LenT

I very much agree, John. The speed at which these fins become usefully effective is something I’ve been trying to find out. I would have thought that, for example, wind tunnel smoke tests would provide this data, but I haven’t tracked it down. The nearest I’ve come is to discover that a series of acoustic tests on noise reduction were conducted at 100kmh (62mph) and did produce results that showed the benefits of vortex generators. But I agree with you that the benefits of enhanced stability may only appear at much higher speeds.

I note that currently the Lexus website is offering a set of mud flaps as an accessory, although possibly not for every model. I haven’t checked! So I can imagine that their view may be model specific. I can now quite understand that a badly designed mud flap can disturb the airflow around the back of the car and increase drag - and thus, say, fuel consumption. But of course this introduces the element of trade off. To the designer these factors are significant. To the owner, the immediately obvious benefits of a cleaner car may be more desirable.

Well I bought my 2015 IS250 Premier as a frisky two year-old and it was bereft of flaps. A quick trawl through the Lexus website suggests that the new cars illustrated don’t have them, but of course they may be offered as an extra. Mind you, I notice that some bodywork behind the rear wheels does seem to have fairly extravagant moulding, so maybe that’s the function they serve. I’ve had cars with and without. I’ve fitted sets as an aftermarket afterthought. But in those days (!) having a dirty body was frowned upon in polite circles. Of the more sophisticated areas of auto aerodynamics…we knew nothing. What we did know is that if you found yourself behind an HGV on a wet road - in the days before mud flaps became compulsory- experiencing the odd sphincter-tightening moment was not unknown. As.it happens, I was idly considering fitting a set to my IS250. But if the consensus is that they look awful, then I shan’t bother.

No problem, Renato. I can just about make calls from my mobile phone!!

This is an extract from a Conference Paper presented in June 2005 by Martin Helfer of the Research Institute of Automotive Engineering and Vehicle Engines Stuttgart on General Aspects of Vehicle Aeroacoustics. It discusses the acoustic contribution made by exterior mirrors and the effect of vortex generators. 4.2 Rear View Mirror A great part of aeroacoustic research deals with exterior mirrors. They protrude into zones of high flow speeds and thus pose a particular acoustic problem. The mirror shape is determined to a large degree by design, but functional aspects must also be considered. Measures aiming at acoustic improvement thus concentrate mainly on details such as the depth and form of water gutters, gaps for folding mirrors and mirror cavity drains. Frequently noises here have a tonal character (whistling). Often it is vortex generators which help with such noises. They are positioned in front of the noise source and interfere with its periodicity. Fig. 21 shows two examples. Fig. 21: Vortex generator to avoid tonal noise in the area of two exterior mirrors of production vehicles I have yet to find a definitive speed at which these vortex generators are supposed to be fully effective, but the experiments appear to be conducted at 100km/h (62 mph).

According to the document tracked down by Peter, these are known as ‘aero stabilising fins’. It can be downloaded from the post above yours. Its function and effect is described. One question that still intrigues me is at what speed do these fins become effective?

See post below. It’ll make more sense!!

My apologies Peter. I should have made clear that I think you have solved the original question. These projections are not for spray rejection or width calibration. They are there to create low pressure areas along the bodywork - and undertray- to aid stability at high speeds. Which also explains why Lexus don’t fit mud flaps. They would disrupt the vortex and reduce this effect. Simple.

Outstanding, Peter! I don’t know if you had access to this resource before this post came up, or whether you’ve researched it since, but it’s a valuable contribution to the debate. For example, it explains to me why my Lexus has a small structure by the A-Pillar, just in front of the mirror. Called the ‘Aero Stabilizing Fin’ it creates a vortex that speeds up the airflow along the side of the vehicle’s body. This helps to hold the vehicle body and stabilizes the vehicle at speed – presumably by creating a low pressure area, rather like an airfoil section. Unfortunately this document doesn’t actually feature the moulding that the OP has queried. So surely the question remains: Is it a spray deflector, as a dealer maintained, or is it a structure to change the airflow over the wheels and improve stability at speed? Now if we look again at Page 5 of this document, we see that there is another projecting body at the rear. This also creates a vortex of an accelerated low pressure area that, as shown in fig. D, pushes the airflow against the body and improves the vehicle’s stability. Now if the rear arch projection in question operates in a similar fashion, then it too is creating a vortex that increases the speed of the surrounding air and creates a low pressure area that pushes the airflow against the body to help stabilize it. But surely that is the antithesis of creating an airflow that would direct road spray away from the rear bodywork? Would not creating a low pressure area actually help to direct road spray against the body? So as far as its purpose as a spray deflector goes, I would stand by my earlier comments. Namely: Well if this is indeed the case, then it strikes me that it is basically ineffective! A less dirty rear is still a dirty rear. And if that was its design purpose, then why not mould it onto the front arches as well? And if Lexus designers were serious about reducing road spray distribution over the bodywork, why not just fit mud flaps, which are actually quite effective, and have done with it? After all, they’re quite popular as an aftermarket addition. Unless, of course, further research proves otherwise! 🙂

Well that prompted me to go and take a close look at my rear end…. The top of the wheel arch projects beyond the tyre but the bodywork does then sweep in as it goes back, until probably about two inches of tyre is exposed. So far more, I would have thought, than would be affected aerodynamically by the small projection behind it. Of course the front wheels are a greater problem because so much more of the wheel is exposed as it is turned. If these tiny projections are aerodynamically effective then do they feature on other Lexus models? Or even other brands? And as I mentioned before, surely mud flaps would be the best solution to road spray over the bodywork. I can envisage this small projection having some aerodynamic effect at, say, 200mph down the Mulsanne Straight, but at 20mph down one of our lanes behind a tractor? Not so much! Perhaps the answer lies within the Lexus design system…if anyone feels intrigued enough to search it out?

That’s certainly my opinion too. It’s many years since we’ve seen extreme winter conditions here in Northamptonshire, so a good ‘all season’ tyre makes more sense for ‘normal’ driving styles. I fitted the original CCs to our small 4x4 when they came out and was delighted with their overall performance. Apparently the latest CC2 version performs even better in comparative road tests. I would have fitted them to the Lexus but my model requires different sizes fore and aft, one of which Michelin didn’t do. My personal priority is wet road performance so instead I chose the then new Goodyear Eagle F1 Asymmetric 5s for the IS250, which have proved to be a very satisfactory choice in terms of handling, grip, noise and overall ride comfort. These days, particularly over the last few months of pandemic, our mileage has been so low that it could be years before I can justify their replacement. And should the weather conditions suddenly become so extreme as to possibly justify a tyre change for the Lexus, then it’s easier for me to just change cars!

Michael, does this model have the double locking feature? If you lock the doors by touching the sensor on the door handle- and then touch it again two or three seconds later - you may hear another locking action. This will be the dead locks activating. The purpose is to render the locks inoperable even if someone breaks a window and tries to open the door by reaching inside.

Well if this is indeed the case, then it strikes me that it is basically ineffective! A less dirty rear is still a dirty rear. And if that was its design purpose, then why not mould it onto the front arches as well? And if Lexus designers were serious about reducing road spray distribution over the bodywork, why not just fit mud flaps, which are actually quite effective, and have done with it? After all, they’re quite popular as an aftermarket addition.

Well it’s an interesting suggestion, Peter, but I would have thought that at normal road speeds the aerodynamic effect of such a small structure would be almost negligible. I rather think that Neil Stephenson may be nearer the mark. It seems more likely to be an ingenious method of complying with overall width regulations regarding bodywork and wheels without actually increasing the width overall!

David, if you believe that the videos did not accurately reflect the true condition of the vehicle, then you might consider that an apology for the misrepresentation is not adequate compensation. This is particularly egregious as it’s committed by a main dealer and reflects badly on the brand. For example, surely something as major as virtually half the car being resprayed might warrant a mention in the description? You might consider a registered letter to the owner of the dealership, headed ‘Without Prejudice’, citing misrepresentation and detailing your dissatisfaction and the costs that you have incurred and requesting compensation. Just a thought….

Spot on, Vladimir. it’s hardly a statistically valid survey, but I too have not had any problems finding petrol or diesel on the relatively few occasions that I’ve gone for my regular fills. Neither have I encountered empty shelves on my occasional forays to the many supermarkets that ring our village. But of course they don’t make good news items. A few days ago on the Radio Four Today programme, one of the crew was interviewing the Manager of a fuel station (possibly BP) and got really excited when she said that at that precise moment they were almost out of fuel. “So you’re having trouble getting supplies!” he suggested. “Oh no!” she said. “In fact we’ve had more deliveries than usual. It’s just that people are putting morel in!” In a later interview a motor trade association rep explained that whereas the normal spend is around £25 a fill, it has now rocketed to over £80. As I heard someone else point out, it’s not ‘panic buying’ when the media and the twitterrarty. are claiming national shortages. Going out to stock up is a rational response. The panic part is when you buy far more than you usually do despite not actually using more than you usually do. Being caught out by unpredicted increases in demand is one of the drawbacks of the otherwise very efficient Just In Time supply system.

Very sorry to hear that you’re having such trouble getting this BlackVue to perform as you want. As I understand it, you bought it from Halfords and fitted it yourself. You then went back to Halfords to get a setting up problem resolved. You then had further problems at which point you contacted ‘BlackVue’ - rather than Halfords - for a solution. Now was this a BlackVue agent, a retailer or Pittasoft themselves? Frankly, how interested an agent might be in a unit bought from Halfords is questionable. On the other hand, you may well have already discovered the outer limits of Halfords’ technical knowledge. I wonder if you have considered approaching the manufacturer, Pittasoft. They operate a Help resource which might be a useful place to start. https://blackvue.com/blackvue-help-center-how-can-we-help-you/

And did you get a satisfying ‘Gotchya’ feeling? I know I do! Another favourite around here is cars approaching roundabouts in the left lane of the dual carriageway - and then turning right without warning. On a lighter note, I have several movies of a family of ducks crossing Silverstone High Street. And even a couple of chickens crossing the road - although I never did find out why.

I fear we may have let Djedji down. It would appear that none of the suggestions found favour. So what could account for this one-off post and then silence? I do hope the answer doesn’t turn out to be….Pacemaker. 🙁

DOH! Carers !!!!

And what is your point, exactly? This Sphinx, for that is what it appears to be, is a natural genetic variation which I understand is very popular with owners. It is renowned for its intelligence, curiosity, affectionate nature and the close relationship it forms with its human careers. It clearly appeals to those who appreciate that beauty is more than hairless skin deep. 😊

I appreciate that for some this is not a joking matter. But I am concerned that some posters are being tempted to make wild and intemperate accusations that detract from the potential seriousness of this problem. So let me just point out that, in my extensive experience of the subject, there is no such thing as an ‘ugly’ cat.

A chance to recycle Pam Ayers, me thinks… I think that I may take a stroll And buy myself a toilet roll. At home it will be safely stowed With the other pallet load.

I very much doubt, Jon, that you can find any respectable tyre maker who would agree that mixing tyre types is a good idea. People do it and get away with it. Until the day that they don’t! Michelin has just introduced the CC 2, and this is one of the reviews you might find interesting.

Yes, John. As I think you suggest, it raises the question of how much of the original oil actually remains after 100K miles? Which rather reminds me of the workman's old broom....