Track sizes

General Bellett, Gemini 75-98, Piazza 81-93, Bellel, Florian, 117 Coupe, Minx, Aska technical discussion.
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Track sizes

Post by eyecon » Tue May 01, 2012 3:35 pm

Getting my car registered in the ACT so I've got this engineer going over the car and I'm having to jump over a few hoops (more like bending over and legs spread wide open if you ask me). At the moment it's too low, there's oil coming out from somewhere at the top of the gearbox, the diff and seals are shagged, blah blah blah.

One of the things the engineer has asked is the track sizes/dimensions for the Piazza. Apparently he thinks there are 3 different track sizes. Does anyone know the 3 sizes, and which one applies in Australia?

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Post by Bugle » Tue May 01, 2012 8:54 pm

The track width for Australian delivered Piazzas is 1355mm front, 1380mm rear.

Older Japanese ones with 13 inch rims had a narrower track, but obviously doesn't apply here.

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Post by eyecon » Tue May 01, 2012 9:09 pm

Excellent Bugle. Thanks and I will pass that on. I wonder what the other two track measurements were. I'll try and dig that out from somewhere.

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Post by eyecon » Tue May 01, 2012 10:09 pm

Did some scratching around on isuzuperformance site.
'83-'87 non turbo US models: front 1356mm, rear 1369mm.
'83-'89 turbo US models (including '87 RS): Front 1353mm, rear 1384mm
'88-'89 non turbo US models: Front 1353mm, rear 1384mm

Bugle as you can see the Aus spec differs in few mm front and rear to the US spec. I can understand the rear being different due to GMH's infinite wisdom to change to the banjo style. But why would the front be out by 2mm, or this just a inch-to-mm conversion anomaly?

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Post by Bugle » Wed May 02, 2012 12:19 am

US turbo and 88/89 non turbo had the banjo rear end too, which would probably explain why the 83-87 non turbo rear track is a fair bit narrower.

Front track would vary that much from a slight change in ride height, or even manufacturing tolerances.
Rear track doesn't change with ride height but 4mm difference might be within manufacturing tolerances too. Or it just got messed up in conversion to imperial and then back again.

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Post by eyecon » Wed May 02, 2012 7:07 am

Interesting. Didn't realise US used the banjo diffs as well. Now I'm curious as to what the JDM track dimensions were.

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Post by Bugle » Wed May 02, 2012 2:46 pm

I've got some JDM sales brochures
1984 (3 link only)
1355mm front, 1370mm rear for 14" rims (4ZC1-T & G200W)
1345mm front, 1355mm rear for 13" rims (G200Z)

1989 Piazza Nero brochure
Handling by Lotus (5 link rear) 1355mm front 1380mm rear
Irmscher (3 link rear) 1360mm front, 1370mm rear

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Post by eyecon » Wed May 02, 2012 7:13 pm

Thanks Bugle. Just found out the front track is 10mm too wide, and needs to be brought back to factory track width. I bought the car with the Hopper Stoppers Gemini front brake upgrade kit (300mm VT disks and calipers) already installed. My mechanic seems to think he will be able to do something to bring it back to factory width. Don't know what he's thinking of but I can already think of a solution and it is related to the current camber settings on the car, and is therefore nothing to do with the brake upgrade.

With the front tyres scrubbing badly on the inside edge due to it's current camber setting the obvious solution will be to re-adjust the upper control arm to try and bring the camber setting closer to 0 degrees. This should bring in the front track enough to make the difference. I'm led to believe there is some room for adjustability in the upper control arm. Is that right archangel? Two issues will then be fixed at the same time if that makes sense.
Last edited by eyecon on Thu May 03, 2012 1:40 pm, edited 1 time in total.

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Post by Bugle » Thu May 03, 2012 1:32 pm

You probably mean 'camber'. The track would decrease if you reduced negative camber as the bottom of the tyres would come in as the top gets pushed out. You can get adjustable ball joints with slotted mounting holes to adjust camber.

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Post by eyecon » Thu May 03, 2012 1:37 pm

Bugle sorry mate I did mean camber. Any reference I made to caster please disregard. I'll edit my previous post.

If I can't get enough adjustment in the upper control arm, or If I couldn't be bothered with increasing the slot in the upper control arm, then I'd be interested in these adjustable ball joints. Where would I find these parts for future reference?

But of course all this talk of camber and track width probly won't be an issue once the car is raised due to legal requirements. ACT compliance won't pass the car at it's current ride height. So once the car is raised the camber and track problem might just fix itself. I'm yet to receive advice as to how much I will need to increase the ride height. I know the car was lowered 2" on the front, so I hope I won't need to come up the full 2".

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Post by IZU069 » Thu May 03, 2012 2:04 pm

Scrubbing is more likely to be bad alignment - especially toe-in. (Or as per my Wasp with a broken LHS strut bar so the LH wheel moves back under braking.)

Also bad geometry (bent arms; differences between LH & RH settings; incorrect strut-bar adjustment) and worn tie-rods etc.

Fast cornering also wears.

Neg camber shouldn't scrub too much (especially with radials) but that should be more even across the tyre rather than just the inner edge.

Not that I have experience with the Piazza. (Maybe GMH's changes also effected things?)


As a rule, I set my Belletts, Wasp, Florians from their st'd spec of about +1.30' camber & +1.30' caster to ~0 camber. (Toe in spec = ~3mm.)
The caster I leave as that affects the "self centering" characteristic , plus is integral to the frond end design (camber on turns etc).


And BTW - whenever I get new tyres, I get a wheel align. (It's cheaper than buying new tyres again in a few months...)
For Pete's sake, don't get them aligned too long after new - I read one forumer aligns at his expected tyre "mid-life" point. Idiot! Once a tyre wears wrong, nothing corrects it other than a skim. You are supposed to PREVENT the tyre wear from new.
(And tyre rotation merely accelerates ALL tyres to the maximum wear. I never rotate, except that new tyres may go to the front, and then it's RF to RR & LF to LR - I never swap sides!)
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Post by eyecon » Thu May 03, 2012 2:14 pm

I'm probably up for 2 new tyres up front, but I'll deal with that once the ride height is sorted out. Then I'll get the wheel alignment done with the new tyres.

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Post by wedgenut » Fri May 04, 2012 7:08 pm

As previously mentioned the track width will alter with suspension arm angle. Narrowest track width is with car off the ground and wheels hanging at full extension. Conversely the widest track width is with maximum load on the front suspension. To give you some idea, I fitted 7" mags with a slightly too big offset and the tyres were clear of touching in normal use but when raised off the ground and wheels hanging the side walls were JUST touching the front shock tube and they don't like that at the testing station. I did explain I rarely drive around with my wheels off the ground. Wheel spacers are one fix but again frowned on so I fitted Rodeo front shocks. A double win, they are about 15mm shorter on full extension and gave me 5mm clearance from the shock tube on full extension, problem solved and the gestapo were happy. The real bonus is that they are a higher pressure than standard Piazza so no body roll, no bump steer, less understeer. Altogether a really successful change. Only one modification required and that is to drill out the existing lugs on the upper control arm from 10mm to 12mm.

The point here is that 15mm less in vertical drop gave me 10mm wider track with wheels hanging so if you reduced the amount of your lowering it will bring the track back in a bit. I would jack the thing up on a trolley jack under the cross member until you have say 25mm more clearance measure at the front guard lip and roll it back and forward with the jack still in place to allow the tyres to settle and see what you have then. That should give you some idea of what you need to achieve.
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Post by eyecon » Fri May 04, 2012 10:13 pm

I like the idea of Rodeo shocks Wedge. I'll use this as a backup if all else fails. What did you use for springs on the Rodeo setup?

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Post by wedgenut » Sat May 05, 2012 3:59 am

Didn't touch the springs, they are standard springs that had already been shortened by 25mm, can't go too low here or car becomes a target for every gang member in a blue uniform, you have the canary we have the pink sticker because our gang members are all gay
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