Tubes on M/T ET drag slicks?....

[cjshaker]

I want to try my hand at running my car on the strip at this years FE Race & Reunion, so I'm considering buying some CalTracs and M/T ET Drag Slicks. Summits web sight shows the Mickey Thompson ET drag slick as requiring a tube. But the M/T websight doesn't say anything about it. Just wondering what you guys do on yours? The tires will only be used occasionally so I'm not worried about losing pressure over a few days or weeks of sitting, but I don't want to compromise anything for safety either.

[jayb]

You might lose air faster than over days or weeks.  I ran a set of Hoosiers tubeless at DW07, and they would lose a couple pounds per hour.  I was having the trunk monkey air up the tires right before I headed for the starting line.  One time an oil down delayed the line, and I'll bet by the time I got the green light I went down the track on 10 psi 

On the other hand, they might seal up fine, but I think I'd recommend the tubes.

[cjshaker]

Thanks, Jay. Didn't think they would be that bad. Did you ever have problems with the tire turning on the rim?

[thatdarncat]

I've always used racing tubes in the Goodyear and Hoosier slicks I use on my primary race car. I've mounted some of the Goodyears at times tubeless to trial fit for clearance and, as Jay noted, they leaked out rapidly. They generally leak right through the thin sidewall of the tire. We did mount up a set of used Hoosiers tubeless for one of my street cars a couple summers ago and they've held air very well, months with little change. My tire guy Bradford did use a special bead sealant on the rim. I guess my advice would be to try them tubeless if you want but do it well in advance of the event and first do the soapy water test on the outside sidewall of the tire when done and see if you have bubbles. After that monitor the pressure over the next few days and see what happens. If you do them tubeless NHRA likes to see screw in valvestems. If you run tubes you generally want to use bead screws to keep the tire from turning on the rim. We also use baby powder liberally sprinkled in the tire with tubes. The tubes will give the tire some more stability, but plenty of guys run without them. The tire pressure you use will probably have a bigger effect. I've done some testing and as little as half a pound less air pressure can go from stable to get your attention.

[cjshaker]

I've done some testing and as little as half a pound less air pressure can go from stable to get your attention.

Thanks. I was trying to stay away from screws because I will be using a new set of aluminum rims, but if it's necessary then I will. There's a local 1/4 mile track (with a not-so-great starting line for traction) that I can experiment on and see if the tire turns, but with the limited traction the track offers it may not be an ideal test. The guy who does all my tire work is very very good and I'll speak to him about any bead sealer or whether it would make the tire more prone to turning on the rim.

Would you have a recommendation on where to start safely for pressure? The car will have about 550hp with this engine and is not stripped at all. Full interior, all iron 427 except for the intake. I plan on CalTracs but may not go the mono-leaf spring route. I don't want to lose streetability.

[XR7]

I haven't used tubes in drag slicks for probably 8+ years, several sets of slicks, maybe close to 1000 passes. No wheel screws either, bolt in valve stems... yes, 1.34 60 ft @ 3600 pounds on a 10.5W stiff sidewall tire. Nobody around here runs tubes, well maybe 90% or so don't. They are heavy (some sizes add 50# or more), expensive, you will have to drill and screw your wheels, and will slow your car down a tenth. Some slicks hold air better than others, but I soap them up and air them up when new, do a good first burnout for good heat, then normal from then on out.

The only time I need to add air is when we wait a long time between rounds, and it cools off into the evening, or the tire in the shade, maybe a 1/4 or a 1/2 pound, otherwise, usually I release air, before I go to the staging lanes. I always jack up the rear about an inch off the ground for the entire week or two or or however long after/between races. If you let them sit a couple weeks or a month, sometimes depending on the tire, some will go flat, other won't. Luck of the draw maybe...

The only time a tube will help (other than hold air... but maybe not balance...), is when a soft sidewall tire is used, or the sidewall has been repeatedly crushed (low air and/or too soft/fast on shock extension) and is "gone", and the suspension needs it stiffened up to work correctly, the tube will do that somewhat.

That is my experience, others will dis-agree.

[cjshaker]

I realize I'll probably have to experiment to find out for sure what will work best for me. I'd prefer no screws so I'll try tubeless to start. I'll probably use my '70 F350 dumptruck to haul it, so I'll be able to take a generator and small compressor if need be.

I would naturally assume it's always good to take the weight off the tires when the car sits for any length of time. But they will probably be removed right after any track use and put my street tires and rims back on. I'm still up in the air about the mono-leafs for regular street use. I have an extra main leaf added to my stock rate leafs and use a 1" lowering block to get the rear back down where I want it, so I'm not sure how that will affect things either. My only goal is to get the best traction with what I have....but before that is to just stay on the track I am also considering changing my front springs back to stock big block springs because the ones I have are the higher rate, 1" shorter springs and they may cause an issue if the front raises too much.

I still wonder what would be a good starting point on pressure, or just go with what M/T or M&H recommends?

By the way. I really appreciate your guys' input and helpfulness. I've done plenty (more than I care to admit) of street racing, but this is my first attempt at a real track. Makes me a little nervous I guess.

[thatdarncat]

Different tires and brands like different pressure. And there can be different compounds available for a given size. And of course track. You'll have to test. I don't have any personal experience with M/T. With a Mustang and a bias ply slick I would probably start at 15 psi and work my way down if needed. Use the highest psi they hook with would be my recommendation. My current Hoosiers seem to work well at 12 psi. The Goodyears needed about 10-11 psi. Any less and it could be a handful at the top end. My Mustang weighs 3400# with me in it and runs 11.50's. I wouldn't worry about the mono-leafs, they seem plenty streetable. Jay runs his on the street.

[cammerfe]

Back in '63-'64 I used a set of M&H slicks---first on my blown 312 '54 and then on my '64 427 car. I mounted the M&Hs tubeless to start with, but found that they lost air so rapidly that it simply didn't make any sense.

I put tubes in and everything was fine. I played with air pressure but found that between 10 and 15 pounds was best.

But that's long ago!

KS

[fastback 427]

Hey cj shaker, I ran my Mickey slicks with no tubes. They leaked down slowly over four or five days. As for the tire slipping we use Hi-tack gasket sealer on the beads! 5000 rpm hole shot and no slip. Slow going taking them off though. The cal- tracs on my 67 are great, worth their weight in gold. I have the whole system front to back. Had a little trouble dialing it in at the track and they helped me over the phone on a Saturday. It rides nice on the street as well, little firm.

[manofmerc]

CJ on my 67 comet dragcar with 9.00-28 mickey thompson slicks I use tubes .I dont have leakage problems and I also put screws in my rims .Supposedly the screws serve two purposes .One to prevent the tire from turning on the rim .And two to pull the tire up tight on the rim .Wheater or not this actually does any of this is up for debate .But that is what I have done for the past 10-15 years .On air pressure a difference in one to one half pound is a lot with slicks .on my setup I run thirteen psi over fourteen it will spin a bit .Go on and get the cavert racing mono leaf springs I dont see any disadvantages for the street .Actually with the caltrac bars they advise using their springs to prevent bending stock leaf springs .I personally havent seen this just internet talk .Another thing about the monoleaf springs .You can easily change ride height by swapping the rear spring segment .You can have stock height +one inch or - one inch by simply changing the rear spring segment .Cost is about $200 for both .I just did this with my comet .Good luck to you Doug

[jayb]

When I ran my Hoosiers tubeless I don't recall seeing any slip on the wheel, just that annoying loss of air pressure that I mentioned previously.  I ran Mickeys on my Mach 1 back in 2005 at Drag Week, with tubes, and the car hooked really well with Cal-Tracs, mono-leafs (which I have had no trouble with on the street), and the Rancho shocks that Calvert recommends.  13 psi seemed to be the best tire pressure for both the Mickey Thompson tires and the Hoosiers.  The Mickeys were 9" wide, 27" tall tires on 8.5" wide rims and they really worked well at the track; if that is the tire you are looking at for your Mach 1, Doug, I think it will work well for you.

I would also encourage you to experiment with going tubeless.  XR7 pointed out some of the advantages, but the one that really hangs with me is weight; those tubes are really heavy.  Avoiding the rim screws is also attractive.  I would much rather run tubeless, but so far I just haven't found the right combination to do so.  Just make sure you put steel valve stems in the rims to comply with the NHRA requirements, and give it a shot; you can always put tubes in later if it doesn't work out to your satisfaction.

[cjshaker]

I have decided to just go with the entire CalTrac set-up. I know I can release some pre-load on the bars for regular street use if need be. Besides, the ride is already on the stiff side with the extra leaf and 750 front springs. In for a penny, in for a pound as they say

Thanks again for the advice and real world experience, guys. It's much appreciated.

[turbohunter]

Curious about the lowering block Doug.
Is that something you would take out in your track set up?
I remember the raising block in my F100 increased rotational leverage and really twisted up the springs.
When I installed my new set of springs, sans the block, the difference was amazing.
But that was a lifting block. Would a lowering block still apply more twisting leverage and would that be something to take out?
Just thinking out loud.
Have fun.

[Heo]

Yes everything that move the axle
from the centre of the spring up or
down increase spring twist.
A guy i know bought some "shelby"
springs that raised the rear 8 inch
he put 8 inch lowering block in to lower
the rear the nuts
on the ubolts almost touched the road.
Talk about Wheel hop
It  riped the glovbox door open