345 tires and IRS

Hey everyone,

I have been doing a ton of research on seeing if its possible to fit a 345 tire on these cars with the IRS. The tire in question is the 345/40/17 Toyo Tq.

I have found some info supporting that this is possible, but I would still like some input. Has anyone managed this with any variation of wheel size/backspace, fender rolling, low profile bolts?

And as to why would I try such a tire? The car is 800+whp and I really don't want to grind my knuckles for a 15 inch setup since its strictly a street car. I also am looking for alternative options for MT et street R'/M&H. And I think it kind of looks good.

Here is some of the stuff I have found while scouring the internet. Yes I know these are car's with 18 inch 345's, but the width is similar.

https://www.svtperformance.com/threads/pics-mickey-thompson-345s-on-11s-on-irs.596540/

The biggest I recall seeing on an IRS car is a 335/xx/18 R888 on a 10.5" width wheel. I wanna say he had longer wheel studs and 1/4" spacers in addition to the low profile bolts. I don't think fender rolling would be necessary unless you're lowered although 40 is getting to be a beefy sidewall with a 345 width. I'd play that by ear since it's a "no turning back" scenario.

TerminatoRS said:

The biggest I recall seeing on an IRS car is a 335/xx/18 R888 on a 10.5" width wheel. I wanna say he had longer wheel studs and 1/4" spacers in addition to the low profile bolts. I don't think fender rolling would be necessary unless you're lowered although 40 is getting to be a beefy sidewall with a 345 width. I'd play that by ear since it's a "no turning back" scenario.

Click to expand...

Well the thread and video I posted up above have cars sitting on a 345. less sidewall and bigger wheel though. I guess I could be a guinea pig and just try it. I would be mounting them to a 17x11 +20 offset/6.8 Backspace welds. I have extended wheel studs. I also have spacers ready if need be, but I think the offset should be fine without.

I am just really hoping someone has tried a tire out this big before.

345 on 18 x 11.5 wheel

Blackedout said:

345 on 18 x 11.5 wheel

Click to expand...

What did you have to do, if anything to make them fit?


Sent from my iPhone using the svtperformance.com mobile app

Just low profile IRS bolts..

I assume the fenders are rolled as well...? My relatively average 315's rub the IRS subframe when I unload the rear suspension. 345's for me would probably create a gap on the wheel studs between the inside face of the rim and the rotor hat.

TerminatoRS said:

I assume the fenders are rolled as well...? My relatively average 315's rub the IRS subframe when I unload the rear suspension. 345's for me would probably create a gap on the wheel studs between the inside face of the rim and the rotor hat.

Click to expand...

I have not rolled the fenders yet... 1/4” spacers installed so when the rear is unloaded they don’t rub..

Blackedout said:

345 on 18 x 11.5 wheel

Click to expand...

This is what I was looking for. Do you have any more pics? How does the car drive on 345's? I think I am going to try a 345 toyo tq on my welds now...

Bumping this to see if anyone else out there is running some wide meats. I am very close to pulling the trigger and trying to make the 345 toyo tq fit with IRS.

TexaSTI said:

Bumping this to see if anyone else out there is running some wide meats. I am very close to pulling the trigger and trying to make the 345 toyo tq fit with IRS.

Click to expand...

im interested in this too, getting my car back soon with a new twin turbo set up and need to get it to hook

Here is a thread from 05

https://www.svtperformance.com/threads/lets-see-those-wide-meats.192112/

TexaSTI said:

This is what I was looking for. Do you have any more pics? How does the car drive on 345's? I think I am going to try a 345 toyo tq on my welds now...

Click to expand...

Drives no different than when I ran 315’s... car is half apart right now... hard to get any good pics..

Blackedout said:

Drives no different than when I ran 315’s... car is half apart right now... hard to get any good pics..

Click to expand...

What tire were you running exactly? Looks like a mt et street? I want to check section and tread widths of various brands since sizes can vary.

I use to have 335/30/18 Toyo r888 on 18X10.5 afs wheels. No rubbing issues in any way. Now I have 315/35/18 and it hits the fender. Had to roll them and they still hit occasionally lol.

TexaSTI said:

What tire were you running exactly? Looks like a mt et street? I want to check section and tread widths of various brands since sizes can vary.

Click to expand...

345/35/18 MT ET Street SS