Hey all,
I apologize if this has been asked here before. I did a bit of searching and didn't find any recent information that was super relevant.
Anyways, I was looking at picking up some of those new Advanti Racing Storm wheels. I was thinking either 15x7 or 15x8 size. It seems like the best overall size for daily driving/weekend track days.
My car is exactly that (its a 99 NB Miata BTW), although every day it is become more track car and less daily friendly (which I am perfectly fine with :P) My question is: Whats the deal with offset? Seems factory offset is around 40mm positive. So going lower should push the wheel further out, thus making overall track wider, right? And wider is usually better??
Or does the offset play a role in lowering the car? Should I only look to change offset once I've lowered the car, because this plays some sort of factor in helping the suspension geometry once I've lowered it? Thanks in advance!
You don't have to worry about offset when changing ride height (fitment issues aside), offset has to do with steering geometry (and a little bit with suspension geometry). There are two basic approaches you can take:
- Do serious steering geometry research
- Stay as close to stock as possible
The most notable effect to worry about is the change in scrub radius. More scrub radius (which you'll get with more negative offset/less backspace) gives more steering feel, but also heavier steering and more torque steer if the car has driven front wheels.
The suspension geometry effects of offset are pretty minor unless you're making massive changes - it will change your effective spring rate and track width slightly, but that's about it.
Correct, lower offset will push the wheels out farther. Going out too far can result in fender clearance issues and could cause pre-mature wheel bearing wear if you go really low offsets. Use an on-line wheel offset calculator to see how the wider wheels with different offsets will "stick out" compared to the stock wheels.
Yeah, I noticed the Spec Miata guys run much less offset. Around 25-30mm positive I think. So you think they do that to give better steering feedback? I dont mind heavier steering, and obviously torque steer isnt a factor here.
Also offset is particular to wheel width, I dont know what width nb wheels are but I'm sure they are smaller than 7 or 8in wide.. et0 is dead center and any + or - is that many mm away from centerline. Ie et0 8in wide is 4in backspacing but same et0 on 7 is 3.5in
If it were mine id run the 15x7 et35, they will fill the wheel well much better than stock. Looked them up they are 10lbs! Heck yes go for em, dunno if you have seen the goodwin racing site but they listing for those wheels show them on a nb and they look great
Yeah Chiodos haha, my friend bought a similar set and they not only look great, but were incredibly light. And true, I think stock width is 6 inches. So you're right, even with the same offset, a wider wheel would already put the outer edge further out.
Desmond wrote:
Yeah, I noticed the Spec Miata guys run much less offset. Around 25-30mm positive I think. So you think they do that to give better steering feedback? I dont mind heavier steering, and obviously torque steer isnt a factor here.
Likely just to increase track width as much as possible, which can help with handling and aerodynamics.
yep, the people probably run lower offset because they have wider wheels or tires than stock and otherwise the inner tire would rub on one component or another. I'd recommend staying as close to stock offset as possible, but the 'penalty' for moving out a little bit to fit more tire is generally not as great as the benefit of the extra tire. If you are moving out just to move out (i.e. adding a spacer to wheels and tires that already work), then I think that probably has very little if any performance gain.
Finally, wider track might be better in some cases, but it can be a hindrance in autoX (every inch wider your car is means that much more distance covered and tighter turning angles for a given slalom).
What 10 lb. ET35s are you talking about?
These are the wheels I'm thinking of:
http://www.good-win-racing.com/Mazda-Performance-Part/61-1399.html
Lower offset will also effectively soften your suspension, BTW.
Miatas are quite happy running offsets in the +30 range without ill effects. I'd rather see a +36 on a 15x8, but the +25 wheels exist because it's a shortcut in the manufacturing process if there's also a +36 15x9 in the catalog.
Offset, wheel width and backspacing are all related. If you know two, you can calculate the third.
As for the initial question - the Advanti is a great wheel. Get the widest that will suit your tire. If you're going run a 205/50-15, get the 8". The offset will work and the tires will like the wide wheel
I like the look of those Storms (and they're light!).
The (non-Storm) wheels on my '00 are 15x7 et10, and they're at the edge of the fender. I think et25 on a 7 would be pretty ideal. 15x8 on an et25 would probably put it about where mine are now, clearance wise.
Since I never bothered to check the toe on the car when I picked it up (on awful coilovers), it ate through the inside edges of the tires down below the wear bars. Those tires were 195/45-15's and were a little too small for me, so I replaced with 195/50's and had gotten a lot of scrub.
Luckily, that Eastwood fender roller I bought last year was just the trick to pull the fenders out a little (though I get a scrape once in a blue moon - might do a little more).
So, along the same thing, my project is running 2.5 inch spacers to make the wheels fit. What effects does this have? Similar to wheel offset?
In reply to Dusterbd13:
Exact same effect as changing the offset/backspace 2.5 inches.
Kenny_McCormic wrote:
In reply to Dusterbd13:
Exact same effect as changing the offset/backspace 2.5 inches.
Well, maybe. It depends on what the stock wheels were. A high offset wheel and a big spacer is effectively the same thing as a low offset wheel and no spacer.
Alright guys I'm really torn between these two:
http://www.good-win-racing.com/Mazda-Performance-Part/61-1399.html
or
http://www.good-win-racing.com/Mazda-Performance-Part/61-1386.html
The first link is 15x7 with +35 offset. The second is a 15x8 with +25 offset.
I have no problem rolling the fenders if needed. Both wheels will fit a 205/50 tires, which is what I will probably put on them. My biggest concern is with offset. I do plan to eventually stiffen the car a bit (stiffer spring rate) and lower it, and I hear that this can usually play a role when deciding offset.
So would the 35 offset be good now, but not so good later once I lower the car? Or conversely, would the 25 offset make the car feel sloppy now, but work really well when I go stiffer and lower later? It seems that people tend to go with the 6UL 15x8 wheels from 949 racing over these ones simply because they are offered in a +35 offset. Help me out!
Which one should I go with and why? I dont want to fudge the scrub radius or geometry or anything! I just discovered that the wheels the PO had on weigh like 20 pounds each! Need to get some new wheels ordered soon 
Tough question...the +35s will be better for both steering geometry and fitment. On the other hand, the 15x8s will make slightly better use of 205 wide tires and will allow you to move up to 225 wide tires later if you want.
I think a 15x8 +35 wheel would be ideal. Too bad those Jongbloed Racing Aero 500s that Flyin' Miata used to have are sold out.
Check these out:
http://www.good-win-racing.com/Mazda-Performance-Part/61-1368.html
Edit: And these:
http://949racing.com/15x8-6UL.aspx
We have hundreds of 6ULs in stock. If you want a 15x8, it's the best choice for your car.
I decided to go with the 15x7 +35 offset. I really like the look of the storms. To bad the 8 inch one only comes in 25 offset. The 6ULs seem like great wheels but I don't much dig the look. I would have preferred an 8 inch wide wheel but that's OK, I plan to run 195 width tires on these guys. Thanks for the help!
I run the Storm on my track car, good wheel in a 15x7 or 15x9.
