Alternate tire/wheel for FV?

[Matt]

For those who have the actual tire dimensions.
With the 14" wheel tire combination, will it mean that a long box will be needed?
With a 15" wheel tire combination will the short box be the more useful choice?

Matt

[FV80]

Matt,
I THINK I saw someplace (can't find it now) that the rollout of the Falken on the Canadian rims is quite close to that of the Hoosier on our rims. That means that short/long would still depend on the track. As for 15" rims.. ideally, IF we could find the right tire, the rollout would, again, be quite similar to our current Hoosier .. at least, that's what we would be looking for.
Steve, FV80

[BLS]

Copied from Michael Clark's post on apex. The falkens are 1.3" larger diameter and are the same diameter in 14 or 15 inch. However, the 15" are 1" wider tread width and may get some of the performance loss back from the slicks. Or, be slower from the aero issue of wider tires. The 15's are also 2 lbs heavier than the 14's. the advantage of the 15 is the much larger tire selection than the 14's (not just the falkens)

wheel . . . . . . . . . . . . . . . . . . . diameter . width . . back spacing . . weight
VW Type I standard wheel . . . . . 15” . . . . . 4” . . . . 3-3/4” . . . . . . 13
Canadian FV1200 spec wheel . . . 14” . . . . . 6” . . . . 3-1/4” . . . . . . 15.275
Empi GT-5 aluminum wheel. . . . .15” . . . . . 5-1/2” . 4” . . . . . . . . . 15.005

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . section . tread
tire . . . . . . . . . . . . . . . . . size . . . . . . . . width . . width . . height . . . rpm* . . . weight

Hoosier C3000 . . . . . . . . . 22.5x5.5-15 . . .6.5” . . . 5.5” . . . 21.9” . . . N/A . . . . 11.5 ~ 12lbs
Falken Azenis RT-615K . . . 195/60R-14 . . . 7.9” . . . 6.6” . . . 23.2” . . . 900 . . . . 19lbs
Falken Azenis RT-615K . . . 205/50R-15 . . . 8.2” . . . 7.6” . . . 23.2” . . . 895 . . . . 20.93lbs

[BLS]

the advantage of the 15 is the much larger tire selection than the 14's (not just the falkens)

Quite a few choices, including BF Goodrich DOT competition tires, one that is really a slick but designed to just meet the DOT minimums:

http://www.bfgoodrichtires.com/tire-sel ... 0/15/tires

There should probably be some restriction in the tire choice...

[Matt]

Steve and Barry

Thanks for the data. The change in tire diameter translates to an increase of 5.9% in circumference.
So there will be a top speed change.
When I ran my car at the Bonneville Salt flats, my top speed with Hoosier slicks was 98 mph at the 1 mile trap. Switching to DOT tires on the rear resulted in a top speed of 104 mph.
Pretty close to the 5.9% change.

Matt

[FV80]

Matt,
I doubt you would have seen an increase if you put the DOT tires on the front too. Additional drag & weight would override additional MPH - you just wouldn't get the same RPM.
Steve

[hardingfv32]

So there will be a top speed change.

But not upward.... It takes more power to go faster because of the increase in aero drag. Chances are very good that your new rpm operating range will be creating less HP.

Aero drag: The wheels/tires create about 65% of the aero drag with a FV. This is not frontal area. A change to DOT radials could increase aero drag of the wheels by as much as 50%. You might equate it to a 3-4 reduction in hp. Think you will notice that on the straight?

Brian

[hardingfv32]

If there were an absolutely clear alternative slick tire that would at least double, and better triple, the current life without any dropoff, I could be persuaded the alternate is unnecessary. I don't think that tire exists. I don't think that tire can be made unless it is so close to a DOT tire compound that it makes no financial sense for the manufacturer.

Posted this before on Apex Speed. I asked a specific question to Hoosier about what has changed...how do you get more durability with almost equal performance? They said it was new chemistry.

The simplest solution would be a more durable compound for the existing FV tire construction. The compound used on the SM Spec tire has been suggested. It is call SM7. I believe it is also used on the FF 1600 radial tire. The SM guys are very happy with the SM7's compound. See the comment below form a Runoffs champion. Over the last decade the OEM tire market has made improvements in compounding in the quest for better fuel economy. Hoosier has been able to use some of this new chemistry to make improvements in durability at minimal cost to performance. That is what this new SM7 compound is all about.


Jim Drago - SM Runoff Champion
Note that he is talking about races not events etc. and that the old SM6 used an old generation of compounding.

"The class loves the tire. Stickers are no longer the fastest or best cycle.* It eliminated what we were doing as far as stickering for qualifying and race with sm6 tire.* I think you can easily get 12 good cycles from them . *"personally" I can run a doubles majors on one set of stickers and then use them on the test day at the next.* I like to race on tires with 5 sessions or less, ideal being 2-4, but have raced and done well with 8 session tires as well. It depends a little on the track.*
In short, going from sm6 to sm7 has basically cut all of our tire budgets from 30-50%.* You will love the tire. It is also faster for us than the old tire."

[BLS]

Brian,

Yes, I saw your post on apex and find it interesting. Of course, hoosier can offer that tire at anytime if it is not a radial. No rules change required.

The only rule change required to allow suitable DOT tires is an alternate wheel specification to be paired with any DOT tire. As I showed in my last post, any DOT tire might be an issue however given the availability of what appears to be a slick at the very minimum of DOT requirements.

Barry

[fvracer27]

Brian I think the problem is your suggestion makes to much sense. No need to change wheels, they all ready said the could make run of them for testing, cuts tire cost and we would still get a proper "racing" tire.

One of the greatest things about FV is the feel and handling of these cars and it would be a shame to take that away. For what they are and what they cost is a pretty good bang for you buck.

[hardingfv32]

Yes, I saw your post on apex and find it interesting. Of course, hoosier can offer that tire at anytime if it is not a radial. No rules change required.

The only rule change required to allow suitable DOT tires is an alternate wheel specification to be paired with any DOT tire.

1) Just provide a harder compound was my first approach with Hoosier. Hoosier will not provide a harder compound as long as FV is a open tire class. No need for then to expose themselves to the possibility of someone else providing a softer option.

2) What is the requirement for an optional wheel/tire choice in the GCR? Has any group been denied the option in a Region's Supps? Is this a difficult think to accomplish administratively?

Does the current use of Falken tires extend beyond the NE SCCA Division?

Brian

[BLS]

Brian,

1. Yes, that makes sense. Hoosier is not going to make a hard compound tire and get beat out by someone making a soft tire. It would have to be a spec tire.

2. The GCR is pretty straight forward - the wheels are the standard 15x4 as used on the VW sedan, or any 15x4.5 that are within the track dimensions. I don't know what has bee tried on a regional basis, other than NE group

As far as I know, only the Challenge Cup group in the NE is using the falkens along with the steel 14x6 wheel the Canadians use.

So, as an alternate, a harder Hoosier that lasts at least twice as long would be an improvement. No way to know how it really stacks up on a V without testing. But it does seem like a reasonable alternative.

[willwin2day]

Steve:

Has anyone approached Bruce at Hoosier? I'm opposed to running a street tire especially when it is left open to any brand. Some guy has a couple of wins and then everone abandons their tire for the winning brand. We have heard on numerous occasions about attracting the new driver to our class. I am not sure a street tire will do that. Let's see if Hoosier will build us a slick with a longer life.

Donnie I.

[hardingfv32]

From another thread:

Hoosier Tires would be happy to supply a Spec tire for FV. They request that the the tire be specified or developed through the SCCA Spec tire procedure just used by FF.

The simplest solution would be a more durable compound for the existing FV tire construction. The compound used on the SM Spec tire has been suggested. It is call SM7. I believe it is also used on the FF 1600 radial tire. The SM guys are very happy with the SM7's compound. See the comment below form a Runoffs champion. Over the last decade the OEM tire market has made improvements in compounding in the quest for better fuel economy. Hoosier has been able to use some of this new chemistry to make improvements in durability at minimal cost to performance. That is what this new SM7 compound is all about.

The SM7 compound on the current Hoosier FV bias slick construction should increase durability 2-3X with a minimal or small decrease in performance. To be clear there is still a loss in performance when you increase durability. This compromise is just more limited with the new compounding. Tires can be made available for evaluation in the context of the Spec tire evaluation process.