Spacer goes over wheel studs and is only secured when the wheel bolted on. Adaptor is bolted on by its own set of lug nuts and the wheel is then bolted on. Adaptor can be used to do the same thing as a spacer but can also be used to change bolt patterns ..I hope I've explained it. Someone else can try if I haven't . As to why one is illegal and one isn't is I imagine the concern is putting too thick a spacer over the studs and not enough threads showing to properly secure the wheel.
-- Edited by Bob T on Saturday 11th of June 2016 11:54:45 PM
Here's the difference;
Wheel spacers apply too much leverage to the base of the wheel stud which can cause them to fail because the clamping force of the wheel nut is further away from that critical area. Wheel adapters don't cause this because they are bolted to the axle flange, and the wheel is bolted to the adapter. It's simple physics. The only proper way IMO is to have the correct offset on your rim, because spacers and adapters are just a band-aid to cover up a poorly designed setup.
Professional drag racers have used spacers for years very successfully and safely in order to compensate for different wheel and tire widths and different strip conditions. The difference is they use a grade 8 stud , the spacer fits tightly on the studs [ not loose like you buy at Can. Tire] and the stud goes through the lug nut and a certain number of threads must be visable. The nuts are also properly torqued.
The difference with the spacers/adapters are quite clear and the spacers should be snug as Bob says.
I've ran Strange axles for years on the track cars and they are always threaded, not a pound in stud. My studs must stick out a good 1/2" with the deep open lugs for the old wheels I use.
I think I could have used my old lug nuts, but was flagged on inspection once. I don't really remember why. We have an Inspection guy here for St Thomas here somewhere so I'm betting he could tell us ?
I'm gonna stud up the front of the car also, because it's a bummer to get to the track and get flagged at the gate. I always had spare lugs, but I totally understand why the visable studs would be mandatory.
I bought a set of 11/2 inch rear spacers for my 2014 Mustang. The spacers bolted on to the original 5 bolt wheel studs. Bolted wheel on the studs that are on the spacer which are the same size as the original studs which gives you the correct size for lug nuts. Torqued all 10 bolts per wheel to 100 pounds, and checked after 300 kms. Everything was fine. IMPORTANT make sure they are hub centric spacers.
