I had a good look at it on my Avant and it doesn't look like it suppose to be an extension to the body to hide the wheel. Looking directly from the top the wheel is hidden within the wheel arch. The plastic bit is virtually flash with the wheel arch anyway so it wouldn't add much width anyway.
Thanks for confirming that, that rear one must be at a similar height to the front one and in my mind serve the same purpose, which is to prevent paint work damage from flying debris. I might have misjudged the orientation of it when compared with the front one on your S4, by it must work okay "that way" round - unless the upper end has the same slopping/tapered profile, can you check up on that some time please. How that shape fits in with fitting rear mud flaps still remains a problem for me to get to grips with.
This could herald the start of many people buying in this new stone deflectors and retro fitting them to earlier/other cars to reduce stone damage further, okay earlier/other cars will not have the holes to accept them, but their is heavy duty double sided sticky tape available to hold them in place. The main issue for the front wheel arches I think, was that there is a section of wheel arch body work that is flat and folded in at right angles and used to support any mud flaps fitted, and it was that flat section mainly that required this extra protection, the rear wheel arches I think, don't have that folded section so maybe it is just the "thin" area and the body work behind that needs protecting when fitting wider wheels/tyres.
Edit:-maybe the rear mud flaps are fitted to a different way to the rear wheel arches, I have never fitted mud flaps to my S4 so can't comment on that - if so then that will be why the profile of these rear deflector is different.
Out of curiosity, what car do you have? I only ask because although you mention an S4 I don't imagine that you have a B9 S4 so that you can go take a look at them?
The front ones are longer and extend right to the bottom of the arch as I'd expect if you were trying to protect the paint from stones. The rear is all the way up where the bumper meets the arch so wouldn't protect the arch from stone damage anyway, not at the point where my B8.5 showed the most damage anyway. So your first sentence is wrong I'm afraid, the rear is nowhere near the same height as the front. I looked down at mine and that piece of plastic does in fact obscure part of the tyre that would otherwise be visible just where the bodywork starts to taper in behind it. Granted I don't think that you'd be able to see it without having spacers on, but it proves the theory.
Lastly, the interview about the Megane was with an engineer that worked on the car if I remember rightly, it wasn't just a sales guy. So, as an engineer, I will listen to the person who actually designed that specific part of the car and take his word for it.
It is a B8 S4 that I have, hence the need for me to retro fit these stone deflectors to try to hold back any more damage to the rear folded section of the front wheel arches.
In respect of the extensions built into the Megane RS, I thought that I covered that quite clearly as yes they will be mainly functional, like they are on Focus RS when it reappears, I just happen to be an engineer as well so I do, like you question things until I find out the correct answer.
Remember one thing, even on that Megane RS, these extensions, in reality would not need to show as much as they do in relation to the general flow of the body work, but that is part and parcel of selling/styling a performance version of a car, just like comparing the performance version of an Audi S4 which as you know is an RS4 - difference boldly placed does improve the owner's feel good factor, and why not!
Yes this is going on a very long way for something as simple as stone deflectors, but if others are not interested in this thread they can avoid reading any new postings.
If you look at a car passing through water you see that the spray kicks up very high up the tyre as the tread displaces it from the road. I am not convinced these are actually stone guards at all but to reduce water spray..I'm just wondering if you're thinking that the rears are in a different position than they're actually in is all? Do these stone guards for your car not fit at the bottom of the arch as you've described with the folded section? Rather than halfway up the arch where they won't actually help stone damage?
They're not really protecting much either since the only section that would be exposed if it isn't there is a 2mm thick bit of sheet metal that makes up the rear quarter.
Ok, so we're not really getting closer to determining the answer to what the OP was actually asking. Why are these trims (whatever they are) on an S4 but not on an A4?
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Who has these bits of trim and who doesn't? What are the variables at play?
What wheels do you have on your car? If it has the wider versions/ones with lower offset it would support my thoughts I guess if compared to the standard wheels?
I've got the 19" 5V spoke matt and diamond cut RS style alloys they are 8.5 inch width and ET40.
Also have sports suspension which is supposed to be 20mm lower than standard.
Are they not for 19" wheels and above? As in my links?Ok, so we're not really getting closer to determining the answer to what the OP was actually asking. Why are these trims (whatever they are) on an S4 but not on an A4?
I have them on my A4 so they aren't exclusive to the S4.
Mine was built in April 2016, so don't think they are to do with only later models having them.
The OP has compared 2 cars, both with 245 width tyres so may not be to do with tyre protrusion after all.
My A4 sits on the lowered sports suspension. Maybe this alters the position of the wheel in the arch sufficiently to require the trim if it is to do with tyre protrusion.
My A4 is quattro, as is the S4. Maybe the rear wheels being driven requires the trim if it is for stone deflection.
If it was for water spray reduction, wouldn't all cars have it?
Who has these bits of trim and who doesn't? What are the variables at play?
Are they not for 19" wheels and above? As in my links?
tbh, what you are saying makes perfect sense to me but rum4mo raises an alternative purpose and it would be good to be able to definitively rule it in or out.
So, who has a quattro A4 or S4 without these trims on the rear wheel arch and what is your wheel size?
Who has a non-quattro A4 or S4 with these trims on the rear wheel arch and what is your wheel size?
In both cases, what suspension do you have as well?
(The matters of great importance idle minds can find to discuss on the internet!)
tbh, what you are saying makes perfect sense to me but rum4mo raises an alternative purposeNot really, they are only just spray guards for 19" sized wheels, end of story as far as I am concerned. My links to the S3's with and without 19" wheels confirm this. Plus our 2013 fiesta had them, and I think that had 16" wheels, also wider than the body was originally designed to take.
tbh, what you are saying makes perfect sense to me but rum4mo raises an alternative purpose and it would be good to be able to definitively rule it in or out.
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(The matters of great importance idle minds can find to discuss on the internet!)
I'm with Grumpz, except my car isn't quattro.
I also stick by what I said back in post 2 (legislation around wheels/tyres in relation to bodywork) and what others have confirmed already.
Amazed some are still trying to find a different explanation.
I think they are being made more technical by some than for what they're intended....I have an A4 quattro with 19's.
I also have these plastic parts.
I don't really care what they're for or what the correct name for them is.