Dragmeisters Andrew, Calvin & Patrick...'splain tire choices, please.

Obviously drag performance vs. Autocross performance requires conflicting chassis/suspension setups.  I admire that patrick in perticular was able to run quickly in both disciplines.

My question really is more concerned with strip performance and tire selection.  Obviously drag slicks/radials are the necessary ticket, but I noticed all 3 of you are running RELATIVELY narrow drag tires, especially given power you are making.  So what gives? Can you have too much tire?

TIA for sharing your knowledge.

In reply to Ovid_and_Flem :I too must total ignorance of drag racing 101  

I know too wide a tire hurts you in autocross.  First you need to drive further with wide tires than narrow ones.  Second a wider tire adds drag and thus costs horsepower. Third wider adds aerodynamic drag. Forth  It's really hard to get the scuff radius in the workable range the wider you go.  

With a Formula 1 type budget you,  simply engineer and custom fabricate everything you need but what is the solution when your budgets are chump change?  

Ultra simplified.  A good drag slick has a sidewall that allows the tire to absorb the shock and wind up to sling shot the vehicle out of the hole.  There are different stiffnesses for higher HP level.  But, most common slicks are just 2 ply for the weekend warriors and Challenge car builders.  Drag Radials are stiffer and very dependent on the tread adhesion.  In both cases, too big a tire is more mass to accelerate and simply not necessary.  Too small and the tail dances.  Tire pressure, IC position, IC anti-squat, spring and damper rates are all critical to short time performance.

In reply to wheels777 :

Thx, Andrew.  So for a 2400 lb rwd challenge car with an honest 300 hp what would you pick?

Can I piggy back a question? Are tire screws or beadlocks necessary? Or maybe better wording: at what hp/weight do drag tires generally start slipping on rims?

I've been reading a lot about drag racing in the last few weeks and I hope to start getting some real experience next season.

Ovid_and_Flem said:

In reply to wheels777 :

Thx, Andrew.  So for a 2400 lb rwd challenge car with an honest 300 hp what would you pick?

What tire height (gearing) might be the more important question, or at least something that needs to be considered.

Mr Pierce, first off I apologize for not calling you.  We've been nonstop go go go since your text

last year i had "too much tire" because it's what i could get.  This year i felt properly sized to the car.  New slicks are 24.5x8x15 and i hooked just fine.  You don't need an 11" slick to hook 300hp in a light car.  I 1.7 60' on the 8" tire and hooked hard enough that i spun the wheel in the tire.  Which leads to screws.  I talked to Andrew about this at the challenge.  I'm going to screw mine in the spring, i just ran out of time/budget.  

Drag radials are more like a sticky street tire and are not going to wrap up(wrinkle) like a traditional slick so there is more chance to spin at the line.  

Bottom line on the datsun is about 300hp, 2450 without driver, 8" wide tire on 7" wheel, 50/50 weight bias with me in car.  3.54 gear.  

I've only ever run hoosier slicks in the past, this year i got m&h racemaster which are widely used by fwd cars because they come in short sizes, and i like them.  I was searching for 3 years for a challenge friendly set of 24" tall drag tires.  28's are everywhere.  Stampie has my hoosier quick time pro dot slicks from the last 2 challenges.  

Keep in mind if you end up with tires requiring tubes, because they aren't cheap.  

As far as performing both autocross and drags well, I'm flattered, but it's blind luck that my simple hypothesis to make it a top autocrosser worked 

In reply to Patrick :

No prob...I would have called but I knew you were tired and probably swamped catching up with work after long vacation.  I looked at Stampie slick but just seem too much for low power motor.  

I'm gonna drop down to 16" wheels as its smallest I can go with brakes on rear.  Try to maybe go down to even 245 50 16 to get smaller diameter and some sidewall flex to help launch.

Last year the 275 40 17 new ax tires just spun to mid track even with no power.

I wonder if even decent street radials might even be better than ax tires...especially since I'm not gonna be drag racing that much.  We do have an 1/8 strip here I can test on to Atleast compare 60 foot times on different tires.

Thank for input

That was an amazingly simply answer from a guy not known for simple answers ;) Although I can tell he wanted  to elaborate on the IC geometry ;)

...And my bet on Andy's tire answer is to get the best real drag slick you cna find/afford.

I learned from the fast guys at the challenge they weren't making insane power, they were just using all of what they had.

This is easier said than done if you don't follow other people's drag race experiences as part of build threads etc, but i find it's a good idea to look for the people who do the most with the least (as far as tires) so that you can cross out as many theoretical excuses as possible from your mind and focus on finding out how to make something work rather than throwing tire (/parts /money /etc) at it. For example, I've only ever drag raced my FWD cars on 23x7x15 slicks. These are smaller than many people run, but since i happen to know for a fact that not-very-light SRT4 neons have gone 10s and 1.6 60' on them, I don't have the option of shooting real progress in the foot by assuming that im slow because 'the slicks are too small' and failing to find the actual problem. That is a 7" wide slick hooking up 500+lb ft of  engine torque. Realistically this means a RWD car with weight transfer ONTO the slicks should be able to do even better.

Most low-power cars need  nothing in the suspension department (assuming it's not worn/broken) to maximize their 60' performance on slicks. It is mostly down to launch technique if you have a manual. Automatics are even easier as most low-power cars won't be able to spin properly heated slicks at all regardless of 'technique'. 

Slick diameter matters because you want to use your slicks to 'gear down' as much as possible without forcing extra shifts in the 1/4 mile. So if you are driving a 4spd auto with a 3rd gear that redlines at 120 and you are trapping 100, you can benefit by running slicks much shorter than the stock tire diameter. There are tire diameter and gear speed calculators online to help you figure this out. The caravan i ran at the challenge last year will top out 4th gear at ~104mph at current rev limit and tire size. It has trapped 97 so  the tire diameter is pretty optimized for its current power level. 

In other words, if you're running a stockish v8 engine with no power adders and an automatic, run the smallest slick that won't force you to upshift right before the finish line. If you have a stockish v8 engine with a manual, it is the same except you have to drive it right. If you think you are going to run quicker than 12s then you might need to actually spend time figuring out how little slick you can get away with, but anything slower than that and it is basically bolt something on and go.  Experimentation with tire pressure will be necessary. You want to run as MUCH tire pressure as you can without killing your 60', because slicks that are flatter than they need to be eat power/trap speed. 

Ovid_and_Flem said:

In reply to wheels777 :

Thx, Andrew.  So for a 2400 lb rwd challenge car with an honest 300 hp what would you pick?

26'x8.5" M/T ET Drag Slicks

Robbie said:

Can I piggy back a question? Are tire screws or beadlocks necessary? Or maybe better wording: at what hp/weight do drag tires generally start slipping on rims?

I've been reading a lot about drag racing in the last few weeks and I hope to start getting some real experience next season.

I run screws.  The tires turn on the wheel at low tire pressure and higher traction.

Bead locks have their place.  I don't make that much power.  DR guys are getting more runs out of their tires with bead locks.  Again, I don't make that much power.

evildky said:

That was an amazingly simply answer from a guy not known for simple answers ;) Although I can tell he wanted  to elaborate on the IC geometry ;)

 

...And my bet on Andy's tire answer is to get the best real drag slick you cna find/afford.

 

I learned from the fast guys at the challenge they weren't making insane power, they were just using all of what they had.

Simple question = simple answer.  He didn't ask about IC.

Best tire is always the answer.

"Use all that you have" = win

Robbie said:

Ovid_and_Flem said:

In reply to wheels777 :

Thx, Andrew.  So for a 2400 lb rwd challenge car with an honest 300 hp what would you pick?

What tire height (gearing) might be the more important question, or at least something that needs to be considered.

True.  Our testing regiment includes determining what the torque converter slip percentage is, then gear to match tire height and have it touch the rev limiter in the traps.  It is common the swap gears 2-3 times.  When class racing the mid-summer gear is typically numerically higher than the spring/fall gear.

The air in Gainesville is usually poor (low barometer/high temp).  I typically rev it 3-500 rpms more in Gainesville, than up here where air density is higher.  

Our land speed car has 2.86, 2.91, 3.00, 3.15 and 3.25 depending on conditions and track length.  Also, we run triple disc clutches that don't slip.

The drag cars use 3.5, 3.64, 3.70, 3.89, 4.11, 4.30, 4.33, 4.57, 4.86 and 5.14 depending on engine rpm, converter slip and tire height. 

Vigo said:

Most low-power cars need  nothing in the suspension department (assuming it's not worn/broken) to maximize their 60' performance on slicks. It is mostly down to launch technique if you have a manual. Automatics are even easier as most low-power cars won't be able to spin properly heated slicks at all regardless of 'technique'. 

Please read this qualifying comment - I have been told that I have unintentionally touched nerves with many of my posted replies.  So, I am qualifying everything with this statement - I am not suggesting you are wrong, did not experience what you witnessed and I am not personally attacking you.  I can only speak about my own experience. 

I have personally improved 1/4 mile ETs by solely focusing in short times through suspension work.  Some projects with low HP engines have seen nearly 2 seconds improvement in 1/4 time without any engine changes, and that did not include the improvements from adding drag slicks. 

Again, I am frequently informed that I post things that are interpreted as hurtful and/or offensive.  I have reread this post and am prepared to hear that it is off base.  I tried to write it and with and without tone, inference and malice.  I think I did okay, but I am reading this with my own interpretation on intent.  If anything stated here or above is out of line, please PM me and I will delete my comments. 

I dont have the expertise of some of these guys but drag racing is the only motorsport i participate in. I was originally a fan of as much tire as possible but in my own experience i gained 3/10s going from a 28×10.5 to a 26x8.5 on a 2600 pound car with a 2200rpm stall, 4.10 rear gear and a 300 flywheel horsepower crate motor.  

In reply to wheels777 :

I think I have internet forum stalked you by reading all your posts on this forum.

Not once did I think you came across as anything but helpful.

Please do carry on.

wvumtnbkr said:

In reply to wheels777 :

I think I have internet forum stalked you by reading all your posts on this forum.

 

Not once did I think you came across as anything but helpful.

 

Please do carry on.

I have deleted almost half of my posts and go without posting for extended periods.  I actually like some of the folks who I offended.

wheels777 said:

wvumtnbkr said:

In reply to wheels777 :

I think I have internet forum stalked you by reading all your posts on this forum.

 

Not once did I think you came across as anything but helpful.

 

Please do carry on.

I have deleted almost half of my posts and go without posting for extended periods.  I actually like some of the folks who I offended.

Don't feel bad i re-wrote a post about 10 times and still think i'm going to come off as an a-hole to the people it's directed at.  Not the intent, but don't care at this point what the intended audience thinks about me.

I will continue to look for some 16" drag tires for the c4 since I'm located within 90 minutes of 4 dragstrips.  There are always slicks and drag radials on CL, it's just a matter of finding the guy who doesn't want 75% of new cost for used tires.  

wvumtnbkr said:

In reply to wheels777 :

I think I have internet forum stalked you by reading all your posts on this forum.

 

Not once did I think you came across as anything but helpful.

 

Please do carry on.

+1

wheels777 said:

Vigo said:

Most low-power cars need  nothing in the suspension department (assuming it's not worn/broken) to maximize their 60' performance on slicks. It is mostly down to launch technique if you have a manual. Automatics are even easier as most low-power cars won't be able to spin properly heated slicks at all regardless of 'technique'. 

Please read this qualifying comment - I have been told that I have unintentionally touched nerves with many of my posted replies.  So, I am qualifying everything with this statement - I am not suggesting you are wrong, did not experience what you witnessed and I am not personally attacking you.  I can only speak about my own experience. 

I have personally improved 1/4 mile ETs by solely focusing in short times through suspension work.  Some projects with low HP engines have seen nearly 2 seconds improvement in 1/4 time without any engine changes, and that did not include the improvements from adding drag slicks. 

Again, I am frequently informed that I post things that are interpreted as hurtful and/or offensive.  I have reread this post and am prepared to hear that it is off base.  I tried to write it and with and without tone, inference and malice.  I think I did okay, but I am reading this with my own interpretation on intent.  If anything stated here or above is out of line, please PM me and I will delete my comments. 

 

 

I'm not taking any offense to that at all. I think we are talking about slightly different things. I said maximize 60' performance (solely speaking of 60'). My understanding is that if you are not slipping the tire at any point in the 60', any suspension articulation is just storing energy in the suspension that you may have been able to put to the ground as acceleration instead. So, if one is dead-hooking every pass and trying to optimize for the power you have, i would do nothing to the suspension (unless you are having issues going straight) and instead add air to the slicks until you started to run into tire slip. Somewhere around there is going to be the best balance between getting the launch right and losing the least power to rolling resistance of underinflated slicks. This is slow-car theory and wouldn't apply to cars that can spin slicks easily. Feel free to contradict me as i have nowhere near your drag racing experience and am open to learning.

This is all fine and dandy, but where does one find low buck slicks when there isn't much left in the budget?

I know "plan ahead" "set aside money early." But where do you look when you've already blown most of the budget.

In reply to bigben :

Ummmm, like the drag strip? Same way how people get all these “free” autocross tires, goto the track.... I can find a pair of 26x10x15 slicks everyday there for $150, especially when a series comes through like nmra/nmca.

Personally, given the current rules, unless I can magically find a set of those “free to everyone” autocross tires around these parts, I’ll run fresh drag tires every time. I personally will always run radials since that’s what I have always raced on.

With drag racing, there is always more than one way to get down track the fastest.

Also when Searching for Freebies find a Sponsored Team car as they don't have Pocket Money Invested and would be more Sympathetic to the Cause .

This thread is excellent. Thank you all!