Just a quick question, does the IRS bolt rub on the wheel or the tire when we run wide rears? I'm going to temporarily put 275s on my 10.5s while I wait on my MM bolts and MT 315s to ship. Hoping with the 275 on it I won't have any problems.
I have 18x11 with 315 R888's lowered on eibach w/o iso's and I clear the bolt by .5 inches and rubbed once but I hit a big bump doing 95. You will have no problem.
I have run 10.5" AFS Cobra replicas with 3/8" spacers, H & R Race Springs, and low profile IRS bolts on a Vert with 315/35 NT555R's, NT05R's, and Toyo Proxes TQ's with no issues. 275's being 40mm narrower, depending on the true tire size, on a 10.5" rim should clear with no problem, but as stated, every ride is different...only way to know for sure is to bolt them up and use a jack to run the wheel through the entire suspension travel range.
315/35R17s here with 17x10.5 reps. No low pro bolts and no spacers. When the car is jacked up and you put the wheels on they hit the bolts. But once you lower it down and the suspension is loaded there is plenty of space especially if yours is lowered like mine with H&R sports.
if you are talking about a American Muscle or late model resto wheel...yes, you'll need it. On a higher end custom fit like Trueforged or CCW, no you wont.