hisvett

After the last DE event, I noticed an unusual step on the outer edge of both front tires. Is this normal or too low or high PSI???

I'm running Viper Scrubs, Hoosier "R" 305X18's at 36 to 38 PSI with 1 1/2 degrees camber. Any ideas


Both fronts have the save step on the outer edge.


Other tire.


Inside edge looks normal.

fatbillybob

Who are you getting those scrubs from. I could use some. Are you running 305's on all 4 corners with z06rear wheels?

Looks like that line is caused by the fender rubbing on the tire in compression on hard corners or you are rubbing soemthing inside the fender wheel upon turning and compressing that corner

also are those grand am slicks? if so are they 305 680 18? Those could be too tall and rub. OK for back but not front? need more of a 645 front

TedDBere

My guess would be your 305s on the front are rubbing. You may be too low with your springs not strong enough to keep the fender off the tire.

I run 295s up front and this picture is at a roll, not much room for a taller, wider tire:



The old 305s are what Hoosier now calls their 315s BTW.

emf

Yup -- looks like you're rubbing on the fender lining. Look for wear on the edges of the lining if you're running a wide offset, middle of the linings if you're not. The bolts holding the lining are usually culprits, but it doesn't look like that's it from the pics.

hisvett

No touchie/feelie by the fenders, I have enough track photos to prove that (not to mention no paint missing). Plus the ware seems to be even on Left & Right side. The track had 2 medium & 1 slow Left handers but 3 major fast high "G" Rights.




The tires are 305-30X18's & I have to find a new suppler myself. Grand Am tire are much harder because they have to last for the full race. I'm on my 3ed set of fronts and they seem to stick better than most. I was getting them from Bobby Archer but he's currently out of business.

hisvett

I have to agree, it does look like fender rub. I just went out and looked again at the underside/inner lip for missing paint.........this is what it looks like...

I see no paint missing or rubber coating and as soft as Vette paint is, I can't believe it could hold up against rubber tire contact. Maybe Bowling Green used some super tuff paint on the inner-fenders lips

fatbillybob

What wheel are you running? If you are not rubbing as a WAG could it be that you are not really using the entire tread? The inside does not look worn all the way to the shoulder. Could it be that on the outside 90% of your turns wear the scribed line as shown then only 10% run up to the shoulder where the wear should be. You could test this by marking with tire marker and see where you are scrubing off the marker vs how much G's you are loading the tire. Are you getting even tire temps in the 175-230 degree range. Is the wheel too narrow and pinching up the tire center? For example a Z06 rear wheel is 10.5 and a 315 is kinda big I would think if the old 305 is really a 315.

emf

That's not where I'd expect it to rub -- look on the front and rear of the wheel wells for shiny spots -- depending on the wheel's offset, it's either rubbing on the fender lining on the far outside of the wheel well, or towards the middle. On mine, it rubbed on the rear until I clearanced the wheel well.


Check the heads of the screws holding the liner on for shiny spots -- that should give you an approximate clue where it's rubbing on the fender lining.

*edit* To clarify, it doesn't look like it's rubbing under full compression / load, but rather on the inside of the fender lining when the wheel is being turned.

RAFTRACER

If those are 305's they are yester-years Hoosiers (R3S05 or R3S04) which have been known to have some sidewall reliability issues. Not as bad as the A compound ones though. Those vintage Hoosiers benefit from 2.5+ negative camber in the front and air pressures hot upwards of 40 psi.
If the wear is caused by fender contact , obviously none of this will help. It doesnt look like there is a devit circumfrentially where the sidewall meets the tread.......yet. This is the area to pay the utmost attention to, and left un-monitored you will go to cord quickly, thats why the A6 and R6 where developed.
Grip is good on those tires, just keep an eye on them , rotate , and flip as necessary and keep enough pressure in them.

hisvett

I think you maybe on to something; I will check this out later today.

One other thing noted after removing the wheel was that the shock was not centered between the two upper "A" arms. It's like this on both sides of the car, almost touching the rear arm. Maybe Raftracer can shed some light on this; and thanks Danny, for the tip on the tires. I know 2 1/2 degrees is what I should be at but I still, on occasion, will do a club run on the street so we settle for a not so happy medium setting.

If the shock should be centered, then my bushings are giving up and need to be replaced. This could account for the centerline of the wheel moving to the front and perhaps making contact with the rear inner-fender on hard turns. Not sure why the centerline would move forward rather than backwards maybe someone smarter can answer this.

Thanks for the help and Happy New Years!