VetteDrmr

I've been running a set of repo GS wheels (17x9.5, 17x11) and either Kumho V700 or Toyo RA-1 tires for my local autocross fix.

Now, I'm transitioning to a set of original OE 18x10.5 Z06 wheels (Speedlines?). I mounted a set of 305 Hoosiers and weighed them against my 315 V700s on the 17x11s. All tires seem to have about the same amount of rubber.

17x11 repos w/315 V700s: 53.25 lb.
18x10.5 Z06 wheels w/305 A3S04s: 44.75 lb.

I've also mounted a set of 17/275 Hoosiers, but I'm still having to use the GS repos (got to get through these before I can go to 18s all around).

This next question is tough, because I've not experienced the increased grip of Hoosiers. What will I feel different pulling 8.5 lbs. from the rear corners and some lesser amount from the fronts?

Or, is this question so confused and scatterbrained that it needs to be deleted?

TIA, and have a good one,
Mike

TedDBere

The rule of thumb that I've been taught is every 1.0 lb of rotating mass is the equivalent of 4 lbs of static weight.

So a 17 lb reduction in wheel/tire weight would be the equivalent of a 68 lb reduction in static weight. Therefore you should be able to feel the performance increase the same amount you'd feel it increase with a 68lb weight reduction. Now if you can feel that difference then you are a better driver than me...lol. It will be there, just hard for most drivers to feel.

LehmanZ06

The car would possibly feel a little livelier on the lighter wheels.

BUT----going to the Hoosier A6 is an incredible difference----MAX your camber----and after 35 to 40 runs---FLIP your TIRES !

Welcome to real world of R compound CRACK !

LehmanZ06

Oh yeah Ted----

The 4lbs rule is BS----more like 2lbs-----

VetteDrmr

Thanks, guys.

That's about what I thought, maybe a better feel, a bit more "spirited", but nothing really specific.

But, the tires I've got right now are a mix of S04s and S05s, with some A and some R compounds. But hey, it can't be any more different than when I was running Ra-1s up front and street tires on back! Just a wee bit of oversteer!

Thanks again, and have a good one,
Mike

RC45

You should notice it easily.

I ran a set of repros on the street for a week, and then went back to my OEM Z06 wheels because the car felt like pickup truck with large lead cubes for wheels - especially up front.

I felt an immediate lethargy in acceleration, braking and turning when I put the repros on.

Going the other way with sticker tyres should be just as noticable.

Aardwolf

My car felt a little faster when I switched to lighter rims. I remember seeing a dyno chart of someone that changed wheels, there was a 10 HP difference.

RX7 KLR

Going strictly on weight... You will notice your wallet is lighter. Unless you are within a tenth of a second to the top guys, you are spending money on the wrong part.
The only significant gain you are going to see is from the tire change.

VetteDrmr

That's the main reason I bought them: it's getting so that 18" scrubs are easier to find than 17", and I got a deal on the wheels/tires I couldn't pass up.

Have a good one,
Mike

XPC5R

8.5 lbs will be very noticeable, especially accelerating in 2nd gear There may also be some small gain in direction changing quickness, with less gyroscopic forces from all 4 corners.

When we switched from 16" slicks to 18" DOT's, and added about 7-9lbs a corner, the car lost a lot of jump coming off the corners. I'm actually running smaller sizes this year to regain some acceleration and nimbleness.

VetteDrmr

XPC5R,

Any chance you'll be out at MW running with the BMW group on Sep. 7th?

Awesome watching that beast of yours on course out there!

Thanks for the comment, and have a good one,
Mike