Becuase the rear wheels are rotating in a different direction to the front.
Eh???
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I think it's down to scuttle plate alignment
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Lee
Having a Fabialous time.
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Some makes of pad are far far worse tahn others, so maybe you have dirty on the back and clean ones on the front?
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Ignoring RF's crazy talk, it probably is just muck thrown up by the front wheels being sprayed over the rear of the car.
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Interesting, Andrew-T. What car is it? The front wheels get dirty more quickly on all three of my cars -- MB E320 Coupé, Golf VR6 and Capri 2.8i.
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Seriously tho, its very interesting to see the dirt patterns on cars. Even look at a car after its just driven through rain. Gives a really good idea of how the aerodynamics are at work here, assuming that less dirt/water stuck to car indicates fast moving low pressure air, and more dirt/water means low(er) speed high pressure air. I would guess that a low speed/high pressure area is centered around the rear wheels and being sucked in by the rear wheels.
The laguna now has some lovely air flow patterns in the dirt.
(mainly because RF junior has now found a girlfriend and wont wash the car)
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The laguna now has some lovely air flow patterns in the dirt.
Could that have something to do with the rear wheels rotating in a different direction to the front wheels? ;o)
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Nope - when the l/h wheels rotate in a different direction to the r/h wheels.
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RF may have hit on a good idea though. If the wheels were made like fans, and handed for the the appropriate direction of rotation, then they could be made to suck the pad dust inwards rather than blow it outwards over the wheels.
I have seen advertisements for plastic disks for fitting just inside the wheels, to stop brake dust. Are they still available?
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RF may have hit on a good idea though. If the wheels were made like fans, and handed for the the appropriate direction of rotation, then they could be made to suck the pad dust inwards rather than blow it outwards over the wheels. I have seen advertisements for plastic disks for fitting just inside the wheels, to stop brake dust. Are they still available?
1/ Escort RS Turbo's circa 1986 had turbine pattern wheels which were not rotationally symetrical, it was claimed that they helped to cool the brakes, therefore the air was sucked through the wheel from the outside on one side of the car and from the inside on the other.
2/ Re plastic discs stopping brake dust - dangerous, reduces cooling of the brakes.
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RF may have hit on a good idea though. If the wheels were made like fans, and handed for the the appropriate direction of rotation, then they could be made to suck the pad dust inwards rather than blow it outwards over the wheels.
1/ Escort RS Turbo's circa 1986 had turbine pattern wheels which were not rotationally symetrical, it was claimed that they helped to cool the brakes, therefore the air was sucked through the wheel from the outside on one side of the car and from the inside on the other.
I can see the advantage of sucking inwards - but why not on both sides? I can see no advantage to the Escort scheme other than to the manufacturer having to make only one mold for left and right wheels.
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I can see no advantage to the Escort scheme other than to the manufacturer having to make only one mold for left and right wheels.
Precicely
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In response to Roger and Cliff: the car is a 306 HDi, and the wheels are standard 6-spoke alloys which are symmetrical to fore and aft rotation. Front brakes are Lucas/Girlings and the rears Bendix-type, all on original materials at 40K, so I don't think that is the cause of any variation.
I assumed that muck on the rears had been thrown up by the fronts, but then a good deal is thrown up by cars in front anyway, so it must be due to air-flow patterns.
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Who can recommend a good cleaner for alloys?
My car's wheels have, over a period of time accummulated some persistent stains, that normal cleaner can't shift.
I think (hope) that this is in the spirit of the thread.
drbe
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I find Wonderwheels very good. It's strong stuff though, so I don't use it too often and try to rinse well afterwards. I have also used Turtle Wax wheel protector afterwards to act as a barrier to the dust - it's not bad, but nothing as outstanding as Wonderwheels.
I've heard some people swear by 'green' brake pads. I've never tried them - never actually seen them in the shops, but perhaps you'd have to go asking for them!
Graeme
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Green stuff. see
www.ebcbrakes.com/Automotive.html
I always use Polycell brush restorer to clean alloy wheels and to get tar off.
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I found that using Wonderwheels (or was it Autoglym wheel cleaner?) got them clean in the first place, then a couple of coatings of "Extra Gloss Protection" has meant that dirt/brake dust doesn't stick so much and they just need a quick wash to keep them clean.
I have also noted that most(?) alloys have a sort of propellor pattern which means that they must draw in air on one side of the car and expel it on the other. Wonder if it has an effect on brake cooling or does the forward motion of the car mean it is irrelevant anyway? Some alloys are "symmetrical" - ie not propellor effect - those on my wifes Xantia for example.
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I agree that Wonderwheels is excellent, god knows what it's in it though, smells pretty vile and cuts through everything on the wheels really easily.
The old car got very dirty front wheels, relatively clean rears. Current one exactly the opposite. Could be that I don't drive the new one as fast though.
Then again, the new one was built in mainland Europe, the old one in the UK. Perhaps it's like the water draining in a different direction either side of the equator. You know, British cars fronts foul up, foreign cars, the rears.
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Lee
Having a Fabialous time.
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Wonder wheels is absolutely amazing.
The inside rim of one of my wheels is not absolutely spotless - previously, there was 5 years of muck and grime built up there as I imagine this area was never washed.
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The inside rim of one of my wheels is not absolutely spotless .........
My curiosity has got the better of me ~ why only one wheel? Am I right in thinking that the others are spotless?
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L\'escargot by name, but not by nature.
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I should also have mentioned that I use Wonderwheels on the black plastic 'skirts' on the C5. It's the only thing I've found that cleans off the muck and DOESN'T go back to a 'mucky haze' again when dry. It stays black! Doesn't seem to do the plastic any harm either.
Graeme
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Green stuff. see www.ebcbrakes.com/Automotive.html
>>
I have only experienced Green Stuff pads once (on a track-day MX5) and have never before seen a car with brake dust down the side up to the middle of the doors! I know other people swear thay get less dust with GS pads, but my experience is completely different.
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Jif or Cif as it is now called (the lemon variety makes them smell nice as well!), this is non abrasive so does not harm the laquer, then polish when clean to protect.
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mainly because RF junior has now found a girlfriend and wont
wash the car
Just you wait... you will get your chance when he wants to borrow it. Dad, can I borrow..... NO.
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I'm guessing you meant to say left and right, not front and rear.
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Andrew-T
Echoing RF, I guess your rear wheels are getting dirtier than the front ones because of the same sort of partial vacuum effect that results in the back of my Golf (not its rear wheels) getting filthy very quickly. I recall that in the 1960s my bro-in-law fitted a small fin on each side his Cortina estate's tailgate, which broke up the airflow and kept the back end remarkably clean.
Disks to prevent brake dust getting onto alloys are still available for many but not all cars. I guess that the point made above about the overheating risk is valid in principle, but I wonder how relevant it is to normal driving as opposed to persistently pushing it.
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The back of a car gets dirty relative to the point that the upward airflow (the dirty air that has come under the car) meets the airflow coming over the top of the car. Most estates and hatchbacks such as the Golf get very dirty rear screens because the airflow meeting point is where the roof an tail gate meet howver with regard to saloons and hatches such as the Mondeo, Vectra etc the point the airflow meets is the lip of the boot lid therefore keeping the dirty air away from the rear screen.
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