All things being equal how much faster pace could someone average on a tri bike than a road bike?
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My âeasyâ rides on a road bike will be 19mph ish. My âeasyâ rides on a TT bike are about 21mph ish.
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Some bit faster, or not at all
Depends on your positions (difference between road and TT), ability to put out power in TT position, comfort in TT position (can you actually hold it for any reasonable length of time)
Friend of mine went slower on a TT bike. could never adapt to the position, and his position wasnt that great anyway
Personally I am about 3-4kph faster average over a 300w-ish effort
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At a somewhat recent 8 mile, double turn around TT event I raced both bikes. My road bike was with 50mm wheels and no TT helmet. The same pedal PM was used for both bikes. Previously Iâve gone faster on the TT bike but that day had some decent crosswinds.
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@Majoeric so without the crosswinds with conditions being equal would you say about 2 mph faster on your TT bike?
@ErickVH my tempo rides are around 21-22 depending on the winds and how Iâm feeling. Iâm very aggressive in my riding position so I donât think the aero position would bother me that much. Would it be safe to assume 23-24 is achievable over the same wattage output?
Iâm about 2 kph faster on my road bike with clip-on aero bar extension than on the hoods. Itâs taken me a few months to get my aerobar FTP to within about 5W of my upright FTP.
I could probably do better than this on a dedicated TT bike with my position more optimized for the aero position.
2mph is a push⌠I would assume 1.5mph is realistic.
I consider myself somewhat dialed in on my position on both bikes.
The TT bike is a SpeedConcept and the Road is a Aeroad. Both had same Corsa tires.
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1 to 1.5 mph for me.
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Nope. Just go ride your bike, optimize it as much as you can.
Its going to also depend a LOT on the roads and route in the real world rather than a perfect situation.
Can you actually hold the aero position on the roads with the traffic, junctions, road conditions etc? Around here you wouldnt last 5 mins riding in a tuck except on main roads, simply due to the horrendous state of the tarmac, the type of narrown country roads etc. Then you have to content with high volumes of traffic etc.
All things being equal I think the estimates about of around 1.5mph are probably fair if you have a good aero position on the TT bike and have enough time on it that you dont suffer the huge power drop many people do initially.
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As already said, it depends on equipment, position and ability to ride this position with comfort and power.
For me the difference was huge. I rode 37kph during my last IM and my roadbike average is more like 30kph.
But the tri bike speed was on a race course and perfect conditions and the roadbike average is on roads with traffic.
Disc wheel should be around 0,5kph faster, helmet, suit, position, aero bottles, tires, etc are normaly different on a tri bike, too and make a huge difference.
But if you only compare the tri bike frame with an (aero) road bike frame, there is probably almost no difference at all.
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A friend of mine was similar on his aerobike with clip ons he was faster than on a dedicated TT bike.
As to the original question I have to go back 8 years on our generally up hill sporting club course on a road bike (so hardly comparable) but for 10 miles its circa 2mins 15 (2mph ) slower.
2mph for me but itâs not just the bike. If I ride my TT bike (disc and 90mm front) in a TT I use my Giro aerohead, Castelli fast feet overshoes, a nopinz flow skinsuit and aero gloves. If I use a road bike (Campagnolo Erus 1450g 28mm climbing wheels) I usually use it for training so often ride out to the race so itâs bib shorts, no overshoes, standard cycling mits, castelli jersey (tight but not a skin suit with some spares in the back!)âŚI do use Conti GP5000 25mm tyres with latex tubes on both my TT and summer road bike 
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With equal fitting clothing, wheel and tire setups and very aggressive positions on each, I am looking at about a 3-4 km/h difference between road and tt bike ( 2-2.5 mph )
Only real difference in my setup is that on the TT bike i wear a giro aerohead vs a giro vanquish ( aero road helmet ) and the rest is down to position on the bike.
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Of course, this is also dependent on having a proper, good position on the bike, if you donât get a great tt bike fit, then your aerodynamics will suffer, as will your comfort, your ability to produce power, and your ability to hold the position, all of which are important.
Is there any data on all of this ?
Iâm currently looking at buying a new bike for my Ironman race in 2023, and the more I read, the more I think that Tri bikes are mostly hype. II struggle to find data backing up the Tri bikes advantages with some kind of testing protocol. Any pointers would be highly appreciated !
Loads of data - mostly from the manufacturer though. I ride a dedicated TT bike - wouldnât ride anything else in a TT unless itâs a road bike TT which I also enjoy. That said although I have done a lot of triathlon I donât currently have to run off the bike so donât have to worry about that (although I was a good runner and always believed that generally good runners run off the bike well provided they donât go mental on 2 wheels). The biggest gain is aero bars so a good road bike with a set of clip on bars will give you 90% of the aero gains. That said itâs a faff taking them on and off for group rides etcâŚso if you can afford a dedicated TT bike itâs by far the best option. If not a good road bike with clip on bars is okâŚprovided you can get the saddle forward to rest on the bars (TT bikes have steeper seat tubes). In addition a good skinsuit and aero helmet make a big difference. As does a disc, if you ride a race that allows them and a 80-90mm front wheel. Plus GP5000/ Corsa speed tyres tubeless or with latex tubes. All the gains are smallish but they really add up.
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The gain isnât the bike, itâs the position the bike puts you in. Youâre the biggest source of wind resistance. In the wind tunnel with no rider I doubt there would be much if any difference between an aero road and TT/tri bike, certainly not if both were set up with a deep front wheel and rear disc. Stick a rider on though and a good aerobars position is faster than a good hoods/drops position, and more relevant for an ironman is that itâs a much easier position to hold for long distances. Since your weight is supported skeletally on the pads, as opposed to having to support yourself muscularly as you do on the hoods or drops. Not many people are capable of riding an aero hoods position for 112 miles.
You can of course put aero bars on a road bike, and plenty of people do. But sticking aero bars onto a good road position wonât lead to a good tri position - your front end will be too high and not far enough forward, your seat will be too far back. You can maybe get a good tri position on a road bike with a zero offset seat post, saddle slammed forward, long stem, take out all the headset spacers, maybe even a negatively angled stem to get lower. Or can look at Redshift who make components that make it easier to switch between a road and tri position. Certainly not a bad option if youâre constrained by budget or space. But still will be a compromise as youâre riding a position that that bike geometry wasnât really designed for and isnât optimised for - handling wonât be great as your weight will be too far forward, when itâs set up for tri riding the hoods and drops wonât be in a good position for road riding, you wonât have shifters in the aero position unless you have electronic shifting and can set up extra blips, etc. So if you have space and budget then having a bike designed to be ridden in the road position and another one designed to be ridden in the tri position is definitely the best choice, and one that all pros and most serious amateur triathletes make.
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It is 100% about your goals. If you are honestly targeting Kona, get a tri bike. It is absolutely faster, something on the order of a few minutes up to an hour depending on a lot of factors. Whether that is âworth itâ to you is a totally different question. I did an Ironman earlier this year, and I rode my Tarmac SL6 with deep wheels and aero-shaped traditional drop bars (no extensions). Did I give up time? Definitely, but I love that bike, riding it is super comfortable, I put out great power on it, I didnât want to give up my power and familiarity on it as I do lots of group rides, fondos, etc. throughout the year, and I had a great time on the day because I rode it. So, for me, it was definitely âworth itâ to ride the road bike. But that is just me. I think I was pretty much the only person riding a bike like that (no aero extensions on road bike and no tri bike) on the day, but it was a small event. Donât let anyone tell you whether it is âworth itâ or not. You have to weigh that for yourself.
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