Help me understand bolt patterns and offsets
 

I have a stock 03 Roadster. After doing a search, I believe the bolt pattern of my current 5 spoke 17"s are 5x100.

I am looking to upgrade to 18s. I saw a set on ebay that had an offset of 35mm and a bolt pattern of 5x112.

Will these fit... or do they need modification?

TIA.


Also... what stock tires should I get with 18s so I keep my speedo as accurate as possible.

the offset works but the bolt pattern s/b 100mm

No they won't fit.
 

Have a look in the classifieds for some Sportec 18's that are 5x100 (shameless plug).

Hmmmm... then why....
 

do i see so many people on this site with RS4 replicas or OEM replicas. What offset and bolt patterns do those run at?

I am looking for the RS4 "look".

The guy below has some details...
 

<ul><li><a href="https://forums.audiworld.com/tt/msgs/1235759.phtml">https://forums.audiworld.com/tt/msgs/1235759.phtml</a</li></ul>

bolt pattern is the number and spacing between the lug bolts...
 

All TTs are 5x100, the only way you can run a different bolt pattern is to use an adapter and those are fairly large and will affect your offset. Check out the <a href="http://www.tirerack.com/a.jsp?a=AR4&url=%2Fwheels%2Ftech%2Fboltpatt.jsp">T irerack</a> for more info.

Offset is the distance between the wheel mounting surface and the centerline of the rim. So if the mounting surface was at the centerline that would be 0 offset. The stock 17" wheels have a 32mm offset so a 35mm offset for up to an 8.5" wheel is usually ok. Less offset will push the wheel out towards the fender, that's why lots of folks use spacers to give a more aggressive look.

<a href="http://www.discounttire.com/dtc/brochure/info/helpDeskWheelOffsets.jsp">Discount tire</a> and the <a href="http://www.tirerack.com/a.jsp?a=AR4&url=%2Fwheels%2Ftech%2Foffset.jsp">Tir erack</a>. Both have diagrams that will help.

On an 18" wheel 225/40/18 would be the cloest match to the stock 17s (225/45/17) but 235/40/18 would also work.
Use this <a href="http://www.miata.net/garage/tirecalc.html">calculator</a> to help you visualize the different possibilities and it will also show the speedometer error.

I believe some of the RS4 reps come dual-drilled....
 

for both 5x100 and 5x112. If so, they'd work. 225-40-18 is your closest size to the 225-45-17 the car came with if you had 17s
Fig