Tri-tip is nothing more than a big steak, so don't try and over complicate it. Cook it like a steak, let it rest, and slice. I cook hundreds of pounds of it, and I find that letting it rest for up to an hour works best. I cook it over direct heat, and it usually only takes 25 minutes to reach an internal of 125. Throw those babies in a warming box (Cambro, ice chest, whatever you have) an after an hour, you have Tri-tip heaven. So timing wise, once your cooker is up to temp, 1 1/2 hours and you're ready to serve. I know a lot of folks like to smoke then reverse sear, but were talking a steak, and IMHO, a steak should be cooked like a steak
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