So, I'm wanting to spend more money on my MINI. Wheels and tires seem to be the next logical move.

Still have the stock 17" Tentacles w/ Hankook run-flats installed and while the car handles fine and rides okay (thanks to the DDC), I'm reading that going to a non-run-flat will improve ride quality noticeably (and also help with road noise too).

Following this investigation, I started to grasp the concept of un-sprung weight and how eliminating 1 pound per corner has the same effect as removing a 80lb bag of concert mix from your trunk (or boot in the case of the MINI). Ratio is 1:20 based on some wheel manufacturers websites. Even if that number is inflated by 50% 1:10 is still quite substantial.

So, I have found a nice set of tires that will provide excellent ride quality and noise reduction while still providing excellent wet weather performance (My two main issues being ride and noise with the third being wet weather since I live in Florida with daily summer monsoons). The tires also get better than the normal summer tire wear ratings (340 vs. 280 and below for some others that are compared by Tire Rack).

Each tire happens to weigh 2 lbs less than my Hankooks. So I save 8 lbs of un-sprung weight overall with just a tire swap. If I add in after-market wheels that can shave another 6 lbs. per corner (24lbs overall). My un-sprung weight is lessened by a total of 32 lbs.

I'll let you guys do the math on projected weight saving (using the weight ratios), but it should be huge and quite noticeable, no?

Can anyone who has done a swap of tires and wheels (where there is a significant drop to un-sprung weight) tell me how noticeable the weight reduction is on handling, performance and gas mileage?

I'm not an auto-x or track guy, but do like some spirited driving and appreciate handling and performance gains (as well as cabin noise reduction and ride quality improvement).

Any insight from members would be extremely helpful with their experiences on tire and wheel swaps, as this swap won't be exactly cheap. I like the look of the stock wheels (so new tires will be coming either way) but if going with a new set of light weight wheels would provide significant and noticeable gains, I'd be willing to dig deeper in my pockets for those gains. Rather hoping that driving the car after the tire and wheel swap referenced above will be a "Holy $#!t" moment for the improvements perceived.

Thanks

 

You are not going to have a perception that 640lbs. have been removed from your car. You may not even notice any difference without a stop watch.

However, the tires you pick can increase the available grip dramatically.

A review of my favorite street tire is here:
https://www.northamericanmotoring.co...hing-well.html

 

Removing 1# at the tread of the tire is like removing 2# on the body (not 10# or 20#)
in regards to braking, acceleration, etc., more like 1.75 # for the tire in general
and about 1.5# for the wheel, as that is getting closer to the rotational axis.
This is based on the simple physics of rotational inertia.

You may note more an improvement in ride comfort and ability of the tire to
stay in contact with rough roads, but that isn't easily quantifiable by an equation
or ratio.

If you can afford it, you'll like lighter wheels better, but it won't be a stunning
change unless you go from heavy runflats with boat anchor wheels to much
lighter wheels and tires.

BTW, which tires are you going for?
Your description sounds like probably the Conti DW, which is a very good, light,
comfortable max-performance summer tire, and outstanding in the rain.
A little soft in the sidewall, so won't feel as crisp as the runflats you're replacing,
but not mushy-feeling like your average all season or winter tire, either.
Another to consider in 205/45/17 might be the Michelin Pilot Super Sport, which has
a little more performance, and a little less comfort.

I have the DW in 205/50/16 on my MINI during the warmer 9 months of the year,
and am quite pleased with them (they don't make the Michelin PSS in 16", or I
would have probably bought them instead).

 

Only difference for me in going to aftermarket wheels and non run flats is lesser jarring over bumps. No noise reduction at all on the highway. This is a countryman so may not compare.

 

Un-sprung weight is pretty difficult to quantify against performance using a ratio. My understanding that for handling it is huge. Otherwise F1 and other racing teams spend thousand$ to reduce unsprung weight.

My understanding that benefit of tire and wheels (aside from reducing total un-sprung weight is reducing the rational weight. Example being the amount of force need to get the wheels started and stopped. I read somewhere that it was a 4:1 ratio if calculating lbs added to a car weight.

Best analogy I saw was turning a bike upside and using the pedal to turn the wheel with and then w/ out a tire. Much easier w/o. then to extrapolate this by adding larger and heavier tires to that bike rim would make each larger size harder and harder to start and stop.

Using the above analogy, it would appear a lighter tire would have a bigger impact on acceleration than the wheel weight alone.

Thought this tread was worthwhile.

http://www.nissanclub.com/forums/200...e-modders.html

 

I'd say, go for it!

My wheels are 16x7 SSR GT1 (now discontinued). They weigh in at 15.5# and the
205/50/16 Conti DW are about 18.5#, just about the same as your planned setup,
and they're nice strong semi-forged wheels. They've held up well for 12 years.

8# less at the moving end of each strut and shock will make a difference in the ride,
and in terms of acceleration, will feel like shedding about 55# instead of the 32#
actually removed, good for over 0.1 sec off on 0-60 times.

 

I'm one of the biggest advocates of shaving unsprung mass but if occasional spirited driving is the hardest you push the car I doubt you will actually notice a difference. You will likely notice the reduced harshness and quieter tire noise by switching to a non-runflat tire though. That being said, there are some good deals to be found on lighter wheels and I love my setup (OZ Alleggerita/Pilot Supersports).

 

Going with just a tire replacement probably makes the most sense (keep my stock wheels and TPMS so out of pocket will be around $500 for a better ride and handling while still shedding 8 lbs of un-sprung weight (and more importantly lessening the rotational weight by 2 lbs on each rim) than the stock Hankook run-flats.

Wheels with TPMS add about $1200 to the equation.

The issue, as with all things, is wondering how much better it would be with the light weight wheels compared to the stock tentacles.

Soooo, still debating with myself which way to go.

 

A member on this forum with a JCW recently swapped wheels & tires and he didn't really notice much if any difference with the non runflats over his original runflats....which was surprising.

It probably depends on numerous variables, like tire pressure, wheels, tire size, make of tire, etc.

My stock Pirelli P7 runflats seem fine so far although most owners don't like them. I will likely swap to Michelin Super Sports or Bridgestone RE71's non runflats at some point.

Unfortunately it gets down to trial & error, which can be costly!

 

Yes does seem surprising. Most guys say swapping out of run flats makes a huge difference in ride quality.

Makes sense since the side walls on run flats are much more rigid than non's and most agree that sidewall softness and height have the biggest impact on ride quality.

Again, everyone is different, so what may be harsh to one person is compliant to another. Although most concur run-flats ride harsher than non-run-flats.

 

Going from a run-flat to a Conti DW or even a Michelin PSS will make a big difference in ride harshness.
Going from a run-flat to a RE-71 or Direzza II or similar will make a small difference in ride harshness.

 

I agree, everyone is different. I may be the odd man out, but I have no issues with the harshness of my run flats. On the contrary, the feel is "crisp" and "firm" but not "harsh/overly firm". This makes me wonder if I'd even like non run flats...LOL!

The sport suspension on my JCW is to my liking....I don't have the DDC, and I'm not sorry I didn't spend the extra $500 for it. Sure, there may be times on horrible pavement where the "soft" ride would be nice (with the DDC), especially for when my wife is with me, but it's tolerable as is. I believe MINI did a wonderful job with the sport suspension (which is only available now in the JCW).

If anything, I'll likely go with the JCW Pro Coilover Suspension to lower the car a bit. But, for now, I'm happy with the stock SS & summer run flats.

John

 

All tires provide a good ride on smooth roads. There is but one really rough road near where I live but it made my kidneys and teeth hurt with my sport suspension (gen2) and the original ContiProContact runflats.

Some people don't like non-runflats because they lose the "go-kart handling" feel due to the softer sidewall tires causing the steering response to slow down a bit.

 

I can't say for certain because I didn't get to drive the Gen 2 JCW I was considering buying before it sold, but those who have owned both Gen 2 & 3 JCW's generally say the ride quality in the Gen 3 JCW is better with the sport suspension...and I can believe that because mine isn't bad at all (it's firm, but not jarring). Of course, any car can be rough on a terrible road......any sport suspension will not ride like a Bentley on a rough road surface!

 

Definitely true. For most drivers, a good performance non-run flat will improve ride, quiet road noise (if you choose the right tire) and still retain excellent handling characteristics. Tire Rack has some great tire comparison videos. The summer max performance tire seem to offer some great alternatives to run-flats w/o sacrificing much handling.

Unquestionably, if you race or autoX, then tires that improve handling ILO ride are certainly a consideration. I know a few guys that swap wheels and tires when Auto-x'ing for that very reason.

My Hankook run-flats tires are not too bad. With the DDC I can adjust sport to -10% getting a softer ride in all three modes. I can also boost the sport back to +10%, which can punish my back on some roads.

Wanting to soften the ride a bit more, quiet the road noise a bit more and get superior wet weather traction. Conti DW seems to fit the bill (and shave 8lbs of un-sprung and rotational weight compared to the Hankook's.

 

I think the big difference in runflat/non-runflat ride comfort is if the Mini has sports suspension. On standard suspension, the difference isn't huge.

 

+1 on the runflat to non runflat, its huge. Tighter the suspension , more you feel. DDC you should be able to dial allot of the runflat harshness out.

 

I changed from 17" S Lites to 16" Enkei RPF1s on my R53. The difference in acceleration I am not sure if I really noticed or if it was placebo from the handling. I am sure it is there, it just isn't significant enough to tell without actual data.

The difference in handling was astounding. The damn thing changes direction like nothing I have ever driven before. And braking is much better too. I actually feel like have less grip, but it is because I am carrying way more speed for the same amount of effort through the steering wheel.

James

 

What tires did you have on the 17's and 16's?

 

Yeah, when the tire diameter is changing slightly, there is going to be a slight change in acceleration, one way or the other.

If anyone does the maths (sorry, math), it does not support the idea that rotating weight has more effect than 'static' weight - it's just an internet myth, my guess by someone who didn't understand the difference between unsprung weight (important, at least for grip) and rotating weight. Or possibly by someone who felt any positive change in anything had to increase acceleration, otherwise why would anyone do it?

 

For your consideration:

http://www.w8ji.com/rotating_mass_acceleration.htm

Specifically:

Wheel Changes[
Let's assume, just as an example, all of a wheel's weight is at the outer edge and remains at the outer edge. If we reduce a wheel's diameter but keep the overall weight the same, the wheel is a spinning ring with smaller diameter. The smaller diameter increases the wheel's RPM at the same vehicle speed. The smaller diameter also moves the spinning weight closer to the center.

Let's say we cut diameter in half. Now think about how fast the wheel spins. RPM will be twice what it was at the same speed. The half size diameter reduction spins the wheel twice as fast, and that would increase stored energy to four times the original amount if the weight was the same distance out. But the weight isn't the same distance out. The spinning weight is now half size. This 1/2 size reduction decreases stored energy by four times!

If we did not change the weight or weight distribution, and we reduced a wheel and tire diameter by half but drove the same speed, nothing would change. It would be a major change that just broke even. Moving the weight closer to the rotation center reduced stored energy, but the increased RPM to maintain the same speed increased stored energy the same amount. One cancelled the other, and stored energy did not change!

If we change tire and wheel diameter without changing weight distribution and weight in the tire and wheel, we don't change a thing. In this example, we gained nothing from a significant physical change. We also lost nothing.
Lightening the tire or wheel some distance out from the hub reduces stored energy. This is especially true if the weight reduction is far out from the center. If we change the weight one-pound fourteen inches out, it is like changing weight four-pounds seven inches out. Which brings up an important point we almost never hear mentioned, a lower weight part might not be lighter at the outside edge. It might be lighter in the center, where the weight reduction doesn't mean much.

It is more important to make something as light as possible on the OUTER edge, rather than near the (wheel) center. Spending money on smaller or lighter rotors to save rotating weight should be down the list, because the rotating weight is closer to the wheel hub. Unless the rotors are huge and we take weight out of the rotor's outer areas, things will not change much. (A light rotor and wheel is good for reducing un-sprung weight, and that helps keep our tires in contact with the road. It also reduces vehicle weight. But this is a different problem. Here we are talking about rotation, not the bounce inertia or "dead weight".)

If we spent money on the same weight reduction in the wheel, reducing weight out a little further away from the center, we would do much better. We would be removing weight further out from the center, where it does the most good.

If we spent our money on a lighter tire we would be getting the very most return for the weight change. The tire's weight change is mostly outside between the rim edge and the tread area. We get maximum effect from the weight change

Think about this carefully. If we buy a lighter tire, we know for sure the weight comes off the most critical area. If we buy a lighter rotor, it is close to the center and, for the same weight change, the return is much less
The wheels also speed up and slow down gradually. With an 11-second car, we have 11-seconds to speed the wheel up. Most of the horsepower pushed into the wheel and stored is pushed in near the end, when acceleration is least. Since we have more time to push the bigger amount of energy into the wheel, it takes less horsepower than we might expect.

 

Just on note. I have owned an '08, a '12, and now a '15 ( all s's). My '08 had the sports suspension with '17 inch wheels. It would skip over expansion joints and was very jarring. Changing over to non run flats improved the ride and handling of that car tremendously.
My '12 had a stock suspension with '16 inch run flats. The car did not skip over road irregularities like the '08. At 30,000 miles I replaced the run flats with a Michelen tire (same size ). The ride was only slightly improved.
Now onto my '15S with stock suspension, the ride with '17inch wheels is dramatically better than the other two cars with non run flats.
I am not saying that there won't be an improvment with a change to non run flats, but I just don't see the change as any significant improvement in day to day driving and may even cause the steering to feel a little numb.

 

17" Federal 595SS 205/45/17
16" Conti PremiumContact (IIRC) 205/50/16

According to a bunch of internet calculators works out to be a smaller circumference by 0.79%, so pretty much meaningless.

James

 

I was wondering about your description of astounding change in handling as a function of tire construction and tread compound rather than tire diameter or wheel/tire weight.

 

The Federal 595ss are an Ultra High Performance tyre with a UTQG of 240A A. The Contis are a premium high performance with 280AA A. Pretty close but better specs on the old tyres.

I am sure having fresher tyres on made a difference, and I am sure that construction and compound also have an effect, but the amount of effort at the steering wheel has decreased and the car responds to inputs and changes direction much more quickly. That is what I would define as handling, separate from absolute grip. You can have a beautifully handling car with so so grip, and a boat with fantastic grip. That is what I am trying to explain anyway. I think there is less overall grip from the new tyres, but the car responds much quicker with the lighter wheels and tyres.

James