Tried 2 Gboost belts today, DBSD383 and WBB383. Both fit length and width very similar to a 571, wide belt with length. Also ran 821 and an aged 571 that might be down 100rpms or so. Had a Gates Redline as well but it is too wide for my shimmed primary,
21 xrs, 25 45 gears, Hrss pdm2 setup. 571 is spot on rpms 7800 and builds to 79-8000. snow covered lake with some icy patches but nothing you would break loose on once hooked up, only about 800-900ft and you have to get out of it, top speed on dream meter 104- could have got more but not looking to kill my breaks yet. Sorry, no real data but temps some info on the how the belts fit in with others. Did about 15 belt changes and a lot of mid speed running getting them all heat cycled a couple of times so very time consuming.
WBB383 is very similar to a 571, maybe 100-200 rpms more or very similar to a new one. Will spend some time with this one comparing long term to 571.
DBSD383 is very soft and grippy, very similar to the XS821. Both of these belts grip so well that for the clutching I was running today you could pin it bottom to mid and be 600-800rpms low and then it would build to around 7800, so final rpm 200 less than 571 and 300rpm less than WBB383. final top speed in the short distances were the same on all belts but as noted, short distances so does not mean much. Not sure when I will have time to dial in the softer belts, would need a lot of weight pulled to get the response with the Ramps I am using.
All belts were pretty similar on clutch temps in these conditions, fast easy rolling, belts side temps were all 100-130 deg F depending on where you hit it and fixed primary sheave was 125-150F on all. Harder belts could have used more weight and softer belts less so nothing was dialed perfect yet.
So if you like XS 821 and your clutching works well for that belt try the DBSD383,
If your clutching is setup for Doo belts the WBB383 is what you would want. Will dial this one and get some miles on before I attack the others.
FWIW the only belt that was noticeably different on temp today was a Gates Carbon fiber, quite hot comparatively. Also if you have not shimmed your Pdrive the Redline will probably engage a bit lower and load early with it is width.