Some thoughts:

• the disc will be the bigger difference for sure
• the deeper front won't make much difference
• tire choice is a bigger issue than the front wheel 6/9

[Technical appendix: evaluating discs is difficult because the magnitude of the savings is very sensitive to yaw angle and also because they have considerable savings in "watts to spin", which is not possible to measure in existing wind tunnels. Thus, you will see a wide range of opinions even among smart people on how much discs actually save, and I honestly don't think anyone knows precisely. I've seen at least one smart person say it's not much, but he was basing that on his own extensive wind tunnel testing which isn't capturing everything, and I disagree. He probably was also assuming zero yaw angle, which isn't realistic. I've done a ton of testing of all sorts, but in all honesty haven't spent much time on disc/non-disc for rear wheels (who has?), so my opinion is based partly on front wheel testing and partly on reading lots of wheel-only tunnel tests by others. The front wheel question has been tested a ton in all sorts of ways by lots of people.]

Disc on the back.

Unless you are chasing every let watt, I’d just stay with the 6 plus up front. I linked to an article from the front page when these first came out. On the second graph you can see the Jet 6 plus and 9 plus compared. At a yaw angle of 10 there is only about 20 grams of drag of difference (which equates to around 2 watts). At 5 degrees the difference is only 5 grams. Depending on your speed you’d end up saving maybe 2-5 seconds per hour of racing by going with the 9 vs the 6. The downside would be a heavier wheel that maybe be harder to handle in a crosswind.

https://www.slowtwitch.com/...lus_review_4421.html

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Matt

Rear disc.

Second hand rear disc...
paid GBP £195 for Shimano one from a few tears ago yesterday,
Still running tubs, but hey.

Hed cycling spain has tested Hed 6 vs Hed 9 and disc. The difference between 6 and 9 front is really small, but handling in windy condition can make you lose the 2 seconds per hours benefits of the 9 more quickly.
This is the video link :

https://www.youtube.com/watch?v=-yHi5ReFazA

Keep the 6 front, and maybe you could put a disc cover on your jet 9 rear. With duck tape inside and isolation tape outside, you can do a very clean and fast disc wheel for just 100$ (Hed jet disc is an ardenne wheel with carbon cover).

Thanks for the input guys. I was kind of thinking that the disk would probably be the best money spent. I live in a pretty coastal area and it's generally pretty windy so i do like having the 60mm on the front. I can confidently ride that in any condition so also that has to be factored.

I looked into making a disk cover a while back so I'll probably do that initially and keep an eye out for a good deal on something.

Thanks

I thought the Thomas Gerlach site showed a Jet 6+ faster than the 9+ until yaw was at speeds considered "kind of slow"?

So, disc for sure.

Who is Buck? And what's he riding now?

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"What's your claim?" - Ben Gravy
"Your best work is the work you're excited about" - Rick Rubin

Rear disc cover.

Disc back. As posted above, you may even be slower with the 9 upfront depending on wind on the day.

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And that's a very realistic prospect for where I train and invariably race most of the time. I've ridden the 60mm in pretty bad conditions and it's a very predictable wheel IMO.

Thanks.