Drag Radial Slippage on Rim

[Taemian]

Dave and I took our MMs to the track last week for opening night of Street Legal season, and managed 2 runs each due to huge crowds. My best was 12.9 @ 109mph with my new widened rears and 285/55/18 street Toyos. Dave used his widened rims with the brand new Nitto 05 drag radials (295/40/18) and got a 12.2, then a 12.1 @118mph.

When we were checking tire pressures, Dave noticed that the tires has slipped on the rim. He had drawn a marker line across the tire/rim, and the tire slipped about 1/2 backwards in relation to the rim. He started about 30psi, then went down to 27 psi.

I'm thinking this can't be normal. Any suggestions??:confused:

I should mention that the rim is a stock MM rim widedned to 9.5".

[RoyLPita]

I have seen some drag tires get bolted to the rim to prevent this.

[Egon Spengler]

I have seen some drag tires get bolted to the rim to prevent this.
Bead Locks....

[FordNut]

Freshly mounted, they will do that sometimes. Especially if the tires were mounted using the soapy stuff to help the beads go over the rim. That stuff is slippery.

[Zack]

Who is gonna ask why anyone would run 30psi in a drag radial?

[RoyLPita]

I'm one who has never tried to run the 1/4 mile in anything that I own. I know nothing about tire pressures except what I put in mine.

[Paul T. Casey]

Who is gonna ask why anyone would run 30psi in a drag radial?

Hopefully no-one. The under-educated are better for some of us at the track.

[SC Cheesehead]

30 psi sounds high, but then that's based on racing "way back when" (pre-radial days). IIRC, the guys that ran bias ply slicks were 20lbs or less on tire pressures.

Does the same hold true for drag radials?

[RR|Suki]

Who is gonna ask why anyone would run 30psi in a drag radial?

I think we were all sitting back and waiting to see who would be that guy :D

[justbob]

15-18 on D/R's depending on the day/night and track prep. 25 ish on stockers seems to work out good for me.

[justbob]

Who is gonna ask why anyone would run 30psi in a drag radial?
HAHA your "that guy" LOL

[ctrlraven]

15-18 on D/R's depending on the day/night and track prep. 25 ish on stockers seems to work out good for me.
I run 18 psi on my 255/50-16 D/R's.

[merc]

Bead Locks....

Bead locks on radial tires..now that would be interesting. Real men run bias tires. That's what the worlds fastest Marauder runs.


Dave and I took our MMs to the track last week for opening night of Street Legal season, and managed 2 runs each due to huge crowds. My best was 12.9 @ 109mph with my new widened rears and 285/55/18 street Toyos. Dave used his widened rims with the brand new Nitto 05 drag radials (295/40/18) and got a 12.2, then a 12.1 @118mph.


12.1 @118 mph seems high for your E/T. What was the sixty foot time and the 330? Also what was the power adder?

[Rick-n-Miami]

I run the MT 305/45/18's at 17.5 PSI and they hook great! I do launch from idle, and do not brake torque the car. There may be some tire spin on the wheel, but doesn't seem to do anything if it's there.

[Zack]

118mph=11.30-11.40's if everything goes as planned.

[merc]

I run the MT 305/45/18's at 17.5 PSI and they hook great! I do launch from idle, and do not brake torque the car. There may be some tire spin on the wheel, but doesn't seem to do anything if it's there.

Track prep and weather conditions play a large role in performance.

[RR|Suki]

118mph=11.30-11.40's if everything goes as planned.

Which has me kinda sad, I'll be getting kicked off the track once I actually launch the car hard

[FordNut]

Which has me kinda sad, I'll be getting kicked off the track once I actually launch the car hard

Me too. :banned:

[sailsmen]

Question: Should I use rim screws with Mickey Thompson slicks?


Answer: Starting line launches can cause the rim to spin inside the tire. This can be hazardous and should be avoided. If you are not sure your rim is doing this, mark the tire and wheel with a line to gauge tire slippage on the wheel. Check for tire slippage when you check your tire pressure after each pass. If it moves ½ to 1, you should use rim screws. Do not use rim screws on radial tires, unless they move on the rim.

Post all the data in your time slip and we can analyze it for you.

[Taemian]

Who is gonna ask why anyone would run 30psi in a drag radial?

As usual, you never disappoint. Must be that the new-improved label has already worn off. Was nice while it lasted.

The March 2010 issue of MM&FF has a 4 page article on the brand new NT05R's, which is the tire we're talking about on Dave's car. They took a 550 rwhp Stang down the track with these tires starting at 15psi. They bumped it up to 20, then 25 psi and got their fastest time with the final pressure after testing runs. The article ended by saying that they believed better times could've been had with a bit more pressure in the tires.

Feel free to write in and call them whatever you like. Personally, I've found most of their tech articles to be right on the money.

[Taemian]

Question: Should I use rim screws with Mickey Thompson slicks?


Answer: Starting line launches can cause the rim to spin inside the tire. This can be hazardous and should be avoided. If you are not sure your rim is doing this, mark the tire and wheel with a line to gauge tire slippage on the wheel. Check for tire slippage when you check your tire pressure after each pass. If it moves ½ to 1, you should use rim screws. Do not use rim screws on radial tires, unless they move on the rim.

Post all the data in your time slip and we can analyze it for you.

The tires are Nittos's new DOT legal drag radials. Screws are a no-go. I'll go look for the time slips right now, but FYI Dave bought Al's (LilAlleyCat) car when his own Trilogy got smashed from behind and written off.

[Taemian]

Dave's timeslip

60'----2.048
330---5.363
1/8---7.990
mph---92.17
1000--10.250
1/4---12.153
mph--118.34

I know the gear timed right, we ran side by side for both runs. Guys from a local Mustang board have the vids as well. This was the opening night of the track for this year, so prep was a big ??? and we had the evening dew settling on the cars around 2000hr, so conditions were less than ideal.

[Taemian]

Maybe you can look at mine while you're at it. I added widened rears, a home-made ram air tube plus some weight reducing parts since last year's time, but it seems traction really sucked. Here's mine:

60'----3.42 WTF
330---6.932
1/8---9.789
mph---86.82
1000--11.29
1/4---12.975
mph---108.95

Last year, my best time was a 12.81@ 107.78 with a 1.9 60' time on stock rear rims and tires. Hopefully the track will be better soon, but for a 3.42 60', it seems a decent time.

Both my tires and Dave's had less than 50 miles on them when we got to the track, so maybe they'll bite better soon.:confused: And we only got in two runs since some import puked at the top end of the track.

[sailsmen]

I should have noted the Question and Answer I copied from MT Website.

These are from my car. The 12.2 & 12.3 and 12.8 when I had 450RWHP;
1.782 5.049 7.8 88.16 10.231 12.287 109.74 NitDR cold
1.745 5.096 7.883 87.13 10.329 12.391 109.4 NitDR cool
1.881 5.362 8.227 84.99 10.744 12.862 106.71 (stock tires), damp
1.879 5.321 8.2 10.740 12.881 105.46 NitDR, hot-hot-hot, 1/8 mph missing
1.754 5.12 7.923 86.51 10.392 12.48 107.93 NitDR cool

With 540RWHP, spinning out past the launch. Had to reduce tire psi to 14 to get to 11.55 @122;
1.912 5.239 7.96 89.58 10.331 12.307 117.17 MTET warm
1.842 5.025 7.673 93.57 9.899 11.793 120.43 MTET.cold

1.735 4.834 7.431 94.02 9.679 11.556 122.51 MTET,14psi cold


T you should have no problem getting to 12.4 in cool dry air, focus on traction.

Dave should have no problem getting to 11.5 in cool dry air, he needs to focus on traction.

Heat and humidity will add up to .75 to your best time. Altitude also is a factor, NHRA uses a conversion factor.

What's % is I swapped time slip data with an experienced drag racer whose car has the same equip as mine except an Eaton. You could not tell by looking at the data whose car was whose. Point is you can use the above data.

[sailsmen]

For street tires I would statr with 22psi, go around the water box, do a slight burn out and nail it.

For drag radials I turn the side mirrors down to see the fender wells. Go around the water box and back in, when the burn out signal is given pull out the water box, stand on the brake and nail the throttle 3/4 until smoke comes out each fender well. I would load up the suspension by holding the break and raising rpm to 1,800 then nail it.

Have someone in the stands stare at the rear tires and tell you if you are spinning out.

Most important when in doubt both feet up, the MM is very stable and will settle back down on her own very quickly for another run.

[Taemian]

For street tires I would statr with 22psi, go around the water box, do a slight burn out and nail it.

For drag radials I turn the side mirrors down to see the fender wells. Go around the water box and back in, when the burn out signal is given pull out the water box, stand on the brake and nail the throttle 3/4 until smoke comes out each fender well. I would load up the suspension by holding the break and raising rpm to 1,800 then nail it.

Have someone in the stands stare at the rear tires and tell you if you are spinning out.

Most important when in doubt both feet up, the MM is very stable and will settle back down on her own very quickly for another run.

Great info, thanks! We don't use the conversion stuff since we are less than 100 feet above sea level here at Mission Raceway. We're waiting for a good weather report, then hopefully we'll get some new data to post/examine

[Black_Out]

Take the rims back and have them just use bead sealer (black gooey stuff they use to prevent rim leaks). I would try that out before you go putting screws in them.

[Taemian]

Take the rims back and have them just use bead sealer (black gooey stuff they use to prevent rim leaks). I would try that out before you go putting screws in them.

Arrgh....we can't put screws in them, as mentioned above. Not sure if bead sealer would be strong enough to hold the tires in place, but it's something we can definitely try if the problem persists. There isn't any noticable air leakage since the pressures remained stable.

[Black_Out]

Yeah the bead sealer won't glue it in place, but it will at least create a surface with more friction than just the smooth lip of the rim.