Different F/R wheel/tire sizing

Suspension and other discussion

Postby smog7 » Fri Apr 20, 2007 1:24 am

Would having different air pressures in the fronts and rears affect anything? maybe less psi in the front and more in the back?
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Postby CMS-GT4 » Fri Apr 20, 2007 2:35 am

Yes. I have played around with different tire pressure. I alway ran more in the rear so the rear gave a little quicker. Not a whole lot for daily driver. Maybe 32 F and 34 R. I think maybe even higher in the rear for an autox, but I don't think I would advise it for daily driving.
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Postby smog7 » Fri Apr 20, 2007 2:48 am

would following the recommended psi on the tire give the greatest mpg?
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Postby mike325ci » Mon May 07, 2007 8:22 pm

smog7 wrote:would following the recommended psi on the tire give the greatest mpg?

yes, that's what it's for.

mark d'addio runs crazy wide tires for the front on his evo than the rear for autocross. i forgot the exact width, you can find it on the web i'm sure. he's a multiple-time SCCA solo2 champion. wide tires in front = less understeer.

i'm keeping tabs on this thread. i want to know if it's possible to make the AT behave a bit more like a RWD car at corner entry/mid-corner. because it's definitely FWD-like in those areas. corner exit feels neutral/RWD-ish, so I'm cool with that.
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Postby smog7 » Mon Sep 17, 2007 2:05 am

just wondering but does anyone have any more info on this topic?? Im thinking about getting spacers for the rear. just for the looks, but im more about function then looks, so front spacers will most likely be ordered as well.
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Postby Roundy » Fri Jun 05, 2009 4:12 am

Grave dig

So what do people want from their GT4/Alltracs in terms of handling?

For my car i have always been chasing front end grip on the track, the understeer has always been horrendous.

I kept changing little bits at a time to remove it, and thus far everything has worked, it was progressively getting rid of the understeer.

However at my last track day i got the shock of HUGE oversteer on corner entry and mid corner, once the power was on the AWD did its work and settled it right down.

My setup (as best i know)

Front:
7kg/mm front spring (390lb/in)
-1*45" camber
1*56" caster (yes more)
0mm toe
poly bushes on the front end (minus swaybar oddly enough)
235/40/17 tyres on 17x8+35 wheels

Rear:
4.5kg/mm springs (250lb/in)
-0*45" camber
2mm toe in
Whiteline swaybar on full stiff (too much, have since put it to the middle)
poly bushes on the inner end of the control arms
stock diff mount
stock bushes for control arms (not for lack of trying, couldn't get them undone!)
235/40/17 tyres on 17x8+10 wheels (effectively, 25mm spacer each side)

Additional info:

No meaningful weight reduction at all, battery still in stock location.

I have a custom undertray on the front of the car, extremely doubt it makes a difference to lift/downforce on the front however.

The caster was achieved by rotating camber adjustable strut tops.

I have camber bolts on all 4 corners to get the camber spot on.

The oversteer was insane, it was waaayyyy too much, hence i have softened the rear swaybar.

My apex speeds were some 5-10km/h quicker than the previous setup, could get on the throttle harder and earlier.

I finally managed to get oversteer, so now i am going the opposite way and trying to gain some rear end grip.

After that, i need more power!
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Postby CMS-GT4 » Fri Jun 05, 2009 8:21 am

Great info on the caster. I might lean to turn my camber plates as well like you did.
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92 st185 (205 swap) | 03 350Z Track (sold) | 13 Pilot | 17 Mazda3
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Postby Roundy » Fri Jun 05, 2009 9:16 am

woops, didn't realise the name of this thread, i followed it from the Alltrac Handling FAQ.

I will also grab a measurement of my ride-heights from the centre of the wheels to the underside of the guards as well, which should be a 'measure' of the roll centres.
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Postby ccsouls » Wed Jun 17, 2009 6:12 pm

I would REALLY appreciate seeing some pics of the rotated camber adjustable strut top.

I don't comprehend how you rotated that strut top but maintained 1.45 degrees of camber.

I am close to your setup now and looking to get rid of just a little more understeer.

I appreciate your post. Thank you.

See if you can also post that setup on the correct thread for others.
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Postby CMS-GT4 » Thu Jun 18, 2009 12:42 am

[quote="ccsouls"]I would REALLY appreciate seeing some pics of the rotated camber adjustable strut top.
[quote]

http://www.alltrac.net/phpBB2/viewtopic ... ht=#294703
Coldiron
92 st185 (205 swap) | 03 350Z Track (sold) | 13 Pilot | 17 Mazda3
www.noritoy.com | noritoy.deviantart.com | http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=19891
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Postby Roundy » Thu Jun 18, 2009 3:19 am

CMS beat me to it :)

I also have camber bolts with it to get the camber spot on as well.

I haven't been using the strut top for camber adjustment.
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