On 22/12/08, Bruce Dayton, discombobulated, unleashed: >Yeah, many people with 4 wheel drive seem to forget that almost all >cars have 4 wheel stop. But the slippery surface doesn't work so >well. So SUV's usually have no advantage for stopping over other >cars.
A vehicle with more than two driven wheels is able to slow down better by using the gears, as the engine braking effect acts on all the driven wheels - to a point. Most 4WDs have open differentials and so drive is always transferred to the wheel with least grip - just what you don't want. Vehicles with locking diffs are at a distinct advantage here. Alternatively, vehicles with some form of traction control (like my Land Rover) have a system that detects lost traction at a particular wheel and applies small amounts of brake to that wheel, combatting the loss of traction. In practice it works well. Some 4WD vehicles have what is known as 'part-time' 4WD where only the rear axle is driven until the front axle is engaged manually from inside the cab, and maybe free-wheeling hubs from outside at the front wheels. Others, like later Land Rovers and Range Rovers have three diffs - one across each axle and one at the gearbox, all open - and known as 'full- time' four wheel drive. The gearbox diff can be locked (closed) from inside the cab on the fly, but this then only gives the same traction as the part-time 4WD with the front axle engaged. Again, cross-axle diff- locks are the ultimate. As has been expressed here, it is the nut behind the wheel that lets the whole thing down. (from a 6 am ferry somewhere off the coast of Scotland, probably sent via wi-fi sheep :) -- Cheers, Cotty ___/\__ || (O) | People, Places, Pastiche ||=====| http://www.cottysnaps.com _____________________________ -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
