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Question, would 19'' wheels cause my car to brake differently?

Hello,

I just picked up a Five Axis FR-S and it has the S5:F 19" staggered wheels on it. The brake responds/feel isn't the same as a stock FR-S. You have to press the brake pedal so hard to get the car to stop.

The GM drove my FR-S and a stock FR-S back to back. He said it feels different but my car still stops so there isn't a problem. He said he spoke with the service team and the wheels have more mass so the car wouldn't feel the same as a stock FR-S with 17" wheels. Is this true?

I have had 16", 17" and 18" wheels on other cars I have owned and the brakes never reacted like this. Any advise/help would be appreciated.

Update: I just installed the stock wheels and took it for a ride. No change, there is something wrong with the brake system for sure.
the pedal is hard almost like manual brakes. you have to apply a lot of force with your foot to stop. No you don't have to put it to the floor, half way maybe. the rotors don't seem warped. I ask a friend and he said it could be the brake booster.

Update 2: GM wrote me an email saying he was ordering me new brake pads, rotors and they would bleed the brake lines. I will update again when the new parts are installed.

True, more rotating, unsprung mass, and depending on overall diameter, the mass is probably moved farther out, increasing the inertia. Same principal as a flywheel, larger diameter and heavier, is harder to get spinning and to stop spinning...object in motion tends to stay in motion.

Quote:

Originally Posted by Gunman (Post 974762)

I just installed the stock wheels and took it for a ride. No change, there is something wrong with the brake system for sure.

Quote:

Originally Posted by Mr.Zoolittle (Post 974926)

I just installed the stock wheels and took it for a ride. No change, there is something wrong with the brake system for sure.

How does the brake application feel? I know that you said the brakes require a great deal of pressure to get them to bite and stop the car, but does the braked pedal feel mushy when depressed? Or do you have to put the pedal completely to the floor to get it stop?

It's newton's second law of motion, the heavier and larger 19" wheel will always be harder to slow down than a 17" wheel.

Agree with @FM Wheels on this I would personally not put any wheels larger 18" on the FR-S.

the pedal is hard almost like manual brakes. you have to apply a lot of force with you foot to stop. No you don't have to put it to the floor, half way maybe. the rotors don't seem warped. I ask a friend and he said it could be the brake booster.

I just installed the stock wheels and took it for a ride. No change, there is something wrong with the brake system for sure. also the pedal is hard. you have to apply a lot of force with you foot to stop. You don't have to put it to the floor, half way maybe. the rotors don't seem warped. I ask a friend and he said it could be the brake booster.

Hmm, faulty brake booster? air in the lines? cheapest thing to do is to bleed the brakes.

i think that the effect of unsprung weights and rotating mass is given too much consideration compared to its objective effect

Quote:

Originally Posted by Mr.Zoolittle (Post 975129)

Quote:

Originally Posted by FM Wheels (Post 975139)

Hmm, faulty brake booster? air in the lines? cheapest thing to do is to bleed the brakes.

What @FM Wheels said. Bleed and see if air got in there somehow. If the brake booster is gone you will hear a "whiiiiiishhhhhhh" sounds when you set on the brakes.

Vacuum brake boosters work off manual brake pedal force as well as engine vacuum (which pull diaphrams to create extra boost for brake pressure), if your booster was not working, you wouldn't stop well at all. it would feel like manual brakes. (if you ever driven a car with this)

All in all, im pretty sure this is almost like the placebo effect.

You did notice a difference in braking with the 19" wheels, this is definitely a given, just like others have posted. Added rotational mass to EACH hub will definitely need additional effort to stop the car that was designed with 17" alloys.

Compared it to a stock FRS with a GM who also felt the difference, same with technicians. You are now AWARE that it is braking slightly different.

Now you go home and swap stock wheels back on and the car still feels different, are you sure? Or are you stuck on it braking differently with the 19" wheels that now, you feel like there is a problem with the car's braking system, even after switching back to stock wheels.:slap:

Now, if there was air in the braking system, you would experience a very soft pedal, or a "spongy/mushy" brake pedal feel. You have already stated that it requires more force to stop, so we can rule this one out.

I'm just saying, that maybe its in your head? Its hard to say this since I haven't driven your ride, you could actually have a problem.

just my .02 no thread crapping, all in good name. (not like im trying to up my post count or something):thumbup:

If the pedal is hard, bleeding the brakes won't do anything.

Are the pads glazed over? After I overheated my OEM pads it took more pedal force to stop the car than before, and when I took them out they were really glazed/shiny.

If they are and the car was purchased new I would be asking the dealership how this happened since a PDI drive shouldn't be pushing the car hard enough to overheat/glaze the pads like that.