Eddy Posted 14February, 2015 Report Share Posted 14February, 2015 Hi, why are rear wheels wider than front wheels? Link to comment Share on other sites More sharing options...
Steiny Posted 14February, 2015 Report Share Posted 14February, 2015 I'll bite - something to do with maximum traction on the rear while being able to steer the front, maybe? Link to comment Share on other sites More sharing options...
Shady Speedway Posted 14February, 2015 Report Share Posted 14February, 2015 Toyotas MR2 ran a 14 on the front and 15 on the rear. Work that out? Link to comment Share on other sites More sharing options...
StevepGT3 Posted 14February, 2015 Report Share Posted 14February, 2015 Because it would look stupid the other way around Link to comment Share on other sites More sharing options...
Eddy Posted 14February, 2015 Author Report Share Posted 14February, 2015 what advantage the wider on the rear Link to comment Share on other sites More sharing options...
Shady Speedway Posted 15February, 2015 Report Share Posted 15February, 2015 Though the front and rear wheels look the same and turn in the same direction The tasks they perform are considerably different. For the a large majority of these cars...... Front wheels steer and do about 70% of the braking. The rears propel the car do the rest of the braking. Different requirements result in different solutions. Link to comment Share on other sites More sharing options...
ByronBayChris Posted 15February, 2015 Report Share Posted 15February, 2015 Because it would look stupid the other way around I just love the technical knowledge and the willingness to share that knowledge around. I can just see the Porsche engineers in the old factory with some cold ones on the shelf tossing a coin to see if they should put the fat wheels on front or rear. Lucky for us it was heads Link to comment Share on other sites More sharing options...
JustJames Posted 15February, 2015 Report Share Posted 15February, 2015 At least part of it is something called the traction circle. Basically, there is only so much grip available. When you're using all of the available grip for braking, there is less grip available for steering (on the front wheels). In a RWD car, you need more grip at the rear because you don't want lots of grip available for accelerating (plus cornering). A 'funny car' dragster highlights this, with mahoosive rear tyres for off the line acceleration, and super skinny fronts because braking and cornering are not a big deal in a dragster's life. The other consideration, particularly for cars without power steering, is that wider tyres would make for heavier steering. Finally, wider tyres are more likely to suffer from aquaplaning in the wet, so relatively skinny fronts clear most of the water ahead of the fatter rears. There's obviously lots of compromise going on, to arrive at a least-worst-for-all-conditions scenario. Link to comment Share on other sites More sharing options...
ByronBayChris Posted 15February, 2015 Report Share Posted 15February, 2015 I think Steve's answer was simpler, though James. Link to comment Share on other sites More sharing options...
Dreamr Posted 15February, 2015 Report Share Posted 15February, 2015 I just love the technical knowledge and the willingness to share that knowledge around. I can just see the Porsche engineers in the old factory with some cold ones on the shelf tossing a coin to see if they should put the fat wheels on front or rear. Lucky for us it was heads Sure would have made the 930's less desirable .... Link to comment Share on other sites More sharing options...
cyberpunky Posted 15February, 2015 Report Share Posted 15February, 2015 coz staggered looks tough ? Link to comment Share on other sites More sharing options...
Peter M Posted 15February, 2015 Report Share Posted 15February, 2015 After reading most comments, the styling and marketing departments obviously said to do so. Link to comment Share on other sites More sharing options...
Coastr Posted 15February, 2015 Report Share Posted 15February, 2015 Lots of rear drive cars run wider wheels at the back. The reason why more cars don't is because of spare wheels. Back in the day the Porsche space saver was pretty rare but now lots of cars run them. The reason is already given - more grip, essential for combating oversteer, amd great for getting off the line. Link to comment Share on other sites More sharing options...
Stew F Posted 15February, 2015 Report Share Posted 15February, 2015 having worked in packaging (the process of compiling the sum of a cars elements into a final product) and other departments at a couple of auto makers I can say that a great deal of work is put into achieving that race car look on any sports variant, including rim and tyre combinations, exterior trim colours, exhaust note, and so on. But wheel and tyre combinations there are also often technical considerations like traction, steering and braking footprint. But when you see options of wheel combos for the same car it's purely based on aesthetics. Link to comment Share on other sites More sharing options...
Steiny Posted 15February, 2015 Report Share Posted 15February, 2015 Ok - I thought the OP was like one of those 'why did the chicken cross the road?' Link to comment Share on other sites More sharing options...
Tit Posted 15February, 2015 Report Share Posted 15February, 2015 For the 911...there's also a bunch of weight hanging over the tail of the car. There's likely a dynamic reason to spread that pressure. Link to comment Share on other sites More sharing options...
Coastr Posted 16February, 2015 Report Share Posted 16February, 2015 For the 911...there's also a bunch of weight hanging over the tail of the car. There's likely a dynamic reason to spread that pressure. I agree with you...but I wonder how many FWD cars would handle better with wider wheels on the front? Link to comment Share on other sites More sharing options...
Tit Posted 16February, 2015 Report Share Posted 16February, 2015 I agree with you...but I wonder how many FWD cars would handle better with wider wheels on the front? Link to comment Share on other sites More sharing options...
StevepGT3 Posted 16February, 2015 Report Share Posted 16February, 2015 Yep, looks stupid Link to comment Share on other sites More sharing options...
Coastr Posted 16February, 2015 Report Share Posted 16February, 2015 How did I know someone would find someone who did that! Clearly for drag racing, that one. I wonder if it corners better with fat slicks on the front? Link to comment Share on other sites More sharing options...
Tit Posted 16February, 2015 Report Share Posted 16February, 2015 Yes. Its for drag racing. I'm sure they swap the wheels back to drive home... Link to comment Share on other sites More sharing options...
Peter M Posted 16February, 2015 Report Share Posted 16February, 2015 I wonder if it corners better with fat slicks on the front?Maybe but can you imagine how bad the "tramlining" would be on rutted roads, how heavy the steering would be a slow speed and how huge the turning circle would be?Actually all the same reasons our old 911's don't run the same size tyres on the front! Link to comment Share on other sites More sharing options...
JustJames Posted 16February, 2015 Report Share Posted 16February, 2015 Why would the turning circle change?If the inside edge of the wheel is no further in than with the skinny wheel, wouldn't you get the same wheel angle, and therefore the same turning circle? Link to comment Share on other sites More sharing options...
Peter M Posted 16February, 2015 Report Share Posted 16February, 2015 James,Depending on the actual offset and wheel width of course, it would either contact the wheel arch in the case of that extreme Golf example earlier or more commonly, contacting the inside rear of the inner guard.I think you can actually buy adjustable lock stops for older 911's to stop the tyre contacting the vertical panel that separates the wheel well from the frunk area by limiting the maximum steering angle.I notice my wider front wheeled 993 has a larger turning circle than my skinny wheeled G series for this reason. I guess when they laid out the 911 body tub in the early sixties Ferry and Edwin thought no one would ever dream of using rims wider than about 5 inches. How times and fads change!RegardsEDIT: This shows it better than my mangled description above on lock stops: http://www.elephantracing.com/suspension/tirerub/911tirerub.htm Link to comment Share on other sites More sharing options...
D-banger Posted 16February, 2015 Report Share Posted 16February, 2015 For the 911...there's also a bunch of weight hanging over the tail of the car. There's likely a dynamic reason to spread that pressure. The 901s had the same wheels all around, but 5 psi more pressure in the rears. Link to comment Share on other sites More sharing options...
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