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Adaptive Cruise... Anyone Else Tried It?


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I have adaptive cruise on my IS250. Anyone else got it fitted on theirs, or tried it?

Mine has a curious issue- occasionally it picks up vehicles, especially lorries/vans, in the left lanes that you are overtaking. The result is that the car brakes hard to match the speed of the truck for no apparent reason (which could cause all sorts of probs with a car that is following 2 feet from the my rear bumper!). It doesn't always happen, and happens more frequently on right hand bends, even very gentle ones. Other than that, it generally works brilliantly and is really great in congested 30+mph traffic.

What I would like to know is- does anyone else's do this? Is mine faulty, or is it just an operational quirk that inevitably happens if an object is in the radar's line of sight as it would be when passing a wide vehicle on a slight bend? Surely they'd have thought of that? Maybe not...

I've had it looked at and adjusted a number of times by the dealer who have suggested they consult Lexus technical help if I'm not happy. I just need to know if mines faulty, or if I'm expecting it to work perfectly when in reality it simply doesn't.

Any ideas gratefully received.

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I've tried it on a test drive in the past and I thought it was awesome! Definitely a must have for my next car...........

Didn't try it on any right hand bends, but can understand why it would do that, until they make the radar beam turn with the wheels (like adaptive headlights) I'd assume this is just the way it will work, as on a bend it will think there is an obstacle in front of the car.........

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I have never heard of a so-called safety feature which could be so potentially lethal. Presumably it will do the same on a left hand bend if you on the inside lane. We have to trust mechanical devices to drive anywhere. The less we leave in the trust of electronics, the better.

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It generally works fine- it is easily over-ridden with a gentle press on the accelerator which gives you total control again (e.g so you can close a gap more than the system would normally allow while you wait for someone to pass you without losing speed)

You can of course switch the adaptive bit off, and just have normal cruise.

On the whole its great, and I'd miss it, especially in heavy traffic. Its just that "lorry on a slight right hand bend" business that's a bit unsettling, and intermittent which leads me to think its just my unit.

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Its just that "lorry on a slight right hand bend" business that's a bit unsettling, and intermittent which leads me to think its just my unit.

I use mine at every opportunity and have'nt come across the problem - perhaps I just use too many straight roads!

I can certainly see the logic of radar only pointing straight ahead so I'm going to make a conscious effort to replicate the situation and will post accordingly.

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Its just that "lorry on a slight right hand bend" business that's a bit unsettling, and intermittent which leads me to think its just my unit.

I use mine at every opportunity and have'nt come across the problem - perhaps I just use too many straight roads!

I can certainly see the logic of radar only pointing straight ahead so I'm going to make a conscious effort to replicate the situation and will post accordingly.

Never experienced that problem on bendy roads, in fact national speed limit "A" roads are my favorite place to use mine. I set the speed higher

than the cars in front, and then sit back and let them do all the work of braking for bends and slowing for speed cameras. I do wish there was a

way to lower the speed at which it deactivates to say 10- 15mph as this would be allow you to use it alot more on local 30mph roads.

One problem I do have is on motorways etc if im going 10-20 miles above speed limit with a clear strech of road in front, when I start to come up

on a car in front it seems to take too long to begin slowing down and then has to brake harder as a result. Often think the car following behind me

must think im a crap driver as he then also brakes harder only to see me accelerate away once path is clear and then do the same thing with the

next car ahead. Not sure if this is just how it is on the I.S model coz the hybrid I had on loan worked flawlessly.

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The systems on BMW, Merc have a traffic stop-go mode which would be great too. Its always a bit disappointing when it deactivates at under 30mph...

Thanks guys- Mmmmm ISF.

I'd be very interested to hear if you manage to replicate the problem. I use the M40 very regularly, which is hardly the col de turini. A truck on even the most mild of motorway bends can upset it when its playing up. Sounds more and more like mine's faulty.

Someone has pm'd me to let me know the potential cost of replacing the unit under warranty which perhaps explains the dealer's forlorn hopes so far that a set-up might do the trick!

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The systems on BMW, Merc have a traffic stop-go mode which would be great too. Its always a bit disappointing when it deactivates at under 30mph...

Thanks guys- Mmmmm ISF.

I'd be very interested to hear if you manage to replicate the problem. I use the M40 very regularly, which is hardly the col de turini. A truck on even the most mild of motorway bends can upset it when its playing up. Sounds more and more like mine's faulty.

Someone has pm'd me to let me know the potential cost of replacing the unit under warranty which perhaps explains the dealer's forlorn hopes so far that a set-up might do the trick!

I've used Adaptive Cruise for the past three years and think it is just great. Heavy motorway traffic is a breese when using it with the full distance setting on. How do you switch it to normal cruise, I seem to remember seeing this in the manual but could not get it to work.

As to picking up wagons or other vehilcles on bends, this is normal. I did ask Chester Lexus if they could adjust the beam to a more narrow setting so as to overcome this but they said that was not possible.

Still the best add-on I have ever used, and I hope it is on the RX 450 that I'm going to get later in the year.

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Adaptive Cruise sounds like one of the most potentially terrifying devices ever fitted to a car. Tailgating is bad enough to deal with. Aggravating the situation can only make it worse as it will upset the aggresive driver behind you making an accident even more likely. Having said that I have never used it and am only speaking from perception not experience.

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I've used Adaptive Cruise for the past three years and think it is just great. Heavy motorway traffic is a breese when using it with the full distance setting on. How do you switch it to normal cruise, I seem to remember seeing this in the manual but could not get it to work.

As to picking up wagons or other vehilcles on bends, this is normal. I did ask Chester Lexus if they could adjust the beam to a more narrow setting so as to overcome this but they said that was not possible.

Still the best add-on I have ever used, and I hope it is on the RX 450 that I'm going to get later in the year.

I think you push the cruise lever forward and then you can change the mode to normal.

Interesting- seems the occasional braking bit around corners is normal. I can tell when it might do it, so I usually gently press the throttle in those situations to take over control for a second so it doesn't matter really. As you say, in heavy traffic, and most of the time its brilliant- well worth getting if you can...

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I use the M40 very regularly, which is hardly the col de turini.

Assuming that's a reference to the photo of my Rapier then it's bloody well spotted!

I've tried really hard over the last few days to replicate the situation you describe (bends with trucks on the inside lane) and haven't really found it to cause problems - I can understand the logic of the radar pointing in the direction the car is heading but it needs to be an awful coincidence for the angles/distances/speed to all gang up together to cut the cruise......

BUT yesterday I found a situation that the system really couldn't cope with - lots of snow/spray on the M1 was tackled fine unless there was traffic in all three lanes travelling at much the same speed at which point a message appeared stating that "cruise is not available"! It could be re-set once at least one lane cleared away and would last until the next similar situation - I ended up changing to the non-auto mode and all was well.

Perhaps therefore your system may need some TLC from a friendly dealer tecchy!

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Adaptive Cruise sounds like one of the most potentially terrifying devices ever fitted to a car.

Not so!

Providing you don't fall into the "sleepy" trap it's brilliant!

The M1 is being updated to four lanes around where I'm based so it's 50mph average speed cameras for twenty or so miles and ACC is wonderful - set it to fifty and a bit and you can concentrate fully on the problems associated with narrow lanes and aggressive white van men content in the knowledge that the electronics are doing a far better job of optimising throttle control (and thus fuel efficiency) than most humans would manage.

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I use the M40 very regularly, which is hardly the col de turini.

Assuming that's a reference to the photo of my Rapier then it's bloody well spotted!

I've tried really hard over the last few days to replicate the situation you describe (bends with trucks on the inside lane) and haven't really found it to cause problems - I can understand the logic of the radar pointing in the direction the car is heading but it needs to be an awful coincidence for the angles/distances/speed to all gang up together to cut the cruise......

BUT yesterday I found a situation that the system really couldn't cope with - lots of snow/spray on the M1 was tackled fine unless there was traffic in all three lanes travelling at much the same speed at which point a message appeared stating that "cruise is not available"! It could be re-set once at least one lane cleared away and would last until the next similar situation - I ended up changing to the non-auto mode and all was well.

Perhaps therefore your system may need some TLC from a friendly dealer tecchy!

No, hadn't noticed your Rapier pic in the profile, so a happy coincidence! Lovely car though- have you had it long?

The "cruise not available" message comes up when the auto wipers are in 'fast' mode- might this have been the case with you? It's easily defeated by putting them into non-auto mode at the lower speed, assuming you can still see... Snow on the 'L' badge in the grille also gives the same message, plus "pcs not available"

They've checked mine over a few times, and done some realignments according to Lexus service procedure involving cones and bits of rope apparently and have given it a clean bill of health. They noted its occasional reaction to high sided vehicles on bends, but say that its working fine as far as they are concerned. They've offered to lend me another car with it fitted to put my mind at rest. Oddly enough, I recently test drove a Range Rover with ACC fitted, and the salesman said that it did the same thing from time to time.

I do agree with your comments though- it does a much better job of maintaining safe distance etc than most drivers (esp Audi and BMW! :whistling: ) and I do love the "gadget" appeal!

Thanks for having a go at replicating the problem though- much appreciated

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  • 2 months later...

I've soldiered on, but am still not convinced mine is working right, mainly because it seems to start playing up intermittently. I had a scare the other day with another driver who got a bit (and understandably) upset when the car slowed in the outside lane reacting to a truck in the middle lane, but on a straight this time.

I've got it back at the dealer to look at it again, and I've asked that they raise it with the powers that be at Lexus to get a definitive answer.

Any other thoughts gratefully received.

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I might do that... only trouble is that its a rare option on the IS's. As luck would have it it's standard on the ISF, may ask for a loan of one of those for a week or so for a proper diagnosis!

Its the intermittent nature of the problem that makes me certain its a fault. Anyway, I've got the dealer on the case now who are being supportive, who now fully understand the problem. I have intimated they may want to get Lexus GB involved as there is a potential road safety issue.

I wouldn't mind so much if I hadn't specially sought a car with ACC out as I do so many m-way miles.

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  • 2 weeks later...

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