinney's (BMC) BMC GranFondo GF01 features a massive 150mm-long stem with a -17° angle that's slammed down atop the headset cover.

The Deda Newton 31 also has an 18 degree, 150 mm version. This is listed as 125 grams in 120 mm.

Turbotandem

I've not found those two (or others) to be available, even though listed on manuf web sites when I was looking a bout a year ago. I The 3t and deda may be close to the weight of the trial tech 150mm, at 214g, when you adjust the listed weight for 150mm. I'll check with the team ordering the Dean ti stem to see if it made it out of the shop back up.

twocicle

Two good 150mm x +/-17deg stem options are now available. Both are mentioned in earlier posts above.

1) KCNC Arrow from Bike24.com. 55 Euro + shipping from Germany. Ti bolts. 130gm for 110mm.

USPSPRO reported the 150mm to be 149gm, non-flexy and happy with it.


2) 3T ARX II Team (red stripe, Ti bolts). $100 includes shipping. 120gm for 110mm.

I just ordered the 3T so I'll have a true 150mm weight posted soon. Update: Actual weight: 160gm



We already have the ARX Pro 140mm which works fine for our stoker drop bars, but with cowhorns those tips extend a bit further forward so the 150mm should move them back to the same points as the dropbar stoker hoods.

FWIW, I have a new spare, ARX Pro 130mm x 17deg sitting here.

Bad1

https://www.bikeforums.net/forumdispl...ar-Marketplace

Bad1

BTW as far as (aka Chadrider) thats not me!