The SERIOUS Wheel & Tire Thread

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The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Sun Feb 13, 2011 10:57 am

I think it's time we had a serious wheels thread.

Old Europe has this: http://www.fiero.nl/forum/Forum1/HTML/058236.html

But of course we can do better.

What's the goal of putting serious wheels on your car?
  1. To put as much rubber on the ground as possible, consistent with good contact patch loading.
  2. To produce correct steering geometry relative to the front contact patches

1. Going as wide as possible on the front end of a Fiero will result in a car that oversteers at the limit and will be difficult to dial in. Thus the rear tires should be as wide as possible while the fronts will be narrower, proportional to the weight distribution. We've covered this before. The weight distribution of a Fiero is about 45/55, which means that the front wheel/tire should be 0.8 as wide as the rear.
For 8" rear wheels, a 6.4" front would be ideal
8.5" rear -> 6.8" front
9" rear -> 7.2" front
9.5" rear -> 7.6" front
10" rear -> 8" front

2. Getting the offset right on the front wheels to produce good steering geometry is vitally important for a car with manual steering. Because of the high "offset" of the '84-'87 Fiero front knuckles (distance from wheel mounting surface to kingpin axis), the front suspension requires very high offset wheels in order to keep the "Dave point" of the front suspension in the correct location relative to the contact patch.

The effect of high offset wheels can be easily demonstrated on an early Fiero. The Mule is an '87 GT. It's currently fitted with Chrysler LeBaron 16x6 wheels on the front. These wheels are very high offset, and have reduced steering effort on the '87 to about the same as my Formula, if not a bit lighter. I should be able to measure the offset of these wheels next weekend.

Since the rear end of the Fiero limits the overall wheel and tire width, the correct width and offset for the rear is critical. This will vary by the diameter of the *WHEEL*.

The front of the Fiero has plenty of room for wheel and tire width compared to what it needs to keep the correct relationship with the rear width. The offset to keep the steering geometry correct is the critical aspect of a front wheel/tire fitment. This will vary by the diameter of the *TIRE*.

ALIGNMENT specs are also important, as the relationship of the tire to the strut body is affected by the rear camber adjustment, for example.

1984-1987 REAR: by wheel diameter and offset

16 inch wheels
16x8-25 (5x115) from early '90s Grand Prix, run with -1.5 degrees of camber. I have tested these on my car with the A-body hub carrier swap. The inner edge is 1/4" from the knuckle and the outer edge is about as far out as I'd want to see it with stock bodywork. I'll try to get pics this weekend.

17 inch wheels
17x9-45 according to WCF: http://www.westcoastfiero.com/faq/faq.html
Comparing to the 16" combo above, a 17x9-38 should also work.
I have not tested either of these; WCF did not specify 84-87 or 88 car or what alignment specs are used.

18 inch wheels
Going by the info above, 18x9-38 and 18x9-45 should also work.
Enkei PF01's for example are available 18x9-35 (5x114.3) and 18x9.5-45 (5x114.3) ( http://www.enkei.com/pf01.html# and http://www.enkei.com/size_chart/PF01.pdf )

1984-1987 FRONT: by tire diameter and offset

16 inch wheels
16x6-40 (5x100) from a 89-91 Chrysler LeBaron. I will measure the offset on a spare this weekend. These wheels have very high offset and work well with the '84-'87 steering knuckle.
IIRC, the pilot bore had to be enlarged to work with the Fiero hub.

16x7-?? (5x115) from mid '90's Bonneville. These are identical to the 16x8 Grand Prix wheels above except for the width and lip. I may be able to measure the offset on some spares this weekend.

17 inch wheels
17x8-45 according to WCF: http://www.westcoastfiero.com/faq/faq.html
I have not tested this; WCF did not specify 84-87 or 88 car or what alignment specs are used.

18 inch wheels
...
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Re: The SERIOUS wheels thread

Postby AkursedX » Sun Feb 13, 2011 11:50 am

Well I'll start this off by adding links to two sites that have somewhat pricey ($500-$1000 each), but full-custom wheels.

http://www.ccwheel.com/

http://www.kodiakracingwheels.com

When sticking with a 5x100 pattern, high offset fronts (45-53mm 7" wide) can usually be found by looking for Subaru Impreza wheels (~'03-07) Although Subies have a 56.1mm centerbore and Fieros have a 57.1mm bore, so if you order, you have to specify that. Rear wheels with 35-40mm offsets that are 8" wide can be found by searching for MKIV VW Jettas.

Wheels off the top of my head that I know that work pretty good are:

5Zigen Fn01R-c's (Although I head they might be discontinued in the needed sizes)
Enkei RPF-01
Work Emotion CR kai
TSW Trackstar

http://www.1010tires.com has a nice wheel search that lets you limit results by size, width, bolt pattern, and offset.
'88 Fiero GT- 3800 Turbo Best E.T. 11.36 Best MPH 121.50 (Sold and gone)
'04 RX8 (The new toy)
'11 WRX-My Daily Fun.
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Re: The SERIOUS wheels thread

Postby The Dark Side of Will » Sun Feb 13, 2011 1:34 pm

Thanks!

I had seen Kodiak and CCW previously, but the 1010tire search engine is a new one for me. I added some content to the first post.

While parametric searches for wheels are nice, I suspect that the offset requirements for the '84-'87 front end are going to push toward a custom 3 piece fitment.
I need to measure the kingpin angle and knuckle offset, but that's easier said than done.
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Re: The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Sun Feb 13, 2011 2:15 pm

Also have a really good link on Corner-Carvers about seated tires turning on the wheels due to installation techniques. It's interesting to see that the Enkei wheels mentioned above have serations on the bead of the wheel to try to prevent this.

http://www.corner-carvers.com/forums/sh ... hp?t=43850

Mounting techniques to reduce movement:

http://marktg.toyotires.com/file/rimslip.pdf
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Re: The SERIOUS Wheel & Tire Thread

Postby eHoward » Sun Feb 13, 2011 2:59 pm

Will, Do you have measurements of the various suspension pieces?

It would probably help to put the numbers into some sort of model. Doesn't have to be fancy. It could be Excel. Especially if you're looking at ordering a custom offset rim.
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Re: The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Mon Feb 14, 2011 11:24 am

Define "measurements"?

Really, the only things we need to know are allowable front spacing and allowable back spacing as a function of diameter.

I think I have allowable front spacing nailed down on the 16x8-25 combo, as well as max back spacing for a 16" wheel. What remains is to figure out what the widest workable combo is in each diameter and test or swing a wheel/tire clearance tool like this one: http://www.summitracing.com/parts/PHP-01201/
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Re: The SERIOUS Wheel & Tire Thread

Postby AkursedX » Wed Feb 16, 2011 10:11 pm

eHoward wrote:Will, Do you have measurements of the various suspension pieces?

It would probably help to put the numbers into some sort of model. Doesn't have to be fancy. It could be Excel. Especially if you're looking at ordering a custom offset rim.



There's this spec sheet on Kodiak's site that I would love to see it all filled out. http://www.kodiakracingwheels.com/kodiak%20spec%20sheet.pdf
'88 Fiero GT- 3800 Turbo Best E.T. 11.36 Best MPH 121.50 (Sold and gone)
'04 RX8 (The new toy)
'11 WRX-My Daily Fun.
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Re: The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Sat Feb 19, 2011 9:54 pm

LeBaron 16x6 wheels:

Outside width: 6 7/8" (measured)
Outside backspacing: 5 - 5 1/32" (!!) (measured)
Offset: 40 mm (calculated)

//

Here are the data items from the Kodiak Racing form:

Size & Fitment:
Diameter:
Design (Inside) Width:
Lip Edge ( (Outside width - Design Width)/2 ):
Design Backspace (measured to inside of bead; also measured backspace - lip edge):

Mounting:
Stud diameter:
Stud length from mounting surface:
Center bore diameter:
Center bore clearance:
Bolt Circle Count & Diameter:
Center bore chamfer width:
Center bore chamfer depth:

Caliper Clearance:
Inside Radius of Caliper from hub CL:
Outside Radius of Caliper from hub CL:
Caliper overhang (distance caliper protrudes outboard of wheel mounting face):
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Re: The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Sat Feb 19, 2011 9:55 pm

Next time I have the front wheels off The Mule, I'll measure the caliper dimensions for the LeBaron front rotor and rear rotor brake upgrades.

Interesting: http://www.1010tires.com/wheel.asp?whee ... F+Mach+Lip

Kyowa Designs KR628 is available with 5x100 pattern in 17x7-42 ($135), 18x8-35 ($180), 18x9-35 ($200), and 18x9-45 ($200)... sounds like a nice wheel combo for a Fiero. Unfortunately they're probably made in China. :(


Also, http://www.1010tires.com/wheel.asp?whee ... k%2FPol%2E

5Zigen FN01R-C is available with 5x100 in 17x8-35 & -48 ($220) and 18x8.5-48 ($245).
Also available with 5x114.3 pattern in 18x9.5-45 ($310).
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Re: The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Sun Feb 20, 2011 9:53 am

Grand Prix 16x8 wheels:
Outside width: 9 1/32 (measured)
Outside backspacing: 5 17/32 (measured)
Offset: 25.8mm
If I stop assuming my eyeball is well calibrated and assume that the design dimensions are 9" outside width and 5 1/2" outside backspacing, then the "published" 25mm offset pops out.

Here's what they look like on the car:

Image
Image
Image
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Image
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Re: The SERIOUS Wheel & Tire Thread

Postby jdv » Tue Feb 22, 2011 3:10 pm

Will are those supertraps ? They look good. How do they sound.
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Re: The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Sat Feb 26, 2011 7:49 am

Those are the shorty 2" SuperTrapps. They are completely uncorked, as you can see. The car is quite loud, but the ST's change the characteristic of the sound a bit, making it less "chuffy" (less flow noise) and more "trumpety". It sounds good.
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Re: The SERIOUS Wheel & Tire Thread

Postby Nashco » Thu Mar 03, 2011 6:33 am

Is it fair to say 88 rear fitment is the same as 84-87 rear fitment? They came with the same wheel size/width/offset, same hubs, same axles, etc. so they must have extremely similar wheel fitment. A friend of mine has one of these:

http://www.wheelworksinc.com/mountmate.html

I have two '88s in my possession. Another friend of mine (in Detroit) wants to know the absolute widest meats he can fit on his '88. Maybe with our powers combined we can provide some useful info for '88s.

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Re: The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Thu Mar 03, 2011 5:37 pm

Nashco wrote:Is it fair to say 88 rear fitment is the same as 84-87 rear fitment? They came with the same wheel size/width/offset, same hubs, same axles, etc. so they must have extremely similar wheel fitment. A friend of mine has one of these:

http://www.wheelworksinc.com/mountmate.html

I have two '88s in my possession. Another friend of mine (in Detroit) wants to know the absolute widest meats he can fit on his '88. Maybe with our powers combined we can provide some useful info for '88s.

Bryce


It will be next weekend (12th) at the earliest before I can take another look at my parts stash, but I have both an early and '88 knuckle to compare. The '88 as more "kingpin" angle than the early cars do, and thus can fit a wider wheel at all sizes down to 16". The difference between what an '88 can fit and what an early car can fit goes up with wheel diameter.
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Re: The SERIOUS Wheel & Tire Thread

Postby Nashco » Mon Mar 07, 2011 5:55 am

I suppose that's true, but it seems like you're talking a few mm. I suppose when you start getting to 18-20" wheels it might add up to an extra half inch or so, so worth mentioning and measuring if somebody has both to measure and compare.

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Re: The SERIOUS Wheel & Tire Thread

Postby Nashco » Mon Mar 07, 2011 9:23 am

This might save some time for '88 info. See Bloozberry's technical drawings, including '88 knuckles, strut, wheel, etc. in here:

http://www.fiero.nl/forum/Forum3/HTML/000116-9.html

Wow, to think he did all of that the old fashioned way instead of with a laser scanner. Impressive!

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Re: The SERIOUS Wheel & Tire Thread

Postby Atilla the Fun » Tue Mar 08, 2011 7:58 pm

For my rear, I've found American-made cast 17x9s, on a 5x114.3, +46, for $133 each. But I'm wanting to try their 10s, +23.8, for just $1 more each.
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Re: The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Wed Mar 09, 2011 12:32 am

Whose?
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Re: The SERIOUS Wheel & Tire Thread

Postby Atilla the Fun » Wed Mar 09, 2011 5:43 am

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Re: The SERIOUS Wheel & Tire Thread

Postby The Dark Side of Will » Wed Mar 09, 2011 5:48 am

Atilla the Fun wrote:http://www.ponyr.com/17_sizes.htm


Cool. Thanks. At $133 (and my car already having a 5x115 rear pattern), it might be worth grabbing one of the 17x10-46's for testing.

Edit: Of course they're as ugly as production Mustang wheels...

Edit Again: Although from this angle, they're not *too* bad...
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