Davemk1

Just a nice shot of my Birkin in a high speed slalom in Helena MT. That's all I got. Dave http://www.usa7s.com/aspnetforum/upload/784047572_IMG_1582.jpg

As much fun as the real high HP cars might be I hope folks don't get the feeling that one needs big HP to have fun or to be competitive in motor-sport. I drive a Birkin with a pretty stock Zetec that is putting out 136 hp at the wheels. Small numbers I know. At the same time it's a ball as the power is so controllable and easy to modulate. Yesterday I did an autocross event in Helena with a very open course. The vast majority of the course was in 3rd gear with my foot to the floor. There were 75 mph lane changes and slaloms and a top speed of more than 80mph. Mine was the quickest street car there and the only thing that beat it was a F-Mod Red Devil. Also there was a very good driver in a hopped up ZO6 on R compound tires that I managed to put over 3 seconds on on a roughly 80 second course. His 500+ hp did a great job of letting him lay down some serious black streaks but in the end proved slower than my little low HP car despite his HP/weight ratio being much better than mine. I say it's all good and whatever makes you happy you should do. If you want 500 hp in a car why not. But you don't NEED that much power to get the job done and in some cases the HP can make it more difficult to get the most out of a car. One can have too much of a good thing IMO. Have fun, dave

38" maybe not. Dave

www.kirkframeworks.com dave

Hey there, The pleasure was all mine with your visit. The ride with Joe was great and hanging and talking for a bit with others that understand the Seven thing was really fun too. You all are welcome anytime. dave

So my Birkin finally got some new kicks (wheels to us old folks). I previously had the stock Birkin wheels which are silly heavy and in my case not so round. So I got these new wheels from Good-Win racing. They sell Miata stuff and had the magic combo of 15 x 7 with a 30mm backspace and at a very reasonable price. With lightweight and round wheels mounted it's uncommonly smooth now. I took this photo this evening as the light was so sweet and had to share. All the best, Dave http://www.usa7s.com/aspnetforum/upload/1529439625_DSC_0141.jpg

It's my very simple and a bit crude front splitter. It's made from 1/8" ABS sheet. There is a vent in the front face of it that leads to a hose that runs back and pushes air into the bottom of the foot box to help keep my feet from getting cooked............ it works pretty well with a nice flow of air. dave

I just recently put new wheels on my Birkin............ it sure is nice having wheels that are actually round. Crazy I know. I'm running 215/45's in the rear and 195/50's up front and they fill the fenders pretty well. I got them from Good-Win Racing and they are Team Dynamics wheels meant for a Miata. They are 15 x 7 with a 30mm backspace. They are fairly light at 12 or so pounds and they are pretty cheap. The center bore to fit the Spec Miata is too small for the Birkin (needs 60.1mm front on my car) so Good-Win had them bored out for me for $10 a wheel and he did a nice job. So there are aren't too many 30mm BS wheels out there but there are a few. Dave http://www.usa7s.com/aspnetforum/upload/906589361_DSC_9996.jpg

I have the T1R on my Birkin for street use. They are very good even in heavy rain and the traction in the dry is fine. Not anything like a R compound tire or a slick by any means but fine for the street. They are pretty quiet and it seems like they will never wear out. I autocross on slicks and just wanted a smooth quiet tire that handled rain well for those long drives home after an event and the inevitable afternoon thunderstorm. Dave

That's good............ with all those guns out there we are bound to be safer and have less risk of gun related violence. or maybe not. dave

I'll see that and raise you one - Two years ago at a local event at our Ice Garden (skating rink with large parking area) everything was going just fine and I was working the course. I looked over and saw and old Chevy Nova slowly and calmly drive over the cones blocking off the lot and through the yellow caution tape breaking it and onto the course. The racer was flagged and came to a stop no where near the Nova. I walked over to the car and there was an older woman driving and she seemed absolutely clueless that she had driven over cones and through the ribbon to get where she was. I was speaking with her when she started rolling away from me. I yelled for her to stop (she was about to drive up a curb). When I finally was able to ask what she was trying to do she answered "park". Poor old woman was scared to death of me. Sad really. The best fun part of the scene were her license plates which read "SUPRNOVA". dave

More like this. dave

So I was in Helena MT yesterday for an event at the Fire Training Facility. I've posted photos of this place before........it's huge. Well the racing is going well but then a call comes over the radio to flag all cars to a stop NOW. Everyone comes to a stop and most of us have no idea what caused this. The the word comes through the radio that there was an antelope walking around on the course. I'll bet this doesn't happen in many places. We all got a huge laugh out of it. Once we got the antelope out of the way things got running again and I'm proud to say I ended up taking FTD. A good day. Dave

In my mind there are a number of things that could give you the effect you are seeing. I think it would be time well spent to go down the list and verify that everything is as it should be. This way you'll at least know all is well before changing tires and adding another variable. I seriously doubt your issue has anything to do with your current tires not be scrubbed in well enough. Unless they are still new and still have mold release on them you should be good to go. Toe Camber Ride height Rake Rear thrust angle Rear Toe Tire pressure Sidewall stiffness dave

FWIW stock Birkin wheels are 15 x 7 with a 30mm offset. dave

I set up mine with Brooklands screens. I bent a piece of 1" x 1/4" aluminum strap and then mounted the motorcycle mirrors and screens to it. Not as cool as a carbon thing but they work very well and my hat even stays on at 70mph! dave http://www.usa7s.com/aspnetforum/upload/601708953_DSC_6465.jpg

I have a few friends that have tried those tires on non-sevens for autocross and they were even less impressed than you were. Switching to Hoosiers will change your life and make you more of a man............... or at least get you around the cones quicker. dave

One issue you might find on a Birkin (maybe other sevens too) is that the rear track is already almost 3" wider than the front. If you add to this substantially I'll bet you add understeer in a big way as the rear grip will go up a good bit while the front will stay the same. I suppose you could consider doing the fronts too but this is project creep in a big way at the fenders would need to be modified...............not to mention the fact that your scrub radius would be huge and the stress on the front spindles might be scary. In the end it might be easier to put on narrower fenders dave

I autocross my Birkin a lot and it weighs about the same as your car. I'm running Hoosier slicks and I run 12.5 lbs. in front and 13.5 lbs. in the rear and it works very well. Dave

+1 Let's hope that sometime soon the folks that have risked their lives for our safety get the treatment, healthcare both physical and mental, and respect that they so richly deserve. They deserve all we can give them. dave

I paid $3.97 for 91 octane ( the highest we can get here) in Bozeman yesterday. Dave

I don't notice much in the way of power drop. If............ if there is any it's at the very high end of the RPM range and not a place I spend much time while driving on the street. With the Supertrapp thingie you can vary the amount of backpressure with the number of discs you use. At first I used all of them for the least amount of backpressure. I found it had a bit more bark that I liked so I removed a few and it took the edge off nicely. As I recall I'm running 9 of the 12 discs right now. My system replaces the stock, rear exit Birkin system and either way (with or without tip) it pulls MUCH harder with the new side exit system. I'm sure some of the power gain comes from the shortness of the system. I look forward to seeing how it does on the dyno. I dyno'd the car with the old exhaust and power started to drop off at about 5500 rpms. It felt that way too. It now feels like power builds all the way to cut off. It will be interesting to see if my seat of the pants deal is in line with the dyno. I hope that helps. dave

I use a DNA truck muffler (longest one) on my Birkin. For the street I have a Supertrapp tip that I slip over and clamp on. It keeps the sound to a reasonable level that I personally don't find too loud. Then when I race autocross I take the tip off and let it flow. It's turned out to be a very good way to go for me. dave

Eggsactly...........but remember that if your rear end carries less than 51% of the weight you get to pull off another 35 pounds. Dave

I don't believe that's true. I'd have to double check but I'm pretty sure it's the actual driver. When you are pulled into impound at a divisional or national event they have you (your helmet and all that) get in the car when it's weighed. If it was a flat amount for driver weight they'd just weigh the car and then add that flat amount and come up with a total.................. now as I think of this if the driver weight was "fixed" then you wouldn't have any mention of it in the book. It would just be car weight since driver weight wouldn't matter. Does that make sense? If you go to the SCCA site you can download the rule book and see what it says. dave