Max spacer limit without longer studs
 

Would it be ok to use a 5 or 10mm spacer with original studs and lug nuts? What is the safe limit? I may need 15mm spacers for rear wheels but not sure if that's ok on original studs....

5mm is the safest max you should go on oem studs

^agree

5mm is the max I'd feel comfortable going.

For the 15mm in the rear, if your wheels have the recesses on the back pad, you can get the spacers with offset studs. You bolt the spacer to the hub with low profile lugs, then bolt the wheel to the 'new' studs that are on the spacer.

I thought 3mm is the max... when I ordered 5mm spacers for my vw, HR send me extended studs as well.

It's different from car to car. I have done road course, drag and autox on the 5mm spacers. Just for the love of god make sure you are using the right lug nuts. :-)

Agreed^

https://www.youtube.com/watch?v=jv4m41viy4I

^wrong lug nuts!

I've read mixed reviews about spacers that come with studs. For 10-15mm, I'm thinking of getting ARP longer studs and a regular spacer.

The general rule of thumb I've heard is that if you can thread the lug nuts at least 8 rotations onto the stud, then you are fine. If you cannot, then your spacer is probably too large for the studs you have.

You can do 5mm, but you are just getting the lug nut to a point where it can secure the wheel. I use a 5mm spacer on the rear for the street, but not for road course events. Anything more and you won't have enough threads to secure the wheel well enough to be safe.

i just purchased 3.5 inch studs , from a company called black works racing , i found ARP was a bit over priced and these studs were made of the same material 8740 chrome moly and the tensile strength of 190,000 psi .

including shipping these were half the price of ARP studs , the only extra hassle of longer wheels studs is replacing the rear bearing but i felt i might as well , car is 20 years old and im running a much wider wheel then before so why not start everything off new ,plus i feel that long studs with a spacer are a bit more safe than spacers that come with studs bolted on to them

Nope..don't get your Buddy to put your wheels on.
(yuk,yuk..did I ferget sumethin???..)

5mm spacers will reduce the number of turns on the lug nuts to 3-4 in my experience.

I've used Gorilla tuner lug nuts that extend a bit in to the hole in the wheel, giving me about 6 turns on the lugs with a 5mm spacer. SCCA requires 5.

10mm on stock lugs - won't work.

Since then I've replaced the stock studs with Moroso 46245 Studs