Davemk1

Narrower or softer tires will help a good bit. You can use blankets to keep the warmth in but if you can't generate any heat there is nothing to keep in. Narrow tires will heat a good bit faster and get warmer and will therefore generate more grip. This is of course for autocross only. Road racing is a different deal...............but for a 1 minute autocross a warm narrow tire will kick the snot out of a cold wide one. A few seasons ago I asked the tire tech guy at Hoosier what tires he'd recommend for my Birkin.........roughly 1450 pounds with the driver and 140hp. I was expecting to hear him say 10" all around or something like that but that wasn't the case. He recommended 7" in front and 8" in the rear. If I were to up the horsepower he'd suggest going up an inch in the rear and maybe in the front. I asked him why so many folks are running such wide tires on such a light car for such a short event. He says Hoosier recommends against that but that fashion and trends dictate stuffing the biggest possible tire you can under the car regardless of how well it works. In some cases, it does indeed seem that less can be more. I've cut and pasted an email he sent to the D-mod email list a while back. I took his advice and it works in a big way. He letter is just below - Subject: Hoosier Tires for Autocrossing a Seven Good talking with you this afternoon about tire fitment for your Caterham 7. Here are a few thoughts we talked about pre-Solo event and post-Solo event. First, the DOT A6 competition tire is designed for heavier type vehicles ranging from 1700 - 3000 pounds. Vehicles under this weight should benefit more from using our bias ply slicks which you currently use our item 43182R25A - 20.0 x 9.0 -13. Now, the new Topeka surface was quite confusing, where throughout the year at other autocross events, the bias ply slicks should have an advantage with more initial grip than the A6 which needs some force/weight to generate heat. The Topeka surface proved differently with many people running faster times on the DOT A6 tire. The specific surface(lots of sand) and cooler temps allowed this to happen. I believe it will take several years of Solo Nats to rough up or break in the surface to allow the bias ply slicks to grip better than the DOT A6's. On to your setup, if you find the 20x9-13 on a 10.0" wide rim is not providing sufficient grip, you should look at running a narrower rim and tire, using a 7.0 - 8.0" wide rim and using our item 43161R25A - 20.0 x 7.5 - 13 R25A on the front only with your 20 x 9 - 13 on the rear or the 20 x 7.5- 13 on all four corners. The narrower tire should develop heat quicker, but tire wear will increase somewhat, depending on driving style and surface type. This narrower tire combination could offer a second option to slick/sandy surfaces and cooler air temperatures while the wider tire option could be used for hot summer days. Having two tire size options may not be feasible for some because of transportation(carrying 8 rims and tires) or cost. The other option would be to run the item 46307A6 - P225/45ZR-13 A6 on the less than 1700 pound vehicle using the 9.0" - 10.0" wide rim which seemed to work for a few Solo prepared and modified competitors at Topeka. Finally, all of this information is a theory or my best suggestion working with tires for 15 years here at Hoosier Tire. I always stress that changes to your wheel/tire combination needs to be track tested before heading to the Solo Nats. Feel free to pass some of these thoughts on to your Caterham 7 group. Jeff Speer, HRT You might also consider spring and damping rates. It sure seems like the trend is to go very stiff.........but remember if you are sliding and there is very little body roll you might be too stiff. The original Seven, like most Lotus, was design by Chapman to have very low spring rates and high damping to control movement. These are for the most part very light cars and they like light spring rates for autocross. In road racing where transitio

It's a bit hard to take photos right now as it's a bit dark inside and it looks like snow outside. But I think you'll get the idea. The SuperTrapp thing came with a 2.5" O.D. flange which wouldn't fit over the 2.5" O.D. exhaust so I made a new flange for it so it just slips over. The flange has hacksaw slots to allow it to compress and grab the exhaust when clamped with a stainless hose clamp. The bracket is a bit harder to show. It's a 3/4" square steel tube. I attached it to the seat belt bolts that protrude from the bottom of the car using pieces of angle steel bolted to the 3/4" square tube. The 3/4" stuff runs across the bottom of the car so it picks up both seat belt bolts. The part that sticks out is pretty easy to see I think. There is a stainless exhaust clamp that bolts through holes drilled in the 3/4" tube. It seems to work very well with no funny vibrations or rattles and was very simple to make and pretty darn cheap too. Does that help?? Dave http://www.usa7s.com/aspnetforum/upload/111564468_DSC_7400.jpghttp://www.usa7s.com/aspnetforum/upload/1330146691_DSC_7401.jpghttp://www.usa7s.com/aspnetforum/upload/1809254526_DSC_7403.jpg

It is a DNA truck muffler. It's the longest and supposedly the quietest DNA offers. The sounds is good with a nice bark to it. Overall it's a bit loud for residential use so I made up a slip on SuperTrapp exhaust tip for it. It just slips over the end and secures with a clamp. Now I can drive out of my neighborhood at 6AM for an autocross and not feel like a criminal. I get to the event and undo the clamp and throw the tip- into my tool box. Seems to work out very well. The added tip seems to take the edge off but still flows very well. If you'd like I can post a picture of it. I wonder what the most effective length of the collector tubes would be? Mine are as Birkin supplied. It would be interesting to know. The is no O2 sensor. The car runs on Webers. Dave

So I made myself a new side exit exhaust system for my Birkin a few weeks ago. The stock system went from a 2.5" collector down to a 2" pipe that went all the way out the back. The exit out the back caused exhaust fumes to come back up into the cabin too often and the 2" pipe seemed to be choking the engine at high RPM's. So this new system is 2.5" all the way and much shorter exiting on the side. This has stopped the fumes issue and really opened up the top end of the RPM range. It used to fade when getting toward redline and not pull as hard and now it pulls with urgency all the way up. It's noticeably quicker now. And it sounds like a Seven should. This weekend the car finally gets it's lightweight aluminum flywheel and undersize crank pulley. Should be good for another boost of power and more smiles. Thanks for looking, Dave http://www.usa7s.com/aspnetforum/upload/1686905587_DSC_7337.jpg

How does one say"bad ass" in French? Dave

I bought my Birkin from Dick Brink in Texas. He was great to deal with and very honest. I see he has a Birkin for sale right now in the low 20's. Scroll down on the page to find it. Dave http://www.texasmotorworks7.com/racoca1.html

Cool. It totally makes sense when you think about it. There is going to be movement up there most any way you look at it. If the suspension is too stiff then something else will take up the load.....like the tires or chassis flex. In either case it's undamped movement with a very rapid rebound. So by softening up the suspension you are allowing it do do it's job so the other stuff can do the jobs they were intended to do. Cool. Dave

If I understand this right it started after you changed the uprights and some brake components. Is that right? If that is the case then we can rule out things like weight distribution and the like since it didn't do it before and you haven't appreciably changed that with your front end work. I assume you've got adjustable shocks and that they have a dial for adjustment. If that's the case then take it out to an empty lot and lock them up and make sure it happens with the current set up and then make a huge change to the damping and see what it does. You might not want to run the car full soft but try it and see if it goes away and you'll learn something. If you don't have the luxury or spinning a knob to make the adjustments things just got less convenient but it's still worth trying anyway. You'll also want to play with rear shock settings. Not enough rebound damping can cause too much weight shift and funny things to happen. You also need to verify your suspension settings. Make sure that your camber is set with your weight in the car. It changes a lot once you drop you butt in the seat. Check the caster too and make use both sides are close to the same and make sure there is enough caster overall. Too little caster can have negative effects under braking. Is your brake bias adjustable? If so you'll want to confirm that you haven't given the front end such good braking that the tires are overwhelmed. That's all I've got. Dave

Sounds like a geometry issue (caster?) or a damping issue. Dave

As you've read there is no clear answer. I'm a bit over 6'4" and weigh 180. I bought my Birkin never having sat in any Seven ever before. The first time I sat in it (after it came off the truck and too late to do anything about it) I thought to myself....."oh lord, what have I done?". I didn't really fit. But I made some changes and now it fits perfectly. I ditched the stock Birkin seat (sucked anyway) and put in an Ultrashield race seat. I modified the seat a bit to get it to drop down lower and go back just a shade more. Before putting the race seat in I took out the stock seat rails and now my butt is right on the floor and pretty comfy at that. After that was done I made myself a new taller roll bar. The stock Birkin bar is pretty short. I made the new bar a full 3.5" taller than the stock bar so it's over my helmet. And lastly, after that, I had a new top made to fit over the new tall bar. Now with the new top I can roll in comfort to the races or anywhere else I want to go with little regard for the weather. And I even fit in the car with the top up and my helmet on. I very nice thing I must say for those wet autocross events. What type of Seven are you considering? Dave http://www.usa7s.com/aspnetforum/upload/1346459251_DSC_3695.jpghttp://www.usa7s.com/aspnetforum/upload/1150602935_DSC_5646.jpg

On what have been one of the last warm and dry days of the fall I took some time and went for a cruise. I saw this fresh cut field a bit off the road and couldn't resist taking a few photos. One more race this season and then the engine comes out for a bit of work. Enjoy the Fall. Dave http://www.usa7s.com/aspnetforum/upload/54927240_DSC_7148.jpghttp://www.usa7s.com/aspnetforum/upload/751944381_DSC_7158.jpg

Glad to help a bit. You're right those guys with the big wheels are using something. If you have a choice find the lightest tire you can. Not only for the weight but for the flexibility. Most of those tires are meant to carry a car twice the weight of a Seven and can be too stiff in the sidewall. About camber and bias ply tires.........I agree in a big way. I'm running 1/4* camber and it works very well. Dave

If I'm not mistaken we are speaking about two different types of slicks here. DOT slicks (like thee Hoosier A6) and true road racing non-DOT slicks. If you need to drive to the event on the tires you are going to race on there is only one choice from where I stand and that's the Hoosier A6. If you are driving to the event on street tires and the race tires will be put on at the event then Hoosier road race slicks can not be beat. I've used Goodyear, Michelin and Hoosier and the Hoosier are in another class altogether. You can think of it this way........with each bump up in tire you are going to see about 2 seconds of difference on a one minute course. So with high performance street tires you might get a 60 seconds flat. Move to DOT R compounds and you'll be in the 58 second range. Move from there to Non-DOT race tires and you'll be able to get into the 56's. The big difference between an R compound DOT tire and a real race tire is weight and suppleness. A true race tire will weigh much, much less than any DOT tire. They don't have to pass the same (or any) tests to pass the DOT deal so they have a very thin carcass. This makes them light but also allows them to contour to the surface much better resulting in much higher traction. All that BS said................most true road race slicks don't come in a 17" size. Most are in the 13", 15" or 16" sizes only. If this is the case then you are getting road tires. I could be wrong on this. In the end it's much faster on real race tires. They are so good that you need to reset your "what's possible meter". Dave

I've got nothing to say about that :-) Dave

Hey Yellowman, Right you are. For all the times I've looked at that rule book I've never put that together. So yes I need to shed some weight (not as much as I thought) and this really drives home the need to add power. At 6'4" tall and 175 pounds I think I should look to taking weight off the car instead of off me. I'd look even dorkier at 6'4" and 135 pounds. Thanks for setting me straight. Dave

Hey Box-man, Yes the only place you can really run with a light weight Seven is in D-Mod. To be competitive one needs to get the weight down (1380lbs with driver for a 2.0L motor). My street car is 1460 with me in it. So I could take out 80 pounds but the only way to get much weight out is to remove the stuff that makes it streetable. So any weight I lose in the near future will be small and pull double duty (being engine rotating weight..........undersize crank pulley and aluminum flywheel are in the short term plan. I should be able to shed about 15 pounds of engine speed weight this way.) The other thing you need to do is have big HP. The Nationals winning DM car for years now has had 285hp and is completely unstreetable. So as you all know if you want to be competitive you aren't driving a street car. On the other hand I get great joy beating up on really expensive cars with really big numbers with my 140hp. At the said Divisional event the guy who won the SS class was driving a Porsche 911 GT3 RS. The driver is an EVO instructor and I got him by 1/4 second for a sweet victory in the emotional "street car class". This is that class that doesn't exist in the SCCA but that we street car guys cling to to make ourselves feel better when watching the race cars getting rolled into their trailers. On the 3rd gear deal. It seems to depend on who is setting the course and where you are running. Events in Helena always have me in 3rd doing a minimum of 70mph. Our Top Gun State Championship about a months ago had a 4th gear slalom that I was doing 85mph through. This was even with a number of SCCA regional safety guys there and no one blinked an eye. The place is just that big so the 65mph guideline seems to be ignored. I know it's against the rules but it happens and seems to be sanctioned. I'm proud to say that I pulled FTD both days of the event against over 100 cars and carts. That was my big goal for this year and I'm pumped that I pulled it off. Our local Bozeman events are 2nd gear 60ish at best as the lots are normal sized. Thanks for reading. Dave

Hey There, I had a very interesting time last weekend here in Montana at the SCCA NorPac Divisional event. It was run at the Helena Emergency facility (HUGE) and the courses were set as prep for the Nationals coming up in Topeka. We had a number of folks from the left coast stop by to attend on their way to Nationals. Normally at local events I'm the only driver in D-Mod and I often take FTD. Not so this time with the big guns being there. The biggest guns were Karen and Ron Babb who between the two of them hold many National titles. These folks are damn good and it shows. They are competing in D-Mod with a 60's Lotus Elan with a Ford BDA under the hood. I'm driving a Birkin with a stock Zetec putting out 140ish HP. Our first runs were pretty close in time but after they figured out where they could open it up their times dropped in a big way. After watching the Elan pull out of the corners like a rocket I asked how much power they had. I was told 230hp and nearly the same torque. Talk about bringing a knife to a gun fight. I drove as well as I could and felt I drove close to my potential and left little on the table but I was still about 2 seconds back on a 65 second course. It was really cool to watch them drive. It became obvious that they were making up large chunks of time every time they pulled away from slow corners. I could equal them in the twisty bits once up to speed but they would get up to speed so much quicker that I. At the end of the event I mounted my tire rack on the back and loaded up for the drive home and got the wildest looks from my D-Mod competitors. "You drive that on the street?"........"You drove that the 90 miles to the event?". Yes and yes. They wondered why I was 80 pounds over the minimum weight (headlights, heater, passenger seat....etc. all add up). It was fun to see their reaction to the fact that they were given a bit of a run by my summer daily driver. I've included a Google Earth shot of the place we race in Helena. It's next to the Airport and it's huge. We run there a bunch of times each summer and one can easliy set a 2 1/2 miute course there and run most of the time in 3rd gear. Good fun. One more event left for this season and then it's time to ski. I love skiing but I'll miss the driving. Dave http://www.usa7s.com/aspnetforum/upload/1045908112_helena airport.jpg

My Birkin has a heater that might be better referred to as a warmer. It makes warm air but you won't e driving in the cold in a T shirt that's for sure. I use a full top and side curtains in the cold and it works well. It's chilly here in the morning no matter what time of year it is. This morning it was 42* at 7:00 but will be in the low 80's this afternoon. Such it is with such low humidity. I don't end up driving it very often when it's seriously cold but this past weekend I drove it 1 1/2 hours to a race and it was in the low 30's. So I use the full weather gear fairly often when going out early to an autocross. This is what it looks like. This shot is taken on one of my favorite roads right where the road leaves the Bridger mountains and head across the Shields valley toward the Crazy Mountains in the distance. The road goes from very curvy and dead flat and straight.....which is of course the road you see. Dave http://www.usa7s.com/aspnetforum/upload/806709342_DSC_3839.jpg

We have the room for you. The state's population is less than 900,000 in total and the distance form the eastern boarder to the western boarder is the same as from Washington DC to Chicago..............in other words it's huge and empty. If the event was centered in the South West part of the state you could see both Yellowstone and Glacier national parks. Yellowstone is about 1 1/2 hours south from Bozeman and Glacier about 5 hours north. There are wonderful places to stay and lot's a first class driving with the only other thing on the road being cows or elk. I'm an active member of our SCCA club and I'm sure we could arrange for an autocross event to be held during the time of the event. We've got a few national class drivers in the area and the events are fun and fast. If folks would like info on roads or places to stay I'd be more than happy to supply whatever you all want/need. I don't want to be too pushy so if the group is interested let me know and I'll do some leg work and present you all with some info. One closing thought................a group of Sevens going over Beartooth pass early in the AM would be over the top fun. Dave

My Dad sent me this link. I don't know anything else about is but I can tell you it was some barn find deal in Europe. A good number of Lotus in there. Unbelievable. Dave http://WWW.intuh.net/barnfinds/afa70.htm Edit - I just got the below from my Dad in another email that explains it a bit more. Sounds a bit urban legend like but who knows. Cool cars any way you slice it. A man retired. He wanted to use his retirement money wisely, so it would last, and decided to buy a home and a few acres in Portugal. The modest farmhouse had been vacant for 15 year.; the owner and wife both had died, and there were no heirs. The house was sold to pay taxes. There had been several lookers, but the large barn had steel doors, and they had been welded shut. Nobody wanted to go to the extra expense to see what was in the barn, and it wasn't complimentary to the property anyway......so, nobody made an offer on the place. The New York guy bought it at just over half of the property's worth, moved in, and set about to tear in to the barn.......curiosity was killing him. So, he and his wife bought a generator, and a couple of grinders.......and cut thru the welds. What was in the barn...............? Go to; WWW.intuh.net/barnfinds/afa70.htm http://WWW.intuh.net/barnfinds/afa70.htm> and start wishing you had bought the place. When the picture comes up, click next to see all the cool stuff he unknowingly purchased. [And, unfortunately the author of this piece doesn't know American cars at all, nor is he/she interested. One of the most valuable finds is the 1931/2 Chrysler Imperial convertible coupe (a Custom Imperial? - or a LeBaron???).]

I believe that would be Hazel. Dave

Nice R/T ! Dave

Amen to that. The Beartooth highway needs to be seen to be believed. I've been over it a number of times and the beauty is hard to describe. There are some other wonderful driving roads in this area and I feel it would be a wonderful place to hold a get together. I can give details of some of the drives if folks are interested. I'm also very active in our local SCCA club (region 52 which for the third year running is the fastest growing SCCA region in the country BTW) and I'm sure we could arrange it for our club to organize an autocross event for that weekend. Food for thought. Dave Bozeman MT

My car is the fastest car on the planet.....bar none. End of discussion. Dave

A Seven is like porn........I'm not sure I can fully define it but I know it when I see it. The Atom is stunning in it's own way but it's not a Seven. Dave