SC 94 Braking System with New Tires/Rims Combo

Bird of Prey 94

Registered User
I recently put on new tires and rims on my Tbird SC 94. The tire/rim size is Nippon 17 inch rims and Nitto 555P245/45ZR17-89W.

I notice when I do high speed braking, the car acts like it does not want to stop. I realize I need too much room to stop the car. An example of this is when I am doing about 70+mph and I have to slow down quickly in ongoing traffic.

Would the tire/rim combination negatively affect the braking characteristics? I have ABS and traction control and I thought this would improve my braking but I am getting the complete opposite.

Has anyone experienced this?

I am not stopping as confidently as I would like to.
:(
 
Your tire and wheel combination is most likely heavier than stock, which is more rotating mass to stop.

I noticed my car has decreased braking ability after my 17" tire upgrade.
 
a few magazines have tested that same theory and found that many times the larger tire and wheel combos can lead to worse braking and acceleration times.
 
Thanks everyone for your comments. I really do appreciate your responses. However, tell me something, is anyone familiar with the differences of height between the tires and wheel combination (i.e. 25 1/2" rim and tire height compared to 26" rim and tire height). What effect will the difference have on my braking ability?
 
The difference in tire diameter...

A difference in tire diameter will affect your speedometer. Your speedometer readings will be off by a certain percentage.

There as a website I saw once through the Miata.net that calculated tire height.

Also running a slightly shorter tire will increase your gearing ratio (numerically higher) and give you higher revs at any given speed in any given gear. This can actually increase your acceleration (like installing numerically higher gears), Whereas a bigger than stock diameter tire will numerically decrease gearing.

I bet the 25.5" tall tires compared to the stock 26.6" tires look pretty small in your wheel wells and the fender gap looks huge.

I upgraded my rims and tires to 255-50ZR-17 tires. They are 27" overall. So a touch taller than stock. Which means I made my gearing taller (reduced acceleration).

Also I have noticed a slight drop in braking ability. This is due to rotating mass. most of it mainly due to the increased wieght of the bigger tire. But I've also read about the larger diameter tire having a "lever" effect on the brakes, meaning that the further the spinning weight is from the center of the hub, the greater the torque-arm effect has on it.

I've got a set of performance friction carbon metallic pads. I'd suggest at least upgrading to those to recover your braking prowess (which was never really great on a heavy car like ours, with the small undersized taurus brakes).

In order to run any of the serious braking systems, you need to upgrade to the 17" or bigger rims anyway....
 
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