1st drag radial test

I tested with the 3754r 275 drag radials for the first time Friday. I am posting a couple of videos, 1 in real time and 1 in slow mo of the 1st pass. Straight off the trailer just as it was the last test session when slicks where on the car (best the car has ever done et and suspension) with no changes. 17lbs of pressure. It dead hooked (surprisingly) and seemed like it was going to do fine until the front tires came back down. Rear unloaded and blew the tires. Being they were brand new tires, I was the second car on the track, and the radial car ahead of me had a lot more trouble than I, we left everything the same and decided to hit it again. Exact same outcome, same spot, racepak data is identical. This was a slick prepped marginal track. This was a test and tune night that encourages street cars to come race but turns the track to shit quickly. I tightened up on the front struts to try again but the track was gone from the street cars, no rubber left at the starting line, and was like ice when I let go of the button. Maybe you guys with radial experience can save me some time and head ache  

start by slowing the front end down


****Edit I see you tried this. Is the front end tied down or at least limited?

Looking at the slow motion deal.....have you tried slowing the extension in the back? What did you ever come up with for the IC length? Radial cars usually like shorter IC's.

right where it starts blowing um off is about where it really starts making power it sounds like.

you may need to get some sort of way to control or ramp timing. And Id get it on a radial prepped track first. ......... on crappy streetcar TnT nights a slick is gonna work better anyway.

Needs the compression tightened up in the front and rear in my opinion.

Plus on a slick prepared track usually the starting line is good and then it falls off quickly after that.

yellowhorse7 wrote:start by slowing the front end down


****Edit I see you tried this. Is the front end tied down or at least limited?

yellowhorse7 wrote:Looking at the slow motion deal.....have you tried slowing the extension in the back? What did you ever come up with for the IC length? Radial cars usually like shorter IC's.

whatbumper wrote:Needs the compression tightened up in the front and rear in my opinion.

Plus on a slick prepared track usually the starting line is good and then it falls off quickly after that.

I never got a "fair" hit after tightening up the front struts because the track was gone. Testing again Friday on the same track. I think if I can get it working decent on this track, it will be just fine on a radial track. I know the strange front struts were 3 clicks off full loose. I cant remember where the rear QA1 da's are at as I haven't had to adjust them in a long time but I'll check and post. I'll also check where my ic is at the moment and post as well. Once I post that info, maybe you guys can point me in the right direction of things to try this weekend. Thanks

After watching the videos more I think you need to shorten the IC too.

whatbumper wrote:After watching the videos more I think you need to shorten the IC too.

X2

Ok fellas, according to my measurements and using the calculator on the sticky above, my IC is 36.75". My IC height is 8.75". My AS value is 133%. My LCA is pointing 2* downward. I have no brackets currently installed to change control arm or ride height postion. The QA1's are currently set at 9 clicks on compression and 3 clicks on rebound. As you see from the video it is pretty close to being acceptable considering the track we are testing on and considering I dont have a lot of time to be drastic because of an upcoming race. I'm testing Friday and probaly Sat. I would like to know yalls opinion on where to start the first small change and if that dont work where to go to next. I dont want to make more than one change at a time and time is limited. I am thinking of starting with tightening the front struts all the way on the first hit Friday and go from there. I would also like to see some initial wheel speed out of the thing. On the slicks, It liked leaving on the brake at 3500 much better than 4500. Didn't hit the tire so hard. But on the radials with more air, it seems the tire dont care as long as it has something to stick to. I'm thinking with the radials it may want to hit harder like it did at 4500? Converter flashes 6000. Thoughts?

We try to beat the hell out of the tire. Hit it hard.

I have a hard time believing those numbers after watching the videos. what were the numbers you put in?

Keep in mind, I make a touch over 1000hp n/a and the converter flashes at peak torque. I had to drop the car on cap blocks to give me enough room to get under it to get the most accruate measurements I could at ride height. Even then, I have to second guess what I see on the tape before I log it as I noticed from playing with the calculator that small increments make huge differences. That being said, this is what I came up with.... I subtracted 3 1/2" from ground to control arm mount bolt measurements due to the thickness of the cap blocks. LCA front - 9.25" rear - 9.625" LCA length 17.5"   UCA front - 16.25" rear 18.5" length 9". Dropped the car back to the ground to read camshaft height - 18.25"   102" wheel base. Also for shits and giggles, call shifter horizontal center of gravity= 57". Pinion angle -1.5*. I did notice that I typed rear LCA as 9.675" instead of 9.625" so I am going to check the calculator again but I'm guessing that it won't make much difference.

I have been proven wrong. Just that little bit of difference on the LCA rear bolt changed the AS to 155% and IC to 34.5". Maybe I need to find a better way to measure  . Also havent scaled the car since dropping weight out of the doors and the nose. Assuming a 55-45 front to rear bias 1705-1395 @3100lbs. Vs the 57-43 @3250lbs before.

Stop...

As long as that lower control arm is pointing down (meaning the front of it is closer to the ground than the rear of it) it will ALWAYS blow the tires off, it's just a matter of where and when. Get them pitched ever so slightly up and it will be fine. The thing wants to work!

I agree with bumper....them numbers are fishy. If the IC was that short at that height, the arms would be at least level if not up.

Stop measuring. These programs can get tricky if not all measured the same way.

Get the car at race weight and have someone take a photo that clearly shows a side view of the rear LCA . The entire profile from far enough out that shows depth and parallels (like to the ground)

yellowhorse7 wrote:Stop measuring. These programs can get tricky if not all measured the same way.

Get the car at race weight and have someone take a photo that clearly shows a side view of the rear LCA . The entire profile from far enough out that shows depth and parallels (like to the ground)

The car does sit quite a bit lower in the front due to a 19.5" rear shock and no adjustable mounting locations.

Tested again tonight. I tightened up the front struts all the way and installed the travel limiters to give around 3" of travel. Everything else the same. It got worse.



Pass 2 I raised the 2 step from 3500 to 4500 to hit the tire harder and bumped pressure up to 17.5 due to the vid from the first pass showed the tire wanting to wad. Got even worse.



Pass 3 I set the compression on 12 (was at 9) and the rebound on 0 (was 3) and got even worse. It's starting to pick up some initial wheel speed and begins to hook but unloads.   Testing again tomorrow. The track will be prepped better. Suggestions????

Raise the rear or raise the front or both to get the lower arm level.  Unhook the limiters.  Loosen the extension on front tighten the compression.  Put air pressure were you had best results.  Make a hit.

If you want to run the car really low then you will need an adjustable lower mounting position.

whatbumper wrote:Raise the rear or raise the front or both to get the lower arm level.  Unhook the limiters.  Loosen the extension on front tighten the compression.  Put air pressure were you had best results.  Make a hit.

If you want to run the car really low then you will need an adjustable lower mounting position.

Boom. X1000

Long story short, put in 8 hits this weekend I think but got a decent one in. Went back to the slick set up, took the travel limiters back off, and dropped down to 16 psi. A lot of slick tire cars were complaining about the track prep. Seems everybody was having trouble with the track, even the 7.50 cars. Maybe we are not as far from it as I thought...

Watch your front tire once the car comes back down I played the video fullscreen couple times to make sure I was seeing it right about 9 seconds into the video.

backhalf it and put tank tracks on.........

richter69 wrote:backhalf it and put tank tracks on.........

Why

looks like the front tires are shimming when the front sets back down and that could be cause the car to wobble just enough to make the rear brake loose in the last vid

69F100 wrote:looks like the front tires are shimming when the front sets back down and that could be cause the car to wobble just enough to make the rear brake loose in the last vid

The car has done that since day one. I have no idea why. I thought it was due to play in the lower control arm that I shimmed out but still does it. There is no slop anywhere other than from the rack to the steering wheel in the aftermarket column and removable steering wheel hub but still don't understand why it does that on its on. It's not me doing it  

soupbean wrote:

69F100 wrote:looks like the front tires are shimming when the front sets back down and that could be cause the car to wobble just enough to make the rear brake loose in the last vid

The car has done that since day one. I have no idea why. I thought it was due to play in the lower control arm that I shimmed out but still does it. There is no slop anywhere other than from the rack to the steering wheel in the aftermarket column and removable steering wheel hub but still don't understand why it does that on its on. It's not me doing it  

What degree do you have the struts my buddy when he built the rx7 with the 557bbf we had to lean his struts back his was doing it some when it would touch back down