Earlydays

Another factor to consider is the tire weight difference between brands.
I run Yoko AD08's in 16" sizes for autocrossing in SCCA's Street Tire - C Stock class.
I narrowed my choice to the Yoko's and Bridgestone RE11's. I chose the AD08's because they were 2 lbs. lighter per tire in the front and 4 lbs lighter per tire in the rear. In fact in my sizes the Yoko's were also lighter than Dunlop Star Specs and Hankook RS3's.

ThomasC2

At the moment i use cup1 replicas from millemiglia for track, 17" with MSPC tires. The rims are a notch heavier than my OEM cup rims. But the weight of the tires are important to. The replica set up with MSPC are lighter than my OEM rims with Toyo 888's. Japaneese tires seems to be heavier than at least michelin. It was the same with an earlier set of bridgestone tires.

The price of 18" MPSC has come down to more or less 17" level now so for next season i'm now considering a set of BBS E28 rims in 18" if we can agree of the price tag. That would give me low weight and low flex due to lower profile. We'll see.

Thomas

boxsey911

Thomas, you may find the 18 inch MPSCs easier to get hold of too. Over here (UK) it's almost impossible to by new MPSCs in 17 inch sizes.

race911

See, that's the thing at our level--we're too inconsistent. If I've got time tomorrow I'll slap on the 18s and just do some ~50-110 runs up the front straight (will keep the grip levels out of the equation, Hoosiers v. dead RA1s).

KaiB

Don't misunderstand me here ya'll. I said I have no proof.

My comment, I had hoped, would only open doors to consideration that that much in weight savings (ca. 6#/corner) could certainly be worth discussing as measureable.

I say it is - once again without proof.

ThomasC2

True, and that's also a reason for moving up to 18".

Thomas

cobalt

I understood you, as I think others did. Although your comment made sense that is why I used it. Considering a total savings of 30 pounds off the car which is significant in itself and if you start to get into the physics of it which is where I fall short i am sure the energy required to rotate and stop the rotation of a 9 pound lighter wheel is less so theoretically you should be able to accelerate and stop the car quicker. Possibly even get longer life from those expense pagid pads too.

I know I have a chevy avalanche that came with 2 sets of wheels the stock rims and tires which are 20" and weigh 61 pounds a corner and some larger 22" wheels and wider tires that weigh 76 pounds a corner. You can really feel the difference in acceleration and it is incredibly noticeable under hard braking that the car does not stop as quickly with the heavier wheels. It handles and rides better with the larger wheels and tires but the scary braking and significant reduction in gas mileage makes such a difference I stick with the stock wheels now. I am sure this would apply to track wheels and tires as well.

Ken we anxiously await your results and enjoy the day even if your on old RA-1's.

race911

Quick post mortem. Got 127 terminal speed today on one of two fliers, which is flirting with all-time best (2:02.7 lap, third of the day). Day was cut short for driving as I had the left front caliper bolts back out from the threads pulling from the hub. Grr...... Hopefully able to fix, as it's an RSR hub. But I can compare from last month with the 18s, and I'll make it a time-to-distance comparison as opposed to merely top speed.

race911

To finish off beating this dead horse, here's what I've come up with. All measurements are basically running up the front straight at Thunderhill. With the above-mentioned brake caliper mounting issue I wasn't able to put the RA1s on 18s on, so I had to go back and look at other data. But it's consistent.

So here goes (all measurements are over approximately 1670ft):

11/10 (~70F, no wind) with full tread RA1 235 + 275 on Fikse 8+ 10 X 18 (bypass pipes + Fabspeed mufflers)--
65.8MPH -> 115.3MPH (49.5MPH gain) in 12.329 sec

6/11 (~85F, no wind) severely worn RA1 235 + 275 on Kinesis 8 + 10 X 18 (catalytic converter + stock mufflers)--
64.5MPH -> 112.9MPH (48.4MPH gain) in 12.556 sec

7/11 (~98F, no wind) new, but 6 year old Hoosier GAC 245 + 275 on Cup 1 replica 7.5 + 9 X 17 (catalytic converter + stock mufflers)--
64.9MPH -> 115.4MPH (50.5MPH gain) in 11.132 sec

Now here's another data point. The Friday data I had to pull from further back in the lap since I was at 73.1MPH (v. ~65MPH) from running Hoosiers, albeit seemingly aged out ones. The ultimate laps being considered here were Example 1 @ 2:04.098 (bypass config, ~2 seconds quicker), Example 2 @ 2:07.609 (full config, really dead tires), Example 3 @ 2:02.756 (Hoosiers, new but 6 years old).

So draw your own conclusions. I submit that we're not good enough at our level for it to matter in the least....................... Most important thing is to have a well prepped car that is consistent, and from which you can learn.

(Obligatory videos here, of what NOT to do on track. #1 is just a bad line on a critical turn following a guy who'd held me up for at least 1/2 lap, then how long it takes for him to let me by. #2 is another guy I've come to know who is mirror-blind, and initially how far ahead he's leading the train to how clueless he is in letting people by to finally me taking an opening that, in retrospect, really wasn't there.)

ChaseN

Wow, didn't realize this thread would provide such great reading! Thanks to all you guy for the great information. Let me clarify that I am but a plebian still at the street tire skill level. One bonus to the Cup II's is they came with a near brand new set of Michelin PS2's (9/32" tread depth left) for a grand total of $350. Should be worth some trackday hoots.

Thanks for the response Cobalt. I have no problem with 18's - I run the 18" turbo twist reps on the street as I like the look & don't worry about the extra weight off the track. I was mostly looking for 17's as consumables are cheaper, as well as the wheels themselves mostly being cheaper! Re: the chrome plating, I agree with you as far as weight & the crack issue. I'm fortunate enough that I work in a shop with access to a large media blasting cabinet and plan on blasting what I can of the plating off. Anything I should know about blasting chrome plating?

On the other hand, you've lodged some pretty serious doubts in my mind about these wheels. I may just run 'em till the tires are shot and look elsewhere.

I'm very interested, only thing is that in my mind HRE = $$$. PM me a dollar figure you had in mind and we'll go from there. I might be able to scrape something together.

Thanks for the offer, I'm way out of new Fikse price range right now - getting married in 2 months . Some day I imagine I'll be giving you a call though.

Dwane

Thanks for the info Ken! These threads and posts are pricele$$!
I've been looking for a set of used (light) 17's for a while. I'll take the wheels off the list and start looking for some RS bars instead.

cobalt

Well very nice and thanks for sharing I doubt the .2 inches less rolling diameter made a difference although I am curious how much the rubber compound did. I am not sure if i will have the time to do anything at the Glenn this coming weekend but if I can i will post the differences between the cupI's and the fikse's since both are running R888's on them I think it would be a better apples to apples comparison.

Actually starting out with the PS2's is a smart move. just watch you don't heat cycle them out long before you run out of tread. I spent an entire season on PS2's while my wife learned to drive. We share a car and with back to back runs there was no time to switch tires so i endured for a season so she could learn. It teaches you a lot about the car and limits of adhesion and they do speak to you better than the R compounds. They can get quite sticky for a street tire and have decent dry traction so you will have a lot of fun. Although don't be too anxious to move on to R compounds it will be hard to go back once you make the change.

I agree with you evaluate how you are doing after a season and you will be a better driver for it in the end.