GTM Speed envelope

[BS]

Now that the GTM has had several years of shakedown and several teams have taken serious racing with this chassis, what is the consensus for the upper limits for speed for this car? What seems to be the obvious limitations and/or remedies to reach the next level? Has the chassis and drivetrain proven to be up to hard core racing for an entire season or are major modifications required to keep it together and competitive? Have there been any surprises along the way of developing the race chassis and drivetrain?

Just some random curious thoughts. I'm starting to wonder how the 818R is developing in this area also and what others have found but that is another forum....

Bob

[crash]

As far as top speed goes, we have gotten the FFR PDG GTM up to just over 150 MPH, but that has been limited by track straight away length and also the fact that we have significant amounts of down force on the car. We reach over 2 Gs in the corners.

There were some issues with suspension cam bolts, the cooling system, rear toe link mounts, and shock mounts. Basically all just a strengthening issue to last through 25 hour long races. All in all the GTM performs really well and is extremely durable. Yes we have had to replace some tubes here and there due to "racing incidents" but that was also pretty easy to accomplish. The GTM is relatively easy to work on and the LS power plants, combined with the Mendeola gearboxes, just keep going and going. With the exception of a couple of items on the engine, the drivetrain, with LS engine and Mendeola transaxle is pretty much race ready and, for us, race proven, at this point.

We had really wanted to help develop the 818R and there were some negotiations going on with FFR to do so, but those never materialized. It would have been a fun project and I think both team Prototype Development Group and Factory Five Racing would have benefited greatly from the partnership, but we simply have not heard anything after we sent over our proposal to Dave Smith(which he requested). It would have been fun, but we continue to dominate with the FFR PDG GTM in endurance racing.

This year we will also be running the United States Touring Car Championship(USTCC) with the FFR PDG GTM and those races will be televised on MAV TV, so keep an eye out for the red white and blue FFR PDG GTM!

[kabacj]

BS

The upper limit depends on how you build it. The only thing that limits how fast you can go is your skill as a builder and your wallet.

You will find that builders are happy to share what they have learned.

After a few years of building and a half a year of racing. I would not trade my GTM for any other car on the grid.

I think that sums it up.

John

[flickery8]

I think the key to going faster is finding a longer staight and having a death wish. I have been in the 140's, but most days i try to not exceed 130 as it can be unsettling. This is all at the race track. It takes years to tweak the suspension and aero, that is after you spend years building the car. Like John said, you can go as fast you want in a GTM.

[Fraser D]

I agree with John, as a base platform the vehicle is awesome!
Just like any production vehicle if you start turning up the performance wick you will need to upgrade from stock.
If pushing the cars potential the stock suspension will be your first upgrade and you will need to pay close attention to the alignment settings.
The biggest weakness in exploiting the true potential of this car is the lack of real world data.
Chevy, Ford, Audi, Porsche, etc have the benefit of multi million $ development departments plus the benefit of thousands of vehicles in the field.
Team PDG has the most performance experience and passes on what they can but they still have to maintain a competitive edge so they keep a "few" things to themselves.
There are others like Quicktime and John who have comprehensive threads documenting their findings but the rest of the combined forums will chime in as needed.
I still have the stock FF5 suspension and have had my GTM up in the 160's in a track but worked out very quickly that those speeds require refinements in settings and upgrades in equipment in order to repeat that speed "safely".
All of which will take place over the next couple of months.
I guess that what I am trying to say is that the base chassis the car is sound but in regards to suspension and handling you will have to treat it like any scratch build track car and revert to suspension fundamentals to guide your setup.
Measure, adjust, test.

[flotowngtm]

There once was a guy that hit 175.4.................. but then he crashed!!

I hope mine is set up right, it will be on some airport runways next year. Still have a lot of work to do on it thou.

[FFR514]

There once was a guy that hit 175.4.................. but then he crashed!!

I hope mine is set up right, it will be on some airport runways next year. Still have a lot of work to do on it thou.

That guy was me.... I was on a runway at the Texas Mile event. It definitely takes a lot of time setting the car up and testing to get ready for high speeds (150+). I learned the hard way. I for one won't be testing mine on high speed runs again mainly because I don't think it is worth the risk. The car is too nice and too much fun to spend time rebuilding and fixing bodywork.

FYI - I was running a splitter up front with no wing in the back which isn't a good combo for very high speeds. I also had the old, gen 1 upper control arms setup which limited the caster. I rewelded the uppers to the new GenII location.

I wonder if anyone has gone faster than me yet in a GTM at a standing mile event?

Rich

[kabacj]

I hope mine is set up right, it will be on some airport runways next year. Still have a lot of work to do on it thou.

Hey flow town! Good to see you.
Shane builds a great car, but I don't know if he delivered yours with a race alignment. It only makes sense that if you take a bunch of parts from one or many c5 corvettes and assemble them in a package with double the HP you get higher performance you need to take extra care you have the setup you need.

If you plan to do 130+I would get the car properly setup. You can get along with just a basic alignment as I did and be lucky you were close enough. If I did it again I would have just learned how to setup the car out of the gate. I'm learning now.

Be mindful of your toe and bump steer settings. These need to be addressed on a lowered c5 too.

[flotowngtm]

Yes they really should repair the end of that runway! Its cost to many good cars there good looks! If it wasent for that stack of tires sitting there out of no where you would have came out of that without a scratch!

Hey Kabacj! Yes your right its a good set up but in no way dialed in. I have a lot of work to do with that and the car in general. I swear every time I come home and bring it out of the garage something else is leaking or broken or making noises. But getting the alignment right and some down force on my front end "as its basically stock" are going to be priority number one! I wont be going all out on the first day like most. 5-10 mph faster on every run to see how it handles.

[Ojref]

I have to say, I've been pretty taken aback by this thread. 130 MPH for the GTM is unsettling? 150+ is untested???

I've been up to 140MPH in my Ford Lightning. While not exactly "planted", stable enough to safely run around a big NASCAR track. I've really been anticipating this car as being the "supercar" experience that was touted. If it's having issues breaking 130 without serious configuration, I think I'll stay with the vette, which I know is pretty good past 170+. This news is really unsettling and disappointing, but better to know this before making the purchase in any event. Unbelievable.

[bbjones121]

I have to say, I've been pretty taken aback by this thread. 130 MPH for the GTM is unsettling? 150+ is untested???

I've been up to 140MPH in my Ford Lightning. While not exactly "planted", stable enough to safely run around a big NASCAR track. I've really been anticipating this car as being the "supercar" experience that was touted. If it's having issues breaking 130 without serious configuration, I think I'll stay with the vette, which I know is pretty good past 170+. This news is really unsettling and disappointing, but better to know this before making the purchase in any event. Unbelievable.

I had my subaru svx up to 140 and it felt planted. I thought the gtm was a 200mph car!?! My 818 better be faster than my svx was. I know it will be quicker, but come on, it should still be faster.

If the gtm is anything like the 818, there are definitely places on the body panels that need more support. I am welding up more support points for the body so that i can see how fast it will go and not worry about the body flying off.

[kabacj]

I have to say, I've been pretty taken aback by this thread. 130 MPH for the GTM is unsettling? 150+ is untested???
(

Hi Ojref

As you do more research and learn about building a GTM. The GTM is certainly capable of supercar speeds right out of the box.

However you do need to give it a quality 4 wheel alignment. (Just like every factory super car and production car has )

A quality alignment is not the one you get at the local tire shop.

A street alignment is at least good for 130.

I'm not saying you need to bring your car in for a race alignment either. I never did an alignment in my life before the GTM. And with the proper tools have setup my car quite well. The important part is knowing what to set.

My GTM has seen 163 (GPS verified) running at Virginia International Raceway. I am just switching into fifth gear at that speed and the car is rock solid stable.

I think we as a community have learned that if you go out and try to set land speed records without setting your rear bump steer you might have some issues.

If you decide to build a GTM you will find that the community is here to help with any problem you might come up against. Others can tell you about how they solved the issue you have and you can choose the solution you like best.

Thanks for as asking the question. I think you have helped clear up a common misconception.

John

[carbon fiber]

I have to say, I've been pretty taken aback by this thread. 130 MPH for the GTM is unsettling? 150+ is untested???

I've been up to 140MPH in my Ford Lightning. While not exactly "planted", stable enough to safely run around a big NASCAR track. I've really been anticipating this car as being the "supercar" experience that was touted. If it's having issues breaking 130 without serious configuration, I think I'll stay with the vette, which I know is pretty good past 170+. This news is really unsettling and disappointing, but better to know this before making the purchase in any event. Unbelievable.

As John mentioned, it's all about the setup. Out of the 400 plus GTMs produced by FFR there are only a handful that have been on a track and their owners are taking the time to get the suspension and aero properly prepared. It's a work in progress. None of the Gen I cars have the upper control arm mounts in the right place and they will need to be relocated or have adjustable upper control arms to replace the vette ones to get proper caster. There are several other things, bump steer kits, aero, proper alignment, etc. that will dictate how the car performs in the end. Please check out some threads and get informed before making blanket statements and discouraging others with your first post. Fran Hall, IS THAT YOU?!!!

[crash]

As John mentioned, it's all about the setup. Out of the 400 plus GTMs produced by FFR there are only a handful that have been on a track and their owners are taking the time to get the suspension and aero properly prepared. It's a work in progress. None of the Gen I cars have the upper control arm mounts in the right place and they will need to be relocated or have adjustable upper control arms to replace the vette ones to get proper caster. There are several other things, bump steer kits, aero, proper alignment, etc. that will dictate how the car performs in the end. Please check out some threads and get informed before making blanket statements and discouraging others with your first post. Fran Hall, IS THAT YOU?!!!

+1

Some other things to consider...we could get our FFR PDG GTM race car to over 170, I believe, pretty easily. The problem is that we cannot do that on a relatively short straight away and with the down force we are creating that allows us almost 2 Gs in the corners. The other thing to note is that in EVERY case where we have been on track with "supercars", some that claim well over 200MPH as a top speed, we pretty much wipe the track with them. Corners, down the straights, everywhere. As I have related before, we had the opportunity to run with a street licensed Corvette in Seattle that was hitting over 150 down the long front straight at SIR and we were limited to 130 because of gearing. We had almost the exact same lap times. Top speed is one thing and going fast is another.

[flickery8]

I should not say it is unsettling to go over 140 mph in a GTM, that was my mistake. In my car right now, that is where I am. If you want to drive really fast down the interstate and you don't like wrenching and tuning you should get a corvette. I tell people building a kit car is like a building a house. It can cost as much as you want. It can have the bells and whistles you want. It can do most anything you ask of it if you put in the time, money and effort. If you just want to go 200 mph, I think you can rent a NASCAR many places now. If you want to know your machine inside and out and improve it year after year maybe a kit car is for you. If someone decides to build a GTM to go straight and fast I am sure they will hit 200mph easily, I just don't know anyone trying to do that. My car has the HP and gearing to do 200mph given a long enough straight. When I say I don't feel comfortable going over 150mph yet, keep in mind I am doing this ALL DAY LONG on a race track that has a 90 degree turn at the end and cement walls on each side. I believe I will be comfortable at higher speeds as I fine tune the car.