18” wheels (Page 1/2)
sdgdf JAN 12, 11:38 PM
I’ve looked through a bunch of archived threads and only gotten confused. I want 12” corvette brakes on my 88 coupe, and that means upgrading from the stock 15”s. That means I want some decent wheels and tires.

Coilovers and going beyond 16-17” on the back, I should be able to run 265 or 275 wide on the back? I found wheels that come in 8” and 9” wide, they’re both 35mm offset though. What I read indicated +35-38 offset on the back should be fine but will that be alright up front?
fieroguru JAN 13, 06:53 AM
Please specify 84-87 or 88.
For example, on the 88 rears you need to go 18" to clear the knuckle for 9" wheels... unless you want or need the rear wheels to stick out about an inch past the body.

sdgdf JAN 13, 08:42 PM

quote
Originally posted by fieroguru:

Please specify 84-87 or 88.
For example, on the 88 rears you need to go 18" to clear the knuckle for 9" wheels... unless you want or need the rear wheels to stick out about an inch past the body.



Ok I mentioned 88 coupe, yup it’s for an 88. Besides that will +35mm offset look alright on the front? If not can I fix it with spacers or something?
fieroguru JAN 13, 09:59 PM
If you want the front wheel protrusion to be stock from the 15's, then you need a 7" wheel with a 45mm offset. The 35 mm offset sticks the tires out about 1/2" further. What looks good to 1 person looks like crap to others, so it is best to reference actual dimensions or look at pictures, find what you like and then ask for wheel details.

On my car, the front and rear wheels are flush with the beltline molding at the top and it gives the car a pro-touring stance which I like, but again opinions vary.

[This message has been edited by fieroguru (edited 01-13-2023).]

Raydar JAN 14, 10:14 PM
If the front is lowered, it tends to make the wheels look more "tucked under".
I have always preferred 38-48 mm offset on 7" wide wheels, for the front of an 88. But I realized I could live with a 35 offset, provided the rears are wide enough, and the front is low enough.





[This message has been edited by Raydar (edited 01-14-2023).]

zkhennings JAN 14, 10:40 PM
I am debating whether I want to run an R18 9.5” wide rear wheel or R17 9”, both paired with a 17” front wheel. My car is an 85 with adjustable coilovers in the rear. I think it would look better with an 18 in back but tire prices jump like crazy going from 17 to 18. Is there any performance benefit? Tire would be 255 regardless. 18” tire would be a larger diameter so a larger contact patch due to contact patch length, but more unsprung weight, about an extra 2 lbs plus whatever extra the tire would weigh with its additional diameter.
Raydar JAN 15, 04:02 PM
Going from a 17 to an 18, you could go down to a lower aspect ratio. (255/45-17 to 255/40-18), to maintain a similar diameter.
That, unless you have the capability of reprogramming revolutions per mile. Otherwise, your speedo will read low, compared to your real speed.
Also, a 40 series tire will ride a good bit harder than a 45. And that's not even considering the unsprung weight that you menioned.
It's why I have stuck with 17s. (I do 235/45s in the rear and 215/45s in the front.)

Just my opinion. Others may differ. I tend to like to keep my spinal disks uncompressed, and my fillings intact.

[This message has been edited by Raydar (edited 01-15-2023).]

cvxjet JAN 15, 10:01 PM
I want to chime in here; A) The Fiero does not have a very advanced suspension design- The arms and spindles are steel (Heavy) and the shocks are not electronically controlled. So the Fiero does not do well with HEAVY wheel/tire combos. I took 3 lbs off of each rear and 6 lbs off each front when I installed my 16 x 7 wheels and 205 & 225/55 tires- it really improved the feel and performance of the car. Keep your wheel/tire combo as light as possible (Bigger wheels add a lot of weight)

B) Back in the 80s, a co-worker won a Shelby Charger...It was one of the first cars to use really short-sidewall tires. He was driving thru a cloverleaf onramp and hit a 2 x 4 which stripped the tire off the wheel, so that he ran off the on-ramp and crashed. I made a decision to never go below a 4" sidewall.

Everyone goes crazy for the biggest/widest tires and the biggest brake discs- keep it light and the car will be better. I used to want gigantic wheels and tires on my Mustang & Firebird, but when I switched to those lighter wheels and tires on the Fiero, I really finally understood what Colin Chapman (Lotus) meant when he stated "Add Lightness"

[This message has been edited by cvxjet (edited 01-15-2023).]

sdgdf JAN 16, 05:15 PM

quote
Originally posted by Raydar:

Going from a 17 to an 18, you could go down to a lower aspect ratio. (255/45-17 to 255/40-18), to maintain a similar diameter.
That, unless you have the capability of reprogramming revolutions per mile. Otherwise, your speedo will read low, compared to your real speed.
Also, a 40 series tire will ride a good bit harder than a 45. And that's not even considering the unsprung weight that you menioned.
It's why I have stuck with 17s. (I do 235/45s in the rear and 215/45s in the front.)

Just my opinion. Others may differ. I tend to like to keep my spinal disks uncompressed, and my fillings intact.




Tires I’m looking at on fitmentindustries are a lot more common in 35 and 40 series for 18” wheels, I’m really looking at 235/40/18 for the front and 255/35/18 rear. I haven’t plugged that into a diameter calculator yet but that sounds smaller than the stock tires. My speedo is already off with the 3800sc and my stock wheels/tires so it’ll need calibration anyways. Smaller diameter tires will have the effect of giving it quicker gearing too, correct?

I’m about ready to get these, gonna wait for advice from the people here though. Those tires on 18x7.5 38mm offset up front, 18x8.75 33mm in rear. Thoughts? I haven’t really seen that kind of combo in the old threads I’ve been looking at.
cvxjet JAN 16, 10:02 PM
I want to say that on my Fiero GT Getrag 5 speed, the 225/55-16s make the speedo as close to perfectly accurate as possible. Diameter of these are 25.75" vs the stock 86-88 GT rear tire diameter of 25.15".

Here is the wheel fitment graphic that someone made up years ago for our Fieros- may be helpful;

(Note: To view it large, right click and then "Open in new tab")

[This message has been edited by cvxjet (edited 01-16-2023).]