211 replies to this topic

[davew]

The prod cars you mention are not driven the same way an SM is driven. Nowhere near the bumping, banging, curb hoping, bump drafting or general argie bargie of an typical SM.

[davew]

The prod cars you mention are not driven the same way an SM is driven. Nowhere near the bumping, banging, curb hoping, bump drafting or general argie bargie of an typical SM.

[Jim Drago]

The prod cars you mention are not driven the same way an SM is driven. Nowhere near the bumping, banging, curb hoping, bump drafting or general argie bargie of an typical SM.

I agree which is why I put it in my post  My point is this "Nowhere near the bumping, banging, curb hoping, bump drafting or general argie bargie of an typical SM."  is not going to to be reduced if we start using a harder tire and this is what causes more damage than tires with more grip, otherwise it would show up in classes that use these tires with more grip.   I dont care what the grip level of the tire is, just like to have one that offers a little more usuable life.. At the rate we are going through tires.. You can buy the front subframe, two hubs and one rear upright for that extra set of stickers we are buying per weekend now and pocket a little extra change.    

[Bench Racer]

Actually, I failed the lower balljoint at the Runoffs, never had a subframe failure myself.  From the sidelines, it sure seems like various failures are on the rise. 

 

There is zero mathematical doubt that the suspension and wheel ends are seeing MULTIPLES of the loads of a stock car, and there is zero mathematical doubt that more offset, taller tires, heavier tires, and stickier tires, all increase those loads.  But running into things, cars, walls, sandtraps, has still got to be the worst loads we can experience?

 

Dave, oop's a ditto post. Argy-bargy, (noisy quarreling or wrangling) had to look that up.

 

Post #157 through post #163 present many contributors to broken diff. and broken sub frames. Maybe if the class skipped the car to car contact, specifically bump drafting, life for the entire class would be more cost effective. Crashes and 4 wheel off track agriculture experimentation occurs, but is not planed/executed during each qualifying session and each race session as is bump drafting. My use of the STL and Prod car is an example of two cars which are driven under the same conditions (stiffer springs/shocks settings and SM rims with 3/4 and 1 inch spacers) as SM except bump drafting/wheel banging and have not had broke diff. or broken sub-frame. 

[38bfast]

Bench not everyone has broken a Diff housing, subframe, wheel hubs, ball joints, bearings. Many can go without many of these failures. Then there is the unlucky few that will break everything on the list. 

 

Preventative maintenance seems to help out. But many of the failures are on the high time low budget cars. The demographic that many trend not invest in preventative maintenance. 

[davew]

The prod cars you mention are not driven the same way an SM is driven. Nowhere near the bumping, banging, curb hoping, bump drafting or general argie bargie of an typical SM.

[davew]

Diff housing do not break from typical small contact. Hard slam drafting or hard surface contact.

 

Subframes will bend in hard side contact, but the brackets are designed to stop the tearing of the metal. Which is caused by repeated bumps,and curb hoping. As seen worst at Sebring and Road America.

 

Find a spot where you can watch from the outside of a corner, where you normally drive over the larger track out rumble strips. The track out at turn 5 at Road America from the access road is a prime spot. Watch the loaded tire as it bounces over the rumbles. It is amazing how violent it is. You will then understand why the subframes get torn apart. Unfortunately they tear at track out, then under braking, all the force causes them to rip open the tear, which causes severe toe out. And the subsequent crash and big expense.

 

Dave

[Bench Racer]

I'm sorry for all the miss information guys, I just got off the turnip boat from turnip island.

 

https://www.bing.com...9456D&FORM=VIRE

[38bfast]

http://s217.photobuc...pindle.jpg.html

[Todd Lamb]

...many of the failures are on the high time low budget cars. The demographic that many trend not invest in preventative maintenance.

 

If there's one sure fire reason to have less grip, this is it. If we can reduce maintenance costs for the low budget guys while reducing the tire costs for the high budget guys, we'll have achieved a very big step forward.

[Jim Drago]

If there's one sure fire reason to have less grip, this is it. If we can reduce maintenance costs for the low budget guys while reducing the tire costs for the high budget guys, we'll have achieved a very big step forward.

That we all can agree with, well probably not

[SaulSpeedwell]

Minor highjack, but my intentions are good.  How low (numerically high) can you guys go on offset and still have Der Continentals fit on the inside? 

 

With +43 mm being the stock offset, and the SM norm being closer to double (numerically half) of that, there may be an easy and fairly cheap reduction available that should help bearing/hub/spindle/flange life?

 

Don't we have some strain gauge nerd on here that can instrument this and tell us what % the Continental SM7s are costing us versus the NITTO RA-1s?

 

Extra credit: instrument the tie-rods and tell us what amount of toe-out creates the least drag when going straight, because we know zero toe can't possibly be the least drag for decambered tires, much less our highly decambered Contis!

[EMatoy]

I took the strain gauge tie rods off my old car. If I still have them on the shelf or can find old data I will share it.

[Tom Sager]

Minor highjack, but my intentions are good.  How low (numerically high) can you guys go on offset and still have Der Continentals fit on the inside? 

 

With +43 mm being the stock offset, and the SM norm being closer to double (numerically half) of that, there may be an easy and fairly cheap reduction available that should help bearing/hub/spindle/flange life?

 

Don't we have some strain gauge nerd on here that can instrument this and tell us what % the Continental SM7s are costing us versus the NITTO RA-1s?

 

Extra credit: instrument the tie-rods and tell us what amount of toe-out creates the least drag when going straight, because we know zero toe can't possibly be the least drag for decambered tires, much less our highly decambered Contis!

 

 

 

To compensate for the scrub created by negative camber, toe out of 5-10% (in degrees) of camber per tire will negate the effect.  The range is an estimate due to tire characteristics.  Different tires behave differently in this respect.

 

This math converting to inches may be correct:

 

A right triangle with a short side of 1" and the other side of the right angle at 56" will make a 1 degree angle.   

You'll have to input the real tire diameter or length of your toe plates, but let's say 24". 
Then 56/24 = 2.33. 1"/2.33 = .42" which would equal 1 degree at 24". 
Then if we guess right in the middle of 5-10%, 3 (degrees camber) x .075 (7.5%) = .225 degrees. 
Then .225 x .42 = .0945

 

Now here's my question to the drag kings and queens out there:

 

How many of you are willing to run this amount of toe out in the rear?

[Jim Drago]

not specifically related.. 

 

But just wanted to mention.. The SM7 compound was specifically designed for Indianapolis.  When grand am went there they were graining the hell out of tires.  They ran harder tires( endurance), but still grained. the Sm7 compound along with multiple others were tested to try get rid of the graining. The way I remember the story from Bruce, this compound was faster and they never thought it would hold up. It ended up being the fastest and most durable.  

Jim

[Tom Sager]

Here's a vote for opening the locked thread on tires.  Seems as though input and debate on the tire topic is being limited a bit.  What is this facebook?

 

Appreciate Todd's update and glad that tire testing is getting done ahead of time and in time for another tire to be evaluated and produced. 

 

Kyle mentioned something about size?  We had RA-1's they were physically the smallest tire and they offered the most number of consistent heat cycles and less grip.  888's were bigger and had shorter life.  SM6 bigger still and an even shorter life.  SM7 is a longer life tire than SM6 but still really big.  We're right on the edge of some clearance problems with the SM7 but it's not too big. 

 

I don't really care what size is stamped on the sidewall or the final dimensions (within reason).  If we get something a little longer lasting and consistent, similarly priced and a continuation of the excellent support SCCA has had from Hoosier (which is better than the support SCCA got from Toyo), we'll have a winner. 

 

Hopefully there is enough testing done soon to ensure this. We've had a couple surprises along the way.  One with the 888 that was a hard tire to manage and another with the SM6 which offered a very short competitive life. A big yes to more testing soon.   

[Todd Lamb]

Tom - discussion is not being limited, however, arguments and accusations are. The SMAC thread will remain closed, but feel free to have civilized discussion in this or another thread.

 

As always, if you have input you'll need to submit a letter.

[Steve Scheifler]

Please point to exactly what argumentative, accusatory or uncivilized post prompted locking of the original topic.

[Martinracing98]

Almost every post I have read in the last day has been two people going back and forth at each other. Can we try to something more productive? When I read the first post that listed the goals as shown below they seemed worth while and understandable.

 

Steve - You did not feel the same way. Are there other goals we should be trying to achieve? What clarification are you looking for?

 

Todd - Anything helpful to add? Any targets? For example hoping to get to X useful heat cycles? I know more is better. With SRF two additional goals was not to have a golden heat cycle. If it drops after first cycle and then level for 12 it is still a problem. Also a tire that is forgiving for average drivers. Some tires tested were great on your listed goal but gave almost no notice before a spin. They were ruled out. SCCA Enterprise did a good job selecting a new tire. You might talk to them about their process.

 

 

• Lap times are not important (everyone on same tire)
• Overall grip should be reduced to reduce wear and tear on cars/parts
• Tire longevity is important
• Getting more heat cycles is important

[Todd Lamb]

Yes we are aware of the SRF3 tire development process as well as how the current SRF3 tire performs (my coaching client won SRF3 Runoffs) - I even did some of the testing personally as different options were being considered, and reviewed quite a bit of tire data.

 

Just for some background, the SMAC has 80+ years of collective racing experience at amateur and pro levels. I alone have 37. We are well aware of what the class needs, what the tire limitations are, and we also have tire engineers providing information. Suffice it to say we have a handle on things, have thought this out very thoroughly, and will update once the upcoming testing is complete.

 

It's great that the community has input, but we can assure you it has already been considered, addressed, brought up, or otherwise discussed at some point during this process...we aren't just throwing darts at a dart board. 

 

Notice I am saying "WE"....as chairman I am but one person on the SMAC, and while I am the messenger in this case, WE all are doing everything we can to have a better tire for SM in 2019.

 

On that note, if the collective "you" believe you have NEW information, feel free to submit a letter and we'll review on our next SMAC call. Many of us on the SMAC don't check here often.