offsets

[xaftershockx]

Ok Ok this is me being really lazy or very sensible depending on how you look at it!!

Where do I look to see what the wheel offset is on my car?

I narrowly avoided buying some wheels off e-bay that wouldn't have fitted! Phew .. cheers Paul!

See I could spend hours pouring over the car and leafing through all the reams of paperwork but!!

You guys can answer the question in minutes!! CHEERS!! in advance!

 

[Diver944]

If you have genuine Porsche wheels from D90 onwards the offset and wheel width is stamped either side of the tyre valve, ie 8 and 55 for an 8 inch wheel with 55 offset

Use this calculator to determine the difference if you use a different wheel:

http://www.1010tires.com/WheelOffsetCalculator.asp

 

[Diver944]

Oh and this site lists all the standard sizes for a 944:

http://members.rennlist.com/951_racerx/WheelsFAQ-StockSizes.html

 

[Riverside]

The wheel dimensions are cast into it either on the back of one of the spokes (my clubsports are like this) or on the rim next to the air valve. The offset is described as ET (ie ET23). Alternatively if you can find the Porsche part number you can use that to look up the spec of that 'part' with PET. If the wheel is corroded or refurbed they may be difficult to find/read.

You can work it out with a tape measure if you know where to measure from (helps if you already know the width) and do a bit of maths. The rim width (and diameter) is measured from bead seat to bead seat rather than edge to edge. Take half the rim width (converted from inches to mm) away from the distance from the back bead to the hub face.

 

[xaftershockx]

Its a tad dark now I'll investigate this simple task in the daylight!!

Watch this space!

 

[333pg333]

ORIGINAL: Diver944

If you have genuine Porsche wheels from D90 onwards the offset and wheel width is stamped either side of the tyre valve, ie 8 and 55 for an 8 inch wheel with 55 offset

Use this calculator to determine the difference if you use a different wheel:

http://www.1010tires.com/WheelOffsetCalculator.asp

I've tried to use that calculator before Paul and what I don't get is it seems to want you to know what your offsets would be if you chose another sized wheel. Maybe I'm not using it correctly, but I would think that if you were to modify our bodywork to accept a larger wheel size then the only way is out further. So with this in mind why can't I put in my old wheel size, then my projected new size and it gives me what offset I need? Rather it seems that you have to tell it what offset you want with your new wheels. Maybe I'm just stupid but I don't get it?
For example. I want to go up to 11's on the front and 12's on the rear when I do the bodykit later this year. How do I determine what offsets I'll need to order the wheels?
Cheers
Patrick

 

[Diver944]

Its to determine the new position of new wheels with different offsets.

For example if you currently have an 8 inch wheel with 55 offset and are thinking of buying a 9 inch wheel with 65 offset, the calculator reveals you will have 23mm less clearance at the inside edge of the wheel and 3mm less at the outside edge.

In your case you are ordering custom wheels (I think) so will just have to keep experimenting by adding a mm at a time until the numbers fit inside your extended arches

 

[333pg333]

Yes that's the rub. It makes it a bit difficult to do until you've got all the fenders in place of course. I guess with the wheels not being able to go any further inwards you can just calculate the extra mm's by converting the inches and just adjust the offset?

 

[944 man]

16mm is WAY sticky-out: are you sure? Front seven inch rims Id expect to be ET23mm, so 15mm-17mm spacers will make them right.

 

[Frenchy]

Thanks 944 man.....DOH got it wrong, i am looking to buy some 17" Fuch Reps the rears are et16 which are the same as my 17" cup reps et16 so that's ok
The front Cups are et23 but the sellers fronts are et40 will they stick in/out 17 mm, will they fit ?
Early 86 turbo BTW

 

[rcsalmons]

Jim

What are the wheel widths - old and new?

Rich

 

[Frenchy]

Rich
New ones are 7.5 font 9 rears, existing ones 9 rears and unsure about the fronts as they are down at my other garage 7 or 7.5 ?
I have a feeling that they will be 7.5 as they are fitted with 225 rubber.
Jim.

 

[944 man]

Theyll be too far in by 17mm; but this assumes that theyre 7"s wide. you add or subtract 12.5mm for every one inch of rim.

 

[DivineE]

So long as its that way round I've used spacers before on other cars to fit different offset wheels and didn't find any problems. (except I had to use longer wheel studs which I'm not sure how you'd do with a 944 as they're the other way round? Do they unscrew from the hub?)

 

[Frenchy]

The new ones are 7.5 ET 40 as opposed to 7.5 ET 23 exsisting so a 17mm spacer is needed ? though if originals are 7 a 6mm would sort it..............corecto mundo ?

Edited due to Shiraz !

Originals are 7 x ET23 new ones 7.5 x ET40 gain 6mm due to rim width difference of half an inch, so ET now equivalent to ET29 Leaving 11mm difference so a spacer of 10mm will get them as near as damn it ?

 

[Frenchy]

Ben,
You will be ok with 6/7 shims to use exsisting nuts, i have them on the rear of my 220, after that you need correct spacers which bolt on to the hub via studs, the new spacers in turn are fitted with other studs at the correct PCD the bolts used for bolting to the existing hub sit flush as it is a short nut in a countersunk hole.......make sense ?

 

[DivineE]

Yes. Neat trick but I assume you have to cut the studs or you'd be a long way out so that makes it a permanent decision to use those wheels... not that thats a bad thing with a set of Fuchs[]

 

[Frenchy]

Ben,
Nah, the spacers are a 5 minute job to unbolt, not a permanent fix,you bolt the spacers to the existing studs, the spacers carry a second set of studs to bolt to, these Fuch are replicas but come in 17".
Pretty sure the car would look the mutts with these on,polished dishes and black centres, not to sure about the quality though, do not think they will be anywhere near Fuch quality, read on the web that no real problems but some run out issues.