Comparing Off Road Functionality of a SUV to the CRV and RAV4
Increased ground clearance and AWD is still not perfectly comparable with a SUV, which offers 4WD, more gear ratios, and a truck chassis. In Honda and Toyota AWD systems, power is sent to the rear tires proportionally to the amount of slipping detected in the front tires. In other words, the car will never fully power all four wheels. There will always be at least one wheel slipping, therefore full traction will never be achieved and the vehicles ability to crawl up steep rocky terrain will diminish. Furthermore, unlike older SUVs the CRV and RAV4 are equipped with active traction control (TCS), which automatically decreases power output once wheel slipping is detected. In some models this can be turned off with a switch on the dash, but not in the older versions. TCS can be manually disabled in these vehicles by pulling the fuse for the ABS speed control sensor, with the side effect of loosing functionality of the Anti-lock brakes, therefore making this alternative only suitable for uphill driving. Fortunately, front wheel slippage controls rear wheel engagement through an independent hydraulic system, thus disabling the ABS speed sensor or a vehicle electrical failure will not inhibit the vehicle's ability to engage the rear wheels. The bottom line is the AWD system is meant as supplemental traction, not primary traction. A conclusion to be drawn from this is that the AWD system is not made to operate for long periods of time. Addition of friction and temperature modifiers, such as Lucas or Z max, to the lubricants in the differentials, driveshaft, and transmission are one means of preventing premature failure of these components when used within the manufacturer's specifications.
Another factor in off road suitability is the strength of the frame, steering, and suspension components. SUV's have shock insulated steering columns. This is why SUV's and trucks have a "boaty" feel to their steering. The CRV and RAV4, like a passenger car, have solid steering columns. This allows crossovers to have a more responsive feel. Extra care needs to be taken to intercept ruts perpendicular to the front axle as large uneven ruts can snap the steering column. The tires also cannot be turned into large rocks, which is another situation that can result in steering breakage. Excessive speed or cargo over rough terrain can also cause the frame of the CRV and RAV4 to bend or break under excessive stress, therefore extra care to always drive as slowly as possible over rough terrain is necessary to prevent irreparable damage to the chassis and steering components of the CRV and RAV4.
Increasing Off Road Capability of the CRV and RAV4 with a Lift Kit
This invites a key distinction between SUV's and the crossover family, gear ratios. A typical automatic transmission in a SUV has four gears and options for 2WD, 4WD High, and 4WD low. Once 4WD low is engaged, the user effectively gains another four gears, meaning the SUV can offer 8 gear ratios using only 4 gears. Because of these low range gears, the torque loss resultant from an increase in tire size can be effectively mitigated at low speeds. This means the SUV's ability to go up steep grades does not diminish operating larger tires. The CRV and RAV4 do not have the low range gear option, meaning the car has only 4 gears (or 5 in manual transmissions). If larger tires are installed on the CRV or RAV4, the torque loss resultant from increased tire size cannot be effectively mitigated and its ability to go up steep grades will diminish, especially while carrying cargo.
The most important factor to consider in tires is the tread pattern, traction, and temperature ratings. Typical economy and passenger tires offer minimal traction in off road or winter conditions. A blocky tread pattern with lots of siped edges will provide the most traction in all situations. If operating in the winter, find a tire with an "A" temperature rating or other ratings such as a snow flake emblem on the sidewall or a "S" designation such as M+S or AT/S. If the car is operated primarily in the city, good tires to consider are a Yokohoma Geolandar HT/S or a General Grabber HT/S. (The HT/S designation indicates suitable operation on highway, terrain, and snow). For frequent operation in snow or off road, consider BF Goodrich T/A or TAKO, General Grabber AT/S, Rocky Mountain Falken AT/S, or Yokohoma Geolandar AT/S. While other tires bear M+S designations, be sure to discuss sidewall strength with a technician at your favorite tire store. The aforementioned tires offer tougher sidewalls, which is more suitable for off road operation and also offers less loss of steering response than tires with softer sidewalls (aka cheaper tires).
Be sure to select a tire size as close to the original factory size as inventory and budget allows. As discussed in previous sections, increasing tire size is unnecessary in the CRV and RAV4 and also largely reduces torque to the point of reducing the vehicle's ability to climb steep grades. Staying within +/- 1/2" will yield the best results. Smaller tires will be cheaper, increase torque, and get better gas mileage. Crossover's operating 6 cylinder engines can accommodate a larger tire up to a 1" increase in radius, but will still suffer from a loss of torque and gas mileage. A 6 cylinder SUV with stock tires is more suitable for off road operation than a CRV or RAV4 with tire sizes in excess of a 1" increase in radius, at that point with comparable gas mileage. The only situation where larger tire diameters is helpful is for snow clearance on relatively flat roads, in which case up to a 2" increase in radius can be accommodated. Keep in mind larger tire sizes will also put more stress on drive components such as CV joints, differentials, and the transmission. Larger tire sizes may incur more maintenance costs than is worth the trouble for cars driven more than 10,000 miles per year.
Additional Increases to Off Road Capability of the CRV and RAV4
Turbocharging or supercharging are always ideas when increasing power. While this is the most effective way to achieve large power gains, the system will likely present a cost on par with the value of the vehicle and is ultimately unreliable and likely to damage existing vehicle components (such as transmission, differentials, cv drive shafts, etc.) Exhaust system upgrades are the next option for solid state upgrades, however given the low displacement of the CRV and RAV4 engines a notable increase will not be obtained through costly exhaust work. Aftermarket OBD engine tuning chips are another option, but are largely ineffective on 4 cylinder engines.
The last remaining cost effective solution would be a nitrous injection system into the intake just behind the air filter. This allows power to be used on demand, giving less opportunity to damage the car under daily driving conditions. The main concerns with this setup are engine temperature and the nitrous tank. A small fire extinguisher will always need to be on board in a readily accessible location. Several means of increasing the engine's cooling capability are increasing the size or output of the radiator fans, venting cold air directly into the engine compartment (readily achieved using a hole saw and a rain gutter elbow), or installing a water/methanol injection system. Extra cooling becomes necessary because the Nitrous will induce a leaner combustion, meaning more oxygen atoms per fuel atoms than normal. Installing slightly larger fuel injectors or a high pressure fuel pump will increase the amount of fuel in the cylinder, thereby reducing lean combustions during nitrous injections but causing rich combustions during normal driving conditions. The net result of richer combustions is loss of fuel economy and premature failure of exhaust sensors. As an alternative to Nitrous, injecting compressed oxygen (available at welding supply stores) into the system can also be a means of increasing engine power without presenting the danger of a compressed flammable gas being onboard. It works in the same way, but increasing the amount of fuel in the cylinder is more important for power gains as the oxygen itself is not explosive.
The nature of a crossover limits off road functionality when compared to a SUV. The gap can be marginally closed with some upgrades, but the CRV and RAV4 will never serve as a true off road platform. Installing a lift kit should ultimately be considered a means of adding comfort to the cars existing off road capability, not as a way of increasing it. If your primary intention is to frequently travel off road, please read the next section for other possible choices.
Reliable Alternatives to the CRV and RAV4
Saturn Vue's made from 2002 and later offer AWD, horsepower in the ballpark of 200hp, and 23 mpg on the highway. Beware of the CVT on the 4 cylinder versions, which is incredibly prone to failure. Similar cars are the Mazda tribute from 2004 onward and the Chevy Equinox from 2004 onward. The AWD systems on these cars are the same as the CRV and RAV4, however the small sacrifice in fuel economy gets 40-50 more horsepower.
The 2001 ford Escape offers comparable power to the CRV and RAV4 and is rated for 25 highway mpg (the 4 cylinder, of course). This car is equipped with a true 4WD system, however it is not complete with a low range gear set. Still, it is capable of fully powering all four wheels thus providing more uphill traction than other crossovers. Research the 2002 as it has some issues. In 2003 Ford took out the 4WD system, all successive models now run AWD.
The 1996 Nissan pathfinder is a true SUV, offering a heavy duty truck frame, full off road suspension, low range 4wd, and excellent reliability. At 20 highway mpg, its about the best you can do for a cheap old reliable car with low range 4wd. All successive years get terrible gas mileage. Excellent availability of aftermarket parts.