Ok so I've been lookin at new rubber for my truck and found MT has discontinued the ones I'm currently running the 325/50. They do still offer the size but it's the ET Street 2. So I was thinking I might go with the 315/60 instead. The 325's list as 27.80in. diameter 13.20in. section width an 11.60in. tread width. The 315's list as 30in. Diameter 12.90in. Section width and 11.90in tread. So basically I'm adding about 2 inches of diameter. My issue is I'm still pulling hard in drive with my currant set up its spinning 54-5500 rpm at the stripe. It consists of a .030 360 with 11ish-1 comp carne 272/272 adv. dur. 216/216@50 and .454 lift. Edelebrock performer 318/360 with port match, home ported 1.88 intake valve smog port heads and a 650 spread bore double pumper Holley, 10 inch 3000 stall?? B&M with 4.10s. I have a new cam,heads,intake,and hp style 750 double pumper for it but with a new baby due in January I don't know if I'll have the time to do the upgrade. So will switching tire size hurt my ETs? Should I just try the new ET Street 2s?

I'm kind of surprised no one had any input on this. Maybe I should have posted it in the Q&A section.

I ran both the older 315x60x15 and the 295x65x15 M/T ET Street Radials on my old pump gas Duster, I never ran the 325x50x15 as I didn't want the motor to peak before the finish line in the 1/4 mile. I would put the taller tire on first and see what that does to the time slip and then add the other upgrades later

The new tire is better, give it a try.

I'm not familiar with street tires, but given the numbers you provided, you are giving up 1/4 inch tread, which is your traction, and 2 inches more diameter will mean your shifts will come on slightly later and your trap rpm will be lower.

From what I see, you are gaining a slight bit of tread but now a taller tire, which will also give you a bigger foot print. However, you will probably lower your trap rpms to about 5,000 to 5,100 (through math). You may have to up your gear to 4.30.

Hooking won't be an issue. The 315 should hook better, but you may end up regearing to get your trap rpm back up. Then again, some combos respond differently to gear changes.

I have 315/60 BFG DR's (original style) that I use on the street, and 325/50s that I run on the track. A long time ago a pass was made with the 315/60s and it wasn't too far off, but I don't recall exact numbers.

This is with a table top torque curve 493 and 3.55 gears, so the gearing is not "optimized" for the track even with the 28" tire. You may be more sensitive with a smallblock

Thanks for all the great info guys! This is what I was hoping to find out when I posted. I figured trap rpm would drop but wasn't sure how much. The tires only get used at the track and around home. I've got a pair of 31/10.5/15s I use for highway because of an incident I had at highway speed in the rain. I'm starting to think I might give the new ET Street 2 a try because of the rpm drop with the 315/60. Regearing would be nice but I do drive to the track, I'm already cranking 3500 rpm at 65mph and 4:30s would make it almost impossible to drive to the tracks further from home.

Thats why you need to build something that will utilize 3:55 gearing (hint: turbo)! I pull about 2600 rpms at 70 mph.

I think its gonna hurt your ET a fair bit... the
tall tires are changing the rear end ratio and in
going that its gonna take longer to get the rpm
to come up to the peak torque rpm.. being that SBs
dont make a ton of torque its gonna be lazy down
low due to the tire size, conv and the lack of torque..
years ago I did basically the same thing.. it REALLY hurt
my ET but my peak torque rpm was higher than yours... my
conv was given to me but it was useless for my set up...
I had more gear than you also... just took to long to get
the rpm up

I use the 315 as my street tire, I haven't tried them on the strip. they are the best I've tried on the street, but until they're heated up they spin. They'll spin at 70mph and then grab.Dave