Davemk1

I've had a few over the past few years. I'm down to a single toy car now with my Birkin. I previously owned and restored this 1966 Lotus Cortina. A wonderful car and a cool slice of history. While owning this I got into autocross and didn't want to risk damaging the Cortina so I bought this 1976 Mazda RX3. It was in a farmers field sunk up to the hubs in the dirt with something wrong with the clutch. It turned out that it was a small spring that holds the clutch fork to the throw out bearing had come unclipped. Stuck it back on and it was good to go. Fully stripped it was pretty darn light and quick. I sold it to a local friend who is still racing it and doing well. Both of these are gone now and I miss them. Dave http://www.usa7s.com/aspnetforum/upload/2028647937__2039.jpghttp://www.usa7s.com/aspnetforum/upload/1696887103_Camera_1962.jpg

I'm not the end all be all of info on this subject but I do have a reasonable amount of experience in autocross. Tire width can be a funny thing. Keeping in mind that the runs are short (about 1 minute in most cases) you'll realize that getting heat into the tires can be a real issue. You are in effect running on cold tires most all of the time. Here in Montana we run plenty of events where the morning temps are in the 50's. I feel tire width choices need to be made considering your temperatures and your horsepower. I'm running a Birkin with about 140hp and 13x7 wheels in front and 13x8 wheels in back. I'm also using Hoosiers (25A compound) in a 7" width in front and a 8" width in the rear. This is a bit narrow compared to national class cars which run 10" in many cases. The narrow tire allows for a much quicker heat build up and in the end better grip than I'd have with a wider tire. If I lived in Texas the choice would be different. So a narrow but warm tire will outgrip and wide cold one every time. I also feel that the choice to run staggered sizes or not depends on your driving style and the cars power and balance. As basic as it sounds, if the car is loose or tail happy then wider rubber in the rear would help..........if it pushes then having the same size all round would benefit. If you have plenty of power then wider rears might make sense. At over 200hp I'd put you in this camp. I drive pretty aggressively and tend to steer a good bit with my right foot and the slightly wider rear tire keeps me from spinning and wiping out cones with the back end of the car. FWIW I've used a few different tire brands over the years and have come to realize why about 90% of the winners at Nationals are all running Hoosier 25A's. They are simply the best for autocross. They stick hard and have a very progressive breakaway which you can use to your advantage. I love them and will never run without them again. So......if I owned your car I'd lean toward running wider rears. I hope that helps and doesn't confuse the matter more. I've attached a photo of my car cornering hard on the Hoosiers. This event was last weekend and I took second fastest time of the day about .3 seconds behind a 125cc shifter cart. Hoosiers rock. Dave http://www.usa7s.com/aspnetforum/upload/161956215_DSC_6475.jpg

I feel a bit like a dummy but here goes - I completely understand the foam around the tunnel deal and that is something I plan to do myself. My question is what does the foam around the radiator do to keep your feet cool? Thanks for sharing your results. Dave

Engineer and first head of the SAE William Stout said (in the 30's as I recall) "Simplicate and add more lightness". He designed a mininvan in the 30's that had suspension geometry that made the vehicle lean toward the inside during corners and demonstrated it's effectiveness by cornering hard with a glass of water on the dash. We was more than a bit ahead of his time. Dave

I've been pulled over only once. I knew I wasn't speeding so I was ready to argue. Turned out the cop just thought the car was cool and wanted to tell me so. Here in the 3rd world country of Montana if it rolls and has brake lights it's legal so I don't get much trouble from the MAN. Dave

I hadn't thought f that. That makes good sense. Dave

That's a strange one isn't it. I remember seeing that car on eBay and then it was gone. Seller ended auction early and sold it to WW. Strange as I'm sure they would have gotten MUCH more if they let the auction run it's course. Is it true that WW got it for 12K. I wonder how they did that? Dave

I bought my Birkin from Dick Brink and would do so again. FWIW there are a few things about later cars that might be better. My car, a 1999, has the transmission tunnel riveted to the chassis and would be a total PITA to remove. Later cars have lot's of little bolts. I wanted to remove my tunnel to put in driveshaft safety hoops. I still will do it someday when I feel like drilling out nearly 50 rivets. I hear that later cars also have a wider footwell than mine has. I wear a size 11 and there is no extra room in there. I can only drive it in driving shoes or barefoot. Not a big deal for me but if you have big feet it might be. I like my Birkin very much and think it's well made. I'll bet you'd enjoy one. Dave

That is a truly stunning vehicle. Makes me wish I did something for a living that really paid well. But I love my job nonetheless. But that car can make one second guess everything. Dave

Do you want a photo of the rack mounted on the car sans tires? If so I don't have one but the rack goes on this weekend for a race and I could take one. Let me know. Dave

Hi Mike, I bought my car used from Texas Motor Work (Dick Brink) and he treated me well and fairly. I'd do it again. My car has what I believe to be a stock Zetec and it dynos at about 145hp. That is more than enough power to have lots of fun with. Would I like more? Yes. Do I need more? No,not at all. I had one issue with my car. For some reason whoever converted the Zetec removed the windage tray. God knows why but it wasn't there. I found out because every time the car was spun up toward redline it would puke oil out the breather into the catch can. I tried everything to fix it to no avail. I finally dropped the sump and found out the windage tray just wasn't there. $25 later it had a tray and no works perfectly. I don't know who did the original work but I do know it wasn't Dick Brink. I've seen both cars in question on the website and it money was no object I'd buy the green one. I think it's worth the $31K. But both cars look good. I feel the Birkin is a well thought out car and I enjoy it very much. I put about 6k miles on mine last summer and loved every mile. let me know if you have other questions. Dave

I do a lot of autocrossing in my car and here is how I get the slicks on 13" wheels to the event. The jack sit on the passenger side floor and I'm good to go. The rack uses the 3 pick-up points normally used by the spare tire carrier. Fun with tubing. Davehttp://www.usa7s.com/aspnetforum/upload/1569071217_DSC_3695.jpg

So I run a Birkin and it has the stock rear exit exhaust. I'd like to replace it from the collector on back and set it up as a side exit system. The stock system is heavy, has lots of back pressure, and causes fumes to come into the cockpit when using the side curtains. I'm told that a side exit system will help a good bit with the fumes and it most certainly will be lighter. So..........I'm wondering if anyone has a recommendation as to what muffler to use. I'm looking for something that is reasonably quiet so that I don't feel like a criminal driving out of my neighborhood at 6AM on an autocross morning or through town. I was told by one Seven owner that a DNA muffler from Summit racing would be good and then told by another that the DNA was really loud. So who knows. I realize that it's hard to gauge how loud a system is but I'm guessing you all understand what I'm looking for. Any thoughts on mufflers? Thanks, Dave

Cool, I think the most important thing is that the car be safe to you and others. If that's taken care of then the next most important thing is that you are having fun driving it. It sure sounds like you've got that nailed. Enjoy the ride! Dave

Hey Andrew, I hope your lack of ignorance is better than bliss. But I hear you. Are your rear control are adjustable so you can set the trust angle? Dave

Hi Andrew, I'll try to answer your question. I try to determine if the tires are working properly with a temp sensor. It reads in whole degrees F. In the perfect world the tire would have an even temp across the tread surface after a given autocross run. This of course shows how the tire is being "worked" and where the pressure and stresses are. I then make camber adjustments (based on tire temps across the width of the tread) and measure those with a digital protractor which reads in 1/10 degree of angle. The tire temp deal is also VERY good for getting the air pressure right. Too high and the middle of the thread is hotter than the outside. Too low and the outside edges will read hotter than the middle. I run Goodyear slicks front and rear.........7" front and 8" rear. I've got it so the tire temps in back are good to within 1*F across the width of the tread. In front I still run a bit hotter on the inside edge. As I recall it's about 5*F hotter inside than outside. I'd like to experiment with even less camber to try to even that out. I was running up to 1.5* camber up front and was getting a 15 degree F ( or more depending on how turny the course was) difference from outside to inside (inside being way hot). This was showing how little work the outside of the tire was doing. I in effect was using 4" wide tires up front. Not good. Dinner time. Dave

This is very interesting. There seems to be a wide range of spec's out there. I run a Birkin and the camber and toe are adjustable but the caster is for the most part fixed. There are a few small washers that can be moved around to adjust caster but they have a very limited range. For some reason the Birkins have HUGE amounts of caster. This is a mixed blessing. My car is very stable at speed and handles very nicely BUT with all that caster, once the steering is turned some the camber goes through the roof. For instance when the wheels are turned to the side only 10 degrees I gain 1.2* of camber. At 20* of steering angle I have 3.5* of camber! Here is how my car is set up - Camber -.3 degrees Caster 9 degrees Toe 1/16" toe OUT These are set with drivers weight in the seat............your numbers will change by a good bit when you put your butt in the seat. You can see I run very little camber but I have no trouble at all with the tire rolling over during hard cornering. In fact if I take tire temperatures right after an autocross run I'm still a bit warmer on the inside edge. I also run slight toe out for quicker turn in. It's still one finger on the wheel stable at 80 mph. One of the benefits of all that caster and so little camber is a full contact patch under straight line braking and initial turn in. I'm not the expert on this but there are a few things I've learned. To optimize camber a tire temp gauge is a very good thing. I have an infrared temp gun that cost about $40. If, in your intended use of the car (autocross and road use for me), you get even tire temps across the full width of the front tires you're doing pretty well. The other thing I learned is how much your body weight being in the seat change things. In my car I gain .3 degrees of camber on the passenger side and lose .1 degree on the drivers side once my butt goes in the saddle. I use bags of wood pellet fuel to simulate my body weight so I can load it up and then make adjustments. The last thing I learned realized is that you can run less camber when you have higher caster. Maybe this is common knowledge but it was new to me. Fun stuff. Dave So I must apologize...........I just now noticed this post was in the Bike engined department. My Birkin is doe not ahve a bike engine. I just got excited about the geometry stuff.

I've only owned my Birkin for about a year and a half but I can't imagine being without a Seven. I've owned some fun cars in the past, A Volvo 1800ES, a 1966 Lotus Cortina, and a 1976 Mazda RX3, and these were all fun but everything feels like a truck compared to a Seven. I can imagine a different Seven but going back to a "real" car seems unlikely. Time will tell. Dave

Everything's bigger in Montana. Dave

I know what you are talking about on the "Birkin Bend". There is a spot right in front of the seat where the chassis has a sharp corner and when the aluminum sheet is pulled over it it leaves a spot that kind of sticks out to the eye. When the light is right, like in my second photo it is easy to see. At other times you can't see it at all. I autocrossed this past weekend in Helena MT and man that was fun. Almost a 1 1/2 minute lap with about 80% of that with my foot to the floor in 3rd. Good fun. Hey....thanks for reading. Dave

Hi Tom, Yes I do know Russ. He and I autocrossed together yesterday and and a great time. He's a skilled driver and owns some very cool cars. Later, Dave

Hello Folks, My name is Dave and I drive a Seven. I live in Bozeman MT and after posting a few shots of my car in the owners gallery section I was told I should say hello officially and introduce myself. Like I said I live in Bozeman and I run my own very small business of building custom, made to measure bicycle frames. I've been a frame builder and a cyclist for a very long time now and as much as I love it my passion outside of work is cars and driving. I live here with my lovely wife Karin who is a geologist and a full time ski instructor. No kids, lots of cats. When I was a kid my Dad was a race car mechanic and I was always be dragged around to different races. I guess it gets into your blood as they say. He passed away when I was young but his love of machines and making them better stuck with me. I've owned and autocrossed a few cars over that last 6 or 8 years. I started with a Lotus Cortina. A wonderful car that was too original and clean to go flogging on the weekends. I then found a very solid 1976 Mazda RX 3 that made for a kick arse race car. Simple design and easy to modify. Lots of fun to drive. It go me thinking about a truly light weight car like a Seven. I sold both the LoCort and the RX 3 and started shopping for a Seven. I found a 1999 Birkin S3 and had it shipped to me here in MT. I've owned the Birkin for just over a year now and I've got it running and racing well with many FTD's late last season. My first real race of this season is this coming Sunday and I'm very much looking forward to mounting up the slicks and letting it rip. The weather doesn't even call for snow! Well thanks for reading and I look forward to spending some time with you all here and better yet on the road. Dave

Hey Tom, Len is a good customer and his bike was fun to build. Thanks for your kind words. Sorry about the tease photos Come out for a visit and we'll go for a blat in the hills! Dave

Hello Folks, My name is Dave and I'm a Birkin owner from Bozeman MT. I autocross the car a good bit and I'm lucky to be able to drive some of the most fun, completely empty road one can imagine. I've really enjoyed looking at your wonderful Sevens and thought I'd share a few shots of mine. All the best, Dave http://www.usa7s.com/aspnetforum/upload/1522655336_DSC_3839.jpghttp://www.usa7s.com/aspnetforum/upload/1178867918_DSC_4183.jpghttp://www.usa7s.com/aspnetforum/upload/1919874711_IMG_0026.jpg