Hey guys,

I've noticed this a few times and thought I'd get your opinion on the matter, I noticed that when there is any form of wet on the road the yeti has a way of throwing it on to the rear window, it's a strange thing even if there's a tiny amount of water on the road it does it.

Today it's been really heavy rain in west Yorkshire and more than ever I noticed that you pretty much have to drive with rear wiper on, I'm wondering if anyone who has the mudflaps fitted has any knowledge of this curing it?

This brings me to another question when it's raining heavy like today the rear wipers seemed to be coming on automatically, does the yeti have rear screen rain sensors?

Thanks in advance all.

Any square shaped rear car will end up with a mucky rear window due to the aerodynamics. The shape causes a low pressure area immediately behind the car, so any water from the rear wheels is "sucked" up into this area. The rear mudflaps stop it a bit, but not much.

The rear wipers are "linked" to the front wipers, so that if the fronts are on continuous the rears will wipe every certain numbers of wipes. It can be altered in the Maxidot menus, however I find it very useful.

Coming to work this morning I think I would have been better off in a boat!!

Our ex-demo car already had mudflaps fitted and I can confirm they do not prevent this problem.

I've used Rain X on the rear screen which does improve rear vision.

IIRC the rear wiper only comes into play when the front wipers are on continuous and your speed is above 30mph ?

Hi all,

Years ago, I have driven a Fiat Uno and a facelifted VW Polo Mk3, both of them with a near-vertical rear window and both had this behaviour: when it was raining, getting over 70-80 km/h the rear window became more and more drop-filled

Now I drive a Smart ForTwo Mk2 (owned by my wife) and although it has an even more vertical rear window, its rounded side edges makes it a bit less prone to drop-catching at high speeds (it starts at about 80-90 km/h).

We are getting our new Yeti this Saturday, so I cannot tell by experience yet, but as its rear is more boxy I suppose it will get more drops at medium and high speeds. Fortunatelly, it has automatic wipers so this is not an inconvenience for me

Kind regards.

Edited 19 April, 201214 yr by Transfesa

Some while ago I remember someone posting a picture of their Yeti with an aftermarket 'spoiler 'recently fitted above the rear window which he hoped would help eliminate or at least reduce the problem. He promised to report back on his experience in due course. I've not seen any follow up report, so not sure if he's provided one, but it would be interesting to know?

I've noticed that winter tyres, because they're efficient at clearing the surface water, create far more gunk on the back window.

Before I fitted the Contis I had never worried about the level f rear window contamination and it certainly was never ever as bad as a golf I had years ago.

Yeah the boot of my yeti is always covered in mud and general road dirt from what the tyres kick up.

I really did think the mud flaps would cure this.

Anyway thanks for all your help.

Some while ago I remember someone posting a picture of their Yeti with an aftermarket 'spoiler 'recently fitted above the rear window which he hoped would help eliminate or at least reduce the problem. He promised to report back on his experience in due course. I've not seen any follow up report, so not sure if he's provided one, but it would be interesting to know?

That will increase the drag, though.

Chris

I've used Rain X on the rear screen which does improve rear vision.

Rain X is great. I use it on windscreen, rear window, lights and mirrors.

Chris

That will increase the drag, though.

Chris

Not neccessarily. The spoiler in question fitted to the body above the rear hatch, flush with the roof, but sticking out rearwards. If it reduced the rear low pressure area significantly it could actually do the opposite.

Have a look at Kahm style tails as an example.

IIRC the rear wiper only comes into play when the front wipers are on continuous and your speed is above 30mph ?

According to the manual, if the windscreen wiper switch is in one of the continuous wipe positions then the rear window wiper automatically does a wipe every 30 seconds, or 10 seconds at speeds above 5 km/h. If you have the rain sensor then the rear window wiper will also wipe automatically like this if it's raining heavily enough for the front windscreen wipers to be wiping continuously under automatic control.

Edited 19 April, 201214 yr by ejstubbs

Not neccessarily. The spoiler in question fitted to the body above the rear hatch, flush with the roof, but sticking out rearwards. If it reduced the rear low pressure area significantly it could actually do the opposite.

Have a look at Kahm style tails as an example.

Well, I'm a pilot but not an expert on aerodynamics :-). I'd work on the assumption that anything protruding into the airflow would induce form drag; and anything that produced lift (up or down) would induce drag. I had a Trooper when stationed in Florida some years ago; that had a spoiler over the rear edge of the roof, angled to reduce the updraught that produces spray on the rear window. I reckon that increased the drag quite a bit, but that's not the shape you are suggesting.

Connected with that (sort of), I remember reading about the shape of cars and how a square back reduces drag over a more smoothed down back, because of the turbulence such a shape causes behind the vehicle as it moves.

But I'm not sure how that would work with a spoiler. Someone will have to try it . . .

Chris

System at work has allowed me a little "play".

One of the spoilers in question:

http://www.superskoda.com/Skoda/Yeti/Skoda-Yeti-roof-spoiler-SPORTIVE-by-KI-R-TÜV-version

They do a couple of other very similar ones.

Your description of the squared tail is the Kahm Effect.

I think 'spoiler' is just a wrong word for that device [uPD: sorry, not the one from the link above ]. I'd call it a deflector because its main purpose is to deflect an airflow, not necessarily spoil it (making it turbulent). In aviation they use spoilers to reduce unneeded lift e.g. during landing. As for drag, spoilers can both reduce and increase it, depending on other factors. It is usually better to have laminar flow to minimize drag. But in some cases laminar flow can make more vortex drag (also making unwanted lift) compared to turbulent one. In the latter case a proper spoiler would reduce drag.

But to reduce rear screen contamination one would want laminar airflow over it.

Edited 19 April, 201214 yr by briskycat

Superskoda call it a spoiler!

I shall stick with their description.

I meant something like this:

the mud flaps are to small to stop the spray up the back window, but have read this on anther forum and may give it a try.

I paid £12.00 for some polypropylene sheet and fitted them myself, easy peasy, mine are now 3" longer and keep the rear window clear

System at work has allowed me a little "play".

One of the spoilers in question:

http://www.superskod...I-R-TÜV-version

They do a couple of other very similar ones.

Your description of the squared tail is the Kahm Effect.

Very pretty. I'd make a mess of fitting it, though.

Chris

I meant something like this:

Nice as well, but I reckon that that's going to increase the drag.

I wonder if I can make mine 3" longer? It would make all the difference I'm sure

BOB corner now 1 minute for every year of you age

BOB corner now 1 minute for every year of you age

Don't you start! It's bad enough Graham always sending me to the corner!

Don't you start! It's bad enough Graham always sending me to the corner!

I'm sure Graham will be along to make sure you stay there for the correct amount of time