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Correct Wheel Offset?

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#1
juliancates

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My new-to-me SM is a 1991, and I'd like to pick up a couple sets of wheels. I see SM-specific wheels in both 25mm and 30mm offsets. Which is the "correct" offset to use for my model year?

Appreciate the help, thanks in advance!
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#2
Bruce Wilson

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You want the 25mm offset because that is max. You can buy wheels with other offsets and add spacers as long as they don't exceed 13mm, so not more than 38mm wheel (subtract spacer width).

-bw

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#3
juliancates

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You want the 25mm offset because that is max. You can buy wheels with other offsets and add spacers as long as they don't exceed 13mm, so not more than 38mm wheel (subtract spacer width).

-bw


Thanks a ton for the information, Bruce. 25mm it is, then.
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#4
William Bonsell

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Julian....
You might find more of selection and better pricing running 30mm offset. Tirerack sells a great SM wheel...30 offset...for about $90 each. I have several sets, but did add extended wheel studs along with spacers this year to maximize track. In the overall big picture, it probably makes very little difference. But, then again, Bruce is THE spec miata guru up here in the Northwest...as well as 2010 SM Oregon region champion.
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#5
Bruce Wilson

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Yeah, but I'm still an old Kosei throwback guy. I run 38mm offset with the max spacer. I like to choose my wheels based on price, looks, and they match what I already have.

-bw

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#6
juliancates

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I'm looking at the D-Force wheels. I ran the 17x9.5 versions on my BMW and was very happy with them. Looks like they're $109 just about everywhere. To be honest, I can buy a set of wheels AND tires for what I used to pay just for a set of tires on the old racecar, so I'm pretty stoked!

When I bought the car, it came with two sets of Koseis. Just checked, and at least the set I have in the basement is 38mm offset, but I don't recall seeing any spacers. Looks like maybe the PO was giving up some track width. Good to know!
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#7
juliancates

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Julian....
You might find more of selection and better pricing running 30mm offset. Tirerack sells a great SM wheel...30 offset...for about $90 each. I have several sets, but did add extended wheel studs along with spacers this year to maximize track. In the overall big picture, it probably makes very little difference. But, then again, Bruce is THE spec miata guru up here in the Northwest...as well as 2010 SM Oregon region champion.



I took a look, and I do like the looks of these. I assume you are talking about the TR Motorsport C1M ? I thought it was interesting that the light grey version was 13.0 lbs, while the silver was 13.2 and the black wheel was 13.6. I should at least give these some thought, although I do like the idea of maximizing track width with the 25mm wheels and not having to worry with spacers.
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#8
philstireservice

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I took a look, and I do like the looks of these. I assume you are talking about the TR Motorsport C1M ? I thought it was interesting that the light grey version was 13.0 lbs, while the silver was 13.2 and the black wheel was 13.6. I should at least give these some thought, although I do like the idea of maximizing track width with the 25mm wheels and not having to worry with spacers.



Go with the D-Force. It's low pressure cast. The TR Motorsport wheel is only gravity cast...not even OE standard.

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#9
JayF

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Julian, also FYI Tirerack makes a version of that wheel for e30 BMW in et25. The hub size is off by 3MM but some guys do go that route. Also Tirerack is bringing back the Kosei K1 15x7 et25 also in e30 fitment and they will be available 4/1.
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#10
juliancates

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Laughing at myself for bumping my own thread from several years ago. I've since sold my SM and have been racing SE30 for the past few years.  I did, however, just pick up another SM, so the question is again fresh in my mind.

 

Here's the thing this time.  I have a ton of E30 wheels/tires. I believe that they are all ET25, and all of them are Team Dynamics.  I know the E30 center bores are slightly larger.  If I'm understanding what I'm reading correctly in other threads, I should be able to use them on the SM and not have to use centering rings. In other words, the lugs should center the wheel on their own.  Just to be sure, I want to ask this explicitly:

Is it cool to use ET25 E30 wheels on a Miata?

Do I need to use centering rings?

 

Cheers!

 

Julian


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#11
basscat

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I have run that setup (ET25 E30 wheels on a Miata) with no issues.


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#12
Ron Alan

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Hub-centric is nice but I don't think necessary. 


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#13
juliancates

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Thanks guys!  This is awesome, as it will make it all the easier to switch between cars. Wasn't looking forward to having to duplicate a bunch of wheels/tires. (At least for NASA...)


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#14
Qyxz

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What do you guys think of our soft suspension and how it pairs with the 25mm vs 30mm? 


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#15
Ron Alan

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I think it is the least of your worries when it comes to turning fast laps!


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#16
Caveman-kwebb99

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Laughing at myself for bumping my own thread from several years ago. I've since sold my SM and have been racing SE30 for the past few years. I did, however, just pick up another SM, so the question is again fresh in my mind.

Here's the thing this time. I have a ton of E30 wheels/tires. I believe that they are all ET25, and all of them are Team Dynamics. I know the E30 center bores are slightly larger. If I'm understanding what I'm reading correctly in other threads, I should be able to use them on the SM and not have to use centering rings. In other words, the lugs should center the wheel on their own. Just to be sure, I want to ask this explicitly:

Is it cool to use ET25 E30 wheels on a Miata?
Do I need to use centering rings?

Cheers!

Julian


Yes the lugs will center the wheels without problem.

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