Wheels w/RWD Offset

Hammer · Postby **Hammer** » Tue May 16, 2006 7:42 pm

Does anyone know what wheels will suit the MX5 (4x100 P.C.D.) that has a RWD biased offset (apart from made-to-order Simmons)?

Unfortunately most cars with 4x100 PCDs are FWD. This makes most of the wheels to suit to have a positive bias offset. Which means the wheel/tyre moves inwards.

In my case I want to widen the track, and I want to do this without resorting to buying wider wheels.

Can anyone help?

I like the wheels below but unfortunately the 1st two don't come in silver only (or oven shadow chrome finish), and the latter has a severe positive offset (+40). I'm looking for alternatives.

adamjp · Postby **adamjp** » Tue May 16, 2006 8:07 pm

Hammer,

I think that you may be a little confused.

The MX5 came with a 40 to 45mm offset, depending on the wheel.

Most FWD cars have a lower offset, 32 to 38mm. This places the mating face of the wheel/hub closer to the centre of the wheel, pushing the outside of the wheel OUT towards the curb.

This is as good a primer as any http://www.tirerack.com/wheels/tech/techpage.jsp?techid=101

Put simply a 7 inch rim with a common FWD (say 32mm) offset will increase the track of a car by virtue of the additional 1/2 inch (12.7mm) in width on each side, plus an additional 13mm or so due to being hung out further on the hub. This should deliver a track increase of 50mm.

I don't know of any wheels made for 4x100 which have a negative offset. I think that the reason for this is that they are not likely to fit any car with that PCD.

kitkat · Postby **kitkat** » Tue May 16, 2006 11:08 pm

im guessing your looking for a 15 - 20mm offset.
i put the wheels off my 89\" BMW onto the mx5 for day and they stuck out heaps.
the rims were 15 x 7, with a 15mm offset.
Only 90' and earlier run that offset though.

EGG80X · Postby **EGG80X** » Tue May 16, 2006 11:40 pm

Hammer you got a NB right?

From what I read, NB can go up to +25 offset with 7\" wide rims.... best offset is +35

Me and Jolt run offset +25 on our NBs.....
Jolt has 16x7 volks
and I have 15x7 centra

and 205 wide tyres will cause rubbing on the guards

Plenty of Japanese and german rims have a wide range of offset to choice from... like you suggested Simmons do custom make offset and width on their rims

Garry · Postby **Garry** » Wed May 17, 2006 10:20 am

My new wheels are 1/2 wider and have a 38mm offset which is only 2 mm different to the Mazda originals and my alignment dude went off at me for getting the wrong offset. He was going off about scrub radiuses or something. Apparently the steering geometry is all wrong now and the car doesn't steer as sweet as it used to. I just think it's because my tyres are shagged.

Hammer · Postby **Hammer** » Wed May 17, 2006 11:36 am

adamjp wrote:Hammer,

I think that you may be a little confused.

No not confused, I just didn't articulate it well.

Thanks guys for all your tips regarding preferred offsets. This gives me a little more information than I had.

I didn't know what least amount of positive offset I can get before it started rubbing the guards. Now I know it will be about 30ish.

The wheels above where about +40 which as Adamjp said is around the same offset as my standard NB8B 16x6.5 wheels. Does this mean if I get a 17x7" wide rims, they will be 1/2 and inch wider on the outside?

I'm also considering getting wider rims for the rears (ie. 7" fronts & 7 1/2 rears - ala S2000 etc). Is that recommended?

Adam_NAclubman · Postby **Adam_NAclubman** » Wed May 17, 2006 3:52 pm

http://marksink.com/tire_wheel_offset/offset.html

Babalouie · Postby **Babalouie** » Wed May 17, 2006 4:39 pm

Garry wrote:My new wheels are 1/2 wider and have a 38mm offset which is only 2 mm different to the Mazda originals and my alignment dude went off at me for getting the wrong offset. He was going off about scrub radiuses or something. Apparently the steering geometry is all wrong now and the car doesn't steer as sweet as it used to. I just think it's because my tyres are shagged.

Scrub radius is basically the intersecting point between the point of the tyre tread and the natural axis around which the front wheel pivots as you turn the wheel. The MX5 is designed with a zero scrub radius, which basically means that as you turn the wheel, the tyre pivots at exactly the centrepoint of the tread. Of course as you drive, things like body roll, added negative camber for racing and sidewall squirm ruin this relationship a little anyway.

And obviously this relationship is also buggered up if you start fitting rims which stick out more, and in some cars it can lead to tramlining, poor directional stability, etc. More so on FWD cars.

But IMHO the MX5 isn't really one of those cars, I run +14 offset wheels and the only undue effect was that the (non powered) steering got a bit lighter and the turn in was a touch slower. But certainly changing the offset by a measly 2mm isn't going to make the world come to an end

Babalouie · Postby **Babalouie** » Thu May 18, 2006 5:42 am

Slugoid wrote:Would +45 rims fit a mx5 or a bit too far in?? This is for a 15X6 rim.

+45 is stock offset for an NA.

Garry · Postby **Garry** » Thu May 18, 2006 9:35 am

But certainly changing the offset by a measly 2mm isn't going to make the world come to an end

My thoughts exactly. Which is why I think my steering grief is caused by the shagged tyres. I'll find out on Saturday when I get a new set.

Moggy · Postby **Moggy** » Sat May 20, 2006 9:16 pm

I have been looking for a set of decent wheels for a 4x100 pcd with a decent offset for a while now. I can't find any (helpful I know). I have even considered going to the trouble and expense of changing the stud pattern to 5x114.3. I don't know if I will do this yet.

These wheels are at the top of my list - light, simple and effective:

You can get these (17\") with a 33 offset in 4x100 but with a 5x114.3 pcd you can choose from a 22 or 12 (!) offset.

The effect of a decent offset can be seen here:

And here:

jolt · Postby **jolt** » Sat May 20, 2006 11:08 pm

Moggy ... just be very careful when looking for 4x100 versions of wheels you have only seen photo's of in 5x114.3. I was hoping for a lot more dish on my 16x7 +25 Volk CE28's because of the photo's I had seen on various other RWD cars, but they all had 5x114.3 stud patterns (Skylines, Silvia's, RX7's, RX8's, 350Z's) and they were able to fit 19x9.5 +12 wheels under their guards. Something like this is what I was hoping for ...

But this is what I got, the spokes are still pretty much flush with the rim just like a +40 offset ...

I'm still pretty happy with them, because they're so light and strong and I love the colour and style.

Unfortunately, to get the extra offset on 4x100 wheels, manufacturers will usually just add more \"meat\" (metal) to the inside of the hub to push the wheel out further, rather than located the face of the wheel further inside the rim. Does that make sense?

That's why EGG80X's wheels look so great, because they're a rare set they do the latter ...

Rod

Moggy · Postby **Moggy** » Sun May 21, 2006 12:32 am

Jolt, your wheels still look pretty good, but I am aware of what you mean about the 4x100 wheels. If you look at this piccie off the rays website it shows the different disk types:

And if you look at this link it shows you which disk (or face as it is referred to here) goes with which wheel.

http://www.rayswheels.co.jp/cgi-bin/cgi ... Name=T57RC

As you can see the flattest disk goes with the 4x100. Are there any 4x100's with a curved disk?

EGG80X · Postby **EGG80X** » Sun May 21, 2006 12:08 pm

how about the volk's te37 cup?

GOT DISH?

this is 15x7 offset+25

Babalouie · Postby **Babalouie** » Sun May 21, 2006 1:11 pm

EGG80X wrote:how about the volk's te37 cup?

GOT DISH?

Yup

The Te37 Cup is a bit deceptive....there's a massive lip to the rim but the spokes actually dome out a lot, so IMHO it ruins the effect to some degree....