GTM roll cage modifications and race car build log

[GTM RACER]

I have been using galvanized heat shields for years now on the GTM. Except I took the metal, folded it, added 3 layers of fiberglass cloth inside and hemmed it. Bent the edges for the stand off and hose clamped it to the muffler. Dropped the temp on the CV boot about 120 degrees. Also, using the heat wrap...follow the directions and you won't end up with a pile of fragmented cloth you can never use! Soak it in water, then wrap, let dry, and paint with high heat aluminum paint(2000). My wrap looks better after a year of racing than when I installed it.

[kabacj]

I have been using galvanized heat shields for years now on the GTM. Except I took the metal, folded it, added 3 layers of fiberglass cloth inside and hemmed it. Bent the edges for the stand off and hose clamped it to the muffler. Dropped the temp on the CV boot about 120 degrees. A

Yep that's a good idea. I considered doing the layers at the track, but with the limited time I had, I figured I would just try the single metal shield. Seems like it also works with just metal. I have plenty of air circulation right now too. I am sure that helps.

I have one more weekend planned this year Nov 3-4th. I think ill go with the single metal layer for now if I cant delete the cats all together. Over the winter Ill fab up a two layer setup with insulation for street use.

Thanks for the suggestion on installing the wrap.

John

[kabacj]

A friend of mine captured a sequence of the GTM motoring down the front straight. I like the silhouette of the GTM vs the 911. Everybody likes pictures so I thought I would share.







John

[LCD Gauges]

A friend of mine captured a sequence of the GTM motoring down the front straight. I like the silhouette of the GTM vs the 911. Everybody likes pictures so I thought I would share.

I like how he conveniently waited until you edged out the Porsche in the last photo.

[RumRunner]

John,

Great photos! Definitely calendar material!

-Michael

[Kempo]

Great sequence. It really shows the speed difference between the other cars and you. In that short distance you managed to catch and pass them.

[VD2021]

I really love the angle of the first picture. ......keep them coming.....

[kabacj]

Thanks Tino , Michael, Hugo and Vidal.

The GTM does have such wicked acceleration. I am still not using all of the car but you can see in this quick clip how easily I catch up to the other cars out on the track. Note that these guys are not slow. I was running with the fastest group comprised of racers and instructors.

[kabacj]

Last trip to the track this happened.


I put a wheel off on the outside of a corner where everybody goes wide. That means after you go over the curb there is a rut where the dirt starts.

Unfortunately with the car so low the splitter hits the deck pretty quickly. A little annoying but I knew it was only a matter of time till I had splitter damage.

Since I'm back on the track tomorrow AM a little duct tape and im good to go. It's sad to put a pretty carbon fiber piece in harms way. But I'll just fix it and recover with a new layer of carbon fiber.

John

[LCD Gauges]

It wouldn't be a real racecar without some war wounds!

Kinda reminds me of Colin Chapman's famous quote.

[kabacj]

You are right Tino war wounds are part of going to the track.

I am very happy to report the splitter was the extent of damage for the year.

I did my best to tempt fate this past weekend however.

My toyo ra1s have over 500 laps on them with at least 45 heat cycles. They were still sort of working last weekend but knew they were well past their prime. I just planned to take it easy. Lack of traction would help me tune the suspension for wet/ cold conditions. I'll just take it easy it will be fine. ( I kept telling myself that.)

Sat am was beautiful. 50 degrees and sunny. The track was damp from rain the night before.



No worries. I'll just do two warm up laps. Out on the track at 9.30.

I was running with the instructors so everybody had the same idea. Make sure you have good tire temps before you start pushing.

I was moving through traffic after a few laps and I see a guy in my rear camera pushing me. No problem buddy. Be my guest. I move off line and lift to let him by.



Holy crap! It's a c7 corvette. I had heard about this guy. He is a local dealer and a member at the track. I guess he comes down to the track with his demo for a few laps before work.

So much for taking it easy. I gotta see what he has. Yes the c7 has a billion gizmos to keep him out of the fence but I have horsepower! That will work right?

Needless to say I had quite a few hair raising moments. But it was so much fun. I drew the line at attempting to pass him since I did not want to be "that guy"who takes out a c7 on the track.

I'm on my way to the show at SEMA so I'll post some video when I can.




I'll be looking for ideas (and tires) for the GTM. I'll post anything cool I find.

John

[carbon fiber]

all I want from that car is the engine!

[VD2021]

J,

Very Cool. Loving the write-up.

[Stage7]

Great read John!

[kabacj]

Great read John!

J, Very Cool. Loving the write-up.

Hey Stage and Vidal. Glad u enjoyed the story.



After my last track day followed immediately by SEMA I had a nice queue of non GTM things to take care of.

Now that I've sorted those things it's back to the GTM. This weekend was wiring the headlights and turn signals. Pretty boring stuff but the DMV thinks its important so I do it.

While at SEMA i had the opportunity to scour over some top level race cars. One of the cool things, for me anyway, was to see the methods and materials used by grand am and other top teams are the same as we can use. It's not like these guys have a multi million dollar F1 budget to develop parts using the best stuff money can buy. These teams just make things that work with what they have available.

One of the items I will focus on over the winter is aero. As a general rule if you copy designs that work it's possible to at least getting the ball park of a good design.


Here is a compilation of pictures of designs that I think I can modify to work on the GTM


Here is a picture of the pikes peak hill climb car developed by Rhys Millen.



Note the rear diffuser.



Here is the diffuser on a racing version of he Lamborghini Gallardo.


The rear window louvers on a racing audi R8



Audi also uses a rear camera to see out the back. ( I really like the camera for rear view in my car)



Check this out.




It's ok to use plywood on your car. This part on a Daytona prototype gets sand blasted into oblivion every race so making an expendable part works I guess


BTW I tried to get continental to give me a few sets of racing slicks. No dice. They only supply top teams. Oh well it's not really practical anyway as I would develop a race setup around tires in limited supply. It would be cool to run them however even if it's just for the physiological effect on the other racers.

Finally a cool spoiler idea. It's not going to be as easy to fabricate since the deck lid on the GTM is a little more complex then a DP car.




I know the air stays attached to the profile if the rear of the car. Using a deck spoiler I think I can run top speed events without a wing at all. Lower drag is a significant advantage over 150 mph.


I got a few other cool ideas. I'll share them as I try to implement them.

John

[kabacj]

After about 500 laps my toyo RA1s are toast. For my last track day I needed to flip the tires from left to right to extend the tread life one more weekend. That really did not work as well as I had hoped. I only got a day and a half before traction really fell off a cliff. It was surprising how drastic the change was but it's good to know what it feels like. Since I'm not racing it really does not matter how fast I go as long as I can control the car. Every weekend so far I drop a few seconds as I learn the car. New tires have not been a priority.

The front left took a pretty hard beating all year. The front left is most often most heavily loaded as its usually the outside tire on clockwise tracks.



The front right looks a little better as it has an easier life as the inside tire on most corners.


The right rear inside wore more quickly then the outside. I'm not sure how this will work , but next year I am going to experiment with less negative camber on the rears in general but the right rear I'll have even less camber. As I make right turns the inside rear naturally gets more negative camber. It then wears the inside of the right rear.

See how the inside of the right rear is worn



The left rear is a little better but still has too much negative camber I think.






Next year I'll also have two sets of tires mounted with me at all times. This way I can swap out out the spent ones before I totally run them to nothing.

It's good to know that even when the tires were junk they are still drivable. Example I ran 1.7 g in July. Then 1.3 g in September and could barely pull 1g when the tires were spent . The GTM was very drivable under all conditions. Definitely got my attention when the tires were going off but it did not do anything evil. Once I slowed down to 70% pace the worn tires were fine.

The only comparison I know is running motorcycle racing slicks past their usable life. Most of the time I crashed. Its funny now that I think about it. It's rare that I was able to catch a slide on a spent motorcycle tire. With a car you get so much warning. Even when I over cook the corner in the GTM I have eons to save it.

Bikes are more fun and scary, but now that I have a little sense from old age, I realize there is something to be said for fighting another day without the drama. I'm very happy in the GTM. Only 100 more days till its track time!

John

[fastthings]

I think it's cool that it held up, and ready for another set. Good job!!!

[crash]

Might I suggest that you use a tire temp gage to fine tune the suspension? I really think you are to the point that wear patterns and tire temps are going to make or break your ability to get some extra life out of your tires. That said, sometimes they just time out or cycle out. I know with the Kumhos we get about 6 hours or about 13 heat cycles(which ever comes first) before they are toast. We haven't found anything that holds up better with good performance. We have seen 1.9 Gs.

[kabacj]

Might I suggest that you use a tire temp gage to fine tune the suspension? I really think you are to the point that wear patterns and tire temps are going to make or break your ability to get some extra life out of your tires. That said, sometimes they just time out or cycle out. I know with the Kumhos we get about 6 hours or about 13 heat cycles(which ever comes first) before they are toast. We haven't found anything that holds up better with good performance. We have seen 1.9 Gs.

Yep agree Crash tire temps and pressures will be important. I got the tires in a happy place where I had reasonably fast even heat up across the contact patch and the tires would not over heat in a half hour session. So many things (mostly me) were changing each session. Its very hard to get good data regarding what actually is faster. I was just going faster each day i went out regardless of if the car felt better or worse. This year i expect ill hit a plateau on my lap times and it will be easier to fine tune the car.

Since the RA1s in the 335 size are way out of production. I will not get them next season. I think im going with the BFG R1s and a set of toyo R888s for the occasional damp track.

I know the Kumho Ecsta V710 is also a good tire. I think they help you guys out which is cool. I figure my choices are the V710, BFG R1, or Hoosier A6/ R6. Im going with a soft slick for the early spring when track temps are low. Ill have the R888 as my street tire/damp/ wet tire. Then go with a hard slick for the summer and switch back to a soft slick for the fall.

You are right that setting up the camber of the car for the track is a step beyond optimizing the temps with pressure. I actually think that since the GTM has more spring now then it did when i started I might get less roll induced camber change.

I am going to add more caster to the front as well as add more tire width in the front. Ill use a 255 for the R888 but not sure how big I should go on the slick. 275 maybe? Not a lot of data from what works for other guys unfortunately.

John

[crash]

We seem to have trouble getting temperature in the front tires...you obviously do not. I think anywhere between a 275 and 295 would work for you depending upon compound. We are messing with A6/R6 combos and sizes right now to try and find a happy medium.

[Fugly_Old_Cowboy]

I might have missed it somewhere since I was kind of outta pocket for a while.... did you ever get fully cleared to race with your roll cage mods or are you still pushing that freight train up that hill???

[kabacj]

I might have missed it somewhere since I was kind of outta pocket for a while.... did you ever get fully cleared to race with your roll cage mods or are you still pushing that freight train up that hill???

Hey Cowboy

I'm just getting a head of steam before I really start getting the train rolling to extend your metaphor.

I needed to tune the car for racing. Far from done there, but I'm getting closer.

I needed to learn to drive fast enough to be in the game come race day. Good progress there.

I need my racing license. That happens this May.

I'm really going to push the next few months.

I don't give up easily. I'll find a way and be sure to let you guys know how I do. Ill ask for help from the group when I hit road blocks.

We will get it done this year.

John

[Fugly_Old_Cowboy]

just a thought.... I live about a hour away from (pretty much anything) Texas World Speedway in Bryan/Collage Station & a little over a hour in the other direction from Circuit of America track in Austin...
I know for sure the B/CS track is used extensively by NASA for events as well as HPDE... I was thinking of bringing the naked frame down there & having their tech guys tell me exactly what else is needed to pass their tech for racing.....
good idea???

[flotowngtm]

Just be prepared for a long conversation when they see the frame.

[Fugly_Old_Cowboy]

Just be prepared for a long conversation when they see the frame.

I have NO problem talking with folks with the same basic mindset.... even if our view differ.... (as long as they don't mind having to figure out my hick-enese speach patterns)...

[kabacj]

. I was thinking of bringing the naked frame down there & having their tech guys tell me exactly what else is needed to pass their tech for racing.....
good idea???

Sure more feedback is better, however it's the national safety director that needs to sign off. My local NASA guys agree the frame as I have it built is stronger then many approved cars, but it really doesn't matter what they think. They only enforce the rule book. They can't make a judgement on it. Approval of a new frame boils down to liability and insurance.

John

[Fugly_Old_Cowboy]

Sure more feedback is better, however it's the national safety director that needs to sign off. My local NASA guys agree the frame as I have it built is stronger then many approved cars, but it really doesn't matter what they think. They only enforce the rule book. They can't make a judgement on it. Approval of a new frame boils down to liability and insurance.

John

that's what I'm thinking.... bring the frame to the guys that enforce the rule book & have them tell me exactly what it needs to meet their specs... rather than build my interpretation of the book & hope it fits theirs...

[kabacj]

Its been a while since I did any fabrication as my recent focus has been on the electrical required to make the car street legal. It was time for some metal work.

I like to extend my track day as long as possible. That means sticking around till the last runs of the day between 5 and 6 o'clock. When I finish that late there is a premium on getting the car loaded and tied down as quickly as possible for the 3-4 hour drive home. There are not any easy front tie down points on my GTM. Some people tie the car down using the suspension or wheels, I don't like doing that as I think its pretty easy to pull one wheel out of alignment. I ended wrapping an axle strap around the front suspension mounting tabs and using that as the best attachment point that had the least chance of changing the alignment.

Problem is this was 10 or 15 min process to get everything tight. When you are tired and in a rush not a good exercise to go through. My buddy on the other hand was finished with his car in 5 min. The corvette has these little pockets that accepts hooks that will not fall out. These points are used for shipping and make it very easy to tie down the car.



I figured putting these tie down points right under the front two corners of the frame under the door hinge. I will have both a strong tie down point and an attachment point that is easily accessed in the trailer. The other nice thing is the brackets act like a gusset increasing the strength of the corners of the frame.

I cut two brackets from 3/16 plate steel.



Verified the fit of the hooks.



Then tig welded them in.



It works! I am going to get tie down straps with the hooks built in so once the straps are attached they can't fall off.



John

[Taz Rules]

Hey John

I sent you a PM

Taz

[fastthings]

Awsome, that looks like a good add on.

[Fraser D]

John,

What are they called or listed as?
Great Idea.

[kabacj]

John,

What are they called or listed as?
Great Idea.

Thanks Dave.

This style of hook is called a 'T hook'

Corvette sites have the t hook with the strap attached.

John

[Roger Reid]

Found them the link at Northern Tool is

http://www.northerntool.com/shop/too...Search=3309048

[Presto51]

Hey John,

X10 what Dave and Gene said, plus my .02

MHO is that this not only a must have fabrication/add on for towing but, like was mention on the Northern Tool site, great tie down points when going to the dyno

Thanks for sharing

Ron

[Fraser D]

I will be paying Northern Tools a visit this weekend.
Thanks guys! This has been an issue lurking in the back of my mind for awhile.

[mikespms]

http://www.ecklerscorvette.com/corve...1997-2012.html

You can use this jacking pads in the same slots but you will need a very low profile jack or have a suspension lift system.

[VRaptor SpeedWorks, LLC]

Maybe I'm missing something here......but in my experience, nearly every single tie down ratchet strap sold has a big formed "double hook" sewn into the end of the straps. It looks to me like that hook would probably be too wide to work with the T-hook pictured here......and since the strap already has the hook built into it......why the need for the T-hooks at all? Why not just cut the holes in the plates so you can hook the strap directly to the plate and be done with it? Seems like a cheaper, easier, faster, more reliable and simpler solution to me.....with no parts to lose. Cut the hole in the plate so it could accommodate the strap hook, a tow strap hook, a log chain hook....and then you're covered no matter what you have on hand to tie down or tow with.

[VRaptor SpeedWorks, LLC]

Out of all of the transport companies and dynos that I've dealt with, I'd say 95% of them used these straps with this style of hook right here:

http://www.lowes.com/pd_329585-50881...7C1&facetInfo=

And the other 5% used straps that go over the tires.

[kabacj]

Maybe I'm missing something here......but in my experience, nearly every single tie down ratchet strap sold has a big formed "double hook" sewn into the end of the straps. It looks to me like that hook would probably be too wide to work with the T-hook pictured here......and since the strap already has the hook built into it......why the need for the T-hooks at all? Why not just cut the holes in the plates so you can hook the strap directly to the plate and be done with it? Seems like a cheaper, easier, faster, more reliable and simpler solution to me.....with no parts to lose. Cut the hole in the plate so it could accommodate the strap hook, a tow strap hook, a log chain hook....and then you're covered no matter what you have on hand to tie down or tow with.

Hey Shane,

I agree with you the wire hooks are more common. The hooks you link to would be the universal setup. Thats the type I use now. The cool thing about the T hooks is that they dont fall out. If I cut a slot to accept the wire hook they might stay in , might fall out. When im in the enclosed trailer trying to get everything sorted and in a rush they ALWAYS fall out/ fall off. On an open trailer/ dyno would not be such a pain.

Once you put the T hooks in and turn them 90 degrees in the general direction you are going to tighten the straps they can't fall out. I will replace the car side of my tie down straps with sewn in rings/t hooks. The T hook I have pictured was for mock up purposes .

http://www.autohaulersupply.com/cata...color-5206.php
Hope that helps.

John

[kabacj]

http://www.ecklerscorvette.com/corve...1997-2012.html

You can use this jacking pads in the same slots but you will need a very low profile jack or have a suspension lift system.

Hey Mike,

I would definitely need a suspension lift setup to use jacking pads. At my ride height i cant even get a low profile jack under the side sill of the car.



It would be cool to get a set of pneumatic jacks to lift the car, but i still have lots to sort out before I get to a project like that.

For those that have a normal street ride height the pads are a good idea.

John