Traction Control?

[Mr Pants!]

I have an RX400h and there is no over ride for the traction control:

Why is this?

Also, what are these cars like in the snow? Does the 4wd kick in and help? I know today would be a good idea to find out, but I only drive in these conditions when absolutely necessary.....

[indy727]

Also, what are these cars like in the snow?

A short answer absolutely dreadful!

I know they are not a "proper 4x4" but i expected a hell of a lot better. Mine has just slid a full 60 yards when travelling at just 15mph! in a perfect straight line! no matter what i did nothing changed my direction, i slid straight across a t junction!

I now need to follow this through with lexus because this surely cannot be right? Can anyone make a car this unsafe in this day and age?

Watch this space.

[ihpj]

And the reson is because this vehicle is FWD only. By the time the the car senses the rear is sliding and kicks in the motor, it may be too late...

(I know I'm going to get flamed for my above comments, but I stand by them...)

As for the AWD RX, I don't think you can tak the TCS off - that has a 'SNOW' programme that can help - but you just can't get away from AWD traction (especially in this type of weather).

[MartyCee]

And the reson is because this vehicle is FWD only. By the time the the car senses the rear is sliding and kicks in the motor, it may be too late...

(I know I'm going to get flamed for my above comments, but I stand by them...)

As for the AWD RX, I don't think you can tak the TCS off - that has a 'SNOW' programme that can help - but you just can't get away from AWD traction (especially in this type of weather).

The problems aren't just the car.

Yes, (I have one too!) they are mainly front wheel drive(FWD), but at low speeds the rear motor helps (a light right foot is nnedd & wise in these conditions!!! LOL) the problem is that 4 wheel drive is great for getting you going & helping keep you going in the slippy stuff, but it makes no difference when you want to stop, none at all.

That's down to brakes (& with the RX400h the motors in re-gen mode) & to stop you need grip, without that you need less speed & MUCH longer distances than you would expect.

Having ABS (as do most modern cars) is actually a hinderance in snow becuase it keeps pulsing the brakes, so you get stop-go-stop-go-stop-go, far better to let the wheels lock & plow in to bit further into the surface. As the ABS isn't switchable you back to allowing about 5 times the expected distance to stop.

This has been proved today by the lady returning home after taking her kids to school in her LR Discovery. 25 mph downhill ("I was below 30 to stay safe") & she decided to slow down on the brakes - about 90 feet after that decsion the LR has gone around 180 degrees & backwards through a cotswold stone wall at about 20 mph, no real retardation affect whatsoever due to near zero grip.

The wall is predicted to recover sometime in the sping, (sadly?) the LR may not do so well, it was one of the early ones & needs about 50% of the panels replaced or straightened. In these times of reduced values it may well be at a breakers near you in the next few weeks.

So take it slowly, & think ahead - if a 1100kg Fiesta needs a long way to stop, then sure as eggs is eggs, a Lexus weighing about double that will need a lot longer, 4X4 or not.

[ihpj]

I only posted because the OP was talking about traction issues (and not stopping) - traction is about moving and keeping moving; and as you rightly say, ABS can be a hindrance in the snow and braking is a definite no-no (engine breaking perhaps?) ... wish everyone safe driving in this weather.

[indy727]

Agreed braking is a no no..........but you can only get so much engine breaking out of the 400h box....

Grip is another issue but my experience this morning is by far the worst i have ever experienced in 20y of driving all sorts of cars. If i had the option the lexus would go back now!

[Boxbrownie]

It is really all down to grip...pure and simple! If the tyres are crap then no amount of engine braking/friction braking or electronic assistance is going to slow you down.....not if the tyres are made of cheese! Get some decent rubber....and if you want good traction (both accel and deccel) in the snow/ice you need winter tyres not all season.

For sure the 400h is really just a FWD with electronic assistance from the rear motors, but the 300 is true 4WD and in the snow/ice has great grip from standstill......but I ain't gonna use the brakes (unless I have to) to slow down on my way home tonight, thats for sure! It'll be as much engine braking as it can muster.........

Good luck you folks that are driving today....keep it safe.

Best regards David

[Mr Pants!]

I guess more to the point is the handling and 4WD'ness of the car.

I used to have a Scooby WRX STi, (I know, Chav car), but it was an amazing drive and the 4WD'ness of the car was very good in the wet, really gripped when you put in the power and I am sure would have been good in the snow to as long as you did not floor it. I have found the RX is not quite as clever in the wet, as you would expect of course, but just wondered how safe the Lexus was in the snow, I would have put it above the average car as it is 4WD and I thought all sorts of clever gadgetry to help you through tricky conditions, but reading your posts above, I guess not.... So is that why there is no TC on/off button because it does not exist?

I will use the wifes BMW 1 series instead in this weather if the Lexus is as bad as some are saying.

[jaroph]

I will use the wifes BMW 1 series instead in this weather if the Lexus is as bad as some are saying.

You will not get anywhere fast in the 1 series. My neighbor abandoned his this morning after trying to venture out on minimal snow. His wife's Vauxhall Corsa managed to get him 3 miles down the road. My 400h on other hand went the full 30 mile round trip, including navigating a road with more than 6 inches of snow without the traction control light coming on once!

[Mr Pants!]

So it is really mixed reviews then....

[williz]

Agreed braking is a no no..........but you can only get so much engine breaking out of the 400h box....

Grip is another issue but my experience this morning is by far the worst i have ever experienced in 20y of driving all sorts of cars. If i had the option the lexus would go back now!

i am sorry to say that it is definitely NOT the car that is poorly handling in bad conditions, you need the right tires (and some driving experience in this conditions will help to).

i am driving this car now for more than 100.000 km and the only thing i can say is that it handles great on snow and ice. i live in the lower alps and we have snow from november to march every year.

the electronicaly controlled AWD is working eficient and the VDIM is the best system of this kind i have experianced so far.

the only thing i realy miss is the "snow button" to disable the traction control in low speeds (will be in the RX450h)

this is the road in front of my house and my daily driving experiance during wintertime

[ihpj]

But the issue here is that you perhaps have the benefit of snow tyres which makes a huge difference to the way a car will handle...well in snow. Here in the UK it is an unwarranted expense to buy Snow Tyres just for the day (or three!) you get snow on our roads - so you are stuck with what one may refer to 'all weather' or even Summer tyres all year round (not that we get a Summer!).

So with proper tyres and gentle persuasion, I am sure you manage to negotiate your driveway. Here, it is a completely different story and a FWD 400h will struggle.

[williz]

But the issue here is that you perhaps have the benefit of snow tyres which makes a huge difference to the way a car will handle...well in snow. Here in the UK it is an unwarranted expense to buy Snow Tyres just for the day (or three!) you get snow on our roads - so you are stuck with what one may refer to 'all weather' or even Summer tyres all year round (not that we get a Summer!).

So with proper tyres and gentle persuasion, I am sure you manage to negotiate your driveway. Here, it is a completely different story and a FWD 400h will struggle.

i fully agree with you, the tires make a huge difference (the most important factor between the drivers brain and the street surface are the tires!).

but even with summer tires the RX400h handles not bad in snow (the first february march i drove with summer tires because winter tires of that dimension had been out of stock).

i think people believe to much about marketing talk and then expect that FWD drive cars are not bound to the laws of physics and when reality struck s they complain about the "bad" car!

[jaroph]

A short answer absolutely dreadful!

I know they are not a "proper 4x4" but i expected a hell of a lot better. Mine has just slid a full 60 yards when travelling at just 15mph! in a perfect straight line! no matter what i did nothing changed my direction, i slid straight across a t junction!

I now need to follow this through with lexus because this surely cannot be right? Can anyone make a car this unsafe in this day and age?

Watch this space.

Sliding for at least 60 yards? That can only mean that you were traveling far too fast for the road conditions and misjudged the stopping distance to the T-junction. Sounds as though you also braked in the process. Nothing to do with the car in this instance I'm afraid.

[Ullevi]

But the issue here is that you perhaps have the benefit of snow tyres which makes a huge difference to the way a car will handle...well in snow. Here in the UK it is an unwarranted expense to buy Snow Tyres just for the day (or three!) you get snow on our roads - so you are stuck with what one may refer to 'all weather' or even Summer tyres all year round (not that we get a Summer!).

So with proper tyres and gentle persuasion, I am sure you manage to negotiate your driveway. Here, it is a completely different story and a FWD 400h will struggle.

"Snow tyres" AKA winter tyres are not only for when there is lying snow.

We all run summer tyres in this country and these start to exhibit reduced performance at air temperatures of 7-8 deg Celsius and below as the rubber compound becomes more brittle.Add to this the particular tread pattern in summer tyres and this leads to reduced levels of grip.Grip is reduced in low temps,which we all tend to manage to cope with,but things obviously get worse in the white stuff.

There are plenty of 4x4s crashed in these conditions because of poor driver awareness/skills and the use of summer tyres.

You have to be particularly careful when slowing down in a big,heavy 4x4 as inertia will try to keep you moving and low traction with summer tyres/road condition will make you skid easily.Approach junctions very slowly,and in automatics it helps to knock the car into neutral as you approach the stop as this stops the engine's propensity to keep driving the wheels.

I have been driving my RX400h in 5-6in snow in warwickshire yesterday and today without any problems,and,yes,on summer tyres.My 4 wheel drive system has worked marvellously,kicking in smoothly and unobtrusively when needed,and progress has remained perfect.Sorry to rain on your parade,ihpj.

[indy727]

Sliding for at least 60 yards? That can only mean that you were traveling far too fast for the road conditions and misjudged the stopping distance to the T-junction. Sounds as though you also braked in the process. Nothing to do with the car in this instance I'm afraid.

Sounds valid but trust me i was only doing 15MPH the road was a slight decline so the only way to kill speed was to use brakes in some form. And yes it was 60 yards ....my car just turned into a huge sledge!....I think this speed and slowing down distance were more than adequate regardless of tyres or the poor conditions

[Laura_Lexus]

Sadly, Black Ice/Snow and a slight decline will create a ski run for a 2 ton car traveling at 15mph. This is not due to a failure of the car but a lack of grip, only caterpillar tracks or an anchor wrapped around a lamp post will stop progress. Deep snow will at least give some grip, but predominantly we have had several compacted inches with ice as the base.

On a positive note it sounds like you are safe and no worse for the scare, I do not use the car in hilly areas when icy conditions are present, stay in and stay safe.

Laura

[Scarlet Pimpernell]

The need for Winter tyres cannot be wholly replaced by a 4x4!

I've been a passenger in a Freelander II just 2 days ago in the snow - and that's right - both me and the driver were passengers when he braked!

Even from a standing start it was woeful really...but was able to slither past most cars up a hill.

The problem is that the tyres are not up to the job, and with an RX, it probably weighs so much that there would be too much momentum anyway...

Something with diff-locks might help, but even in the F'lander hill decent made no difference. It was bloomin' dangerous on ice and braking is just a joke...

[BGLister]

I know this is primarily about the RX400h which has been interesting, but I would like to share my experiences in snow with the RX300 and RX350.

I live on the Pennines in West Yorkshire where we have had around 8" of snow in the last couple of days and can say from experience that 'how' the cars are driven is of paramount importance in snow. As has been said above, once you have too much speed and you are heading downhill on ice/snow - the brakes are not going to be able to help you much, except that you may still be able to steer the car more.

I had to go down a steep snow covered hill on Monday and took it really easily. With the RX350, you can drop the gear into 1st and just let the car roll down. I also use the brake VERY gently just to try and stop it from accelerating away. Too much brake though, and the ABS can kick in, and the rear of the car can try and overtake the front. That's why when learning to off road, you are taught to keep your foot well away from the brake. I just let the car down the hill very gently, and I was OK. Much better off than the cars that went ahead of me and crashed into each other and then a dry stone wall. Having AWD does not make you a God or immune to crashing though!

Another thing I do is to let some air out of the tyres so they read arouns 25 psi, gives the tyre a bigger foot print. But I would only do this in extreme circumstances for running on alot of fresh snow. Once back to more normal conditions, I would pump the tyres back up to 30 psi.

Giving the car too much gas on snow/ice can give four wheel wheelspin - and I have done on this purpose but still never seen the traction control light come on to try reign it in. I take it from that that the car is still quite happy with what is going on!

[indy727]

sorry to be a pain and keep going on............but i did take it very slowly, the snow dusting was only very light at 7:00AM my speed was below 20MPH with 100 yards to stop everything was ok or so i thought.

As for brakes if the rear did start to overtake the front at least i would have stopped somehow!!! but no matter what i did it went in a perfect straight line with no grip or control whatsoever.

Not sure what the answer is to my problem, how slow should you go? how much time should you allow? or do you just not take the car out in inclement conditions? or was there a problem with my car in this instance?

Any thoughts anyone?

[Boxbrownie]

Giving the car too much gas on snow/ice can give four wheel wheelspin - and I have done on this purpose but still never seen the traction control light come on to try reign it in. I take it from that that the car is still quite happy with what is going on!

If you think about it logically if ALL four wheels are spinning (presumably at the same rate) the car knows not that you not doing the same "road speed" as the wheels are doing in "rotational speed".....therefore the cars traction control would not cut in, it is designed to cut in when one, two or three wheels are spinning at a higher speed than the ONE wheel that the car thinks has traction.

Good fun though

As for sliding 60yds at 20 mph......no problem on snow over ice with a vehicle of that weight....they make a sport of it in curling!

As I said before and others too.........TYRES......

Best regards David

[paolo137]

As I said before and others too.........TYRES......

I fully agree.

Rx is heavy.

My mark I has always worked nicely on ice and snow both in plain and uphill, with its ordinary M+S "all year round" tyres.

But going down used to be a nightmare: gear to L, an egg placed between the foot and the brake pedal, the odd "snow" button pressed (never undestood compeltely its function, apart from starting off in 2nd gear, maybe, but then, in if I'm in L, what's the use? ), and just hoping that nothing unexpected would happen, as the emergency stop would be hard to handle.

That changed completely a month ago, when I decided to go for a set of Toyo winter tyres (600 €, and thank God I've the 16" wheels).

They're unbelievable: handling and braking has improved dramatically on snow AND ice, and now I can get 100% out of the 4WD. For instance, if I'm going downhill and meet someone coming up at full throttle (because that's the only way for the guy to manage the steep climb without proper tyres), I can brake safely, put in reverse, and reach the nearest passing place. All of this smiling like an idiot while the other guy struggles with the steering wheel.

For comparison, my Mom's Panda 4x4 and my wife's Daihatsu Sirion 4x4, have no problem at all even in the direst conditions and with conventional tyres: it's all in the weight!

By the way, regarding the transmission of the (non-hybrid) RX, I've read some posts where the car is stated to have a part time 4WD, normally front WD and with the central diff kicking in only when needed.

Others claim that the drive is always 50% front, 50% rear.

I must say that the car handles like a full time 4WD, but I would like to get a definitive answer to that. Thanks :winky:

P.S.: I know that a set of winter tyres is expensive, particularly if you have 17" or 18" wheels, but be sure that the lightest crash into a wall or another car will cost way more, and that's not considering possible personal injuries!

[Scarlet Pimpernell]

....or take out 10PSI from the tyres - makes a huge difference - especially when braking - Tyre width doesn't help one iota either - the snow just gets compacted into the grooves and the effectively become slicks...

By reducing the pressure the tyre becomes "flexible" and more likely to tract

[aido]

....or take out 10PSI from the tyres - makes a huge difference - especially when braking - Tyre width doesn't help one iota either - the snow just gets compacted into the grooves and the effectively become slicks...

Was under the impression that the narrower the width of the tyre the better for snow as you've got more weight over that one particular area, so therefore a car with say a 6 inch wide tread would perform much better than the same tyre with a 9 inch width tread? Hence why cars with wide rear tyres are useless in the snow?

Definitely agree with letting the pressure down though in the snow :)

[dave1]

Approach junctions very slowly,and in automatics it helps to knock the car into neutral as you approach the stop as this stops the engine's propensity to keep driving the wheels.

Whilst I would agree with most of your comments, putting the car into neutral is certainly inadvisable. If you override the autobox and change down manually you are allowing the engine, via the driving wheels, to assist in slowing the vehicle down. It is never adviseable to put any car into neutral and allow the it to coast. If the pressure you exert on the brake pedal is very light as you approach the stop then you will stop safely.