Tire chains and cables are devices that improve traction in snow and ice. Chains provide better traction than cables, however cables are easier to install; both are acceptable under the law for most vehicles. Tire socks are also acceptable. Plastic devices, straps, and other emergency or alternative "tire chains" do not meet the legal requirement.
You can purchase chains or cables at most auto parts stores and gas stations, particularly in communities surrounding Yosemite National Park. A limited selection of chains is available for purchase at the Village Garage in Yosemite Valley and the Wawona gas station. Be sure to purchase chains or cables that match your tire size. Roller Blind Chains
It's difficult to find businesses that rent chains; they're usually only available for purchase.
Rental car companies generally don't provide chains, however rental cars are not exempt from chain requirements, even if they have all-season tires.
An alternative to using tire chains is to park your car at a YARTS bus stop on Highway 140 outside Yosemite (e.g., Mariposa or El Portal, depending on current chain control location), and use YARTS (which requires a fee) to travel into and out of Yosemite.
If you are visiting any location in Yosemite from November through March, you should expect chain requirements to be in effect, even if you only plan to visit Yosemite Valley and use the free shuttle. Any time chain controls are in effect, all vehicles must have chains in possession, including four-wheel drive and rental vehicles.
Chains are often required on roads both inside and outside of Yosemite from November through March, less often in October and April, and rarely in September or May. Because high-elevation roads receive more snow, chains are required on the Wawona Road (Highway 41), Big Oak Flat Road (Highway 120 from the west), and Badger Pass Road more often than on the El Portal Road (Highway 140), roads within Yosemite Valley, and the Hetch Hetchy Road.
Call 209/372-0200 (then, 1, 1) for updated road information inside the park. This recording is updated whenever road conditions change and is the same way in which park staff gets road information. This recording includes information about current chain requirements. Remember that conditions can change rapidly.
Keep in mind that these chain requirements are not unique to Yosemite and apply in all the mountainous regions of California. You may encounter chain controls even before you enter Yosemite. You can check on current chain requirements for the following roads outside of Yosemite: Highway 41, Highway 120, Highway 140, Highway 88, and US 50.. You can also call 800/427-7623 for road conditions throughout California (these links and phone number do not provide information about roads within Yosemite).
You must have tire chains or cables in your possession when entering a designated chain control area, even if you're driving a four-wheel drive or rental vehicle. (Designation is by a sign that says "chains required.") If you're driving a vehicle that doesn't allow tire chains, consider using YARTS to travel into Yosemite.
Conditions dictate when chains are required, therefore, it's not possible to predict if chains will be required ahead of time. We strongly recommend that you have chains when visiting Yosemite from November through March (chain requirements may be in place on occasion as early as September or as late as May); conditions can change rapidly and chains can become required at any time.
Within a designated chain control area, you must use chains or cables on your car's drive wheels when the chain control sign does not exempt your car. Even if your car is exempt, you must have chains or cables in your possession.
All vehicles must have tire chains in possession.
There are no exceptions; all vehicles must use chains.
When you encounter a chain control sign that indicates chains are required for your vehicle, pull completely off the road into the turnout and put on your chains. Chain control signs are at the best locations for putting on chains. Put your chains on there, not further down the road, where it may be unsafe.
Just because you have chains or four-wheel drive doesn't mean driving in snow is easy. Even park residents who regularly commute on park roads during winter are involved in snow-related accidents. Follow these tips to reduce your chances of an accident.
The speed limit within chain control areas is 25 mph, even if other signs indicate the speed limit is higher.
You will be subject to a citation (up to $5,000) if you fail to put on chains when required. Further, if you don't have chains with you, you may have to call a tow truck to supply chains for you (this could cost up to a few hundred dollars and is not covered by AAA; the wait can be several hours).
Countless accidents are caused by motorists who lose control because they don't have chains, and many of those drivers have winter driving experience. Don't be responsible for injuring someone, damaging vehicles, or inconveniencing hundreds of other park visitors by causing an accident: use chains when required and drive with caution.
An alternative to using tire chains is to park your car on Highway 140 outside Yosemite, before you encounter any chain controls (the location of which varies based on conditions), at a YARTS bus stop and use YARTS to travel into and out of Yosemite (fee required).
Chain Operated Roller Doors Caltrans has a list of frequently asked questions about chain requirements.