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Road vs TT bike

Posted: Sun Feb 03, 2019 1:48 am
by mereli97
Have a race coming up with an 8 mile TT stage. You can ride your road bike (no aero gear) or a full TT set up. If you use a TT set up, you will have a 45 second handicap. Which should I use? Some details:
  • My TT set up includes disc wheel, shoe covers, tear drop TT helmet

    Road bike is a very aero carbon frame, 35mm carbon wheels, aero road helmet

    Skinsuit is allowed on both set ups

    Course is relatively flat, 8 mile out and back course

    On a TT bike, my time is around 20 minutes, 24.3 mph

Road vs TT bike

Posted: Sun Feb 03, 2019 1:48 am
by Weenie

Re: Road vs TT bike

Posted: Sun Feb 03, 2019 2:16 am
by none
Is the time trial course in hilly terrain?
Many twists & turns?
Narrow rolling hills?
or just open, out & back, flat surface against the wind?

Re: Road vs TT bike

Posted: Sun Feb 03, 2019 4:51 am
by Miller
TT bike.

Re: Road vs TT bike

Posted: Sun Feb 03, 2019 8:38 am
by Jugi
Rough calculations:

Handicap per mile: >5 seconds and per km: >3 seconds

If you can push 40km/h or 25mph on the road bike on this course, to overcome the handicap you'd have to go 41,4km/h or 25,9mph on the TT bike.

I'd say it depends a lot on the course, conditions and how dialed in you are on your TT bike. If it is a typical TT course (straight, not much ascending) I would definetly go with the TT bike. If it is more undulating and/or technical or conditions are far from ideal (gusty crosswinds etc.) I would seriously consider the road bike.

If you are aiming for an average speed considerably more than 24-26mph ballpark, the TT bike has more of an edge over the road bike. As speeds increase aerodynamic drag increases exponentially.

Re: Road vs TT bike

Posted: Sun Feb 03, 2019 5:37 pm
by ParisCarbon
We have an 11.3km or roughly 7 mile loop we do TTs on... In general park is very windy, 1 lap gives a little over 100 feet elevation only, but the one "hill" in the park is always into a significant headwind (30-50kmh) so it makes it 3 times harder than it should be, and there is no equal downhill on the otherside, there is some very slight decline through out the rest of the lap to make up for it, but usually you are fighting wind ... On my Tarmac SL5 with Roval 50 wheels, vs my Shiv TT with 40mm wheels, I am generally about 45+ seconds faster on the TT bike (this is no aero helmet, skinsuit etc) If I go full disc, trispoke, and gear can gain significantly more pending conditions..