I'm doing a swap this winter from 3.73 gears to 4.56 gears. What tire is best to use with this gearchange. I used M&H Radial slicks 275/50/15 this year but the compound of these were way to hard, and the tire cooled down really quickly after the burnout. And causing a lot of traction problems. Best ET without stalling the engine right now is 11.13@117MPH couldn't stall the engine with these tires they would just go up in smoke. The engine rpm was 1500-1800rpm leaving the line. I have had ET's from 12.00 to 11.13 ET times due to traction problems. I'm swapping my POSI Unit for a Strange Spool, the POSI unit diff.plates gave up after 18 runs. I have koni SP1A shocks, set 50/50 in the rear and 70/30 in front, HR Swaybar, TA No hopbars. Etc. Greetz Robert
Have you tried Mickey Thompsons? http://www.summitracing.com/search/...Thompson-ET-Street-Radial-Tires/?autoview=SKU
Robert, you are going to need a tall tire to use those gears for the quarter mile. We use the MT drag slick and have the 10.5 x 29 with a 4.10 gear. Finish the quarter now at 119mph at about 5500rpm. These tires still have some traction issues, but all we currently have is adjustable uppers. We will add Spohn's rear drag race bar this winter.
Go with a 4.10. You will HATE the 4.56's. By an Eaton posi with the 800 FT/LB spring upgrade. I wore out 2 Auburns before I bought the Eaton. It's been great for 7 years now. Tom
Depending on your converter slip you might not be able to run a tire tall enough to work with those gears.Are you running the stock wheel tubs? Jamie.
I forgot to add. There are drag race calculators that will help you with tire height. We looked at our estimated mph in the 1/4, then desired rpm, tire height, and it would give us gear info. You can play with tire height. http://golenengineservice.com/calc/calcrgr.htm Looks like you will need a 31" tall tire to be running 120 in a 1/4 mile at 6000rpm.
Ok seems that those 4.56 gears are not good for my car. Yes, I got the wheel wells, fenderlip with trim all is still in place. Biggest tire I ever used was a Mickey Thompson Full Drag slick without tubes, and that was a 28.10.5x15 tire that fitted nicely and would only rub if I would take a sharp turn. I got some M&H Cheater Dragslicks that are the same size from a friend who isn't using these anymore. They are good for at least 20 passes still got some "tread" on them. So we will see how these work. I have a new Strange spool with new 3.73 gears. But JW suggested to go to 4.56 gears. So what is the deal guys? I have had traction problems due to bad tire compound choice. This was a 275/50/15 Radial dragslick from M&H. I was leaving the startline with only 1700-1800rpm max and best ET was 11.13@117MPH so I couldn't use the full potential of the 9.5 4500 stall convertor, who works really well its like you have only 1 gear and you don't even feel the trans shift (if you have no grip problems). I will post a video of 1 run, and you can see the RPM needle stick at 6100RPM and just when I get at or go over the finishline it start to climb to 6200-6400. I got a 6400RPM revlimit chip in there for now. So with that low tire I guess I'm close to 4.10 gears allready. But a bigger tire is a better footprint. So guys what are your opnions, trow in the 3.73 gear with spool that I have now or swap the 3.73 to 4.10 gears and see what happens? A fellow race friend told me that a transbrake could cure my traction problems also cause it would hook harder with a transbrake. Did I tell you that, my POSI unit went crazy in the last two runs I made. Last run the 60 foot was really off and one wheel did go up in smoke shifting from 1 to 2 gear and ET was a 14.xx ET! So its time for a POSI unit change, I have the spool so. I believe if the traction problems and inconsistent times were due to the tires and or POSI unit acting up. That I could have go in the 10s if have had the time to put in the Spool before we left to the track.
Does your engine make power that high up in rpm. The 117 mph your running, I would say it is not. Posi units and drag slicks do not mix as you found out. Do you have an anti roll bar on the rear? Do you have a front sway bar? How much front end travel do you have? Get your car to "work" with bias tires before you play with radial. Do they prep the track well? Radials are very unforgiving.
My peak HP power is at 6100RPM, peak torque is at 4900RPM. fastest run was a 195KPH thats a 122MPH I believe. I have a HR swaybar in the rear, I have the stock front swaybar. Front end travel: the front tires almost completely unload, almost come loose from the ground. Prep track was not really good, have seen it much better. On friday for sure the first runs in the morning everyone a lot of people were having traction problems, even with tubbed cars. They didn't have a problem later that day when the sun heated the track up.
You really should remove the front sway bar, that will help alot with your traction issues. Is this pretty much a drag car only?
Here's Robert's motor.. He has barely scratched the surface of the cars performance potential. He really needs a sealed hood scoop.. Your not going to hook that kind of power, with a tire with a 26" sidewall. You need a full on drag slick for the strip duties, have another set around for street cruising. I would run this tire.. as long as you have the right offset on the rear wheels.. need about 5.5".. you can judge if it will fit, by comparing your current tires to this tire, and then looking at how much room you have in the wheelhouses. http://www.summitracing.com/parts/HOO-18180D06/ If you ran on better tracks, I would suggest a stiff sidewall version of this tire, as your car is pretty heavy, but I think you going to need all the traction help you can get. When you get it all worked out, you should shift that motor at 6300 and trap it about 65-6600.. It's got a filled block with a girdle and good rods, it will do that for a long time.. That block made 800 Hp and went thru the traps at 6800, reliably in it's previous life.. With the right conditions, and the combo dialed in, he will run in the mid 10's at 123-125 mph.. You will get there, but the 4.56 gears and a tire with enough sidewall, will be a good start.. and that thing is just dying for a forward facing, sealed up hood scoop. Right now, traction is key, you need get that motor in it's working range quickly, and putting that pwr to the ground. I would also say it may be time to take the No-hop bars out, they start to work against you after you get it going into the 1.6 or faster 60" times.. We stopped using them at about 11.50 in our 4100 lbs GS, as it was doing a 3 wheel wheelie.. As Jeff said, at least loosen up the front swaybar at the track.. take the links to the lower control arms out.. also, lightweight front wheels and tires will help transfer weight. Once you get the car to start to hook, then watch your video, to analyze the front/rear suspension actions, and the wheelspin.. take a series of tighter shots on the car, on the front, and on the rear, to look at what is going on with the suspension, and traction. Right now, the gear is making the converter flash too hard, the 4.56 will get that converter to lock up better, down the track. JW
JW, still learning here, tnx for the info. This engine/trans combo is a different beast then my old setup. I got a set of these tires for free to try out: http://www.summitracing.com/parts/MNH-MSS001/ I have two sets of lightweight rearwheels one with a good offset of 4.5 and its a 8.5 rim says the previous owner, but I think its a 8 WELD rim. Never seen an 8.5, but will measure that up to be sure. I will call a friend who has some WELD rims for sale they came of his GTO, I believe they are 5.5 backspacing and 10". If it has 4.5 backspacing will the 10" be a better choice then the 8" I know have. With the 8" rim the tire can get a little bulgy. I will measure up the clearance I have now with M&H radialslick I got on these rims now. I made the last couple of passes with my WELD front rims, but the POSI was going bad allready so didn't notice a improvement. Yes its a dragcar only right now, so I can loosen up the swaybar to allow for more travel. I found an hoodscoop locally at my friends shop he didn't knew he had it. Its a scoop that is close in front and its open in the rear it a small scoop. Looks like a early 70s transam scoop. I haven't bought it yet, will this do the job? Or is a cowl hood or cowlscoop or even an Stage2 scoop better. Ok replace the No Hop Bars, with non or adjustable ones. I haven't made alot of runs with the car 20 runs tops, but we have seen there is much more in there. I tried to manually shift two times, but couldn't keep up with the speed the engine goes true its rpm range. Its really fast! Now I have read your comments, it could be due to the 6400 rpm revlimiter chip. The moment I shifted I was just to late and it went in the limiter. The ET's (Best ET11.13) we got with that 26"tire and 3.73 gears told me also that there is more in it. Cause with the slow start, the engine was still able to get the car easily in the low 11s. Can't wait to make some more testruns at the track, but we have to wait untill june to test it at a good track. I will post some vids on the web this week, so you or the other racers can see how it acts at the start and can chime in if they see more things for improvement. Greetz Robert
