Wheel & Tire Fitment
The '73-77 GM A-body-particularly the Chevy Laguna-is known for its large, tank-like body, huge wheelwells, and bulging wheel arches, so the smaller performance tires that fit Chevelles, Camaros, and Novas just don't look large enough for the proportions of the car. Looking through various manufacturer tire size charts, we quickly came to the conclusion that we needed something along the lines of a performance sport truck tire size. General Tire makes a very good one-the Cross Contact UHP (ultra high performance)-in a 275/55R17 (UTQG 420 treadwear rating, AA traction, A temperature), which fits a 17x9 rim perfectly, and has a 28.9-inch diameter and an 11.2-inch section width. That's a tad taller than our old 275/60R15s, and about the same width.
All that figuring isn't as...
All that figuring isn't as good as actual measuring. We ordered the wheels and tires, but stopped short of mounting them. We kept the plastic rim protectors on the rim and bolted the rim to the front. Using a jackstand under the ball joint, we lowered the car to put weight on the suspension. We cranked the wheel both ways, checking for clearance with the control arms, and found no issues.
With the old wheel/tire combo (275/60R15 tires on 15x8 Bassett steel rims) and cut Global West springs, it was a snug fit, but we never experienced any rubbing. Our new Year One wheels are an inch wider with a 5-inch backspacing, compared to our 8-inch-wide steelies with a 4.5-inch backspacing. The new wheels would essentially put the outside of the rim a half-inch closer to the fender, and a half-inch closer to the inside, thus splitting the extra width evenly between outside and inside.
It was a really close fit at full wheel lock, but there was no rubbing at all with the full turning range of the steering explored. Taking a ride around the parking lot revealed that there was some minor rubbing at full lock, but a few weeks later at the Goodguys autocross track, we had no problem hammering the two-ton beast through the cones at full gallop.
For '73-77 GM A-body fans out there, here's what we've got: Global West springs (cut to lower the car 2.5 inches in front), 17x9 Year One five-spoke Rally alloy wheels with a 5-inch backspacing, General Cross Contact UHP 275/55R17s at all four corners, and 1/2-inch ARP wheel studs with 1-inch NASCAR-style lug nuts. Fitment of the 275/55R17 tires on the 17x9 wheels is fine in the rear, with plenty more room to spare. If Year One made a 17x10 with a 5-inch backspace, it would easily fit, and we would've put a 315 tire on that.
Next, we cut up an old coat...
Next, we cut up an old coat hanger and wrapped it around the shape of the General Cross Contact UHP to simulate the tire cross-section. We taped the coat hanger to the inside of the rim, and then rotated the tire through the range of motion with the weight on the suspension. If your new wheel can do this, you're pretty much out of the woods.
The stance of the car is sweet. To look at the profile, you'd swear the car was 'bagged, but it isn't. In fact, with the front lowered 2.5 inches, there's still more than 5 inches of ground clearance. Moreover, there is plenty of room on top of the front tire wheelhouse, and in the area of the wheel lip. These cars just have tons of space for big tires. That's the combo, folks.
As for cost, this particular setup will run you about $800 for the Year One Wheels, and about $520 for the General Cross Contact UHP tires (pricing them through Tire Rack). Figure just over $1,400 total after tax and balancing.
The other side of the brake...
The other side of the brake line attaches to the hard line on the chassis. Miller used a 7/16-inch and a 11/16-inch line wrench to tighten the fitting, which passes through a retaining clip on the frame.
A 9/16-inch wrench is used...
A 9/16-inch wrench is used to tighten the banjo bolt through the brake hose and onto the caliper. You'll want to do this right the first time-the dead-soft copper washers that seal the system will conform to a unique shape after the first try.
The increase in the piston...
The increase in the piston surface area over stock means we needed a smaller-diameter master cylinder to create the same brake pressure. A new master cylinder from CPP brought the cylinder diameter down from 1 1/8 inches to 15/16 inches. There is a slight difference in pedal feel, with the new CPP unit exhibiting a longer, smoother stroke with better modulation. The new CPP master cylinder (PN 6150012, $115) is a direct swap for the stock unit.