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What is the correct way to measure the front and rear track ?


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#1 Marshall

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Posted 26 June 2011 - 04:18 PM

I measured the front and rear track on my hatch today. Doing it by my self...I believe i got it fairly accurate but I'm not 100% happy with the accuracy.

Front
1422 1st measure
1412 2nd measure

Averaging them out... 1417mm

as for the rear it's a 9" that came out of a LX Torana.

Rear = 1380mm 1st measure, this is to the out side to out side of the drum.


Do these measurements seam correct ??


Now if they are correct, Working out my rim sizes, I need some help.

Some information to help work it out.
  • 1976 LX Hatchback
  • Track = Rear 1380mm, Front 1417mm
  • Im going with HQ stud pattern,
  • 330mm hoppers stoppers on the front.
  • I want/ would like, 235/55/R17 front and 255/55/R17 on the rear.
  • Guards will be cut, and Wilsons flaires fitted.
  • I would like to fill the guards as much as possable.

Now what widths, offset, back spaci should i go with ??


.

#2 LS1 Hatch

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Posted 26 June 2011 - 04:41 PM

I run 18" on mine, but width-wise they are 8" up front and 10" out back, and they fit quite well with decent room all around them. If I were you, I would go ahead and get all the flares fitted up and then measure your actual car for what backspacing works best instead of trying to compare it to other cars. (nothing wrong with that to start with, but when you have altered stuff, going with the actual measurements for your car will help you get the best fit.)

On mine, I measured the back spacing for each wheel before building them, then went ahead and built them to center the wheels as much as possible...helps give the max clearance as well. (Which I have heaps of) I could go larger on tires too, but got a deal off my mate with the tire shop on these, so will run them for now at least. (just 225/35 up front and 265/35 out back)
I run a 9" as well, and a custom brake setup on the front...but the back spacing that suits mine nicely might be a 1/2" (or less or more) different to what really suits yours nicely for example.

Speaking of tires...you might want the filled in look, but that rear size is pretty tall...just might want to make sure they are going to fit ok depending on how much of your 1/4's are cut out and how high/low the car sits. (probably ditto on the front as well)

#3 S pack

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Posted 26 June 2011 - 05:04 PM

I measured the front and rear track on my hatch today. Doing it by my self...I believe i got it fairly accurate but I'm not 100% happy with the accuracy.

Front
1422 1st measure
1412 2nd measure

Averaging them out... 1417mm

as for the rear it's a 9" that came out of a LX Torana.

Rear = 1380mm 1st measure, this is to the out side to out side of the drum.


Do these measurements seam correct ??



Now if they are correct, Working out my rim sizes, I need some help.

Some information to help work it out.

  • 1976 LX Hatchback
  • Track = Rear 1380mm, Front 1417mm
  • Im going with HQ stud pattern,
  • 330mm hoppers stoppers on the front.
  • I want/ would like, 235/55/R17 front and 255/55/R17 on the rear.
  • Guards will be cut, and Wilsons flaires fitted.
  • I would like to fill the guards as much as possable.

Now what widths, offset, back spaci should i go with ??


.


Wheel track is actually measured from centre of tyre tread to centre of tyre tread (obviously the steering on the front wheels must be in the straight ahead position) so you cannot get the actual/real track measurement until your wheels and tyres are on the car. The offset of the wheels you get will determine the track measurement.

#4 LH8VD69

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Posted 26 June 2011 - 05:05 PM

Im pretty sure track is measured from the centre of one rim to the centre of the other??

#5 cruiza

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Posted 26 June 2011 - 05:11 PM

Have you fitted the HQ stubs yet as that will in crease front track width by 50mm and lower the car by same. I found that ride height also plays a factor as the lower the car the less width of tyre you can run in the front, I could only just manage 225 on the front with HQ Stubs and ride height of 100mm to middle of cross member which is as low as I could legally go I had standard HQ mags with zero offset, I never checked it out but maybe with negative offset I could have run more but all the cars with big rubber up front have a higher ride height then I had

#6 S pack

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Posted 26 June 2011 - 05:32 PM

Im pretty sure track is measured from the centre of one rim to the centre of the other??


Well I suppose that should give you the same result as measuring from the tyres as the centre line of the tyre tread should match up with the centre line of the rim.
Just sharing the way I was shown to measure wheel track many years ago by a suspension expert, he said measuring the track from tyre to tyre was the correct way.

Cheers
Dave

#7 Lima31

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Posted 26 June 2011 - 05:37 PM

Easiest way is if your tyres are symmetrical ... get the tape measure tab on one tread edge near the centre of the tyre and measure to the same tread edge point on the other tyre - track is the width as measured between the centre of each tyre.

#8 ls2lxhatch

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Posted 26 June 2011 - 06:48 PM

The front track measurement will vary depending on the ride height. The widest track measurement will be when the lower control arms are horizontal.

Camber will also affect the track measurement as the top of the tyres will be closer together than the bottom of the tyres.

I assume the official track measurement is when the suspension is at ride height and is measured from the middle of one tyre to the midlle of the other tyre at axle height.

Chopper or Axistr should be able to confirm

Edited by ls2lxhatch, 26 June 2011 - 06:51 PM.


#9 LH8VD69

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Posted 26 June 2011 - 08:41 PM


Im pretty sure track is measured from the centre of one rim to the centre of the other??


Haha you will see we were posting at the same time so I didn't see your post . :)

Well I suppose that should give you the same result as measuring from the tyres as the centre line of the tyre tread should match up with the centre line of the rim.
Just sharing the way I was shown to measure wheel track many years ago by a suspension expert, he said measuring the track from tyre to tyre was the correct way.

Cheers
Dave



#10 S pack

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Posted 27 June 2011 - 05:53 PM

The front track measurement will vary depending on the ride height. The widest track measurement will be when the lower control arms are horizontal.

Camber will also affect the track measurement as the top of the tyres will be closer together than the bottom of the tyres.

I assume the official track measurement is when the suspension is at ride height and is measured from the middle of one tyre to the midlle of the other tyre at axle height.

Chopper or Axistr should be able to confirm


Yep, vehicle must be at full kerb weight and on level ground to get accurate track measurements. In fact all suspension measurements must be made under these conditions to be accurate.

This is how Roy showed me how to take wheel track measurements.

Track measurement is the distance between the centre of the tyres where the tyres contact the ground. Unfortunately it is hard to get a tape measure between the tyres and the ground. So take the measurements as close to the ground as possible.

On the front wheels take two measurements (because of toe in or toe out), one in front of the tyres contact patch and one behind, now work out the difference between the two measurements, halve the difference and add it to the shortest measurement. This adjusted measurement is the true wheel track measurement.

#11 Marshall

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Posted 27 June 2011 - 07:44 PM

So bacically I'm screwed. :Headbang2:

As the car is currently a rolling chassie, I can reinstall the diff and take measurements with the car on the ground but it wont be kerb weight unitll the rebuild is finihsed.


There must be some way to work out the measurements, so i can calculate the backspacing/offset/ rims width etc.

With the wheels and tyres fitted i can also mak out how much of the guard to cut.

.

Edited by Marshall, 27 June 2011 - 07:44 PM.


#12 Hybrid

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Posted 27 June 2011 - 10:08 PM

Have you fitted the HQ stubs yet as that will in crease front track width by 50mm and lower the car by same. I found that ride height also plays a factor as the lower the car the less width of tyre you can run in the front, I could only just manage 225 on the front with HQ Stubs and ride height of 100mm to middle of cross member which is as low as I could legally go I had standard HQ mags with zero offset, I never checked it out but maybe with negative offset I could have run more but all the cars with big rubber up front have a higher ride height then I had


It's probably not a good idea to fit HQ stubs unless you want to spend an axtra $400 on Harrop steering arms. The beauty of the Hoppers kits is that it is designed to work with the Torana stubs so that the steering geometry is not altered.

#13 ls2lxhatch

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Posted 27 June 2011 - 10:14 PM

So bacically I'm screwed. :Headbang2:

As the car is currently a rolling chassie, I can reinstall the diff and take measurements with the car on the ground but it wont be kerb weight unitll the rebuild is finihsed.


There must be some way to work out the measurements, so i can calculate the backspacing/offset/ rims width etc.

With the wheels and tyres fitted i can also mak out how much of the guard to cut.

.


You should be able to get accurate front track measurements by removing the front springs at setting the car at your preferred ride height. One way to do this is to replace the front shocks with threaded rod.

The rear track can be measured with the diff out of the car. The rear track on a live axle does not change with suspension travel.

#14 Marshall

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Posted 28 June 2011 - 06:38 AM


So bacically I'm screwed. :Headbang2:

As the car is currently a rolling chassie, I can reinstall the diff and take measurements with the car on the ground but it wont be kerb weight unitll the rebuild is finihsed.


There must be some way to work out the measurements, so i can calculate the backspacing/offset/ rims width etc.

With the wheels and tyres fitted i can also mak out how much of the guard to cut.

.


You should be able to get accurate front track measurements by removing the front springs at setting the car at your preferred ride height. One way to do this is to replace the front shocks with threaded rod.

The rear track can be measured with the diff out of the car. The rear track on a live axle does not change with suspension travel.


Cheers, :buttrock:

#15 ls2lxhatch

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Posted 28 June 2011 - 11:06 AM

Before measuring the front track check that your suspension bushes are in good condition and make sure you have fitted the front brakes you intend to run.

If you are checking tyre clearance then you need to be aware that with the UC caster the tyre is closer to the firewall than it is with the LX caster.

#16 Marshall

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Posted 28 June 2011 - 07:25 PM

hmmm, As the front seams trickier to work out, and the rear being somewhat fixed with the dimensions.

Ill remove the front springs and set the car down to the ideal legal ride height. But if I fit the Hopper Stoppers with HQ stud pattern.
How can I find out what the track is as I wont have rims that fit?

As for the rear, I have measured the diff out of the car. Rear = 1380mm, this is to the outside to outside of the drum. I can measure this again with the old Torana rims.

I found this in an old thread, I think i have it correct.

I measured my diff from one drum face to the other. Subtracted the diff measurement from the standard rear track specification and divide the result by 2 to give the offset required to maintain track.

Diff measurement 1380mm
Standard rear track LX RTS 1382 mm
1380- 1382 = 2 mm
2 / 2 = 0 mm

For the measurement between the centres of the tyres to be 1382 then centre of tyre must be 0 mm inboard of the hub +0 offset.
This verifies the +0 mm offset

So if I can adjust the tracking by a max of 25mm (12.5mm each side)

Am i correct in thinking that I should be good with 17 x9 rims on the rear (pending any clearance issues) +13mm offset and a 5 1/2 backspacing with 255's.

#17 Marshall

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Posted 28 June 2011 - 07:29 PM

And if the HQ stubs increase front track width by 50mm. I guess im looking at 17 x8 rims on the front(pending any clearance issues) -25mm offset and a 3 1/2 backspacing with 225's

#18 ls2lxhatch

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Posted 28 June 2011 - 07:42 PM

But if I fit the Hopper Stoppers with HQ stud pattern.
How can I find out what the track is as I won’t have rims that fit?


If you measure from the hub to hub (where the rim bolts up to the disc) then that measurement should be the same as a zero offset rim.

The same goes for the diff. If you measure the diff from drum face to drum face and add the offset for each rim then you should get the same measurement as you did measuring from the centre of the tyres on the diff.

HQ stub axles do not have any significant affect on track. The HQ discs do increase track but a HQ stub with Hoppers Stoppers will have the same track a the LX stub with the same Hopper Stoppers hub.

Edited by ls2lxhatch, 28 June 2011 - 07:44 PM.





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