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I want to put some 19's on my BMW coupe, but dont want to slow down the car

2007-06-19 17:51:57 · 12 answers · asked by Anonymous in Cars & Transportation Car Makes BMW

12 answers

Contrary to popular believe, increasing rim size does not increase or decrease the speed of your car due to it's diameter. Whether you use a stock 15-inch rim or an over-the-top 19-inch rims, as long as you keep to the plus-sizing rules (adjusting tire size to suit the rim), the rotational diameter of the tire will remain the same. This is also very important if you want to have accurate readings on your speedometer.

Now, with that out of the way, other factors can affect your speed. Increasing the width of the tires will increase the rolling resistance as well as air-resistance. Having a larger wheel usually also means a heavier wheel. This increases the inertia of the wheel, requiring more energy to accelerate and decelerate (brake effort).

To add to that, a heavier wheel also increases the total unsprung weight of your axle (the weight of your hub, tire, wheel, brake assembly), slowing suspension reaction/handing.

2007-06-19 21:40:39 · answer #1 · answered by Snowie 6 · 1 1

Wow, ask a question and get a bunch of 1/2 or less informed answers. To answer, a larger rim will not by itself slow the car but here are things to be aware of.

To keep your speedo true you need to ensure that the tires outside diameter is exactly the same as OEM. Any good tire shop can help with this. Also keep the tire width consistant with OEM to maintain appropriate rolling resistance. Wider will roll with more resistance, but will corner better...but will also likely interfere with body and or suspension components.

If you go larger, get lighter. Larger, in and of itself doesn't have to mean heavier. An 18 inch M -parallel series wheel will be lighter than a 15 inch honeycomb wheel. If your rim is heavier than your original, it will be have some adverse effects, but it isn't like you are adding 10 lbs per wheel. Some of the weight gain will be offset by a lower profile tire.

Smaller sidewall always yields a harsher ride and a bigger risk of rim damage from potholes or curbs. It is rare to see curb rash on a normal 15 inch wheel, but you see it on 18s all the time.

The larger rigid wheel will actually yield better cornering due to a lower flex in the sidewall of the tire...but it will put more stress on the tire and increase tire wear. With a 15 inch rim you will have in the area of 6 inches of sidewall. With a 18 inch rim it will be approximately 1/2 of that....so you can see there would be more lateral stiffness with a larger rim.

You also need to pay strict attention to hub offset and centerbore diameter. Keep the offset and centerbore size the same or you will have interference or vibration issues respectively.

All that being said, anything larger than a 17 inch wheel on a BMW is a major compromise of the balance of the car in performance and appearance. Your car deserves better than being turned into a Ghetto cruiser.

2007-06-21 09:41:37 · answer #2 · answered by DH1 4 · 0 0

puttin a bigger heavy wheels will slow you down of course as what other users said, it will need power to turn em.. But if you look into HRE forged rims aka known as BMW rims they will actually make it a little fast.. You will feel the difference onces u added rims..ive change three rims on my car for a yr and felt the dirrerent of it ... especially when acelleration.. goodluck but check out HRE rims.. they lightweight but since u drive a beamer im sure u get your money for maintenance and style.. Schoots

2007-06-20 04:33:12 · answer #3 · answered by Pimpin on 18z 2 · 0 0

Actually big rims could do one of two things.

If they are lightweight premium rims, Like off of an M3, Your car will actually go faster because of the increased distance per rotation of your tire. But they have to be the same weight or less of your original rims. Oh, if they meet those standards, you will have to get your speedometer re calibrated. It usually goes off about 5 miles per hour, more or less.

If they are heavier, the exact opposite happens. You'll go slower and it will suck horsepower because it takes more force to turn the wheels. Also needs a recalibration.

2007-06-20 01:10:34 · answer #4 · answered by Russki parin 2 · 0 1

Bigger rims add to the unsprung weight of the car and have an adverse effect on the overall performance.

2007-06-20 01:01:26 · answer #5 · answered by Anonymous · 1 0

well yes they will slow it down, but if youre willing to put out alot of money to get the most expensive/lightest wheels it will make up for the difference in size. in any case though, the amount that it will slow down will probably be so slight you wont really feel a difference.

2007-06-20 00:56:27 · answer #6 · answered by Britt 2 · 0 0

If the outer circumference of the wheel is increased, it increases the distance the wheel travels in one revolution, but it takes more power to turn it. They don't affect speed as much as they affect the accuracy of the speedometer and odometer which take their input from the drive shaft.

2007-06-20 01:11:18 · answer #7 · answered by Anonymous · 2 1

There more mass in them wheels. It will affect every thing. Performance,braking,handling and fuel mileage. Plus it makes the car look stupid.

2007-06-20 00:55:49 · answer #8 · answered by Anonymous · 0 0

Only if it's big in width. Too wide cause drag and heavy vibration on the steering wheel.

2007-06-20 01:02:17 · answer #9 · answered by Tim V 1 · 0 1

the "taller" the rim the more top end speed, sacrifices low end power, but probably of little consequence.

2007-06-20 00:57:06 · answer #10 · answered by dad 4 · 0 1

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