Brice-RX8

This is the first car I have had that is not nose heavy like a front drive car, so I am wondering if what I feel when braking is because of the car's even weight distribution. When I come to a stop my car feels like it is lunging a little bit, I have the clutch pushed in and just pressing the brakes with even pressure and there is a slight lung (sp?) affect. The steering well does not vibrate at all, and the car tracks straight. I am thinking it is the way it is suppose to do, the roads, or the tires are not perfectly round, what do you guys thing?

Go48

Not sure what you mean by "lunging". Lunging to me indicates a sudden movement forward. I've never experienced that with the brakes on my car, so maybe a little more descriptive info will help someone respond with some useful information.

If you mean the front of the car dips down when you press the brakes, you are probably pressing too hard on the pedal and waiting 'til the last minute to brake. This car has incredible brakes and sometimes even a slight pressure will stop the car pretty suddenly. Practice putting a lighter pressure on the pedal a little sooner than you would normally do when stopping a "normal" car.

Brice-RX8

Actually I am putting light pressure on the pedal, the lunging I am talking about seems kinda like a flat spot on a the front tires and everytime it rolls over that area you get a lung or lumpy feel, but it is only felt under light brake pedal pressure. Not sure if that is any more descriptive or not, but like I said no shaking in the steering wheel, doesn't do it with hard braking, might just be the crappy Bridgestone tires.

Go48

Could just be the small irregularities in the road surface, particularly at stopping points like traffic-light-controlled crossings, causing "tramlining". Wide tires are known to be more prone to that than the narrower, more standard tires. Check out http://www.tirerack.com for an explanation of the term "tramlining".

To test for this possibility, find a perfectly flat-smooth surface, like a freshly paved parking lot, and see if it still does the "lunging" on that surface..

Brice-RX8

Thanks I was thinking that could be the possibility just wanted to get some insite, I will try braking different ways on fresh pavement and see what goes on there.

Go48

Here's the link to the TireRack article:

http://www.tirerack.com/tires/tirete...tramlining.jsp

gc1bflyr

You may be experiencing what some folks refer to as "warped rotors". I have a similar situation with my 8. I did a dumb thing by setting the handbrake after a series of high speed braking demonstrations. That was 20K or so miles ago & the occasional bumping to a stop under light pedal pressure is still there. It is not consistent. I think it depends on whether or not the "bumps" are in phase when I apply the brakes. I read somewhere that there are very few cases of warped rotors and that the actual cause is the change in hardness of the rotor when the heating/cooling is not uniform, like when you get the rotors really hot and then clamp the brakes while the really hot rotors are cooling. The uneven cooling that results changes the crystal structure of the steel where the cooling is fastest (or something like that). It isn't that bothersome so I haven't fixed it. Mazda dealer claims not to be able to duplicate it. Since it isn't consistent I tend to believe them.

dannobre

iTrader: (3)

Usually that " warped rotors " feel is uneven deposits of brake pad material on the roror surface. If you bed your brakes....it will probably go away....

EyeBall Fixer...(o)(x)

Please explain?

"bed your brakes"

Go48

How about a guess? You turn the rotors to rough them up and then "break in" the pads by avoiding panic-like stops for a period of time.

EyeBall Fixer...(o)(x)

okey-dokey...
Think i got it...
Thanks Go48

Go48

You're welcome, but note that this is a guess.

mlx8

There is a good "general" article in the latest (June '05) Grassroots MotorSports on brakes and solving brake problems, including a summary of "adherent" vs. abrasive friction etc. and vibration problems

Brice-RX8

Thanks for all the insights guys, I think I will try the bedding in procedure and see how that goes, if it doesn't make it better then to the dealership. By the way under heavy braking everything is smooth and quick stopping

gc1bflyr

http://www.stoptech.com/whitepapers/bedintheory.htm
A good article on brakes and theory as well as bedding of same. Much thanks for the "correction".

Razz1

Or you could just put them under the covers with you like Michele Jackson.