johnnymk

On Monster Garage several months ago, an Escalade was modified with all sorts of equipment, which definitely made it heavier than stock.

Jesse had a large set of wheels/tires put on the vehicle.
He also had a set of expensive rotors/calipers installed because he was concerned about the additional weight of the larger wheel/tire combination.

This was the first time that I had seen this brought up.

Obviously, the Gross Vehicle Weight Rating(GVWR) doesn't change by adding larger tires or wheels, because they are not usually the least rated component on a vehicle like this. The reserve weight (carrying capacity) definitely is reduced, though.

Has anyone seen an article concerning this or know anyone who has gigantic wheels and the brakes are not working correctly afterwards?

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jase71

Not only are the larger wheels gnerally heavier, but the weight is farther out from the axle, which means more inertia to overcome, making it both harder to accellerate, and harder to stop the larger wheels.

Think of a playground merry-go-round. Weight closer to the center makes it easier to spin, and easier to stop. Shift that weight to the outside, and it's harder to push, and harder to slow down. Large wheels add weight to the outside.

It's a big issue on the Miata forums, because it's such a light little car that even small changes will have very noticeable effects. Most of the hardcore folks run 15" wheels and tires. 14" would be more common than it is if the performance tire selection was better in that size. But going to a 16" or 17" starts to have negative effects that some people will notice, it'll seem less "peppy".

The bigger issue, though, at least for Miatas, is the unsprung weight of the larger wheels. The weight of large wheels can wreck the handling pretty easily.

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Bires

Wouldn't the mods also throw off the front/rear brake-force ratio, causing the vehicle to dip or lift upon braking?

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Jabberwocky

If you ask me, most SUVs need better brakes period. In any case, bigger brakes don't always mean better, just means that it is more resistent to fade. They probably did it just for the looks. A more aggressive brake compound would have done the same thing.

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johnnymk

I believe they used larger brakes front and rear, assuming the vehicle had discs front and rear.

They may have used an adjustable proportioning valve. However, I am not sure how that affects the antiskid feature, especially with the larger diameter tires, which also affects the speedometer reading which affects trans shift points and on and on.

johnnymk

No, I am looking into 17 inch wheels and tires for my pickup. But they are soooo expensive!!

And guess what, NTB, a subsidiary of Sears is selling 20 inch wheels now.

Tommy Boomfiger

i know too many people with 18"+ rims that warp thier rotors within weeks of installing thier rims.

if youre going to put some wide open spoke rims on your car, the stock brakes are going to look tiny. i just saw a civic with at least 17s on it, but they were open. you could see the whole wheel well and suspension. looked worse than stock rims.

johnnymk

WOW!! That's something I wouldn't have thought could be a problem, but it makes sense.

Nanotech9

actually - better pads wont necessarily overcome the fact that you need bigger rotors - bigger rotors dissapate heat much faster than smaller rotors. if you put too large of a wheel / tire and have too much mass to stop, stock rotors can overheat - both warping the rotor, and boiling the brake fluid causing extreme brake fade.

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Tommy Boomfiger

i dont know if anyone read my post as saying needing better brake pads, i meant the rotors, pads, calipers, etc. front and back. going from 16s to 18s probably will be fine on your brakes, but i cant be positive. but when you are doing +1s or +2s stock brakes will probably be fine. if you are doing +4s, definately upgrade your brakes.

actually if you get better pads without bigger rotors, you will probably just warp your rotors faster because they usually produce more friction and more heat.

Tommy Boomfiger

the last set of rotors i bought were slotted and cross drilled and i liked them a lot, but i remember a post by apex about how cross drilled and slotted tend to develop micro cracks in the surface because they arent made to be used for long periods of time. i think my next rotors are going to be just slotted.

http://www.gotapex.com/forums/showth...#postid=344472

Apex

SOME crossdrilled rotors tend to.

The main problem is not the ones that were designed for crossdrilling (ie. Porsche OEM), with each hole dished out, and reinforced. The problem is the ones that are not.

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Tommy Boomfiger

so what rotors can i get for a e36 bimmer that has reinforced holes? i know that some porsche rotors are made by zimmerman and ive seen those go from about $150 to over 500 a pair.

EDIT:
i found some Zimmerman Cross-Drilled for e36 vented

fronts: $134
rear: $104

thats not bad at all. i think i spent around 150 for my last cross drilled and slotted rotors (front and rear) and that was at 50% off.

johnnymk

Talking about rotors, I have seen some pretty cheaply made ones on smaller cars. I wonder if flexing could occur while going around turns with the larger tire/wheel combos? Especially on front wheel drive cars?

EDIT: After thinking about it, the lugs are attached to the hub and not directly to the rotor, so that may not be a possibility, unless the hub were cheaply built, which would probably fail first.

Nanotech9

ATE makes a good "Powerdisc" slotted rotor for many BMW models. Lots of auto-crossers and mild road course racers use the ATE disc - its vented and slotted - doesnt reduce the surface area as much as drilling does, but still releases gasses produced by the heat from friction. On the e30 they run about $70 for a set of Fronts.

shoeish

All four discs on newer chevy/gmc trucks/large suv's are greater than 13". My 3/4 ton truck has never ran out of brake, even when pulling a trailer or with a load in the bed. It runs out of traction and triggers the anti-lock before I run out of brake.

Also, the chevy/gmc trucks have automatic load sensing and brake proportioning systems to help balance the brakes out from front to back.

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Showtime

Bigger rims = to faster top speed generally speaking. A little slower off the line but faster on top end. The new viper powered Dodge truck comes standard with 22's.
My 23's ate up the brake pads for breakfast. It took longer to stop. I prefer the stock 17's for saving dough and a smoother ride.

-jel

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johnnymk

I was talking to a guy yesterday I used to work with.

He has a 2002 Chrysler 300 which has 17" wheels and tires. He said that his first set of brakes lasted 16,000 miles. He figured that it was the larger wheels that was causing the premature brake wear. He said that Chrysler recently corrected the problem by adding larger rotors, calipers and master cylinder.

He was trying to figure what would be the easiest way to correct the problem. So he changed the rotors to the ones which are drilled and has grooves directing the heat toward the front of the car, not rearward as many do. He said that it cost $200 and solved the problem.

Another potential problem I didn't even consider that he brought up: When the brakes get very hot, the wheel bearing grease can melt and ooze out of the cups, creating one heck of a mess and a very dangerous situation.