[senortighto]

what about the electronic brake force distribution used on wrxs and stis from 04 and up?

wouldn't this have a great effect on stopping distances and using different brake pads front and rear and possibly different braking surfaces at the moment the driver depresses the brake pedal?

[MGizzle]

Sorry guys. No new info, haven't really bugged the guys too much since we are busy as heck this year with all these Truck sales falling through the floor.

I will try to call the guy up again.

As far as the electronic brake distribution, that is your ABS/ESP unit. It's built into the systems logic.

Let me try to hit up SAE papers tomorrow to see if they have any data on tire swapping.

[Flycaster]

Originally Posted by MGizzle

Sorry guys...we are busy as heck this year with all these Truck sales falling through the floor...

Understood - whenever you have the time, not a big deal.

[MGizzle]

Well, I haven't been back on the site for months now and remebered that I commited to explaining this a bit better I guess. Anyhow, attached is how I understand the ABS and how some vehicle calibraters are looking at it as well. I also attached two pages from "Fundamentals of Vehicle Dynamics" from Thomas D. Gillespie, my professor from undergrad, and coincidentally his chapter showed exactly what I spent an hour on drawing up in Paint.

Anyhow, take a look at it and hopefully it will make more sense why changing the tires will/could throw off your ABS calibration and so with stopping distance.

http://i214.photobucket.com/albums/c...zle_05/ABS.jpg

I hope it helps.

Anyhow, it clearly shows how the calibration depends on your INDIVIDUAL tire characteristics. Assuming that all tires are equal, changing to tires that have a different slip curve will throw off your performance since the ABS unit still assumes you have the old tires. Now, the ABS calibration guys tune to the OEM tire characteristics hence the ABS unit is tuned to know when the peak on the slip curve is being passed and it tries to climb back up there. Hence, if you switch to tires with significantly different slip curve, the ABS unit could be operating in a different portion of the curve, which is not near the peak force. Hence, your tire performance is not optimized. The opposite could occur, where you get tires that have a higher peak force at EXACTLY the same % slip but that is something you can't even assume in my opinion. That's like buying a turbo assuming what it's efficiency maps are. You need to know some of this data and the Tier 1 suppliers get it from the Tire OEM's.

Finally, please try and search for Pirrellis new tire, where they are trying to implement load/temp sensors into the rubber compound. If you read on in the article (autoblog had a good one) you will understand why. In summary, instantenous information for the ABS/ESP modules (as well as other things) on where the tire is. Switch tires on a car like that and God will only know what will happen to your performance.

Anyhow, enjoy the read.