Don't try running small drag radials [Archive] - Dodge Talk Community Forum


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v8440
03-22-2009, 07:13 AM
I went to the track again this last Friday, and I borrowed my buddy's drag radials. He runs them on his '05 rcsb. There's one critical difference between his truck and an '09...traction control. Before installing the tires I measured them, and his were 4" shorter than mine. That's great, right? After all, I need a little more gear.

Yeah. It's great until the computer senses the difference in rpm between the front and the rear tires. SLAM goes the throttle. Of course, I putting the ESP button in (partial) disable works. It turns out, it doesn't work quite well enough for the track. It works well enough for you to not notice anything wrong while driving to the track, but as most of you know, you can't fully disable traction control on a 2wd '09. Read the owner's manual carefully and pay attention to how things are worded and you'll see. I read it wrong the first time and thought I could disable it completely. Not so.

Long story short, I got a helluva launch, and then it pulled the throttle partway shut a bit before the 60 foot mark. It then felt like it opened it up again, but never really felt quite as strong through most of the pass as it does on the stock radials. Then, I got a nasty shock-a couple hundred feet before the finish line it let WAY off-the damn speed limiter! I wasn't actually going 106 of course, but the truck sure thought I was because of the tire height difference. It ran 93.something on that pass, which is way off the normal pace. ET was 14.10. In fact, the pass before that was on the stock tires, and it had just run 96.75 mph, a new best for that truck. I think it was because I had let it cool down for a long time before running it.

So, the moral of the story is, the 09's don't like differences in height between the front tires and the back tires.

adamsredlines
03-22-2009, 08:28 AM
Sounds more like an ABS thing than traction control.
There are some 3rd gens with 4 wheel ABS that are real picky about staggered tire fitment. Most guys who run drag radials also get front tires to match also (same diameter)

v8440
03-22-2009, 08:52 AM
Yeah, but why would ABS come into play when the brakes aren't being touched? The ones with traction control determine wheelspin by comparing front wheel speed to rear wheel speed. My buddy's '05 has ABS but not traction control. Sure enough, he has no problem running different size tires. I'm sure I have some tires around that would be close to if not identical in height to the drag radials, but they're all on 5 on 4 1/2 bolt pattern wheels, since all the rest of my stuff is older mopars.

Not being argumentative, I just don't see how ABS is involved when the brakes aren't being used.

adamsredlines
03-22-2009, 09:05 AM
Thats similar to how the BAS works on the rams. If the front wheels are spinning faster than the back, it thinks the wheel is slipping so it does weird things with the brakes. If you're on a slick surface and apply the brakes, and say two grip and two dont...then they will be turning at different speeds. Thats when the ABS kicks in and does some weird stuff. Its the same for different size tires....I dont think it differentiates between brakes or not, its just reading wheel speed.
It may be a traction control thing, but I've heard of 3rd gens doing the same thing, and they dont have traction control...so I'd lean towards ABS.

v8440
03-22-2009, 09:14 AM
I don't know enough about the traction control systems in these things yet to know for sure-it could be the ABS now that you put it that way. I know that on an '05 magnum r/t I had I was able to completely disable the ABS and traction control by pulling fuse #17. The dashboard lit up like a Christmas tree, but it worked. I bet there's something similar that will work on my truck.

daytona1191
03-24-2009, 01:14 AM
If the fuse trick works its either the fuse in cavity J04 or J05 in the fuse box. J04: BAT-ABS Pump, J05: BAT-ABS Valve. I downloaded the owners manual in PEF format, so if anyone needs one just PM me with an email address and i'll send it as an attachment!
-Josh

v8440
03-24-2009, 05:52 AM
I got to thinking about it, and I don't think a fuse trick will work for traction control. The reason I say that is that with moderate wheelspin, the ecm doesn't seem to use the brakes to control it. It pulls back the throttle opening. Doing that does not require any extra hardware beyond the ecm itself, so there's nothing external (like an abs module) that would have it's own fuse to pull.