XR4Ti Archived Tech Articles
Post Date: Tue, 27 Mar 2001 Subject: Re: Drag Radials List: firstname.lastname@example.org Chad wrote: > last year i ran 245/50 15 kumho > auto cross tires (they were free) I don't believe any DOT approved autocross tire would be worth using in a drag race situation, compared to a tire designed with drag racing in mind. I know my "racer" XR will melt BFG R1's in 2nd gear (coming out of a turn), and traction was always a joke in a straight line in first gear. The car is only putting out about 220hp, if that. I've always been amazed at how R-compound autocross tires don't hook up as much as you think they would. I was concerned I'd be replacing my 5-year old Motorsport clutch as soon as I bolted on the R1's last year. Well, I suspect they'll live through this season of the Kumhos too. As I recall, this thread started with Tim asking about what else he could do to hook his car up. Maybe it was someone else. Anyway, I'll add my $0.00. Get an LSD. We've discovered how cheap it is to get a viscous LSD from a Sierra XR4x4 out of England. I'm going to be installing mine this coming weekend if all goes well. You can see my write-up to date in the install progress at my "Archived Tech Articles" page. Also, I don't think I've ever heard mention of it among the XR drag racing crowd, but do NOT forget about the importance of a rear alignment. Rear camber especially, and toe somewhat, have a HUGE effect on straight line traction. Maybe this has been talked about and I just wasn't paying attention. My "racer" had a standard-lowered-XR rear negative camber of about -2.75°. In a straight line, with street tires I could bark 3rd gear on command and smoke them as hard as I wanted going into 2nd. I reset my rear camber to about -0.75° and I could no longer get any tire noise out of 3rd gear and the car prefered to hook up much faster going into 2nd. Shim the rear suspension until you get the desired camber. There is another "Archived Tech Article" on rear suspension shimming as well. I'd suspect that the really hardcore XR drag racers could benefit from even a tad bit of positive camber at the rear tires (I can't believe I just typed that) When the XR is launching, accelerating, the rear suspension squats, increasing negative camber (I'm sure most of you know this, just covering this for clarity). This reduces available traction. If the tires are vertical, you'll get better traction. This holds even more true on wider tires. Slightly positive camber would turn to zero camber or maybe less negative camber when traction counts the most. Finally, I'm not a pro or even a regular drag racer. There may be better info, but I think I'm barking up the right tree.Back to the Tech Articles main page
Published by Chris Anglin.