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What wheels do I need?

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I need to buy some new wheels for my Westfield. What offset / stud pattern do I need?

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For 15 inch wheels for a current SEiW, Westfield say they fit 7Jx15, 4x108pcd (Ford 4 stud pattern), with an offset of et+35 as standard.

If you want though to have the wheels slightly in towards the car body then a greater offset e.g. et+38 (3mm narrower track each side w.r.t. et35 wheels) would do, or if your wheel arches/cycle wings allow, then some people run a smaller offset e.g. et+23, to get an extra 12mm wide track each side.

Spacers can also be used to adjust the + offset (i.e. how far the wheel mounting flange is spaced outwards w.r.t. the centre line of the wheel) if the wheels you want do not come in the desired offset. For example if you need an et +35, then you can buy an et+40 wheel and use a 5mm spacer, bringing the offset back to +35 (i.e. 40-5).

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Hi, Interesting post, Sycho you clearly know your stuff! But how do I go about measuring my current PCD? I've got an early narrow body, with what I believe, early ford stud patterns but would like to check before I buy some new wheels. Thanks in advance!

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with a ruler;

 

pcd.JPG.7b28b23537d4cd7fa1e0257984b6440a.JPG

Edit: I was taught that the PCD was between stud centres, ie, represented by the (diameter of) the dotted circle above, although its the same result as the above method.

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Be careful about the offset, they aren't all 35mm. on new or recent cars, so far as I am aware. I believe that is correct for the Mazda SDVs, but for the Ford based cars I think it is more likely to be 23mm. offset. But for some of the earlier cars (maybe Sierra SDVs?) it was I think about 35mm.. For early (ie narrows) I have no idea!

Really, you need to measure, or borrow a wheel to check if thinking of changing to a different width, or different offset.

It also occurs to me to point out that a lot of alloy wheels have the offset cast or stamped into the back of the wheel, so if you plan to replace a wheel with the same rim width and you are happy with the existing offset, then just look at the back of the wheels, and see if any of them have the offset marked on them.

Usually if you want to change the diameter of the wheel, but not the rim width, then you will need the same offset, whereas if you are going to wider rims you will normally need less offset.

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Stephen has hit the nail on the head here.

The reason wheel size, in particular offset seem so confusing when you go back across multiple posts, is that Westfield has used multiple sizes over the years. Offset in particular has changed a lot. Unfortunately it is not possible to say fro a certain specific date or chassis number, the offset for a 13" x &" wheel became x or y. As a result the ONLY safe approach is to measure the current wheels and work from them. Duplicating the offset if its just a change in style and the fit is OK, or tweaking the offset if necessary.

One final thing, bear in mind that just because a wheel may have a certain offset marked on it, doesn't mean it is 100% definitely that offset! A number of different manufacturers have been know to re-machine the offsets on stock wheels to match orders...

So, like everything kit car related, always measure to be safe, don't just assume.

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Thank you very much guys, really interesting read and very useful!

I am just after a change in style, the current set up is perfect really, I may just paint the current wheels to prevent any issues, not sure. My preference is the team dynamics black multi spokes, but that will be an increase in size then and I worry based on the above I may screw up the overall drive. Difficult one. But thanks again!

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