64 replies to this topic

[FTodaro]

I don't need any of that stuff, I am going to run the "easy Button" this year from Staples, and i did some wind tunnel testing and this was the result. 

[granracing]

Simon McBeath has nice articles on racecar Aero. Here's one he wrote about Airdams. It'll be a PDF you can download. He has another one which talks about Means testing / how to do aero testing at the track.

 

Jim, what do you do for a splitter on your STL car? Sorry, know it's off topic for SM.

[Jim Drago]

We had one made by my fabricator, it is aluminum and made in conjunction with an undertray. 

[RussMcB]

Time to start a new thread?

[Bench Racer]

  Maybe there "is" a reason we run lip spoilers?

There have been equally fast cars with no front spoiler when you had spoilers.

 

My lap times are not consistant enough and I have no segment data facts to validate with and without spoiler to determin down force through turns or down a straight away. Anyone have any segment data facts to validate with or without????

[Jim Drago]

There have been equally fast cars with no front spoiler when you had spoilers.

Not since we started sealing engines three years ago, not even close.

[Ron Alan]

Ok...more SM7 data please! All this chin talk has got me looking in the mirror at both...

[Jim Drago]

Ok...more SM7 data please! All this chin talk has got me looking in the mirror at both...

BTW .. I have no friggin idea which is faster , was just screwing around

[Bench Racer]

BTW .. I have no friggin idea which is faster , was just screwing around

Your good at that.

[Joe (dad) Jordan]

Just an update we just completed the 2nd Majors weekend in the Western Division and everyone will need to run the SM7 from now on in the West.  This was our first weekend using the SM7 and we ran the same pressures as the SM6 but I am most happy to report we set the races fastest lap on lap 18 of the second race on these tires.  This was the 3rd heat cycle and the fastest lap and what we believe to be a new track record came on lap 18 or a 22 lap race the tires had a total of 31 laps before we set the new track record.   Our fastest

 

We did rotate the tires around a bit, and changed one tire pressure 1 psi from the sm6 but that's it.  We did break in the tires on Friday test Day and did not use them again until qualifying,  

 

I do believe we have a very consistent and good tire that you will not have to "sticker up" to win.  This is a big relief to our team, as we can not afford to "sticker up"

[Cy Peake]

So how many sessions/heat cycles before the SM7 falls off roughly a second per lap?  Looks like I may stick with the ToyoRR this season, as I was getting about 15 sessions (two full double-dip race weekends) per set before they began to get slippy.  They didn't stay fast for 15 heat cycles but didn't noticeably fall off until about that many.  Comments on the SM7 for someone who is hoping to make 4-5 regional race weekends with a 2-set tire budget?

 

Additionally, does anyone know if the recommended RR mounting/rotation procedure is now null and void?

[Joe (dad) Jordan]

 

 

Additionally, does anyone know if the recommended RR mounting/rotation procedure is now null and void?

 

Too my knowledge the RR mounting rotation is still what you need to do.  We have tried to ignore it but consistently got the tread splice to show it's ugly head.

 

We will put some more heat cycles in the SM7's in a few weeks, but i don't think anyone has run them that long yet.

[Jim Drago]

Hallet was my second weekend on the SM7.  

 

My opinions differ from many, hopefully with more time and different track surfaces my results with start to mirror others. 

 

As far as speed goes..  I don't see much difference at all.  

 

As far as driveability goes...

 

Driving the tires 9.5/10 I see little to no difference.  driving at 10/10ths.. I find the SM7 much harder to drive, but it seems to be able to be driven and maybe even overdriven with no noticeable wear or drop off in performance. ( That may change as I get more time on the tire) The SM6 you could over drive and it would get pretty greasy.  The overall grip with the 7 IMO is less than the 6, not more. You can and almost have to drive and slide the 7's a little bit to get the last bit of performance out of the tire.  This will separate the fields a little bit, the top guys will be able to dance the tire on the ragged edge, the further down the line the harder it will be for people to drive.  In my opinion, set up will be dialed out a little bit. While it will always be important, the car is never stuck like the SM6 tires were.  I think the tire would hold  and hold, you could really get the car dialed for the track for max g through corner etc. I fell that with the 7's, the tires are dancing long before the 6's would do anything, so as long as set up is pretty close.. you can drive it there with 7's,  not so much with 6's.   None of this is backed by ANY data, haven't even looked yet. Just perceptions from the seat ( not always very accurate could also have been a very low grip surface)

 

 

Still I have no real explanation, but my car feels like I added 3-4 degrees of caster whenever running the 7's. My wrists literally hurt during the race, so much so that I change the grip on the wheel in turns etc. My wrists and shoulders hurt are sore after running them. Hallet is exceptionally demanding, but I had the same issues at Atlanta, they went away Sunday with the same set up and SM6 tires.  I will be moving to a larger steering wheel before my next race. But very strange.  Anyone  have any opinions on this part in particular? Maybe I am just getting old and pussified

 

Jim

[Bench Racer]

 
 

But very strange.  Anyone  have any opinions on this part in particular?  Maybe I am just getting old and pussified
 Jim

You were racing a young talented kid.     Power steering

[mdavis]

Hallet was my second weekend on the SM7.  

 

My opinions differ from many, hopefully with more time and different track surfaces my results with start to mirror others. 

 

As far as speed goes..  I don't see much difference at all.  

 

As far as driveability goes...

 

Driving the tires 9.5/10 I see little to no difference.  driving at 10/10ths.. I find the SM7 much harder to drive, but it seems to be able to be driven and maybe even overdriven with no noticeable wear or drop off in performance. ( That may change as I get more time on the tire) The SM6 you could over drive and it would get pretty greasy.  The overall grip with the 7 IMO is less than the 6, not more. You can and almost have to drive and slide the 7's a little bit to get the last bit of performance out of the tire.  This will separate the fields a little bit, the top guys will be able to dance the tire on the ragged edge, the further down the line the harder it will be for people to drive.  In my opinion, set up will be dialed out a little bit. While it will always be important, the car is never stuck like the SM6 tires were.  I think the tire would hold  and hold, you could really get the car dialed for the track for max g through corner etc. I fell that with the 7's, the tires are dancing long before the 6's would do anything, so as long as set up is pretty close.. you can drive it there with 7's,  not so much with 6's.   None of this is backed by ANY data, haven't even looked yet. Just perceptions from the seat ( not always very accurate could also have been a very low grip surface)

 

 

Still I have no real explanation, but my car feels like I added 3-4 degrees of caster whenever running the 7's. My wrists literally hurt during the race, so much so that I change the grip on the wheel in turns etc. My wrists and shoulders hurt are sore after running them. Hallet is exceptionally demanding, but I had the same issues at Atlanta, they went away Sunday with the same set up and SM6 tires.  I will be moving to a larger steering wheel before my next race. But very strange.  Anyone  have any opinions on this part in particular? Maybe I am just getting old and pussified

 

Jim

 

 

 

 

 

 

 

If I am putting a tire on so far to win races and the tires are open, I choosing the SM6.  

Funny.. I thought the same thing about the steering input as my forearms and wrists hurt too and I also changed my grip on the wheel.  I attributed it to the racing surface as Hallett is pretty rough and there are no breaks in the action on any lap.  Maybe it was the tires.  

I also agree about being overdriven.  That's a bad habit of mine and the 7s, while dropping off somewhat, do not seem to get as greasy as the 6s.

[Keith Andrews]

I've felt something similar during a test day.  My car was also pushing more than usual L & R.  I thought my set up was out of whack.  When I got home I put it on the scales and everything was normal and pointed the right direction.  The SM7's were on the 3rd HC to start with and I put 5 more on them.  I was running pressures I used to run with the 6's.  

 

Have you tried using different tire pressures?  I did some testing at Sebring at a range of pressures starting in the mid to upper 40's (Hot) and bleeding down from there.  The steering wheel did not feel heavy during this test.  I know I haven't found what i consider a go to setup yet. 

[Jim Drago]

Have you tried using different tire pressures? I know I haven't found what i consider a go to setup yet.

This is exactly where we are now.

[Cy Peake]

How fast do the SM7s come up to temp?  Good to go when the flag drops or do they take a lap or two to get predictable?

[Keith Andrews]

I think they are like any other tire I've run.  It depends a little bit on the ambient temp and how much you work them on a pace lap.  I don't know if it takes time to come up to temp or pressure or both.  They are normal.  They seem to have good laps in them a little bit longer into a race.  I haven't been surprised by them early in a race.         

[Parity]

Ran my first majors this weekend at NJMP on the SM7's and struggled quite a bit. Tires rotated on rims at every session as much as 180º which totally threw out the balancing. Also started to see the edge grain during the second session. After three sessions, I flipped tires on the rims and tried to increase cold PSI a bit as a this was the Hoosier guy's recommendation. Turned out to be the wrong move as I slid everywhere and had an off and ended with 3 of the 4 tires over 44 PSI. They were a bit out of round with the worse one looking almost flat spotted. My sense of fiscal responsibility kicked in and I refused to purchase new stickers for the race.

 

Rebalanced and dropped pressures significantly for Sunday's 10 minute warm up and had one tire move slightly on rim. Dropped pressure a little more and was able to get through the race. After the race they were rotated up to 90º.

 

I did post a personal best on Saturday but it's a new car to me and chasing faster drivers helps. Not sure I'd say they're faster but they didn't fall off as quickly. I'll need to run these 1-2 PSI lower than SM6's.