Can anyone take the trouble to explain to me how the Front wheel drive breed of SUV's with four wheel drive coming in when wheel slippage is detected handle on tarmac. I understand the theory off road whereby wheel spin is spotted and drive is sent to all 4 wheels, hopely maintaining progress. I am interested in what happens in a typical front wheel drive understeer cornering situation.
I am the happy owner of A MK1 RAV 4 LWB with permenent 4 wheel drive and quite enjoy it's on road handling. A little like a bigger non turbo Impreza. Obviously a fuel saving with these new SUV's compared to mine in theory.
Thanks in advance
Mark W
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By theory, if the car has central differential, then you should not feel anything.
If it has a locking differential on rear, there might be tyre scrubbing following cornering.
It it has viscous coupling based 4WD, then rear diff (open - not locked) will prevent scrubbing.
However, I've not done this personally so don't know if theory matches with real life incidents.
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An example taken from HJ's own road test of the 2002 CRV;
Under the floor, Honda's hydraulic Dual Pump four-wheel-drive system does the same job as before. In most conditions drive is to the front wheels only, but if the system detects any slippage at the front, it engages a clutch to the rear wheels. This works very well in wet grass, mud and snow, and also in the wet on mountain hairpins where the rear wheels clutch in and push the car around the corner without it scrabbling for grip.
Most of the other "part-time" 4WD SUVs will probably handle similarly - the rear wheels will power up and help push the car round and overcome the understeer....
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I can vouch for that - our CRV handles just as you say - and ours is an auto! Great for taking away from roundabouts - just clicks in the rear wheels, and you can belt it round with total confidence.
And reverting to 2 wheel drive helps keep tyre wear down as well as keeping fuel consumption up to the 30+mpg
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Rav 4's do not have permenant four wheel drive.
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If you are concerned about handling why do you have a SUV? None of them have good handling. I would say that if you keep getting understeer then either you need to adjust your driving style or buy a car that handles.
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If you are concerned about handling why do you have a SUV? None of them have good handling. I would say that if you keep getting understeer then either you need to adjust your driving style or buy a car that handles.
My Forester handles fantastically well, better than many saloons :)
MVP
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Correct its a softroader looks as though it might do but but can't.
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Thanks the comments so far.
1) MK1 RAV and the MK2 RAV is permenent 4x4 unless i am very wrong, over to the forum...
2) What is a SUV then if none of the RAV's are. I only used it as a collective term to make text of mail easier.
3) Is understeer the same as wheelspin?, i thought not. ie understeer is the nose pushing wide. Surely not quite the same as wheelspin.?
4)Surely a neutral permenent 4x4 set up eliminates most of this understeer, whereas a part time mainly front wheel drive set up does not?
5)I have a tremendous respect for the Forrester!
I have no issue with the handling of my MK1 RAV
Look forward to all your comments which i have a tremendous respect for!
Mark W
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Ravs are two wheel drive with a limited slip diff bewtween the wheels so it transfers power to any of the four wheels never 4 at the same time.
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>>Is understeer the same as wheelspin?
NO. In fact all modern vehicles understeer to a greater or lesser degree when there's no acceleration or braking going on.
The understeer you have been talking about is what happens when you are applying power during the corner, and might be better described as power understeer. No modern cars fundamentally oversteer - you have to provoke them to get this to happen.
The "oversteer" that you see on programs like top gear is better described as power oversteer - the car will still fundamentally understeer.
Once you have gross wheel slip that wheel can no longer support any significant sideways force anyway - effectively, you've gone beyond the sensible limits of the car's handling.
Number_Cruncher
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My Mk2 Rav4 is most definately 2wd only!!
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