TT bike on a road frame [build project]

Discuss light weight issues concerning road bikes & parts.
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skidrrr
Posts: 71
Joined: Fri Jun 29, 2018 12:25 pm
Location: Moldova

by skidrrr

I always had a thing on TT bikes but I can't afford one. At the same time I have a good unused road bike frame. It is extra small and realitvetely aero because of internal routing. And I'm thinking about building a TT rig based on it. Like installing TT handle bar and tt shifters, right?
Do you think it is a bad idea? If so please tell me why

by Weenie


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VTR1000SP2
Posts: 779
Joined: Tue Nov 05, 2013 8:21 pm

by VTR1000SP2

I wouldn’t do it.

A nicely built TT bike looks like a weapon, a road bike built for TT looks... confused.


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wheelsONfire
Posts: 2953
Joined: Mon Jul 07, 2014 8:15 am
Location: NorthEU

by wheelsONfire

With the thing in mind, you can't afford a TT bike, it's either this or nothing i guess?
What would it cost you to build this one to try it out?

Or perhaps
https://www.planetx.co.uk/c/q/bikes/tt- ... bikes/exo3
Bikes:

Ax Lightness Vial EVO Race (2018.12.21)
viewtopic.php?f=10&t=156137
Paduano Racing Fidia (kind of shelved)
Open *UP* (2016.04.14)


Ex bike; Vial EVO D

jones1991
Posts: 16
Joined: Mon Oct 15, 2018 2:17 pm

by jones1991

mistake

morganb
Posts: 667
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

The geometry is so different that you won't be able to achieve a proper TT fit and will have terrible handling. Look at the seat angle on any modern time trial bike compared to a road bike in the same size. If you are set on building one, used, high end frames can be had cheap from tri groups.

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skidrrr
Posts: 71
Joined: Fri Jun 29, 2018 12:25 pm
Location: Moldova

by skidrrr

Alright I get it :) But can I add something?

I have limited budget and I want to build a Campagnolo TT bike. This season I can get a group and then install it on the road frame. Just a temporary solution before I can get a real TT frame. This is extra step will cost me about $150 but save at least 1k.

What I'm hoping to get is a slight improvement in aero performance compared to clip-on bars. Plus I can fit myself more agresivly by lowering stack.
Does it still sounds like a bad idea to you in this perspective?

alcatraz
Posts: 2208
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

I'm an amateur but...

I used to ride one. The trick to getting into a similar position is a seatpost that can set the seat forward "forward setback", and an ISM split nose saddle (these saddles allow to sit much more forward than regular saddles).

For the bars you need something that puts the aero bars higher than the base bar. Otherwise the transition is too big and you will have extreme difficulty to switch between. (If you're not in the aero position you gain nothing).

Another thing I wished I'd known was that my elbows should be on the pads and under my shoulders. Not in front of them. You should not be tense to try and hold the position, but relaxed and have skeletal support. You should be resting your upper body on the pads. You think you are by trying it quick but if you ride hard for 2 hours over bumps, you will be tired fast if it's not perfect.

Later if you decide to get a tt frame you can reuse basebar/shifters/brakelevers/seat.

Short crank arm crank is very useful. 5mm shorter than your road length is a good starting point.

What you will not have is high speed stability like a real tt frame, so you won't win any races and you might soil your underwear riding in the aero position. Nervous steering, crosswind sensitive, front wheel heavy.

morganb
Posts: 667
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

skidrrr wrote:
Wed Jan 23, 2019 2:33 pm
Alright I get it :) But can I add something?

I have limited budget and I want to build a Campagnolo TT bike. This season I can get a group and then install it on the road frame. Just a temporary solution before I can get a real TT frame. This is extra step will cost me about $150 but save at least 1k.

What I'm hoping to get is a slight improvement in aero performance compared to clip-on bars. Plus I can fit myself more agresivly by lowering stack.
Does it still sounds like a bad idea to you in this perspective?
Yes because the handling will be poor and more likely than not you will be adapting to an inefficient TT position. There is more to being aero than being low. I have a flat back on a TT bike with slightly less drop than my road bike but much longer reach and a much more forward position. If I was to have that amount of reach on a road bike with a TT bar, I would be so far over the front the bike would be totally unbalanced and near unrideable.

none
Posts: 148
Joined: Mon Dec 17, 2018 11:29 pm

by none

^^^
TT riding position differs from person to person, some like to be stretched out, some like to be hunched over be as compact as possible.

Seems like if you are looking for a smaller road frame to use as your TT bike, you like to be compact in your TT efforts.

Sometimes, being compact can restrict your breathing, which would affect your riding performance.

Also consider how often and the distance of TT you plan to participate, usually the longer the distance you want to be more neutral in riding position.

I think it's a good idea to start with a road frame that's 1cm or 2cm smaller than your regular road bike, going too small might not serve the purpose.
Shorter crankarms is a good suggestion, smaller circle to pedal action, likely allow smoother pedaling especially when compacted into aero riding position.

audiojan
Posts: 827
Joined: Fri Jan 27, 2006 1:38 pm
Location: New Hampshire

by audiojan

More than likely you'd be slower than you would be on a well fitting TT bike. As mentioned the position and therefore weight balance is different. Trying to "shoe horn" yourself into that position on a road bike will very likely be quite unstable and robbing you of precious energy and speed.

It can end up being a giant waste of money...
"Suddenly the thought struck me; my floor is someone elses ceiling" - Nils Ferlin

jones1991
Posts: 16
Joined: Mon Oct 15, 2018 2:17 pm

by jones1991

like people have said the geometry is so different you wouldnt get a good position, i bought a second hand felt b2 for my first couple of seasons, cost me £250 for the frameset and i got down to 19:20 for a 10 mile TT on that before i upgraded to something better

dont fall into the thinking that lower is more aero too, i dont have much of a drop between my saddle and tt pads, i run a 837mm saddle height too, my bars are rather high

GothicCastle
Posts: 234
Joined: Mon Jul 04, 2016 1:52 am

by GothicCastle

skidrrr wrote:
Wed Jan 23, 2019 2:33 pm
What I'm hoping to get is a slight improvement in aero performance compared to clip-on bars. Plus I can fit myself more agresivly by lowering stack.
On a TT/tri bike, you are tying to reduce frontal area, so getting narrow is often more important than getting low. You can affect airflow by getting lower, but that is difficult to assess by eye; you want time in a wind tunnel or some careful testing in a velodrome to understand the effect on your cda. Dropping stack can also reduce your power output, so you really want to go about this systematically.

Road and TT geometries are somewhat different. You could get some aero bars and reverse your seatpost to approximate a TT position, but having that much weight over the front of a road bike can really change how it handles.

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skidrrr
Posts: 71
Joined: Fri Jun 29, 2018 12:25 pm
Location: Moldova

by skidrrr

Handling is what I'm most afraid of and it's the biggest reason why I'm thinking to back off.

I am preparing for the national masters championship (Moldova). This is a two-day event and the first day is a TT, then group race. Both days are important to me and therefore I practically do not change my road bike. I just install clip-on bars as is. I did a Guru fit on the road bike and that's why I'm trying to avoid altering my position.

In my mind a separate half-tt half-road bike will allow me to play a bit more with my postion. I feel like I can go lower even though I understand that it can limit my breathing and doesn't necessarely mean better aero. But I do have a power meter so I can test my efforts and see how it goes.

Do you know good numbers in terms of weighting balance and trail for the TT bikes? On my road bike after Guru Fit I have 45/55 weigth balance on hoods and 63mm trail

by Weenie


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