The SERIOUS Wheel & Tire Thread

Real tech discussion on design, fabrication, testing, development of custom or adapted parts for Pontiac Fieros. Not questions about the power a CAI will give.

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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

The Dark Side of Will wrote: Does AST have universal struts? I see they have apps for Porsche and Subaru.
I don't know, but I should be able to get something that can work. I just need to match lengths and make the bottom fit. I can make top hats.
I was browsing the WCF site recently to see what things they have and found this: http://www.westcoastfiero.com/suspensio ... hocks.html

Looks viable, unlike some of the other things they do.
Wow I haven't seen that before. Awesome. Looks simple and strong.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

The Dark Side of Will wrote:
[ ... ]

At that point, save yourself frustration and buy a race car.
Just quoting this for the record.

Will is trying to discourage me so that he can have the biggest tires on a stock-bodied Fiero first. :friends:
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Re: The SERIOUS Wheel & Tire Thread

Post by The Dark Side of Will »

Lol. :wink:

If I wanted to hold the community back so that I would be the first one to do things, I'd just act like Rcheee... %)
The community would also never get anywhere.

The point I was making is that if your wheel rates are the better part of 4 digits, then your suspension stiffness is a LOT closer to the Fiero body's stiffness than it was stock. At that point, in order to keep making the car better, you'll need to make SERIOUS compromises in the car's streetability and daily-driveability with a tube frame/cage... At that point, just buy a race car that's already sorted, buy a kit or build exactly what you want from scratch.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

The Dark Side of Will wrote:Lol. :wink:

If I wanted to hold the community back so that I would be the first one to do things, I'd just act like Rcheee... %)
The community would also never get anywhere.

The point I was making is that if your wheel rates are the better part of 4 digits, then your suspension stiffness is a LOT closer to the Fiero body's stiffness than it was stock. At that point, in order to keep making the car better, you'll need to make SERIOUS compromises in the car's streetability and daily-driveability with a tube frame/cage... At that point, just buy a race car that's already sorted, buy a kit or build exactly what you want from scratch.
I do need to install a roll bar of some sort so I can run harnesses. I was falling out of my seats at Buttonwillow last weekend. Too much grip ;-). Might be some opportunity to stiffen the chassis with the bar or half/cage there but stitch-welding may make more of a difference. I don't really know where the weak points are.

After I redyno my motor on a Dynojet for NASA-compliant numbers, I'm going to request a reclassification for my motor swap and see if I can be competitive in TTC (preferably, as there's little competition locally) or TTB. TTD is dominated by Fulton Haight and his E36 M3... it's not unusual for him to put down lap times that would win TTB the same day.

At that point, just buy a race car that's already sorted, buy a kit or build exactly what you want from scratch.
Yeah that'll be the M3... the Fiero has just been ridiculously inexpensive to run compared to how the M3 will be, so I'm going to continue using the Fiero for NASA HPDE's until I've earned my competition license.

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Re: The SERIOUS Wheel & Tire Thread

Post by The Dark Side of Will »

You'd go for an M3 over an Elise/Exige?

I ran into a guy from Lotus of Bethesda at the Washington Auto Show back in January who said Lotus makes a subframe that bolts to the Elise/Exige body and allows mounting the Evora powertrain. If I fit into those cars, I'd be looking at one...
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Re: The SERIOUS Wheel & Tire Thread

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The Dark Side of Will wrote:You'd go for an M3 over an Elise/Exige?
Yes.

I haven't driven an Elise yet, but having another small midengine car like mine doesn't interest me much for Time Trials racing. The Elise is a poor choice for wheel-to-wheel since the chassis is basically unrepairable, and body parts are ludicrously expensive. The cost of consumables for that car is extremely low, but I don't know if it's low enough to make up for the extra costs for parts. to Power is also extremely limited on the Elise without boosting it, and then control is a serious problem.

If the FF 818 gets a spec class; then maybe I'll stay midengine and build one.

Otherwise, I'm sticking with time trials in the Fiero (once I get my TT license) and then eventually an M3 once I find one and build it.

I drove my friend's Cayman S at an autocross earliest this year. It felt more refined than my Fiero but also more dull and boring. I actually enjoy autocrossing the Fiero a lot more... and when we traded cars, he did too. So much so that he said he wanted his 5 year old Porsche to handle like my Fiero. That's probably not the case on a road course though ;-). Next time we're out we should have some open track and my cooling system problems solved, so we can see how our lap times compare.

BTW I've done 4 days of autocross and 4 track days on my current wheel and tire setup, along with ~3000 miles of street driving. Fronts and rears are at 50%, but I did have to flip the fronts (they wear on the outer 1/3; I need more camber).
I ran into a guy from Lotus of Bethesda at the Washington Auto Show back in January who said Lotus makes a subframe that bolts to the Elise/Exige body and allows mounting the Evora powertrain. If I fit into those cars, I'd be looking at one...
The subframe and drivetrain probably cost more than a used Elise.
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Re: The SERIOUS Wheel & Tire Thread

Post by The Dark Side of Will »

The drivetrain comes out of a Toyota Avalon... (or V6 Camry/Corolla)

Lotus just bolts on the TRD supercharger for the Evora S.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

The Dark Side of Will wrote:The drivetrain comes out of a Toyota Avalon... (or V6 Camry/Corolla)
The engine might come from one of those, but when's the last time Toyota made an Avalon/Camry/Sienna with a manual transmission?
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Re: The SERIOUS Wheel & Tire Thread

Post by The Dark Side of Will »

Not so long ago in the US... But I don't see it on the website now.

Honda still offers a manual trans V6 Accord.

I imagine the FWD Toyota 5 or 6 speed transmissions could be had from a JDM parts dealer (they still exist, right?), or maybe from a European Ebay source. The Lotus guy I spoke with said that the 5 speed is stronger.

At any rate, I think that once someone buys the subframe from Lotus, the rest of the powertrain could be done for significantly less than Lotus prices one way or another.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

I found another wheel that's available in staggered widths and offsets which work on the Fiero.

http://www.rotawheels.com/wheel.php?id=29

Rota GR6-2F are available with the 5x100 bolt pattern in the following sizes/offsets:

18x7.5, +40 to +45
18x8.0 +45 to +50
18x8.5 +15 to +20, +25 to +35, +40 to +48
18x9 +20 to +25, +30 to +40, +45 to +52

That's a very nice selection for 1984-1988 Fieros. The 18x7.5+45 will work well on the front of an 88, and the 18x9 from +35 to +45 is a great fit on the rear. I believe these wheels are special-order only due to the various offsets available.

The only drawback is that 225 is the narrowest streetable autox/track tire available for an 18" wheel, so that limits the maximum stagger to 225 front 275 rear (the widest that fits on 18x9) which gives a contact patch distribution of 45% front, 55% rear. That should be perfect for an engine that weighs about the same or less than the 2.8, but it's too much front tire for a V8 or the 3.4 DOHC. Moving down to a 17" wheel up front gives options ranging from 205 on up.

The ability to fit wide front rubber on the Fiero is fantastic. I fit a 255 on a 17x8+48mm with no clearance issues. With a lighter drivetrain (NA Ecotec?) the above wheels would be great for running a 255/275 stagger (48.1% front 51.9% rear)
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Re: The SERIOUS Wheel & Tire Thread

Post by The Dark Side of Will »

I've been musing about the ability to do something like 275 fronts/335 rears under an IMSA kit. As silly as the replica idea is, the MERA body supposedly has very wide fenders, and has production caliber engineering, unlike the IMSA. The same is true of the Enterra Vipre, but that's even sillier than the MERA.


Good find on the wheels.
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Re: The SERIOUS Wheel & Tire Thread

Post by Shaun41178(2) »

Are meats this wide going to make a big difference in handling vs having a better alignment job?

All I see is more weight from the wheels and tires when going that wide, plus the extra drag from a greater contact patch. I can only imagine trying to turn in a parking lot with 275 wide tires mated to a heavier rim than a stocker or something slightly bigger.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

Shaun41178(2) wrote:Are meats this wide going to make a big difference in handling vs having a better alignment job?
What do you mean by "better alignment job"? The alignment settings required depend on the tires. Different tire types, brands, and widths require different amounts of static and dynamic camber for optimal performance.

The only time wider isn't better is when you can't get enough heat into the tires to get them into the operating range. That's really just a problem in autocross and time attack, not in time trials or open track sessions (which last 20 min or more).
All I see is more weight from the wheels and tires when going that wide, plus the extra drag from a greater contact patch.
That's because all you do is race in straight lines....
I can only imagine trying to turn in a parking lot with 275 wide tires mated to a heavier rim than a stocker or something slightly bigger.
.... and the only time you turn the car is in parking lots. :P

At this point I think it's silly to try optimizing the performance of a Fiero without fixing the steering. After half a dozen track days and autocrosses, I can honestly say that the fast ratio power steering rack I added was the best thing I ever did to the car, tied with fieroguru's lateral link relocation kit, and staggered tires. Power steering will move whatever tires you throw at it.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

With the rear lowered a bit more now (should be just under 14.5 inches), I noticed some rubbing on the plastic bits of the inner fender from my 275/35/18s on 18x9ET45 wheels. This is with 350 lb/in springs and no rear swaybar. The interference is 1/8" or less.

I already ordered 475 lb/in Hypercos for the rear. I won't install them until I have stiffer fronts though. Hoping to get my front coilover setup done in the next month or so.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

I'm running BF Goodrich Rivals now since Hankook is changing the compound on the RS3s and they're out of stock everywhere. I still have 215/45/17 and 275/35/18. The rears seem to wear a lot better than the RS3s, but the fronts still shave a lot off the outer shoulders from each day at the track. I am designing some adjustable upper control arms so I can add more caster and camber, since I'm maxed out at a little under -1 deg camber right now. See: http://realfierotech.com/phpBB/viewtopi ... =3&t=17936

By the way the Rivals were HORRIBLE in the wet at Auto Club Speedway on March 1st. NOT a rain tire. I also hydroplaned a few times on the freeway at 55 mph.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

Not liking the BFG Rivals so much anymore. The sidewall flex is ridiculous. I can push the car around when it's parked and watch it wobble all over the place for a few seconds. I can actually feel undamped motion of the car when I come to a complete stop. It feels like the shocks are blown. These tires also flex enough under hard cornering to rub against my trailing links. Front wear is also kinda wonky; it looks like a wave. I think the tread is distorting under load. Based on what I've read about these tires, they have been optimized for cars with little or no camber. With some real camber (like my front -- not the rear), there may be some tradeoffs compared to a "normal" tire.

The only good thing I can say about them is they don't overheat like the RS3s, but overall grip is still pretty good. With the Hankook tire my fastest lap was almost always my first or second hot lap. After that, they would slide all over the place. Even a couple cooldown laps wasn't enough to bring them back. The Rivals build heat and grip progressively, but seem to tolerate a wider temperature range. They also "come back" after one or two cooldown laps if they are run too hot.

Now that I have better front grip (added more camber and caster with my adjustable control arms), I'm able to corner faster and work the rear tires more. I'm getting enough rear compression during roll that my tires are destroying the low-hanging parts of the inner fender liner on the inside and outside. I also have a slight amount of rubbing on the bottom inside edge of the top of the rear fenders. This tire and wheel combination (18x9-45, 275/35/18) is definitely the limit of width and diameter that will fit on a stock-bodied '88.

I'm going to reinstall my rear swaybar to see if that brings the body roll down enough to keep the tires from interfering with the body.

If a smaller diameter tire is used, it may still be possible to run a wider tire such as a 285/30/18 or 295/30/18. However, those require wider wheels (18x9.5 minimum).
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Re: The SERIOUS Wheel & Tire Thread

Post by The Dark Side of Will »

Interesting... good to hear actual experience using tires like those. That's exactly why I started this thread. Thanks! :-D

Are 275/30's on the market?
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

The Dark Side of Will wrote:Are 275/30's on the market?
Nope.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

Rubbing in the rear right wheel well from 18x9 (45mm offset) 275/35/18 with 475 lb/in springs and no rear swaybar. -2.0 deg camber. Need to check the ride height measurement.

It hits the metal inner fender, not just the plastic liner.

Image

I added the factory '88 rear swaybar now. Another track weekend coming up soon so I'll see if it still rubs.

I should clarify that this does not happen on the street. This is like 1.2Gs.
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Re: The SERIOUS Wheel & Tire Thread

Post by Series8217 »

275/35/18 on 18x9-45mm wheels in the rear and 215/45/17 on 17x7-48mm wheels with ~10mm spacers, under extreme cornering load:
Image

Static front camber is -3 deg with 12 degrees of caster. The rear has -2.5 deg of static camber, and fieroguru lateral link relocation brackets. You can see there is plenty of room for more front tire. However, the outside of the rear tire is rubbing on the inner face of the outer fender, and the inner shoulder is rubbing on the inner fender liner and a bit on the sheet metal. The inner sidewall also sometimes rubs on the trailing link a little bit. There is no room to go in or out with this setup.
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