Rams Eye The Track Guy

2012 Boss 302 on square 305/30/19 RE-71R's at AMP - Graham MacNeil © For better or for worse, I have heard and read so much about RE-71R's. Everyone swears by the grip but complains about the wear. Generally speaking, the pros are: 1. They grip as well or better than most R comps. 2. They don't wear as quickly as R comps if driven occasionally on the street. 3. They work better in the rain than R comps. The cons were limited to overheating quickly when used on track (being an autocross tire) and wearing too fast on heavy cars like mine. In the popular 200 TW category, they are faster than the popular Hankook RS-4's and BFGoodrich Rival S's according to published Tire Rack Tests. According to plenty of reviews, they are also faster than well established R comps like R888R's (which don't seem to work too well on heavy cars anyway) and the venerable NT01's. But I was still hesitant for a while until I talked to a tire tech support gentleman...

I've been a huge fan of Michelin PSS tires and exclusively bought them for the Mustang over the last four years. So how did I end up here? This year, I was hugely interested in trying an "R-comp" tire. I had my eyes set on Bridgestone Potenza RE-71R's for two simple reasons: price and reputation. Although not a true "R-comp" tire on paper, it performs like one by the account of every single test and review I've read (down to wear rates...). They seem like they're easily the most affordable (from a big brand) R-comp tire and combine that with a reputation for having tons of grip, it was an easy top contender. I had my concerns, though. For one, I'm told and have read that they are an autox tire, not really designed for high speed, pressure, and temps associated with open track. For another, the Mustang is a heavy car (as far as track cars are concerned) being roughly 3,800 lb. (including driver), which will amplify the unwanted open track load...

C7 Corvette Grand Sport... doing a burnout with a proper diff - Graham MacNeil  © I wrote a tech post comparing various open and limited slip diffs for a comparison and I found that a lot of people were asking questions. To simplify and make it easier to read, I decide to break them up for a future tech article about handling. Make sure to stay tuned for two posts on limited slip diffs this week!. WHY DO YOU EVEN NEED A DIFFERENTIAL? A differential's job is to allow two wheels on the same axle (or two axles in a 4WD drivetrain) to spin at different speeds so a car could smoothly go around a corner. Why do the wheels need to spin at different speeds? Each wheel on a car has to travel a different path to reach the end of the turn. You can see that for yourself every time you drive on snow covered roads or muddy trails. Four different tracks by four wheels/tires on one car going around a turn - Rams Eye The Track Guy  © If you take a turn, you'll see that each whe...

The "M5 BMW should have built" is what Switzer, the Ohio-based tuner, is calling their P700 BMW M5. The new F10 BMW M5 is far from lacking in the power department, thanks to a twin turbo 4.4 litre V8 making 560 hp and 500 lb-ft of torque. The numbers don't tell the complete story though - judging by acceleration test numbers compared to similar cars in the segment with comparable hp ratings, power-to-weight ratios and even some dyno tests, the hp rating is probably closer to what the car makes at the wheels rather than the crank, which is what many people have come to expect from BMW engines. That was not enough for the folks at Switzer Performance though, so they made a few modifications to bring the numbers up a little. How much is a little? Well, if Switzer is conservative with their power ratings like BMW, then nearly 140 hp. For $6,995, they will take a stock BMW M5 and turn up the boost with a new engine control unit (ECU), replace the stock exhaust with...