Performance loss with bigger wheels?

[Gro Harlem]

how much do those rims weigh? I chose rims that were lighter than my stock 15's and have no problems accelerating.

Also, the width of the wheel could have something to do with it. Going from a 6" to 7.5" can cause more resistance.

Also, the tire size, if it increases your overall diameter can make the gears taller which slows acceleration

[phillyMX3mayn]

after u paint the calipers red u should be fine

[Nd4SpdSe]

I noticed a huge performance loss when i went with 205 55 r 16 and steel rims..i cant wait till i wear out these tires to go back to 105 55 r 15. I used to be ableto peel out in second gear..not anymore. ..can be contributed to other factors.

Could it be that your getting better traction?

[Dave-UK-MX3-V6-SE]

To answer the SE question: In the UK there's a '94 model that came with leather/suede interior, anthracite alloys, air con, and a chaste white paintwork. Only 150 made!

About performance... I went from 205 tyres to 215, and the rolling radius slightly increased. Also the wheels themselves are indeed heavier....
So after I got these and they look amazing (in person, seriously... you gotta see them up close (or moving!!)), I'm consdering ditching them for some 16" lightweight wheels....
Argh!

[Famine]

An increase in rolling radius by approximately 1 inch will put your speedo out by nearly 8% (give or take). It will also adversely affect acceleration, but give you a marginally increased maximum speed (assuming you can get there - for the 137hp the MX-3 puts out it has a maximum speed of 141mph, due to Cd, frontal area, power and a small factoring in of weight).

Look at it this way. A 15 inch wheel with a 55mm sidewall tyre has a diameter of 19.33 inches and a circumference of 60.7 inches (1.54 metres). A 16 inch wheel with 45mm sidewall tyres has a diameter of 19.54 inches and a circumference of 61.4 inches (1.56 metres). One rotation of the hub on the larger wheels is 0.7 inches longer, meaning the engine has to do more work (or it requires more power) to turn the hub once, thus your acceleration is slower. But at maximum revs in top gear you're travelling 1.1% faster - all the components are still turning at the same rate, but your tyres are moving 1.1% further for the same amount of work.

For reference, on the above example, the 55/15 wheels rotate 31,760.5 times per hour at 30mph. On the 45/16 wheels the speedo will still read 30mph and the wheels will still rotate 31,760.5 times, but you're actually travelling at 30.3mph. Not terribly significant, you may think, but at 99.5mph you'll get 9 points and a hefty fine - and if your speedo reads 99.5mph but you're actually doing 100.6mph, you'll get an instant ban. Probably.

[ertaisi]

Is it possible to recalibrate your speedo?

[Famine]

Yes - and it should be done if you're thinking of changing your wheel sizes.

I would say that you can get a GPS system, so that you're aware of your true speed, but in the UK that wouldn't help - speedos have a certain tolerance in law of -10% (they aren't allowed to read over - like saying 33mph at 30mph), which they MUST be within. Changing your wheel size affects that and can potentially put you at risk of getting stung even at low speeds (the above example, at an indicated 30mph your speedo you could actually be doing 33mph, but the extra inaccuracy puts you within range of a speed camera calibrated to 34mph).

[Steeb]

if u have a performance loss from aftermarket wheels, your wheel and tire package are:

1. heavier than stock wheel and tire combo
2. rolling diameter is bigger than stock - tire too big
3. both 1 & 2

which makes the below true
if you have a performance gain from aftermarket wheels, your wheel and tire package are:
1. lighter than stock wheel and tire combo
2. rolling diameter is smaller than stock - tire too small
3. both 1 & 2

if you have the same rolling diameter and weight as stock with different size wheel and tire combo, your performance will not change. having bigger wheels doesnt throw off your gearing if u choose the correct tire size so u might loose performance because most aftermarket wheels are heavier than stocks. we are blessed with ugly somewhat lightweight stock wheels, which makes me prefer more expensive lightweight aftermarket wheels that i cant yet afford.

[Steeb]

something to keep in mind is with a bigger rim once you reach speed the car needs to do less work to keep this speed because of the distribution of the weight in the rims. But other then that its not a huge difference in performance.

i believe this has more to do with the fact that most cheap aftermarket wheels are much heavier than stock wheels so there is more rolling resistance when accelerating while also hurting braking performance and handling. seems like the only good thing about heavy aftermarket wheels is that they keep your car rolling longer after u let off the gas...

mitmarks, your posts are annoying and never have anything to do with the thread topic

[Dave-UK-MX3-V6-SE]

cheap aftermarket wheels

These were $1350 !!!

I accept what the problem is now... greater rolling radius plus a heavier (17in compared to 15in) wheel, with a wider tyre (215 instead of 205).

Gah.

Thanks for the advise y'all!

[Steeb]

why is your rolling diameter bigger than stock? did you choose the wrong tire size? having a wider tire doesnt give you more rolling resistance and if you choose the correct profile, it will be the correct rolling diameter as well (or close it).

what kind of wheels are they? they do look pretty nice, remind me of 57 pro's or adr's... fergot what they are called. do u have anymore pictures? how bout some side shots to show how the fitment is. what offset and width are they?

imo, 1350 isnt pocket change but its not that much for 17's. (Rotas dont count cuz they are dirt cheap everywhere you go) id set aside at least 1600-2000 for lightweight 17's without tires. my 16's on the mr2 were about 2400 when new. they weigh less than the stock wheel and tire combo even after i put wider (and in the back taller) tires.

stock aftermarket
front 195/55/15 215/45/16
rear 225/50/15 245/45/16

ive been waiting for a set of ms08's in 16's to pop up or else ill be getting a set of ssr comps for the mx3 when i can afford them.

performance parts are not cheap. choosing wheels is the same as choosing other performance parts cuz some will help others will not.

[tatsu]

Okay, there seems to be quite a bit of misunderstanding here as to why switching to a larger diameter wheel package would cause a loss of performance, particularly at higher speeds. There are two main factors at play here - the "flywheel effect" and/or a change in rolling circumference.

To explain the "flywheel effect", here is a snippet from a previous post of mine. Bear in mind that this is discussing changing the diameter of the wheel without changing the overall diameter/rolling circumference of the package:

Without getting into the various formulae, there are three basic truths: 1) it takes more energy to change the velocity of (accelerate/decelerate) a greater mass, and 2) the further from the rotational axis the mass is located, the more energy is required to change its velocity, and 3) the further away from the rotational axis the mass is located and the higher the rotational speed, the more energy is required to change the direction (I.E. to turn the wheel from side to side). Bear in mind that the bulk of the weight of a lightweight wheel and tire combo is carried around the outside diameter of the wheel rim, with the tire making up from 52 - 64% of the package in our examples above, and that going from a 15” to an 18” wheel moves some of that mass 20% further away from the rotational axis! You also need to take into account that the 18” wheel also has 20% more mass in the wheel rim because of the larger circumference, with the rest of the difference being in the wheel spokes. What this means is that with the larger wheel/tire combo, you will have poorer acceleration, braking and turn-in at speed.

If the wheel/tire package you select is heavier than stock, this effect will be magnified even more...

With regards to a larger rolling circumference, this comes about when the overall diameter of the package is taller than what you are replacing. For example, going with a 215/45-17 instead of our stock 205/55-15 (the best match would actually be a 215/40-17, FYI).

If you increase the rolling circumference of the wheel/tire package, you are actually increasing the gearing of the car, making less torque available at the wheels to accelerate from any given speed. With the example of sizes given above, you would actually put about 4% less power to the ground at a given rpm in any given gear than with the stock diameter.

For reference, here are the "upgrade" tire sizes that best match the diameter of the stock 205/55-15 size from the MX-3 GS:

225/50-15 (very slightly shorter)
205/50-16 (slightly taller)
225/45-16 (slightly taller)
215/40-17 (slightly shorter)
215/35-18 (slightly taller)

After some research at the Tire Rack, I have found several plus size tires that are the same weight or lighter than the stock 205/55-15 size of the same model. Check out the list in my other post.

So, the good news is, if you can find a plus size wheel that is the same weight as stock (I have now heard anywhere from 15 - 16 lbs.) or lighter, you should be able to put together an upgrade package that is lighter overall than a stock wheel/tire package! Lighter is definitely better!

Again looking at the Tire Rack, it should be noted that the only 18" wheels I have found in our fitment that weigh that little are:

• SSR Competition (14.0 lbs./$459 US per wheel)
  SSR GT2 (15.9 lbs./$467 US)

Both CRAZY expensive...

For 17" wheels:

• BBS RGR (16.3 lbs./$553 US)
  Kosei K1 Racing (16.3 lbs./$179 US)
  Kosei K1 TS (14.1 lbs./$199 US)
  OZ Superleggera (16.3 lbs./$280 US)
  SSR GT1 (16.5 lbs./$249 US)

Some more reasonably-priced choices here. Note that all except the Kosei K1 TS are actually marginally heavier, but they are close enough that the difference shouldn't be noticeable.

There are LOTS of 16" and 15" wheels that are significantly lighter than stock, so I won't list them here.

If you want to have a look at my previous post, which has a bit more in-depth discussion on the tradeoffs of larger diameter wheels, leaving aside weight and changes in diameter, go here.

[Flashpoint2]

SO now that we've determined what is bad, and what is good as far as wheels go, does anyone have any quantified data as to just exactly what these performance gains/losses amount to? I mean its one thing to say that having heavy wheels is bad, but just how bad is it? Because I have 17s on mine, and 215/40-17s, and I don't notice anything, except that I feel more of the imperfections in the road (read: potholes).

[tatsu]

The change in perceived performance from a change in the weight of your wheel/tire package is difficult to quantify on paper. The most effective practical test would be to time the acceleration in gear, say from 80 km/h to 120 km/h (50 mph to 75 mph for you non-metric types) in 4th and/or 5th gear over the same stretch of road under the same weather/temperature conditions, before and after the change in wheel/tire package.

This should eliminate traction as an issue (as it would be if you were timing standing-start acceleration), and would show the effect at a high rotational speed, where it should be more pronounced. It should be noted that this will also incorporate any changes in rolling resistance, wind resistance, etc.

Leaving all other effects aside, the change in torque to the road by running a different overall diameter than stock wheel/tire package can be easily quantified, because you are basically looking at torque multiplication via gearing. Here's an example using the popular 215/40-17 upgrade size:

• Stock size = 205/55-15 = overall diameter of 606.5 mm
  
  Upgrade size = 215/40-17 = overall diameter of 603.8 mm
  
  Torque change = 606.5 / 603.8 = 1.004 (approx.)

So with your wheel/tire combination, all other things being equal, you would be putting a whopping 0.4% more torque to the ground than with a stock size. Now, let's look at a hypothetical larger-than-stock package, with a 215/45-17 tire:

• Upgrade size = 215/45-17 = overall diameter of 625.3 mm
  
  Torque change = 606.5 / 625.3 = 0.970 (approx.)

With this upgrade size, all other things being equal, you would actually be putting about 3% less torque to the ground than with a stock size. Here's the theoretical change in torque to the ground, all other things being equal, with the upgrade sizes listed in my previous post:

• 225/50-15 = 0.1% more torque
  205/50-16 = 0.8% less torque
  225/45-16 = 0.4% less torque
  215/40-17 = 0.4% more torque
  215/35-18 = 0.2% less torque

Note that, worst case scenario, you would be losing nearly 1% of torque to the wheels with the 205/50-16 - hardly an earth-shaking difference, but a difference nonetheless.

Now, how do you find out how much of the difference in our timed tests at the beginning of this post can be attributed to something other than the change in torque to the ground? Well, a simplistic way to do it would be to directly factor in the theoretical change in torque to the ground due to tire diameter. Here's a very simplistic example using nice round numbers to make the math easy:

• 80 to 120 km/h time before = 10 seconds
  80 to 120 km/h time after = 11 seconds
  
  Upgrade size = 215/40-17 = 1.004 times (or 0.4% more) torque to the ground
  
  11 / 10 = 1.1
  
  1.1 * 1.004 = 1.1044
  
  Difference NOT attributable to torque change = 10.44%

So, in this case, despite me theoretically putting more torque to the ground due to the smaller diameter, the increased weight (and/or rolling resistance, wind resistance, etc.) cost me enough to offset that and make me slower overall.

So what is the overall message here? It is difficult to predict how much of a difference in performance a wheel/tire package will make on paper beforehand, but one can logically assume that if you are using one of the correct plus-sizes listed above as an upgrade, and the overall package is heavier, it WILL negatively affect performance. Whether you PERCEIVE the difference or not depends on how sensitive your own "butt dyno" is!

Hope this helps...

[Dave-UK-MX3-V6-SE]

Wow, thanks tatsu, nice and informative post.

I've put the 17's up for sale, and am now investigating a lightweight 16" rim for use with low profile tyres - I'm not bothered about top end speed, just acceleration really, so am I right in thinking that the reduction in weight, reduction in rolling radius, and reduction in width (ground friction) should result in generally better acceleration?

Even compared to stock? (as the rolling radius will be less)

Thanks again,
David