6ULs

[theancientone]

Hi......did a search and found some mentions of 6ULs. Is anyone running 9 inch 6ULs on an Exocet? Thanks.

[greg]

Search posts by thejeffman.

[theancientone]

I'm painfully slow, but I can't find a member with the name 'thejeffman' and so can't find any posts.

[JIDiesel]

Here is his facebook page. www.facebook.com/NMHFR?fref=ts

"tehjeffman" member name.

[boileralum]

The short answer is that you need much lower offset wheels on the Exocet than a miata, so to run the 6ULs, you would need to run some big spacers. There is a google doc that Warren made , I think I saw it linked in the thread on GRM. I have it bookmarked on my home computer, but don't have it here at work.

[theancientone]

Please forgive my ignorance....why, in principle, does the Exocet need a lower offset than the Miata/MX5.

[mawdo81]

Moves the back of the wheel away from the frame and wheel arch mounts. Something the miata avoids through the chassis itself.

Sent from my GT-I8190N using proboards

[theancientone]

Thanks. So spacers are needed for clearance purposes rather than to optimise suspension geometry?
Does this mean that the (reputedly excellent) suspension geometry of the Miata/MX5 is compromised by the spacers, and does it suggest (improbable as it might be to achieve) that an alternative way of supporting the wings/fenders would negate the need for spacers?

[tacan]

The spacers are for clearance. We are stuck running a 0 offset 15x8 or effectively a -12 15x9 to clear the frame in back, OR spacers in the 36mm range. I have not seen anyone post numbers/pictures/specs showing what you can get away with as far as minimum clearance, i.e. a 205 on a 15x8 +36 needs 'X' spacer to clear, a 225 on a 15x9 needs 'Y'. Granted, this isn't easy as every component involved is going to affect clearance, every tire is going to be different and what works on the street might not on the track. I was a little ticked that the clearance issue wasn't addressed in the U.S. redesign, and my nice ARP studs might have to come out for some giant blocks of aluminum. We are stuck with imperfect scrub radius, which might not make that much difference for most users(I personally liked the feeling better with the 'wrong' offset wheels, 11-16mm less than optimal). Getting into the serious wheel sizes (15x9) I bet it will matter, as the (possibly) 48mm wheel spacer you'd need for a 15x9 is getting really big. I really want to know just how little spacer I can get away with for 15x9 225's at the 36mm 6UL offset. The reality is, a bolt on spacer is the better way to do it from a mass, rotating mass and wheel strength perspective. For now, I'm running 15x8 0's with 205s.

[theancientone]

Is this thinking correct?
To get the necessary clearance the standard mk1 Miata/MX5 7J et45 wheel reportedly needs 30mm spacers.
So for the same clearance a 7J et36 wheel would need 30-(45-36) = 21mm spacers.
And for the same clearance a 9J et36 wheel would need 21+25 = 46mm spacers.

[BTD]

^ Math looks right to me. To get the same clearance:

15x7 = ~+15 offset
15x8 = ~+0 offset
15x9 = ~-15 offset

So on and so forth.

[miket]

Aug 13, 2015 3:35:48 GMT theancientone said:

Is this thinking correct?
To get the necessary clearance the standard mk1 Miata/MX5 7J et45 wheel reportedly needs 30mm spacers.
So for the same clearance a 7J et36 wheel would need 30-(45-36) = 21mm spacers.
And for the same clearance a 9J et36 wheel would need 21+25 = 46mm spacers.

Just in case size matters - the UK Exo Build Guide says 32mm spacers rather than 30mm...

"The wing stays are designed to use 195/45-16 wheels/tyres either with a 32mm spacer for 45 ET
 wheels or no spacer if you buy 15ET wheels".

Better safe then rubbing eh!

[theancientone]

Thanks. So that's how 'tacan' gets to 48mm spacers for 9" et36 wheels.

[theancientone]

Sorry to go on about this but Miket's quote from the Build Guide raises the query of whether it's the design of the wing/fender stays which determines the need for and size of spacers..... or the proximity of the bodywork/chassis.
I ask this because I keep coming back to the fact that we sometimes run 9" 6ULs on our Mk2.5 MX5 without spacers, without modifications to the bodywork, and without any rubbing.
And to my inexpert eye there doesn't look to be anything on the Exocet which is nearer to the wheels than on the MX5.
I guess the way to find out is to trial fit the 6ULs on the Exocet.

[mawdo81]

Look through the build diaries, there are some US auto-crossers who ran their cars pre body work (inc guards/fenders) that had issues with tires rubbing the chassis.