Ok just a technical question here more on the engineering side. I am not planning any upgrades, but was just wondering what the actual differences in forces are when you put a bigger wheel on a vehicle??
Example) Rotational mass difference? Rotational moment of inertia?
Is there enough of a difference to actually justify the brake upgrade?? What is the relationship or even better, the formula, to calculate the forces and how is the radius of the wheel related?
The reason for asking is I was just having a discussion of how people are throwing on 24" or 26" wheels on a hummer h2 and not upgrading there brakes is not the best idea. The argument was that how is a slightly heavier wheel or a greater rotational mass going to make any difference when the brakes are still stopping a 9000lb vehicle either way.
Thanks.
<img src = "http://www.members.shaw.ca/shaun-ironside/sig_pic.jpg">
well im not sure how big the brakes come on a hummer but people that put like 22 on their mustangs and 20s on the cav and all need to upgrade the brakes. now you dont have to but its very smart. your stopping time is greatly increased. also you are going to go through pads and rotors like crazy.
the 17's on my car didnt effect the brakes at all, doenst wear faster and hasnt hurt the rotors....if i went bigger it probably would be a very smart idea to upgrade the brakes (although im doing it anyway in about a month)....sadly i bet most thosej people who go from 17's to like 24's on an suv dont touch em
theres not a need, however it can help tremendously.
especially if you get 17's that are up to 5lbs heavier than stock.
so far it keeps getting better and better.
i;ve had 17's and stock brakes, then 17;s and a variety of stock sized upgrades, then 17's with baers 13's, all of these were with nitto 450;s that are A in traction rating.
today i finally got my neogens, and they are a AA traction rating...
heilige shcisse. talk about great grip.
if you can, i would.
also view this page on baers site...
http://baer.com/baer/news/img/Truck_SUV_Performance_OctNov2003.pdf
deals with the improvement with suv;s
This really depends on the weight of the wheel. There are 17's out there that weigh quite a bit less than the stock 16's so those wouldn't make any difference. Of course, if you got those sorts of wheels then one would assume you had performance in mind and would be upgrading the brakes regardless.
Most larger wheels do weigh more. On top of the extra weight is the fact that the weight is concentrated further away from the center of rotation. This means there is more momentum built up and more energy to be absorbed in order to stop them.
In my opinion, the stock brakes aren't good enough for performance-minded driving even with stock wheels, though they're adequate for your average driver whose not trying to push them. They'll perform ok in a single emergency stop and there shouldn't be any need for more than one in the span of 10 minutes or so.
With that said, putting bigger wheels on quickly shows the deficiencies of the stock brakes. You will have longer stopping distances. If you're the type of driver who generally follows too close or are a late braker, this will cause you problems.
So I say yes... even if it's just a matter of getting better pads with more grip and better fade-resistance, I think a brake upgrade should go hand in hand with bigger wheels.
There's no need for a big brake upgrade on anything less than 19's, but upgrading the stock pads should be a given.
It's a small price to pay to still be able to stop properly.
Well it always seems to be the consensus that when you are upgrading to a significantly larger size wheel above stock that you should upgrade your brakes at the same time. Usually the reasons are just like everyone is saying.......its the SAFE and SMART thing to do.
I read that Baer article and the only real numbers they have posted there is a reduction in stopping distance of 20 feet from 60mph and a reduction of 50 feet from 90mph.
But these numbers are really irrelivant since there is no relation to wheel weight or size to compare to.
I am just really curious to know actual numbers. I know there are formulae that would be able to compute roughly what the actual force required to stop based on pad surface area corresponding to diameter of rotor and contact area of pad. In addition the relation to the inertia generated by rotating mass of different sized diameter and weight wheels.
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The hawk pads I have heard a lot of good things about. And they wouldn't break your bank either, last I saw they were less than 70 dollars for the set of front pads.
I'll have a sig someday....................
Scorpian: The Baer site used to list stopping distances for some SUV with stock wheels... when with bigger wheels (longer distance)... then with the bigger wheels and their brake upgrade... which ended up being shorter than the original setup.
ScorpionZ24 wrote:But these numbers are really irrelivant since there is no relation to wheel weight or size to compare to.
the first part of the article says the truck comes with 16's
then it says when upgraded to 20s.
so it states what the difference is.
each car and such is gonna be different. theres no real set determinant for every vehicle. that would also have to factor in your brake pad condition, how many pistons, what condition the brake fluid is.
there are way to many extra variables besides pad size that are gonna be factors.
if you wanna know exact figures, best bet is to get a car, test before and after and compare results.
I have 18's on my car i want to upgrade the brake but as of right now i am not having any problems with stopping. But it can be said i don't drive that hard to warrant new brake. Most people going with bigger wheel are no really doing it for performance, more for looks. Personally when i get the money i will be doing a rear disk conversion before i do a front big brake upgrade.
2004 Grand Prix GTP (Competition Group)
SOLD-->1999 Z24 5M-#30 to register on JBO
"You can please some of the people some of the time but you can't please all the people'
all the time
i would recommend doing the front big brake upgrade first. your front brakes do between 65-80 percent of your stopping, so those are the ones you should upgrade first.
also, it helps to know the weight of wheels. like said before, some 17s are lighter then stock wheels. i know that my 17's weigh about 24lbs each. i dont know how much it weighs with the tire though. somebody posted elswhere that the stock 16" wheel and tire weighs about 40-42 lbs, so my 17" setup is roughly the same weight.
Land Pirates sail the open roads
DISCLAIMER: If anything I say offends you, I don't care..wear a helmet. Also, the information
I post is what I know to the best of my knowledge. If I am wrong, please correct me so that
others as well as myself may learn.
Premium sinc 6-17-04
Even if the 17's weigh the same as the stock wheels, the location of the weight is critical when dealing with momentum.
Of course, that 1" isn't going to be a world of difference but it's still going to have more energy to bleed off.
exactly, which is why since i need to replace my brakes im doing oem size upgrades. better rotors and pads. that 1" isnt going to warrant me spending 1k for a big brake upgrade.
Land Pirates sail the open roads
DISCLAIMER: If anything I say offends you, I don't care..wear a helmet. Also, the information
I post is what I know to the best of my knowledge. If I am wrong, please correct me so that
others as well as myself may learn.
Premium sinc 6-17-04
land pirates cavalier wrote:i would recommend doing the front big brake upgrade first. your front brakes do between 65-80 percent of your stopping, so those are the ones you should upgrade first.
.
That can be argued. Some will say yes others will say not to what i want to do. But i have seen the benefit both side and for me i would rather do the rear disk conversion.
2004 Grand Prix GTP (Competition Group)
SOLD-->1999 Z24 5M-
#30 to register on
JBO
"You can please some of the people some of the time but you can't please all the people'
all the time
true- it is completely up to you as far as which one you do first
im thinking more of a safety/practical side of it. the front big brakes will let you stop better then upgrading the rear ones first. but yes- its all your choice
Land Pirates sail the open roads
DISCLAIMER: If anything I say offends you, I don't care..wear a helmet. Also, the information
I post is what I know to the best of my knowledge. If I am wrong, please correct me so that
others as well as myself may learn.
Premium sinc 6-17-04
I noticed a decrease in the abilities of the stock system when i went to 17" rims and tires. unless i jabbed the brakes real hard the tires have never engaged the ABS. so if i was slowing down and braking at the same time then had to abruptly chane the brake pressure nothing would change. scary! there could be a coralation(sp) between the traction of the tire and the abilities as well. since tires that grip better will lock up later than stock. also ,muffins, go to tirerack.com. in thier tech articles AA traction rating is wet traction rating not dry.
Traction Grades
UTQG Traction Grades are based on the tire's straight line wet coefficient of traction as the tire skids across the specified test surfaces. The UTQG traction test does not evaluate dry braking, dry cornering, wet cornering, or high speed hydroplaning resistance.
The Traction Grade is determined by installing properly inflated test tires on the instrumented axle of a "skid trailer." The skid trailer is pulled behind a truck at a constant 40 mph over wet asphalt and wet concrete test surfaces. Its brakes are momentarily locked and the axle sensors measure the tire's coefficient of friction (braking g forces) as it slides. Since this test evaluates a sliding tire at a constant 40 mph, it places more emphasis on the tire's tread compound and less emphasis on its tread design.
In 1997, the UTQG Traction Grades were revised to provide a new category of AA for the highest performing tires in addition to the earlier A, B and C grades. Previously the A grade h ad been the highest available and was awarded to tires that offered wet coefficients of traction above 0.47 g on asphalt and 0.35 g on concrete. Today the grades and their traction coefficients are as follows:
The treadwear rating will give you a better indicator of the dry traction.
land pirates cavalier wrote:true- it is completely up to you as far as which one you do first
im thinking more of a safety/practical side of it. the front big brakes will let you stop better then upgrading the rear ones first. but yes- its all your choice
From other thing i have read it helps with the rear disk conversion. Anything that will help you stop sooner is good and safe. Also, i know a Big brake kit up front will not help me because when i want to throw on some 14" rims for track the brake kit is not going to help me. The most i can do is upgrade the rotors and brakes which is not that expensive to do.
2004 Grand Prix GTP (Competition Group)
SOLD-->1999 Z24 5M-
#30 to register on
JBO
"You can please some of the people some of the time but you can't please all the people'
all the time
it's just being straight up practical, every time i see a shiny 20"+ chome blinger roll onto the lift, zip off the lug nuts, grab one and then say holy **** that big fat mother is hot. once there was this suburban that came in for a brake job, 24" davinci wheels on it and they were johnny blazin hot....lugs, hubs, caliper, pads, needed two ove' gloves.
go ahead and put some chrome on the stock brakes, it will keep the $$$ in my pocket.
CAR GODS MADE THE 1.6 SOHC TO MAKE US 2.2 OHV GUYS FEEL BETTER.
After 30+ years experience with car & truck repair, I can say that the size and weight of the wheel makes little or no difference in brake performance, providing the overall tire diameter is the same, or near stock.
Any brake upgrade is good, but not necessary unless you drive like an A55hole. I believe that your personal driving habits are more a contributing factor to brake fade, or failure, than the size of your rims or tires.
Just my .02
WelderJeffO
Jeff O wrote:After 30+ years experience with car & truck repair, I can say that the size and weight of the wheel makes little or no difference in brake performance, providing the overall tire diameter is the same, or near stock.
Any brake upgrade is good, but not necessary unless you drive like an A55hole. I believe that your personal driving habits are more a contributing factor to brake fade, or failure, than the size of your rims or tires.
Just my .02
Basic physics will show you that adding more rotating mass and concentrating that mass further from the center of rotation will give the wheels more momentum at the same speeds. This means there is more energy that needs to be bled off while braking. This means the brakes are being worked harder than they were before and since our stock brakes are barely adequate to begin with, it means you should do some sort of upgrade.
I don't really see how your 30 years of repair experience comes into play. Do you test stopping distances when repairing cars?
Jeff O wrote:After 30+ years experience with car & truck repair, I can say that the size and weight of the wheel makes little or no difference in brake performance, providing the overall tire diameter is the same, or near stock.
Any brake upgrade is good, but not necessary unless you drive like an A55hole. I believe that your personal driving habits are more a contributing factor to brake fade, or failure, than the size of your rims or tires.
Just my .02
disagree to the fullest there.
you just basically stated that if we get a chrome solid steel wheel which is heavier than stock by far, maybe 10-20lbs per wheel and add the tires to make it the SAME rolling diameter as stock, then it will not affect braking, however with 30 years of experience, you;re overlooking the fact.....well law of physics of kinetic energy.
things in motion stay in motion unless a force acts upon it.
think about a d lineman and a reciever in football. if i'm sprinting at someone, with the ball and make contact with a guy 180 lbs, the larger object will lose momentum but still have some to carry it forward a decent ways more.
if the reciever who is 150 lbs hits the 180lbs target, he will more than likely be stopped in his tracks. if he does go forwards, it wont be nearly as much momentum or distance as i did.
same for brakes. heavier wheels take longer to stop.
like said above and below you, when the bulk of the weight moves to the outside of the wheel, no matter if its the same wheel diameter overall, it will be harder to stop.
this is ALREADY noted on SUV's and many cars where adding wheels and tires in plus sizing (which means keeping the overall diameter the same, but going up in wheel size and reducing tire sidewall size) have INCREASED STOPPING DISTANCES.
hence a need to upgrade braking systems.
car and truck repair is one thing, brake and traction systems testing, R&D, is another.
some things for you to read.
about midpage, labelled the "wheels of fortune"
http://www.autocrossracer.com/wheelsandtires.htm
<img src="http://www.lingenfelter.com/Merchant2/graphics/00000001/product_images/brakebkwb.jpg">
or
Brake Systems: Oem & Racing Brake Technology by Mike Mavrig1An, Mike Mavrigian, Larry W. Carley
http://www.amazon.com/exec/obidos/tg/detail/-/1557882819/qid=1116257904/sr=8-2/ref=sr_8_xs_ap_i2_xgl14/103-3979771-0496610?v=glance&s=books&n=507846
i;ve got both books and i know its covered in there repeatedly.
