Tandem Cycling - Stem length fit question

I am considering purchasing another frameset. I can go with either of 2 sizes- 1 would put me on an 11 cm stem, and the other would require a 14cm stem. I tend to lean towards the longer stem to put more weight on the front wheel. Both frames have the same 73* head angle and fork rake. Thoughts?

How tall are you? That seems like a big difference between the two frames.
It also dpends on the handlebars. I changed recently from bars with a long reach and drop to compact bars with a short reach and drop and had to increase the stem length from 10 to 11cm.

I am considering purchasing another frameset. I can go with either of 2 sizes- 1 would put me on an 11 cm stem, and the other would require a 14cm stem. I tend to lean towards the longer stem to put more weight on the front wheel. Both frames have the same 73* head angle and fork rake. Thoughts?

Tandems already have more than enough weight on the front wheel. Also, I wouldn't spend too much time fretting the difference in steering lever associated with the 110mm vs. 140mm stem. There are just too many other aspects associated with reach and how you set-up the front end of your tandem to consider (i.e., bar choices, shifter placement, where you tend to put your hands on the bars) that will also drive your fit and comfort to focus too much attention on stem length so long as what you're looking at is in the ball park for stock stem lengths.

Instead, focus your attention on the other aspects of the frame's fit for you and your stoker, i.e., saddle set-back, saddle height above the top tube, standover height, and even water bottle placement. As for your stoker, consider where her stem and handlebars will end up relative to your saddle's position, both height and set-back.

Plus a 140mm stem leaves little room for adjustment at the far end. Besides, I don't think i have ever seen a 140mm stem.

OK, then let me rephrase the question. The tandems I am considering all have 73/73 angles, and my saddle position is my saddle position. I've calculated the stem length I need based on 3 existing or previous tandems, using the bars and components I'll use on the new frame.

For the smaller frame I'll need a 112.5mm stem, and for the larger frame I'll need a 137.5mm stem. The stoker compartment won't change, except for standover. Stoker reach remains the same.

I'm 6'1", long arms, and 58.5 cm from the saddle tip to the center of the bars.8.5cm saddle setback (Not that any of this matters:)

Short stem or long stem?

Co-Motion sells and *adjustable* pilot stem.

I am 5'8" and use a 110mm stem. You must have something backwards, the larger frame should require the shorter stem. I would go by the top tube length that mtaches your single bike.

I would go by the top tube length that mtaches your single bike.

+1



OK, then let me rephrase the question. Short stem or long stem?

No need to rephrase, it only makes things more vague. As previously stated...

Focus your attention on the other aspects of the frame's fit for you and your stoker, i.e., saddle set-back, saddle height above the top tube, standover height, and even water bottle placement. Let me add stem rise and stack height to that list as well. Again, the sem length alone shouldn't be a make or break as the shorter frame will have a shorter head tube, shorter seat mast and/or a different slope to the top tube and you'll also have less toe clearance. Therefore, additional considerations should take in account that the shorter frame would have to have several spacers below the stem or a lot more rise in the stem to place the handlebars in the same position relative to your saddle height on the larger frame and so on.

So, if none of those things is a driver for your decision and you're simply asking for OUR highly subjective opinions on whether or not a relatively normal length stem on a larger frame or a extra long stem on a smaller frame would be preferrable to US, my preference is to stick with stems that are in the mid-range or that tend to be shorter, noting that I myself actually use 90mm and 100mm stems on our tandems. But, then again, I have a shorter than average reach.

1) well done for calculating your fit, including bar reach and shifter position. I have been caught out more than once by differences here.

2) Stem length of 14cm suggest the length of the rest of the system is too short. Bikes steer well with stems in the range 9-12cm, and this is what most people use. They will also steer fine, albeit a little slower with a longer stem, but this is not ideal on a tandem since you need to turn the front wheel twice as much on a single since the wheel base is twice as long.

14cm frames are very rare and usually only used by average sized people who need a low bar placement but are forced to buy a bike with a relatively long head tube because it's what their sponsor makes. Here the fact that they're dead skinny and tend to sit far back means their weight distribution is still fine.

The other reason is people over 6'3" who want to keep the rest of the bike in proportion and buy a custom frame. Even then, most use 12cm stems as the longer stems can be flexible and off the shelf larger frames are still not designed to take 14cm stems.

Finding a 140 mm stem is going to be difficult. They're made, but there's not a big selection. I looked awhile to find someone that actually had a 140 mm stem, to replace the adjustable stoker stem on our tandem.

Also, I'd bet that going with the frame size that uses the 110mm stem is likely to give you a better overall fit. And if your calculations are off, you can adjust with a stem either longer or shorter.

If you're off with the 140mm stem, you have virtually no option of going longer.

Finding a 140 mm stem is going to be difficult. They're made, but there's not a big selection. I looked awhile to find someone that actually had a 140 mm stem, to replace the adjustable stoker stem on our tandem.

Also, I'd bet that going with the frame size that uses the 110mm stem is likely to give you a better overall fit. And if your calculations are off, you can adjust with a stem either longer or shorter.

If you're off with the 140mm stem, you have virtually no option of going longer.

+1.....go short.

Bill J.

I was also thinking about weight distribution since the longer stem puts more weight on the front wheel. It seems that with a light stoker, it may be better to run a shorter stem to weight the rear more, and with a heavy stoker it may be better to run a longer stem to reduce the rear wheel burden.

In all cases, less weight on the front wheel seems safer in the event of a pothole/ road hazard that might result in a blowout. I've had a few front deflations and they are not fun.

I've decided to go for the longer top tube/short stem combination.