Hey everybody, I just got some new all-season tires on my 16" X-lites that weigh 17.6lbs and am looking forward to hi-performance tires when I get a new set of lighter 16's. I am just wondering if I should expect a noticeable difference not in the better traction of the hi-performance tires but of the lower unsprung weight. The reason I ask is, suppose I get very light 16's @ 14lbs, the wheelweight savings is 3-4 pounds on each corner. How significant of a change will these mere few pounds make for the road handling and response of the suspension? Many people seem to go from the 17" S-lites (or other 17&quot which weigh 25lbs to lightweight wheels which will save them over 10 pounds in many cases and so I understand they will see a large improvement, but what about for this situation? Thanks! :smile:

 

You can never be too thin or rich. Wheels are the same, although Grassroots Motorsports did a comparison between heavy and light wheels and the differences are hardly earthshattering. The lighter tires will have more of an effect than light wheels, but it is still hundreths not tenths of second improvements.

 

Well, I didn't know so few people had anything to say about the feel of lighter weight wheels coming from 16's... come on guys.. what's the holdup? Fwd-mx5, thank you for your reply, I don't track the car, so times won't be of concern, but that puts things into perspective. I didn't know the difference would be so minimal though, I still care to know what the different feel (if any) would be like.

 

Lighter wheels/tires aid significantly in throttle response and braking. These benefits are most significant if you are doing some sort of performance driving; lapping days, autox, etc. For just driving around town I wouldn't worry about wheel weight, I would be more concerned about wheel strength. Lightweight wheels don't like potholes much...

Ewald did some testing at Pacific Raceways in Seattle with two different tire setups. Relatively heavy Azenis Tires on V spokes (R84) and the stock Continentals on the 7 hole 15in wheels (R81). He found that he gave up grip in the corners with the lighter 15in setup (much narrower tires) but he was 6 ot 7 mph faster at the end of the front straight. I'm not sure of the overall lap time differences, but I think the lap times were pretty similar... The ultimate setup would be light and wide/grippy to get the acceloration and braking benefits and the cornering benefits.

I did not do the testing, I am just relaying Ewald's results as I remember them.

 

>>Grassroots Motorsports did a comparison between heavy and light wheels and the differences are hardly earthshattering.

Do you have a link to the article? That's contrary to everything I've read about unsprung weight.

 

>>For just driving around town I wouldn't worry about wheel weight, I would be more concerned about wheel strength>>
>>


I've made the move to a lighter wheel/tire combination on my WRX. My butt dyno felt the same imrpovement to acceleration as the under-driven crank pulley I had installed (dyno proven to add 7-9 hp).

So it's not "earth shattering", but it's noticeable if you're butt-dyno is properly calibrated.

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Motoring, the difference in the straight speed is coming from the loss of grip in the corner making entry speed lower and then straight line speed slower.
eEarly_apex, I looked on Grassrootsmotorsports.com, but could not find the link. The guys there are car guys and if you give them a call they should be happy to point you in the right direction of the issue. I will check for it in my back issues tonight and post what I find.
Chris

 

Tire Rack lists SSR Comps at 11.5 lbs for 16" versions. Were I looking for dedicated track wheels, that's what I'd go for.

 

I got the fastest time of the day for a MINI at the last autocross I went to and I was running on the heavy 17" s-lites with Yoko AVS-100s. There were several MINIs there (mostly Cooper S' like mine) including a couple with lighter 16" wheels and people who have been autocrossing much longer than me, so I have some doubt about how much difference the weight of the wheels makes.

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>>Motoring, the difference in the straight speed is coming from the loss of grip in the corner making entry speed lower and then straight line speed slower.
>>eEarly_apex, I looked on Grassrootsmotorsports.com, but could not find the link. The guys there are car guys and if you give them a call they should be happy to point you in the right direction of the issue. I will check for it in my back issues tonight and post what I find.
>>Chris

You didn't read it right. He was significantly faster on the straight on the skinny light combo, than on the sticky/heavy combo. Pacific raceway is an interesting track. The entry on to the front straight is pretty fast, and entry speeds were pretty similar, so the difference in speed at the end of the straight is definitely a function of the weight of the tire/wheel combo.

Keith

 

I replaced my heavy S-Lites and runflats with a set of the seven-hole fifteen-inch wheels and 205-55 Yoko ES100 tires. Subjectively, the ride improved a lot and the car seemed to get better reflexes. It feels like the Yokos in the same width as the OEM tires stick better, but I wouldn't be able to prove it.

 

Keith, you would think the increased grip in the corners would translate to faster straights. That's what I thought and when reading your post I saw what I thought was correct.
I also located the GRM article and the times that were 'not earthshattering' were 1/4 mile times, along the lines of .03. They also tested heavy and light wheels in an autocross with a Miata (a car that is very susceptible to heavy wheels degrading performance). The test track was an asphalt lake in South Carolina (very smooth) and the differences were ~.185. A bumpy course would increase that margin. I do not think the MINI would see as much of a difference as the Miata, but every .001 helps.
Chris

 

Everyone should read the article on Vince's website, above, (posted by orbhot) on performance driving.

http://vinceandjessica.com/mini/driving_tips.html

His message is that technique and talent have a lot to do with driving performance. Our car is very capable as it comes, assuming you use proper technique.

Having said that, the biggest performance improvement you can make to the physical car, so far as autocross is concerned, is the stiffer rear anti-sway bar, imho

 

RSpeed has lots of Rota's in 16" that are lighter than your R84's... At $135 a pop, including hardware, that's a perty good deal. My Rota Slipstreams are coming in today.

I'd love to have SSR Comps, but they're too expensive for my tastes!

 

>>I'd love to have SSR Comps, but they're too expensive for my tastes!

I thought that at first, but if you do the math, the SSR's (10.9lbs) are actually about the same as the slipstreams (13.6lbs) on a $/lb improvement scale from the stock 16" MCS wheels (17.8lbs):

save ~4 lbs for $145 = $36/lb
save ~7 lbs for $275 = $39/lb

 

Yeah... sell that to my wife!