floridafordguy

I'm exploring putting staggered 20" wheels on a 2011 GT, 8.5" 255 front, 10" 285 rear. Tire Rack says no problem, no issues. Dealer says bigger wheels and tires harder to stop, and recommends upgrade to Brembos. All this money is getting me closer to GT500 territory, too rich for me right now.

Anyone have any experience or advice with this? Your help is appreciated.

conejo172

I just installed almost the identical sizes on mine only difference is 275 rears. Braking seems the same to me. sounds as if the dealer wants to suck more money out of you!

siberian.mist

you wont notice much of a difference in braking if any. and id go 265/35 all around

floridafordguy

Do you recommend that so you can rotate them? Also is that a commonly available size? What brand of tire are you using?

Thanks

Sleeper_08

As it is tires that stop cars and not brakes then putting on better tires will improve your braking.

With the stock brakes you can kick in the ABS any time you want and this confirms that the tires are the limiting factor.

Of course if you then have better tires then better brakes are nice and then better tires and it never ends. I just finished my first track day on NT01 R-comps and Carbotech pads and GT500 brakes and brake duct colling. I now have a bruise on my shoulder that I think is from braking!

Norm Peterson

If the tires are not much larger OD than the OE 27-ish, I doubt you'd notice the difference. Theoretically, it does take a little more brake effort to stop a 60 lb 20" wheel/tire than a same-OD 18" wheel/tire that weighs only 53 lbs, but the difference amounts to less than 2% of the loaded car weight (a couple of 40-lb bags of kitty litter amounts to a bigger difference and yes, I am including rotational effects for the wheels/tires). Bottom line, your OE brakes will be fine in normal street driving to cover that kind of change. If you were swapping to 35" tall offroad tires, it might be a different story.

Unless you're going to go open-tracking the car or canyon-running it in the hills, there is little performance requirement for anything beyond a set of performance street pads (Hawk HPS or equivalent, which in most cases are enough better then OE replacement pads in terms of initial bite and "feel" to do as a stand-alone mod). At ~$70 per, ATE slotted rotors don't seem to develop grooves in the rotor faces as fast as the OE rotors do, which might be a consideration. Sam Strano (www.stranoparts.com, site sponsor) carries both of these items. My own order for the above items, for a car that gets driven fairly hard but isn't tracked (yet), goes out later this week.


Norm

Philostang

WHOO-HOO! Now we're talking! Before long you'll have those seats pulled out and Kirkey aluminum ones put in! It truly does never end...

To avoid being a complete thread-jacker, I do recall seeing some data figures on 60' braking distances with 18"-20" wheel swaps (on an SUV, diff. was something like 16'-20'). The difference isn't always in what you "feel" as this can be as much a function of pad compound, air in the lines, etc., as anything else. Initial bite is great and confidence inspiring, but if you're still seeing a 16' difference in braking distance you're still losing a full car-length of buffer room in an emergency stop. That's the difference between merely having puckered butt-cheeks and having blown air bags. You probably won't feel that sort of difference, until you hit something.

I'm not suggesting you get BBK's because you want to run 20" wheels. I think better rubber will suit you more than fine, and everyone should be upgrading their pad compound.

What I am saying is that there is a measurable and not-insignificant effect moving up to a heavier wheel (the size is of little importance if the wheel/tire combo weighs in roughly the same - to be picky, yes the large wheel of exact same weight is harder to stop, but now we're really being picky). The dealer may have been trying to up-sell you, but he isn't necessarily an ignorant jerk.

Best,
-j

ronniegibson1978

just remember when you go to 20's you're gonna lose a bunch of power

marcuskeeler

Why does everybody have to pull this one out every single time 20" wheels are mentioned... Sheesh.

If the tires are selected to retain the original rolling diameter and the weight of the wheel/tire remains in the same area as stock, tell me, how is that a RW power issue?
Think Forrest, think........

marcuskeeler

Not entirely right Colin. Touch the stock brake setup once or twice at speed and the ABS might show you the brakes are still there, but soon the pads give way and you find yourself pushing ever harder.

That said, running 20's with the appropriate tire size will retain the rolling diameter so your speedo will read correctly and all will remain fine. As for any extra your wheels might weigh, it's an insignificant factor. The brakes operate on both the sprung and unsprung weight, naturally, so factoring in extra momentum in the wheel rotation, even a huge increase, will be relatively negligible on the brakes as a whole.