PFF - Pennock's Fiero Forum, PDA Edition

Same size Tires on Front and Rear? (Page 1/4)

Dennis LaGrua

MAR 07, 03:21 PM

My Fiero now uses Goodyear Eagle sport 225 /45 x17 tires in the rear and 205/45 x17 tires in the front. I can no longer find the 205 45 x 17 Goodyear size for the front in the Eagle sport version and am wondering if the same size used on both front and back will work. Also wondering why GM chose to use two difference tire sizes on Fieros Anyone tried same size all around? Results in handling and ride?

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cartercarbaficionado

MAR 07, 03:43 PM

quote

Originally posted by Dennis LaGrua:

My Fiero now uses Goodyear Eagle sport 225 /45 x17 tires in the rear and 205/45 x17 tires in the front. I can no longer find the 205 45 x 17 Goodyear size for the front in the Eagle sport version and am wondering if the same size used on both front and back will work. Also wondering why GM chose to use two difference tire sizes on Fieros Anyone tried same size all around? Results in handling and ride?

the 88 Tangerine menace used a set of 87 rims with 225 tires.
honestly didn't make the handling worse other than the horrible bumpsteer which was corrected with alot of chamber and caster changes. then again we arent tracking it at high speed and power.
you have mostly 87s to my knowledge so the wider tires should be fine if you arent pushing it too hard or have the right offsets

1985 Fiero GT

MAR 07, 03:44 PM

Most Fieros had the same size all around, only the 88s had staggered sizes (205 and 215), all other years had either all 215 or all 195, the staggered tires was done for performance, the weight is balanced with more in the rear than front, therefore you need more tire on the rear than front to have a balanced car.

Patrick

MAR 07, 04:07 PM

The only problem using the same size tires along with the same offset wheels on an '88, is that the front tires will sit more "out" than the rear tires (due to the 88's front hubs). IMO, that looks awful. I've resolved this issue by using wheels with the proper offset for the front, and then using 25mm (1") hubcentric wheel adapter/spacers on these same offset wheels in the rear. Looks 100% better. I've been using these wheel adapter/spacers on two different Fieros for 15 years, with many of those years on an autocross track, with absolutely no issues at all.

olejoedad

MAR 07, 04:46 PM

quote

Originally posted by 1985 Fiero GT:

Most Fieros had the same size all around, only the 88s had staggered sizes (205 and 215), all other years had either all 215 or all 195, the staggered tires was done for performance, the weight is balanced with more in the rear than front, therefore you need more tire on the rear than front to have a balanced car.

All GTs 86-88 and the 88 Formula ran staggered tire sizes.

olejoedad

MAR 07, 04:49 PM

quote

Can you find 215's for the front?

I ran a 215/225 stagger on my Fieros for years with 15 inch wheels.
I now run 215/235 stagger on 17's (50 series) on my Formula.

1985 Fiero GT

MAR 07, 04:50 PM

quote

Originally posted by olejoedad:

All GTs 86-88 and the 88 Formula ran staggered tire sizes.

No, only the 88s.

85 GT got the 6"wide 14" rims with 215 front and rear, 86-87 got 15x7 215 front and rear, 88 GT/formula got 15/6 205 front, 15/7 215 rear with staggered tires.

My Fiero, 85 GT, tire size 215/60R14 for all, pressure listed front and rear, 125/70d15 spare tire.

My dad's, 86se, exactly the same

[This message has been edited by 1985 Fiero GT (edited 03-07-2025).]

pmbrunelle

MAR 07, 06:39 PM

quote

Originally posted by 1985 Fiero GT:
86-87 got 15x7 215 front and rear.

olejoedad is correct about staggered tires on 86-88 GTs.

The fastback cars (and Formula) received:
205/60R15 (front)
215/60R15 (rear)

The tires were staggered even though the wheels were the same.

[This message has been edited by pmbrunelle (edited 03-07-2025).]

1985 Fiero GT

MAR 07, 06:58 PM

quote

Originally posted by pmbrunelle:

olejoedad is correct about staggered tires on 86-88 GTs.

The fastback cars (and Formula) received:
205/60R15 (front)
215/60R15 (rear)

The tires were staggered even though the wheels were the same.

Oh ok, interesting, I guess that would have only added to the understeer early Fieros have, without other changes to the suspension like a rear sway bar like the 88 got, 84/5 would have had less understeer than 86/7, assuming that more tire=more grip

Dennis LaGrua

MAR 07, 08:04 PM

quote

Originally posted by olejoedad:

Can you find 215's for the front?

I ran a 215/225 stagger on my Fieros for years with 15 inch wheels.
I now run 215/235 stagger on 17's (50 series) on my Formula.

My wheels have a 36mm offset. I thought that you can't go too much wider than the 225/45 17 rear tires on my 87GT. You are running 235's. That IMO is a tight squeeze with stock struts. Should I try those? .