I'm glad you like them, as I've just splashed-out on a pair of 24mm tubulars. Didn't go for the 27mm rear as I have a narrower Zipp 900 disc.

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29 years and counting

Is there a downside to using the new 24mm Zipp tires on the older Zipp wheels which were designed for 21mm tires? Will they glue properly or is the extra 3mm in width not an issue? The rolling resistance data looks much better compared to the previous Zipp Tangente tires but is there an aero penalty for a tire that is wider than the rim in this case or does Crr dominate? I was going to go with the Schwalbe Ironman 22 until they stopped using latex.

I wouldn't think so. People glue 33mm cyclocross tires to zipp carbon rims and don't have a problem. Don't know this for sure, but I would imagine that the base tape they put on there is the same width for those two tire sizes, and that is what you are actually gluing to. I use 23s on my pre-FC zips without issue.

Just got the 27 mm for my rear Super 9 and the 24 mm for my 808 Firecrest front. Got them after Tom posted the CRR results of the new Zipp tires and tubulars on his blog. I will test them thoroughly next week and will post about them. I do not think the width will offset the gain in crr on the rear but there's no aero data to be found yet...