Bret Kepner originally posted this on our local forum:
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Track temp is usually good down to 60 degrees at night for cars with slicks! For 90% of all street tires, things get pretty stupid below 70 degrees. That's why some people were spinning past 330 feet, where track prep very seldom matters except for cars which are already close to overpowering their tires in the first place.

I'd venture to say not many folks on this board run at any other track which hosts a "street tire only" program. One reason traction at other tracks' "test 'n tune" programs is much better in almost all conditions is because those tracks are simultaneously running high-powered cars with slicks which stay in the groove, keep the surface temp up, and keep it sticky.

VHT is a very tricky proposition on a street tire night and Ace & Chuck, (the starters), agreed it would only make things worse. The rosin is used to keep street tires from peeling the rubber off the starting line (called "bald spots") and is not really used to help traction.

I hate to say it, but the only "big tire" car which I saw have any problems off the starting line last night was Rob Nolan's turbo Regal and he was really spoolin' the blower trying to run quicker than 11.26...hence, overpowering the tires on a 69-degree surface.

When a car has a giant footprint, it'll hook. Case in point: the S-10 ran nonstop 9.70s and 9.80s including on the very last run down the track. The really funny example is NHRA Pro Stock racer Jason Line, who ran 6.72 at 204 mph (on a 6.68/207 National Record) only minutes before they opened the gates...and they hadn't prepped the track all day!

A few important points:

1. As I pointed out in the Results thread, the most common reason most folks blow the tires off at Gateway is they're nowhere NEAR the "groove". At almost ANY track, if you stage six inches out of the groove, you're gonna spin. Period. This might sound silly, but if you don't know where the groove is, walk up to the starting line and ask the starters. If you've got an armband, you can go up there and they'll tell you because they know (It's their job!). I'll help anybody who asks, as well.

2. In drag racing, traction comes in a relatively narrow temperature band. For cars with slicks, it's usually between a surface temp of 60 degrees (extreme lower limit) and 105 degrees. For street tires, it's between 75 degrees and 95 degrees (extreme upper limit). Above 95 degrees, street tires will spin on any track...unless changes are made.

3. An honest 75% of all multiple-purpose/application street tires work much, much worse when they're heated in a burnout. First of all, they're designed to rapidly dissipate heat rather than retain it, so the tires are usually almost air temp by the time the car is staged. (Don't believe it? Buy a $30 temp gun and you'll be amazed!) Likewise, the rubber compounds in most multi-purpose tires are A) a fairly hard compound which gets slimy rather than sticky when heated and use extremely stiff sidewalls. Low-profile tires work about as good as shopping cart wheels on a hard launch because they're designed to work in every scenario BUT that. Don't believe it? watch the start of a Formula 1 race; they're using the highest-tech multiple application tires in the world and they smoke 'em like a Top Fuel burnout when leaving the grid. When a tire is built for multiple compromises, it's just not gonna do some things perfectly.

4. Most tires can be made to work (well, sort of) with just one simple change: tire pressure. If the tire spins, drop the pressure until it doesn't...50% if you have to. If it keeps spinning, then there's obviously a problem. Most likely, it's a simple one...you're overpowering the tires.

Bottom line: If everybody's spinning, the track is junk. If even one car ISN'T spinning, there's a reason that car is hooking up.

 

very good post

 

good info

 

I didn't realize staying in the groove was so important! But equally as important is the suspension setup and the RPM you launch at! In my experience, the rear suspension should be as soft as possible still allowing the power to be transfered to the tires. And it's very important to find the right RPM that will be right between the car bogging and spinning through 1st.

Lupe, do you also just drop the clutch? I drop it at 6100 - 6500 rpm depending on the tempature. Maybe now with MT street ET's I may be able to raise that.

 

thanks for the post.

How much psi is too low though for a street tire. i am talking toyo proxes. Is it safe to lower them to 15psi?

 

I lower my tires to 11psi.....I have lowered as low as 8 psi but it was uncontrollable and I had to let off. Maybe others can give us their experience on what tire pressure they use.

 

what kind of tires? u are talking slicks or dr's right? u arent lowering regular street tires to that psi are u?

 

I started out using Nitto 555R drag radials.....I pulled a 1.76 with 12 psi but mad wheel hop

Then I switched to BFG drag radials and ran a 1.70 at 12 psi but very smooth launch

Later I bought some BFG G-force drag radials but this time got 295's which were so wide I had to roll the fender hard and I pulled a 1.63 at 12 psi

Now I have MT street ET's and run 11psi but only ran a 1.65 60 ft but I think I would be in the 1.5's if I hadn't changed my suspension....The worn out stock suspension seemed like it squatted more!

 

How does tire pressure affect traction? Proper inflation is one of the single most important factors in the performance of a drag slick (this includes slicks of the DOT-legal variety). Traction can be dialed-in by adjusting tire pressure up or down. In order to determine how much pressure your particular tires require you must find a clean piece of pavement, preferably off the highway. Next, make sure that both rear tires have identical air pressure. Then, do a short burnout and examine the marks. As the pictures indicate, an over-inflated tire will leave a mark that is dark in the center, but light on the edges. This is known as ’’crowning.’’ An under-inflated tire on the other hand will show dark edges and a light center indicating that the tire is cupping. This procedure can also be used on radial tires. The final picture of this series shows what the proper pressure looks like: an even contact patch the entire width of the slick.


That’s not all there is to it, though. Small incremental changes in tire pressure can have a meaningful affect on traction. Mickey Thompson Tires recommends adjusting your tire pressure up or down in half pound increments to precisely tune your slicks to the race track’s conditions. Tire pressure will affect your reaction time. Keep in mind that an underinflated tire reacts more slowly than one with more air pressure.


So, you keep reducing the pressure in your tires and your 60-foot time (also known as your short time) keeps dropping. All well and good, but you also begin noticing that the car is no longer stable on the other end of the track. Reducing air pressure in your slicks often improves traction, but often the tradeoff is reduced stabilty. They say you haven’t lived until you’ve done the ’’slick dance’’ through the lights at a buck-fifteen-plus. Remember, eight pounds of tire pressure is great at the starting line, but those same eight pounds are holding up the back end of the car while you are hurtling down the track. Be sensible with tire pressure. It’s better to give up a couple of hundredths of a second on your 60-foot time to avoid a catastrophe on the big end.


How do you get a handle on air pressure? Don’t expect to use an ordinary auto parts store tire gauge; you know, the type that fits in your pocket like a pen. The instrument used to measure tire pressure in a drag slick needs to be capable of reading accurately at low pressures. Any mail-order parts house offers a variety of good tire gauges for this purpose. Expect to pay between $20.00 and $250.00—it’s a worthwhile investment.

 

Very nice piece....I didn't know about doing a burnout and looking at your tread marks....but it makes since....may have to try it!

 

i like to drag race a few times a yr so it doesnt warrant buying an extra set of rims with dr;s on them or et streets. thus i am curious if anyone is able to cut a sub 2.0 sixty foot time on regular street tires? if so did u run very low tire pressure??

its fustrating trapping 118mph and not improving on your et that u have been running since u trapped 110mph and had 60 less rwhp. there comes a point of diminishing returns if u dont improve traction some how. sucks.

 

What do you call "Regular street tires" ?

 

ultra high performance tires. proxes, pilots, s03s, etc

 

It just depends on how soft the tires are. I can't see you cutting better than a high 1.9 sixty foot with a street tire.

 

I would call the Nitto 555R street tires....At full tire pressure I could only cut a 1.9 /2.0 60ft but once I did a burnout and lower tire pressure....they did pretty good (1.76)

 

If you're going to call the Nitto tire a "street tire" then that says that the new ET Street Radial is a "street tire" too. Afterall, they're both radial tires

People are going wheels up with the new ET Street Radials.

 

Are you kidding me....big difference with the two tires.....MT street ET's have no tread what so ever....the only reason they are DOT approved is the 2 little grooves in the middle....


The Nitto 555R's look like a real tire...plenty of tread

 

Re-read my post. I'm not talking about Et Street tires. I'm talking about the new Et Street Radials. People are putting them on the bumpers with these.

 

I guess I haven't heard of them then....So one is call MT Street ET's and one is called MT Street Radials?

 

Damn...those are pretty cool! I would have bought those instead so my car looks somewhat streetable and not get a ticket. Now if only they would make that tire in a 19" so I can cruise around and not get spanked off the line by build STI's and Evos!

 

dont the nitto dr feel like **** on the road though ?

 

Not at all, they don't have much of a sidewall. To me, they felt like my old Yokahama's AVS's.

 

LUPE ....in your avatar.....what does the Japanesse wrighting say?

 

**** if I know........I'm just a buck-toothed honky.

 

I think it says something about not touching your grape drink.