Tires for snow Articles

Introduction

Tires provide for steering, traction, braking, and load support by transmitting forces between the vehicle and the road. Lateral Force Variation (LFV) is a property of a tire that characterizes its dynamic behavior of these forces. High values of LFV for a given tire reflect a high level of manufacturing variations in the tire structure that will impart ride disturbances into the vehicle in the lateral, or steering, direction. LFV is measured according to processes specified by the ASTM International in ASTM F1806 – Standard Practice for Tire Testing.

LFV can best be explained by example. Assume a perfectly uniform tire mounted on a perfectly round wheel loaded with a constant force against a perfectly round test wheel. As the wheel turns, it turns the tire, and the tire carcass undergoes repeated deformation and recovery as it enters and exits the contact area. If we measure the lateral force between the tire and the wheel we will see zero change as the tire turns. If we now test a typical production tire we will see the lateral force vary as the tire turns.

Consider a good tire with LFV of 4 pounds. This tire will induce a 4 pound force sideways into the vehicle every rotation. The frequency of the force will increase in direct proportion to rotating speed. This affect will influence the steering of the vehicle. Tire makers test tires at the point of manufacture to verify that the RFV is within allowable quality limits. Tires that exceed these limits may be scrapped or sold to markets that do not require stringent quality.

Waveform Analysis

LFV is a complex waveform. It is expressed using several standard methods, including peak-to-peak, first harmonic, second harmonic, and higher-order harmonics. In production LFV testing these are reported as both magnitudes and angles.

Canadian Tire Financial Services (CTFS) is the Financial Services arm of Canadian Tire.

History

CTFS began in 1961 as Midland Shoppers Credit Limited, a small company offering third-party credit services. In its early years, many Canadian Tire stores in Ontario had signed onto its program. In 1968, the company was purchased by Canadian Tire and re-named Canadian Tire Acceptance Limited. In 1995, it began issuing a MasterCard, becoming a non-deposit taking, financial institution.

In 2002, Canadian Tire Acceptance Limited became a bank and therefore changed its name to Canadian Tire Financial Services.

In October 2006, CTFS began a pilot project in two Canadian municipalities to offer more traditional banking services to the public. In Kitchener-Waterloo, Ontario and Calgary, Alberta, customers can visit Canadian Tire stores and obtain information on opening up a savings account, a GIC account or obtaining mortages directly from Canadian Tire Financial Services.

Options Mastercard

The Canadian Tire Options MasterCard offers benefits similar to those offered by conventional MasterCards, while also offering Canadian Tire “Money” on-the-card, similar in nature to many loyalty programs offered on other credit cards. They also offer special promotions from time to time such as a rebate promotion in partnership with MDG Computers.

One-and-Only Account

The One-and-Only account provides an account that allows users to roll their Mortgage and other lending accounts with their day-to-day banking accounts.

High Interest Savings Account

The High Interest Savings Account is similar to other high interest accounts by offering a higher interest rate per dollar to conventional savings accounts.

Other Products

CTFS also offers GICs and Mortgages. All their deposit accounts are insured by the Canadian Deposit Insurance Corporation

For the Chinese city, see Siping (city)

Siping is a process of cutting thin slits across a rubber surface to improve traction in wet or icy conditions.

Siping was invented and patented by John Sipe in the 1920s. Sipe worked in a slaughterhouse and grew tired of slipping on the wet floors. He found that cutting slits in the tread on the bottoms of his shoes provided better traction than the uncut tread.

The process was not applied to vehicle tires on a large scale until the 1950s, when superior tread compounds were developed that could stand up to the siping process. On roads covered with snow, ice, mud, and water, sipes usually increase traction. A US patent to Goodyear claimed sipes improve tire traction as well, and tend to close completely in the tire “footprint” on the road. A 1978 study by the US National Safety Council found siping improved stopping distances by 22 percent, breakaway traction by 65 percent, and rolling traction by 28 percent on glare ice[1].

Tire tread block shapes, groove configurations, and sipes affect tire noise pattern and traction characteristics. Typically, wide, straight grooves have a low noise level and good water removal. More lateral grooves usually increase traction. Sipes are small grooves that are cut across larger tread elements. Up to a point, more sipes give more traction in snow or mud.

As is often the case, there are compromises. Winter tires, and “mud and snow” tires, may have thousands of sipes and give good traction. But, they may feel “squirmy” on a warm, dry road. Treadless racing “slicks” on dry roads give maximum traction. These have no sipes, no grooves, and no tread blocks. They also have very poor traction on wet surfaces. Tire manufacturers use different tread rubber compounds and tread designs for different tires’ usages.

Large sipes are usually built into the tread during manufacturing. Sipes may also be cut into the tread at a later date, called “microsiping”. Bandag developed a machine for microsiping which places a curved knife blade at a slight angle on a rotating drum. The drum is placed so when it is pressed against the tread the tire is pressed into an exaggerated hollow, as if driving down a rail. The drum is lubricated and rotated and the knife makes a series of diagonal cuts across the tread. For improved traction, the tire may be siped twice, leaving diamond-shaped blocks. A significant problem with field siping is that the tread picks up rocks, glass, and other hard road debris in use, and even with thorough cleaning the knife service life is often poor.

Microsiping can dramatically improve tire traction in rain and snow. However, microsiped tires may also have increased road noise and tire wear when operated on dry surfaces.

In Massachusetts in the 1970’s, it was legal to operate a school bus with bald tires, provided they were double microsiped.

Both Bridgestone and Michelin sell snow tires that are siped at the factory, while Saf-Tee Siping and Grooving sells machines that can sipe most standard vehicle tires. Siping can also be done by hand. Be aware that siping the tires can void the manufacturer’s warranty.

The 5HP18 was the first 5-speed automatic transmission for passenger cars. Introduced in 1991 on the BMW E36 320i/325i and E34 5 Series, the 5HP18 was designed for longitudinal engines and produced by ZF Friedrichshafen AG.

Applications:

• 1992–1995 BMW E34 530i M60/B30
• 1993–1995 BMW E36 320i M50/B20
• 1993–1996 BMW E36 M3 S50us/B30
• 1997–1999 BMW E36 M3 3.2 S50usB32