Bestbikesplit - help a newbie?


TrainerRoad (podcast and forum) signposted me to using Bestbikesplt when racing TT’s. I love being able to use a power plan as a guide to laying down as much power as I can.

Can someone help to guide me in respect of where I am going wrong in my workflow with this or if I have a fundamental flaw in my expectations of the software.

I am using BBS to produce power intervals for TT races. All on tarmac in the UK.
I have weighed my bike, my clothing and updated my bike settings for actual gear specs being used.
I upload the course, then update the weather as close as I can to leaving for the event.

Usually I exectute the power plan to the letter. I’m generally pleased with this aspect and achieve the intended IF, VI, NP and AP.

Then, I analyse the actual Cda and Avg Yaw (via race analytics) and find that they are way off from the original plan - although often the time is not. I then use the widget at the foot of Race Analytics to update the Bike for the new Cda Race and Cda Climb. I then get a race result which almost matches the actual result. I then use these new numbers to plan future events.

I feel like I am bodging it. I feel like I am reverse engineering the actual settings to make the ‘plan’ work, after the event. Should I be changing the bike Cda after every event?

I am not an engineer and not scientifically minded and realise that this may be as good as it gets, but I hear people talk about their estimated Cda with some certainty and mine is honestly all over the shop which makes it difficult to establish whether any changes to bike / equipment or rider setup are helping?

Any help gratefully received :slight_smile:

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Calculating CdA and Crr from a race is still a VERY inexact science. If there happened to be trees blocking your cross-tailwind or the you pumped your tires up too high can all change these variables. The best thing I believe you can do if you are racing the same course each time is to be very precise on your tire pressure, and then try to only compare races with similar wind profiles. Even then your absolute CdA will still likely be inaccurate, but relatively you should get a good idea of what is more aero in terms of setup.

Outside of a race, using the “Chung Method” (Your Power Meter is the Best Wind Tunnel Available) is probably the best way to do A-B-A-B testing for aero and is IMO much better than a race scenario since you can do the A-B-A-B test all in the same day. But it takes time and practice to get just right.

At the end of the day, BBS is great for power plans and giving your a rough estimate of your race time, but it’s a very muddy science at best.


Thanks so much for taking the time to reply - all makes perfect sense and the link is realy helpful - THANK YOU :smile:

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