vettracer

While watching the Grand Tours on TV this summer, I noticed many pro's using a different aero position on downhills. They are sitting on the top tube butt up aginst the seat post and hands together near the stem. It seems like it would reduce frontal area fairly well.

On my commute I have a steep decent where I usually hit about 45 to 50 mph depending on the wind.

This morning as I started down the hill, I decided to give the position a try. First off I noticed that it really seems to shift your weight forward, when you think about it no surprise there.

As I got close to 50mph, the bike started a slow weave from the front. Now this was interesting. Not wanting to upset the bike with sudden movements, I sat up a little and slowly shifted my hands away from the stem. I found you can't sit up much before your back hits the nose of the saddle . Moving my hands out helped a little, but the bike still really wanted to weave. I decided at that point to move back to the seat. To get my butt out from under the seat, I had to move forward even more, BIG WEAVE .

As soon as my butt hit the saddle, bam, rock solid straight ahead as usual. I don't think my bike likes that riding position.

Next time I think I will try out someting new in smaller steps

Has any one else tried that position? Experiences?

Lexi01

Yep.

It also gives your lower back a bit of a release/rest.

Nbob

Probably the most dangerous position there is on a bike. Pros do it because they get paid to take risks and their risk is less than the typical "enthusiast" because ;

1. They have pro wrenches that check the bike for soundness before every race/stage - particularly, in this case, the wheels and head set

2. They typically weigh less than the average joe and so put less weight on the front wheel ( the probable cause of your weave). When you watched them on TV you might have noticed it's mostly the smaller/lighter guys who do this in hopes that the extra-aero position will make up for the weight advantage the heavier guys have going down hill.

3. They have excellent cores - they can use their abs, etc. to hold back much of their weight from the front end ( i.e. do a sort of crunch to pull the upper body back)

justkeepedaling

Done this many times. Never had the bike weave though. Did almost have the fork hit my legs once though when trying to turn in that position, not a good idea

zitter

i do it all the time on descents, it just takes some practice

i sit on the top tube with hands in the drops and chest basically resting on the stem

pretty much this



it's very easy transitioning between the positions if you keep your hands in the drops instead of on top near the stem since you can push yourself up a lot more easily and still stay stable

you have to grip your headtube/downtube or fork with your knees to keep from sliding off the front and look for bumps so you know when to lift your chest off the stem

btw i weigh 180lb so anybody can do it easily with practice

vettracer

Hey thanks, I tried that today and with my hands on the drops, it was stable, no weave problems. It still feels weird with all the weight over the front wheel though.

It will be interesting to see if there is a consistent difference in speed that way.

datlas 

I must be a wimp.

That position looks too risky to me.

MrTuner1970

Me too.

Not to mention most of the hills I could try that on are bumpy old chip seal. Sounds like a recipe for a face plant....

Beaker

And most important of all...

4. They have no traffic to deal with.

Lexi01

From looking at the pic in the post from Zitter I take my "Yep" back. I misunderstood. I've never done that. I don't think I'd fit in that position on my bike!

Clipped_in

Ding ding ding ding!!!! Lots of things the pros do don't make sense for the rest of us - on open roads.

rat fink

I do it, too. I mostly do it the way shown here:



If you do it with your hands close to the stem, It's reputed to be more aero, but I prefer having my hands in the hooks, because I can steer through a sweeping curve, or around obstacles that way.

zazenzach

seem dangerous if youre doing this where there might be peds or traffic.

what happens if you need to stop or slow down quickly?

Perp

Hopefully you are looking ahead of the road and you can get back to the drops to slow down. I did this position (hands next to stem) in a race yesterday on a straight downhill. Not brave enough to hold that position in a turn.

Seattle Forrest

My tops are (sometimes) good for climbing, but not for descending.

carpediemracing 

For the OP - if you start weaving when doing the top tube sit thing, you're letting the bars move too much. It may be that you're steering with the bars in general, rather than with your hips. Ultimately it's more stable to steer from the hips.

The top tube tuck allows the rider to rest the legs. It's also more aero for taller riders than other tucks. Taylor Phinney and other tall riders will typically use the top tube tuck in time trials and such. Shorter riders (I would ride size S Giant; my bike has a 40 cm seat tube) like me work well with a face-over-front-tire, hands-at-center-of-tops, chest-almost-on-bars tuck. I've burnt my chin on my front tire before (once).

This is kind of like the whole tailgating thing when driving. I don't tailgate unless protecting a spot in heavy traffic but generally speaking I'm closer than 120 feet at 60 mph, maybe more like 60-80 feet. Most cars, including mine, won't stop from 60 mph in 120 feet. But unless someone drops a huge concrete block in front of the car I'm following, I'll have some time to react.

Also, I'm not staring at the car in front of mine's bumper - I'm looking around.

It takes a half second to go from a full hands-on-tops-next-to-stem to the drops and braking. Seriously. After multiple posts about safety of a downhill tuck I tried it to see exactly how "risky" it is. It doesn't feel risky at all. It takes me maybe 40-50 feet? without panicking.

I can do a full tuck in close quarters if in a group of reasonably skilled riders (racers or ex racers or experienced group riders). I do the compromise tuck (hands on drops) when around riders I don't fully trust (i.e. local shop group ride).

In real turns you can't use a tuck, but for curves and such you can.

Holding the bars next to the stop on the tops are the absolutely most stable position when going really fast or when riding one handed. It doesn't mean you can do anything else, but as far as stability goes, it's the most stable. It reduces any rider input to a minimum.

The drops are best for all-out control, i.e. braking, steering, and over massively rough pavement.

The tops are good, one handed, at over 50 mph on rough terrain.

Bobsled

You mean like this?



By the way, I'm awear who this is and in no way imply or infere or anything else that riding in this position is either safe or dangerous. I'm simply responding to the OP with a different point of view to his question.