Does anyone know the tallest slick tire I can put on my Z? Reason being, I got 4.10's with a Th350, so I was already just about topping out at the end of the 1/4, using borrowed slicks from a friend. Now I just put a 100 shot to it, so I'm thinking I'm def. gonna need to get some more gear out of her. I ran a 13.3 not tuned w/out the spray last summer. Yes, I know the gearing is prolly too tall, but I put the 4.10's in it back when the car was a manual with the original 5 speed and when that blew a muncie 4 speed. Any help on the tire size?

 

oh yeah, the tires will go on my old originals, the stock alum. 15x7's.

 

i would try some 28" tall slicks. really you need to figure out your trap speed and do the math for what size tire is needed. i've seen 29.5 slicks run with a lot of mods to the wheelhousing

 

What were you trapping at on the motor and what RPM where you going through at? I am assuming you were running short (26") tires. If he know where you were at, we can figure out what's possible by changing one of the variables.

 

I've had some 29.5x10.5's under mine at once. I had to do some trimming around the inside wheel wells and bang around some, but they fit. I'm back to 28x10.5's now with a 4.56 gear and a glide. But I can't make it down the 1/4 mile with that setup unless I want to turn it 7500. So you should be fine with a 4.10 and 28's with a th350

 

i was pulling 7k at 103

 

Factory tach? Even with 26" tires, that works out to 28% slippage. Something isn't right!

 

so with 28" tires underneath it I should be good on gear and RPM's if and when I break into mid-12's?

 

so with 28" tires underneath it I should be good on gear and RPM's if and when I break into mid-12's?

 

so with 28" tires underneath it I should be good on gear and RPM's if and when I break into mid-12's?

 

You should be good for an extra 7-8mph by changing to 28" tires. My point was though that you should not be having to rev your motor that high - either your torque converter is slipping an unbelievable amount or your tach is reading too high.

 

either your tach is wrong , or the converter is sliping! i run 4.11 gears and 28x12.5x15 et streets. i run 10.31 @ 132.87 and i am turning 6800 to 6900 rpm across the line.
something is not adding up!

 

I think that I'm just recalling wrong on the RPM's.

 

That's a pretty important piece of the puzzle! Its all about choosing gears that will put you at the optimum RPM. Find out where you cross the line (RPM wise), where your peak power is and we can help you pick a tire/gear combo.

As I said above though, you should be good for an extra 7-8mph (at a given RPM) by changing to 28" tires. Whether you need the tires or not is yet to be determined.

 

well, here's my 2 cents--- hard to get a slick on a 7" wide rim, try the M/T # 3054 (28 x 9 x 15) i don't know weight of car, under 3000lbs. try 12-15 lbs. each tire, over 3000lbs. try 16lbs. and up. but 16lbs. is were my car works the best at 3075lbs. w/ 850hp. plus not to do a glorous burn out for the crowd, just till you see some good smoke out from the tires. plus leave the 4.10's in. JR.

 

trans. could be slipping, if converter would be slipping the car would have a hard time, 60 ft times , the same. but 7000rpms is not bad for a well prepped motor. JR.

 

what size is converter, stall, which kind is it. what motor specs. can you give us. i had a stock 305, w/.480 lift, dual plane manifold, 1" spacer, th350,B&M strip trans.,w/10"- holeshot 3800 conv.,w/4.10's, went 12.86 motor, w/150 shot, went 11.89 and nitrous kick on at full throttle,spun for 80-100ft., then tryed 250 shot and broke both axles, at line never moved, the nitrous was run by the Jacobs box for nitrous,and was at 100% all the time,car weighed 3595lbs w/ me, plus through the traps -6700rpms.now its a 84' firebird stock susp. drag car. at 3075lbs. JR.

 

Back to original tire question, I've run the guantlet for different tires tallest thus far has been the M/T 29.5x9 which is still wider than my 28x11.5 hoosier DOT QTPro's. front inner wheel well beating is the norm for any bigger slick, but for these I also had to cut out hte rear diff bumper stop area since sidewall hit that area. but these were all mounted on a 10" rim, 8" rim would be better than the 7" since your going to be sucking the sidwalls in alot and distorting the foot print and/or having to really air down to get a better tread pattern.

FWIW, with my 28's I trap at 6600rpm and when I went o 29.5 it dumped me down to 59-6000 rpm. So if your adding N2O over tire your car to open up the rpm window otherwise your gonna be in a tight winding situation which is never good for longevity.

Anybody doing a john force on slicks is either un informed or showing off, the new compounds only need a whisper of smoke and theyr'e as good as they're gonna get-anymore and your wasteing tires/money.

 

thanks IHI, you're right, my original question was how tall of a tire I could fit. I'll go with 28's. I wanted to go tall as to help the gearing and make room for the spray. Also, the rubber wont be going on those 7" wheels anymore(I'm assuming that's what those ugly stock Z28 wheels are), I've found some old 8"s. That way I can keep my nice AR's on the street. Thanks for the info.

 

not to chagne the topis back but i have a th350 with 4.30 gears and running 11.8 and turning 7000 at the end of the track. this is with a brand new race prep trans, so is converter junk. i have a 28 inch tall tire also

 

Why do you think that the converter is junk, because your turning 7 grand at the end. i would say no. gears, tire diameters, play a roll in rpm at top end, theres performance calculators out there for everything, I've tryed different gear sets so that i can get through my gear changes the same till the end, like a 4.30 gear gets my 1st gear 7700,2nd-7500, 3rd-7700 < at the traps, that like perfect for my horsepower & torque band. JR.

 

well from what people are telling me i should change converter to a higher one ayway. i have a b&m hole shot in there now and from what summit says in the book its only rated up to around 500 hp and tq i am well over that. i want a higher stall speed anyway and i was going to start with that to see how the car reacted.

 

Well, if that doesn't work, try TCI-#254013, 8"-4400-4800, on my buddies car, the trans. brake flashes to 6,300rpms. works great in my buddies 383", car goes 10.20 @ 3325lbs. JR.

 

Just make sure you pick a convertor based on engine/cam specs rather than "hp" okay, you make 550hp...where in the power curve is that peak tq taking place to get max effort? and max performance from your convertor? If you get a loose goose 8" that flashes to 6K but your peak tq happens at 4K your losing a ton of "get up and go" due to convertor slippage and thus your not maximizing and will still be slow. You should be increidbly consistantly if bracket racing with a loose convertor....but slower.

But if you wanna you dead set on getting s higher stall without thinking, call up and tell them your looking for a 8" race convertor and you run a super charger. This should get you into a stator/fin angle that flashes the convertor high with your current set-up since it wont match, peg the tach at 6-6100 and stay there the entire time even after the shift...sounds stupid? so does buying a convertor based on "hp" Not meaning to flame you, just giving example of how important convertor choice is, as I've said before the convertor is #3 on my list of priorites for a great combination with the heads/cam being #1 and #2.