We have been running an 18 x 7 inch wheel on the front of a car running Modified Sport. Using Mickey Thompson 26.5 x 9 x 18, we have discovered that the tires have a very large contact patch and cause the car to become unstable above 160. In fact, we spun the car at 188 it became so loose.
When we had the wheels made, we contacted M/T and used their recommended width for that tire. Going back and forth with their tech representative, they insist we do not have an issue with the wide contact patch.
At the USFRA meet last week, we ran a second, better matched set of M/Ts. At 164 our driver backed out of the run, as the front end was unstable, in fact he said he could feel the instability at 80 MPH. As an experiment, we changed the front wheels and tires to the stock Bridgestones, with 45 pounds of pressure to increase the crown on the tire and lessen the contact patch, we ran 204, with no stability problems.
We are now looking at either mounting the 26.5 on a narrower wheel, such as 5 inches (not recommended or approved by M/T), or changing the a 15 inch wheel to get more tire options, such as running Goodyear Front runners.
Either way, I need suggestions on wheel manufacturers. The original company that made our existing set is no longer available.
I would also appreciate any input on who is running the 26.5 M/T, and how they make them work on their cars.
Any suggestions are appreciated.
Thank you,
Kevin Marsh
Hi Kevin, just a thought I had when reading your post. I remember doing a little experiment, nothing to do with racing, back in the mid eighties. In the UK we get a lot of snow and where I lived, it was very hilly. I did the usual with my car as you do when you're young, a few mods here wide wheels etc.
However, when it snowed the car was like Bambi on the ice.
I could not get traction to climb the hills and as for braking, forget it.
Then whilst chatting to a colleague at work about why my car was at home he replied, put the stock wheels and tyres on and explained that the wider surface area of the tyre meant that there was no contact with the solid road surface beneath the snow and that a narrow tyre would, in effect plough through the snow and give me the traction I needed. I fit the old wheels and tires and it worked! I could drive the car, still with caution but it was a lot better.
Back to the thought, if the salt surface is loose, would a wider tyre on the salt have the same effect as on the snow and did the Bridgestones with 45 pounds of pressure produce the same results I got when I changed to narrow tires?
