I thought folks might appreciate seeing how our own SM2 class racer is coming along. Fender flares went on this past week so we could add lots of rubber to handle our 262 HP. We tested today with our Enkei RP-F1 18x9.5 and 285/30/18 tires all four corners...and discovered we could use even more tire. We figured out we can go taller in the rear and I think that will help the autocross performance....will likely try some 295/30/18s in the rear soon.
I have autocrossed many a Miata over more than a decade but never had so much fun as autocrossing this Cosworth Supercharged MX5. Once I get fresh tires on it, it will be amazing. Once I got the old tires hot enough to stick decently I discovered that I could point the car at will. If I wanted to tighten my line a little I just gave it enough throttle to bring the back end around just enough. Big thanks to Cosworth for the cold side mount that allows such a precise throttle application....it was big fun!
Last edited by Brian on Mon Nov 03, 2008 12:37 pm, edited 3 times in total.
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
The front is no more than what you would guess...you cut your metal, trim and fit the flares as you please, and paint and rivet.
The rear is more involved because you end up with two parallel metal panels that should be welded together as shown here to maintain the integrity of the structure.
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Just out of curiosity, for a nc with a sc blower that will only see track time and no autocross, would going to 18x9.5 wheels with 285/30/18 tyres be beneficial? Or will it be sufficient to just stick to 16x8 or 17x8 and 245 tyres?
Just out of curiosity, for a nc with a sc blower that will only see track time and no autocross, would going to 18x9.5 wheels with 285/30/18 tyres be beneficial? Or will it be sufficient to just stick to 16x8 or 17x8 and 245 tyres?
I run around town on either my stock 16x7 with 225/50/16 or my old RX7 16x8 with 245/45/16
But for track work at DOUBLE STOCK horsepower I think your lap times will improve by moving wider than 245mm tires. You will be able to carry more corner speed...both into and out of the turns, and get into the power earlier on corner exit. Obviously the wider tire will mean a little more drag down the front straight but at this horsepower level I think you will come out ahead on most tracks with the extra grip.
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
That looks like a lot of work. Not to mention the thought of CUTTING INTO MY LITTLE BABY. I am not sure I could do that without crying. I am going to have to leave that one alone. If I decide that I need to do it, I will have to take it to a body shop and have it done. Otherwise, I will be having nightmares for month to follow.
New tires for this weekend!! Had lots of fun sliding around on two year old Kumho 285s at the last event and wanted both a newer tire and a little taller effective rear gearing. Thus, this weekend we will have it with:
I told a regular customer about this plan and he noted that the Tirerack tire specs chart shows the 295 is actually NARROWER than the 285. Not correct, the width of the rim is critical to reading the measured width of the tire. Use a wider rim and the measured width goes up...and what the Tirerack chart is really telling us is that 295/30/18 is a bit pinched in comparison to the 285 when used on the same comparatively "narrow" rim. However, since we planned to have 18x10 RP-F1 in the rear for the 295/30/18, I knew we would end up easily getting more width on the ground with this combo...which was confirmed as soon as the tires were all mounted up and measured. This picture helps illustrate that result, on the left is a stacked pair of 295/30/18 on 18x10, 38mm and on the right is a stacked pair of 285/30/18 on 18x9.5.
Nonetheless, it appears we could fit even more in the rear if we wanted to...
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Why do the flares in-progess photos show a stock nose while your completed photos show the Mazdaspeed nose? I thought you had the Mazdaspeed nose on the car already.
Oh, wait. Your car is a blue 2006. Who's silver car?
Also, what are those wheels and tires doing to your scrub radius?
