joey bagadonuts

I just wanted to share some info for those interested in losing some unsprung weight and maybe get others to chime in. I finally got a new set of Michelin Pilot Sport Cups mounted to my Fikse's and here are the totals compared to my street tires:

MPSC/Fikse's
F 39.5 lbs 8 x 17, 225/45/17
R 43.0 lbs 9-1/2 x 17, 255/40/17

Toyo Proxes T1-S/Cup II's
F 40.5 lbs 7 x 17, 225/45/17
R 45.5 lbs 9 x 17, 255/40/17

I'm reluctant to guesstimate separate wheel and tire weights but the key, IMHO, is how much the total package weighs. I knew I had a light street setup but was a bit surprised to see how close it came to the lightweight Fikse combo. But as you can see, the Fikse's allow me to go wider without a big weight penalty.

Anyone else?

JoeW

Not just yet, Joey. I may dredge this thread up next spring -- by then I should have Toyos (assuming they work out as well as all have said) on 8 & 9x17 and Hoosiers on 16s from Kodiak or some such. We'll see.

Thanks for starting this ----

Joe

Tom W

We had a similar thread on the 993 board a while back (here). Lots of weights for different rims and tires.

For MPSC in 205/255 on Cup II rims: 39.5 and 45.0 lbs.

tonytaylor

From previous thread;

As I have swapped my wheels around today I thought I would weigh them:

Front Cup 1 17 Wheel and Bridgestone SO2 205/45 tyre 20.78kg 45.8lbs
Rear Cup 1 17 Wheel and Bridgestone SO2 245/40 tyre 21.92kg 48.3lbs

Front RUF Wheel 8J 17 and MPSC 225/45 tyre 19.66kg 43.3lbs
Rear RUF Wheel 9J 17 and MPSC 255/40 tyre 21.58kg 47.6lbs

Johnny G Pipe

If not a stupid q:what are you using to weigh them? Bathroom scales?
If so, do the Ruf's make your Bum look less big, Tony?

joey bagadonuts

Yes, bathroom scale.

tonytaylor

Salter scales accurate to + or- 5g at 20kg last time tested Bigger if anything

AsianBond

Joey, who cares about weights...tell me more about the MPSC, been dying to get them, was debating between them and Yoko A048's. How are the MPSC so far?

joey bagadonuts

Glad you love the thread.

The MPSC's are an excellent R compound tire: great grip, predictable breakaway, comfortable on the street and fairly quiet. They cost twice as much as Kumho's but:

- They don't get greasy near the end of a 20 minute session
- Last about twice as long
- Do not require more than -2.5 degrees of camber to optimize

The downside is that they are not very safe in the rain--hydroplaning with every puddle--and tend to pick up track marbles. And like the Kumho's, they feel A LOT heavier during low-speed driving when compared to a street tire.

For high-speed events, though, they are an excellent choice but if you plan to drive on them to and from the track, make sure rain isn't in the forecast.

tonytaylor

Weighed my rear RUF wheel without tyre 24lbs8oz or 11.12kg

so if wheel and tyre weigh 21.58kg 47.6lbs then the 255/40/17MPSC (and air) weighs 10.46kg or 23.1lbs.

New rear wheel is 5.75lb or 2.6kg lighter
(and there is 2 of them and hopefully similar at the front)

tonytaylor

Dunlop D01J Formula R tyres;

235/40/18 23.2lbs/10.5kg
265/35/18 25lbs/11.23kg

graham_mitchell

There is more to this than the overall weight

You need to know the distribution of the weight. A 10kg wheel with a 5kg tire will be easier to spin than a 7.5kg wheel with a 7.5kg tire, even though the overall weight is the same. The further the weight is from the axis of rotation, the worse the performance.

tonytaylor

Quite true.

It's not unreasonable to assume the weight distribution in different tyres is broadly similar, in that the majority of the weight will be at the circumference, the "tread". Since we ought to be comparing tyre of similar overall circumference then the weight of the tyre is a good indicator of the amount of inertia it will have.
Similarly with wheel design, although higher diameter wheels, eg 18ins cf 17ins, are likely to have a greater inertia for similar weight due to the posistion of the weight of the rim. Hence a lightweight 18ins wheel may have a greater inertia than a slightly heavier 17ins wheel but I'm not clever enough to work out the ratio.

joey bagadonuts

Thanks for sharing, Tony.

Graham, I agree that mass location affects braking and acceleration as you described above. For example, you'll get better performance in these areas from a 17" setup versus an 18" combination weighing the same amount. While the weight of the separate components will remain relatively unchanged (yes, I checked), you've increased the weight concentration towards the outer edge of the wheel.

I believe the real advantage of a lighter setup comes in the form of better handling. Perhaps someone more knowledgeable can chime in but simply put, the lower the mass the easier it is for your suspension to respond to road imperfections. There's less inertia to overcome.