Flickery's GTM #72 Track Performance log

[flickery8]

First track weekend of the year at Autobahn Country Club, just south of Chicago, went well. Decided to put this info over here for those that don't check the other forum.

Total car weight with full tanks = 2,812 includes 200lbs added to driver seat.
Front left = 609lbs
Front right = 537lbs
Rear left = 843lbs
Right Rear = 823lbs

Ride height started at 4 1/4" front and 4 3/4" rear, haven't checked since corners set.

Tires are Nitto Invvo:
Front 245/35/ZR19 93w
Rear 345/25/ZR20-100Y

I have installed my new upper control arms from Mike and am very happy with my first track day.

adjustuca.jpg

Gen1 GTM had the tabs in the wrong location and finally there is a fix with mostly off the shelf parts. As you can see, I have finally gotten some good numbers on my caster and camber.


2015 (current)

Front
Camber -1.5
Caster 4.3
Toe 0.14 (1/16" per side)
Rear is same as last year
Camber -0.7
Tie 0.15 (1/16" per side)

2014

1/8" total toe front and 1/8" total toe rear (that is 0.22 front and 0.30 rear with my size tires).
Caster is at 3.1 and 2.7 degrees.
Front camber is -0.6 and -0.2
Rear camber is -0.6 and -0.5.

2013
left front
Camber -0.5
Caster 3
Toe .08

Right front
Camber 0.5
Caster 3.4
Toe 0.2

Left rear
Camber -0.6
Toe -0.3

Right rear
-0.5 camber
0.12 toe

[flickery8]

Had a great weekend in Bowling Green Kentucky at the National Corvette Museum new race track. It is 3.2 miles with 24 turns! There is more elevation change than you can tell from video. Sink hole is crazy, you can't see the track as you go around a corner and drop 20+ feet. Also, top speed was probably 131 mph (set up issues with app has me going 150+). The outer edges of my front tires are bald and all tires are over 5 years old. I could carry much more speed through sweepers with new tires and more confidence. I also need to get cockpit better closed off from engine bay. I have hot air pouring in and it was over 100 with heat index all weekend. Had a lot of fun and I'll go back to this track.

http://youtu.be/CVk2EYg7UuQ

The data overlay is not right in the video. I never get into 5th gear. Top speed was 131.

[kabacj]

Great video Fickery.

The NCM track looks like a lot of fun. I'll definitely make it down there one of these weekends.

Great job! Looks like you are having fun in the GTM.

john

[flickery8]

Road America 2015
Last weekend I traveled to Road America, one of the best and fastest road courses in the country. The track is in Wisconsin, and I was able to stop by in Illinois and meet Ken, the proud new owner of a partially built GTM with twin turbos.

Ken is a great guy with a lot of work ahead. I look forward to taking my car to his shop some time as he has offered to help me tune my engine. It is great to know other people on similar journeys and I think Ken really appreciated seeing a car further along and getting clarity on how some of the pieces go together.

I do have a big upgrade on my car, new tires. I went with Michelin super cup 2 tires, 345/30/20 on the rears and the same size on the front as before 245/35/ZR19. I was worried about the new rear tires rubbing as they are one size taller than the old so I strapped the old tires to the trailer. Well, after leaving Ken's town the tires came loose. After tracking them down we traveled another few minutes before the trucks tire went flat. After a two hour delay we finally got back on the road. We arrived around midnight, giving us some sleep before the the 7 am meeting.

At tech I got the usual questions, and one very inquisitive guy who was instructing in HPDE1 really thought I should give him a ride so he could explain the course to me I obliged and it was helpful as this is a new track for me and the high speeds had me concerned. Now, we took it really easy and for only 15 minutes, but while letting him out of the car at his paddock area (the car idling for only 2-3 minutes) I overheated.

Now, what is very strange is two weekends prior I was at NCM in KY where it was much hotter and I did not over heat the entire weekend. Also, I had not driven the car since that event. But, I did notice my overflow tank was empty while there (in KY) and oddly I filled it 2-3 times to have it only puke about the same amount of fluid at the end of the session. Finally, I just quit putting fluid in thinking it was full and had a lot of expansion. Plus my temps were fine. The only thing I can think of being different is that I noticed I had hot air pouring in (like the cabin was negative pressure at cruising speeds) and so i put insulation under the waterfall blocking off airflow from the cabin to the engine bay. Keep in mind I have that large hood scoop, hood vents and Shane's diffuser vents. I wouldn't think that would be the difference, but who knows.

So, I didn't miss any sessions, but I came in early most sessions and put it into 5th or 6th in the straights to try to cool. I had to take it easier most of the time, but I did post a fastest lap of 2:49 which I am pretty happy with. I know there is a lot of time still out there, but my car and I returned with no damage Here is the link to the video, unfortunately the overlay speed is about 15% high as my top speed on this lap per the gps data was 135 mph. The car could go faster, but I had another concern which I will address in a separate post. Great track and great weekend!

https://www.youtube.com/watch?v=H06qlzlAnT4
__________________
Facebook.com/FastGTM

[flickery8]

At the National Corvette Museum (NCM) road course I was able to keep the pedal down and hit ~135 before braking. The car would start to feel a little darty at that top speed. At Road America last weekend the straights are longer and I did not feel comfortable holding the pedal down or even pushing my hardest up the hill in the straight. Granted, there was a wind, but I think I am just reaching speeds where the aero is coming into play or something is not quite right with my setup.
I think the best way to describe the feeling is, the car feels nervous. Imagine walking your dog on a leash through a hallway of caged dogs. Your dog is headed in the right direction but it keeps glancing at the dangers to the left and the right. It seems like the car and I are on the same page here
To help demonstrate I have uploaded a GOPRO video. TAG appears to have the standard GOPRO case mounted at the top center of his windshield. We would have identical cameras, mounts and cars (or very similar). If you look at the two videos (both compressed by YouTube with the same algorithms) it is apparent my car video is more bouncy even though I am traveling slower. In fact my top speed in this video is 117 mph I believe.

Here is TAG going into the front straight: https://youtu.be/uHDbHdoPJ-M?t=228

Here is me at same point on track: http://youtu.be/LCiDulI0w1w

notice how much more bouncy my video is, or am I nuts?
__________________
Facebook.com/FastGTM

[carbon fiber]

If you're going to run at the track, there are some things that would probably help. 1. Closing off the radiator tunnel to the front bodywork. (The Gen I has a large radiator opening, any air getting between the opening and the radiator tunnel will create lift on the front end) 2. A shock upgrade (The konis aren't really setup right for the car. The genesis shock upgrade is getting good feedback) 3. MAKE SURE you've dialed in your suspension settings. (John and others will attest to how important this is when tracking the GTM) 4. Add some canards to the front end for more downforce. John has done this on his car and he's noted the immediate difference in the amount of front end down force. I'm selling canards for the GTM. I'm making the first set now. They're similar to the ones John bought from FFR but with a slightly different trim shape. Since FFR has shown no interest in selling any more, I'm making them. They'll be in carbon fiber and available SOON. If you have any questions about them now you can pm me. P.S. I saw your thread on the other forum and agree with Tag, you need a rear wing also. The canards on the front will help balance down force with the rear wing in the back. On the street it's not a big deal but at the track the extra down force is greatly needed.

[Cattrax]

Gary,
Your cross weights are good, less than 1% off, and the alignment values should but you in the ballpark. If it is twitchy side to side, I suspect you have a bump-steer issue. It is simple to check (just takes some time to remove shocks) and you can make a bump steer gauge for $5 or less if you have some plywood scraps. You can add a dial indicator to it if you want to be high tech. If you are not in a hurry, bring your car up sometime and we will check it or give me a call and I can walk you through it if you want to check it soon.
Ken

[crash]

Please allow me to give a little advice...don't discount the amount of rear anti squat that is built into the GTM when looking at the bumpsteer. Wink-Wink.

[flickery8]

I do have the bumpsteer kit. Here are the bumpsteer settings. They look ok to me but I'm no expert.ImageUploadedByAG Free1430005354.739631.jpgImageUploadedByAG Free1430005366.501237.jpgImageUploadedByAG Free1430005376.956101.jpgImageUploadedByAG Free1430005386.056681.jpg

[flickery8]

Currently I have the yellow Koni's (not upside down in the front) and MikesPMS upper control arms with FFR Springs.

This morning I was thinking about my new Michelin Sport Cup 2 tires that I have used for the first time last weekend. I was concerned they could rub the rear fender as I went from a 25 to 30 profile. This would affect the ride height. Although the rear did not rub (it is very tight, but I put painters tape on the body and it never got scuffed) I did feel like the front rubbed somewhere if I turned extremely tight (I think in the parking lot). The fronts are supposed to be the same as my old tires.
I decided I should check my ride height as I did not check it when the race shop installed MikesPMS UCA and did the alignment this spring or after putting on the new tires last weekend. Surprisingly the car is now at 5 1/4" in the rear and 5 3/4" in the front. I would think this could be a big deal as it could have a negative impact on front downforce. Looks like I need to redo the entire alignment, corner weights and ride height adjustments. Ken, could you help me with that I used to work with a suspension race shop in Kansas City when I visited my parents, but they have moved away. And although the GM shop was giddy the first time I came in for an alignment, by the third time they just sighed.
__________________
Facebook.com/FastGTM

[Cattrax]

Gary,
I do not have scales, just toe plates and Longacre caster/camber gauge and a level garage floor. Plus my home made bumpsteer gauge. It is not difficult, just takes a little time. I'll be glad to show you how if you come up some time. Then for a modest investment you can experiment with different settings. My wife and I have cars that are for track use, DE's, and Sunday drivers. We regularly switch between track alignment with negative camber and street alignment more straight up. I have done it so many times, I have marked the cam locations and know how many turns of the tie rods for each setting. I usually just check toe afterwards to be sure handling will be okay. Only her's has IRS and on it I just set it with a little negative camber and leave it alone.
Ken

[flickery8]

Ken, I would like to get comfortable adjusting my suspension myself so it is something I should consider. I tried using toe plates once and it didn't go so well.

I am not super excited about spending more money on shocks this month, the tires I just bought were super pricey. But don't get me wrong, I want better shocks

Here is what I think I can do:

1) I don't think -1.6 degrees camber in the front is enough for the track. I may even go from 4.3 Caster to 5+, thoughts?
2) Having the front end sit higher than the back can't help but sitting at 5" vs 4" does cause less scraping bottom of car. Maybe 5.25 rear and 4.75 front?
3) I need to install the front splitter. I don't have the ffr splitter, but rather a "different" splitter. How far should it stick out? I have heard people suggest riveting the splitter may avoid body damage if it is ripped off, but I am thinking I might want to remove it if driving on the street so that it doesn't rub.
4) new shocks may be the solution, not sure

[kabacj]

hey fickery

I think the cheapest and most impactful change you can make to your current setup is to set the Rear bump steer.

Stiffer shocks will help you if your rear bump steer isn't set because the wheels will travel less and bump steer less however getting the rear properly aligned without new shocks is going to make your car more stable.

I was able to get both rear tires to change their toe angle at exactly the same rate.

As crash mentions you can further tune this by changing the anti squat geometry. I have not played with that yet

The GTM is very sensitive to toe changes. It's easy to feel 1/32 of change at high speed. It's a weird feeling that's probably why people blame aero.

When you are traveling down the road over 100 mph with tons of rear tire grip as you go over a dip if one rear wheel turns 1/16 of an inch out and the other does not the car feels nervous. I'm pretty sure this is your issue.

With everything aligned my GTM is one hand loose grip on the wheel stable at 160.

Once you maximize your current setup then you can add springs , shocks , more grip, more downforce more power. It's a slippery slope!

[flickery8]

hey fickery

I think the cheapest and most impactful change you can make to your current setup is to set the Rear bump steer.

Stiffer shocks will help you if your rear bump steer isn't set because the wheels will travel less and bump steer less however getting the rear properly aligned without new shocks is going to make your car more stable.

I was able to get both rear tires to change their toe angle at exactly the same rate.

As crash mentions you can further tune this by changing the anti squat geometry. I have not played with that yet

The GTM is very sensitive to toe changes. It's easy to feel 1/32 of change at high speed. It's a weird feeling that's probably why people blame aero.

When you are traveling down the road over 100 mph with tons of rear tire grip as you go over a dip if one rear wheel turns 1/16 of an inch out and the other does not the car feels nervous. I'm pretty sure this is your issue.

With everything aligned my GTM is one hand loose grip on the wheel stable at 160.

Once you maximize your current setup then you can add springs , shocks , more grip, more downforce more power. It's a slippery slope!

John, I think you are right. You describe the issue I feel and it does seem like ripples in the road at 100+ under acceleration is the problem. I am going to get the rear c5 bumpsteer kit and work on the alignment.
Thanks!
Gary

[Cattrax]

If the above graphs are indeed for the front, I would suggest setting it too.

[carbon fiber]

This is the pic from Johns build thread.8FB4896E-E095-4C70-9EA3-D60BD1D4064F-10047-000014F912D3D436.jpg The bumpsteer kit replaces the c5 toe links with beefier adjustable ones. John, what brand did you buy, where? The cheapest I could find are from RPI Designs - $320. Thanks again for doing all this groundwork for everyone else!

[kabacj]

This is the pic from Johns build thread.8FB4896E-E095-4C70-9EA3-D60BD1D4064F-10047-000014F912D3D436.jpg The bumpsteer kit replaces the c5 toe links with beefier adjustable ones. John, what brand did you buy, where? The cheapest I could find are from RPI Designs - $320. Thanks again for doing all this groundwork for everyone else!

Yep your price is what I paid. I got mine from one of the corvette retailers , but they don't carry them anymore. If you get them I would put a dab of anti seize on both sets of threads on the rod ends. Makes adjustment easier and I had mine gall up and jam at the track. Had to take it out and put lots of torque on it to break it free. With anti seize it's been working fine.

They make for fast rear toe adjustment as well. This is also a nice plus.

[flickery8]

I went back to my earlier post of my bump steer print outs and input the numbers into the calculator here: https://robrobinette.com/ConvertToeDegreesToInches.htm One of the images says total toe while the other says front toe. They look like the same numbers, just doubled. I don't think they measured the rear toe.

Technically we should use degrees rather than inches because the size of the tire will affect the inches but not the degrees. Its pretty minimal if we aren't talking RC cars vs monster trucks.

Looks like my total front toe is at 0.15 inches at rest and fluctuates from 0.33 inches if the suspension compresses 1 inch to 0.01 inches if the car is raised 0.5 inches (almost zero toe).

I don't know how much the car compresses the springs at any point but if I have an inch of compression that puts me at nearly 3/16" per side when I want to be at 1/16" . And what is worse, if the car bounces up over 0.5" I could be going from toe in to toe out. Looking at my bouncy video I could easily be bouncing half an inch up.

I have the front bump steer kit and ordered a rear bump steer kit today. Paid $175 at one of the popular online racing sites. Hope to get them both set before next event.

Thanks guys

[Cattrax]

I think there is two lines on the one that says front toe, one for each side. They look pretty similar, that is good but both are high.
Ken

[carbon fiber]

Which popular online racing site? I haven't bought them yet, any info is appreciated.

[flickery8]

arrived todayimage2.jpg

[carbon fiber]

Thanks. I was hoping for the whole toe link setup at that price, I'd like the stronger links too. Let us know how it works out.

[crash]

Just so you are aware, those are ultra low quality two piece rod ends. They will wear quickly and then allow variations in the toe to occur. It is definitely a personal preference, but I will not put cheap rod ends or bolts on my cars. They both have too important of jobs. That said, we did have to make our own aluminum connecting rods for the rod ends. I believe I have about $600 in the rear toe links alone when it was all said and done. Again, this is a critically important part to tuning and safety, so I used nothing but the best and the rod ends were over $100 each by themselves. Out of that kit you show there the only thing I would feel comfortable using would likely be the ball joint stud adapters...maybe.

[flickery8]

Just so you are aware, those are ultra low quality two piece rod ends. They will wear quickly and then allow variations in the toe to occur. It is definitely a personal preference, but I will not put cheap rod ends or bolts on my cars. They both have too important of jobs. That said, we did have to make our own aluminum connecting rods for the rod ends. I believe I have about $600 in the rear toe links alone when it was all said and done. Again, this is a critically important part to tuning and safety, so I used nothing but the best and the rod ends were over $100 each by themselves. Out of that kit you show there the only thing I would feel comfortable using would likely be the ball joint stud adapters...maybe.

How do you feel about the rpi bumpsteer kit? Since I will need realignment going to have the shop do this (plus I'm going to a shop 2 hours away).

I'm thinking I will go with ride height not to exceed 5.0" in rear and 1/2" rake.

Front

Camber -2

Caster 5

Toe 0.14 (1/16" per side)

Rear

Camber -0.7

Toe 0.15 (1/16" per side) or more?

[flickery8]

Yep your price is what I paid. I got mine from one of the corvette retailers , but they don't carry them anymore. If you get them I would put a dab of anti seize on both sets of threads on the rod ends. Makes adjustment easier and I had mine gall up and jam at the track. Had to take it out and put lots of torque on it to break it free. With anti seize it's been working fine.

They make for fast rear toe adjustment as well. This is also a nice plus.

John, just to confirm, you have the RPI designs bumpsteer kit? I may have time to get that before my appointment at the shop. Here in middle Missouri it is 2 hours to St Louis and I am trying a new shop next week. It's nice because I have to fly to west coast for several days and should be done when I get back. Also, have you run more than 1/8 toe in rear? How was that?
Thanks,
Gary

[kabacj]

John, just to confirm, you have the RPI designs bumpsteer kit? I may have time to get that before my appointment at the shop. Here in middle Missouri it is 2 hours to St Louis and I am trying a new shop next week. It's nice because I have to fly to west coast for several days and should be done when I get back. Also, have you run more than 1/8 toe in rear? How was that?
Thanks,
Gary

Hi Gary.

Yes I have the RPI designs kit. It's all high quality parts. Aurora rod ends , hard anodized aluminum parts. This is key to getting the accuracy and durability needed for high speed track work.

Regarding rear toe, before I set the rear bump steer I ran lots of rear toe. 1/4 inch toe in each side. I think that was just covering up the fact that the rear bump steer was out of alignment.

Now I am running 3/16 or 1/8 toe in each side I believe. I kept taking rear toe out

I'll check my notes tonight.

[crash]

We run very little toe in on the rear. 1/8 or less TOTAL, IIRC.

[flickery8]

So, I had a shop swap out the rear toe links with a bumpsteer kit, then set ride height, bump steer, corner weights and align. Before I get into all that, I want to compare what my last alignment was (according to that shop just five months ago) and what this shop say my alignment was when I brought it in this weekend. Both of these shops claim to be racing garages. Should be the same, right?

Numbers I got in the spring
Front
Camber -1.5 / -1.6
Caster 4.3 / 4.3
Toe 0.14 (1/16" per side)

Rear
Camber -0.7
Toe 0.15 (1/16" per side)

new shop says I had

Front
Camber -1.2 / -1.5
Caster 3.5 / 3.5
Toe 7/32 / 5/32

Rear
Camber -0.6 / -0.8
Toe 5/16 / 19/32

I don't know who to believe, but thought it was interesting. Something to consider when having you car aligned.

[flickery8]

alignment September 2015
here are the latest numbers I am going with

Front
Camber -2.0 / -2.0
Caster 4 / 4
Toe 1/32 / 3/32

Rear
Camber -0.7 / -0.7
Toe 1/8" / 1/8"

I wanted 1/16" on each side on the front and 1/8" on rear, not sure why the front numbers I got are mismatched.

I also had the bump steer set. I have the ffr front bump steer kit and the RPI designs rear kit (not the cheap one I posed pictures of), numbers attached. Start means before adjusting and finish is where we left it.
https://www.dropbox.com/s/xkzae9is1z...02015.PNG?dl=0September 2015.PNG

[kabacj]

Regarding your numbers. I normally can get the same measurements from alignment to alignment, but i am using the same tools with the same process. The numbers your two shops got were not wildly off. Depending on your setup and how firm your adjustments are made, cam adjusters vs plates and even the stiffness of your bushings can result in significantly different readings. Any pre load on the bushings and your readings are not exactly the same. Worn parts are also a culprit for variability.

Sounds like you made some good adjustments and you will eliminate some variables with your new setup. Im interested to hear what you think of the changes.

[flickery8]

Struggling at Autobahn today. First time out with rear bump steer kit. Also had front bp steer adjusted and car cornered and aligned. It feels the worst its felt all year.



Took the car out on track this am. I first noticed car turned very very easily. Felt like power steering.

Later found, When I get on the gas on the straights and hit a bump or ripple the car gets extremely springy. In fact, it feels like a hula hoop where first the front right dives then the spring pops up and passes the energy around one by one to each spring. Another time car felt like a bronco bucking left right left. This is while going straight and giving gas and hitting any bp. Had to pit the car.



I thought maybe my big new tires rubbed the rear fender so I raised ride height 3/8" in rear but problem is still there. Now I notice exiting corners car is very springy. Will bounce 2-3 times and skip some. Brakes seem to lock up easier also. But only is the straight line acceleration intolerable.



Help! Still have tomorrow.

[flickery8]

I saw that I only had about 1/16" total toe on front. According to my alignment shop left has 1/32 and right 3/32". Decided to add 1/16" to left. It was near impossible to turn that tie rod. Took it out and felt a tiny bit better but still can't drive fast. I'm adding 1/16 to right front this time. This side turned much easier. It's funny how I did t notice this on the highway, but it's nearly un-driveable

[flickery8]

Well, maybe it is the rear. Finished my last session. Car was hopping from right to left on fast straights on acceleration. I think I had bump steer
before and that felt like the car kicking hard to one side. This feels like bouncing to one side, then the other then back. Very springy.

[crash]

About the only thing I can tell you for sure is that these cars are very sensitive to changes in suspension adjustments and ride height. It may feel scary until you work the bugs out for what is comfortable for you.

[kabacj]

Hi

I second what crash said. The GTM chassis is very responsive to suspension tuning.

I assume you got rid of your cam adjusters that mount the lower rear A arms? They are a problem item on tracked corvettes and the GTM on the track overwhelms them.

[GTMsomeday]

Hi

I second what crash said. The GTM chassis is very responsive to suspension tuning.

I assume you got rid of your cam adjusters that mount the lower rear A arms? They are a problem item on tracked corvettes and the GTM on the track overwhelms them.

I agree. I have also had bad luck with alignment shops NOT torqueing the cam bolts properly. Get Mikes shims. Good Luck

[flickery8]

I am certain I will need to install Crash's shims on rear (only put them on front).

At this point I am pretty sure the issue is rear steer. I had several mechanically inclined racers at Autobahn check out the play on my tire (wiggling laterally with hands) and all said it was way too much. This is the case on both wheels. They also crawled under the car while I wiggled and they all pointed to play in the new tie rods. Unfortunately it is unclear what part is moving (well it all moves but not sure why). I tried to tighten everything, but the chassis mount is hard to reach and it spins (though it did tighten more). Also, someone suggested the bolt may be smaller than the hole (where it mounts to chassis) and therefore has some play.



Also was asked if the kit included any bushings for that joint. Were there instructions? I will have to ask the shop.



Does the orientation of the ball joint matter? I can rotate it so the bolt is at a 3-9 o'clock orientation or any other.



As u can see in this video with car on ground I can rotate tie rods. http://youtu.be/IyCVhOedy8A

Is that normal?

[Erik W. Treves]

it is hard to see with all the shaking of the camera..lol... those can rotate as part of the joint but there should be no radial play in those heim joints

[Fraser D]

As per other forum,

There are no additional bushings as the unit is complete.
As for tightening the inner unit to the chassis you will need a spanner on both sides to make sure that it is tight enough. It should not continue to spin.
You also have the inner tie rod in the wrong orientation. It needs to be rotated 90 deg to allow full joint travel. It looked to me that mine would bind close to full suspension travel when in the orientation that you have.
In the picture I have not adjusted the bump steer yet so don’t worry about my shims all being on the wrong side of the tie rod.

[crash]

Just a heads up...the rear toe links take some pretty extreme loads. I just got through doing some major reworking of this area on the FFR PDG GTM race car. We simply could not keep the additional "kickers" that we added to the back side of the toe links from causing cracks in the X brace at the rear of the frame. If you have not added the kickers yet, it is a requirement, but then you need to watch out for X brace cracking as it becomes the next weakest link. I'll post a pic soon...maybe just on the other forum.