:help:

Hello all,

I just put an RCD 6" lift with new BFG 35s on and the first thing I noticed was that that speedo was way off (about 9 mph at 50). Now I see that this has been covered all over the place, but I am a bit confused about how to proceed.

First, I understand that the ECM has 2 tire size parameters that can be set - one for the ABS and a second one that is used to calibrate the speedo and adjust timing, shift points, etc.

It seems that with the Flash type programmers (Predator, Hypertech, etc.) I can set the correct tire size for the ECM, but I'm unclear if it also sets the tire size parameter for the ABS?

Also, I'm considering putting in an Edge Juice/Attitude (I like the idea of having the guages and controls in one unit). There is a tire size setting in this device as well, but setting it will not program either parameter in the ECM? Correct?

Superlift make a doodad (TruSpeed) that can calibrate the speedo and presumably correct the issues with the ECM, but does it also handle the ABS setting?

The BIG question - If I buy a programmer (like the Hypertech) and use it to set the tire size in the ECM, and I install the Edge Juice/Attitude combo, what pray tell, would I set the wheel size to in on the Edge Juice/Attitude?

OR

Does is make more sense to use the Superlift TruSpeed the Edge/Juice together, but the question remains - what would I set the tire size to on the Edge Juice/Attitude?

I am really confused. Worse, I called Edge yesterday and asked these questions and the guy didn't have a clue what I was talking about!

Been there, asked that. I was wondering the same stuff after my RCD 6" lift and
315's. Did a search but could not find much on the ABS.

ABS - Asked the dealer to re-calibrate the ABS a couple of days ago. Service writer daid he talked to service manager about it. He gave me some vague answer about them not being able to. Tried to find out if that meant they would not do it or just didn't have what they needed to do it. I think it was that they just didn't have wha they needed to do it. Was told by Max Payne on a thread I posted that the ABS does not need to be recalibrated and based on what he told me an how the truck is performing I believe this to be the case.

Speedo - Asked the dealer about this as well and also got some vague answer as to them not being able to do it. Didn't try to find out because I am getting the Predator and that will fix it. If you run the Predator with the tire size correction your speedo will be correct. If you run the Edge alone, your speed will not be correct on the speedo but the tire size enter in the Edge will display the correct speed on the Attitude. Of course, you could always get both and stack them. If you get both just set the correct tire size in both.

Also, if you are looking for accuracy, measure your tires to get the correct height.
35's are not always 35 inches.

Mark

Setting the tire size in the ECM only affects the speedo. It has no effect on the ABS.

I adjusted for tire size with my Predator programmer for my 35's. I actually called Diablo and they gave me the conversion size to enter into the programmer. I put it in and no problems with speedo or ABS. I checked the Speedo with my hand held GPS and it's accurate to 1-2 mph and my ABS works(I have unfortunately had to test it once or twice on the freeway), I will say that with larger tire and wheel combos the ABS is less effective because the distance the wheel travels in between brake pulses when the ABS is attivated, is longer because of the larger diameter, so teh vehicle actually travels farther thus making the ABS less effective. To accurately compensate for the larger tires the high speed motor that controls the pulses would have to be modified and I don't think this is a viable option. Just my $.02,

Chris

I adjusted my speedo with the predator. My abs appears to function properly.

You should post some pics of your truck, looks good in the little avatar picture.

Well, I ordered a Predator yesterday after reading your responses. It seems like it is the most cost effective solution and I have decided that I really not need the ability to change tunings on the fly - I'm not racing the thing!

Question for _nar_: Did you have any issues with the Predator on your 04 lly? I read somewhere that I might need to have the PCM reflashed before I use the tuner.

I also ordered a set of Westin Platinum step bars per my wife's request ... not to mention the fact that I almost broke my ankle getting out of beast yesterday! When I get them put on, I'll post some pics. Hard to keep a black truck looking clean though. ;-)

My predator has worked fine on my truck, and my truck has never been reflashed by the dealer. Built 6-04...

The predator is a good choice...you will not regret it. I have them all and its definitely the best bang for the buck. Truck looks sweet by the way!:ro)

Update and a question:

OK, by some freak of nature, I received the Predator yesterday afternoon (paid for Saturday delivery). Went through the procedures and loaded the "Std" 65hp tune, modified the tire size parameters to 315/75/16.

Took it out with GPS and noticed a couple of things. First, the tranny shifts are a little rough, but I understand it needs to re-learn, no problem. Second, when I got on it, she took off like a scalded ape - nice! BUT, the speedo is still off by what appears to be about 8 to 9 mph @ 60. It doesn't appear to have had any difference on the speedometer. Also, I noticed that I had to enter the wheel size info twice - is that normal? I guess I'll be calling Diablo on Monday.

Comments, suggestions and rude remarks are all welcome.

I bet I know what you did.....the first tire screen that comes up is what size tires and wheels came on the truck STOCK.The next tire screen asks for ACTUAL tire and wheel size. I screwed this up once before...try it and see what happens.

I bet I know what you did.....the first tire screen that comes up is what size tires and wheels came on the truck STOCK.The next tire screen asks for ACTUAL tire and wheel size. I screwed this up once before...try it and see what happens.

:exactly: I think there are quite a few members that did the same thing...some of us more than once :o:

DPower,

Your suggestion worked like a charm - reapplied the tune with the modified parameters and took her out with the GPS. Dead on. You would think that the instructions and the prompts on the Predator would be a little more descriptive. Well, maybe with the next version...

Thanks everyone for your help.