Stiff sidewall slicks

[Anonymous]

Anyone used these over the softer compound slicks?

Got a few issues @ the moment regards stability down track , could be the weight of car causing the slicks to move around on the sidewalls or could just be the suspension not set up properly , gonna fiddle with the caltrac preload & ranchero shock adjustments , also got some different front shocks to try out (90/10s) , but i still think it's the sidewalls giving me the problems , just can't keep on it down track without having to lift off the throttle thinking it's gonna hit the wall or something , don't think it's the nitrous as this comes in off the line , problems start around mid track , any thoughts , gonna try a set of Hoosier stiffwalls & see how it goes , can't be any worse than what i got , maybe it is the weight on the but i can't be sure , car weighs slightly more than the average B body.

TIA.

[Anonymous]

Only gets out of shape when on the nitrous , tried different tyre pressures with no effect on stability , seems more stable @ 16psi ,which is too much pressure i think , is'nt helping much for the 60fts.

[Ashley]

Adam, just a thought, but have you tried running the car with your road tyres but with less pressure in them see if the car wants to lane change still ?

If it did at least you would know it was suspension setup and not the slicks.

[Anonymous]

Good thinkin , but i think the tyres would get blown away on the nitrous , maybe it's that little bit more MPH on the nitrous runs that's causing the problems , thing is i gotta change a few things before next meet , so hoping it's gotta be one of them.

This has been a problem since the motor hit mid elevens & it's gettin worse the faster it goes , just stuck with the ET till i can sort this out , no point tryin to get brave if the motors gonna go tits up.

Alan has the same issues as me but slightly worse (same setup)

[andyrob]

Adam, just a thought, but have you tried running the car with your road tyres but with less pressure in them see if the car wants to lane change still ?

If it did at least you would know it was suspension setup and not the slicks.

good idea ash
adam just make sure you change one thing @ a time then run the car, otherwise if you fiddle with loads & cure it you wont know what was the cause

[Ashley]

What pressure you running ?
Have you tried uping the pressure ?

[Anonymous]

Andy , you're right i should only change one thing @ a time , but track time is so limited i get impatient , not the way to do things i know.

Ashley , tried the tyres @ 18psi & stability was pretty good , although 60 fts were Bananarama!.

[Mick]

Adam
Do you run tubes.

[Cannonball]

my chally was gettin outa shape in 2nd gear on the 9.4 runs went straight when i shifted in to top reckon that was down to the springs, not the tires and tigg reckons they weigh 3,900 not far shy off yer charger adam,

[Anonymous]

Might help with tubes but never ran them as i could'nt drill the rims for the screws with the wheels i was using.

I think the stiff wall slicks are for heavy cars , also for cars with good suspension , there must be a reason they manufacture them , you're probably right dunc it may be a suspension problem , but if i get hold of some stiff walls then i can eliminate the tyres being the problem , gotta get new slicks anyhow as mine are shagged.

Somee of the heavy cars inthe states are running the caltracs with preload backed off & shocks set to minimum rebound , they say the car is pretty unstable otherwise , gonna back the preload off & fiddle with the shock settings & see what happens.
Done a few to many runs to think this is the normal way the car should behave , gotta be something amiss somewhere.

The only other thing i can think is the gas comes in full chat @ 6000rpm (my mistake & did'nt realise till the other day), before this the controller gives it only 50 % , maybe when it gets a full shot this is when it gets unstable.

[Dave999]

this might have nout to do with it
but they just built a new corvette supersonic z9xrisatsumafannymagnet or some such which comes with 650+ turbo injected BHP and costs twice the price

report in CA mag this month

and they could not keep the back stable when shifting under load 1 wheel or the other was always bouncing about and it was not stable enough for a production car.

they discoverd that with two identical axle shafts that flexed the same the axle and centre acted as a resonant system. causing 1 wheel to hop then the other as the vibration pinged back and forth through the centre (this would be dependent on torque applied and traction so would not be apparent all the time)

they discovered the solution by accident when experimenting with different diameter half shafts, they were making them thicker to reduce flex

they sent the car out with mis matched shafts...oops

problem gone one side shaft a tad thicker, meant the conditions to cause the resonance were gone. and wheel hop and general instablility was a thing of the past. a necessary move for a production road car i guess

chance of this happening on yours is probably low as it sounds specific to their GM axle but

if you had say a moser half shaft and a strange half shaft to try out............ i think by the nature of two different products their flex characteristics would differ and that risk would be minimal, both say their axles are unbustable

it might just fix it.

you might also find that ware on axle, bearings and centre differs side to side but that would take a while to become apparent

just need to find someone to lend ya one before you spend on tyers

I wrote about a similar thing when Alan had his shimmy....... although i backed down at the time easier to control it rather than fix it?

http://www.moparuk.com/forums/viewtopic ... g&start=15

do you and alan run the same axles and the same shafts??

kill two birds with 1 stone share a new set or swap

Dave

[NaughtyAlan]

Fitted caltracs and strange,inner tubes since then Dave but still have the same problem

Gonna have to go with the idea that the back end is to stiff and letting the preload of with adjusting the shocks as well is going to soften the blow and help it up the top end of the track.

[Nick]

Cal tracs, split leafs and Rancho's (set @ 5). Hoosier stiff side walls @ 14lb. Arrow straight. I think you just need to get used to the fact that these cars do wander a bit from half track.

[Blue]

A bit more caster dialled into the front suspension might cure high speed wandering, certainly worked on my car. It is very difficult to get any caster at all on stock suspension if the car sits at a rake. You normally have to resort to offset A arm bushes or aftermarket adjustable arms to be able to get the camber where you want it and still retain some caster angle. From memory I set mine at 3 degrees, runs straight as a die so far in the low 11's.

[Mick]

When i fitted the Dana I dropped the back down at the same time and the car feels like it's on rails now
Adam
I run tubes but the wheels haven't got any screws in.
Mick