What’s the best practice of category selection for kids joining group rides and races, based on their auto calculated FTP or FTP test results, and w/kg.
My kids are under 45kg, but have correct weight in settings.
I read somewhere that they should race down a single Category. Eg If w/kg would be Cat B, ride in Cat C.
Not sure if that was on a FB Riders/Racers group post, or in a forum or just hearsay. Couldn’t find an official Zwift response on this.
My son recently had his FTP increased after a race he did in Tour of Watopia Stage 1. Sometimes the W/kg looks high because the kids get dropped and pushing the wind in no-mans land does such, as they can’t hold the mental starts and fast pace after the first 10 mins.
Great result for him, and no doubt people must have seen his average Watts was much lower than those around him, obviously he’s a lot smaller 
Would be nice to know.
Bear in mind, no HRM and no account on ZP/Strava, this is purely for kids to join a ride/race and enjoy it.
I would say for Races he should be it the correct Cat according to his FTP.
For group rides he should drop at least one but if that is still to fast drop another one, group rides is supposed to be fun and he should be in Z2 (the blue one) with a bit of green an yellow now and then.
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Thanks Gerrie - helpful advice.
Wow, his average in the Cat C race was 3.9w/kg. Will have to get him into the B’s for the races.
Won’t be long and he’ll be racing with me in the A’s!!! Can’t wait for that moment when I get dropped 
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I like Zwiftpower.com’s way of making Cats. Based on meeting a wkg and min FTP number.
See table in top post.
C Cat is over 2.5wkg and over 150W.
B Cat is over 3.2wkg and over 200W
Thus makes is so that lighter riders that make less power are not blown away and I would apply to to the youth guys that are very light.
So if you are 3.8wkg at 45kg that’s a 171W FTP. I would go with the C group.
Just my 0.02.
That’s useful thanks.
His FTP got upgraded to 169w after the race, so with this approach, he’d still be in the C’s instead of B’s, even if his average power was 3.9wkg then because his threshold power isn’t high enough.
Yes, at 169W it will be very difficult just to sit in on on the flats with the B’s quite often. I would guess many of the B group are in the 280-320W FTP (70-80kg riders). That is a ton of power to give up.
I have no idea how junior do peak sprint power wise either… I would also guess that he would be blown out of the water every time in a sprint finish in the B’s. Those are some long hard powerful finishes that are highly contested in B’s.
Perhaps if you are doing a big climb race like AdZ then the wkg become the deciding factor and the B Cat may be best. All other rolling and flat races C Cat.
On a side note as a low end C rider I would have no issue with a low power junior at 3.9wkg racing in the C’s as you describe.
I checked a few sprint finishes, son hit 349-389w, so up to 9w/kg. Agree with the flats, it’s where the youngsters get dropped after a long period as it’s normally above threshold for such a long time, also rolling courses break the pack and they can’t stick with the group.
Impressed he’s hit level 15 already, with 1,300km and 21,000m elevation 
Less than 400W peak power means he will have just about no chance at winning a sprint in Cat B ever. I would stand by what I said earlier, Cat C for all rolling and flat races and B only for big long mountain stages… AdZ type stuff. For that matter I always push more than 1000W if it is down to any kind of sprint and have peaked at 1550 before and I just got out of Cat D about a week ago. Now I am mid pack in the C races. I am always confident in a sprint, but getting to the sprint with the lead pack is terribly difficult for me at times.
Yep, you are right there. All in good time, he’ll just get bigger and stronger. Thanks for your thoughts.
I average over 4 wkg in my races, but normally near the back of Cat A Zwift Power results. Don’t have the sprint legs, maybe 1100-1200 max, and the hills break me almost every time. Good to stay in lead pack until it goes up Then find myself pushing the wind solo in no mans land normally for half a race.
I don’t agree with suggesting different Categories for different types of races. If everyone pic categories that way then no honest rider will stand a change.
If he is good at climbing then he should pick climbing races if winning is the aim.
We all have our weak points.
I know the w/kg categories is actually weight classes, but that is the rules we have to live buy until we get ranking.