Friday, October 3, 2008

Rollin', Rollin', Rollin'...Keep Them Fenders Rollin'...

Somewhere many months ago, I said, "I'll find some wheels that fit better, because I don't want to alter the fenders to clear these." That was before I decided that the G-Games wheels are just RIGHT for the car. Not that I care -- okay, so I do care -- but 100% of the people who have an opinion also love the wheels. So they stayed, and to make sure the rear tires didn't collide with the edge of the rear fenders, we rolled the fenders.

You can do this a couple of different ways. The old-school way involves a baseball bat rolled between the fender and the tire. That's a little crude for my tastes, although there are people who can do it really well. We used a dedicated fender rolling tool, which bolts to the hub, and has a little urethane wheel and a screw that is used to press the wheel against the fender lip. It works well and makes sure you roll a nice circular arc. (The picture above is from Tire Rack. You can buy one of these tools from them, if you want.)

Mach V master tech Mike Gerber performed the delicate surgery on the STI, and the results are very nice. The fender is flared out ever-so-slightly -- so much that I didn't notice it at first -- so that it clears the outside edge of the rear tire. Mike made sure to heat the paint at the edge before rolling, so the paint did not crack. Before, the tires and fenders would rub together under any large suspension movement. Now, they don't seem to be able to touch at all. I've done some pretty hard cornering with the new setup, and have not been able to get them to rub.

At left is the fender and tire, post-fender-rolling. I'll be doing a bit more high-g driving to understand more about the results of our sway bar swap, and in the process I'll keep an eye on that rear tire/rear fender. Stay tuned.

I do have to make a note here about wheel offset for the 2008 STI. I've been seeing a LOT of 2008 STIs running very low-offset wheels. I think this is mostly because there are not many high-offset, large-width wheels on the market. Optimal offset for a 9.5" wide wheel on this car is probably around 50mm, but you'll be hard-pressed to find anything that wide, in anything CLOSE to that high of an offset. (As of this writing, I do have a set of 19" ASA's in the showroom. Email me if you're interested...) Most 18x9, 18x9.5, 19x9, or 19x9.5 wheels are in much lower offsets, like +30 or less. This kind of offset is great for a deep concave look, which I admit is really cool. But it also puts the tire really far out toward the fender, resulting in pretty serious interference problems unless you go with a narrow tire. So I've seen some people running only a 225 or 235 width tire so it won't rub. The car comes with 245s! I'd hate to go to a narrower tire just because I couldn't find the right wheel fitment. Some of the people who do this seem to really like the sticky-out wheel look, or the small-tire-stretched-to-large-wheel look. But in many cases these cars are severely compromised in terms of driving them every day, and in outright performance.

The other isse that nobody seems to talk about is that changing the wheel offset changes the scrub radius, and the steering feel is changed. For the worse. Even the relatively small (-15mm) change I made on our car resulted in a noticeable loss of steering feel, especially at higher speeds.


Emil said...

Hey Dan,

I'm a former Mach5/Ultimate customer (2005 WRX) living in the UK now (sold the rex when I moved. I still cry a little when I think about it).

Love the blog. Interested in your experiences with the new STI, as I will likely get one when I return to the US.

One quick question - your 1/4 times were with the AccessPort?

Mach V Dan said...

Hi Emil!

Yes, we were on the off-the-shelf Stage 1 map when we drag-raced the car.

Mach V