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TT pace

Posted: Fri Sep 25, 2015 11:36 am
by jules21
did a 5 x 5min session at the local velodrome on my TT bike last night.

each 5 min. session comprised 3 mins at 40 km/h and 2 mins at 42 km/h. I hit those targets for all sessions - wouldn't have made a 6th effort though - point of exhaustion.

I don't have a PM on the TT bike, but my FTP is somewhere around 300w or slightly higher. (i'm 193cm and 83kg)

am I in the ballpark? I know I'm making less power on the TT bike, but the speed seems a bit slow. the velodrome is an old concrete one (Brunswick, Melb) that is pretty rough, a bit windy, so I reckon that's knocking a bit of speed off, also I'm not in any aero kit except the TT bike (about 30mm profile training wheels).

this is about 2km/h faster than I would lap on my road bike, with similar perceived effort/HR.

Re: TT pace

Posted: Fri Sep 25, 2015 2:11 pm
by Alex Simmons/RST
Far too many unknown variables. In calm conditions it would suggest pretty ordinary aerodynamics for a TT bike set up but wind has a big impact on the power-speed equation.

Going from 40 to 42km/h would mean an increase of ~ 40-45 watts (~14% - 15% more power).

Re: TT pace

Posted: Fri Sep 25, 2015 3:38 pm
by jules21
thanks Alex. i'm no TT aerodynamics expert, but my position is relatively low. I know there's more to it than that, e.g. position of arms guiding wind around torso, but I can't imagine my position is that bad. I've been focusing on holding my position (head tilted back, facing forward, opening up the torso for breathing) which seems to help with aerodynamics and breathing.

what I suspect is that bending my body forward saps more power than it should. the reason I suspect that is I notice the same thing happening on my road bike when I get into a more aero (low) position, which does have a PM fitted.

Re: TT pace

Posted: Fri Sep 25, 2015 4:34 pm
by dalai47
Any chance of swapping the PM onto the TT bike?

Not sure I understand the head tilted back. Head higher than your back looking side on is generally bad. Usually ducking and turtling is better...

Re: TT pace

Posted: Fri Sep 25, 2015 5:53 pm
by jules21
dalai47 wrote:Any chance of swapping the PM onto the TT bike?

none - shimano HT2 PM, vs. SRAM Red / BB86 on the TT bike!

dalai47 wrote:Not sure I understand the head tilted back. Head higher than your back looking side on is generally bad. Usually ducking and turtling is better...

that's what I meant, I think. not bowing my head, staring down. so when I'm wearing the sperm helmet, it forms a nice smooth line onto my back.

Re: TT pace

Posted: Thu Oct 22, 2015 2:49 pm
by zill
Jules, you seem to train at the velodrome a lot. Do you have a trainer? If so why not train on it instead of the velodrome?

Re: TT pace

Posted: Thu Oct 22, 2015 10:25 pm
by warthog1
You mention you are quite low ag the front. Do you maintain a regular stretching routine to stay flexible?
Are you further forward on the saddle on the tt bike to open up the hip angle?
The plank also helps with a bit of core strength. They dont do tts at all where I live now so I don't ride them anymore. That used to help for me though.

Re: TT pace

Posted: Thu Oct 22, 2015 10:51 pm
by toolonglegs
Didn't realise ( or maybe forgotten ) you were such a tall guy Jules.
Lot of variables obviously but would have thought you would be able to hold more than 42 for 5 minutes "reasonably" easily on a velodrome.
Can't comment much though ... only dragged the TT bike out a couple of times this year, that was enough to tell me that it wasn't worth bothering. Run 180mm cranks and feel like I can't turn them smoothly. Probably tells me I am way stiffer than previous years and power is down as well. I lose about 10% of my power in my TT position, which I think Alex would say is huge. Still even with that loss my position must be OK as no way I could average similar speeds on my road bike.
Next year I am hoping!.

Re: TT pace

Posted: Fri Oct 23, 2015 9:15 am
by mikesbytes
Another way to think of it is to do exactly the same routine in a years time and see what difference there is. [assuming same wind, air density, equipment - none of which will be the same]