19th February 2008, 05:36
M5 Expert (>4000)
Join Date: Aug 2002
Location: Raleigh, NC
2001 M5 LeMans Blue
Thanked 1,158 Times in 749 Posts
Originally Posted by bimmernut1
The interesting part of the graph to me is how steep the curve is and how fast the grip drops off at temps below approximatly 120 degF. I haven't tried to extrapolate down to to the 50-60 degF range. But just eyeballing the chart seems to show the grip could be as low as 60-70%.
I guess that's not a big surprise but still good to be aware of.
With summer tires there is a huge step-function like drop off in grip as you approach the glass transition temperature of the compound (which is essentially a phase change). This typically is near and below ~35F. Hence the reason you never want to run them in snow/ice since traction is essentially zero under those conditions. You also want to be aware of the loss of grip when driving on dry pavement in cold weather too. Don't overestimate the potential traction you think is there. When you look at R-compound tires, temperatures below 35F or so can actually damage the tire's rubber compound. Toyo has a warning out for their R-comp tires about storing and/or attempting to use them when temps are below 35F. Also as a regular summer tire ages after many heat cycles, the sensitivity to loss of grip is more apparent as a function of temperature.
You can easily see this with summer tires on the M5 and trying to launch the car. If the ambient temp is 90F versus 50F, there is a huge difference in the launching rpm to be used and the rate at which you can feed throttle in 1st gear without spinning too much. Drop that temp to 30F, and it is yet again a huge difference from 50F.
2001 M5 LeMans Blue/Silverstone
Dinan: springs, Konis, rear sway bar, monoball bushings, and exhaust;
Ground Control camber plates, Stoptech front BBK, Brake ducts opened,
Evolve AlphaN tune,
OE 9.5" rear wheels all around & 275/35-18 Pilot Super Sport
2011 M3 sedan 6MT Silverstone, no sunroof!
2006 330i sport 6MT Electric Red/Black
2001 Audi S4 6MT -- for sale?
1996 Volvo 850R wagon
Last edited by CSBM5; 19th February 2008 at 05:39.