topley

Hi guys,
Been finding it difficult to find good info on 3 piece wheels. Basically I want to put 10" 18's with 275 tires all around on my 85.5 race car that just got a turbo motor and trans. Same size/offset front and rear so I can rotate wheels/tires. I have 1" wider fiberglass front fenders and I believe the 10" rears fit fine on the back. I've seen posts saying that late offset cars can fit a 7.5" inner barrel front and rear so I was thinking 6" inner barrels with 4" outer barrels. But what the hell do I know...

So, do 3 piece wheel centers have any kind of "offset" built into them? Do I need to worry about how much clearance the spokes or mesh give from the contact face? (I ask as I have Xshops billet hubs for 330mm discs and adapters for M030 calipers)
How "standard" is the setup for 3 piece wheels manufacturer to manufacturer?

Thanks all!
Jay

Paulyy

Have fun with this.

www.willtheyfit.com

factory 86 wheels
F - 16x7 et 23.3 (205 55 r16)
R - 16x8 et 23.3 (225 50 r16)

On the rear you can have around 20mm more "poke" to the guards.

So you can have 18x10 et28 with 275 35 r18 tyres.

topley

Great website! That's funny, I've never heard "poke" before as a description. I like it. That certainly helps me visualize...

Now to find out how offset is measured with wheel centers. With wheel halves it seems like the unit of measure is 1/2" so for instance I can change offset by 12.7mm by changing from 6" and 4" barrels to 6.5" and 3.5".

Paulyy

It's a 'stance' term for when the wheel is poking out the guard. It's just want the website uses to make it less confusing.

Anyway the offset is measured from the centre of the barrel. so you have a 18x 10" wheel with a et 0 means you have the mounting face of the wheel (the face that sits on the hub) is in the middle of the wheel.
If you have a 18x10 et25 means the mounting face is forward from the centre of the wheel 25mm
likewise if you have an 18x10 et-30 means the mounting face is 30mm away (more dish) from the centre but in the opposite direction.

The dish will change if your centre section of the wheel is concave.

topley

Yeah, so that's more my question... I have a basic understanding of how to fit regular wheels... but race wheels with barrel halves I only hear people talking about what the inner and outer barrel widths are (or more specifically barrel halves for sale), not how the relate to the wheel centers or offset. It's this mix and match that I am trying to educate myself about.

Here's 3 for sale ads that still don't help me figure out offset

https://rennlist.com/forums/porsche-...ashers-fs.html

https://rennlist.com/forums/for-sale...-for-sale.html

https://rennlist.com/forums/racing-a...fikse-bbs.html

guards951

It all depends on the face/backpad setup.
Good wheel companies offer different backpad(mounting surface/'disk') thicknesses to accommodate whatever brake setup you're needing to clear. So if you already have the faces, just lay them on a totally flat surface and measure how much the backpad is holding the edge of the face off of the surface (or vice versa, in rare instances), then you can figure that into your effective offset.

Faces are generally 1/2" thick. Some faces mount through the front of the outer barrel or back of the inner barrel, so it won't affect the overall width. The most common is generally a sandwich mounted face, which is just as it sounds, being sandwiched between the barrels, so it DOES affect the width.

If you have a 5" inner barrel, a face with a TOTALLY level backpad, and a 4.5" outer barrel (lip), then you'd have a 10" wheel with a +/-0 offset.
The necessary backpad thickness to clear your brakes depends entirely on the spoke design. Some spokes bulge out to accommodate larger brakes without needing a super thick/heavy backpad, while others are flat and require a much thicker backpad to get the spokes away from the caliper.

topley

So this basically confirms what little I've been able to find searching pics and used ads on the Internet. Seems like one needs to just jump in and commit to a style or manufacturer and figure out what fits and sell what doesn't... Wish I had a boxster or 911 where a million people before me have tried any combo.
New track... Anyone know a wheel shop that deals in used 3 piece race wheels (even better if they are on the west coast...)
Thanks!

Paulyy

http://www.ccwheel.com/

www.fikse.com

topley

And by the way, your car looks amazing with those wheels...

FrenchToast

Just so you know, many wheel manufacturers DO have available two (or more) different centers of a certain style to fine tune offsets.

I know Fikse, HRE, and surely others have used two or more different centers in the past.

I think the pairs usually differ in 0.5" - probably to enable half-inch backspace increments that would otherwise be one-inch increments by just switching barrels.

Or maybe the centers are .25" different offset and barrels are .5"? I don't remember.

Some single sets have different offset centers F/R, but you need to look very close. It is usually very subtle.

Someone like user and wheel expert Thatcher might be able to tell you some more.

topley

Sounds like what I was expecting... Thanks French Toast!