[kwik66]

I though this my be better posted in performance. I am know running E.T. Streets on the back and M/T front tires on 4" rims up front.I would like to put on a new set of M/T drag radials and keep the bias tires up front. They are like new. Has anybody ran this setup or is it unsafe. I will change the front tires if it is a saftey issue. The car sees street driving and 1/4 mile runs

Thanks
kwik66

 

[Bob West]

I think you'll be fine. I've run radials up front and bias at the rear, as long as both fronts are bias and both rears are radial or vice versa, you'll be okay.

 

[BillsCamino]

Bob's right.
I run Hoosier radial slicks with Hoosier bias skinnies up front...absolutely no issues, actually very stable at the top end.

 

[Harold Sutton]

I think you'll be fine. I've run radials up front and bias at the rear, as long as both fronts are bias and both rears are radial or vice versa, you'll be okay.

I was told a while back that keeping it in a straight line is a matter of the correct front end alignment. My son's nitrous car didn't like the mixing of radials and bias ply tires one bit. It went all over the track at Tulsa when he tried it. I don't remember what the trick is (it seems like a guy told me it's the camber setting) but be sure to have it aligned by someone who knows, don't just throw them on. My son's car got so out of shape that he destroyed the tires. They got into the fenderwells and big chunks of the sidewalls, where the tread starts were gone when he took them off. He also stated that skating around at 140 MPH wasn't fun.

 

[kwik66]

Thanks Bob and Bill, I think I will give them a try.( next spring,I HATE SNOW)

Harold, my car isn't a high H.P. car like your sons, just run in the mid elevens,so maybe they will work for me. Good point on allignment though

Thanks guys
kwik66

 

[BillsCamino]

I don't remember what the trick is (it seems like a guy told me it's the camber setting) but be sure to have it aligned by someone who knows, don't just throw them on.

To assist in keeping the car in a straight line... during a wheel alignment, you'll want as much positive caster as possible.
I'm able to get +5.5 degrees with the Global West control arms.

If you draw an imaginary line thru the center of both the upper and lower ball joints, then view that line from the side of the car, positive caster would have that line tilted forward.
Now think of that same line as viewed from directly in front of the car...the angle of the line is camber.

 

[Motor Martyr]

I was told a while back that keeping it in a straight line is a matter of the correct front end alignment. My son's nitrous car didn't like the mixing of radials and bias ply tires one bit. It went all over the track at Tulsa when he tried it. I don't remember what the trick is (it seems like a guy told me it's the camber setting) but be sure to have it aligned by someone who knows, don't just throw them on. My son's car got so out of shape that he destroyed the tires. They got into the fenderwells and big chunks of the sidewalls, where the tread starts were gone when he took them off. He also stated that skating around at 140 MPH wasn't fun.

Harold, more then likely that fiasco was due to the lack of caster in the front end.

My specification when having my car aligned was as much caster as possible. Ended up being something like 2.5 degrees.

One of the cars i work on has so much positive caster that it will pull the steering wheel out of your hands when turning a tight corner.

 

[Rowdy]

Maybe this is a difference in terminology, I just want to clarify, as my interpretation of Bill's explaination initially seems opposite. If "tilting" forward is the same as sloping forward (downward) O.K...Positive caster has the upper balljoint behind the lower, the imaginary line would tilt back at the top.

Theoretically, the camber definition is correct, but the imaginary line can not be considered as 0 degrees. The spindle actually locates the upper ball joint further inward than the lower. The hub at zero would have the imaginary line displaying negative camber. The geometry difference is engineered as steering axis inclination, a completely seperate measurement and normally not a consideration during your common alignment. It is the factory method of minimalizing things like bump steer through a variety of possible chassis ride heights and alignment specifications (usually within the min/max recommendations i.e. Camber: -2* to +2*).

As a rule, a vehicle will pull in the direction of the front wheel displaying the most camber (+) and/or the wheel displaying the least caster (-). + Camber seems to pull harder, while - caster (in reasonable values) kinda drifts. Unorthodox combinations of these characteritics (and others) are what makes roundy round race cars stick like slot cars in the turns. The shorter the track the more you want the car to turn itself left, obviously longer tracks, have longer straightaways and "looser" turns. Likewise, less "lefthand favoritism" is desired of the alignment.

Of course, there is alot more to it, I didn't even address the rearend, but you should get the idea. Street cars usually favor the left (within a degree) to compensate for road crown.

Rowdy

 

[BillsCamino]

Maybe this is a difference in terminology, I just want to clarify, as my interpretation of Bill's explaination initially seems opposite. If "tilting" forward is the same as sloping forward (downward) O.K...Positive caster has the upper balljoint behind the lower, the imaginary line would tilt back at the top.

Thanks for clearing this up, Rowdy. :thumbsup:
That is exactly what I was trying to convey. Re-reading my post, I can see the confusion.
The picture below shows positive caster...

And while I'm at it, I'll do camber too.

 

[Harold Sutton]

I really don't know which alignment problem exists but the results was a car with about 950+ RWHP walking all over the track on a set of BFG Drag Radials which are no longer usable. This car handles pretty good with bias ply slicks on the rear and bias ply skinnies on the front. Maybe we'll try it again one of these days if we get the front end right.

 

[mild68ss]

It's been a while since I took a class in steering , alignment and suspension.
I recall to remember positive and negitive caster or camber is, if the line from center is towards the front (from side view) or center (front view)of the car it is negitive.
Or if the line points towards the NUMBERS on the licence plates or tags it's Negitive.