Hi,
I am looking for a Tri / TT bike and my budget dictates second hand.
If my road bike top tube length is 56cm, is that a reasonable guide for sizing of a Tri/TT bike.
Many Thanks
Second hand TT bikes
-
- Posts: 704
- Joined: Tue Jun 09, 2009 3:17 pm
- Location: Perth
Second hand TT bikes
Postby bianchi928 » Fri Dec 18, 2015 4:21 pm
Stand on my dog I cut off your head
-
- Posts: 2
- Joined: Tue May 12, 2020 10:43 pm
Re: Second hand TT bikes
Postby Travis_R01 » Tue May 12, 2020 10:49 pm
Hi,
Yes a 56cm top tube is often the best way of measuring a frame size for best fit. Best place to find second hand TT bikes is online, such sites like Facebook marketplace, eBay and Gumtree are good places to look, and the trick is to look regularly.
cheers.
Yes a 56cm top tube is often the best way of measuring a frame size for best fit. Best place to find second hand TT bikes is online, such sites like Facebook marketplace, eBay and Gumtree are good places to look, and the trick is to look regularly.
cheers.
- MattyK
- Posts: 3257
- Joined: Fri Oct 01, 2010 1:07 pm
- Location: Melbourne
Re: Second hand TT bikes
Postby MattyK » Fri May 15, 2020 1:26 pm
Short answer, no.
Get a (TT position) bike fit, get your Pad X/Y numbers, and get someone (ideally the fitter) to help translate that into a frame size.
Second point is that every frame maker uses a different frame sizing system, often with no relation to the classic seat tube length measurement.
Third, you typically want a longer frame in a TT position for stability/reducing weight on the front end, and typically a steeper seat post angle. This often messes up the top tube length number.
That said, it's probaby a good starting point to say that if you're a "large" frame in one model/brand, then "Large" would be fairly close in other brands.
Get a (TT position) bike fit, get your Pad X/Y numbers, and get someone (ideally the fitter) to help translate that into a frame size.
Second point is that every frame maker uses a different frame sizing system, often with no relation to the classic seat tube length measurement.
Third, you typically want a longer frame in a TT position for stability/reducing weight on the front end, and typically a steeper seat post angle. This often messes up the top tube length number.
That said, it's probaby a good starting point to say that if you're a "large" frame in one model/brand, then "Large" would be fairly close in other brands.
- Derny Driver
- Posts: 3039
- Joined: Wed Nov 21, 2012 12:18 pm
- Location: Wollongong
Re: Second hand TT bikes
Postby Derny Driver » Fri May 15, 2020 2:25 pm
TT bikes are often marginally smaller than road bikes.
The seat tube angle is steeper so position is more forward. And seat tube shorter.
By putting more seatpost above the frame it allows the rider to get a lower front end for aerodynamics.
Aero bars /cockpit are postioned further forward than normal flat bars or drop bars so a shorter top tube allows you to position you arms without being too stretched.
Ideally though, as MattyK said, you dont want to have heaps of weight in front of the head tube, or too long a handlebar stem. So if your road bike was say 56 square, you'd go 55 seat tube and 56 top tube for TT. The forward seat position and steeper seat tube angle will move your whole body forward anyway. A shorter top tube is not required.
But of course, TT bikes are not custom built so you really need to try them for fit.
The seat tube angle is steeper so position is more forward. And seat tube shorter.
By putting more seatpost above the frame it allows the rider to get a lower front end for aerodynamics.
Aero bars /cockpit are postioned further forward than normal flat bars or drop bars so a shorter top tube allows you to position you arms without being too stretched.
Ideally though, as MattyK said, you dont want to have heaps of weight in front of the head tube, or too long a handlebar stem. So if your road bike was say 56 square, you'd go 55 seat tube and 56 top tube for TT. The forward seat position and steeper seat tube angle will move your whole body forward anyway. A shorter top tube is not required.
But of course, TT bikes are not custom built so you really need to try them for fit.
-
- Posts: 15385
- Joined: Wed Jul 25, 2012 4:40 pm
- Location: Bendigo
Re: Second hand TT bikes
Postby warthog1 » Fri May 15, 2020 9:38 pm
They still need to comply with the nose of the saddle being 5cm behind the bottom bracket though.
Stupid rule that it is for TTs.
You need a specific saddle with a short nose to get the hips forward.
As Derny says moving forward opens the hip angle and allows a lower frontal position for better aero whilst still developing power.
Rode a 56cm effective top tube in tt and around a 57 in roadie.
Edit: (just looked up the chart and it states it was a 57 in the rear seat hole and 54 in the front which I used. Had a shortened slr t1 so I sort of fail to see the relevance of the 2 positions a bit. I run the seat at 5-5.5cm behind bb on the roadie too, but it aint shortened)
I ordered my p2c new and had to swap it for another size larger as the bike shop had me on one that was too small.
Max seat tube extension and needed a longer stem.
Yeah it would pay to try it out before buying.
Stupid rule that it is for TTs.
You need a specific saddle with a short nose to get the hips forward.
As Derny says moving forward opens the hip angle and allows a lower frontal position for better aero whilst still developing power.
Rode a 56cm effective top tube in tt and around a 57 in roadie.
Edit: (just looked up the chart and it states it was a 57 in the rear seat hole and 54 in the front which I used. Had a shortened slr t1 so I sort of fail to see the relevance of the 2 positions a bit. I run the seat at 5-5.5cm behind bb on the roadie too, but it aint shortened)
I ordered my p2c new and had to swap it for another size larger as the bike shop had me on one that was too small.
Max seat tube extension and needed a longer stem.
Yeah it would pay to try it out before buying.
Dogs are the best people
- MattyK
- Posts: 3257
- Joined: Fri Oct 01, 2010 1:07 pm
- Location: Melbourne
Re: Second hand TT bikes
Postby MattyK » Tue May 19, 2020 9:22 am
Top tube is not a number to pay attention to. If you want to compare TT/Tri frames, use the Stack and Reach numbers.
- g-boaf
- Posts: 22975
- Joined: Mon Sep 26, 2011 6:11 pm
Re: Second hand TT bikes
Postby g-boaf » Tue Jun 02, 2020 12:58 pm
When I got a Cervelo P5, we worked out the medium frame was okay. I ride also a medium frame on a Giant TCR Advanced SL1 road bike.
Garmin-Sharp people recommended that and the guy who did my bike fit did his work and we came up to the same result and were able to set up the bike with the right fit. It was comfortable enough and a pretty good position on the bike as well.
If you can find a bike fitter with an adjustable stationary bike setup, you might be able to replicate the TT bike you are interested in to see if it will work.
Garmin-Sharp people recommended that and the guy who did my bike fit did his work and we came up to the same result and were able to set up the bike with the right fit. It was comfortable enough and a pretty good position on the bike as well.
If you can find a bike fitter with an adjustable stationary bike setup, you might be able to replicate the TT bike you are interested in to see if it will work.
- twizzle
- Posts: 6405
- Joined: Wed Aug 13, 2008 11:45 am
- Location: Highlands of Wales.
Re: Second hand TT bikes
Postby twizzle » Thu Nov 10, 2022 6:40 am
Another vote for stack/reach. My "go to" for fit calculation was always Competitive Cyclist, but they don't have TT.
Grab a tape measure and try this one instead.
https://www.jensonusa.com/bike-fit-calculator
Grab a tape measure and try this one instead.
https://www.jensonusa.com/bike-fit-calculator
I ride, therefore I am. But don't ride into harm's way.
...real cyclists don't have squeaky chains...
...real cyclists don't have squeaky chains...
Jump to
- General Australian Cycling Topics
- Info / announcements
- Buying a bike / parts
- General Cycling Discussion
- The Bike Shed
- Cycling Health
- Cycling Safety and Advocacy
- Women's Cycling
- Bike & Gear Reviews
- Cycling Trade
- Stolen Bikes
- Bicycle FAQs
- The Market Place
- Member to Member Bike and Gear Sales
- Want to Buy, Group Buy, Swap
- My Bikes or Gear Elsewhere
- Serious Biking
- Audax / Randonneuring
- Retro biking
- Commuting
- MTB
- Recumbents
- Fixed Gear/ Single Speed
- Track
- Electric Bicycles
- Cyclocross and Gravel Grinding
- Dragsters / Lowriders / Cruisers
- Children's Bikes
- Cargo Bikes and Utility Cycling
- Road Racing
- Road Biking
- Training
- Time Trial
- Triathlon
- International and National Tours and Events
- Cycle Touring
- Touring Australia
- Touring Overseas
- Touring Bikes and Equipment
- Australia
- Western Australia
- New South Wales
- Queensland
- South Australia
- Victoria
- ACT
- Tasmania
- Northern Territory
- Country & Regional
Who is online
Users browsing this forum: No registered users
- All times are UTC+11:00
- Top
- Delete cookies
About the Australian Cycling Forums
The Australian Cycling Forums is a welcoming community where you can ask questions and talk about the type of bikes and cycling topics you like.
Bicycles Network Australia
Forum Information
Connect with BNA
Brought to you by Bicycles Network Australia | © 1999 - 2024 | Powered by phpBB ®
This website uses affiliate links to retail platforms including ebay, amazon, proviz and ribble.
This website uses affiliate links to retail platforms including ebay, amazon, proviz and ribble.