Adjustable Stem on TT Rig

El Loto said:

Last year I got a chap to build up a TT bike for me. We weren't sure about stem length so he just install a 90mm one. As I am in danger of whacking my knees off the handlebars I know I need longer one. I noticed this and wondered if anybody had a similar experience using an adjustable stem like this in TTs. I figure that it'll be possible to make a rather savage aero position with this stem.

Any thoughts/advice much appreciated.

For £48.44 you could buy several stems ... you should be able to get a 130mm stem via eBay for under £15.

ALSO, what may be more important, the particular stem is for older (nothing wrong with that) handlebar with a 28.6 center section ... and, if you just built up your TT bike, then the handlebar may have a 31.8 center section (yes, an adjustable stem for 31.8 OS handlebars must be available).

Now, if you had the bike built last year, why wasn't there a test fit BEFORE you spec'd the components AND/OR rolled it away from the shop?

I recommend you simply buy a 130mm stem for 1/3rd the cost ... of course, you can pay more.

In the meantime, try raising your handlebar by about 10mm (or, more) by adding some spacers beneath your stem to achieve some more clearance for your knees.

alfeng said:

For £48.44 you could buy several stems ... you should be able to get a 130mm stem via eBay for under £15.

ALSO, what may be more important, the particular stem is for older (nothing wrong with that) handlebar with a 28.6 center section ... and, if you just built up your TT bike, then the handlebar may have a 31.8 center section (yes, an adjustable stem for 31.8 OS handlebars must be available).

Now, if you had the bike built last year, why wasn't there a test fit BEFORE you spec'd the components AND/OR rolled it away from the shop?

I recommend you simply buy a 130mm stem for 1/3rd the cost ... of course, you can pay more.

In the meantime, try raising your handlebar by about 10mm (or, more) by adding some spacers beneath your stem to achieve some more clearance for your knees.

28.6 is the steerer section. The stem is designed for use on 26mm diameter bars; the diameter of bars on my bike.

The gentleman who built it was a friend of a friend. We agreed that I should just feel my way around it and then we could work on changing things like stems, etc.

I want to know if anyone has experience with using these stems to make a large negative angle to create a more aerodynamic position.

El Loto said:

28.6 is the steerer section. The stem is designed for use on 26mm diameter bars; the diameter of bars on my bike.

The gentleman who built it was a friend of a friend. We agreed that I should just feel my way around it and then we could work on changing things like stems, etc.

I want to know if anyone has experience with using these stems to make a large negative angle to create a more aerodynamic position.

Actually, the 28.6 size was probably a typo (which I echoed), and the center section on your handlebar is probably 26.0.

As far as using an adjustable stem on your TT bike, I know (have seen) some TRACK racers who use an adjustable stem for lowering their bar in some circumstances; so, why not for a TT bike?

The 'problem' is that the net reach will only be about 90mm ... which may-or-may-not work for you (it sounds as if you could have chosen a frame with a top tube that was ~1cm longer).

FWIW. Based on MY observation (several years ago), you can simply invert a Hi-Rise MTB stem in case you want to road test the riding position you are referring to.

Regardless, let your personal flexibility & comfort in the TT position for 15+ minutes be your limitation.

BTW. Negative angle (below horizontal) stems were common on older TRACK bikes ... as were smaller front wheels, at one time.

El Loto said:

...Any thoughts/advice much appreciated.

I use a Ritchey adjustable stem on my TT bike: treefortbikes.com125 333222343186 Adjustable 26.0 Black Road Stem.htmlOpen ↗

They're available in several lengths and clamp diameters. FWIW, my VisionTech base bars require a 26.0 clamp so it limits stem selection a bit.

The adjustable stem is great, especially if you're just figuring out your best TT bike fit or exploring the tradeoff between reduced CdA (translate flexibility and low position) and ability to sustain your best power. It's also good if you want a very low front end as you can run the stem at a very steep drop angle as Alfang points out.

I spent most of last season dialing in my TT position and by August I could comfortably ride a much lower front end than I could at the start of the season. The adjustable stem let me make small changes every three to four weeks until I found the place where my power started dropping and my comfort/up the road visibility suffered too much for long TTs. I'd just make sure I took some alan wrenches on training rides and made stem angle adjustments roadside when it was time for a change or if I'd pushed it too far.

And yes, I've ended up with the stem at a very steep negative drop reminiscent of some of the steep track stems I've used. And that's on a TT bike with a very short 95mm head tube.

FWIW I use profile Cobra clip on bars mostly for their fore-aft adjustment. It's a fine line on cockpit length, if I get the pads well out of the ways of my knees (in the position I'll ride while racing which tends to be pretty far forward on the saddle) my upper arms "reach" a bit far. IOW, the angle between my torso and upper arms is obtuse which puts more weight on my arms and is less comofortable for longer time trials.

If I slide the pads back a bit to give me a nice 90 degree upper arm angle I tend to clip the pads with my knees when going hard. I've split the difference and my current position has a very slightly obtuse upper arm angle but about as little as I can get while not clipping my knees when I go hard and tend to slide forward in the saddle. I definitely wouldn't want a larger frame as I don't want to be any more stretched out but for me the correct cockpit length is very close to the point where I'll clip the pads with my knees. For that reason I personally wouldn't go to an integrated base bar - aerobar design. I like to be able to have a bit of fore-aft and width adjustment on the pads.

Anyway, I like the adjustable stem quite a bit and would recommend it for folks that aren't very confident about their TT positioning or who are using a power meter to dial in CdA vs. power on a TT bike.

-Dave

daveryanwyoming said:

I use a Ritchey adjustable stem

I've got the same setup. Most TT bars still run 26.0 clamps.

I originally put it on so I could dial a fit in over a period of time, which I did. Ultimately I could go out now and buy something off the shelf thats a bit lighter and offers the same fit, but I've not bothered, the Ritchey is doing just fine in there, and I'm sure down the track I'll re-use it in some other application. Right now my TT rig is living in the trainer full-time.

I run the same setup in my aerobars for my track bike. Only difference there is I've got a couple of bikes, and having the adjustable position on the stem lets me use a single TT bar / stem combo that I can slip onto either bike and then dial the fit.