944 wheel size/offsets help needed

[poprock]

Wheel offsets, widths etc are a black art to me. I haven’t got a scooby. Can someone help me out?

I’m offered the following from a friend (wheels with tyres already fitted):
Rear - 235/40/R17 90W
Front - 205/40/R17 94V

Are they suitable for a 1987 944 Lux, or shall I tell my friend to pop them on eBay?

[Sean Smallman]

It's the offet that is important, though they do look a bit larger than standard.

[Porsche]

Can't you just have them off your friend to try & see if they will fit before agreeing to buy them?

[poprock]

In the interest of learning more on the subject, what do those figures all mean? Is the offset not mentioned there?

I know the R17 refers to 17" rims with R-rated tyres.

Is the 235/40 referring to overall diameter and tyre thickness, or something? and what are the last part, 90W etc? Are those widths?

Not understanding stuff really bugs me … time to find out.

[tr7v8]

try here:

http://www.etyres.co.uk/glossary-tyre-t ... rm=profile

[poprock]

The aspect ratio of a tyre is the height of the tyre sidewall expressed as a percentage of the tyres width. To understand this more you need to recognise the meaning of the size markings on the sidewall of a tyre.

For instance a typical tyre size used today is 205 / 55 R 16 and this size can be broken down into 3 major areas:

205 - this is the width of the tyre expressed in mm.

55 - the aspect ratio, or profile of the tyre, in this case 55% of the tyre width.

16 - diameter of the rim the tyre is designed to be fitted to (in inches).

In this case the tyre sidewall height would be 113mm (205 x 55%).

It can be stated that the smaller the aspect ratio, the wider the tyre in relation to its height.

Aspect ratios will range from 80 series (eg 175/80R14) all the way down to 25 series (eg 335/25R19).

Excellent, thanks Jim. That explains the main parts, but leaves the last bit: What do the 90W and 94V mean? Any ideas?

[J.J.]

Think thats the speed rating or loading. W is 168mph & V is 149. Both ok for a Lux. (Speed rating should match or exceed the top speed of the car. Bit Acedemic unless you do track days at SPA )

[poprock]

Cheers, that makes sense. So I still need to find out the offsets on these wheels before I know whether they’re suitable for the old girl. Given the number of people who put Boxster wheels onto their 944s, I figure they’ll either go right on or go on with spacers.

[lindsayhbrown]

offset will be marked as ET near valve on gen porsche wheels, on an '87 an ET of between 50 and 65 should be ok

[tr7v8]

Think thats the speed rating or loading. W is 168mph & V is 149. Both ok for a Lux. (Speed rating should match or exceed the top speed of the car. Bit Acedemic unless you do track days at SPA )

To be pedantic the number is the load rating, leightweight sports car or lardy exec saloon. The letter is the speed rating.

As for offset, this will be on the wheel written as ETxx you're looking for around the 50 mark front & back for a late model (post 86) 944. This won't guarantee that they fit but will give you a fighting chance.

[Porsche]

What type of Boxster wheels are they? Lindsay has Boxster wheels fitted to his '44 and may be the same size.

[poprock]

I’ve yet to see the wheels, but I suspect either Cup 1’s or twists.

Basically, here’s the plan: My Lux has suffered somewhat from sitting garaged for six months and needs a little work before I try harder to sell it in the spring. One of the ‘issues’ is that the right rear tyre has gone flat. Must have been a very slow puncture. Rather than shell out for fresh rubber before selling the car, I’m thinking a better idea is to buy these 17" alloys with nice low profile tyres on them, and fit those. For not much more money than two brand-new rear tyres, I then end up with my lovely 3-piece split-rims to keep in my garage or sell separately at a later date.

[lindsayhbrown]

What type of Boxster wheels are they? Lindsay has Boxster wheels fitted to his '44 and may be the same size.

sorry the're 968 coupe wheels 16" and all have ET 52