Im thinking about trying some 275 65 15s on the rear of my 88, does anyone know what the biggest tire is that will fit?
Im using stock honeycomb rims
The front, im goign to try the 225 50 15s on 86 rims, just cause I have them. If they dont fit, I dont know what to do, I cant find the front 88 rims anywhere

Wow, a 275 is a pretty wide tire. Mounting that on a 7" rim would not be a good idea.

Besides it not being too safe, you think a 275/65 rear and 225/50 will look good?

The 275/65 is gonna be a pretty tall tire, and the 225/50 will be rather low profile in comparison.

You ever see an old Camaro or Mustang with the back jacked way up and tiny tires in front....?

Your Fiero will look really stupid. A 225 would be a nice fit for a 7" rim.

The largest I have ever seen on a stock Fiero rim would be a Pirelli 235, good luck finding them as they are not a common tire size. Your best bet would be online for them and prepare to pay around $250.00 a tire.
The most common around here for a stock rim would be a 225, but most seem to go with a 195-205 on the front as this makes stearing a bit more easy since you do not have the extra width making a non power stearing car like the Fiero a real bear to turn if you have that wide of a tire up there.

hey I have an 88 formula with stock rims, I have 235/65/15 in the back and 215/65/15 in the front, looks fine and drives fine, but I wouldnt go any wider cause then you might feel the car moving around on your tires if you know what I mean. To my opinion 235 is about as much you should go on a stock rim.

I have 265/50/15 Dunlop GT Qualifiers on my 88 formula and they fit fine. However, what ever you do make sure that the sidewall height of the front and rear are the same or very close. I learned the hard way. My fronts are 225 50 15, my old rears were 245 50 15 a great combination. Handled like a dream, better acceleration (smaller diameter than stock). However, last year I needed to replace the rears and couldn't get the 245 50 15 and the company could not tell me when they would be made. So I searched for a replacement and determined the 265 50 15 would work, boy was I wrong. The problem is that the sidewall difference between the front and rear was too great and the car handle horrible. I mean is was nasty, when you passed a car the rear end would sway and it felt like you would spin out at any time. Needless to say my clucth went out so I didn't put many miles on them (haven't had time to replace it maybe time for an engine swap). I have to look but I think it was less than a 1000 mi, didn't even like driving it. I would be willing to sell them if you are interested they are like new. I think with the proper front tires they would be fine, lots of tread on the road. By the way my suspension is stock.

you handling issue is most likely due to using a tire much wider than designed for stock width rims.. the sidewalls are bending way out of shape to fit 265's on 7 inch rims

One thing to keep in mind about rim width and tire size is that the tire width is not the only criteria, the sidewall height also plays a factor. Look at factory specs and the smaller the aspect ratio the closer the rim width must be to the tire width. The larger the aspect ratio the smaller width rim that is approved for use. The tires in question have an approved rim width of 7.5 to 9.5 ". I do realize I am a little shy of 7.5" but I'm not so sure it has any effect. Please enlighten me on the physics of why you think this would be the problem with handling. It seams to me that side wall height and stiffness between the front and rear play a much largerer role.

when the tread width is much wider than the rim you get a mushroom effect - this effect makes it very easy for the sidewall to flex allowing the tread to follow changes in the road surface - when the tread width is much smaller than the rim you get too much sidewall touching the road surface when cornering .. your optimal handling is with the ratio of the rim width too the tread with is closest to 1:1

275/65-15?!?!?!

Do you realize that wheel / tire combo would be FOUR INCHES taller than a stock 215/60-15? That'll jack up the back of your car 2", and you can give up any thought of wheel well clearance if you've lowered your car.

Just curious, though. Where did you find 275/65-15 tires? Tire Rack lists nothing in that size - not a single tire.

For all practical purposes, AFAIK, a 245/50-15 is the biggest you can go on a stock 15x7 wheel. You might be able to go wider with a taller tire, but the 245/50 is close to the height of the stock tire (0.3" shorter radius).

There are many who say the 245/50-15 is too big and unsafe, but it's within the specs for a 7" wide wheel according to Tire Rack. Still, going much wider than that is seriously pushing the limits.

having run a variety of tire sizes on my last fiero I can say one thing for sure.. real wide tires on the rear on stock rims (max i used was 245/50/15) are great for straight line but the 235's and 225s' handled better - ultimately i settled on 235/50/16's with beretta gt rims..

for this reason i'll always stick to the middle range of recommended rim tread with for the rim size..

[This message has been edited by Kohburn (edited 09-10-2004).]

Kohburn I still to not understand how this mushroom effect changes sidewall stiffness. I realize it will affect the contact patch but why would this change stiffness? Wouldn't rim width play a larger role in contact patch area not sidewall stiffness? I would think sidewall stiffness is more a function of air pressure, sidewall height, and material stiffness.

quote Originally posted by montage: Kohburn I still to not understand how this mushroom effect changes sidewall stiffness. I realize it will affect the contact patch but why would this change stiffness? Wouldn't rim width play a larger role in contact patch area not sidewall stiffness? I would think sidewall stiffness is more a function of air pressure, sidewall height, and material stiffness.

its also a factor of the angle/curvature of the sidewall itself..
without even looking at sidewall flex.. lets just look at them as rigid planes.. under side load the farther they aspect ratio from 1:1 the more the tread angle changes from the wheels angle.. with an uneven road surface traveling in a straight line this would actually translate to moving the wheel side to side on the road relative to the tires path

what I discovered in practice on daily driver is that the wider it is beyond the rim that the non smooth nature of many older roadways caused the rear end of the car to wander side to side and the tread angled to match the road surface..

I found the 275's in a goodyear at tire kindom (NTB). I had the 225's all the way around on my 86, They fit perfectly in the front, but the rear of the car had a TON of wheel well space. Maybe it was a suspension problem, though all seemed well. Ive got to get these 225s on the 88 and see how it sits, and determine where to go from there. I want something that will fill the space, but still give a lot of tread width.

You are jokeing right?
Dont do anything wider than 225 on a 7inch wide rim. Will they fit? Yes. But that dont mean they will ride or perform well. Yes people put wide tires on narrow rims and they like them but the tire manufacturers all say the same thing. For a sports car with an aspect ratio lower than 60 dont go wider than 225 on a 7 inch rim. The tires are the most important part of the car, do it right.
If you want dide tires you haveto get wide rims.
The fronts are one inch less so you need to take 25mm off the width of the front tires, so 195-205.

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