Drafting a Tri-Bike vs a Road Bike
 

Hi I was having a discussion with a friend and I was wondering if anyone has any knowledge of the difference in drag between drafting behind a TT style bicycle and a typical road bicycle while on a road bicycle. I think that the difference would be minimal but not sure and would like some link to factual data or some kind of reasonable explanation.

Thanks for your time.

No data but my impression is less of a slipstream behind a TT/Tri bike, because of reduced frontal area in lead rider.

Most of the draft effect comes from the rider's body, not the bike. If the rider in front of you has a very low riding position (because they are short and/or are hunched way over on the aero bars), you get noticeably less draft behind him or her

I ride with a guy who's around 5'7", maybe 150lbs and rides a tri bike. Drafting him is almost a waste of time compared to drafting a bigger guy.

I've drafted one of the fastest guys in my area when he was on a tri bike. He's around 5'10", 180lbs and I get a much better draft from him. It's still tough to hang with him though. I can stick with him until we get a crosswind, and then I usually fade away. He can hold 32-33mph for many miles (at least as many as I've stayed on his wheel) and once I lose him, I can't catch up.

It's hard to draft behind a hobbit
Pirk

Most groups will not allow a bike with aero bars in a paceline. There may be a reason for this.

The reasons are mostly from a lack of understanding. There's nothing dangerous about an experienced rider on aero bars in a group.

Agree. And yet, the contrary is often stated on the 41. : )
Experienced cyclists both Tri and road understand the limits of a TT bike when it comes to handling and adjust in pacelines accordingly.

But... both of you implicitly agree that aero-bars are more dangerous than drop bars for drafting and riding in groups.

It is inherently more dangerous because the handling is worse and the ability to respond to unexpected circumstances is as well, but as you note, experienced riders can mitigate this danger. Does not change the fact that, for any rider, aero-bars are less safe than drop bars.

Similarly, I used to be a rock climber, and I have had a number of people tell me over the years that is is more safe for an experienced climber to free solo (do roped climbs without a rope) than it was for a group of noobs to do the same climb with ropes. Well, perhaps, but that does not change the fact that, all things being equal, free-soloing is more dangerous than using safety equipment.

Even when risk can be mitigated to some degree, it is still risk.

PS For the record I have drafted with people using aerobars on a number of rides, and there have never been problems

Yeah. We have a couple guys who ride their TT bikes in group rides without issue. Skill, experience and judgement makes up for a bit less maneuverability. FWIW: Being in the drops makes drafting a lot more effective, especially if the rider in front is in the drops, or small.

I've done group rides with triathletes who paceline on aero bars. They're what I like to call "high-functioning" triathletes, though.

+1 It isn't just the rider's position, their size also has a big impact. Riding behind a very small 120 lb guy/gal riding in the drops doesn't give much draft compared to a 180+ lb guy well tucked in. After drafting behind the 120 lb guy, then going to the front to pull, there isn't much difference.

I agree with everyone, height is the most important factor. I drafted a 6'8" guy on a TT bike and it was a dream, in contrast a tiny chick was cruising on her tops and I couldn't pick a slipstream out... didn't keep me from drafting for longer than absolutely necessary.

Ummmm. Yeah right. They haven't free solo'd and taken a fall. Meanwhile noobs TR-ing at my gym are falling all night on 5.8's and walking home to tell about it...

Does "high functioning" mean they can still train after crashes?

Means they don't crash. It's very possible to ride aerobars in a paceline if everyone is skilled.

I was joking. I occasionally train with a group of triathletes and many do ride aerobars, mostly to get the miles in that position. There have been two accidents in the entire time I've known them/ridden with them (maybe eight years) and neither had anything to do with aerobars

That's most impressive since even the pros don't even go that fast in their TT's. ;)

That's what I was thinking.

Never ever ever draft a TT bike.

Those guys and gals don't stop for anything. :eek:

He is using BF speed. Take 2/3rds for real world.

Bit of an oxymoron here: drafting in a paceline on a TT bike. As most triathlons disallow drafting, training in a paceline on a TT bike kind of defeats the purpose of it. The purpose of an "aero" TT bike is to be faster solo than a comparable rider on a roadbike.

FYI, there are TTTs: Team Time Trials, where teams of 8 or 9 riders ride a TT on TT bikes in a pace line, like stage 4 of this year's TDF, for example.

And they ride SCARY fast!

Read this article on LeTour.com

25 km at about 58 km/hr average, or
15.6 mi at about 36 mph average.

Wow!

FYI, for myself being 63yo and doing triathlons, when I am riding with the group as in today's ride, the effort I am expending drafting these younger guys doing 26 to 30 is more of a workout for the extended time they are pace line riding than I could do on my own at much lower speeds. What really helps is the time I pull. Much shorter time frame than the young'uns but one heck of an effort for me.