Jditlfm

iTrader: (26)

So i want to run a taller tire in the back of the car but i am worried about a abs inop light coming on. I want my abs so forget about pulling the bulb or anything like that. Does anyone know for sure the range between front and rear tires the computer will allow before going inop?

The tire size I have in the front are 275-40-17 = 25.6" tall
I want to run a 295-45-17 in the rear =27.4" tall

Speed calibration is easy as i have tuning software. What Im thinking is about running a 285-40-17 front for a 25.9" tall and then the 295-45-17's in the rear. Some one said the computer will allow a 6% difference before going inop so with that combo it will be close, but i'm not sure. Anyone have any experience with mixing front and rear tire sizes. Thanks

SJM Manufacturing Inc

iTrader: (5)

I don't think you're going to have luck with that. It's almost a 27.5" diameter tire.

Even if you were at the limit range of where you didn't trip ABS, it will NOT function well and will activate when it's not needed hampering what “performance” benefits you may want.

I'm not sure why you want ABS so bad, but if it’s that important to you then leave everything alone so it can work as it was intended to optimally using OEM components.

This is a simplistic analogy, but if you changed your cam or other component in your engine, your OEM computer will be controlling your engine as if it was stock. Sure the engine works, but not how one would want it to. This is why one tunes the engine via the computer…you cannot do so with ABS. The EBCM is optimized based on OEM settings. If you start changing parameters of the car, the EBCM still functions from the OEM tuning. Not good.

SS SLP2

iTrader: (8)

my 295/45/17 just came in today as my a4 4l60e is slipping 1 st gear it may be a bit before I try them but getting to the last part of your question
I have several times ( 8-10 times) ran OE stock 275/45/17 on front and
245/xx/17 and 255/xx/17 on rear ( ran the odd ball tires just to burn out in several city cruise because they were free use for burn out)
I do not know how much differance in dia. but I never had a problem or set a code and I am 4 channel
my .02' Johnny

Jditlfm

iTrader: (26)

I understand this, if i could change the ebcm parameters i would. I simply want to know the range allowed? I want abs for the simple reason of being able to push the brake down as hard as i can and steering around what ever i want to avoid. People mock Abs all the time saying its not needed its useless i disagree. I have driven both I prefer having abs.

ls2 bait

iTrader: (11)

i prefer no shiny light on my dash board. thats why i still have abs. but usually you have about a 5% range for the abs. and the m/t 295 measure in at just about 27" so you will be ok. on the verge but ok.

Jditlfm

iTrader: (26)

I just wish I could find a 27" tall front tire for a 17' rim . It would just make this easier and allow abs to work in a better range. I also hate the light being on but some people will just say to take the bulb out. If i get rid of abs it will be because i wanted to save some space/weight/got fed up with not being able to mix tire sizes. Im not at all three yet.

Edit:

I see Nitto makes a

255-50-17 27.03" tall

275-50-17 27.88" tall

I wonder which one would look better on the front I would prefer the wider 275's but at the same time i don't want my front tires being taller then the rears in either overall height or sidewall thickness.

I guess my best option is a 255-50-17 front and a 295-45-17 rear. I think that's the solution to all my problems. Thanks guys.

SJM Manufacturing Inc

iTrader: (5)

I don't know how else to help folks understand what I've discussed. My points are not to tell everyone to remove ABS and its worthless. I'm not here to argue or tell you you're wrong for liking ABS. As discussed, you're setup will NOT be configured correctly for the non-stock configuration. The further you go from OEM parameters, the worse it will be. Just as I discussed using an aftermarket cam or other modification which requires PCM tuning.

If you're handicapped to using ABS as you appear to be, don't rely on it like you use to do...it won't operate the same! Your ABS lamp may not illuminate but don't let that be a false sense of security!!

Don't get me wrong, ABS on a stock oem configured car works very well in some circumstances. Change parameters and it will no longer work as it was engineered. There is no substitute for smart and proactive driving.

I personally never liked ABS and found it to be a hindrance not help. I feel if you have to rely on your ABS system you're not in control of the car, you're letting it control you. You obviously feel differently.

Jditlfm

iTrader: (26)

I disagree.
If all the tire sizes are the same 27" across the board how is it going to operate differently then stock config?
My plan is to run a 27.09" tall tire in the front as well as a 27.2" tall tire in the rear.
255-50-17 Front
295-45-17 Rear

Each wheel speed senor is going to send the same voltage signal to the BCM, I don't see how adding a inch all around is going to effect anything. Under a wheel slippage situation is still going to pulse the brake caliper or calipers (3 channel system) just the same as it would with the stock 26" tire. The only reason it should have a problem and operate any different is if i mix overall tire diameter. The system doesn't care how tall the tires are in general it just cares that they are all the same overall height (within a certain percent) and that they send the same signal voltage while going in a straight line. Obviously the closer you can keep all 4 tires the same height the better the system will operate. And BTW I would classify anyone's driving habits as handicapped just because they want to utilize ABS. The only time abs is useless is either in the snow or on ice. But this is a summer car.

Answer these question's for me

When is a tire most effective in a braking situation? Locked up, rolling or just before wheel lock up?

What are the two main goal's of abs?

You think you can pump your brakes as quick as an abs motor and/or on independent calipers?


Let me guess you don't like fuel injection either your more of a carburetor guy?

SJM Manufacturing Inc

iTrader: (5)

If the front/rear tires are the same size, then it would be fine.


There are positive and negative aspects of ABS functionality. It will not provide the best solution for every situation. Some designs are better than others even from a basic proponent, 3 and 4 channel systems.

I'm not going to debate on this matter. I think with my background which I clearly note, not to brag but to let readers know when I answer a question, I'm not throwing an answer from the cuff or a 16 year old kid giving googled answers. One can reasonably assume I can answer any of those questions clear and precise. I'm not here to take your quiz, I was originally here to help you with your question.

If you understand your ABS system as to if I answered your questions to validate or negate them, than you shouldn't be here asking a question regarding tire configuration.

For the record, I'm a proponent of both carbureted and fuel injection, they both have their advantages.

cdubbzz

iTrader: (11)

Let me know if those fronts work out for you. I'm currently running
the 275/40's up front and 295/45's in the rear (ABS light is in full effect).

Jditlfm

iTrader: (26)

I only asked the range the BCM would allow, and/or if anyone had any experience with mixing tire sizing and what they got away with. Because what works on paper sometimes doesn't work out in real life. And my knowledge of automotive systems comes from the 4 years of automotive schooling I have as well as being a Mercedes technician for a living so I'm not just throwing things out there i read off the internet merely backing up my position on why i feel abs is important and why i think it will work how I want it.

SJM Manufacturing Inc

iTrader: (5)

based on your tech school background, you should know these things.

You shouldn't have needed to ask how ABS will function.

I'm surprised you'd attempt to rely on ABS setting up the original parameters as you suggested.

Jditlfm

iTrader: (26)

I will let you know on the tires, My car has about two months before its going to be ready though.

Jditlfm

iTrader: (26)

Like i said i was asking the range the bcm would allow and if anyone had any experience with it. I fully understand what will happen and that's why i wanted to run a 27" tire up front and i clearly stated that if you read my post.

bigdsz

iTrader: (1)

Things other than tire diameter can cause the ABS inop light to come on. I put a 9" Ford rear in and ran 26" tires front and back and still got ABS inop, reason being the big screw in lug studs in the axles were creating a huge magnetic field ******* with the sensor.Well I shimmed the sensor out by about 3/8" and now I set very few lights unless I'm going real fast.

SJM Manufacturing Inc

iTrader: (5)

Actually, you clearly stated otherwise. Your initial post read you wanted a combo of 25.6 and a rear tire 27.4" tall. You also stated you were considering switching to a 25.9" front tire. That is what my initial comments related to. Later you considered switching to a 27" front tire.

It really doesn't matter anyways. You've obviously overlooked my comments turning defensive for no reason. Do what makes you happy.

Jditlfm

iTrader: (26)

You posted all of this right after i said i wanted to run 27" tires all around. You caught the attitude with me first Guy. Looks to me like your the one that cant read passed the first post. I'm over it. its not helping anyone. If this keeps going i will just delete the thread I'm done EThuggin back and forth with you.

Jditlfm

iTrader: (26)

That's good to know. My buddys 4 channel set up was a little close when I did the 9" install but i shimmed the sensors away and i haven't had a any problems with it. But he also had stock studs...

bigdsz

iTrader: (1)

My latest set up is 26" diameter front and QTP 27x11.5x15 backs with minimal ABS lights even with the big screw in studs. I believe the larger diameter tires are causing zero additional issues. My friend has Hoosier 28" with a 12 bolt and sets zero lights.