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another wheel / offset querie

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Guest

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hi guys!

i know this has prob been done to death but i have read the forums previous posts and am still none the wiser.
i have a early 85 944 with teledialswearing 215/60/15 rubbers.
i want to get a set of after market alloys but have no idea where to start,
what are offsets?, what are my offsets?
whats available to me?[&o]
forged? is it a requirement?
spacers? [&o]
best place to buy? london?
please any help in laymans terms would be apreciated!![&o]
 
Well, to start with I'd think you've got 7x15's with 23.3 offset. Clean behind the 'spokes' of the wheel and you'll find one of them cast with the size/offset - see pic. This one is probably what your's will say 7Jx15ET23.3.

The offset is the 23.3 dimension, which is the distance from the true centreline of the rim to the mounting face of wheel. The mounting face is generally out-board of the wheel centre, hence offset (rather then inset, if it was the other way round)

What this does is put the centreline of the wheel pretty much in line with the centreline of the wheel bearing arrangement, hence no side loading of the bearings. Because the bearings/hubs/discs etc all take space the mounting face is further out than the bearing (obviously, otherwise the bearing would be in thin air), hence the wheel rim is set back to put the load on the tyre (and wheel) back over the bearing. Hope that makes some sense - Fen (I think) posted a sectional view recently which will help - if I could find it [:mad:]

DE5CDFF8B6E243F1A41F0D48BDC14853.jpg
 
Offset is the difference between the centreline through the wheel (i.e. midpoint between the inside and outside edge of the rim where the tyre sits) and the face that meets the hub when the wheel is mounted. In most applications the mounting face is further out than the true centreline of the wheel and this is described as a negative offset. Such offsets are frequently written ET## where the ## represents a number corresponding the difference between the mounting face and the centreline in mm.[FONT=verdana,geneva"] [FONT=verdana,geneva"]The offset on your car, which being pre-'87 has the earlier non-ABS style hubs, is of the order of ET23 or 23mm. Later cars with the ABS style hubs (even if they didn't actually have ABS) use offsets between ET52 and ET63 or so.[FONT=verdana,geneva"] [FONT=verdana,geneva"]What that means is that fitting the same wheel to an early and a late car will result in it being something like 30mm further under the arch on an early car than a late one. Therefore if you have an early car you can fit late wheels with a spacer of around 30mm to put the wheel back where it would be in the arch of a later car. It is not so easily possible to run early wheels on a late car as they will stick out of the wheelarch around 30mm more than they should and would likely foul the arch lip unless they are very narrow.[FONT=verdana,geneva"] [FONT=verdana,geneva"]Most (in fact probably all) genuine Porsche wheels of 17" and bigger diameter will be for cars with the later hubs i.e. would need spacers to fit an early 944. Aftermarket or replica wheels are available with the correct offset for early cars.[FONT=verdana,geneva"] [FONT=verdana,geneva"]In terms of forged or otherwise it is just a way of making a wheel, cast being the main alternative. Forged wheels tend to be lighter as they are inherently stonger for a given weight, but there is no need to stick with forged wheels. In fact aside Fuchs (which only fit early 944's) and the "Silver Rose" style I'm not sure you would be able to find forged wheels that you could use.[FONT=verdana,geneva"] [FONT=verdana,geneva"]The other thing you need to know to ensure they will fit is the PCD (pitch circle diameter) which the 944 shares with air-cooled VW's and is 5x130, meaning 5 studs arranged in a circle with a radius of 130mm.[FONT=verdana,geneva"] [FONT=verdana,geneva"]Lastly the hole in the centre of the wheel is what locates it on the hub so you need to make sure it is the same size as the hub centre. I don't know the OE size from the top of my head, but I believe (someone jump in if I'm wrong) all Porsches have the same. Aftermarket wheel manufacturers can supply spigot ring adaptors if the hole in the wheel is bigger than the centre of the hub.[FONT=verdana,geneva"]
 
To follow up on a couple of your other questions, although I'm no expert on what is available, I'd suggest...

Forged - yes, you could but I don't think there are that many about (I know some were but not sure which) and it's not a 'requirement' - anyone else - confirm or tell me I'm a twit [:D]

Most wheels are commonly for the later (deeper offset) cars which had 53.3 offset when the hubs became wider due to the addition of ABS. You'll probably find a wider (sorry [&:] ) choice, but will need corresponding spacers (30mm) to move the wheel back out to the correct position. 2 reasons, one - it will bring the wheel load back over the bearing, and two, it will look really stupid with the wheels pushed 30mm further into the wheel arches. These are available, but budget about £100 for a pair (I think, haven't looked for a long time). They come up on e-bay occassionally for less than that.

Phil
 
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