Front track measurement?

A

anviltester

Well-known member
How does one measure the front track? is it outside of the wheel to the inside of the other side wheel? Or is it outside of tire to inside of tire? if its the tire what about the diff width tires, radial or bias, sit closer or further out. Also the FP spec line for a miata is 60.4" but C.4. says 103% - stock plus 2.5" so is that 60.4 the 103% or is 62.9" the 103%? Just trying to do some setup for new fender molds and need to get this right but its a little confusing for a first timer.
 
Page 185 of the Feb 2016 GCR

4. MEASURING TRACK
Track is the distance between the centerlines of the wheels as raced, without driver, measured at a horizontal plane through the wheel hub
centerline. Alternatively, it may be measured from the inside of one wheel at the hub centerline height to the outside of the other wheel, then
conversely from the outside of the first wheel at hub centerline to the inside of the second wheel. The 2 dimensions obtained are to be added
together and divided by 2 to obtain the average. Measurements are to be taken at both front and rear of the wheels and averaged to compensate
for toe-in/out. Under certain circumstances it may be preferable to measure from the outside of one wheel to the outside of another and
from this dimension deduct the thickness of one wheel. This should be repeated 180° opposite to the first measurement and the two dimensions
averaged.
 
The number on the spec line is the actual maximum track.

They got that number by looking at factory documentation, then doing the 103% plus 2.5" thing.
 
The VW spec line uses the stock width. VW rear= 57.2 x103, +2.5 or the actual limit is 61.41., My front I figure to be max of 63.16. I hope I have it right..

I dont see any of the Prod cars listed with a max track, just the factory track specs.

The speced method or measurement is extremely difficult to actually execute,measured at the hub centerline. Much easier to measure at the ground and subtract the camber value.
It is quite conceivable to be measured at the hubs and be 1-2 in over at the ground. @ 3 degrees camber .
 
99 miata, EP factory track spec:
Front: 1410mm/55.5in
Rear: 1428mm/56.2in

Source:
https://books.google.com/books?id=8eNAb48HomAC&pg=SA1-PA9&lpg=SA1-PA9&dq=miata+track+specification+1410mm&source=bl&ots=Gvldefq2nC&sig=3NI8bqEyX0aBg1ndYdAXVAZtGQY&hl=en&sa=X&ved=0ahUKEwiwzOaIhvrKAhXKuoMKHXcCCpwQ6AEINDAE#v=onepage&q=miata%20track%20specification%201410mm&f=false

99 miata, GCR spec line:
1483/1509
(59.9/60.9)

I found the specs to be incorrect and sent a letter to the CRB - they since corrected the spec line to be the number listed above.

As you can see, the stock track spec is clearly not on the spec line.

I'm not sure what to tell you - you didn't say which car you were talking about, list a reference for stock track spec, or the GCR spec line and track spec.
 
My example is page 698 , early VW. Track listed is 58.9 and 57.2 . Factory listed track width.
The GCR should use the factory specs , not the max specs. Where clearly the rule states that the track may be 103 plus 2.5 of the listed spec.

I think that you are right the listed Miata specs are clearly near the max allowed . So are the current Miatas @ the listed spec or the listed plus 4 spec?
 
Mike, the track specs seem to be pretty jacked up.

The GCR lists the miata track spec, AFTER the math is done to the factory spec.

If you're saying the VW has the stock spec listed - I don't know what's going on.

I do know - they just added the "M-Technic" BMW 2.5L to E prod- That car has a similar (but not exact) track spec to the other 2.5L BMWs...

..however, the track spec for the M-Technic is completely wrong - they took the 2.5L max track, and then double-added the 103% to that - it's completely wrong and not even close. It's (near) stock, time 103% plus 2.5" - and then ANOTHER 103% plus 2.5"!

Who knows?
 
Looking closer, the numbers listed dont match any of the specs- either the OE VW or the max allowed. Many of the cars listed have the same issues.
I have spent lots of time/money getting to the max allowed track based on the old wording. The Aug GCR wording is " Track specifications will be set at 103% of the car’s stock track
plus 2.5 inches".
The older wording was the track may be 103plus 2.5 added the the listed spec. I will go back and find the older book.
Edit; looks like the same wording . Just read the rule wrong..
@ this point I have new custom control arms, axles, and wheels. As do others.
The OE spec That I have shows; 55.3 and 54.0, computes to 59.45 and 58.12.
Listed now is 58.9 and 57.2
I will check for better OE specs.
 
Mike - they did actually correct the GCR for me.

If you find official factory documentation, for all the listed years on the track line - send it in. They'll correct it.

It should read the computed track spec, not the factory spec - or else the beloved Miata specs are way off, After I contacted the CRB and they made a correction.

Good luck.
 
On line, I see the front & rear as delivered track as 54.72/53.54.

Seems this is where there is a difference.

I believe in the 60's is too wide. The body width max was only 64.8". It's easy to see the tires are well within the body profile so the listed track appears correct.

Did you ever post pictures of your front spoiler as suggested by Sam Moore?
 
Ill gather the track data and put in the letter . 1/2 in difference.
As far as the air dam, I put in at least 2 letters to clean up the wording and both were tossed. I will flare theshitout of the fenders and stop the air dam at the corner/junction of fender and dam . Done with it.
I just cut the nose off today as a result of gross incompetence of Miata driver @ Sebring sun. All new- much cleaner/smoother and nicer .
MM

Jim's numbers are correct for the 13x5.5 wheel cars . The later cars had 14x6 and thus the 1/2 in wider. None of the 1.7 or smaller engined cars had 14s tho

88 Rocco A1, OE track= front 55.3, for max of 59.45/ GCR value 58.9
Rear 54.0 , for max of 58.12,/ GCR value 57.2


88 Golf A2, OE track front 55.6 , max of 59.77,/ GCR value 60.5
raer 55.4 max of 59.56/ GCR value 60.2

If you have different values please post source. TIA,MM
 
Mike, here are a bunch of factory brochures that show track information. http://a2resource.com/brochures/brochures.html
 
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