Warning: 2wd racers

[McRat]

I'm not going to mention names, but we had another 2wd dragracer get into a serious accident at the dragstrip running steel radials up front, and bias-ply slicks in the rear. This was a VERY experienced dragracer on a very safe dragstrip, and he is fine, but the truck is pretty well destroyed.

Running bias-ply slicks, which have very little sidewall strength on the rear in combination with stiff steel radial tires up front, magnify steering input and can induce yaw oscillations, "wagging tail". Everything is fine as long as you do not have to steer the car/truck going down the strip, or nothing "upsets" the car into a direction change.

I have run cars both ways, and even ran Casper 1 this way, but it is just asking for trouble. We have seen dozens of crashes over the years caused by this, and I can tell you from first hand experience that you have far more control if you put tires with more sidewall give up front.

This is not the first time I've discussed this, so I perhaps sound like a broken record. But remember that it's not only your safety, but the safety of the other racer you need to look out for.

 

[othrgrl]

Any recommendation for tires that will hold up to the weight on the front of our trucks but yet still be skinny and have sidewall give.

 

[lotsofmiles]

thanks for posting this. you may have discussed it many times, but it was something i was just wondering about.

 

[mytmousemalibu]

X2

Thanks for bringing it up again, i forgot Glad the racer is ok!

 

[McRat]

Any recommendation for tires that will hold up to the weight on the front of our trucks but yet still be skinny and have sidewall give.

Worse ones are wide steel radials. Best are bias-ply racing tires but size issues make it difficult. Drag radials would be better than steel radials, like the M&H 275-55-16? which fit stock wheels.

If you must run steel radials up front, reduce pressure. 80psi is going to make things worse than 32psi. Running higher pressures in the rear can help, as can inner-tubes. 8 psi slicks with 305/40-20 steel radials up front is the worse possible scenario.

Get going on the street at 35mph and give the car/truck some steering input. If it "wags" you know that you might have an issue.

 

[SmokeShow]

timbeaux calls you friend??? :angel:


Looks like the word is being spread and received well be others. Probably better through him than yourself.


C-ya

 

[McRat]

Yeah, if they knew the advice was coming from me, they would probably dismiss it as the rantings of a lunatic.

Some seem to think it has to do with freeze plugs. Well, yeah, blowing coolant all down the track sucks for lots of reasons. However, I've hit oil and coolant running slicks and skinnies and haven't crashed yet, heck it wasn't even scary. I'm not so sure I'd be as fortunate if I had been driving something that handled like I was driving in reverse.

As long as there are no surprises, slicks and steel radials will work, but I'm not that trusting of the track condition.

 

[The Neens]

If you must run steel radials up front, reduce pressure. 80psi is going to make things worse than 32psi. Running higher pressures in the rear can help, as can inner-tubes.

The 1st time I had my 2WD '05 at Fontana, I took this advice...IIRC, 30 psi in my 285s up front, 18 psi in the M&H slicks...My truck only ran 99.8x, but went perfectly straight on a cold track...

 

[McRat]

From "another" board (see if anyone can guess who):

The biggest issue comes from people driving at speeds they are not use too. It's all fine and well when things go right but when they go wrong most people do not know what to do and event those who do cannot always correct for it fast enough. I'm all for safety in these trucks as we keep going faster and quicker but do not over look the problems by putting a tire on and thinking that's going to fix it! When you hit oil or blow a freeze plug and run through the antifreeze your pretty much along for the ride. Yes, you can make a few corrections from the steering wheel but you are pretty much along for the ride. Swapping types of tires up front isn't going to solve it, nor is running a tire not rated for the speed an load that's on it. Use a tire that is rated for the speed and load your running at first.

We all take our chances when you climb in to make a quick pass, just make sure the safety equipment is all up to speed before you do it as that's what's going to save you!

So I guess you're supposed to find out by crashing, because MOST people who drag race their trucks have driven over 100mph, yet the bias-ply accidents are most often occurring at lessor speeds.

Yeah, I'd have to agree that changing tires isn't going to mop up the oil on the track. I learned that in Janitor School. But I have hit oil/anti-freeze dragracing with proper tire combos and have recovered the car. It's not a guaranteed accident.

Speed ratings on the tires is an interesting subject. Many of us have taken the stock tires WAY past their printed speed rating, both in the 1/4 mile (briefly) and on the highway (sustained). Ditto for the load rating. While I do not suggest it, the evidence says that those ratings are very pessimistic for short bursts of speed. Even the SCTA acknowledges that, and allows you to run tires rated at 149mph up to 200mph and it appears to be working. I tested a 149mph rated tire up to 215mph at 2200lb load, and it failed. At 38 miles that is.

As you drive, heat builds up in the tire, then it stabilizes after several miles. This peak temperature is when the tire is weakest. We do not get tires up to their peak temperature in 5 miles, and certainly not in a 1/4mi. Ratings are done testing at full load and long duration, with some safety margin added in.

Has anyone actually blown a tire due to speed in diesel racing? Perhaps, but I've never heard of it, and have seen hundreds of trucks exceed their published speed rating before. Many of these tires are rated 99mph (Q), 106mph (R), and 112 mph (S), yet show no problems for short distances.

Now comes the next question. Which is more dangerous, hitting the wall, or losing a front tire? If you have had a front blowout on the street, you already know the answer to this one. The car/truck leans over, doesn't respond to steering input very well (understeers), and is generally stable. Rear blowouts are a different animal, and can cause gross oversteer.

Since the latest accident was a very experienced diesel racer, I don't think "not used to driving" argument really holds water.

 

[wikdlmm]

So are my 305/65/18 bfgbok up front with my 32/12/16 m&h out back?

 

[othrgrl]

So are my 305/65/18 bfgbok up front with my 32/12/16 m&h out back?

You would be much better off throwing stock wheels and tires on the front and not having them aired up too high. The bigger the rim the less sidewall (and sidewall give) you will have and the more it will cause the problems Pat is talking about. On top of that PYOs with smaller tires will weigh alot less and help your times.

 

[LarryJewell]

bump for safety sake

 

[wikdlmm]

Whore

 

[LarryJewell]

Whore

uhm no, trying to give a friendly reminder, this has actually got me thinking that I might want to sell my M & H slicks and get drag radials, what are your plans this year

 

[wikdlmm]

Its actually got me thinkn I'm puttn the m&h on our race truck!

 

[LarryJewell]

Its actually got me thinkn I'm puttn the m&h on our race truck!

you interested in buying mine for the fronts

 

[wikdlmm]

Its a 2wd Larry

 

[LarryJewell]

Its a 2wd Larry

well it would look really cool with all 4 :beavisnbutthead:

 

[68skylark455]

It would resemble a few local dodges:rofl:

 

[Subman]

It was my understanding the driver wasn't all that experienced and he wasn't the owner of the truck. I may be wrong but I didn't think the kid who was driving had that much experience drag racing. Sorry to see that truck go, one of the first in the 9's I believe.