Yesterday I replaced the 16" bridgespokes/RF combination with a set of 18" R105/Kumho SPT 215x40. I was astounded to discover that the previously vicious torque steer is totally gone with this new tire/wheel setup. Awesome!

 

Congratulations! I have just started pushing my 07 MCS a little harder now that I am beyond the 1200 mile break-in and have definitely noticed some "tugging" when I get on it.

As such, I am also considering a switch to a different wheel/tire combo, but I am not sure where I should look in SF or Alb... I have searched until my eyes bleed on the net and know what I want - the issue now is that I would prefer to buy the set locally instead of @ tirerack or some other online retailer. Additionally, it would be nice to see some of the wheels in person.

Ideas?

Also, any pix of the new setup?

 

That just means the engine now doesn't have enough torque to over come the extra mass of the wheels and lateral grip of the tires . Not really a bad thing.

 

That's what I was thinking, but it must be better grip, because the R105s weigh 23.2 lbs and the tire is about 1-2 lbs. lighter than the RFTs. So weight is about the same.

 

Its not just the mass of the wheels that the engine is having to push through. The larger diameter wheels (lets take the 18in wheels for example) cause the engine to have to put more power down to do a full rotation. Larger diameter = larger circumference that the engine has to battle against. So that is why you noticed that the torque steer has diminished.

 

Circumference of wheel tire combo is no different. There is a larger contact patch, more grip, less opportunity for the wheel/tread to slip and apply off axis load to steering arm.

 

As a side note, the +2 setup ride quality has not changed much at all, and we have pretty rough streets in Santa Fe.

 

Circumference of wheel tire combo is no different. There is a larger contact patch, more grip, less opportunity for the wheel/tread to slip and apply off axis load to steering arm

It is not that the overall diameter is larger, but the angular momentum required is greater since the overall mass has been moved farther from the center of the circle, therefore it requires more force to overcome inertia.

 

I think you are on to somethng there. The technical reasons notwithstanding, it makes the car a little more pleasant to drive and I dare say, safer as well. Which is good for my wife's DD.

 

No pix yet, but it's nothing special. Most people have seen the JCW R105 silver on a stock height MCS.

I have always found my wheels, new and used, online rather than locally. These used R105s came from California and yes, they are heavier than I would want normally if it were my my DD, but it's my wife's car. I would usually go for a 17x7 wheel that weighs ~17-18 lbs. and sticky tires like Bridgestones RE01R or the cheaper Falken RT615. It's hard to beat TireRack or EdgeRacing.com

 

I think rotational mass is the proper term.

 

True, that.

It is definitely hard to beat the NET on price and selection, so in the end, I may end up purchasing the set online and having Amigo Tire swap them out...

As you expressed - I am trying to find the lightest wheel/tire combo without having to sell my sister, so it looks like some 17" or 18" Black O.Z. Ultraleggeras w/ some Pirellis or Bridgestones. I know, I know - "everyone" has these O.Z.s.... it's just that they are kind of hard to beat for the price and weight and I like the way they look.

How much difference can this possibly make if you (actually, me w/ the O.Z.s) are using a much lighter wheel/tire combo - the OEM 16" RF tire/wheel combo has a lot of "heavy" rubber spinning around the edge of that 24.44" diameter circle. Also, if one assumes a 215 width vs. the stock 195, there is roughly a 5% difference in width impacting the contact patch, so....

 

Sorry for explaining it incorrectly, talking about its diameter. In turn I was speaking about changing its angular velocity. When i should have said its larger radius from its axis. Because a mass that is further out from its axis must, for a given angular velocity (omega), move quicker than mass closer to its axis.

 

Before I came across the R105s I was looking hard at these in 17" or 18" and they would look great with Nigel's paint color. $194 in 17", 18lbs.
http://www.edgeracing.com/images/whe...angle_zoom.jpg

 

Congratulations!!!
Enjoy the ride!