Dr tire size

[socalrdnck]

Ok before anyone starts talking shit I've done searches and either I'm searching wrong key words or something isn't right cause I can't find shit!

My question is with an IRS can I put either a 325/40-17 or a 325/45-17 on my cobra without any rubbing issues. If I have to roll the fenders a little that's fine but I'm worried about inside clearance. I currently have 315/35-17 drag radials now with no clearance problems but still have a big problem with traction so I want to go to a larger sidewall.

Has anyone ran those tire sizes without any issues?

 

[tt335ci03cobra]

I recommend using low profile IRS bolts. They are roughly $10-25 for both (and much less if you find their equivalent at a hardware store). I have to run them to clear my toyo tq's which are 315/35/18's. The largest I've seen someone run on a low profile bolted irs cobra was a 335/35/18 on custom offset rims. You won't cleanly fit a Mickey or Hoosier 315 on the factory 17x9's, but the 10.5 replica's should. I have no experience with replica's though, and assume the backs pacing would limit the sizing to about a 315 at most.

The tire anyone buys will vary in width regardless of the written size on the sidewall. It's also more important to have a truly flat and square footprint with squared sidewalls than absolute contact patch. A tire works as a system, so if you squeeze a 325 onto a 9" rim, the sidewall is at a terrible angle to absorb, and the contact patch is literally stretching and warping. It would hook possibly worse than a properly sized, say 275, on that 9" rim.

My current Toyo tq's are about 1" wider than my old Nitto nt05r's, and those where roughly 3/4" wider than my nt555r's were.

I ran 275/40/17 bfg gforce ta dr's that were wider than my nt555r's or so I recall, maybe they were barely smaller.

A huge help for traction is to get the rear suspension sorted with an ftbr kit if you are irs, or proper pinion angle, struts, sway bar and lower control arms of solid axle.

Driver mod is crucial as well. After about 500whp, launching, even on drag radials, is a balancing act of smooth, quick engagements and imputs.

Good luck. Many agree that Mickey Thompson makes the stickiest, albeit shorter lasting drag radial.

 

[socalrdnck]

I'm currently running 10.5 on rear right now not 9"

 

[socalrdnck]

Thank you for explaining things! I appreciate it.

 

[socalrdnck]

sorry I didn't specify on my traction problems. I'm not launching my car from a dig. I'm set up for 40+ pulls. 2 gear at 40mph and I break loose. Even dropping pressure in tires and heating them up first. Are you having good luck with the toyos? I've been told to look into those but was also looking into the m&h dr's in 325/45-17 but would like to know if those will rub my irs. I already have the low profile bolts installed.

Thank you

 

[tt335ci03cobra]

Toyos have been good. What power/torque are you making? What suspension are you running? What wheel do you have? What exact tire do you have? There is a huge difference between something like a nt555r and a MT et street or Hoosiers, etc. I'd bet money on a 245 MT over 315 nt555r's in a 60ft contest.

-17x10.5 replica's usually have 5.8-6.4" of back spacing iirc, which allows for about a 315-325 tire to fit in the stock wheel well with shaved or low profile bolts.

A 325/45/17 will be very tall, at about 28.5" tall. On anything but stock suspension, it will scuff/rub badly on dips and bumps.

I think a 325/35/17 on an 11" rim with an ftbr bushing kit, 3.73's, and supporting mods would really get the bite/hook you want.

I had 620whp on a nitrous/eaton combo that hooked terrible if I just went wot, but did very good if I quickly rolled into power from 50 rolls. This was in 2006 with 315 nt555r's on 9" wide rims with poly bushings, and 4.10's.

Knowing what I know now, I'd have been running 3.73's, delrin, 11" wide rear rims, and 335/35/17 Hoosiers or MT's.

I've ran a 28" tall tire, I think the happy medium is a 26-26.5" tall tire. You get very odd handling changes from a 28" tire on these cars, the suspension geometry really works best with a 25.6" tire, but a 26.5" isn't too bad.

 

[socalrdnck]

Im sitting at 550 wheel and will be on a whipper with spray as well very soon so at that point I'll be over 700, h&r springs and full tilt bushings. Wheels are the afs replicas.
Will be gearing here soon as well.

Trying to get the traction dialed in before I start building big number cause I know it's only gonna get worst.

Im not new to racing and tire combos however I'm still new to this platform. I've built and raced fox body's for many years with and sra and tubed rear.

Trying to gain some knowledge in this and learn what wheel/ tire combos work for our cars.

Mine will not be set up for the strip. It's being built for high speed runs. 2nd gear 40+ pulls and 3rd gear 50+ pulls


Thank you again for the insight. I appreciate the help.

 

[tt335ci03cobra]

Ok that'll be awesome man, I'd definitely go no taller than a 26.5" tire, I fit 28" tires on mm coil overs but it rubbed on larger expansion gaps, dips, etc.

335/35/17's Hoosiers or 325/35/17 MT's are a great tire for hooking.

700whp would be about perfect with 3.73's or even 3.55's on an sc setup with 6500-7000rpm shift point.

on replicas I've seen 325's fit well

 

[socalrdnck]

I will be purchasing the 325/35-17 tires. Thank you!

 

[safado]

you install the 325's yet?