What size spacer to use for the front to make the width the same as the rear for a square set up with same rims. Any negative affects?

 

Do you mean to get equal flushness front to back or to get equal track width front to back? As far as flushness goes if you're non staggered you'd need something like 5-8 mm spacer in the rear, not the front. This isn't feasible on stock studs and you'll need to get lengthened studds. There are 10-12 mm spacers available with build in studs however that's too much and the rears will become more flush. If you're talking about track width it looks like the front is about 1-1.5 inches narrower than the rear. So by rough math you'll need at least 12 mm spacers. With how poor our outboard clearance is at the front with most nonstaggered setups I don't you'd want to run that much spacer unless you've got wide front fenders.

 

Yes I’m wondering if it’s worth trying to make the front and back the same width with running 17x9 +45s all around. I do have arp studs.

 

I imagine the main change to adding such a large spacer is increase to positive scrub radius. My understanding is that most RWD cars naturally have a decent amount of positive scrub radius baked into the design. Im no engineer but from what I can gather the increased scrub radius will increase the natural propensity of the front wheels to toe out when moving forwards as the ground “pushes” the wheels out. This theoretically may increase tire wear and maybe increase the sensitivity of steering response. You could theoretically install a large enough spacer that it dramatically increases the swing arc of the wheel enough that you can clearance issues with tire front and rear edge of the fenders. That said, you’d be landing somewhere around +30 offset which people have run before without too much problems regarding handling, albeit with wide body.