211 replies to this topic

[Martinracing98]

Which Hoosier do you run in SRF?

Elsewhere Jim indicates that they are the spec miata tires. They may be similar, I do not know, but they are different. I think spec miata is a D.O.T. tire like our Goodyears were. The Hoosiers we run are not D.O.T. Also they are 13". They are made for SRF. I am not sure what other tires they are closest to. I think it is a good example of getting it right. Testing was done with good and average drivers. Effort was to make sure the tires did not have a golden lap, had longevity, and was fairly forgiving. Most of my experience is in karts, but have been doing SRF for about 5 years. This round of tires are better than the previous.

[Bench Racer]

Not sure what GL is 

At the risk of over posting, GL is Great Lakes Division. Originally was area 4 of the CenDiv and WI, IL, MN, part of Dokota's  were area 5 of CenDiv. Area 4 got greedy with respect to dates and went their own way and became the GL Division.

[Erik Hardy]

I think overall, this poll or desire to make tire costs more economical is fantastic. However, I fully believe the thought process of considering a 195 tire for SM, is 100% in the wrong direction and would make tire budgets increase. I discussed this with our tire simulation engineer earlier today from work too, so hear me out for a second...

 

A skinnier tire doesn't necessarily mean a loss in grip, in fact I would expect a stretched 195 to be slightly quicker than a 205 (on the same 7" rim) due to the sidewall stiffness change.... until the tire overheats! 

 

As it sits today with our 205's,  tire management plays a key role near the end of any race. We hear this time after time with the post race interviews. With a 195, of the same sm7 compound, tire management would play a bigger role than it does today. 

 

Therefore, I would actually suggest moving towards a larger 225 tire on the same rim.

 

But wait, what about all of our cracked subframes!

 

Harden up the compound ever so slightly to reduce the overall grip of the tire. Hopefully, with the harder compound and increased thermal mass of the system, this combination would yield more usable heat cycles from the tire. 

 

But none of that can be proven on the internet from behind a keyboard. Lost of testing,$$$, and confusion. In the end a larger, harder tire might work, but then again it might be faster when shaved. So maybe this issue we have today, isn't all that bad.

 

I will however, smash my keyboard if a smaller tire remotely seems like a good idea

 

 

Like Jim said the perfect tire is not as easy as some would think. SM tried and failed with the 888. FE is failing with the AR tire. The SM6 would grain real bad at some track. The RR requires saving at some tracks. The RA1 was only fast when it was worn out.
The amount of testing to insure a tire is a success would be costly and very time consuming. If it was easy everyone would be doing it.

[BorisB]

Would that heavier, wider tire work the same on all generations of our cars ? 

[J. Pressman]

Trying to compare numerical tire sizes among brands, especially these Hoosiers is just silly IMO.  The current SM7, is enormous!  You are already running a 225 tire compared to most other brands offering in a "super 200" or "R" compound.  Miatas running SM7's and R7's in classes other than SM are running them on a 9" rim!

 

I agree going to a smaller casing, more inline with other 205 sized casings, would likely improve handling, and negate any laptime dropoff due to decreased contact patch. 

 

All things considered I think the Toyo RR that NASA is running is a better spec tire.

[CarbonRacer]

No shaving of tires should be allowed.

 

Then you will have some drivers shaving the tires down almost to the cords to make them the lightest and fastest and only get a couple sessions out of them and you really haven't solved the problem of large tire budgets. The drivers and teams will still have many sets of tires all shaved down and just keep changing tires to get the advantage.

[Todd Green]

Couple of thoughts from someone who's moved from SM to PTE and tried a bunch of tires over the years...

 

225's on 7" rims would be really pinched.  I currently run 225 R7's on 9".  It's also a very tight squeeze on NA's.  Definitely get rubbing when using curbs.  If you think 205 SM7's made the cars easy to drive 225's are silly easy.   They are also much more consistent over the length of a race.

 

Shaving - There is no way to enforce that.  I shave a tire, do circles in a parking lot and the shave marks are gone.  I'd be very much against any tire that requires shaving to be fast.  Hated the RA-1's with a passion for that reason alone.

 

Wear on parts.  I've run BFG R1's, RA-1's, RR's all in 205's and SM6,7,R7's in 205's and now 225/45 R7's and have seen zero correlation between tires and hub failures.  Obviously basic  logic says that the stickier the tire, the more force you put on the parts, but it just doesn't seem to be the limiting factor.  I'd guess poor manufacturing is the issue with hubs.  On 205 RR's I went through 3 hubs (new NTN's)  in one weekend a couple of years ago.  I've done 6 race weekends (running PTE and TTE) on 225's on the same Mazda HD hubs.  On my other car I've done a 6 hour enduro, 5 race weekends, test days etc, and will do another 6 hour enduro in a few weeks on the same hubs on R7's (205's last year, 225's this year.)  I'm 3-5 seconds a lap faster than SM and it's all suspension.  We have a junk yard motor (~180K, 1.6) in the car  I can't pull SM's in their draft and my weight with driver is 2165.  Just saying don't get your hopes up that slightly less sticky tires will "fix" the hub issue.  The revised Mazda HD/Enduro hubs seem to be working for us FWIW.   (Haven't tried the newest roller hubs.)

 

As usual YMMV.

[Tom Sager]

Couple of thoughts from someone who's moved from SM to PTE and tried a bunch of tires over the years...

 

225's on 7" rims would be really pinched.  I currently run 225 R7's on 9".  It's also a very tight squeeze on NA's.  Definitely get rubbing when using curbs.  If you think 205 SM7's made the cars easy to drive 225's are silly easy.   They are also much more consistent over the length of a race.

 

Shaving - There is no way to enforce that.  I shave a tire, do circles in a parking lot and the shave marks are gone.  I'd be very much against any tire that requires shaving to be fast.  Hated the RA-1's with a passion for that reason alone.

 

Wear on parts.  I've run BFG R1's, RA-1's, RR's all in 205's and SM6,7,R7's in 205's and now 225/45 R7's and have seen zero correlation between tires and hub failures.  Obviously basic  logic says that the stickier the tire, the more force you put on the parts, but it just doesn't seem to be the limiting factor.  I'd guess poor manufacturing is the issue with hubs.  On 205 RR's I went through 3 hubs (new NTN's)  in one weekend a couple of years ago.  I've done 6 race weekends (running PTE and TTE) on 225's on the same Mazda HD hubs.  On my other car I've done a 6 hour enduro, 5 race weekends, test days etc, and will do another 6 hour enduro in a few weeks on the same hubs on R7's (205's last year, 225's this year.)  I'm 3-5 seconds a lap faster than SM and it's all suspension.  We have a junk yard motor (~180K, 1.6) in the car  I can't pull SM's in their draft and my weight with driver is 2165.  Just saying don't get your hopes up that slightly less sticky tires will "fix" the hub issue.  The revised Mazda HD/Enduro hubs seem to be working for us FWIW.   (Haven't tried the newest roller hubs.)

 

As usual YMMV.

 

Some good points in there.  Your weight, 2165 is substantially less than what NA 1.8 and NB Spec Miata's compete at and that likely helps to reduce load although you're also likely cornering at higher force. 

 

I've definitely experienced shorter hub life since going to the SM7 tires compared to the toyos of the past.  For me lengthening the tire life (number of cycles that provide competitive performance) is the primary objective in the next tire choice for this class and if that also results in reduced wear on load components - all the better.

 

My guess is that for SCCA, Hoosier probably already knows how to achieve this if requested.

 

Also, does anyone know where within SCCA tire choice is determined?  Does the SMAC participate in the evaluation or is that done by the SCCA tech team?  Is the decision run up the same chain as other rule changes?  SMAC -> CRB -> BOD?

[SaulSpeedwell]

I think overall, this poll or desire to make tire costs more economical is fantastic. However, I fully believe the thought process of considering a 195 tire for SM, is 100% in the wrong direction and would make tire budgets increase. I discussed this with our tire simulation engineer earlier today from work too, so hear me out for a second...

 

A skinnier tire doesn't necessarily mean a loss in grip, in fact I would expect a stretched 195 to be slightly quicker than a 205 (on the same 7" rim) due to the sidewall stiffness change.... until the tire overheats! 

 

As it sits today with our 205's,  tire management plays a key role near the end of any race. We hear this time after time with the post race interviews. With a 195, of the same sm7 compound, tire management would play a bigger role than it does today. 

 

Therefore, I would actually suggest moving towards a larger 225 tire on the same rim.

 

But wait, what about all of our cracked subframes!

 

Harden up the compound ever so slightly to reduce the overall grip of the tire. Hopefully, with the harder compound and increased thermal mass of the system, this combination would yield more usable heat cycles from the tire. 

 

But none of that can be proven on the internet from behind a keyboard. Lost of testing,$$$, and confusion. In the end a larger, harder tire might work, but then again it might be faster when shaved. So maybe this issue we have today, isn't all that bad.

 

I will however, smash my keyboard if a smaller tire remotely seems like a good idea

 

This is not meant to be troll-y, but I remember when the Toyo tire engineers simply could not believe that the new R888 was definitely slower and seemingly worse in almost every way than the RA-1s.  (Then again, I doubt Toyo engineers ran bald 15+ heat cycle RA-1s on the tire machine).

 

Width and outight grip are one thing, but weight, rolling radius, offset, and sidewall stiffness are all direct multipliers on the wheel end component stresses?

 

I added up the napkin math on here somewhere, but when we go from 185/70-14 scrub radius to 225/50-15 scrub radius and +43 mm offset (stock) to where we are at now (+20-ish mm?), we are *many* times the original design assumptions, BEFORE counting the taller, grippier, heavier, stiffer sidewall Continentals?  Er ... I mean Hoosiers? 

[Jim Drago]

Elsewhere Jim indicates that they are the spec miata tires. They may be similar, I do not know, but they are different. I think spec miata is a D.O.T. tire like our Goodyears were. The Hoosiers we run are not D.O.T. Also they are 13". They are made for SRF. I am not sure what other tires they are closest to. I think it is a good example of getting it right. Testing was done with good and average drivers. Effort was to make sure the tires did not have a golden lap, had longevity, and was fairly forgiving. Most of my experience is in karts, but have been doing SRF for about 5 years. This round of tires are better than the previous.

I was called by several SRF people and talked to Hoosier people before SRF went to Hoosier. If is basically the SM tire and why they were calling me asking me lots of questions

[Johnny D]

Nice article on how to replace a SRF wheel bearing. Page 26,   PDF page 14.  Looks like they have the wheel bearing like our beefed up one we're offered.

 

http://www.sfrscca.o...July-m2-web.pdf

[Bench Racer]

Ya, well, maybe in the fact that it is a two row cartridge tapered bearing, it's like our beefed up SM front bearing, or might one say similar. Man, that's like saying a Trout is a Blue Gill. There both   Man, your not leaving me with much material to work with lately. 

[Jim Drago]

I think overall, this poll or desire to make tire costs more economical is fantastic. However, I fully believe the thought process of considering a 195 tire for SM, is 100% in the wrong direction and would make tire budgets increase. I discussed this with our tire simulation engineer earlier today from work too, so hear me out for a second...

 

A skinnier tire doesn't necessarily mean a loss in grip, in fact I would expect a stretched 195 to be slightly quicker than a 205 (on the same 7" rim) due to the sidewall stiffness change.... until the tire overheats! 

 

As it sits today with our 205's,  tire management plays a key role near the end of any race. We hear this time after time with the post race interviews. With a 195, of the same sm7 compound, tire management would play a bigger role than it does today. 

 

Therefore, I would actually suggest moving towards a larger 225 tire on the same rim.

 

But wait, what about all of our cracked subframes!

 

Harden up the compound ever so slightly to reduce the overall grip of the tire. Hopefully, with the harder compound and increased thermal mass of the system, this combination would yield more usable heat cycles from the tire. 

 

But none of that can be proven on the internet from behind a keyboard. Lost of testing,$$$, and confusion. In the end a larger, harder tire might work, but then again it might be faster when shaved. So maybe this issue we have today, isn't all that bad.

 

I will however, smash my keyboard if a smaller tire remotely seems like a good idea

 

This will go against conventional thinking.. But this is "my personal" experience!  As far as wear goes.. 

Besides Danny, I probably raced as much or more than anyone. I push the car as hard or harder than 99%, I run the heaviest version car..  So how much did I "wear" out?

 

Wear items changed this year? 

One hub

refresh on 2 season old trans

Thats it

 

 

I think we are blowing this " too much grip, we are tearing cars apart " way out of proportion! 

 

I agree we need more usable cycles and I would have no issue with a  slightly harder tires to save some money. But we arent tearing these cars apart because of tires

[EMatoy]

Jim- how old (race seasons) is you car?

[Jim Drago]

Jim- how old (race seasons) is you car?

  All of 16 and 17, 

[38bfast]

All of 16 and 17,

So if you race your new build 10 weekends a year for 2 Seasons your parts should not fatige and break. I could believe that. Exclude anything that has been involved in crash damage.

Not sure how many parts have been swapped out in that time period from getting Sternsed

[Richard Astacio]

This will go against conventional thinking.. But this is "my personal" experience!  As far as wear goes.. 

Besides Danny, I probably raced as much or more than anyone. I push the car as hard or harder than 99%, I run the heaviest version car..  So how much did I "wear" out?

 

Wear items changed this year? 

One hub

refresh on 2 season old trans

Thats it

 

 

I think we are blowing this " too much grip, we are tearing cars apart " way out of proportion! 

 

I agree we need more usable cycles and I would have no issue with a  slightly harder tires to save some money. But we arent tearing these cars apart because of tires

 

 

Just a fyi, the new car that you built for me has these weekends:

Nola - Test day only 

Cota

Palmer

Monticello - 1 day

Thompson - Track day 

Lime Rock 

Watkins Glen 

Thompson

 

I had to replace 2 front hubs (1 on each side) 1 rear hub and both upper ball joints. This all happened at Lime Rock and Watkins Glen. Perhaps certain tracks? 

[FTodaro]

I do not think we can draw to many conclusions, on one or two examples, however I think it's fair to say, in the big picture, we are havin an increase in the type and number of failures.

Go back 5 years did we talk about hub, subframe, rear knuckle, and flange failures?

Before I could support any change I would want to know, the cost for what specific changes,

I think the 3 most important factors to modify are, compound, sidewall stiffness, and size. In that order.

[Danica Davison]

Just a fyi, the new car that you built for me has these weekends:
Nola - Test day only 
Cota
Palmer
Monticello - 1 day
Thompson - Track day 
Lime Rock 
Watkins Glen 
Thompson
 
I had to replace 2 front hubs (1 on each side) 1 rear hub and both upper ball joints. This all happened at Lime Rock and Watkins Glen. Perhaps certain tracks?

 

Yes ... certain tracks is the key answer. All of the tracks that have the nice new pavement are the ones that have the issues with the hubs breaking.  I mean ... I still replace my hubs/ball joints and other items every 20-24 track hours just in case, but we don't have this issue down south. I race at Sebring A LOT, which as you know is a very rough track, and I never see broken hubs or sub-frames. 

 

I agree with Drago,  the tires aren't to blame. The grippy tires may help it wear a little faster, but the paved tracks up north are the only ones that have this issue. This makes me think it is more a track surface issue.

[Bench Racer]

So how much did I "wear" out?

 

Wear items changed this year? 

One hub

refresh on 2 season old trans

Thats it

 

I think we are blowing this " too much grip, we are tearing cars apart " way out of proportion! 

 

 

 

So if you race your new build 10 weekends a year for 2 Seasons your parts should not fatige and break. I could believe that. 

 

 

Just a fyi, the new car that you built for me has these weekends:

Nola - Test day only 

Cota

Palmer

Monticello - 1 day

Thompson - Track day 

Lime Rock 

Watkins Glen 

Thompson

 

I had to replace 2 front hubs (1 on each side) 1 rear hub and both upper ball joints. This all happened at Lime Rock and Watkins Glen. Perhaps certain tracks? 

 

 

The grippy tires may help it wear a little faster, but the paved tracks up north are the only ones that have this issue.

WTF, when one adds up the content of these 4 threads it's like asking an accountant, how much is 2 + 2? Response from accountant, anything you want it to be. 

 

Y'all get the big one.