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Saturday, November 01, 2014

Doug's Domain

Doug Vetter, ATP/CFI

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Thursday, November 20, 2003

The 2nd set of Dunlop SP8000's are spent. The rears are at the tread wear indicators, while the fronts have about 1/16" above them. As I've been pondering for some time whether to go with another set of SP8000s or try a new tire, I let these wear farther than the last set. As a result, I've really noticed a decrease in wet performance as well as a significant increase in tire noise. Considering that the tread now resembles a DOT legal racing slick, that's no surprise.

The main reason I'd considered going with a different tire is because this set of SP8000's was particularly out of round. When I brought the car to my mechanic shortly after they were installed at another local shop, he said he balanced the tires as best he could and moved the worst two the rear, where I would not feel them as much. He also strongly suggested I NOT buy Dunlop tires again.

When it became clear I'd need to look for new tires recently, I went back to him and asked for his opinion. He said that he balances tires all day long on a Hunter RoadForce balancer, which can measure the eccentricity of the tire in "lbs of road force differential". A perfect tire would present 0 lbs of differential, while a bad tire might between 30 and 40 lbs. He added that Dunlop and Bridgestone, for example, are all over the place...some good, but mostly bad (anywhere between 20 and 35lbs, with some as bad as 40). He said Continental aren't too bad, but Michelin are the best...at around 3-5 lbs on average.. BMW specifies a maximum of 18 lbs. So, what to do?

I initially considered many tires, including a promising alternative for the SP8000 - the Kumho ECSTA MX. But after weeks of on and off analysis, with emphasis on finding a tire with low eccentricity, I worked it down to one of the two Michelin Pilot Sport tires. The original Pilot Sport is a summer-only ultra high performance tire that comes on the newer sport-package BMWs, while the Pilot Sport A/S is Michelin's all season equivalent.

I really wanted to go for the summer tire, but two things stopped me.

The good news is the A/S came highly recommended. Nearly all personal reviews I read about this tire raved about its performance in dry, wet, and (yes) even snow. The downside? They're EXPENSIVE. Tire Rack had them for $180 each + shipping, or a total of $750...which is a LOT of money for tires that I'll likely replace in 18 months or 30K miles. Just for grins, I asked the dealer's parts guy how much they would charge for these tires and he said $250/each(!). When I mentioned Tire Rack's price he said that he would call Tire Rack if it were his choice, and added that I should have the tires shipped directly to the shop for installation. So I shall.

While they have the tires off, I plan to have them do front pads and rotors (still a bit ahead of schedule, but better to do before the holidays, IMHO), do the biennial brake fluid flush, and a mid-cycle oil change. Total bill will likely be around $1200.

Oh, and incidentally, I'm not fooling myself -- I know that these tires will NOT have the dry performance of the SP8000's. You need only look at the respective treads to see why. I am also concerned about more rapid tire wear on the Pilot Sport A/S, in spite of what I have read to the contrary. If the tire significantly impacts dry performance, next spring I will either buy a set of Pilot Sports or other tire I can burn up during the summer and swap the tires on the existing 16" rims, or I'll buy the 17" M-Contour rims (available on the E36 M3) and put the summer rubber on those. That way, at least, I can swap the tires on my own, and I'll improve the looks of the car as well. And, before you suggest how much THAT will cost, it's STILL cheaper than a second car. Been there, done that, got the t-shirt.

Cost (parts): $750, Mileage 87005.