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magindat
02-29-2008, 12:30 PM
I just put 245/45/18 KDWNT on the front and 295/45/20 KDWNT on widened 10" rear. They are GREAT! Look HUGE and have dropped my effective gear ratio to 390. They grip well and have, in my opinion, completed the car visually and ride wise.

I have lowered the car over them and they only rub slightly on deep bumps (like after a train track crossing). I am happy with them in every way and from every technical aspect and believe me I explored them all!

However, like with most customization, I missed one thing. ABS. It's a 300A with no TC, so no issue there. I have searched and searched and not found these symptoms.

After turning on a running under 45mph for an unlimited amount of time, no ABS light. After 30 or so seconds at above 45mph, ABS light. ABS light always turns off if the car is restarted and is never there on a fresh start.

So I did some testing. ABS light not on. Run to 100, slam em down. ABS works - no light. Run to 45, get the light to turn on, accelerate to 60, panic stop - slide, no ABS.

I have heard tell of ABS computer being able to be programmed or accessed by the dealer. Any truth? Maybe get someone to input my revs/mile front and rear and booya?

I could pull the ABS fuse and not have it. I know how to brake modulate, but ABS IS a nice safety feature.

So, any input would be appreciated. No flames about my tire choice. I knew the risks/rewards and visual impressions and I'm happy with my choice, so basically, unless you have real input, don't bother...

Sorry to be a WEINER, but I'm just a little sick of the flames (toward anyone), but that's another thread!!!

Raudermaster
02-29-2008, 01:02 PM
That's odd Rich. If you pull the fuse though, won't that completely disable it? The NT is the same as the KDW2 right? My tire guy told me they are the same, just a new model name. Pics would be great, I'd like to see your car now with them.

magindat
02-29-2008, 01:17 PM
That's odd Rich. If you pull the fuse though, won't that completely disable it? The NT is the same as the KDW2 right? My tire guy told me they are the same, just a new model name. Pics would be great, I'd like to see your car now with them.

I'll post pics soon. Thanx, Jarod.

Only Tire Rack calls them KDW2 and apparently BFG doesn't like that.... causes confusion. NT means New Tread as opposed to the plain ol' looking standard tread.

It's the opposite problem of those who put front size on the back and went SMALLER.

I got a tip from a ABS module repair shop I called and they DID say the dealer can program the ABS module and does so regularly on raised trucks (I guess that have ABS sensors on the pumpkin).

Guess I'll start with my local dealer....

Raudermaster
02-29-2008, 04:02 PM
That's good to know Rich, I didn't know dealers could do it themselves. And BTW, I knew what the NT stood for. ;)

CKMustangCobra
02-29-2008, 07:24 PM
ABS sensors should be on the inside of the brake calipers on the axle.

Like other Fords, from my experience... the ABS system relys on the sensors to read segments of rotation... or RPMs to simplify.

Brakes applied and the front wheels lock up, the sensor locks up... causing the ABS block to activate and limit brake pressure in pulses to free the wheel.

If the sensors are not reading the same "RPM" on all 4 wheels, it can not decide when to use the ABS block... so the ABS light comes on and it deactivates the system.

You will need the same overall tire height on all 4 wheels for the system to work.

20" overall on all 4 tires..... 30" overall on all 4 tires....

I can see that even if the system sees a 1/2" difference it will turn itself off once it's driven long enough for the computer to recognize there is a size difference.

larryo340
02-29-2008, 08:25 PM
You will need the same overall tire height on all 4 wheels for the system to work.


Not exactly true. The anti-lock module on cars such as the Marauder with different OEM sized tires front and rear will are calibrated for that difference. Any deviation from OEM will then trip the system into thinking a tires is locking up.:)

While working in a Lincoln dealer we had a Town Car in which the anti-lock light would come on after I think about 20 MPH. It drove us crazy :confused: till we realized that 3 tires were 225/60/16 and 1 rear one was 235/60/16. They were all the same brand, the owner had a nail in sidewall and tire shop installed wrong size tire on it. Visually that wrong tire size looked the same. We put on the full size spare and all was normal. Who woulda thunk it :o. That was a mistake none of us in the shop would make twice.

Marauderjack
03-01-2008, 05:11 AM
Rich,

The OEM tires have a 1.3" diameter differential front to back while your ties choices have a 3.9" differential which is 3X the OEM!!:cool:

You will have to get closer to the OEM differential....maybe a larger diameter front or....God forbid.....go back to 18's on the rear??:shake:

I have played with TC and various tire sizes and I think you can make the system happy with 3% to 6% differential front to back!!:beer:

Good Luck!!

Marauderjack:burnout:

snowbird
03-01-2008, 05:55 AM
Rich,

The OEM tires have a 1.3" diameter differential front to back while your ties choices have a 3.9" differential which is 3X the OEM!!:cool:

You will have to get closer to the OEM differential....maybe a larger diameter front or....God forbid.....go back to 18's on the rear??:shake:

I have played with TC and various tire sizes and I think you can make the system happy with 3% to 6% differential front to back!!:beer:

Good Luck!!

Marauderjack:burnout:

I agree with Jack but from over 2 % to 6%. Before I started to play with sizes, I just substracted the height (10/32 " 2 times) from the overall diameter of the rear and I had my play. I assumed Ford program would have to accept a customer installing 2 brand new tires at the front and keeping on running with 2 very bald, completely used to the cord rear tires; ie in that case: slightly over 2 %.

Now, in your car you went Fiat Allis kind of way with 14.16 % front to rear difference (26.68" and 30.45 inches). We probably could do over 6% diff but it seems that at 14% you have overcomed the tolerance.

Hope it helps. :o

Edit: Thinking about it: using the same logic but opposite (2 very bald front tires and 2 brand new rears), the upper limit if there is one as it seems to be the case for your effort would be about 7.5 to 8 %. So maybe that's why at 14%, the systems get confused .

Marauderjack
03-01-2008, 07:34 AM
The ABS is looking at revs per mile per tire....the differences front to back are below:

Stock:

Front: 762 rev/mile
Rear: 726 rev/mile
Delta: 36 revs

Your Setup:

Front: 777 rev/mile
Rear: 682 rev/mile
Delta: 95 revs

I would think that anything over "Delta 50" would cause the ABS to act up or shut down??:confused:

If you could find a taller front that would give you a delta <50 revs you might be OK with the 20's out back??:beer:

Marauderjack

magindat
03-03-2008, 06:57 AM
Thanks, gents. I too, have done the math. generally ABS modules will allow a 7% difference between axles. I figured the Marauder would be a bit more. I'm sure it is. I do know EXACTLY what I've done with tire sizes and I like them and am not going back.

I have done some threshold braking tests and am satisfied with the performance without ABS. Aside from real true panic braking and occasional hard braking in rain, the ABS goes largely unused in FL - at least for me.

Also, when the car goes into ABS mode, loss of pedal feel and loss of my control of brake force is disconcerting. Old skool?

So, I think, in the end, I'm going to pull the ABS fuse and not have it. Perhaps if I rearrange tires in the future (and I might go back to 255's up front after these wear out), I'll try it again.

Thanx for the input!

ckadiddle
03-03-2008, 07:54 AM
Like you, Rich, I learned braking in big, heavy cars the old fashioned way without ABS or traction control systems. Somehow we survived!

magindat
03-14-2008, 08:52 AM
I got some good answers on this from Walter at Velde Ford in Vero Beach, FL.

I spent some time talking with him about this. He basically let me know that they COULD fix the ABS tire proportions with the For d WDS diagnostic tool. However, they would have to follow the WDS's software troubleshooting plan to get there. This would mean flashing the PCM to 'as built' specs and following the instructions given by the WDS which include driving. Well, with the SC installed, that's NOT gonna happen! He understood.

So we went down another road. Disable ABS since I'd just as soon not have it anyways, but also don't wanna see that light. He advised I unplug the ABS module harness on the front of the ABS assembly on the left frame rail. CLOSE! ABS is now disabled and the ABS light is not lit. However, the BRAKE light is on constant.

Based on further discussion with Walter. He thinks the PCM can be BS'ed to think the ABS module is still plugged in by sending either 12 or 5 to a certain pin in the harness. :dunno:

This sounds like a question for DROCK96Marquis, to me!

Gettin there!

arejayesss
03-14-2008, 10:07 AM
Rich, why don't you just use a clip lead to connect the brake light switch to the horn relay?

CKMustangCobra
03-14-2008, 10:12 AM
Rich, why don't you just use a clip lead to connect the brake light switch to the horn relay?

HAHAHAHA... We rigged a friend of mines car like that in high school... Had to be one of the funniest things I've seen to this day! LOL

rocko112869
03-16-2008, 03:32 PM
I ran into the same prob!...2003 grand marquis stock: 225/60/16 i put on front - 235/50/18 rear - 255/45/20 . Same prob...when I would cruise down the road, taking into consideration that my speedo was reading 5 MPH off (slower)from the wheel size change, when my speedo hit 60 MPH(really 64/65) like clockwork about 20 seconds later...the abs and trac control lights would would come on and Im assuming the systems were shut down....no effect to the car driving wise...but annoying!...doing my research...someone told me about an ABS correction module in the summit catalog...I checked,...made by ford racing,...I called they said it was discontued...but they were coming out with a new one...this supposedly gets hard wiried inline for gear ratio changes that could throw off the ABS..I think the abs module is programmed for a certain revs per mile...once you hit a certain speed and the gap between the front revs and the back revs is significant enough BAM, SHUT DOWN!...what size tires you put will determine what MPH it hits that magic MPH #....Last week I ordered a SCT xcaliber 2 which allows for tire size adjustments for aftermarket wheels, I talked to lonnie at BOC and he said he cant fix the prob but he can tweak the tune to delay it so it happens at 85/90 MPH...which is good for me I dont drive much over 70..so the lights should never come on...plus I want to give the car a kick in the ass powerwise!...I also didnt like the way the 18/20's looked so I bought 2 more 20's for the front but the OD will be the same still a difference in the sizes...anybody interested in 2 18" chrome wheels w/ toyo tires 235/50/18 for there maruaders let me know?

red
03-16-2008, 03:44 PM
I think the abs module is programmed for a certain revs per mile...

:agree: Our ABS / traction control modules are dependent on a difference in revolutions read at the front and rear encoders. The threshold likely considers both inflation and tire wear differences.

magindat
03-17-2008, 05:53 AM
...doing my research...someone told me about an ABS correction module in the summit catalog...I checked,...made by ford racing,...I called they said it was discontued...but they were coming out with a new one...this supposedly gets hard wiried inline for gear ratio changes that could throw off the ABS..I

Thanx for that. I'll dig further.