How much faster is a TT bike than a relaxed road bike geometry?

General cycling advice ( NOT technical ! )
Post Reply
martinn
Posts: 421
Joined: 1 Dec 2012, 8:20pm

How much faster is a TT bike than a relaxed road bike geometry?

Post by martinn »

HI all,

I have been set a challenge by a work colleague, to take part in a triathlon relay, with myself doing the riding bit.
its a very flat course in comparison to what I normally ride, over 90KM
He has set me a time, which works out at an average of 35Km/h, which he rode it a year or two ago. I am generally significantly faster on a bike than this individual, when I have gone out riding with him, especially up any incline. I do audax and the fastest I have every done a 200 is 7hrs and 25mins (A DIY), i only stopped briefly once.
When commuting on Fixed I am happiest cruising along around the 29-30Km/h mark. (18X48 or 70" gear)

Having never been on a TT bike, how much faster once acclimatised to the position would I be? or like most things, "its a bit more complicated than that"? (there is a local 10 mile TT that runs (Ran) near me on a weekday evening, so I could use that for training)
What should I look for in a secondhand TT bike, anything different? (I cant borrow my work colleagues, as he is about 3" shorter than I am)

If I did this challenge i have over a year to prepare.

Many thanks

Martin
User avatar
squeaker
Posts: 4112
Joined: 12 Jan 2007, 11:43pm
Location: Sussex

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by squeaker »

Here's a start (the data is rather old now) but I think you are asking the wrong people ;)
"42"
robc02
Posts: 1824
Joined: 23 Apr 2009, 7:12pm
Location: Stafford

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by robc02 »

For me the difference over 10 miles on a flattish course was about one minute. At the time, on that course, I was able to do about 22.45ish on the TT bike and about 23.45ish on a road bike.

This all depends on your riding position. While I was able to ride with a near horizontal back on both bikes, I was probably a touch lower and much narrower (arms in on the tri-bars) on the TT bike. To enable the lower position my saddle position was a bit further forward - maybe 10 -15mm - so not as much as some have theirs.The new riding position took a bit of get used to initially, and evolved over time. Eventually it was pretty comfortable and much easier to hold an aero position than on my road bike.

I would suggest that you get some tri-bars to start with and see how you get on with them on a road bike. If you go for a specialist TT bike be aware that seat tube angles can vary greatly between models, and this is critical in getting the right TT position. You can make adjustments with lay back/forward seat posts of course, but even this can be difficult in some cases.

Good luck, you should have great fun .... but remember, it can be addictive!
robc02
Posts: 1824
Joined: 23 Apr 2009, 7:12pm
Location: Stafford

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by robc02 »

squeaker wrote:............. but I think you are asking the wrong people ;)


Oh, I don't know .... there a quite a few ex-TTers on here - some more recently ex than others. (I have now just about got to the position where I think I have probably retired rather than "am taking a bit of a break").
Marcus Aurelius
Posts: 1903
Joined: 1 Feb 2018, 10:20am

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by Marcus Aurelius »

It depends on the engine, and route, and conditions. All things being equal, a properly fitted TT bike should be a fair bit quicker than a ‘sportive geometrically’ set up bike.
User avatar
TrevA
Posts: 3551
Joined: 1 Jun 2007, 9:12pm
Location: Nottingham

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by TrevA »

I would just fit some clip on TT bars to your normal road bike, this will give you much of the benefit of a TT bike without the cost. I find I’m 40 seconds to a minute quicker in a 10 mile TT with tribars fitted.
Sherwood CC and Notts CTC.
A cart horse trapped in the body of a man.
http://www.jogler2009.blogspot.com
Brucey
Posts: 44513
Joined: 4 Jan 2012, 6:25pm

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by Brucey »

martinn wrote:
Having never been on a TT bike, how much faster once acclimatised to the position would I be? or like most things, "its a bit more complicated than that"? (there is a local 10 mile TT that runs (Ran) near me on a weekday evening, so I could use that for training)…...


once acclimatised? That is 'if' not 'when'. Frustratingly I could make enough power to go incredibly fast, provided I adopted a suitably aero position. I could manage the position, but not whilst making full power, and not for any length of time.

In practice every time I rode a TT the position was a compromise between these things. I even tried using a bike with tribars to ride to work, hoping that I would become better accustomed to that position. It did improve matters but it wasn't completely effective. Now, I'd probably train indoors in my TT position, carefully measuring power output vs pulse rate in different positions.

On a good day I was as fast on my road bike as I was on an average day on my TT bike.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Ke1th
Posts: 100
Joined: 11 Jul 2018, 7:54pm

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by Ke1th »

I remember an article fairly recently comparing a tt bike with road equivalent. The conclusion was riding the road bike wearing an aero helmet was the most significant improvement v cost. Of course tt bike and aero helmet won the day.
mattsccm
Posts: 5101
Joined: 28 Nov 2009, 9:44pm

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by mattsccm »

I am nearly 2 minutes faster for my local 10 on my TT bike. Position mostly and I doubt mine is that refined. Bike is more aero as well, disc rear wheel deep front, TT bars etc. My mood helps as well. Depends as well on the route. Another club TT course has a half miles flat out descent with a 17% S bend that I feel happier through with fatter tyres and disc brakes than on the aero bars. Few of us are brave enough to tuck down on the extensions for the following 1/2 mile to a junction as it has a cycle path crossing, a layby and millions of squirrels etc. The corresponding up hill later is arguable either way as its longer and not so steep.
My rambling point is that there are so many variables. You could modify your road bike to a great extent. Tri bars, even a spare seat pin fitted reversed so the seat is further forward etc. A disc wheel cover from ebay converts your rear for less than 40 quid.
Aero is everything as long as you don't lose power.
martinn
Posts: 421
Joined: 1 Dec 2012, 8:20pm

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by martinn »

Thanks Guys,

So a "sensible" plan of action would be, try a set of tri bars, and see how I get on, possibly look for an areo helmet, get something set up on a turbo trainer and see where I end up
Brucey
Posts: 44513
Joined: 4 Jan 2012, 6:25pm

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by Brucey »

that sounds reasonable to me.

You can get some idea about aero drag by freewheeling repeatedly down the same hill (using different riding positions etc) and timing yourself over a distance. Such measurements contain scatter (even if taken back to back) so you need to take an average. In addition the measurements will vary from day to day. To make valid long term comparisons you need a 'control condition' which you should use to top and tail every session with.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
mattsccm
Posts: 5101
Joined: 28 Nov 2009, 9:44pm

Re: How much faster is a TT bike than a relaxed road bike geometry?

Post by mattsccm »

Get the wrong aero hat for your position and you will make things worse. There is a Facebook group dedicated to time trial positions . Still ends up with a difference of opinion of course.
Post Reply