How accurate do people find best bike split? I consistently find that I am 15-25 minutes slower than predictions on BBS for 70.3 courses.
Is this normal?
BBS is pretty accurate, but it’s only as good as the data you feed into it.
If you are finding it more than a couple of minutes off you need to go back through all the data fields you’ve entered and look for something that’s (way) off.
I have used on courses where I have been able to race multiple times to help correlate the variables that are harder to fully ensure are accurate, and by doing that have gotten most of my bike splits to come out within 2-3% of the BBS prediction, if I don’t fall apart or have ride off plan.
When I first started using it, I did some reverse engineering after races to manipulate the variables I couldn’t know exactly to make the time match what I actually rode. Once I figured out bike configuration, it’s been consistently within 2-3 minutes for 56 or 4-5 for 112 through 35-ish races.
Usually within 1 minute, occasionally 2 minutes.
I put in a century route I like to do into best bike split, wanting to average 20mph. BBS estimated I’d have to do like 217w, but when I did it last year at 20mph I did more like 230w. BBS estimates I could do 4:45 (21mph) at 230ish watts. Anyhow, I’ve been using mywindsock and it seems a bit more accurate with estimates based on weather conditions. For example, today if I were to ride my century route at 230w, I get an estimate of 4:50 on windsock (that actually appears to be the estimate on most days, I did it in 4:56 last year). Anyhow, from my very surface level stuff, windsock seems really darn close
just editing to add on, I just looked at best bike split where I entered my last ride last year and it models 4:43 for the same course, maybe it’s missing weather stuff because I’m not a premium member but it’s definitely more ambitious with estimate compared to windsock. So I’m not gonna bank on doing 21mph but I’ll try anyway!
How accurate do people find best bike split? I consistently find that I am 15-25 minutes slower than predictions on BBS for 70.3 courses.
Is this normal?
How much elevation on those rides? If find that on flat courses it’s spooky good. For me, on courses with elevation, results have not been that great.
How accurate do people find best bike split? I consistently find that I am 15-25 minutes slower than predictions on BBS for 70.3 courses.
Is this normal?
How much elevation on those rides? If find that on flat courses it’s spooky good. For me, on courses with elevation, results have not been that great.
I have been thinking this was the case as I haven’t been able to accurate get BBS to predict my hilly races. I did Muskoka 70.3 last year (804m of elevation) and BBS predicts me in the 2:21-2:22 (308NP) area where I actually completed in 2:36:16. (317NP) I have tried adjusting for climbing speed, utilized files from hilly rides to calculate CdA but nothing has helped me bridge that gap.
BBS: https://www.bestbikesplit.com/public/207073
Alternatively a flat Olympic distance I did last year it accurately predicted within seconds of my actual time:
Actual: 1:00:21 (342 NP)
Predicted: 1:00:06 (343 NP)
BBS: https://www.bestbikesplit.com/public/212456
Would love any insight there is to understanding how I can bridge the gap between hilly and flat course predictions.
How accurate do people find best bike split? I consistently find that I am 15-25 minutes slower than predictions on BBS for 70.3 courses.
Is this normal?
How much elevation on those rides? If find that on flat courses it’s spooky good. For me, on courses with elevation, results have not been that great.
I have been thinking this was the case as I haven’t been able to accurate get BBS to predict my hilly races. I did Muskoka 70.3 last year (804m of elevation) and BBS predicts me in the 2:21-2:22 (308NP) area where I actually completed in 2:36:16. (317NP) I have tried adjusting for climbing speed, utilized files from hilly rides to calculate CdA but nothing has helped me bridge that gap.
BBS: https://www.bestbikesplit.com/public/207073
Alternatively a flat Olympic distance I did last year it accurately predicted within seconds of my actual time:
Actual: 1:00:21 (342 NP)
Predicted: 1:00:06 (343 NP)
BBS: https://www.bestbikesplit.com/public/212456
Would love any insight there is to understanding how I can bridge the gap between hilly and flat course predictions.
How is it possible to only go around 24-25 mph on that wattage on a flat course? Are you a really big person? I’ve done Olympic distance races on rolling terrain in the 55-56 min range on a bit over 300 watts.
Back to the initial question, I’ve found BBS to be eerily accurate when I do the ‘correct’ wattage in a race. In many 70.3 races the estimated time has been within a minute of what I’ve ridden.
At the recent IM WC in St. George my predicted BBS time was around 4:46 on 230 AP. I ended up being sick and had my first ever DNF that was not due to a mechanical on the bike or injury I knew I had going into the race. I only made it to mile 95 before dropping out. I finished averaging 167 watts and was absolutely smashed at that point. A few days later I finally got a positive test for Covid, so there was a logical explanation for feeling like I had nothing on race day. Plugging in the power I rode from race day into BBS gave me almost exactly the pace I rode at until my DNF - around 20 mph. So, the point is that BBS is pretty accurate if you use it correctly. Using the weather as close to race day as possible makes it as accurate as possible.
How accurate do people find best bike split? I consistently find that I am 15-25 minutes slower than predictions on BBS for 70.3 courses.
Is this normal?
How much elevation on those rides? If find that on flat courses it’s spooky good. For me, on courses with elevation, results have not been that great.
I have been thinking this was the case as I haven’t been able to accurate get BBS to predict my hilly races. I did Muskoka 70.3 last year (804m of elevation) and BBS predicts me in the 2:21-2:22 (308NP) area where I actually completed in 2:36:16. (317NP) I have tried adjusting for climbing speed, utilized files from hilly rides to calculate CdA but nothing has helped me bridge that gap.
BBS: https://www.bestbikesplit.com/public/207073
Alternatively a flat Olympic distance I did last year it accurately predicted within seconds of my actual time:
Actual: 1:00:21 (342 NP)
Predicted: 1:00:06 (343 NP)
BBS: https://www.bestbikesplit.com/public/212456
Would love any insight there is to understanding how I can bridge the gap between hilly and flat course predictions.
How is it possible to only go around 24-25 mph on that wattage on a flat course? Are you a really big person? I’ve done Olympic distance races on rolling terrain in the 55-56 min range on a bit over 300 watts.
I am 195cm and race around 107-109kg so races were raced at 2.9w/kg for the 70.3 and 3.1w/kg for the oly. That probably will make more sense now.
It’s likely the CdA needs to be worsened as it may have you staying aero longer than you actually do.
I have noticed this on some hilly courses as well, in some cases in the past BBS over-smoothed some of the shorter steeper sections. When one of the original founders Rich (me being the other) purchased BBS back from TP last year, he made some adjustments to that algorithm to allow for shorter segment lengths. There are some pros and cons to this, but one benefit should be new uploaded courses should do a bit better on punchier courses.
I have noticed this on some hilly courses as well, in some cases in the past BBS over-smoothed some of the shorter steeper sections. When one of the original founders Rich (me being the other) purchased BBS back from TP last year, he made some adjustments to that algorithm to allow for shorter segment lengths. There are some pros and cons to this, but one benefit should be new uploaded courses should do a bit better on punchier courses.
The issue I ran into in Whistler was my minimal climbing power. BBS predicted my climbing power at 180 max, never touching 200. Turns out on those climbs in my easiest gears I was putting out 220-230 minimum. Absolutely crushed me. I think BBS had me at sub 7, I wound up 8:01 and walking up the last few hills.
I have tried adjusting for climbing speed,
Does your climbing speed adjustment mirror what you actually do in races? eg I have mine set to 12mph in BBS and I never go out of aero unless I am < 12mph. If my real life action does not mirror what I put in then I start to see discrepancies. Also make sure your weight is accurate (bike weight plus full race setup weight)
I just completed the race I was looking at with 366m of elevation over 40km (so a reasonable amount of elevation).
BBS Projection: 59:09 @ 363w NP
Actual: 1:00:11 @ 355w NP
So a time I was skeptical of was actually pretty bang on.
BBS is pretty accurate, but it’s only as good as the data you feed into it.
If you are finding it more than a couple of minutes off you need to go back through all the data fields you’ve entered and look for something that’s (way) off.
Spot on. Something is amiss with the data entered by the OP.
Just for fun I signed up and entered a couple of races I have done more than once.
It was one minute faster in an Olympic and 4 minutes slow on a 70.3
I also have some inaccuracies with bbs in hilly races. I think one problem on hilly courses is that bbs calculates the power needed to maintain speed and balance the sum of resistances (air resistance, rolling resistance, gradient). This is a constant power. Now if you think you are going up a hill with say 250W and 14km/h and you come to a plateau, the equation tells you that you might be able to go 35km/h on that plateau with your 250W. In reality, if you were to keep the 250W constant, it would take you a very long time to reach that 35km/h. In reality, you have to accelerate the bike to 35km/h, and the power output for that depends a lot on the rider, so it’s different for everyone. I think the key to a good prediction is to model this erratic behaviour really well. And that’s really hard to do.