New CC tires

[Frank Parise]

I have spoken to Bobby Archer, Jeff Speers of Hoosier, and John Purner. They have all confirmed that Hoosier will no longer be making the slicks that we ran on last year. Apparently this is being done to relieve some of the challenges that Bobby had in having to bring so many different types and sizes of tires to the VRL events. Bobby says the new tire will be less expensive.

Production begins tomorrow on the new Hoosier slick that will be made for all VRL racecars including the CC, the GT-1 and GT-2. It is a 305-18 in the front and a 335-18 in the rear. Jeff tells me it is essentially the old DOT race tire from last year that has the grooves removed and the sidewalls changed to make it a true slick. John tells me this is the new tire that will also be used in the Grand Am SGS class in 2004. The SGS class used to be part of the Grand Am Cup in 2003, but it will run in the big Grand Am series in 2004.

This will present a variety of challenges for CC owners in 2004. First, the rear tires will not be as wide as the 345 we are used to. A smaller foot print in the rear should tend to reduce understeer or increase oversteer, depending on how you look at it. Second, I don't know how the compound is different from what we are used to. If the Grand Am boys are using it in their endurance races, perhaps it will last longer. I've heard the compound is no different than the old DOT Hoosier and I've also heard it is no different than the VRL slick. I didn't think that both Hoosier tires were made of the same compound last year, but I'm not sure. Third, the new rear tire is only 25.6 inches tall versus our existing rear VRL slick that is 690 MM or 27.16" tall. This changes the effective rear axle ratio approximately 5.8%. I believe this means that we now have, effectively, a 3.25 ratio rather than a 3.07, but I'm not sure. It also means we have to reprogram our Motec systems so that the wheel sensors produce the correct speed and distance in the all the calculations that are made.

I would appreciate if PVO can tell us what programming changes are necessary when we modify the height of our tires from the factory original size.

This is everything I know to date. Thought you would like to know early enough to make any set up changes to your car.

 

[FrankBarba]

With this new tire being less expensive, is it going to be considered a DOT Tire? Since it is essentially made of the ame materials.....Any help would be appreciated...Some events i would rather run ITE instead of SPO.....

 

[DonMc]

i have also ask eric p. to ask the dodge engineering team to reissue the suggested alignment setup with the new tire specs if it is different. i have heard that you need to replace the 10" rear inner rims with 9" inner rims...the list goes on and it is really late to be making these type of changes, at least for those of us who don't have any support team...btw, i haven't seen anything on this on the viperdays site, have you?? it was discussed at finals but that was the last i heard...also, i have 2 sets of good hoosiers from last season i was hoping to get some use out of....this is getting to be more expensive everyday!!

 

[Bob Woodhouse]

Frank,
As usual a great post on a subject that should have interest to a lot of Viper racers.
Two comments: It will not be necessary to re-program your Mo-Tec. This means all comp coupes, other SRT's, I don't know; perhaps Eric could respond for those. The reason all is OK is that your computer takes a reading of front to rear speed differences and re-calibrates on it's own within one to three miles. Now what happens if you change diameters of all four, how does it know? Duh, dunno. The previous scrap of knowledge was gleaned from our changing to the iddy bitty toyo rear tires we run in SCCA WC GT.

An added benefit, beyond the one Frank already pointed out, is that the smaller tire lets your suspension have more travel at the same ride height. Trust me, that is a good deal for us comp coupe blokes.

As for the tire itself, I am very looking forward to it. Most of you were aware that the DOT Hoosier was faster than the previous slicks offered, (one exception, the early built comp coupes that had the original equip tire with the DOT compounding). This new tire seems like a great compromise all around for all of us, cost reductions, less complexity and a faster tire, (potentially).

The term DOT and that tire have outlived their reason to exist anyway as it was created to get a competitive advantage where DOT (ie.street tires) were required. No longer an issue in most cases. Don points out one stickler, the SCCA IT class. Hey, maybe we just groove em Don, ask Rick Maxwell to bring his groover gun next time out.

I think most GT-1 spec Viper Days cars will need to compensate for the smaller width front tire, it is likely that since most of you have been running the big 335's on all four corners that you will now have some understeer. Oh, and guess what, we make a front bar that adjusts. www.woodhouseviper.com huh just thought of that!

 

[Frank Parise]

Thanks for the return post Bob. I was under the impression that the Motec does not self-adjust for the new rear tire diameter. Jimmy McCann told me that Peter from PVO reprogrammed the McCann cars for the Toyo tires. At the Road America event, they reprogrammed their Motecs and I did not. The result was that I was showing top speeds on the straights of over 160 MPH, and they were both in the mid 150's. If what you say is correct, that's great, but would you please check and reconfirm. Thanks much!

 

[Frank Parise]

In my above post I erroneously said that Peter from PVO made changes to the Motec to correct for non-stock tire diameters. I should have said that it was Matt from PVO, not Peter. Apparently Matt is the expert and can help clear up this discussion. Matt, please respond if you read this thread.

 

[Russ Oasis]

I spoke with Eric today on a different issue and mentioned the Motec adjustment for the tire change. He promised me that they would post the fix within a week or so (definitely before the first event). Looking forward to seeing you guys soon.

 

[Frank Parise]

The fix has been posted by Viper Headquarters in the Service Manual/Technical Updates section.

 

[VOI9 ASP]

I purchased a set of brand new Hoosiers #13865 305/645R18 and 345/690R18 from Bobby Archer a few months ago and have not had enough track time to swap them with the tires on my CC.

How long before these tires will go bad from non use?

Are you guys that race often still using these tires?

Is there a chance Archer would take them back for credit on another set when I have put enough track time on the set I have?