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Automatic Auto-brake For Hill Starts


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I've seen several threads that suggest the new IS auto has an auto-braking feature that stops the car rolling back when doing a hill start. Having driven the new IS and all the GS range recently, I could find no evidence of this (only the GS300 held). My current IS300 doesn't hold either.

Curiosity got the better of me, so I asked the Service Manager at my local dealer and he says this feature doesn't exist on any of the past or current range of Lexus cars.

He reckons some people think there might be something because their car holds on hills, but this is caused by the natural internal drag of an auto box, influenced by the idle speed and temperature (hence viscosity) of the gearbox oil.

Just though I'd share this with the forum for confirmation or comment.......... :blink:

IanB :D

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I still believe that there is something going on as there isn't enough forward drive from the auto box to stop it from rolling backwards on a steep hill. Also, there have been times where the car would sometimes roll backwards, and sometimes stay still, on the same hill depending on how I've brought the car to a halt.

When it does hold, you can actually feel the car clicking into some kind of locked position - I'd never really paid much attention to it before, but now I'm quite curious. Will ask my dealer next time I take the car in and see what they say.... :)

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I still believe that there is something going on as there isn't enough forward drive from the auto box to stop it from rolling backwards on a steep hill. Also, there have been times where the car would sometimes roll backwards, and sometimes stay still, on the same hill depending on how I've brought the car to a halt.

When it does hold, you can actually feel the car clicking into some kind of locked position - I'd never really paid much attention to it before, but now I'm quite curious. Will ask my dealer next time I take the car in and see what they say.... :)

Yes puzzling isn't it. A second opinion will help, and more from the forum no doubt.......!

When I drove the GS300, I thought I detected similar symptoms to you, but all the other cars just rolled back freely.

IanB :D

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Perhaps I can add somethng to this....

The new GS DOES have a brake hold on hills but it depends on how steep the hill is before it kicks in. If it's just a slight incline it works the sameway as all auto boxes and the torque converter slips and provides enough drag for you to move your foot from the brake to the accelerator pedal. When you are on a steep hill and you come to a complete stop and lift your foot from the brake pedal, the car senses that it is about to rollbackwards and applies the brakes. Ths is immediately cancelled as you push the accelerator.

I have tied this on several occasions on differing inclines (with nothing behind me just in case :D ) and it has worked each time I have been on a steep(ish) hill.

I can't speak for the new IS as I have never driven one.

The Ed

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Most of the people I know who drive automatics keep their foot on the brake if stopped on a hill say for

traffic lights. When you want to go forward, just go from brake to accelerator, you have the power on before the car ran roll.

Starting on a steep hill with foot 'handbrake ' on ....start, engage D with your foot on the brake, then release the parking brake when you have your foot on the accelerator.

If it's a hill like the side of a house, put some revs on before releasing the parking brake.

All becomes second nature after a couple of days if your not used to autos.

If you NEVER drive manual you can brake with you left foot, power with your right but this is a recipe for

disaster if you have to switch between auto and manual. :blink:

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Tried on a slight incline today on ny IS250 auto and when I took foot off brake and gas just to sit there it was creeping forward. I guess if I was on a real steep hill I'd use both feet if it wanted to roll back ( had to this on an off road day this week in a Freelander automatic, after first time it was easy and they were really steep hills ).

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I've seen several threads that suggest the new IS auto has an auto-braking feature that stops the car rolling back when doing a hill start. Having driven the new IS and all the GS range recently, I could find no evidence of this (only the GS300 held). My current IS300 doesn't hold either.

Curiosity got the better of me, so I asked the Service Manager at my local dealer and he says this feature doesn't exist on any of the past or current range of Lexus cars.

He reckons some people think there might be something because their car holds on hills, but this is caused by the natural internal drag of an auto box, influenced by the idle speed and temperature (hence viscosity) of the gearbox oil.

Just though I'd share this with the forum for confirmation or comment.......... :blink:

IanB :D

On page 145 of the IS250SE-L owners manual is listed the "Hill-start assist control (vehicles with an automatic transmission)

Prevents the vehicle from rolling backwards when starting on an incline or slippery slope.

This is obviously something more than just the natural drag of the torque converter. Maybe your Service manager needs to read up on the IS250's features. :duh:

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On page 145 of the IS250SE-L owners manual is listed the "Hill-start assist control (vehicles with an automatic transmission)

Prevents the vehicle from rolling backwards when starting on an incline or slippery slope.

This is obviously something more than just the natural drag of the torque converter. Maybe your Service manager needs to read up on the IS250's features. :duh:

That's all the proof I need, and I'm sure the old IS has exactly the same thing as the IS250 loan car I had behaved in exactly the same way as my IS200...... :)

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Interesting replies here. thanks everyone. However, the fact remains the hill start assist control only worked for me on the GS300SE-L. None of the others.

The hill I tried it on was a very short piece of private road on the Castle Fraser estate. The hill was very steep, probably 1 in 4. The cars all rolled back about a metre before I applied the brake.

So I guess this means I wouldn't rely on this feature, even if it is in the handbook. In my case I have a weak left foot, so operating the footbrake isn't an easy option for me. However, a quick switch from brake to accelerator, or using the accelerator to hold the car for a short period would work fine. It certainly won't put me off buying a GS one day :)

Next time I'm in the dealers, I'll mention it to the Service Manager......!

Cheers,

IanB :D

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