Tire wear at the track

[rhyary]

Originally Posted by dparm

Are you using a tire pyrometer when you come off the track?

I use infrared reader. Not the one you stick a sensor into the rubber.

[rhyary]

Originally Posted by redpriest

Kumho PS91 are fine as an emergency track tire, and I've used them many times when my track tires corded unexpectedly - but ... they will wear out fast when used for this purpose. I would say you can probably get 5-6 sessions before they start to give out. They are not economical for long track runs.

18" tires are going to give you far more options and frankly, are far more economical than moving platforms are gonna be.

I have on the front PS91 275/30/19 and will be using them on the next rainy track day.

Otherwise, I am on RR slicks until I use up my stash from the winter.

Then I am going to try Hoosier A7 or R7 265/35/19. Fit would be potentially an issue so it will be a project playing with the JRZ coil overs for hight and other clearance issues

Never a dull moment

[redpriest]

Originally Posted by rhyary

I have on the front PS91 275/30/19 and will be using them on the next rainy track day.

Otherwise, I am on RR slicks until I use up my stash from the winter.

Then I am going to try Hoosier A7 or R7 265/35/19. Fit would be potentially an issue so it will be a project playing with the JRZ coil overs for hight and other clearance issues

Never a dull moment

Hmmm, I ran 265/35/18 BFG R1S and this is a super wide tire - I had to have a 5mm spacer in the front just to clear the perch, but it was otherwise fine in the rear.

[dogbone]

With JRZ, I wonder if you could fit 295/30/19 up front. The R7 comes in that size.

[rhyary]

Originally Posted by dogbone

With JRZ, I wonder if you could fit 295/30/19 up front. The R7 comes in that size.

I tried.
By mistake.
Early in my career as HPDE driver I mounted by mistake the rear 295/30/19 on the front passenger because it was the least worn tire not thinking to check the size.

Surprisingly the only unintended consequences was the inner rear inner fender. Still on the todo to be replaced 3 years later.

Anyway, my dream would be 295/30/19 square.
Not sure yet how to implement it. Also, visually it may stick out of the fender too much and be unpleasant to look at when sitting in the garage.

Next project is front 265/35/19.
Scheduled for Aug.

[rhyary]

Originally Posted by dogbone

With JRZ, I wonder if you could fit 295/30/19 up front. The R7 comes in that size.

Dog,
you just gave an idea!!!
I have a set of 295/30/19 RR rears.
So after my next track day, my front RR will be done.

So, I will mount the rears on the front wheels and test fitment. Then we know!

[rhyary]

Originally Posted by dogbone

With JRZ, I wonder if you could fit 295/30/19 up front. The R7 comes in that size.

So, no question should be left unchecked!

My rear track set is 10.5 and 23 offset and has 295/30/19 RR. No excuse not to test a theory.

So I have 3mm and I had to use them.
I will need at least 5mm for sure, but perhaps 10mm to clear the JRZ.

Otherwise it fits perfectly but.....

The problem is full lock. It hits the inner fender too hard and definitely going to polish the metal behind the fender.

But this has so much potential.

Question number 1:
Will a 5mm or 10mm spacer help with clearance at full lock rear. The front is not a problem.

Question number 2:
What will it take to have 5mm more clearance at full lock. What metal shavings can be done on the rear at full lock. What is actually behind there? the chassis? a fender? structural?

Question Number 3:
Has anyone actually able to fabricate clearance at full lock in the rear?

[dogbone]

Originally Posted by rhyary

Dog,
you just gave an idea!!!
I have a set of 295/30/19 RR rears.
So after my next track day, my front RR will be done.

So, I will mount the rears on the front wheels and test fitment. Then we know!

hehe it’s always fun trying to fit the fattest tires possible on a car! Have fun!

[roastbeef]

google "fender rolling." another technique is "massaging" with a 5lb sledge.

[dogbone]

Originally Posted by roastbeef

google "fender rolling." another technique is "massaging" with a 5lb sledge.

You can’t roll the front fenders because they are plastic. You can roll the rears.

[rhyary]

Originally Posted by dogbone

You can’t roll the front fenders because they are plastic. You can roll the rears.

The immediate challenge is not the fenders but the rear inner fender and what's behind it during full lock (more precisely the last ~10%.

The two 19" rim options with good count of tire availability are 265/35/19 and 295/30/19.

Each option has its difficulty.
With 19" x 10.5" x 23 offset offset rim:
This is my rear track wheel.

The 265 is taller and may hit the fender but clears the spring and I think clears the inner fender lock to lock. A 275/30/19 has no inner fender issues. I have not tested this size yet

The 295/30/19 is my current rear set with RR.
So easy to test what can be done.
A 295/30/19 has wide selection and mostly has the RR $260 tire available. The issue may not have a solution if the metal behind the inner fender plastic can not be bent to yield another 5mm or better yet 10mm. Also, it will need either a 5mm or 10mm spacer. We already know that 3mm spacer is not enough to clear the JRZ

Using 10mm spacer will clear the JRZ, may help with the inner fender rear but may create upper fender issue, with the JRZ, I can raise the car, but that may have detrimental effect on lap time.

Another thing to consider is that a Hoosier R7 or A7 265/35/19 is a significantly more expensive tire than the 235/35/19 RR and the 295/30/19 is even more expensive.

At the end the 235/35/19 is not perfect, but has many advantages. no fitments issues, cheap, and the fastest compares to anything non slick at any size (245,265,275).

Grrrrrr

[slicer]

A spacer will not help fender liner clearance. It will make it worse. Think about the wheel position when the wheel is turned. Adding a spacer will push it closer to the fender liner.

That being said there are a couple of options. There is metal that can be cut to increase room on the back side of wheel well. In addition the windshield washer tank is located behind the liner on passenger side. That can be removed (saves 10 lbs with fluid). Lastly you can install steering rack limiters to prevent turning the wheel far enough to cause clearance issues.

Another thing to point out is that you can improve inner clearance with your JRZ by going to a shorter spring and or helper. Do you know if you are using a no-load helper? If not there may be some available stack height reduction by switching to a no-load helper. I was able to completely delete my helper but Ohlins uses an inverted design which allows me to pre-load the spring without a helper.

[rhyary]

Originally Posted by slicer

A spacer will not help fender liner clearance. It will make it worse. Think about the wheel position when the wheel is turned. Adding a spacer will push it closer to the fender liner.

That being said there are a couple of options. There is metal that can be cut to increase room on the back side of wheel well. In addition the windshield washer tank is located behind the liner on passenger side. That can be removed (saves 10 lbs with fluid). Lastly you can install steering rack limiters to prevent turning the wheel far enough to cause clearance issues.

Another thing to point out is that you can improve inner clearance with your JRZ by going to a shorter spring and or helper. Do you know if you are using a no-load helper? If not there may be some available stack height reduction by switching to a no-load helper. I was able to completely delete my helper but Ohlins uses an inverted design which allows me to pre-load the spring without a helper.

Here is my 275/30/19 and JRZ
Perhaps it will give you some insights into coming up with a solution.

[slicer]

Originally Posted by rhyary

Here is my 275/30/19 and JRZ
Perhaps it will give you some insights into coming up with a solution.

That's a rated tender spring. Going to a no- load helper will push the perch up about 12mm because it has a 12mm shorter stack height.

You can possibly gain more by going to a shorter main spring if a shorter spring has enough travel for your suspension setup

[rhyary]

Originally Posted by slicer

That's a rated tender spring. Going to a no- load helper will push the perch up about 12mm because it has a 12mm shorter stack height.

You can possibly gain more by going to a shorter main spring if a shorter spring has enough travel for your suspension setup

I am not sure 12mm will solve the problem.
I am concerned that a shorter spring may not results in better laptime.

Also, both the 265/35 and 295/30 are taller.

A 295 perhaps would have too much hard issues to solve. Will 265/35 be easier to solve?


I hate engineering. There is always something in the way.

[slicer]

Originally Posted by rhyary

I am not sure 12mm will solve the problem.
I am concerned that a shorter spring may not results in better laptime.

Also, both the 265/35 and 295/30 are taller.

A 295 perhaps would have too much hard issues to solve. Will 265/35 be easier to solve?


I hate engineering. There is always something in the way.

265 is definitely easier to solve. There's zero reason to make any adjustment to the suspension for a 265/35/19. It will fit easily - other than the diameter causing some rubbing on the fender liner (which would not likely be solved by a more conservative offset afforded by more inner clearance). The need for increased inner space is for fitting a wide 295 which needs all the room it can get (width-wise).

A shorter spring in the same spring rate would have zero impact on your lap time. The change will not be detectable As long as the spring has enough travel (you simply want to avoid a spring that will bottom out before the suspension does). The gain would come from the added grip of a wider 295 tire (afforded by the extra space provided by the shorter spring)

I will point out that all of this is easier with 18" wheels because of available tire sizes. For example 265/35/18 and 295/30/18 are far easier to fit due to their 1" smaller diameter (when compared to 19" tires of the same width and aspect ratio). I know you are committed to your current brake kit and would not consider changing it. However this point will benefit others considering what brake kit and wheel size to build around. For those of you who don't know - @rhyary has a Brembo 380 kit which is very limiting when it comes to wheel fitment. There are only a select few 18" wheels that can clear that kit, therefore @rhyary is focused on 19" wheel and tire fitments.


Here's a picture to illustrate the reduced stack height of a no -load helper. Note how thin the helper spring coils are.

Wheel fit by slicerM, on Flickr

[ThunderMoose]

Originally Posted by slicer

265 is definitely easier to solve. There's zero reason to make any adjustment to the suspension for a 265/35/19. It will fit easily - other than the diameter causing some rubbing on the fender liner (which would not likely be solved by a more conservative offset afforded by more inner clearance). The need for increased inner space is for fitting a wide 295 which needs all the room it can get (width-wise).

A shorter spring in the same spring rate would have zero impact on your lap time. The change will not be detectable As long as the spring has enough travel (you simply want to avoid a spring that will bottom out before the suspension does). The gain would come from the added grip of a wider 295 tire (afforded by the extra space provided by the shorter spring)

I will point out that all of this is easier with 18" wheels because of available tire sizes. For example 265/35/18 and 295/30/18 are far easier to fit due to their 1" smaller diameter (when compared to 19" tires of the same width and aspect ratio). I know you are committed to your current brake kit and would not consider changing it. However this point will benefit others considering what brake kit and wheel size to build around. For those of you who don't know - @rhyary has a Brembo 380 kit which is very limiting when it comes to wheel fitment. There are only a select few 18" wheels that can clear that kit, therefore @rhyary is focused on 19" wheel and tire fitments.


Here's a picture to illustrate the reduced stack height of a no -load helper. Note how thin the helper spring coils are.

Wheel fit by slicerM, on Flickr

I think the key message here is that before you begin modifying your car, find out what others are doing and why first.

I bought my E46 M3 track car in 2012. Fastest guys had 18x9.5 rims with ET35 offset and camber plates at ~3.5 negative camber.

That's what I bought. I haven't varied from that set in 7 years. I run 245/40/18 Hoosiers which are actually wider than 265 pirelli DH slicks. Have run those tires for last 4 years.

Car came with brembo 355 4 pots in the front and stock calipers in the rears. Have run with pagid RS-29 compounds for all 7 years of ownership.

I did change from KW V3 to MCS 2WNR so that I could play with springs. Have had 700/800 springs for last 3 years.

Point is I haven't had to experiment with setup and have been able to focus on the driver.

Some people like to tinker. Some people like to just go with tried and true. I respect both.

[rhyary]

"Point is I haven't had to experiment with setup and have been able to focus on the driver.

Some people like to tinker. Some people like to just go with tried and true. I respect both."


ThunderMoose wise words.

I don't tinker with my ice cream.
I always order vanilla and focus on the eater.
Still, my wife makes fun of me.
I can't win.

Once I get to a config I like on the E92 M3 I will be set. I don't plan to tinker forever.

[dparm]

Originally Posted by rhyary

I have on the front PS91 275/30/19 and will be using them on the next rainy track day.

Otherwise, I am on RR slicks until I use up my stash from the winter.

Then I am going to try Hoosier A7 or R7 265/35/19. Fit would be potentially an issue so it will be a project playing with the JRZ coil overs for hight and other clearance issues

Never a dull moment

I thought the A7 was more of an autocross tire? I'd be hesitant to take that on the track unless you just need a tire for a quick qualifying lap or whatever. I would think it's going to overheat fast.

[rhyary]

Originally Posted by dparm

I thought the A7 was more of an autocross tire? I'd be hesitant to take that on the track unless you just need a tire for a quick qualifying lap or whatever. I would think it's going to overheat fast.

Here is the description:

Hoosier Racing Tire Sports Car DOT Radial R7 tires are Racetrack & Autocross Only tires developed for drivers who compete in road racing where responsiveness and high levels of grip in hot, dry conditions are desirable. Radial R7 tires are designed to reward drivers with fast, consistent lap times and extended wear due to their traction and handling.

[dparm]

Yeah but isn't the description for the A7 and R7 the same? The compound is different.

[rhyary]

Originally Posted by dparm

Yeah but isn't the description for the A7 and R7 the same? The compound is different.

One is for cooler temp when the tire has a hard tine coming up to temperature.

Honestly, I think this is only important for race situation. I am going with the R7 for two days racing school at Lime Rock. I will be happy to report the difference between the RR and the R7. Notwithstanding the difference sizes.

Hopefully the weather be the same.