so talking with a good family friend that been a nation wide drag racer with his 68 camaro going 6's in the 1/8. was telling me why not run a drag radial on my civic so i wouldnt have as must drag and strain on the drive train. now i figure there must be a reason you dont see fwds running them. im only runing 3-400whp so maybe they be worth it compared to someone whos 6-900. just figured id see if someone could break it down for me. pros and cons

 

Pro - They're streetable and give you more traction on the street than regular tires.
They will help save your drive train.

Con - Not a lot of traction at the track. Your 60' will suffer.
It does put more stress/shock load on the drivetrain.

Rwd vehicles get away with them because when they launch all the weight transfers to the back over the tires. On our FWD cars, when the weight goes to the back on launch, it takes away weight off the front tires causing us to loose traction. That is why the fwd guys run slicks with real low pressure. Plus, the wrinkle wall on the slicks wrinkle up, store energy and cause a slight slingshot when released helping us get out of the hole.
While the tread is somewhat soft on the radials, they are still much harder than a slick. There is no burnout to warm them up and because of the compound is why they do not hook like a slick do.
And that is the reason he is telling you it would be less drag and less strain on the drive train. Less drag because you keep more air in them. And less strain because of how hard they are they will spin a lot on launch and not try to grip as much. But if you learn to preload, it will help save your drivetrain a lot longer. Or run a clutch flow control valve by clutch masters or Tilton.

 

drag radials are far worse for drivetrain compared to slicks. slicks when sized correctly and are being used properly are very forgiving. ive snapped way more stuff with drag radials.

 

I can see that. The things I said about the radials saving the drive train is more theory than practice.
But regardless, the biggest con for a competitive drag racer is you loose a lot of traction and hurt your 60'.

 

ya im pretty good at preloading but still wanting to do a clutch release from clutch masters. ok but with my size of power would i still wan to use a 13" slick or run 15s as i dont have that much power do i need alot of side wall wrinkle or would the 15s with less wrinkle be better. ya ive scaled the car and did a 62.5 fron 37.5 rear weight 49.9 left side. left the number alone because this was where everything way after i set my ride heights and spring preloads. so figured was close enough . cars a ek hatch with me and full interior and turbo set up weights 2420 and a full tank of gas.

 

also ive looked for a long time but how much ride height difference do you want from front to rear? of is it as long as your precentages are good then dont worry about there being a difference cause right now i have a 1/2" difference on my car. was pulling 1.9s but my lanuch control wasnt working due to bad speed sensor but was leaving around 5500 and exhaust leak on the turbo i found the next day. but was dead hooking. no spin problems with my 22x8x15 mt et drags

 

The radial is simply a more efficient design. Radials have more ultimate hook than a slick, also the ability to run more air pressure without turning into a basketball. No need to lose speed running a radial half flat like you do a slick. Because there's a more defined "line" that you can't cross when it comes to spinning a radial, basically you have to tune out any momentary power/torque surges that could knock the radials past their traction limit.

The most common power surge comes from a grabby clutch. Any time a clutch grabs hard enough to pull engine rpm down, it's creating a torque surge. The quicker it pulls the engine down, the more intense the torque surge. Here's a simplified example- suppose you have a clutch that's grabby enough to cause an engine putting out 500ft/lbs to lose 3000rpm over .2 seconds. Let's say that 3000rpm loss over .2 seconds creates a 250ft/lb surge to the input shaft. That's a total peak of 750ft/lbs to the input shaft over that short .2 second period. That 750ft/lb surge could be enough to break parts or start the tires spinning. If you simply double the time over which that rpm loss occurs the torque surge will lose 1/2 it's intensity, dropping that original 250ft/lb surge over .2 seconds to just 125ft/lbs over .4 seconds. Now the peak of the surge is only 625ft/lbs. How is that accomplished?...delay the point of clutch lockup. Stretch the time to the clutch lockup point out even further to .8 seconds, that original torque peak of 750ft/lbs is reduced to only 563ft/lbs.

Lets look at the above example from a different perspective. Let's say the radials can only tolerate 600ft/lbs to the input shaft in 1st gear before they exceed their limit and start to spin. If your clutch locks up in .2 seconds and creates a 250ft/lb spike in torque, you will have to limit engine output to 350ft/lbs during that .2 seconds in order to keep from exceeding that 600ft/lb threshold that will cause the radials to spin. Stretch the point of clutch lockup out to .8 seconds and now there is no need to limit engine power at all, you actually have room to increase boost slightly before you reach the radial's 600ft/lb input shaft limit in 1st gear.

Another advantage in reducing the intensity of the power surge is that it reduces weight transfer to the rear tires. Smoothing out power delivery will always help a FWD car keep weight on the drive tires.

Not only does a power/torque surge occur on launch, it also happens just after the shifts. If a clutch does not slip on the shifts, the rpm loss that naturally occurs just after a gearchange can also create an intense torque surge that can break parts or knock the tires loose. This can be important if you are using a simple boost limit in each gear. Same basic rule of thumb applies, doubling the duration over which the rpm loss occurs will cut the intensity of the resulting surge in half.

On my personal car that i run radials on, i typically stretch rpm loss out over .8 seconds, well within the capabilities of my medium weight clutch assy and sintered iron disc. Conventional wisdom says it's very difficult to run radials with a manual trans, but after you understand the basic issue it becomes much easier.

 

The problem with a radial is there is so much suspension tweaking and dialing in to get them to work. Also if you spin a radial, it will blow the tires off even if you peddle it, there is no recovering on a radial whereas a slick can spin then hook. I tried for a whole weekend to get some radials to hook with my Camaro and it either wheel hopped or blew them off, and with a slick it hooks no matter what.

 

Nothing you can do to the suspension is going to work, unless you are delaying the point of clutch lockup out to at least .5 seconds or more. Anything less than that, the car is simply not yet moving fast enough for the tires to remain hooked without bogging the engine. Remember, either the clutch or the tires have to slip to keep the engine from bogging. With radials you can't be slipping the tires, so the only choice left that keeps the engine happy is slipping the clutch.

After you accept the fact that the clutch must slip to make radials work, the problem then becomes how to get the clutch to slip enough consistently when you want it to, while still having enough capacity to hold when you don't want it to slip. Simply reducing clutch clamp pressure does not work very well, it's a quick way to burn up a clutch. What does work well is to choose clutch that has plenty of capacity to handle the power, then slowing the rate of clamp pressure application to delay engagement. This allows enough slip initially to prevent a bog, while still having enough clamp pressure to lock up and prevent excessive slippage. Basically the clutch only slips when needed to make a fast pass, without bogging the engine or breaking the tires loose. Power application to the input shaft is much smoother as a result, makes the car much less likely to break parts. I accomplish this by adding a simple adjustable hydraulic cylinder to the clutch pedal... ClutchTamer.com

 

really when it comes down to it, hes telling you this because he absolutely has no clue about FWD racing, at all. That's how it always is. They try to apply their knowledge to something that completely invalidates that knowledge.

I just attended Lights Out 7(Biggest radial race on the planet)

Totally different world.

 

Hey if they can put down 3000hp to the track why couldn't a fwd do the same with a 1/4 of the power..... It just takes setting up the car. Slicks do make things easier to manage tho....

 

Well since you are close and all, i'll sit back and watch you struggle

it would be interesting to try it on a track that is setup for radials like MIR or SGMP.

They prep those radial events WAAAYYY different then slick events. Slick guys usually have to bog a little to get going on that straight up glue surface.

 

Agreed. RWD racers who have never done FWD will always try to give you advice based on what they know about RWD thinking it applies the same. Ive seen so many RWD racers at the track grab a tech saying "His front tires are flat!" and the tech just says its okay and moves on. Nothing wrong with knowing one skill set, but you shouldn't give advice on something you know nothing about.

 

We were out there , man what a great event.... just need more seating haha

 

Standing room only!

 

i had planed to get some type of clutch control devise regaurdless the type of tire i use. just going over to a gsr trans now and wont beable to use my 22x8x15 mt et drags. i love how hard these tires hook they actully hook to hard. but that mite also be that i need to leave on boost vs 7k rpm and i need to work on my clutch work some more. thanks for all the input. up here in norcal they dont prep very well so every event you mite as well go into as a no prep event so just wondering what tires would be best for that.

 

yea, nothing better than having 200 people on the start line and 2,000 in the staging lanes. True Story.

 

Hey , get in where you fit in.....

 

Sounds like WCF when the rotary cars are running! 5 golf carts, 2 suv's and 20 people on the starting line, women holding babies, etc..

 

Those folks , just askin to get hurt!

 

well heres some passes from tonight on my ek hatch drove the car 2hrs to the track had no one to watch the daily tires and tool box and jack so threw them in the back and ran with it. car was scaled 63% front 49.5 left side total weight 2365 with me in it before all this stuff i had in the car tonight thats also with a full tank of fuel. i know i through my precents off but had no choice so. these runs are on my old 15x8x22 mt's et drags on 7" wide wheels which they look to need wider. track isnt realy preped so nothing over 5900 and 3psi would hold off the line. btw no traction bars not after market lower a arms now if im able to do this with no wheel spin would i be have a hard time using radials with some traction bars?

 

I've never had luck running radials, crappy 60's and nothing to show for it but shattered cv joints and sheared axles. Slicks are so much more forgiving.

With very few exceptions I just smile and node at most rwd guys advice.

Have you had your car dyno'd? You mph seems a little low for your hp, weight and 60'

 

car weighted about 2600lbs last night. have not dyno yet wait to get few more passes in to fine tweak my tune on the top end as doing any street pulls doesn't have boost come in near as hard as it does at the track so all my tuning ive done its quite right for the track as my afrs are always rich. going back this next wed with all the weight in the car and should be able to leave a little harder then ill rent a hour of the dyno to try adding timing as im running 20 degrees at 14.5psi on my 61mm garrett. but it is werid that calculating my mph to weight to get a good hp guess is far off from doing it off the amount of fuel then engine is wanting. im at 58% on my 1000cc injectors with base pressure at 50 according to that i should be around 300ish according to the mph i run its only saying 250

 

or are you saying based off the 60ft and weight i should of had a faster mph? ya im wanting to get some 24.5/13x8 m&h's soon as i start to hit the limiter on my 22's

 

The key to running radials without killing parts is in controlling clutch engagement, especially with a turbo setup that ramps up boost down the track. Basic problem is by the time you get enough clutch to hold the power at full boost, the clutch does not slip long enough to get the car off the starting line without either bogging the engine or excessively spinning the tires. Adding a little clutch slip on pedal release is the key to bringing everything together, huge reduction in shock to the drivetrain as well.

The solution isn't hard, but it does take a little creative thinking. I'm just here trying to create a spark to help you guys get this figured out.