Hed 3 Front stability in breezy conditions - light rider

Triathlon Forum
1

So I’ll be racing IMW in two days, and am borrowing my friend’s Hed 3 front. I’m a light rider (137 lbs) and have had a chance to try it out a couple of times. I rode it in last year’s race in light wind conditions (5 to 10 mph) and it felt solid. This year, wind conditions are expected to be around 12 mph, with gusts of 20+ according to accuvue weather. I did a test ride last weekend along w/ my rear disk in sustained 17 mph winds and the cross wind blew me around pretty bad. For my weight, is the H3 front too much to handle in the expected race conditions? I hope to do my last test ride in similar conditions on Saturday a.m. to make my decision but my experience is limited w/ this wheel. My backup front is my deep dish training wheel (something like a deep V) which I’m comfortable on in any conditions and expect it will perform fine paired w/ the disk. Thanks.

Ben

2

I’m a little heavier, but not much. I found no difference in the side winds between my Hed 3 and the Zipp deep rims. I’d maybe consider the weight more, as there is a pretty fair amount of climbing.Also, breaking efficiency, as the downs have some tought turns at the bottom.

3

I don’t think you need to worry about the wheel and its stability. When I rode an H3, I weighed about 155 lbs and have raced it in all kinds of wind conditions up to 25-30 mph gusts with steady winds of 15 mph and didn’t have any real problems with stability.

I think a big thing with any aero wheels is understanding that the bike will blow around when hit by a 25 mph gust and not to let the movement cause you to tense up. In my opinion, that is what causes the most problems with bike handling. If you can’t ride it comfortably, then I would use the other wheel.

4

The stability in itself is not a problem – something you do have to deal with, but it’s manageable. What may be a problem is that you’re borrowing it and possibly haven’t ridden it yet. It does take some getting accustomed to for putting your full confidence (and hence power) into it. Just my $.02…

5

I’ve ridden HED3’s for years in all conditions, everyday, training and racing. You need to consider that the bike portion is very long. Which wheel you are most comfortable with is the wheel you should ride. Its a long day, you don’t need anything EXTRA to worry about, like the winds and how they will blow you around if you are not used to it. Unless you are attempting to qualify for the Big Dance, I’d stick to the wheel I’ve used the most. No need to change wheels this close to race day, it won’t make that much difference.

6

If you have a disc in back, no problemo. The trick is to have more surface area in back than in front. H3+ disc is primo. A pair of H3s is good, an H3 front with a box rim in back could be trouble.

7

The trick is to have more surface area in back than in front. H3+ disc is primo.

This makes sense, but I read a John Cobb article that said if you only had one aero wheel, the front would be the place to put it because that hits the most wind. Also I jsut found a 1993 copy of Triathlete and noticed that areo front with normal box rim back was not uncommon in the elites that year.

8

“…if you only had one aero wheel, the front would be the place to put it…”

True…but we aren’t talking about just aerodynamics in this case, but stability in a wind. Different shit calls for different stuff!! The most aero wheels are tri-spoke front and disc rear. This also is the best setup if you run a tri-spoke front in a wind due to the counter forces of the disc on the front tri-spoke when its hit by a wind.

9

I can “understand” that logic that the rear disc “balances” the front tri spoke in the handling of the bike…but what exactly is the counterforce to the wind relative to the wheels that require a disc to balance a trispoke?

If the wind effect on a wheel is the same at the front as at the back of each wheel (i.e. the side wind pushes a lateral force on any single wheel evenly, across the wheel and any place you measure the lateral force on a wheel it will be the same), then the wind effect wouldn’t nec. make the wheel turn in your hands right?

Likewise the wind wouldn’t skew the bike under the rider if the contact patches on the ground have eaual grip on the road. The wind wouldn’t cause the bike to rotate around and axis in relation to the different side forces of a disc wheel and a tri spoke.

It would seem that the main problem with a larger front side force is that it gets squirrely when its angle of attack to the wind changes, though turns and balancing corrections associated with side wind. And that the front wheel surface area relative to the back wheel surface area is not the cause of the front wheel handling problem.

What am I missing? Weight distribution?

10

The bike has to lean into the wind. Lets’s say it is from the right. When the wind increases you get blown to the left, when the wind increases your tilt on the bike causes you to steer right. The same gust blow the bike more left on the rear disc, balancing the force and you go less left. In other words it blows the disc further left making you go right, but the increased force on trispoke makes you go left.

When the wind decreases, the force pushing the disc left is reduced more than the force is reduced on the trispoke, so the rear tends to go a less left (more right) so the right hand steer caused by the tilt is less.

A trispoke front and box rear does the opposite.

11

That’s clear as mud…

12

I’ve had a lot of experience with tri spoke wheels, not Hed but Nimble. If your not used to it and if your not a relaxed rider, don’t use it. The tri spoke is stable under all conditions, it’s the rider who tries to manage it and tenses up that is the problem. I’ve learned to relax in those conditions, but I still can’t go full bore. The speed at which this happens varies with individuals (dependent on what speed you start becoming uncomfortable and start to tense up). For me, my next windy IM race, I’ll use a wheel similar to Nimble Fly. If you rode constantly in training with the tri spoke, you eventually would become vary relaxed with it and probably would never have a problem, BUT this close to the race, go with something you’re used to.

13

Here’s the laymans take on the science:

The weight of the rider is disproportionately distributed between front and rear. Depending on rider position this can be as much as 30/70. Steering meanwhile, happens at the front of the bike. The pressure of the wind on the rear wheel accentuates the downward pressure of the rider and as the bike does not steer from the rear, it effectively creates more pressure under the rider thus stabilizing the bike.

Meanwhile, the wind forces on the front wheel, being well in front of the center of mass, create steering forces that attempt to redirect the bike. If these are not offset by similar forces at the rear wheel (as with two similar wheels) the bike becomes difficult to control. If it is more than offset (as with a disc rear) the steering force of the wind is actually diminished, resulting in a more stable ride in windy conditions. Of course in gale force winds, all bets are off.

My one experience with a HED CX front (60mm, about the same side surface to catch wind as an H3) and a Rolf Vector Pro rear (much less surface) was a near catastrophe. I was dialing in some last minute changes a few days before a race and it happened to be somewhat windy. The bike was almost completely unmanageable. On gusty days prior, I’ve noticed that the pair of Rolfs catch wind from the side and make the bike a bit skittish at speeds above 35 mph. Meanwhile, at CaliMan last year I had a great bike ride in horrid wind conditions running a disc rear with the HED Cx front. I heard a lot of riders complaining of handling difficulties due to the wind, but I can honestly say the wind didn’t affect the handling of my bike in any noticeable way.

Perhaps the most famous miscalculation in this regard was Fignon using dual disc wheels for the final TT of the '89 TdF and thus losing to LeMonde. There was not a lot of wind that day, but enough to cause Hinault significant difficulty and allow LeMonde to make up 58 seconds and win the Tour.

Many people consider this a huge mistake by Fignon, but the fact is that a lot of guys used dual discs in those days, just not when there was a risk of wind. One of my friends shared his experience of riding a dual disc setup on what was a well sheltered course with a short bridge over a small river. When he emerged from the sheltering of the course onto the bridge, crosswinds put him on the ground so fast he never had a chance to react.

A similar miscalculation was made in the final TT of the '04 Tour when Ulrich ran the Mavic IO five spoke wheel (Mavic says it’s for track riding only, i.e. indoors) on a rainy and windy course with disastrous results. A few others have used that wheel in TTs, and it’s OK as long as it’s a calm day. It has a great deal more surface area than the H3.

14

I have double H3’s (wish I had a disc rear. At the sprint Tri at Oxnard last year, narrow bike lane, on the highway, cars, 30-40 mph crosswind, I had to get out of the aerobars on one stretch.

I borrowed a disc one windy day and rode the first 15k first with the double H3 and then H3/disc. Big difference, especially when I was in the crosswinds.

I’m gonna get a Renn for next year.

15

Here’s the laymans take on the science:
That’s painfully obvious (and if your bike’s weight distribution is 30/70, regardless if the 30% claimed is on the front or the rear, you need a new bike).

16

“if your bike’s weight distribution is 30/70…”

Ever notice how much longer your front tire lasts than your rear? Ever notice how much more frequently your rear flats? Why do you suppose that is?

17

“if your bike’s weight distribution is 30/70…”

Ever notice how much longer your front tire lasts than your rear? Ever notice how much more frequently your rear flats? Why do you suppose that is?
That is the basis for your conclusion? The reason for your rear tire wearing faster than the front include torque (that does not exist on the front) and weight distribution, but if the weight distribution is either 30 or 70 percent (not sure which you are advocating, nor that either is actually possible on a road bike) on the rear wheel you need a new bike.

18

“if the weight distribution is either 30 or 70 percent (not sure which you are advocating, nor that either is actually possible on a road bike) on the rear wheel you need a new bike.”

30/70 would be extreme, but if you think yours is 50/50, think again.

My point refers to the steering effect of crosswinds with and without a disc wheel.
The question at hand is “does a box rim rear and H3 front make a good combo?”
Answer: Hell no!

Now John Cobb can explain it better than I can, and understands the vectors far better than I do. However, his answer to the question would be essentially what I’ve given. Weight distribution will actually change dramatically depending upon your pedalling power. Under hard braking, the weight transfers forward. On a hard climb, it may go down to 10/90.

19

30/70 would be extreme, but if you think yours is 50/50, think again.

Really? And what is your basis for that statement (regarding both percentages)?

Weight distribution will actually change dramatically depending upon your pedalling power.

You clearly have no grasp of physics, and specifically how it applies to bicycles.

20

I don’t understand how a H3 front and a H3 back does worse in a cross wind than a H3 front and a disc back.

It intuitively makes no sense to me as the surface area from a disc is substantially higher than a tri spoke, when a cross wind is hitting it.