I’ve seen the data and know a 90mm front wheel outperforms a 60mm front wheel. However, in practical terms and in the real world, how significant is this difference. Given a disc wheel (or covered rear wheel), how much faster is a 90mm front wheel compared to the 60mm wheel over 40K at say 27mph? I know yaw angles will influence the time difference, but how many seconds (in general) are we talking about?
I ask because I’m in need of an aero front wheel - most likely a HED Jet or Flo. From a straight aero viewpoint, a 90mm front wheel would be the preferred choice. However, living and racing in Colorado many of the time trial races I participate in are windy. I’ve heard differing opinions, but I’m concerned that I will be blown around too much on windy days with a 90mm front wheel; I weigh 155 lbs, and my handling skills in wind could be improved.
Apparently Macca had 808’s on his rig in the 2012 Kona ironman. Originally Jacobs had a 404 front. Macca told Jacobs there is no difference in the wind between a 404 and 808, but the 808 is faster. Jacob switched last minute to the 808 and attibutes part of his win to this advice.
At the extremes of yaw an H3 would be best, for everything in between 404 and 808 are.
and see anywhere from basically no difference at yaw angles < 10
to ~10 seconds saved per 40k if yaw angles are consistently around 10 degrees
to ~20 seconds per 40k if yaw angles are consistently around 15 degrees (pretty unlikely)
These time savings assume a perfectly flat course with no corners. I would expect typical differences to be around 5 to 15 seconds per 40k depending on how windy it is, and depending on how much you get blown around.
Only you can say how hard a 90mm front is for you to handle. I know 132lbs women who can stay locked in the aerobars on crazy windy days with a 90mm deep wheel and I known grown 180lbs cat 1 men who can’t.
I’ve heard differing opinions, but I’m concerned that I will be blown around too much on windy days with a 90mm front wheel; I weigh 155 lbs, and my handling skills in wind could be improved.
Thank you.
Michael
If you not confident this won’t be a problem, then the small time advantage is irrlevant if you have to spend a lot of energy, stress and risk of a crash because of crosswinds.
Here’s a simple test of handling confidence. In a race, do you always sit up and go to the pursuit position for corners, or do you take them most of the time in the aerobars if the surface is in good condition, not major bumps, etc.? How about a downhill high speed 35+mph sweeper with good sight lines? Sit up or stay aero? Assume dry pavement and your not passing. A good, confident bike handler stays aero, unless they have to brake or it’s a sharper corner or questionable road surface. I find most riders sit up.
I think the effects of wind on handling between a 60mm and 90mm front are overstated. I understand and appreciate the caution, but I weigh the same as you and ride a Hed Jet 9 for all race conditions and even in windy/gusty weather, I find it more than manageable. It takes some getting used to, but once you learn to relax and not over react to the wind, it becomes a non-factor outside of extreme conditions.
My suggestion is to buy the faster wheel and then learn to ride with it. Unless data exists that shows the Flo 60 or Jet 6 are faster, which I don’t know of but might exist, then usually deeper is better.
Thanks for the info. However, I’m still truly undecided. I’m tentative on fast downhills (and often on the horns), and I tend to bounce back and forth across the road in crosswinds. Though, with practice, I should be able to rectify these problems. I rode a friend’s 88mm front Chinese wheel on several occasions, including in crosswinds of 10-15 mph. While not particularly fun in the wind it was manageable.
My biggest races are the Colorado State TT and the Record Challenge in Moriarty, NM. In both instances I rode the 88mm front wheel; albeit in very little wind. No problem. These are my “A” races. It’s my “B” and “C” races earlier in the season that typically are windy, have twists and turns, and downhill sections.
So, perhaps I should go for the 90mm front wheel, practice my handling skills in the lesser races (hopefully I won’t crash) and/or use a non-aero front wheel in very windy conditions, and then hope I have the skill and little wind for my “A” races.
Then again, as a 52 year-old racer shooting for a 55 minute 40K time, perhaps 10-15 seconds shouldn’t matter too much. Though, I did miss the podium twice last year by less than 5 seconds. Hmm.
I agree. A 90mm can be handled with ease and with decent performance gains given the right technique but it takes more effort than a 60mm front reguardless of your skills. I rode a set of Aeolus9d3’s everyday for a long time and after hitting so many different wind conditions I came to the conclusion that it was slowing me down in the long haul due to seriously heavy crosswinds making it too sketchy to stay down in my aero position at certain times. A truck or bus blowing by at 50+mph as a crosswind gust of about 25-30mph hits me while i’m going 32mph was HECTIC. I’ve experienced these conditions with alot of wheels. When I switched the front wheel from 90mm to 50mm the front steering turbulence in most crosswind conditions came down to a minimum where it wasn’t sketchy to be down low in the aero position which, in my book, compensated for the insignificant increase in air drag. If conditions don’t get as crazy as 30mph crosswind gusts you should be fine with 90’s all around, and honestly 90’s all around was a pretty darn fast and fun setup. I currently run a 50mm front and disc rear every day in all conditions and the wind has gotten so crazy its pushed me off my course right onto the edge of the bike lane but I find it to be just a tad faster than my 90s still. Fun stuff!
The seconds add up. If you make good gear decisions accross the board, (5s here, 8s there, etc.), it becomes a significant advantage. This is only one factor that you may choose to balance your comfort level with the speed gains, but don’t overlook 5-10s as insignificant!
Thanks for the info. However, I’m still truly undecided. I’m tentative on fast downhills (and often on the horns), and I tend to bounce back and forth across the road in crosswinds. Though, with practice, I should be able to rectify these problems. I rode a friend’s 88mm front Chinese wheel on several occasions, including in crosswinds of 10-15 mph. While not particularly fun in the wind it was manageable.
My biggest races are the Colorado State TT and the Record Challenge in Moriarty, NM. In both instances I rode the 88mm front wheel; albeit in very little wind. No problem. These are my “A” races. It’s my “B” and “C” races earlier in the season that typically are windy, have twists and turns, and downhill sections.
So, perhaps I should go for the 90mm front wheel, practice my handling skills in the lesser races (hopefully I won’t crash) and/or use a non-aero front wheel in very windy conditions, and then hope I have the skill and little wind for my “A” races.
Then again, as a 52 year-old racer shooting for a 55 minute 40K time, perhaps 10-15 seconds shouldn’t matter too much. Though, I did miss the podium twice last year by less than 5 seconds. Hmm.
MichaelBased on the bolded above sounds like you need to get a 90 & 60, problem solved!
If ~6 seconds in a 40k is not an issue then you are right.
Note that the deep rims are best when it is really wind… which is precisely when people tend to wish they didn’t have them.
If the advantage of a 90mm is 5-10 seconds, maybe 15 seconds in windy conditions, then how much time is lost working to control a 90mm wheel vs. a 60mm wheel (assuming one stays in a tucked position). Is it a wash?
I have no idea. I ride a 82mm front and just deal with it. The 30+ mph gusts when going over 40 mph can be exciting, but I don’t know that a 60mm rim would be substantially different.
IMO if TTs are your thing, then go deep or forget about it.
