tire height for 18" rim with eibach pro's

im getting 18" Z06's all around on my WS6. it sits really nice right now with the STOCK suspension. i plan on putting in some Eibach pro's that i got a while ago off here. i just need some cheap tires that will fit. i know the wheel well gap will be pretty minimum with the bigger wheel and lowering springs. i found a set of tires for like $135 a tire. they are 275-40-18s. would that be too tall of a tire to fit in there? or would it be good. i would like to go more low profile but all the tires that are 275-35-18s or 275-30-18s are a lot more money. any help is appreciated.

You're going to end up with a tire that is 1" larger in diameter than stock. That lifts your car 1/2" higher off the ground, and puts the tire 1/2" further up into the wheel wells, increasing the chances of rubbing. Your speedo will read about 2MPH low at a true 60MPH.

The 275/35 is actually a bit smaller in diameter than stock. A 275/30 (if it existed) would be way too small in diameter. 285/35-18 seems to be the best match. Tire Rack has 285/35 Sumitomo's for $166, and 275/35 BFG g-Force Sports for $159, Dunlops and Kumhos for similar prices. Have you checked with the site "Supporting Vendors"?

i have 18s all around, and i never had a problem....just dont put more than one person (including yourself) in the car :)

Doesn't the tire size really depend on how wide the rim is? I have 295/35/18 with the Prokit and it fits well. Tight but fits.

I just put 275/40/18's on my 97 Z28 with stock suspension. It clears fine, but as Injuneer stated, it now sits 1/2" higher than before. The clearance in the wells is fine, but it looks like a monster truck now.

The clearance has a lot to do with the offset (56mm on mine, but it will be different for your T/A). My project over Christmas is to put my Hotchkis TVS suspension kit on, including the 1" drop springs. I am hoping it will clear with the taller tires. Your Eibach springs are rated at a 1.3" drop I believe, while my Hotchkis are supposed to be a 1" drop.

Anybody have past experience with the 1" drop and the 275/40/18's fitting?

There have been some recent threads for rubbing when you have ground effects and the 275/40/18 tire instead of the 275/35/18, so beware of that.

I will be posting pics and let you know how that setup works for me.

You're going to end up with a tire that is 1" larger in diameter than stock. That lifts your car 1/2" higher off the ground, and puts the tire 1/2" further up into the wheel wells, increasing the chances of rubbing. Your speedo will read about 2MPH low at a true 60MPH.

The 275/35 is actually a bit smaller in diameter than stock. A 275/30 (if it existed) would be way too small in diameter. 285/35-18 seems to be the best match. Tire Rack has 285/35 Sumitomo's for $166, and 275/35 BFG g-Force Sports for $159, Dunlops and Kumhos for similar prices. Have you checked with the site "Supporting Vendors"?


Fred is correct again. With an 18" rim, I too would recommend a P275/35R18 tire as the rolling diameter is almost exactly what a P275/40R17 or a P245/50R16 is. My shop has lowered many F-bodies and we have never been able to make a P275/40R18 work without rubbing, either lowered or non-lowered. The only way that I am aware of that you can keep a P275/40R18 from rubbing is to install adjustable shocks/struts like GMMG did to my ZL1. That is why they had Penske adjustables specially made for the ZL1 Supercars. In talking to the guys at GMMG, they told me that that was their solution to the problem anyway.

I just put 275/40/18's on my 97 Z28 with stock suspension. It clears fine, but as Injuneer stated, it now sits 1/2" higher than before. The clearance in the wells is fine, but it looks like a monster truck now.

The clearance has a lot to do with the offset (56mm on mine, but it will be different for your T/A). My project over Christmas is to put my Hotchkis TVS suspension kit on, including the 1" drop springs. I am hoping it will clear with the taller tires. Your Eibach springs are rated at a 1.3" drop I believe, while my Hotchkis are supposed to be a 1" drop.

Anybody have past experience with the 1" drop and the 275/40/18's fitting?

There have been some recent threads for rubbing when you have ground effects and the 275/40/18 tire instead of the 275/35/18, so beware of that.

I will be posting pics and let you know how that setup works for me.

I think all f-bods have a +56mm offset with 18inch rims , its no different for a lt1 Z28 to a LS1 firehawk.. or if it is, somebody can clarify this, cuz i also will be gettin 18inch c5's on my car and its pretty lowered, jus dont know if its 1.8inch or 1.3inch..

As promised, pics are now up

They include new Hotchkis 1" drop springs, new front and rear swaybars, new lower control arms, new panhard rod, and new strut tower brace.

Now the 18's look proper - and to all those who say 275/40/18's don't work, I would tend to disagree - 273/35/18's do retain stock overall diameter, but I think these 274/40/18's fill up the wheel wells very nice.

Pics - http://groups.msn.com/GMsFbody/30thz28.msnw?Page=3