I realize that reasonable people can debate the effect of larger, as in my case, (or smaller tires) on ABS performance.

I have heard that the major OEM's (Ford, GM, Dodge) have said that so long as you stay within +/- 10% of OEM recommended the ABS will perform just fine.

I am wondering if anyone has that statement in writing. Either in a service bulletin, a shop manual, or in response to a direct queery to a OEM. And if you do, if you would be willing to give me a copy.

Thanks for your help.

AJV

 

yes it would be nice to have that in writing. It is supposed still perform normally as long as it is within the parameters you mentioned.However My abs does not function normally.I went from 255/70 series tires to 265/75 series tires. That is enough to throw the speedo off by 1-2 mph.The brakes really want to lock up now.

 

Lightning,
Something is definatly wrong with your truck, as I went from the 235/70/16 to a 285/75/16 with no problems at all. I would have it checked out. Here is my question: Does the abs sensor differ from truck to truck? What I mean is, did my truck that came with 235's have a different abs sensor than a truck that came with the 265/70/17's? I doubt it, so the 10% thing is relative in my mind. There seems to be plenty of people running 35's and 36's and even some running 39's with no problems. So I kind of wonder about the whole 10% thing.

------------------
97 4X4 Flareside
4.6 5-Speed
Superchipped
ASP underdrives
Airaid
Dynamax headers
Borla Cat-back
Clear corners
5% Tint
285/75/16 BFG All terr.
16x8 AR Baha's
Rancho 9000's

Soon to come:
3" Perf. Acc. body lift
w/lift lips
315/75/16 BFG KO's
4000K bulbs

 

Here is the response I got to a e-mail to the ABS education alliance;

" Here's your answer. My source is Jim Lawrence, exec director of the Brake Council here at MEMA.
OK to increase tire size as long as the difference is 5% or less of the loaded rolling radius of the wheel/tire.
I understand your pickup truck has four wheel ABS but no traction control or intelligent stability and handling system technologies.
Have fun driving, but remember that ABS is only a safety tool and doesn't allow you to attempt defying the laws of physics.

Rosemarie Kitchin
Director, ABS Education Alliance"

My question now is, what is the largest tire Ford recommends? Notice I said recommends, not what it offers.

I believe tha largest Ford offers from the factory is 265/70R17 at ~15.8" in radius.

AJV

 

This is interesting!

I was just doing some math looking at the tires listed in the Ford F-150 brochure and this is what I found.

The minimum tire Ford lists for a f-150 (4x2 or 4x4) is a 235/70R16 which has a diameter of 28.95 inches and a width of 9.25". The maximum size tire they list is a 265/70R16 which has a diameter of 31.61 inches and a width of 10.43 inches. Thats a 9.2% increase in diameter and a 12.8% increase in width.

Assuming that Ford does not have a ABS control module for each tire/wheel combination listed, which would be a nightmare from a inventory & service standpoint. This would seem to indicate to me that the ABS system can handle a fair degree of difference in tire sizes (within reason of course, for you 44" swamper fans).

Which makes sence given the vast array of aftermarket wheel/tire combos out there.

Its also interesting to note that the ABS question seems to come up more often in regards to larger tires, when it would be logical to assume that smaller (for the fans of lowered trucks) would impact the ABS just as much as a larger tire.

I am interested in your thoughts.

AJV

[This message has been edited by ajvamvakias (edited 11-14-2000).]

[This message has been edited by ajvamvakias (edited 11-14-2000).]

 

I have p265/70R17. I am supposed to have the 16 inch wheels. My truck came equpiped with ABS but I have never felt them. I have locked up the tires before and never felt a hint of ABS. No reason why mine shouldnt be working. Its no big deal to me though.

------------------
'97 F-150 XLT Clearcoat Red
4x2
4x4 wheels
Stepside, K&N, bedliner
32inch tires,flowmaster
tint, matching ford sticker
5spd fully loaded, hidden hitch
new spark plugs
Comming soon:
spark plug wires,leveling kit,toolbox,
bed rails,push bar, CB with whiplash,
clear corner lenses,brush guard, blackouts,
edlebrock shocks, hypertech, K&N induction system,KC highlighters,
bed xtender, BOSE audio or infinity gold, disc changer,
side steps, dixie horn, white faaced gauges, and those small fender flares some 4x4's have,
matching boddy color of course, and some of those door guards,ventshade visors, power pulleys, that is all
i can think of right now

 

it does not matter if you go smaller or larger in tire diameter unless you have a different overall outside diameter size tire on the front than the rear, the abs sensers monitor the rotations of the front to rear tires,so if the front tires are making more revolutions than the rears you're abs light will come on and it will not operate correctly

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99 F-150 XLT 5.4L,17"CENTERLINE WHEELS,GIBSON CAT BACK,GIBSON HEADERS,POWERDYNE SUPERCHARGER,POWERAID THROTTLE SPACER,

 

ABS light isn't on, so the truck "thinks" it operating normally.Perhaps I should pay a little more attention while driving(good luck w/a 2 yr old sitting next to me begging to hear that da** britney spears cd) I have a few other issues w/ my truck that the dealer will get to look at as soon as I find the time.Most of them are just little annoying things.Nothing major.

 

Last December, I got rid of my 'Stones (yea, the ones that were later recalled) as the were wiped after 32K. I could never get enough air in them to keep the edges from wearing. They were the 2.35x70 R16's. They always reminded me of Dunkin Donuts, as they looked so small on my '97 4x4. Too tiny.

I got a set of Michelin XCX/APT 235x85 16R's. The tread design is a little more "aggressive", but I do use the vehicle on muddy job sites. The 85 sidewall ratio does make a big difference. Both in appearance and diameter. These are 31.5" in diameter. I have noticed NO difference in the ABS capabilities. I have one hill on the way home from work that I have to stop at the bottom. The road is particulary slippery in the rain. The old tires would be using the ABS very often (they were slippery tires anyway) and the Michelin's rarely use the ABS. I have felt it once or twice, but no where near the amount of times with the 'Stones.

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1997 F150 4x4 extended cab
1986 Buick Grand National
1970 Buick GS 455