Dilemma; disc on a road bike for TT ?

Back by popular demand, the general all-things Road forum!

Moderator: robbosmans

Post Reply
stang1
Posts: 142
Joined: Mon Jan 30, 2012 8:57 am

by stang1

Hi guys, wanting/hoping for some serious input into this, thinking about doing some TT events but having 3 bikes ( 2 road and 1 TT ) is out of the option. What I am thinking of is selling one of road bikes for a s5/s3 and having it setup aggressive to tackle these events . I have had TT bikes before but always ended up selling them for a road bike, however that said , selling the road bike for another TT is definitely possible as well. I will be getting a disc, but my question comes down to how close will a road bike setup mimic a TT bike ? I know watts = watts etc, but I am hoping people with more experience on this issue can assist . Is it similar ?

User avatar
53x12
Posts: 3708
Joined: Fri Sep 15, 2006 6:02 am
Location: On the bike

by 53x12

The top aero road frames are up there in terms of low CdA compared to some of the top TT frames. Specialized has said that their Venge ViAS is faster than their Shiv frame. So frame CdA wise, you won't lose too much going with a top end aero road frame.

The issue lies in fit. Can you get low enough and comfortable enough on a road frame? Is the handling of whatever road frame you pick going to be affected with much of your weight now leaning forward over the front wheel. Some road bikes geometry is suited more for this than others. I think it all comes down to whether you think you can get the setup you want on the road bike. If you can, go that route. With Di2, it is very easy to swap from a road setup to a TT setup on the same bike. Take off the brake cables, unplug Di2, screw off your road bars, throw on your TT bar, reconnect Di2 and reinstall the brake cables. Once you get proficient, you could have this down to a 10-15 min job to swap between the two.
"Marginal gains are the only gains when all that's left to gain is in the margins."

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



BikeAnon
Posts: 399
Joined: Sun Mar 02, 2014 6:36 pm
Location: NY USA

by BikeAnon

What are your racing goals for the season? What have been your results in the past?

As you know, in TTs, position is super important. Typically, you can't get close to a TT position with a road frame that fits you properly.

If you're not focused on TT results (or a triathlete), there's nothing wrong with using a road bike with some aero bars, and maybe a swappable seatpost. You can't definitely do "the best you can do" for that setup. But weaker riders will beat you.

How many TTs (or omniums with TTs) will you enter, where podiums are in reach, and matter to you?

allencanna
Posts: 29
Joined: Sat Feb 28, 2015 11:33 pm

by allencanna

there will be a 1-2 miles/hour different between road and tt bike.
if they are all be ridding comfortable.

stang1
Posts: 142
Joined: Mon Jan 30, 2012 8:57 am

by stang1

Thanks 53x12, I ride a r3 with a 0 setback seatpost, -17 120mm stem and classic drops. Like you mentioned, riding I was comfortable with the r3 in that setup and with leaning over the bike as well sitting on the nose, but definitely agree with finding a bike that suits more towards that positioning fit you mentioned. Do you have any recommendations ?

@BikeAnon, I've dabbled into TTs but have not yield much results due to procrastination of racing , but this year I've committed myself to do Abit more than just recreational and will be looking to target some specific events like 20/40km TT events . I suppose in a way, I just want to identify my next purchase .

mimason
Posts: 654
Joined: Tue Feb 24, 2009 11:43 pm
Location: Florida

by mimason

If possible just buy an inexpensive TT bike. I sold my old "2008" Cervelo P2 for around 1200 to a friend. That bike was stupid fast and I beat the crap out of guys on P5s. Sink $1500 or less for a used Tri geek's old stuff and get an aggressive TT fit....and add good wheels, tt helmet and skin suit to the mix. If you are running -17 stem on a cervelo R3 you sound like you are already pretty flexible. Just get aero in a decent used TT bike and suffer like hell. Good luck.

User avatar
53x12
Posts: 3708
Joined: Fri Sep 15, 2006 6:02 am
Location: On the bike

by 53x12

stang1 wrote:Thanks 53x12, I ride a r3 with a 0 setback seatpost, -17 120mm stem and classic drops. Like you mentioned, riding I was comfortable with the r3 in that setup and with leaning over the bike as well sitting on the nose, but definitely agree with finding a bike that suits more towards that positioning fit you mentioned. Do you have any recommendations ?

@BikeAnon, I've dabbled into TTs but have not yield much results due to procrastination of racing , but this year I've committed myself to do Abit more than just recreational and will be looking to target some specific events like 20/40km TT events . I suppose in a way, I just want to identify my next purchase .



I think the S5/S3 are good options to consider. Same with the Felt AR if you want to stay with an aero road bike route. One thing to consider is that a true TT bike will give you horizontal dropouts. So will be better when fitting your disc to the bike. You could look at a used TT frame/bike. Could get some nice value there.
"Marginal gains are the only gains when all that's left to gain is in the margins."

User avatar
Calnago
In Memoriam
Posts: 8612
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

Curious as to why a "true TT" bike would give you horizontal dropouts. Why? It doesn't make fitting a disc easier, or any other wheel for that matter. It's not a single speed with no derailleur where you have to accommodate different cogs by moving the wheel horizontally to tension or slacken the chain dependent on the cog you are using. So why on a TT bike? My P3 has horizontal dropouts and I think they're a pain in the ass with a geared bike and a derailleur.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

stang1
Posts: 142
Joined: Mon Jan 30, 2012 8:57 am

by stang1

Calnago wrote:Curious as to why a "true TT" bike would give you horizontal dropouts. Why? It doesn't make fitting a disc easier, or any other wheel for that matter. It's not a single speed with no derailleur where you have to accommodate different cogs by moving the wheel horizontally to tension or slacken the chain dependent on the cog you are using. So why on a TT bike? My P3 has horizontal dropouts and I think they're a pain in the ass with a geared bike and a derailleur.


That.. :smartass: is one of the reasons I think I moved on my TT, it's a pita to move wheels in and out of it, when moving it from trainers to wheels vice versa. Can a disc be used on a road drop out ? Any big no no's with disc on road dropouts ?

spdntrxi
Posts: 5782
Joined: Sat Jul 20, 2013 6:11 pm

by spdntrxi

I thought the horizontal dropouts aid in tucking your wheel up close to the seat tube... Aero maybe.


Sent from my iPhone using Tapatalk
2024 BMC TeamMachine R Building
2018 BMC TImeMachine Road
2002 Moots Compact-SL- getting aero look makeover
2019 Parlee Z0XD - "classified"
2023 Pivot E-Vault - completed project, full Xplr package

User avatar
53x12
Posts: 3708
Joined: Fri Sep 15, 2006 6:02 am
Location: On the bike

by 53x12

Calnago wrote:Curious as to why a "true TT" bike would give you horizontal dropouts. Why? It doesn't make fitting a disc easier, or any other wheel for that matter. It's not a single speed with no derailleur where you have to accommodate different cogs by moving the wheel horizontally to tension or slacken the chain dependent on the cog you are using. So why on a TT bike? My P3 has horizontal dropouts and I think they're a pain in the ass with a geared bike and a derailleur.


Because people run different size rear tires, with a horizontal drop out it allows you to get your rear wheel as close to the rear wheel cutout as possible. It is not about fitting being easier. It is about making it the best fit possible.

That is why TT bikes have adjuster screws like this, to dial in your rear wheel as close as possible based on your tire size being used with the TT frame:


Image


Image


Horizontal dropouts = allows rider to tailor it exactly for their setup.

Vertical dropouts = one size fits all and not as efficient.

Remember you want the wheel as close as possible, but still need to pass that credit card between the cutout and the rear wheel.


Next, is the fairing rule
(UCI rule 1.3.024), which states that there should
be no fairing that will inhibit an object such as a
credit card from passing between the frame and
the wheel (this is targeting wheel cut outs). In
figure 2 the straight line is the "credit card" like
object, and the top would be the seat tube and
the bottom arc being the leading edge of the rear
wheel (lower diagram to the right).


https://s3.amazonaws.com/USACWeb/forms/ ... ations.pdf
"Marginal gains are the only gains when all that's left to gain is in the margins."

User avatar
Calnago
In Memoriam
Posts: 8612
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

Yes, ok. Makes sense for different tire sizes. I guess I misinterpreted your earlier statement saying "it will be better when fitting your disc to the bike".
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

cyclenutnz
Posts: 854
Joined: Tue Jul 18, 2006 5:18 am
Location: Cambridge, New Zealand
Contact:

by cyclenutnz

Main issues with going for tt setup on road bike:
-often not able to get into optimal position
- if you can get there it's likely to make the handling a bit scary with so much weight on the front wheel

If you're looking at spending money on TT (buying a disc) I'd always advise a TT bike as first port of call. Hunting out a P2SL (ally) frame that fits properly is a cheap way of making it easy to get in a good position. Position is everything for TT, equipment is just a nice to have.

junchen
Posts: 348
Joined: Fri Jun 12, 2015 6:21 pm

by junchen

cyclenutnz wrote:Main issues with going for tt setup on road bike:
-often not able to get into optimal position
- if you can get there it's likely to make the handling a bit scary with so much weight on the front wheel

If you're looking at spending money on TT (buying a disc) I'd always advise a TT bike as first port of call. Hunting out a P2SL (ally) frame that fits properly is a cheap way of making it easy to get in a good position. Position is everything for TT, equipment is just a nice to have.

For what you mentioned above about position being the most important - does it apply to triathlon as much as TT?


Sent from my SM-G920I using Tapatalk

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



mimason
Posts: 654
Joined: Tue Feb 24, 2009 11:43 pm
Location: Florida

by mimason

^YES. Tri setup is important in bike fit to position yourself to save muscle groups in your legs used for the run. When I was doing TTs only we would set up the bike for max bike performance which was for me to utilize more glutes with the saddle a little further back...for Tris we would adjust forward more to save the legs.

I won't get into more specifics but Slowtwitch has a lot of information that you may find helpful.

Post Reply