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Trying to put the power down without wheelie bars

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Trying to put the power down without wheelie bars Empty Trying to put the power down without wheelie bars

Post  Dave De on October 16th 2019, 10:40 pm

Last Sunday at Milan Dragway it dead hooked and I couldnt recover it when it rolled from the right slick to the left while on the bumper. I thought the car was going to roll over on the side. So I lifted and down it came crashing hard and leaving the front end damaged including that nice pan that Lem sold me just 2 years ago.
A lady happened to take video of the car and sent it to me, it is grainy but I could see that the rear end had separated on the hit. I had my rear shocks set near maximum for extension to spread the hit out but it still stood on the rear end. The front shocks were 2 clicks from maximum and prior runs it felt like the tires were being plucked out of the beams without the suspension moving.

The car is 3250#, ladder rear that normally 60's in the 1.25 second time that runs 9.0's in the 1/4
tires are Hoosier 32 x 13.5 W's

Am I stupid thinking that this could be controlled without bars?
I'm going to bars and see that some are spring loaded and some are rigid. Also length varies.
Which type and how long for this wheelie crazy package?
After the bars are on do I set the shocks for maximum hit?

Video
https://youtu.be/2WBKJ_LJ-6c


Last edited by Dave De on October 16th 2019, 11:14 pm; edited 1 time in total (Reason for editing : added video)
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Post  wickettoby1 on October 17th 2019, 12:01 am

Holy s**t, you were at Milan when they actually prepped the track😃😃😃
Joking aside sorry to hear about the damage from you’re “return to earth”.

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Post  wickettoby1 on October 17th 2019, 12:01 am

Double post

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Post  wickettoby1 on October 17th 2019, 12:03 am

.

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Post  DILLIGASDAVE on October 17th 2019, 5:54 am

Eh, ladder bars can get damn violent with decent at-launch power/torque numbers to work with. And the average off-the-shelf coil overs with standard valving installed might not be able to keep up and quickly become overwhelmed. Combine the two and boom....violent dead-hook happens and the car climbs the ring gear before you can react.

Or it could have just been unusually good track prep.

Either way you probably need to think about doing something/anything to generate some wheel-speed at the hit. That usually means slowing down the suspension's initial hit (using any number of methods) , or adding wheelie bars, or adding more power, or playing with slick air pressure.

Or keep the dead-hook & calming it back down with either an ignition box timing retard ramp, or use one of the Davis boxes.
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Post  Dave De on October 17th 2019, 10:30 pm

Wheel speed on the hit. Tires are at 32.2 tall, the gear is only 3.70 and the first gear is 2.40. Some look for a multiple number 2.40x3.70=8.88
I was thinking to go a 3.50 gear to get it down to 8.44
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Post  stanger68 on October 18th 2019, 12:23 am

What launch rpm? Trans brake? I’m far from a tuning guru but I would take the cheap route to start with to get an idea what the car will like. If you’re using a trans brake, swap it for a studder box and leave at a much lower rpm and let the converter soften the hit. Doing it this way you may have to adjust your reaction time though. This was recommended to me by a converter manufacturer for running foot brake with a lot of power.

I’m still trying to work the bugs out if the rest of the car but that method does keep the front end down.

Question is if you can drive it good enough Very Happy

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Post  stanger68 on October 18th 2019, 12:26 am

stanger68 wrote:What launch rpm? Trans brake? I’m far from a tuning guru but I would take the cheap route to start with to get an idea what the car will like. If you’re using a trans brake, swap it for a studder box and leave at a much lower rpm and let the converter soften the hit. Doing it this way you may have to adjust your reaction time though. This was recommended to me by a converter manufacturer for running foot brake with a lot of power.

I’m still trying to work the bugs out if the rest of the car but that method does keep the front end down.

Question is if you can drive it good enough Very Happy

You can do the same thing with a trans brake if you’re worried about breaking beams. just wire the two step in the same circuit as the brake

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Post  Dave De on October 18th 2019, 8:48 am

Broader Performance pro tree valve body. leaving off 3600 rpm 2 step with a converter flash at 4400 rpm. Trans brakes are consistent.
I know this package should have a glide but I just dont want to do that. I am thinking the 3.50 gear and pulling some timing may be best or just go bars.
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Post  litshoot on October 23rd 2019, 12:34 pm

2nd gear start an option, maybe lower launch rpm a couple hundred. If it helps then get converter rebuilt

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Post  Dave De on October 23rd 2019, 6:31 pm

litshoot wrote:2nd gear start an option, maybe lower launch rpm a couple hundred.  If it helps then get converter rebuilt

Leaving in second with a 1.40 ratio wont cut it. Also the brake wont work in second gear.

I am going to a lower number ratio somewhere between 3.50 and 3.65 and use bars.
Will that help with instantaneous wheel speed?
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Post  DILLIGASDAVE on October 25th 2019, 5:10 am

Dave De wrote:.....I am going to a lower number ratio somewhere between 3.50 and 3.65 and use bars. Will that help with instantaneous wheel speed?

If the car is already setup for and/or has a set of wheelie bars you could save a few bucks and test the bars first before spending money on a gear change. You could test lowering the wheelie bar height pass-to-pass until the car goes from trying to yank the nose up-out of the beams to flat-out spinning the slicks. Then raise the W/B height back up a little and fine tune from there with air pressure changes.
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Post  Dave De on October 25th 2019, 11:29 pm

I like your plan. I'll get the front end fixed then work on the bars. Should the bars be spring loaded or rigid?
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Post  DILLIGASDAVE on October 26th 2019, 6:29 am

Dave De wrote:.........Should the bars be spring loaded or rigid?

Meh, kinda depends on a few things. In a lot of situations if the w/bars are short (or are the older design with aluminum strip for the lower "bars") being spring loaded can be a benefit. But if the w/bars are long and made of all thin wall 'moly tubing (and doesn't use aluminum strip lowers) then they usually aren't spring loaded because the w/bar it's self flexes under load and in effect acts as the "spring".
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Post  snuff98 on October 26th 2019, 2:53 pm

I run a ladder bar also, tightening the front shock setting, limiting front suspension travel, and even changing front and rear ride height can help with wheel stand. My car would not wheel stand unless the track was real good. I put wheelie bars and the 60' picked up and got deadly consistent 1.17 pass after pass. It never drove that well before the bars.

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Post  STR-LGL-70 on October 27th 2019, 8:48 am

I'm getting ready to go down the same path, ladder bars with C-6 and I think we are both making similar power- how much set back does your engine have? Also been reading up on ladder bars and I saw somewhere where sprung (wheelie)bars were recommended with ladder bars.

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Post  DILLIGASDAVE on October 27th 2019, 9:25 am

I guess another "simple/easy" option is to just hanging some given amount of weight ballast out on the nose and test to see what happens. The farther you can hang the weight ballast out on the front/nose of the car the greater the effect it will have (and do it with less total weight).

Years ago while working a set of scales on a full chassis car we played around with the placement of a small 5lb ballast puck. It is amazing how much effect just 5lbs of ballast has on the front/rear weight percentages as you move it farther & farther out on the nose of a car.
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Post  snuff98 on October 27th 2019, 1:47 pm

I run 72" solid wheelie bars with ladder bars, works very well for me.

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Post  Dave De on December 18th 2019, 1:14 am

STR-LGL-70 wrote:I'm getting ready to go down the same path, ladder bars with C-6 and I think we are both making similar power- how much set back does your engine have? Also been reading up on ladder bars and I saw somewhere where sprung (wheelie)bars were recommended with ladder bars.

Sheldon G

Sheldon,
Sorry for not responding sooner. My car is close to 50/50 weight distribution. The crank balancer is in line with the front wheel spindles. I saw the sprung bar recommendation as well.
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Post  Dave De on December 18th 2019, 1:16 am

snuff98 wrote:I run 72" solid wheelie bars with ladder bars, works very well for me.

Thanks for that info. I might be contacting you spring season 2020 for some setup recommendations.
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Post  Dave De on August 27th 2020, 2:01 pm

Update...
I had way more damage and needed to go thru the engine as well as replace the control arms. It had 2 burnt pistons and a blown head gasket. Also total cam and lifter failure.
Many parts were held up from Covid delays. I finally got to the track two weeks ago but without bars. Working on setting up the suspension to make it work ended the day with a 1.25 sixty foot but with the front end pulling a 2 footer. All went well with the engine having a 1050 Dominator due to the 1450 showing bad AFR at WOT.
Discussing my wheelie plight with another racer he said his car would do the same until he lowered the suspension travel to 2.75" with limiters.
I measured my travel and found it to be 3.1" then noticed that I could limit it to 1.75" and made that change. I can probably get it down to 1.50"

Has anyone made gains here by lowering the travel? What do you think?

Refresher on details
3250 pounds tube chassis, ladder rear, MII front, 585 cubes, SR-71, small solid roller, 13.3 comp., E85, C6 trans, Broader brake leaving at 3600 2-step, flash to 4500. Car is close to 50/50 weight.
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Post  DILLIGASDAVE on August 28th 2020, 4:25 am

Installing travel limiters on the front is one usable adjusting method/tool you can try. Another is tightening/stiffening the front shock/strut extension valving, (if the shocks/struts have adjustable valving).

Limiters adjust the total extension travel distance, shock/strut valving adjusts the speed/time of that travel. Valving adjustments will have a softer/smoother effect on the rest of the suspension, and thus less likely to unload the rear suspension as the front is "limited" during travel. limiters will have a more pronounced/violent effect on the rest of the suspension, and thus more likely to unload the rear suspension as the front abruptly reaches it's "limit" during travel.
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Post  Dave De on August 28th 2020, 8:21 am

Thanks Dave
I think what's happening in my case is that to keep the front end down to be reasonable I have to tighten the front shocks up so much that on the release the car pulls the front end out of the beams without any travel taking place at all.
Shortening the travel by 40% may allow the shock adjustment to be one or two clicks lighter and help that transition at the release but still keep the tires less than a foot from the surface? At the same time the rear has some time to load and not blow the tires off.
Am I dreaming here?
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Post  DILLIGASDAVE on August 30th 2020, 4:02 am

Meh, truth is since every car is different you will never know for sure until you try any given setting.

It might work better. Or you might find the shorter travel distance combined with a looser front extension valving setting lets the front come up even faster at first, and then BAM! the abrupt travel stop shocks/unloads something. Or go the other direction and try the limiter with tighter front extension valving to smooth/soften the point at which the limiter stops travel. But that too could cause problems if you don't have enough "at-launch" torque to work with and see it grunt and fall on it's face.

But since it's already yanking the front tires straight up-out of the beams you might find that adjusting the front suspension is less effective than adjusting the rear suspension, (or a gear change, or moving weight around).

Test, test, test.
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Post  Dave De on September 7th 2020, 10:43 pm

Update
Limiting the front end travel from 3" to 1.75" worked out very well. The wheels never came up more than about 9". I now have shock tuning for the reduced height. I am considering setting the rear shocks to hit it harder. The front can be loosened up s well.
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