Hope they work out for you! Thanks for sharing the info.

2BKING

Well race day was interesting. 1st pass nearly took out the tree jumping hard left at the hit wheels up. Tightened struts and 2nd hit still went left but driveable some tire spin wobble is back. Took a little weight off the right rear with antiroll, loosened front a little made a decent pass still wobbled. 4th pass spun and wobbled bad. Now time for 1st rnd so I pulled a little timing, loosened the shocks and struts back to original setting on struts and the car decided to work again. Ran off a string of 6 or 7 5.03's (if ran clear out). 4 straight passes 1.130 60' and then a 1.22 with the rears. It seems like if the front tires are 6" off the ground or more for at least 40' the car is friggin deadly and doesn't wobble. If the front tires don't come enough it wants to wobble. I'm thinking it may need even more anti-squat to shove the tire down.

Glad you are making progress with the radials.
So does the wobble start after it sets the front end down? Is there any chance it could be something up front?
What tires are you using for fronts? I don't know if it is still an issue with modern radial slicks, but way back when radials first came out, there was a lot of guys saying you had to go with radial fronts as well, or it could lead to an unstable ride down track.

Just curious, what is your end goal with the PBR over a bias ply slick to make all this trouble worth it?

I may be old and sometimes narrow minded, but I have always been a firm believer in don't try and fix something that isn't broke

FBJ I’ve read that same thing from classracers who were running radials.

quote:

Originally posted by FootbrakeJim:
Glad you are making progress with the radials.
So does the wobble start after it sets the front end down? Is there any chance it could be something up front?
What tires are you using for fronts? I don't know if it is still an issue with modern radial slicks, but way back when radials first came out, there was a lot of guys saying you had to go with radial fronts as well, or it could lead to an unstable ride down track.

We have been using radial rear tires for 10+ years. Up until last year we ran bias ply front runners & never an issue! I do like the radial front runners but don't like the price.

2BKING

quote:

Originally posted by Big Steve:
Just curious, what is your end goal with the PBR over a bias ply slick to make all this trouble worth it?

I may be old and sometimes narrow minded, but I have always been a firm believer in don't try and fix something that isn't broke

For us it was almost a seamless transition to radials many moons ago. We started with a lightweight Hoosier 30x9 that wasn't supposed to work for bracket racing according to Hoosier & other so-called experts. I won some pretty good money on them radials & put 150 runs on them.

I was skeptical when I did the switch. It's not easy running a small tire 3,000+ lb. car; the main reason was sidewall life of a bias slick. 50-75 passes & sidewalls were gone: even when using stiff sidewalls & tubes. The radials solved that issue & I have put 200 runs on a radial without issue. We change them out just because of feeling guilty.

Now, to present day with a ProCharged mid 5 1/8th & mid 8 1/4-mile sbc. I have around 150 passes on my current set of radials & still going strong. The car works very good on them & little to no drama going down the track.

Seems like the majority of issues are with the bigger sized radials. Some have issues of spinning the small radials but feel like there set-up wasn't right.

My radial experience isn't perfect but they're significantly better than a bias ply tire in the big picture of things! That's my opinion for our racing program.

2BKING

This message has been edited. Last edited by: B KING,

They are MT bias fronts, Mt told me it wouldn't be an issue. I asked them because I remember hearing this same thing in the past. The wobble starts 100-150' out. No idea why but if it has any spike in driveshaft graph in the 1st 100' or so it wants to wobble down track.

quote:

Originally posted by FootbrakeJim:
Glad you are making progress with the radials.
So does the wobble start after it sets the front end down? Is there any chance it could be something up front?
What tires are you using for fronts? I don't know if it is still an issue with modern radial slicks, but way back when radials first came out, there was a lot of guys saying you had to go with radial fronts as well, or it could lead to an unstable ride down track.

This message has been edited. Last edited by: inferno camaro,

Being more consistent is my end goal. I really like the fact the radial will not shake because it is dead hooked and not trying to manage wheel speed. So far if I keep the front tires up 5-6" or more the car is nasty good. If I keep the tires down where I would like them it will slip slightly and seems to make the car wobble and loses consistency. So far it seems to like shorter higher instant center so I'm going to keep going that direction until it doesn't work.
ET wise I would say no noticeable difference from bias tire. I think the bias is a little quicker to the 60' (I assume because of wheel speed) and radial is quicker down track so ends up very similar.

quote:

Originally posted by Big Steve:
Just curious, what is your end goal with the PBR over a bias ply slick to make all this trouble worth it?

I may be old and sometimes narrow minded, but I have always been a firm believer in don't try and fix something that isn't broke

This message has been edited. Last edited by: inferno camaro,

quote:

Originally posted by inferno camaro: So far it seems to like shorter higher instant center so I'm going to keep going that direction until it doesn't work.

How much does the rear separate now during launch?

That is the really odd part, it still doesn't separate. It still looks neutral at the hit. Honestly doesn't look any different than when it was set at 100%
I have a ton of videos but not sure how to post them on here.

quote:

Originally posted by markemark:

quote:

Originally posted by inferno camaro: So far it seems to like shorter higher instant center so I'm going to keep going that direction until it doesn't work.

How much does the rear separate now during launch?

quote:

Originally posted by Big Steve:
Just curious, what is your end goal with the PBR over a bias ply slick to make all this trouble worth it?

I may be old and sometimes narrow minded, but I have always been a firm believer in don't try and fix something that isn't broke

Every car I've been around that made the switch has become noticeably better on radials with no other changes made. If they don't wobble, which has only been one of them.

I believe a travel sensor provides a more accurate sample of where the body is moving to at launch and during the run. For me, when moving the AS from 69% to 102% to 126% present, the graph showed more than a video. Consider adding one if possible as you continue to pursue making radials work.

I actually do have sensors on it. I put them on it about 2 months ago. I'm just not sure I trust them. Never show the shocks hardly ever move. It shows the shocks do nothing at the hit and actually compress about .5" at the top of 1st gear and goes back to neutral or slightly above in high gear.

quote:

Originally posted by inferno camaro: I actually do have sensors on it. I put them on it about 2 months ago. I'm just not sure I trust them. Never show the shocks hardly ever move.

If you can disconnect the rod mounting and run the entire stroke out/in and see it displaying correctly in your DA device I’d call it correct.

They are rotary switches and I had to enter a number at static ride height then compress the rear and enter a voltage # and measurement and do the same extended so it should be correct. Just seems like the shocks should move more than they do.

^^^^^^Does the DA display actual inches of travel?

supposed to.

In inches, how much is the total shock movement during the run? When you change the AS does it reflect in the DA shock travel position during the run?

With 126% AS my total shock travel during run is now 0.90, 0.82 of it above the shock position on starting line. But my car leaves wheels down.

At the hit it stays level @ .6 seconds in it starts to compress slightly. It will compress .3" through low gear in high gear it ends up .2" above start point. So 1/2" total travel.