Forgot to add I live and race in rural Australia our roads are not the same quality as you have in the states mostly rough bitumen

The rear isn't as important for tire selection. I would be inclined to use the Conti Attack in the 22 width. While the 4000s/20 sounds like a good choice, there is a big difference in Crr between the 20 and 23.

A lot of people are going to 25mm, because it's more comfortable, absorbs the bits and pieces on the road better and is just as fast. Also you will find that some (including me) are putting on latex tubes. Softer, more comfortable, faster.
For aero the front is more important.

hi mike can you elaborate a bit more on what the difference in crr between the 20and 23 is about, are you saying the 20mm would be a better tyre or the 23mm conti gps4000s for the rear hed 3? Sorry I find this stuff very confusing. What is the conti attack I haven't heard much of that tyre on this forum, most seem to talk about the super sonic or gps4000s tyres?

The more aero tire will be the 20mm, but the 23mm is probably better suited to the road conditions and won't be that much less aero on the rear.

The GP4000S is more durable (thicker tread), less supple (higher CRR), and more flat resistant (has an anti-puncture belt) than the Supersonic. The comparison is relative, the 4000S is still a race tire. For your road conditions it's probably a better choice.

I have a 23 Supersonic on my back wheel, but I race in California, mostly on smooth tarmac.

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The GP4000 has very different rolling resistance between the 20 and 23 width. All the info you could ever want is at the BikeBlather site

https://docs.google.com/...jNOs/htmlview?pli=1#

You are kinda looking for a reasonably narrow tire with good aero properties and low rolling resistance, but you need some durability for bad roads. The GP 4000s/23 or the Attack/22mm are probably some of the better

Ok thanks guys based on the info you have given me I'm going to go with a gps4000s in 23mm for the rear HED 3 with latex tube.

Now I will also be getting a front HED 3 soon and am going to order a tyre for it at the same time as I order for the rear. I have read on here several times that unless your using a 20mm supersonic on front of HED 3 you are giving up heaps of time I think Thomas gerlach has said that several times. I haven't seen much on using a 20mm GPS4000s up front on a HED3 anyone know how this would compare to the supersonic up front? Would rather stick with a 20mm tyre on front as from what I can tell the front HED 3 operates best with a narrow front, my average speeds are around the 40km/h mark or slightly quicker on a flat course sprint Olympics if tha makes any difference

See the previous comment. The 4000s in the 20mm width has a much higher rolling resistance compared to the GP4000s in the 23 width. I ride the SS 20 on my front H3 with latex tube and sealent and I haven't had any really bad luck. Anything that will pinch flat a SS will probably do in the 4000s.

ok so disregarding the supersonic 20mm due to flat issues what would be the next fastest tyre for the front HED 3 averaging speeds 40kmh+ would the 22m conti attack be faster on the front than the conti gps4000s in 20mm? I don't really understand all those graphs and charts im a bit simple lol

Ok so deciding between 20mm gps4000s or conti attack 22mm on front, anyone care to say which tyre will be faster based on the speeds im doing? One last question what length valves do I need for tubes on the HED 3 wheels

thanks