Drag radials ?

[Brian Conway 264]

I have a pair of BF Goodrich G-Force Drag Radials 215-60-14 on loan.  Should I run these instead of the BF Goodrich Radial T/A's 215-70-14 on the car now ?  I have been told that the smaller drag radials will help out with the 3.25 gears out back.  Racing in San Diego at one of the Two 1/8 mile tracks.  My last outing I ran on the T/A's and never got out of second.  Brian

[barnett468 418]

Not quite sure what your question is . A smaller tire will accelerate the car faster but will spin more if all else remains the same, but being a drag radial, it will spin far less than a ta radial, but if you don't have enough power, you want some spin off the line.

 

Hope this answers your question.

[Brian Conway 264]

Well sort of.  Let me explain; spin is not a problem can get plenty of spin with either tire.  The 428 CJ puts down plenty of torque even with the 3.25 gear.  A friend did some mystical math and tells me the smaller Drag radial combined with the 3.25 gears results in a seemingly 3.45 rear end.  Make sense ?  Anyway I'am going to give the drag radial a try and see what happens.  Thanks,  Brian

[ray1970 88]

I have 14in T\As You could not hook up on a spike mat..

[barnett468 418]

Well sort of.  Let me explain; spin is not a problem can get plenty of spin with either tire.  The 428 CJ puts down plenty of torque even with the 3.25 gear.  A friend did some mystical math and tells me the smaller Drag radial combined with the 3.25 gears results in a seemingly 3.45 rear end.  Make sense ?  Anyway I'am going to give the drag radial a try and see what happens.  Thanks,  Brian

 

 

You can increase traction with drag radials by lowering the air pressure significantly . check with the tire mfg for pressure limits.

 

Also, check the mfg date . If they are several years old, i might not use them.

.

[Brian Conway 264]

Took a look at the Manu. date for the drag radials and looks like 1998.  So may not be running on those.  Maybe use the T/A's with about 25-28 psi ?

[barnett468 418]

Took a look at the Manu. date for the drag radials and looks like 1998.  So may not be running on those.  Maybe use the T/A's with about 25-28 psi ?

 

ummm, yeah, those drag radials are museum pieces.

 

unfortunately, you could run the ta radials with 6 psi and it ain't gonna help them . they are probably one of the lowest traction tires made these days . seems like they changed their compound.

 

just get some mickey thompson et street radials and be done with it.

.

[cobra3073 24]

Well sort of.  Let me explain; spin is not a problem can get plenty of spin with either tire.  The 428 CJ puts down plenty of torque even with the 3.25 gear.  A friend did some mystical math and tells me the smaller Drag radial combined with the 3.25 gears results in a seemingly 3.45 rear end.  Make sense ?  Anyway I'am going to give the drag radial a try and see what happens.  Thanks,  Brian

The difference diameter of these two tires ( 24.20" Versus 25.90") will give you approximately 300 point jump in RPM at 100 MPH.

 

The RPM formula is what you are working with here to see the results. The formula is:

 

RPM = MPH X Gear ratio X 336 divided by tire size

 

In your case for the 70 tire using hypothetical 100 miles at the end of your run would be:

 

100 X 3.25 X 336 = 109200 divided by tire size of 25.90 = 4216.2 RPM at the end of the run

 

Going with the 60 tire using hypothetical 100 miles at the end of your run would be :

 

100 X 3.25 X 336 = 109200 divided by tire size of 24.20 = 4512.39 RPM at the end of the run

 

If you substitute the 3.45 gear into this equation (using your 70 diameter tire), you will see:

 

100 X 3.45 X 336 = 115920 divided by tire diameter of 25.90 = 4475.6 RPM

 

Of course, You can always go to one of the online calculators and key in the information if you don't like doing it manually. LOL

 

...my $.02

 

BT

[RPM 1,190]

The difference diameter of these two tires ( 24.20" Versus 25.90") will give you approximately 300 point jump in RPM at 100 MPH.

 

 

BT

 

Would not the ratio difference be the same no matter what the speed?

[barnett468 418]

Would not the ratio difference be the same no matter what the speed?

 

The actual gear ratio would of course be the same but the tire size has an affect on how it all works to together.

 

The best setup for drag racing is numerically high gears and tall tires because the taller the tire is, the more contact area it has . If you have tubbed wheel wells you can run wider tires instead of taller ones.

[cobra3073 24]

Would not the ratio difference be the same no matter what the speed?

As noted by Barnette468 the "gear" ratio would remain the same, however if you are referring to RPM, it would change at a different (higher or lower) speed.

 

You would use the speed you are at going through the traps. You can validate my manual figures for the 70 series tires and the 60 series tires by going to the calculator in this link

 

http://www.csgnetwork.com/multirpmcalc.html

 

Your 70 series tires are 25.90" in diameter and your 60 series are 24.20.

 

As you will be able to see, the gained RPMs (when using the 60 series rather than the 70 series)tires going through the traps will be lower at lower speeds.

 

For the 1/8 mile racing, you really need deep gears to get the best results unless your are bracket racing, IMO.

BT

[barnett468 418]

Another way to look at it too is that the tire size is another gear ratio . Smaller tires increases the rpm per mph and larger ones decrease it.

 

Ideally you want the taller tires for cruising at higher speeds and the smaller ones for drag racing because of the ratio, however, as mentioned, the smaller the tire, the less traction it will provide if the tire type remains the same, therefore, in this particular situation it is more of an even trade off that likely won't gain you much.

[Brian Conway 264]

Went down to Jack Murphy stadium Friday night and the Race Legal Drags.  Decided to run the drag radials and see what happens.  Short story is low 9's and low 80's.  That's a best guess as the machine seemed to mal-function on my last/best run. This 1/8 mile track has a reputation for very poor traction and it's been about 5 years since my last visit and that memory had faded.  Well it was refreshed last Friday.  First run got sideways at the lights and finished in the 10's somewhere.  Second run, just to see, tried starting in 2nd and did a little better but I burned a bit of clutch.  There after just started letting air out and ended up in the low 20 psi range.  I think 5 years ago I was in the 12 psi range, when I was done, but can't remember for sure.  Anyway that's the last go around for those tires and lest I forget the last time at that track.  Car and motor ran great, don't think I ever past 5000 rpm's, mostly top of second gear at the traps, think I shifted into 3 rd once.  Stock shifter was really sticky when shifting into and out of 2nd.  May have something to with burning clutch disc and pressure plate ?  Had some fun didn't break anything and had a good time.  Brian

[RPM 1,190]

Nice to see somebody else still calls it Jack Murphy Stadium. Sounds like you had a good time, so were you happy with the old drag radials?

[Brian Conway 264]

The tires were fine and with some psi adjustments ET performance improved.  Track traction is a problem for every one and you just do the best you can.  Yeah leave it to the political whores to re-name that stadium.  They have no shame.  Jack Murphy deserved better.  Brian

[barnett468 418]

The tires were fine and with some psi adjustments ET performance improved.  Track traction is a problem for every one and you just do the best you can.  Yeah leave it to the political whores to re-name that stadium.  They have no shame.  Jack Murphy deserved better.  Brian

 

the changed the name of jack murphy stadium?

 

glad it worked a little better, now save up for some real tires.

.

[barnett468 418]

The tires were fine and with some psi adjustments ET performance improved.  Track traction is a problem for every one and you just do the best you can.  Yeah leave it to the political whores to re-name that stadium.  They have no shame.  Jack Murphy deserved better.  Brian

 

Those drag radials are not fine . They are very old so they lost all their bite just like my grand,a did . once she got new teeth her bite was fine again . if you get new drag radials, their bite will be fine again.

 

Micky Thompson ET Street Radials or go for the gusto and buy real drag tires and swap them at the race.

 

The Yelloybullet guys say run the Street Radials at 18 psi and get them hot first in the burn out box.

 

.

[Midlife 814]

I remember buying corn from a farm that also had dairy cows at the site of Jack Murphy stadium back in the early 60's.  Then they built Fascist Valley Mall as well...sigh...

 

My grandfather homesteaded cattle in Fletcher Hills back in the 1910's.  My, how SD has changed over the years.

[Brian Conway 264]

Yes the drag radials were a little hard.  The burn out box is little more than a depression in the asphalt with some water sprinkled on top.  Real drag tires and some new rear gears would go a long way to getting some better ET's for sure.  $ = Speed.  I remember the dairy farms, horses and other live stock down there.  Those days are long gone. Now days they can't build the condo's fast enough.  After the Chargers leave town the city will be tearing down that stadium and puff no more drags.  I'll be 68 in a couple weeks and I find myself saying " I remember when " an awful lot.  Brian

[RPM 1,190]

68??? Holy crap Brian, I figured you to be around 35ish. Guess I ought to check the profile pages more often.