TT vs adapted road bike
Discussion
What do we think is the real world performance difference is between a full TT bike and an aero road bike adapted for TT'ing?
I'm keen to move into TTs but my pockets aren't deep enough for n+1, so I'm in the process of adapting my Aeroad in the most bang-for-buck way possible. For reference, I'm probably about Cat 3 ability and would hope to be turning out a decent pace. My main goal is long distance TT (100 mile, 12-hour, 24-hour) but training will inevitably include lots of 10s and 25s. The Aeroad has 50mm Cosmics, clip-on aerobars and a saddle I can ride in a tuck, but I'm a bit stretched out and I can tell I'd be better off with shorter and lower.
With all that in mind, what sort of time penalty do you think that would give me on a 10, 25, 100?
I'm keen to move into TTs but my pockets aren't deep enough for n+1, so I'm in the process of adapting my Aeroad in the most bang-for-buck way possible. For reference, I'm probably about Cat 3 ability and would hope to be turning out a decent pace. My main goal is long distance TT (100 mile, 12-hour, 24-hour) but training will inevitably include lots of 10s and 25s. The Aeroad has 50mm Cosmics, clip-on aerobars and a saddle I can ride in a tuck, but I'm a bit stretched out and I can tell I'd be better off with shorter and lower.
With all that in mind, what sort of time penalty do you think that would give me on a 10, 25, 100?
This doesn't really answer your question, but I found it impossible to "adapt" (I assume you mean add clip-ons) my road bike (Giant Propel SL). When I do duathlon I use a standard road setup with a skin suit, deep wheels, aero helmet, low position w/ elbows bent etc. I have found this quite significantly faster than when I tried change the set-up to accommodate clip-ons - lost far too much power.
Suppose what I'm saying is bear in mind that trying to turn your road bike into a TT set-up may not result in improvements for everyone. Depends on both the bike and rider of course.
I'm interested to know what the answer to this is though, what gain do you get simply from a TT frame and the ability to use bars without compromise, all other things being equal?
Suppose what I'm saying is bear in mind that trying to turn your road bike into a TT set-up may not result in improvements for everyone. Depends on both the bike and rider of course.
I'm interested to know what the answer to this is though, what gain do you get simply from a TT frame and the ability to use bars without compromise, all other things being equal?
I'd asked something similar elsewhere and my take on the feedback is that I'd ruin my road bike as a road bike without really getting my of the TT benefit. So I'm going the N+1 route (probably). Going on a jig this Saturday to see how well a medium or a large framed Boardman Team TT (£800 new) would work for me. Assuming one of them does and this time I can get on with a triathlon position then I may, at a later date, buy something more expensive.
Are your clip-on bars on top or below your normal bars? Trek did this at the tour with some extra rolls of bar tape as padding for your forearms on the normal bars:
You need to be low at the front and further forward than you would otherwise be so unless you can get your saddle far enough forward and your bars down, it's not going to work properly and you're probably better off just riding your road bike in your normal position.
You need to be low at the front and further forward than you would otherwise be so unless you can get your saddle far enough forward and your bars down, it's not going to work properly and you're probably better off just riding your road bike in your normal position.
It depends.
IMHO the BIG issue with adapting a roadbike to a TT position is whether you can achieve an equivalent position on a roadbike geometry. Being flexible will help.. Don't think you can just bolt clip-ons onto it and change nothing - you most likely need the saddle as far forward as it will go, a very short stem, and to get the bars as low as possible.
IF you have the same position on both bikes, the difference will be there, but probably not so much. There are round-tube TT bikes, frame aero is rather secondary to body position aero!
The problem with getting a TT position on a roadbike is the geo. You want to go low in the front, but you can only have so much hip angle - thus your ass has to go forwards. That means the seat. Roadbike seat angles are slack (laid back). Assuming you can shove it forward far enough to get a reasonable effective seat tube angle, you then stick a lot of weight over the front, and it (may) handle hellishly. TT bikes fix this by having the front centre further forwards and shortening the seat stays/drawing in the rear wheel as much as they can.
Next consider the front. Your hands on the hoods - now imagine clip ons - you moved them a lot further forward - that doesn't work unless you're after a superman impression. It's compensated to some amount by moving the seat, but you probably want a much shorter stem. Then the head tube is possibly too tall.. you can work around that with a negative stem perhaps.
Admittedly I'm as flexible as a concrete block, but trying to get 'aero' on my roadbike didn't work at all well for me. Moving to a TT frame (an old 'classic' P2) made a world of difference.
ETA: You've already alluded to the differences. Try shoving the saddle forwards (and it will need to rise a bit to compensate), fitting a short stem (I ran a MTB style very close coupled one - 40 or 50mm from memory), and playing from there. That'll shorten the cockpit, and you can play with height.
IMHO the BIG issue with adapting a roadbike to a TT position is whether you can achieve an equivalent position on a roadbike geometry. Being flexible will help.. Don't think you can just bolt clip-ons onto it and change nothing - you most likely need the saddle as far forward as it will go, a very short stem, and to get the bars as low as possible.
IF you have the same position on both bikes, the difference will be there, but probably not so much. There are round-tube TT bikes, frame aero is rather secondary to body position aero!
The problem with getting a TT position on a roadbike is the geo. You want to go low in the front, but you can only have so much hip angle - thus your ass has to go forwards. That means the seat. Roadbike seat angles are slack (laid back). Assuming you can shove it forward far enough to get a reasonable effective seat tube angle, you then stick a lot of weight over the front, and it (may) handle hellishly. TT bikes fix this by having the front centre further forwards and shortening the seat stays/drawing in the rear wheel as much as they can.
Next consider the front. Your hands on the hoods - now imagine clip ons - you moved them a lot further forward - that doesn't work unless you're after a superman impression. It's compensated to some amount by moving the seat, but you probably want a much shorter stem. Then the head tube is possibly too tall.. you can work around that with a negative stem perhaps.
Admittedly I'm as flexible as a concrete block, but trying to get 'aero' on my roadbike didn't work at all well for me. Moving to a TT frame (an old 'classic' P2) made a world of difference.
ETA: You've already alluded to the differences. Try shoving the saddle forwards (and it will need to rise a bit to compensate), fitting a short stem (I ran a MTB style very close coupled one - 40 or 50mm from memory), and playing from there. That'll shorten the cockpit, and you can play with height.
Edited by upsidedownmark on Thursday 6th October 09:45
NatAsp said:
what gain do you get simply from a TT frame and the ability to use bars without compromise, all other things being equal?
My TT bike vs road bike (allow round tube), both with same body positions, wheels, clothings etc have a CdA difference equivalent to about 10 seconds in a 10 mile TTThe position it allows me to get in makes around 2 minutes difference
Depending on your current setup Gruffy, there are a few options for mounting the aerobars below the base bar which allows the pads to be mounted around 25mm lower. If the lack of reach is because your saddle is too far back then a setback seatpost used in reverse can help this, otherwise a shorter negative stem.
Plenty of people do fast times on road bikes. It won't hold you back in itself, it's just about whether you can get a sustainable and aerodynamic riding position on it, and whether the bits that you'd need to buy to achieve it would cost less than buying a cheap TT bike without the compromises converting a road bike brings.
I've got some Profile Designs V4+ clip-ons installed. The pads sit nice and low on the handlebars and the extensions mount underneath them. I moved the saddle forward and tipped it down a degree. I could probably drop it another degree and nudge it forward another 5-10mm though. There's 20mm of headset spacers which I haven't played with yet. The stem is 110mm so there's options there.
I don't want to go crazy because I still want to use it as a road bike too and I'm conscious that it'll never be as quick as a TT bike anyway. I realise I'll need/want a proper TT bike if I'm going to take it seriously but I guess my question is: am I pissing in the wind trying to achieve anything on an adapted road bike in the meantime? If I'm going to be giving away >10% against others then I think I'd struggle to stay motivated once the novelty of a new discipline has worn off.
The plan might be to look at some filthy-deep wheels and/or a disc first. I can use those on the Aeroad and then when I do manage to get a TT frame I'll already have wheels for it.
I don't want to go crazy because I still want to use it as a road bike too and I'm conscious that it'll never be as quick as a TT bike anyway. I realise I'll need/want a proper TT bike if I'm going to take it seriously but I guess my question is: am I pissing in the wind trying to achieve anything on an adapted road bike in the meantime? If I'm going to be giving away >10% against others then I think I'd struggle to stay motivated once the novelty of a new discipline has worn off.
The plan might be to look at some filthy-deep wheels and/or a disc first. I can use those on the Aeroad and then when I do manage to get a TT frame I'll already have wheels for it.
I think you can get a reasonable position on a road bike - I ride a cervelo s2 to some OK times in that set up. The main issue IMO being that most people should size down on a TT bike from road so you will give up a fair bit most likely.
But it's a race against yourself and the clock. Cat 3 ability riders don't often win opens so it shouldn't be too much of an issue.
But it's a race against yourself and the clock. Cat 3 ability riders don't often win opens so it shouldn't be too much of an issue.
okgo said:
I think you can get a reasonable position on a road bike - I ride a cervelo s2 to some OK times in that set up. The main issue IMO being that most people should size down on a TT bike from road so you will give up a fair bit most likely.
But it's a race against yourself and the clock. Cat 3 ability riders don't often win opens so it shouldn't be too much of an issue.
I'm too old (for a noob) to be thinking of winning opens in any case. Sounds like the difference could be small enough to tolerate and still large enough to have a credible excuse when I underperform. Ideal then.But it's a race against yourself and the clock. Cat 3 ability riders don't often win opens so it shouldn't be too much of an issue.
okgo said:
I think you can get a reasonable position on a road bike - I ride a cervelo s2 to some OK times in that set up. The main issue IMO being that most people should size down on a TT bike from road so you will give up a fair bit most likely.
Just to add (and I'm sure OKGO knows): The S2 (along with all S-series Cervelos) was specifically designed to be a "double duty bike", as it has a reversible seatpost with geometry intended for TT purposes (i.e. the handling still works well when in the TT position). I believe the Kestrel Talon was also designed as a changeable Road/TT bike. There may be others too.
The Felt AR has a reversible seat post, changes the seat tube geometry quite significantly.
I've tried it on the turbo and so whilst I can't vouch for any aero improvement, the change in hip angle helps get power down "differently" - feels more like running to me actually.
From what I've read, this is one of the big benefits of a TT geometry but a flipped seat post would help significantly
I've tried it on the turbo and so whilst I can't vouch for any aero improvement, the change in hip angle helps get power down "differently" - feels more like running to me actually.
From what I've read, this is one of the big benefits of a TT geometry but a flipped seat post would help significantly
Jacobyte said:
okgo said:
I think you can get a reasonable position on a road bike - I ride a cervelo s2 to some OK times in that set up. The main issue IMO being that most people should size down on a TT bike from road so you will give up a fair bit most likely.
Just to add (and I'm sure OKGO knows): The S2 (along with all S-series Cervelos) was specifically designed to be a "double duty bike", as it has a reversible seatpost with geometry intended for TT purposes (i.e. the handling still works well when in the TT position). I believe the Kestrel Talon was also designed as a changeable Road/TT bike. There may be others too.
Hmm. pretty sure none of the S series seatposts are 'reversible' per-se; the seat post/tube is a teardrop shape - looking at a 2015 right now, and mate has a 2013 s3.
What they do apparently allow is fitting of a 2 position post like many of the TT bikes come with - it has 2 holes for the seatclamp at the top rather than just one, allowing you do fit the clamp futher forward.
What they do apparently allow is fitting of a 2 position post like many of the TT bikes come with - it has 2 holes for the seatclamp at the top rather than just one, allowing you do fit the clamp futher forward.
upsidedownmark said:
Fair enough, but the post I replied to said reversible. It ain't 
Yes it is - the photo above is of a more recent S-series seat post. The older ones have a reversible seatpost head that fits into the aerodynamic seat post.
Not my bike, but similar to this, I have two seatpost heads and two saddles, so that I can swap them round really quickly without having to set up the saddle each time:
http://smg.photobucket.com/user/campled/media/Cerv...
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