Hoosier A6 Query

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Hoosier A6 Query

Postby Randale » Thu Aug 22, 2013 7:13 pm

OK, lusting after a set of Hoosier A6 for AX.

Lowering car with Ohlins.

Thinking PF01 17x9, Hoosier A6 245/40/17. (no 235/40/17 it seems?)

How much fender work will be needed?

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Re: Hoosier A6 Query

Postby Brian » Thu Aug 22, 2013 7:24 pm

Need a good roll. Not a roll with pull....but a roll of the lip up pretty much flat.
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Re: Hoosier A6 Query

Postby honestobob » Thu Aug 22, 2013 8:54 pm

What do you do with all that plastic shrouding inside the fender when you roll the lips?
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Re: Hoosier A6 Query

Postby Brian » Thu Aug 22, 2013 9:49 pm

We leave the plastic fender liner in.....the only trick is pulling the tabs that hold the liner before you roll up the lip so you don't dent the paint. The rolled up lip will pinch the liner and do the job the plastic tabs were doing.
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Re: Hoosier A6 Query

Postby Randale » Fri Aug 23, 2013 10:05 am

So, along the same lines, I am not completely sure I understand "offset."

Does the RPF1 (less offset at 45mm) move the outside edge of the tire more toward the midline as opposed to PF01 (offset at 48mm)?

Less chance of rubbing with less aggressive fender roll?

And, is there a significant advantage for 245/40/17 with 9 inch wheel versus 225/45/17 with 8 inch wheel?

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Re: Hoosier A6 Query

Postby Brian » Fri Aug 23, 2013 10:14 am

The 45mm offset moves wheels out by 3mm compared with 48mm.

Thus, 45mm requires more fender work for 245mm tire than the 48mm offset wheel.

For autocross there is a significant advantage with 245 on 9 inch compared to 225 on 8 inch. I recently drove a customer's STR class NC at BMW autocross back to back with my 2006....and I could feel the extra grip of the 255mm tires on 17x9 RPF1 compared to my 235/40 on 17x8....particularly under braking. For autocross you usually want the limit of what you can fit under the class rules. For STR that limit is 9 inch wide wheels and with really good fender roll we can just stuff 255mm tires on that 17x9 in NC fenders....which is what you see below.

Image

Now, for high speed track driving the analysis above does not hold because aero resistance plays a bigger and BIGGER role as speeds increase. My supercharged 2007 autocross toy with massive 10.5 wide wheels and 285 hoosiers really proves this, with fast autocross results and even some track records at the tightest slowest tracks like Horsethief Mile.....but it is comparatively slow at higher speed tracks like Laguna Seca.....and a downright dog at Fontana because it just runs into wall of air resistance at about 130mph.
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