Radial tire question
 

If you have a 31x13 radial tire how much would it hurt to put the tire on a 15x12 wheel vs a 15x14 wheel? Thanks

Re: Radial tire question
 

Are you thinking about trying radials with a stick? Not a good idea, I don't know anyone who is having any luck with manual trans applications. My experience was that they hook sometimes and about every 5th run, it would just blow the tires off. Not a controlled spin either, pretty much a total abort situation.

Re: Radial tire question
 

I have seen no difference between 12 and 14 inch wheels
on 13/31 Tires

Re: Radial tire question
 

Radials with a stick requires a different approach regarding the clutch and gearing. The clutches you guys typically run would not be my 1st choice, and something like my ClutchTamer is also needed to control the hit.

Since a radial needs to be dead hooked, there's no need for a deep 1st gear ratio to control tire spin. Less ratio in 1st means less torque available to break the tires loose, but that loss of torque at the tire is offset by spending more time in the gear with the most multiplication. More even gear splits also improve recovery rpm, with the side benefit of less energy discharge on the gearchange. Less energy discharge on the shift lowers the risk of breaking the radials loose.
...You need enough mass in the clutch so that it doesn't overheat while you are leaning on it, also need one that doesn't depend on centrifugal assist to hold.
...With a properly controlled clutch hit, you won't need a 2-step and will be able to launch off the limiter without breaking the radials loose. Higher launch rpm means more energy available to get the car moving when the clocks are running.
...Wheelspeed spikes after WOT clutchless shifts need to be minimized with radials, bring those under control by adjusting clutch base.

Grant

Re: Radial tire question
 

Intrinsic value.

Re: Radial tire question
 

From everything I've tried with radials, they always liked a wider rim than the tire. When using a narrower rim I had trouble with bad wobble and less contact patch.

Re: Radial tire question
 

I use the 13" X 31", on 14" wheels, so I can run more air (13 to 14 psi).

Re: Radial tire question
 

,Wide rim. If you can manage deformation early, you're managing spikes. If you can manage W/S spikes, the potential for leaving tracks could present itself, bridging the gap. Wider wheels than normal?

Re: Radial tire question
 

Mike, what is a "W/S spike"? I've never heard that term.

Re: Radial tire question
 

After the car leaves pause, look in the groove Ed. You can get away with it, bias tire. No wheely bar it's essential to not getting on the bumper. Wheel speed spike.

https://youtu.be/pgWw9ZcX4YM

Re: Radial tire question
 

Thanks, Mike. I've never had that. I have a low hp car that always just dead hooks.

Re: Radial tire question
 

This is low hp as well around 750hp, with aim to dip in the 5's 1/8 N/A 23 sbc @3250 pds 10 x 28 bias tire. New combo just for fun, no particular class in mind. We kinda stumbled on using the wheelspeed to our advantage, first time we took it out went 6.01 on a set of ten year old tires. A lot of wheelspeed w /no wheelstand. Took it from there using shock adjustments favorable for wheelspeed on new tires to keep the car off the bumper no wheely bars.

Re: Radial tire question
 

Thing about radials on a stick car, stick cars usually need to turn the tires a little at launch. Radials don't "recover" like bias slicks. I was with a friend who had a fast Pro Stock car, when he decided to try to make radials work. Last I asked him about it, he never made them work. When radials spin, from what I have seen, they spin. Bias tires I have had recover much better.

Re: Radial tire question
 

FWIW,a few years ago a friend was running a 305 stocker stick car.I let him try my Hoosier 9x30 radials.Had them at 15-16 psi.I run 20-22 on my auto.Made 2 runs hooked on both,picked up just under a tenth and almost 1 mph over his M/T bias.The track had good bite that day. gsa612

Re: Radial tire question
 

When I did try this a few years ago, I had to run them down to 10-12 PSI, they didn't work at all at the normal 20 PSI range that the auto trans guys seem to run. Interestingly, I picked up nothing as far as ET goes which surprised me.

Re: Radial tire question
 

Not a stick guy but good reading and learning. Back in the 70s I would go to the track with a good friend who had a 64 Vette M/P 277 cu in. They had to spin the tires (14x32) at 10,000 + rpm or it would stand on the bumper. Not too much science in clutches back then. I imagine a dead hook with radials would rattle teeth and pull your eyes back around your head, and very hard on parts.
Mike

Re: Radial tire question
 

You would think at that low psi it would drive the rim into the ground making the tire oval,then unload on extension with the radial sidewall.You may have to change launch rpm and clutch settings and tighten the shocks for less "hit' to get it off the line clean.It would be more of a challenge on a higher HP combo. gsa612

Re: Radial tire question
 

Someone will bridge the gap. They always do. It's essential-intrinsic.

Re: Radial tire question
 

Mike, not bashing your product but have you checked with NHRA about the legality of this for Stock & SS? The reason I ask is that I proposed something similar to this quite some time ago and was told absolutely not. They said that anything that affected the release of the clutch linkage would not be legal. I think their issue is that this kinda gets into the delay box gray area. Jim

Re: Radial tire question
 

By-product- ramification of rolling up sleeves unambiguously, possibly. Unless new tire technology solves the equation. Although once that happens, it's no longer an advantage, dominion.

If you're referring to me.

Re: Radial tire question
 

If that question was intended for me, I have no idea if it's NHRA legal for stock or SS. It does not affect the manual release of the pedal with your foot, it only stops the pedal's return at a pre-determined point. Basically the same as adjusting base pressure, except that it also has a bleed that allows additional pressure to then come in at a much slower rate. That allows more slip during launch without blowing thru the clutch in high gear.
Here's a Psi graph showing what it does on a hyd throwout bearing. The vertical drop of the trace was all foot controlled. It's only after the clutch hits that pressure drop is controlled (acts on the pedal itself, also compatible with mechanical linkage)...

http://grannys.tripod.com/clutchtamergraphintro.jpg

There's an article in the April issue of NMCA/NMRA's Fastest Street Car Magazine. I have not seen it yet, but I hear they interviewed some racers that are using it.

Grant

Re: Radial tire question
 

I always thought you could not run a hyd clutch in stock super stock. Tom

Re: Radial tire question
 

Been that way for years. Maybe they will.

Re: Radial tire question
 

So, the bias slick's fundamental for traction is its deformation. > High energy losses at all frequencies. So, the bias slick is fundamentally inefficient.

The radial is the opposite, low energy loss at all frequencies. Traction at all frequencies if you can keep it from deforming. Efficient, less rolling resistance. Faster, quicker et's.

The fundamental for wheel speed we've found effective for radial tires is the same as limiting wheel stands. Prolong the period of time the shaft is neutral in, or even exiting the damper/shock main body. We run a two way rebound adjuster on a heavy 2950pd small tire radial nitrous leaf spring car to combat wheel stands. No wheely bars allowed in the class. It lays tracks 275 radial, one teen sixty foot. There's another idea, maybe smaller tire would be easier to manage, deformation. Dunno, be interesting to see who gets there first on a radial.

Re: Radial tire question
 

Mike.
We have been using wheel speed/slippage to go fast in Comp/Modified/Gas classes for 4 decades. At the time those were not bracket classes. We all know bracket guys want a dead Hook. A turn to a turn and a half after the hit on roll out usually produces the quickest ET. Watch this with no wheelie bars and a V-6. The tire slips gets it off the line. The engine stays up on the converter after the hit. Hard to dial.
https://www.youtube.com/watch?v=eZPI6eCN8pE
We didn't have computers back in the early 70's and there was a lot of trial and error to make things work. Ed Wright knows what I'm talking about. He was there, too. Glad to see you guys working on this kind of stuff. That is getting the performance instead of being one of the dead hook crowd.

Re: Radial tire question
 

Clutch hit control is what you need to make radials work with a stick.

I don't share competitive graphs, but this one had a few problems so I can show it here. It shows what a dead hook launch looks like using one of my clutch hit controllers. 302ci sealed crate engine running the spec tune, 3100lbs. Class doesn't allow radials, so this run is with a 10.5" bias slick @ 18psi...

http://grannys.tripod.com/032419.PNG

First problem was not enough delay after the hit, which caused rpm to get pulled down to about 5200 after launch. 5500 is typical.
Second problem was the PP needed to be shimmed a little more in order to control those wheelspeed spikes after the shifts.

Depending on the track/conditions, it's not unusual for the above car to be able to go above 20psi with bias slicks and still dead hook without pulling rpm below 5500.

Re: Radial tire question
 

Radials can be made to work. All of J Allen Sherman stick customers use radials except for me. I just haven’t messed with them yet. Steve Kent uses them on his AH cud’s and his bad azz SS/B Vette. Stan Holt and Jarrod Grainer run radials on both super stocker and their stick shift comp car. Go to dragracertv and watch this pass weekend runs by Jarrod Grainer 66 Chevy II and watch how it leaves on those radials. It’s a thing of beauty.

Re: Radial tire question
 

Good call. That's a bad dude. 1.38 on the back tire. Thanks for the tip. That's a clinic.

https://i.imgur.com/ke3HBvE.png