winter time chassis setup

[vrex]

Hi all, im curious how much track width effects traction in a car. from my experience in karting, front and rear track width has a HUGE impact on handling, traction, and tire wear. I recently picked up a winter setup (sport techno's 8x18 and 10x18 with, i assume, correct offsets; Blizzak LM25's 215/265's). The seller included 25mm spacers and requisite bolts. my summer setup has 15mm rear spacers and 7mm fronts on stock 8x18/11x18 wheels, and i swapped spacers front and back, no spacers front & 15 mm rear, etc just to see how it feels. spacers made a noticeable diff when added to the rear, and none up front, but for aesthetic reasons i kept the 7mm fronts in there. for the winter, should i run spacers at all? i learned by trial and error, but i dont want to sit out in the cold changing spacers around. also, what cold pressures are you running your tires at? im inclined, while there isnt snow on the ground but its cold out, to run them rather high, and bleed them as conditions dictate. bad idea? ive never owned blizzak's im not familiar with their character.

Thanks!

[jmj996]

I run spacers with the longer lug bolts as well. I can't attest to how much of an impact it makes with any real data, but I do want to add something that I learned from a dealer, because I don't see this written about the use of spacers very much: I was told that the reason there is so much space between the outer edge of the wheel and the fender lip, as the car comes from the factory, is to allow for the use of factory snow chains (look them up - they're available from Porsche as a factory accessory). The extra space doesn't have anything to do with any perfect engineering scenario, it's about allowing the space necessary to use the chains, so before the spacer-haters start chiming in I want to throw that out.

Text from a Porsche snow chain product available online:

Special low-profile design with fine-link chain for minimal adhesion of ice and snow, these chains are easy to fit. Note: Cannot be fitted to vehicles with spacers.

Seems to provide further clarification that the spacing from the factory is simply to allow for snow chains.

Edited December 7, 2009 by John Jones

[vrex]

well i wont be running tire chains, so where does that leave me for optimizing traction? space wide for understeer? space it to stock geometry with just a 25mm? spaced slightly under stock? also, how about front track width? and last and most important, what are you all running for tire pressure?

[rockjock]

Tire pressure is a subjective #-here in MN I change mine depending on temp (it can fluctuate from 20's down to -20 in a week)-as well as snow depth (we're just now starting a 6-10" snow day here). I'm also running the LM25's-like them so far (as compared to Yoko W drive in the past)-I'm running on a C4S Cabrio (04)-bought AM rims from Tire Rack (5 spoke Turbo knock offs) that are 18x8 front and 18x10 rear-no spacers-traction has been fine so far-I dont know that adding 10-25mm in track will improve enough in winter to notice (I drive pretty hard all the time-but with snow and cold-I slow down too).

Optimizing traction would really depend on tire choice and pressures-I think you're looking more for handling char. of the car?

Edited December 8, 2009 by rockjock

[vrex]

im not out to optimize the handling of the car as though im going racing. i just happen to remember that moving the wheels on my kart in 1/2" on both sides yielded some drastic handling changes. so moving my wheels in and out an inch on my car would seemingly have some ability to change things. but the difference with a kart is; no suspension, no differential. a car is much more forgiving and the fudge factor due to the bushings and suspension and whatnot may make track width a moot point. but based on what i learned in trial and error with the summer setup, there must be something to it. realistically though, winter driving is much more conservative, so looking for a handling advantage is going to lead me to be probably a bit overly confident and end up in a ditch. i just want the most traction possible, and as with anything else, thats probably more about psi than track width (like you said)

Cheers!