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That guy...
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Discussion Starter #1
We normall run a M/T 26x8.5 tire but last night we decided to give the new M/T radial a try and it didn't go very well.

Three hits, three failures... anyone wanna take a stab?

I feel like we were completely lost and really want to have a game plan before we go back out.

PASS 1
VIDEO - http://www.youtube.com/watch?v=nV6UZVI2wN0&hd=1
Tire = 18 PSI
Launch = 3400 RPM
Front Travel = 4"
Front Shock Ext = 3/4 Stiff
Front Shock Comp = Full Stiff
Rear Shock Ext = 50% Stiff
Rear Shock Comp = 3/4 Stiff



PASS 2
VIDEO - http://www.youtube.com/watch?v=46857tlhftc&hd=1
Tire = 18 PSI
Launch = 3500 RPM
Front Travel = 4"
Front Shock Ext = 3/4 Stiff
Front Shock Comp = Full Stiff
Rear Shock Ext = 50% Stiff
Rear Shock Comp = 3/4 Stiff



PASS 3
VIDEO - http://www.youtube.com/watch?v=pxfyiyEu_LY&hd=1
Tire = 18 PSI
Launch = 3500 RPM
Front Travel = 4"
Front Shock Ext = 1/4 Stiff
Front Shock Comp = Full Stiff
Rear Shock Ext = 50% Stiff
Rear Shock Comp = 3/4 Stiff

 

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I'd say the last run the front rebound was too soft. Popped up too quick, dropped down and unloaded.

The order looked like it spun fairly far out and each next video is spun sooner.

How was the track prep and track temp?

Just looking at your shock settings, I would have tried the rear shock rebound softer and set the compression at max firm.

What kind of rear suspension? What power adder if any?
 

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The first run looked to to be your best of the three. Usually with my N/A car on 275's, if I can make it 5 or 10 feet it'll stay hooked up the whole run. I can't help but wonder if there was something to the track prep where the VHT wasn't sprayed very far out, something with the start line pad transition, or something to make the tire let go where it did.

You made it pretty much to over 2 seconds till the tire spin set in which really the car should have been go to go for a full run. I could see if you were aggressively adding power around that time, but all I see on your graphs is timing ramping back in from maybe a launch retard?
 

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That guy...
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Discussion Starter #4
Thanks,

I also thought the first pass looked the best but it bogs hard off the hit and knocks the tire off as soon as we give it power from the timing ramp... The track is not known for being great but it didn't seem like junk either.

The last pass was a ton looser on the front with less timing out on a longer ramp to try to plant the rear... didn't work at all but on the previous passes the front looked way too stiff... like a chassis car... also looks like no travel although we measured 4".

1st pass also had the lower launch RPM
 

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Chupa Cabra
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Take the compression to full stiff in the rear and a looser extension in the rear, try the front where it was on the first pass. See where that gets you.
 

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DJ, your g-meter seems way low, you need an initial hit of at least 1.90 ish. Those tires like to be hit hard and then ramp the power in quickly and evenly. On the first pass you never hit them hard and so they were never really planted and that's why they broke loose when you applied power.

First, you need to loosen the extension on the rr shocks to 1/4 stiff as a baseline (you may need to go looser). Leave the front ext 1/4 stiff too. Then leave with more power, Whether it be timing or rpm, however you do it with those backwards turbochargers :).

Another thing is I tried my tires at 18 and but needed more bite so I ended up at 17.5 which seemed to help...

Where are you testing at? Must be nice :)
 

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Take the compression to full stiff in the rear and a looser extension in the rear, try the front where it was on the first pass. See where that gets you.
And yes, max out your rr compression.
 

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seems like a lot of front end travel
 

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That guy...
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Discussion Starter #9
And yes, max out your rr compression.
You stagger the right rear? Independent from the left rear?

Congrats on the fast passes...
 

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That guy...
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Discussion Starter #10 (Edited)
DJ, your g-meter seems way low, you need an initial hit of at least 1.90 ish. Those tires like to be hit hard and then ramp the power in quickly and evenly. On the first pass you never hit them hard and so they were never really planted and that's why they broke loose when you applied power.

First, you need to loosen the extension on the rr shocks to 1/4 stiff as a baseline (you may need to go looser). Leave the front ext 1/4 stiff too. Then leave with more power, Whether it be timing or rpm, however you do it with those backwards turbochargers :).

Another thing is I tried my tires at 18 and but needed more bite so I ended up at 17.5 which seemed to help...

Where are you testing at? Must be nice :)
The 8.5's have held up to 1.8 G and that makes for a much nicer run. Next time out I'll try to hit the tire with more timing and see if it likes it... it's just so crazy to spin and add power to correct it.

I have a light car so I'll try less on the tires as well (I was told to start at 18 and og up from there).

We were testing at Sac... we were gonig to go again today but after last night, I didn't want to go and waste a day without having any real direction.

I also think the converter is wrong. On the shift we see a 1600+ RPM drop and it tries to (actually does) knock the tires off...
 

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Chupa Cabra
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What does your car weigh DJ?

Mine weighs 3002lbs race weight and for example on the 275/60 Hoosier I run 18-19psi of air. I know I could possibly go lower being my car is probably even lighten than yours, but I like to not have any sidewall distortion or flex on my car which I get at 16psi. Not so much at 17psi, but at 18-19psi it leaves a nice contact patch for my liking and seems to get up on the tire faster into the run.

I'd also try between 18-19psi on your car if it weighs what I think it does(3200?)
 

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H&H Racing
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DJ, your g-meter seems way low, you need an initial hit of at least 1.90 ish. Those tires like to be hit hard and then ramp the power in quickly and evenly. On the first pass you never hit them hard and so they were never really planted and that's why they broke loose when you applied power.

First, you need to loosen the extension on the rr shocks to 1/4 stiff as a baseline (you may need to go looser). Leave the front ext 1/4 stiff too. Then leave with more power, Whether it be timing or rpm, however you do it with those backwards turbochargers :).

Another thing is I tried my tires at 18 and but needed more bite so I ended up at 17.5 which seemed to help...

Where are you testing at? Must be nice :)


1.9? Thats it?:p
 

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Turbo Terror
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1st two passes, the car left on no power......when the power finally came on (too far out) the suspension had already settled, and the car had fell off the tire by then.


The 3rd pass, if you had cranked the rebound up would have been a good pass or very close. When it left it just slammed the tire into the track. You can hit a radial hard and with a lot of power but the suspension seperation has to be slowed and controlled. And once it's planted and the car is rolling it has to stay planted.

This is why so often guys will end up getting their shocks revalved, because once you figure out how to leave on some power...most of the time you run out of shock. You keep on tightening them, and keep on upping the power, but eventually there is no turn left!



Maybe somebody else is seeing something different than me, but it looks like it's slamming the hell out the rear tire to me. It just goes into violent spin before you can see it seperate out more.
 

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That guy...
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Discussion Starter #19
thats all the g's a turbo car needs at the finish line to go 4.77 on 275's i guess :) :smt102
I smell a trap in this reply.

Why change tires though?
Dont you want to try and be top dog on an 8.5 before going up??
We'll still run PSCA 8.5, we just don't have the ability to get the car to 3500# to run WCHRA 8.5 and we want to support Tim.


1.9? Thats it?:p
Hey Kelly, I don't believe you... post your G graph :p
 

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That guy...
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Discussion Starter #20
1st two passes, the car left on no power......when the power finally came on (too far out) the suspension had already settled, and the car had fell off the tire by then.


The 3rd pass, if you had cranked the rebound up would have been a good pass or very close. When it left it just slammed the tire into the track. You can hit a radial hard and with a lot of power but the suspension seperation has to be slowed and controlled. And once it's planted and the car is rolling it has to stay planted.

This is why so often guys will end up getting their shocks revalved, because once you figure out how to leave on some power...most of the time you run out of shock. You keep on tightening them, and keep on upping the power, but eventually there is no turn left!
Front or rear? I fought with my buddy about this because on the first two passes the car didnt seem to transfer at all. He's going to read this and start gloating if you mean front.

We had the vales on the front changed from stock 100# @ 1"/s to 400# 1"/s. Rears are stock.
 
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