I've tracked with 15/20 spacers and no issue. These are lug replacement all around.

FYI, Porsche lists 5mm spacers as an option on their cars. Just sayin'

Well, first of I'm in no way saying they won't sit firm or that they will be loose in any way, mine are in there firm as hell. It's just if you switch out studs often enough, you will start to shave the holes the studs are in and that can lose some of the firmness. Nothing to worry about of course, but I just mentioned it as related to track use.

ive been using spacers for over a decade. never encountered an issue. ive tried both types, the ones with new studs and once with built-in studs. i currently only use the ones with built-in studs (Eibach, Kics are my favorites, and even tried the garbage looking Ichiba's. they look like crap but work just fine).

most people have problems with over torquing or using the wrong type of spacer. like using spacers without hubcentring rings on hubcentric wheels and such.

I'm really wanting a set of spacers (15mmF / 20mmR) but I have heard that users with the built in stud versions have had some shaking issues at hwy speeds. So is the extra work involved with replacing the studs worth it? Are the built in stud versions hub centric ?

If you want 15mm for the front you have to swap out your studs.

Yup, like Azn says you must swap out the studs for the fronts on the 370z. You could use either for the rear, but why have to worry about tightening 2 sets of lugs per wheel (with the bolt on type)? Might as well do it properly and use the ones with replacement lugs.

Thank's for the info.. I am more towards replacing the stud.. Just for peace of mind..

theres some that have stud and hub centric built in... like this one.

http://www.more-japan.com/files/d_5815.jpg
FIC 20mm Wheel Spacer for 5/114.3 Bolt Pattern - More Japan :: Since 2003

I too have the 15/20 set up and have tracked my Z twice last summer with no problems.

I track with 15s in the rear now and used to use 25s in the rear with no problems. On the street, I run 15/15. I choose to use spacers so I can use the same wheels front and back for track use and rotate my tires.

The only issue I have had is a balance problem with ichiba spacers, because their hubcentric ring isn't deep enough to fit into my Nismo rims, so it doesn't center them. Switched to H&R and have no problems at all.

I hope that's not the issue I could have. I just ordered some Ichiba spacer (10mm). But I don't have the Nismo rims (see my sig). They are the extended studs models. I wouldn'y use the bolt on ones anyways. But was told they wouldn't work with my wheels anyways. I had these same spacers on my 350 with Rays wheels and they were fine. Guess I'm paranoid.

the ichibas are also fine with my 350z Rays wheels that I use for the track, and apparently, most people with the factory wheels have no problem either. they just don't work well with the Nismo Stune wheels.

I have stune wheels with 20/25 spacer. Steering wheel shakes after 65r 70mph.
Been trying to fix the problem.. and now it all make sense now. Thank you!
Thank you!
Did you go with the H&R DRM ,or DRS??

Check this thread for empirical feedback ........

IMPORTANT ADVICE: Don't run spacers! - Brakes & Suspension - Zclub - Australia's Largest Nissan 370Z and Nissan 350Z Forum

Note: there is nothing wrong with a space that is hub-centric and which requires longer studs - ARP do a 75mm long stud which is perfect.

My issue is with "spacers" that are fixed to the hub with the original studs, and the wheel is fixed to the spacer with a second set of studs .... it was this typre of spacer that is the subject of the link.

I have used up to 25mm spacers for my track wheels as I could not get a forged wheel with the right offset. These spacers are hub centric to the hub and centric to the wheel centre bore hole, all fixed to the hub with 75mm ARP studs.

The wheel nuts are thrown away after every 20 changes and the stud threads inspected before each track meet. I;ve lost a wheel "at speed" in my race car and it gains youur attention in the ost immdeiate manner possible.

THey are H&R, don't remember the model designation, but the hubcentric ones that use longer studs, not the bolt on kind. I mistyped though, I only use the 15s in the rear now. before I used 15/25. the 25 were the bolt on kind.