812MANY

I need new rear tires BAD!

I've got major traction problems (BFG Comp T/A) and I've wiped out both of my rear tires in the last 2 months.

Every time I try to merge in traffic while turning right the inside tire goes up in smoke, even if I try to pedal it.

Drivers aren't very polite around here so if I wait until I can pull out like a grandma I end up sitting there for a good 20 minutes!

I'm looking into getting a set of BFG DRs next week, will they help?

I've got an 8.8 locker in my garage, but it will be at least 6-8 months before I get it built up and installed.

I need a quick fix NOW!

Thanks,
JK

EDIT: what's the widest tire I can fit on my POS 15X7" rims? I was thinking about a 235/60, but my bud said he squeezed a set of 275/50s on his 89 RS.

I've got a GOOD air hammer



[This message has been edited by 812MANY (edited September 05, 2001).]

Norm Peterson

Save the DR's for the strip. They are a specialized tire for a particular use and normal street duty isn't it.

BFG lists a treadwear rating of 00 for their DR's (you might get 2 weeks given your existing treadwear problem), a "B" rating for traction (true that this is straight-line wet braking traction, but Fla. does get wet occasionally), and "C" for temperature (the poorest rating, and with all the recent publicity over tread separation . . .). Any "C" rating is enough all by itself for me to strongly discourage purchase for normal use (actually, I'm not all that comfortable with "B" ratings for any kind of performance car use).

There are a few things you can do to reduce that right rear wheel spin, though, and they aren't very expensive and don't take much time to do.

Put an air bag in the right rear spring to preload the RR tire.

Move whatever lives in your trunk to the right side, again to add weight over the RR.

Replace your front antiroll bar endlinks and a-r bar frame bracket bushings with poly bushing parts (this will reduce lateral weight transfer at the rear which means that the RR will not unload as much in a right turn). Leave your rear antiroll bar alone (you don't want to stiffen the effect of that one until you've upgraded that differential).

And you can modify how you approach an intersection from a sideroad. Try coming to your stop at an angle rather than straight on. That lets you use a much wider arc as you merge (which is another method of unloading the RR less).

235/60 is absolutely as wide as I'd agree to on a 7" wide rim. Tire width on stock wheels was a hot topic on another bb. In a nutshell, mounting tires on too narrow of a rim can overstress the cord structure of the tire and you ultimately run a higher risk of tire failure. For a range of rim widths that are acceptable for each tire size, go to www.tirerack.com, click on "Tires" and go to the Specs of whatever tire you're thinking about. A range of acceptable rim widths for each available size is given along with other dimensional info.

Here's what Tire Rack had to say about BFG DR's on the street (so you don't have to just take my word for it and feel that I'm just bashing BFG)

The Comp T/A Drag Radial is a special use product designed for competitive drag racing applications. As such, the following precautions must be followed when using the product.

ON THE STREET:
These tires have a reduced tread depth when new and a tread rubber compound optimized for straight line grip. As such, they will wear out much sooner and offer less wet grip when compared to normal passenger car tires. Therefore:

Observe tire wear condition often.
Do not use the tires on the street when the tread depth wears to less than 2/32nds inch.
Reduce speeds in wet conditions and whenever any standing water is present

Norm

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1979 Malibu w/some cornering tweaks and a few other interesting things

[This message has been edited by Norm Peterson (edited September 06, 2001).]

RB83L69

I'd suggest fixing the traction problem first... try a set of LCA lowering brackets. My motor puts 213 HP and 282 ft-lbs to the wheels, and I practically can't spin them at all with the brackets on there, the tires just dig in.

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"So many Mustangs, so little time..."
ICON Motorsports

812MANY

Thanks Norm,

I only drive about 12-15 miles a day, so tread wear isn't really an issue for me (when they stick).

I know several people running DRs on their daily drivers without a problem. They actually wear pretty well.

I usually enter an intersection at an angle already- 1 because my car is low and bottoms out if there is a dip, and 2 because I don't have power steering right now (popeye arms) and its a real PITA to make a 90* turn.

Rain traction is nonexistent on the shifts even when I had brand new full depth BFG Comp T/A HR4s on it. Obviously it has gotten worse lately.

I guess LCA lowering brackets would be a good idea (I know I scrwewd the geometry when I dropped the car). It will give me an idea of how to fab the brackets for the 8.8.

Since I need new tires anyway, what would you sugguest?

I would like to cheap out and get a set of BFGs and keep the front tires, but if there is something better and not TOO expensive I'll change all 4.


Thanks
JK

AlkyIROC

As mentioned above, get some rear air bags or at least one in the RR spring. Since they come as a set you might as well use both. When properly set up they can make even an open diff hook up like a posi.

I use air bags in the rear springs of my drag car. I run 5 psi in the drivers side and 15 psi in the passenger side.

Because of how the gears work in the rear diff, when you accellerate, the ring gear tries to push out the rear of the diff. The rotational forces also push down on the driver side wheel and lift the passenger side. That's why relocated batteries are always over the RR wheel to add weight to that side. Putting a stiffer spring rate spring on that side will also help keep the wheel planted. It'll take more energy to try and force the wheel up. A combination of a stiffer spring, air bags and a rear sway bar should help keep that wheel on the ground.

The LCA relocation brackets will be needed since the car has been lowered but they won't do anything from keeping that wheel from lifting and spinning like you mentioned. They'll just reduce the amount of wheel hop during straight line accelleration.

I use Comp TA's on my truck with no problems at all. The diff is only a GM Eaton gov-lock with 4.10 gears. I've even used them at the track with tire spin only when the track isn't prepped.

------------------
Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

Best ET on a time slip: 11.242 altitude corrected to 10.89
Best MPH on a time slip: 121.52 altitude corrected to 125.89
Altitude corrected rear wheel HP: 497.9
Best 60 foot: 1.546

Racing at 3500 feet elevation with a typical race day over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

Norm Peterson

LCA relocation brackets should help (for some reason I thought that you might already have them; that's why I didn't mention them). While it's true that they don't reduce the lift on that RR due to axle torque reaction noted by Stephen (that's a separate effect), they will add some anti-squat. This plants the tires harder whether you're going straight or turning (or at least reduces how badly they lift and how much traction you lose as the chassis squats if you've REALLY slammed the ride height).

I have had BFG Comp T/A ZR's (225/60-15, ~$100 each, 220 treadwear) and Dunlop SP8000's (225/60-15, 200 treadwear, about the same $ but I don't see that size at www.tirerack.com any more, then 245/50-15, 200, $more) on the Malibu in my sig (15 x 8-1/2 wheels). Before I replaced my almost-not-posi-at-all GM posi with an Auburn unit I couldn't keep that RR from spinning any of those tires either even with the band-aid solutions I mentioned previously. I just didn't spin them as badly as before and it was easier to regain the grip.

Norm

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1979 Malibu w/some cornering tweaks and a few other interesting things

[This message has been edited by Norm Peterson (edited September 07, 2001).]