I am losing town line sprints with my midweek cycling group largely it seems because my front derailleur (all 2x9speed Dura Ace with clamp on FD) refuses to shift up to the big ring when I really need it.

at moderate speed and light load, she shifts like a dream.

But when Bill jumps and I want to respond and start to chase him down (and so I am already spinning the pedals fast) but need more speed), she balks.
and even dropping it down to a 12t but on the small ring, I can't get enough speed.

what suggestions?
is it my sprint-shifting technique? (I am a no nothing on race tactics)
or could there be a mechanical or setup issue?

Many thanks

Peter

2 part answer.

First, my experience with Bill and other of his ilk would make me suggest that you always be in the big ring except when you *must* be in the little ring to go up a hill. You shouldn't be shifting on the front to catch a lead out. Anticipate what is going to happen and get ready for it.

As to the mechanical question, make sure the FD is not jammed up and moves smoothly. My 9 and 10 speed DA FD would get jammed up from too much sweat and gatorade. You can usually check this by pulling the cable where it it parallel to the down tube. FD should move smoothly and easily. If sticky, remove it, clean it and lube it up. After that, check the entire FD setup and adjustment according to Shimano's instructions.

Yep, if you're riding like that you should already be in the big ring. Specially if you are that close to being in your smallest rear cog.
Modern bikes with pinned and ramped chainrings are usually very reliable shifting. Old style flat rings sometimes would rattle a bit before shifting under load.
But a front shift will always be a bit slower. Check your limit screw isn't set too tight and you don't have too much slack in your shift cable. Front derailleur adjustment is an art and small tweaks are not unusual to get perfect shifting.

When in Rome, do as the Romans do. I'll echo the call for the "anticipatory" shift. I'll bet Bill was already in his /her big ring.

I'm not certain under how much load you are trying to shift but I am inclined to think that your front derailleur could be tuned better (not that disagree about anticipating the move or anything, why aren't you in the big ring if he is?). At least up to what I consider moderate load, I expect a front shift to happen seemlessly without a perceptible break in pedaling other than a slight slowdown as the taller gear comes on board.

I would first go out and practice your technique with the lever itself. Make sure you are fully depressing the lever and holding it fully rocked for a split second. A sloppy movement of the lever might not hold the chain in the right position long enough for the crank pins to pick it up onto the big ring. If you are certain you are doing all you can there, I'd move on to adding a bit of tension, maybe 1/4 turn at a time and looking for an improvement. If your downshift to the little ring starts getting slow, you've added too much tension. Actually, first clean and lube the derailleur at all pivot points to clear out any crud that maybe be limiting the movement of the cage.

If you don't make any progress with that quick stab, let us know and we can dig deeper. Things like proper positioning of the FD relative to the chainrings and crank and chain wear can all contribute to sloppy shifting.

The front derailleur is not supposed to be shifted under load. Proper shifting technique for the front is to let up on your pedaling pressure until the shift is completed. This is due to the tension on the top side of the chain when load is applied to the system. In order to shift, the chain has to be pushed sideways and catch on the shift pins. The shift pins then lift the chain up and onto the big chainring. If you are applying a load to the chain, it will slip off the shift pins and drop back onto the smaller chainring.

This.

but our regular Goodwood Ontario townline sprint (which marks the coffee break) is just beyond (about... 150 yards beyond) the crest of an incline, a slight uphill.
It's only ever once we reach the crest that someone goes for it.
I can labor up that incline in the big ring, but do I not put myself at a disadvantage by not being able to accelerate quickly when the time comes?
I feel that way in the big ring and so have been starting on the small ring and then trying to pop it up to the big ring to finish the job.
But that might just be lack of experience.

Front shifting is not supposed to happen under full load, certainly not in a sprint.

From your description above, ride the hill in the big ring and a bigger rear cog and then you'll be ready at the crest of the hill. Then just up-shift as needed.

sometimes though Bill (the little stinker) just outpedals me. Last week he was riding a modified setup that seemed to have just a 38/42 front. And he still beat me in his 42.
But that will not happen again.

This is a friendly ride for a bunch of near or over 60s with just a little bit of friendly competition at 2 points - the coffee break and the finish.
A) both of these townline sprints come just after an incline which (for our old legs) would require a Big-Big combination. So we are transitioning from the small climb.
B) We are generally at about....22-25mph when we hit the hill but slow somewhat once on it. we probably hit the crest at no more than... 15mph?

But really it's a game to see what goofy sprint technique takes the day. Some days no one even bothers to contest the sprint. (Though I've sometimes thought I was the only one racing, only to be scooped by some cagey oldtimer when I let up before the sign.)

overall, it's all just a good laugh. though I don't like losing due to equipment failure or expecting too much from my gear at the wrong time. Pilot error or a slight adjustment, I can work with.

Why is it then that every reviewer, at least for recent Dura Ace groups, loves to go on about how well the front shifts under load? Are they doing something wrong that this works for them? I am doing something wrong that it works for me? Sure, BITD with flat rings shifting under load would be impossible but we're out of the dark ages now. Those little pins and ramps work, or they should work. Of course, it is possible that the OP really is botching the shift or standing on the pedals on trying to get the front shift to happen, hence my suggestion to practice and tune. I don't get the wholesale discounting of the idea of shifting the front under load, though.

To be fair the OP indicates he's using Dura Ace 9-speed, originally released in 1997. The big ring from that crank appears to have pins but not much ramping. I think chainrings have improved since then.

My son, a 210 lb. body-building nut who likes to spend 99% of his time in the big ring and smallest cog, complained about being unable to shift back to big after the occasional, brief stint in the small ring. I had to explain that there must be a reduction in chain tension, or the chain can't possible climb onto a bigger circle. "Oh, I get it!" he said. He's doing better now.

An analogy is standard shift in a car: You must let up a little on the gas when shifting, or you will inevitably damage the clutch and/or the trans.

The best way to deal with Bill is to sabotage his bike before the race.

let off the load.. shift early. before you put the strain on the chain.

Replace your big chain ring and see if there is a difference. How many miles do you have on the big ring? Abuse over time will degrade performance to the point of jeopardizing the functionality