Yokohama's new Geolander H/T-S...
Yokohama's new Geolander H/T-S (255/55R18 109H M+S) and Raceline's Phat Series 283 Excess (18x8-inch with 4.5-inch backspacing) make a compelling visual statement on this '99 GMC Sierra. The Raceline/Yokohama package is rated to handle up to 130 mph with proper load and tire pressure and pull 0.92 g in our lane change test.
In spite of the fact that wheels and tires have the most influence on the handling, performance and style of your sport truck, these critical components rarely receive in-depth discussion or analysis of their performance and design attributes. To fill that informational void, we at ST decided to begin a regular column devoted to this extremely important component category. We begin this column with a review of the Raceline forged-aluminum Phat Excess wheel and Yokohama Geolandar H/T-S. In this first installment, we'll compare the Yokohama Geolandar tire with a typical factory-supplied tire in order to communicate the performance differences between these two tires.
The OE replacement rolling stock combination is built on stamped-steel 16x7-inch wheels with 5-inch backspacing wrapped with a P235/70R16 tubeless radial with two plies of polyester supporting the sidewalls and two plies of steel and two plies of polyester supporting the tread. The plus-two rolling stock upgrade consists of a set of Yokohama's Geolandar H/T-S P255/55R18 109H mounted on a set of forged-aluminum Raceline Phat Excess 18x8-inch with 4.5-inch backspacing.
We tested these tires on a 4.8L automatic '99 GMC Sierra with a 2/4-inch dropped suspension from Hotchkis Performance. Both sets were tested at the factory-recommended 35 psi of air pressure and driven over the same test drive loop with all cornering and braking tests performed at the same site.
Before our dynamic testing, we inspected the tires for symmetry and weight. It surprised us to find that both the stock and the upgrade package were not perfectly round. The stock wheel and tire showed a slight oval shape, while the Yokohama was slightly eccentric, like a cam. The eccentric shape of the Yokohama came from the tire, not the wheel, compared with the stock setup that showed some out-of-roundness in both the tire and the wheel. These are minor differences and are routinely balanced out with with weights to produce a smooth ride. We also weighed each tire/wheel combination, and to our surprise, both the OE and the upgrade combinations weighed the same: 62 pounds each.
The Raceline Phat Series 283...
The Raceline Phat Series 283 wheels highly polished forged-aluminum surface features chamfered cutouts and dimples to add interesting detail to the design. They also come with a polished aluminum lug cover plate with security key. The design puts the valve stem behind the wheel face for a super clean look.
Another area of rolling stock performance we tested was body interference at maximum steering angles with the vehicle while driving and at rest. Both sets of tires had no clearance issues either at rest or while driving, which is what you'd expect with an OE tire and wheel and a plus-two combination that has the same circumference as the OE unit. In addition to the benefit of not interfering with the body, the fact that gearing didn't change meant we didn't have to mess with recalibrating the speedometer or install a rear gear to compensate.
Our next area of evaluation focused on tire noise at various speeds on common road surfaces. The OE replacement tire was very quiet. At freeway speed, tire noise wasn't an issue as the wind noise was louder than any tire noise. In surfaces with some roughness, such as expansion joints or irregular patches, the OE replacement tires weren't noisy at all, even on older, worn pavement with gravel exposed from erosion.
The Yokohama Geolandar was noisier than the OE at freeway speed. Its tread noise was noticeable but not excessive, more of a "white noise" whirring than a harsh-tread-generated noise. Over joints and other surface displacements, the tires pop, indicating the increased stiffness in sidewall and tread. The OE replacement tires were very quiet on these road surfaces. The above quality of the OE tires comes from a very compliant sidewall designed to maximize ride quality. The soft sidewalls allow the tire to absorb road shocks to promote a smooth ride.
In comparison, we found the Yokohama Geolandar H/T-S quiet firm.The emphasis of this tire is handling, grip, and load capacity. The sidewalls and the tread are stiffer. This results in a tire with more feel through the wheel and frame and a good grip that gives you a lot of confidence. The truck is several magnitudes more sure-footed compared with the stock tires. The trade-off, though, is a firm, almost harsh, ride with the higher rate springs and shocks of the lowered Hotchkis suspension. A point we should address here is that with the stiffer sidewall of a high-performance tire, the roundness of the wheel will impact ride quality more so than with a more compliant tire. In this case, the Raceline Phat Excess wheels provided an almost perfectly symmetrical wheel, which allowed the tire to run smooth and true even though the tire wasn't perfectly symmetrical.
The Raceline 283 Excess is...
The Raceline 283 Excess is a two-piece design constructed from forged aircraft-quality aluminum. So in addition to its appealing style, Raceline's 283 Excess is strong enough to manage heavy cargo and high cornering loads, vitally important for sport trucks.
In contrast, the soft sidewalls of the OE tire allow the tire to develop large slip angles at relatively low cornering speeds. That aspect was very apparent in the handling ability of the OE tires. In our 45-mph lane change test, the truck was controllable, but the tire's grip profile was vague and felt greasy; the tire lost traction very gradually. The tire tells you it's coming loose almost from the beginning of any cornering maneuver and slowly goes into a full slide.
On the other hand, the Yokohama gave a much better performance in the 45-mph lane change. The tire's stiffer sidewall and tread allows it to respond quickly to steering inputs at the beginning of a turn and at its well-defined adhesive limit. We recorded a peak of 0.92g of lateral acceleration in this test, and the vehicle was very controllable and responded well to steering inputs, even near the limits. This tire inspires confidence, even when drifting around in a 4,700-pound extended cab pickup.
The OE tire is overly forgiving in that the tire filters out at least half of your steering inputs when it begins developing cornering force and 99 percent at the ill-defined limits of adhesion. That's good for inexperienced drivers as it keeps the truck plowing along; you'd have to work real hard to get the truck sideways. In our testing, we saw a peak cornering force of 0.77 g in our 45-mph lane change test. This is exactly the performance this type of tire is designed to give.
In our braking test, the OE replacement tires produced 0.98g peak force, with the truck stopping from 60 mph in 135 feet. The Yokohama generated nearly identical rates of deceleration and distance. We recorded a 0.98g peak deceleration with a stopping distance of 133 feet.
At first, these results may seem contradictory. The tire with the most lateral grip should also have more grip longitudinally and produce superior deceleration rates. This, however, is not the case. A wider tire with a stiffer sidewall will deform less under the weight transferred on the front tires during braking than a soft-sidewalled tire. That means there is actually a smaller contact patch generated by wider performance tires under braking than that generated by typical OE tires. More rubber on the road equals more traction, producing higher deceleration rates.
The conclusion of this comparison comes down to this: If you want the grip and control of a performance tire, be prepared to make a few sacrifices in ride quality. Our comments regarding the styling aspects of the OE wheel/tire combination compared with the 18-inch polished-aluminum Raceline wheels and Yokohama tires are noted in the captions to the photos. Since a photo is worth a thousand words, and questions and opinions of style can fill volumes, we feel it's best to let the product do most of the talking
Yokohama's latest is designed...
Yokohama's latest is designed for plus-sizing and features handsome sidewall design and a very sporting, stylish, and functional directional tread pattern. Compared with the OE tire's footprint, the Yokohama tires make the truck much more sure-footed in our performance tests.
Performance Summary:
OE:
Wheel: 16x7-inch with 5-inch backspacing; stamped steel, chromed stamped cosmetic cover
Tire: P235/70R16 M+S. Tread: Two-ply steel; two-ply polyester. Sidewall: Two-ply polyester. Ratings: Tread wear A; Traction A; Temp B. Max load 1,984 at 35 psi
Wheel/Tire Weight: 62 lbs
Steady State Cornering:
Not much grip; lots of steering angle needed to get truck to react
45-mph Lane Change Peak Force: 0.77
Cornering While Accelerating: A little more prone to power oversteer; it felt loose and vague
Cornering While Braking: Easy to force into understeer; not much directional control when braking hard into a corner; less directional control with ABS activated compared with the Yokohama Geolandar H/T-S4
Braking: 0.98 g/135 feet
Road Noise: 65-mph fwy below wind noise; 45-mph smooth surface below wind noise; rough surface slightly above wind noise barely noticeable. Old blacktop: below wind noise
Ride Quality: Soft/moderate/harsh
Comment: Smooth, quiet ride
Raceline/Yokohama Plus-Two Upgrade:
Wheel: Raceline Phat Boy Series 283 Excess 18x8-inch with 4.5-inch backspacing. Forged-aluminum two-piece, welded; polished-aluminum finish. Available sizes: See chart.
Tire: Yokohama Geolandar H/T-S (GO52) 255/55R18 109H M+S; Tread: two-ply steel; two-ply polyester; one-ply nylon; Sidewall: two-ply polyester. Ratings: Tread wear: 420; Traction A; Temp A; Max load: 2,271 lbs at 50 psi maximum air pressure. Available sizes: 235/65R17 108H; 275/55R17 109H; 255/55R18 109H; 265/60R18 110H; 285/60R18 120H; 305/50R20 120H
Wheel/Tire Weight: 62 lbs
Steady-State Cornering: Excellent grip and feel; tire lets you know exactly what's happening at the contact patch; good linear response to steering inputs
45-mph Lane Change Peak Force: 0.92 g
Cornering While Accelerating: Good positive grip and feedback; takes the power and moves the truck forward without trying to step out on you; very positive and sure-footed
Cornering While Braking: Excellent grip and far more control compared with the OE tires with the ABS activated. These tires would help you avoid obstacles under severe braking that the OE tire couldn't avoid
Braking: 0.98 g/133 feet
Road Noise: 65-mph freeway slightly higher sound level; 45-mph smooth surface road noise is noticeably loader than stock; rough surface slightly louder. Old blacktop: same white noise, just above wind noise
Ride Quality: Soft/moderate/harsh
Comment: The ride vibrates at higher frequency than with stock tires. The attack is harder and it puts more energy into the suspension
| 283 Excess SIZES: |
| Size | BoltCircle | B/S |
| 17x8 | 5-4.5/4.75 | 4.5" |
| 17x8 | 5-5/135 | 4.5" |
| 17x8 | 5-5.5 | 4.5" |
| 17x8 | 6-5.5 | 4.5" |
| 17x10 | 5-4.5/4.75 | 6" |
| 17x10 | 5-5/135 | 6" |
| 17x10 | 5-5.5 | 6" |
| 17x10 | 6-5.5 | 6" |
| SIZE | BOLTCIRCLE | B/S |
| 18x8 | 5-4.5/4.75 | 4.5" |
| 18x8 | 5-5/135 | 4.5" |
| 18x8 | 5-5.5 | 4.5" |
| 18x8 | 6-5.5 | 5" |
| 18x9 | 5-4.5/4.75 | 5.5" |
| 18x9 | 5-5/135 | 5.5" |
| 18x9 | 5-5.5 | 5.5" |
| 18x9 | 6-5.5 | 5" |
| 18x10 | 5-4.5/4.75 | 6.25" |
| 18x10 | 5-5/135 | 6.25' |
| SIZE | BOLTCIRCLE | B/S |
| 18x10 | 5-5.5 | 6.25" |
| 18x10 | 6-5.5 | 6.25" |
| 20x8.5 | 5-4.5/4.75 | 5.25" |
| 20x8.5 | 5-5/135 | 5.25" |
| 20x8.5 | 5-5.5 | 5.25" |
| 20x8.5 | 6-5.5 | 5.25" |
| 20x10 | 5-4.5/4.75 | 6" |
| 20x10 | 5-5/135 | 6" |
| 20x10 | 5-5.5 | 6" |
| 20x10 | 6-5.5 | 6" |