Hi all Christian from Australia here Our $$dollar is higher than yours at the moment so its time for me to import some wheels for my 68 firebird I want to fit some 17in wheels and want to know whats the widest i can fit under standard wheel wells. What backspace? Looking at American Racing 500 vintage wheels My car has std rear end with drums,front end has discs with single piston callipers. Pypes twin system exhaust system. Also what size tyres do i need? Thanx Chris
Optimum front size is a 17x8 with a 4.75 backspace. Since the front is stock, a 235/50R17 is probably the largest you can fit. If you do the Gulstrand Mod or taller balljoints or taller spindles to allow a negative camber curve, then a 245/45R17 should fit without rubbing.
On the rear you can do a 17/9.5 with a 5.5 backspacing. A 255/45R17 will definitely fit. The 275/40R17 typically fits, but can require rolling the fender lip in some cases (original manufacturing tolerances vary, and amount lowered may affect it).
Thanx for the input. In the front,can a 17x 8in wide rim fit with a lesser backspacing?Like 4 inch? Whats the offset on the front wheels you mention? Thanx Chris PS: I am after American Racing vintage AR500's,do you know where i can get them from?
Make sure to watch your BS so you do not have more of a dished rim up front compared to the back. A 9.5 rim in the back is a little to tight for my taste. I had a set that I was told would fit but I would have to jack the back of the car to make them fit without rubbing. I now have a 8" wide rim in the back and with the correct size tire I have the whole wheel well filled up and some wiggle room for body roll or suspension travel.
I don't know what the offset works out to on the front. But if you want to run a 4" backspace, you'll need to drop to a 7" wide rim. Even then, a 4.25" backspace would be better. You might get away with it if you use a 225/55 tire.
Remember if you have too much backspace you can always use a spacer to adjust, but if you go too shallow you're kinda stuck.
P.S. If you go too deep, it rubs on the frame first at full lock. So worst case is slightly less turning radius. To shallow you rub on the inner fender itself as the suspension compresses which is a real concern.
Most tubular control arms will clear without any more modification. But I've heard before that when using factory control arms you'll need to grind off the top of the frame mounts. They don't mention it in this article. However there has also been several versions over the years, and the one in the article appears to have the least amount lowering. So it's possible it may clear without grinding the mounts or the arms.
Not sure if grinding is absolute but it was too close for my taste when I did mine so I did go at it with the grinder a bit. Not much but just enough. I thought about cutting the "ears" off but am glad I didn't because I eventually went back to the original mounting holes.
Maybe if you use the following combination: 1) do the Gulstrand mod (or taller spindle) 2) dial in -1° static camber in the alignment 3) and run a 225 width tire
it might work.
The problem you might run into is rubbing on the inner fender towards the outside of the body as the suspension moves while driving down the road both straight or cornering.
Like I said before, if you go with a little too much backspacing, worst case you rub the frame at full lock. Not a problem during normal driving, and can be compensated by a think spacer if it really bothers you.
Thanx for your input guys, Ihave decided to run 7's in front,my car has the subframe off and all in pieces so i can't measure up for my wheels. I'll play it safe and stick with 7's Thanx again Chris PS:Wheel spacers are illegal in oz,come to think of it anything above 16in wheels ara also illegal.
