Lotus Europa Community
Lotus Europa Forums => The Paddock => Topic started by: rjbaren on Friday,September 17, 2021, 04:16:49 AM
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Hello, I am signed up for my first parking lot type auto cross next weekend with the local BMW club. I have a 73 Twin Cam Special. My tires are stock size Barum and my suspension is stock except for Spax adjustable shocks and the stock front springs were changed because they were too tall. I think a pair of 110 lb. springs were installed but I am not sure the poundage.
Any tips on shock settings and tire pressures? Any tips in general? I have only auto crossed once about 30 years ago in a stock Sunbeam Alpine.
Thanks
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It has been a long time since I autocrossed my stock suspension Europa Special. What I remember was that I needed to reduce the rear tire air pressures to help get the car to rotate. In the sharp corners of the parking lot events, there was just to much understeer.
Just have fun!
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Awesome that you are doing it again. I autocross too. Start of our season is Sunday. My car is a little tail heavier than most Europas due to a different engine but I run 18 psi front and 24 psi rear. If you don't have a pyrometer, you can get some chalk and chalk about an inch long and 1/2" wide of the edge where the tread and sidewall meet and you will know if you are too low and rolling it over. Lower is better until it's too low. If you have some tall, regular all seasons maybe a few more psi but don't follow what 3000lb + car guys run. I run my shocks the same on the street as autocross. Just enough rebound without being uncomfortable. I don't change anything. Show up, run, and drive home. If you stiffened up the front springs only and not the rear it should understeer a little more. Easier to drive than loose but if it's excessive understeer, you can run the rear shock stiffer, if they increase bump and rebound and try to reduce the push. Only change one thing at a time.
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Hi and thanks Clifton. I have all season tires I think they are currently set at 16lbs. front and 26 lbs. rear pressure. Also I checked the shock adjustment and they are set all the way counter clockwise which I believe is the least stiff. So would those pressures and basically no adjustment be a good place to start?
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I would run more front pressure and a little less rear. I run "street" autocross tires and have a pretty stiff sidewall plus I run stiffer springs, 250 lb front and a large bar. My 18/24 would probably too little for you with stock camber. I think 16 psi in the front with all seasons will roll over more than you want for autocross. Maybe 22 front 24 rear cold. I would bring a pressure gauge and if you aren't close to the edge on the first run, I would lower 2 psi then 2 psi on the next run. It's easier to lower then add in between runs. Your pressure will come up too after you get heat in them so don't go by the same numbers when hot. My 18/24 is cold. I would just make sure the fronts are being used equally the same as the rear, both at the same point on the edge, whatever that ends up at. If you know they are being used equally the same and you find the limit of slip at one end, you can go from there rather than wonder if it's pressure or spring or both.
You don't have to chalk but it is easy to see and cheap.
First pic is chalk half wiped off so you can kind of see what it looks like before and after. It is a cleaner line after a run.
Second pic is how much roll over I have.
Third pic is wifes car, street use only. If hers looked like this pic after a run I would lower it 2 psi per run until it rolled over to match the second pic of mine.
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Ok, I'm a bit out of my depth, since it's been an age since I last autocrossed and I knew even less than I do now about shocks and springs but here are my thoughts (I welcome comments from those more knowledgeable):
Because you seem unsure about exactly what springs you have: How does your car handle now? Does handling on the highway seem vague or unstable? Do you have to intently watch steering inputs on the highway for fear of ending up in the next lane or even a ditch? That's likely a sign that your shocks are not stiff enough for your springs.
Is your ride rough or even bouncy where the car seems to follow every undulation of the road and absorbs none of them not enough of them? Then your shocks are likely too stiff for your springs.
Considering that you mentioned you might have 110# springs (probably on the rear since the stock front spring rate is 116#) and your shocks are set full soft, I'm guessing that you probably have your shocks, at the rear in that case, set too soft.
Assuming that your shocks are in a comfortable setting where steering and handling is precise in fast turns and the car is stable on the highway, you might turn your shocks up two clicks for your autocross. If that works well, you could experiment with a couple of more clicks.
Shocks can affect the balance, too. since they affect the roll resistance. Increasing the roll resistance in the front will give tend to give you more understeer and more roll resistance in the rear will tend to give you more oversteer. Tire pressures also affect roll resistance. I've attached some information about that.
If you plan on doing more autocrossing, it would be good to know what springs you have. Quite often springs are marked with their rate. Sometimes with paint, or engraving on the end of the spring (the flat part). Sometimes there is a band that is heat shrunk on the coils with the rate. Who knows how it might be noted on the spring (or not). Look all over the spring for some identifying marks and if you can't find any, you can use a bathroom scale, some 2x4s, threaded rod and a ruler to determine the number of pounds force is required to compress the spring one inch. It's linear so you don't have to start at 0 and go to 1 inch, you could start at 3/4" and go to 1 3/4 inch for example. Knowing how your spring rates compare with the stock rates would be helpful.
Because I only know a little about this (and because I already have more springs than I need), I would try to stay close to the same multiple for spring stiffness. For example, you mentioned you might have 110# springs. If those were on the rear, they are 46% stiffer than the stock 75# springs. I would want a similar increase in stiffness in the front springs to maintain the balance that Lotus designed into the car. Of course, if you are an experienced performance driver you might have a different idea of how you want your car to behave and thus might want a relatively stiffer rear spring for more oversteer or a relatively stiffer front for more understeer, but I think most of us "amateurs" just want what Lotus designed or maybe "a bit more" of what Lotus designed.
A lot of this is personal taste. I've made my suggestions based on my experience with new shocks and not actual racing or autocrossing experience. I'm still experimenting and I readily admit that I am walking in the dark to some degree. I hope if someone more knowledgeable thinks I've steered you in the wrong direction, he will set me straight.
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I checked my pressures this morning and the fronts are at 14psi and the rears are at 24 psi. I also added 8 clicks to the firmer side on the rear shocks. I read if you adjust all four shocks equally than you haven't really made a change. So I will leave the fronts alone and then maybe even drop back on the rear.
The car felt fine in a straight line. Then I made a couple of quicker turns and the tires were squealing quite a bit. I am thinking of adding more air to the fronts, like 2 lbs., and trying it again.
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Tires squealing just means they’re working hard. Two more pounds in the front might be good. Use Clifton’s trick about the chalk (when I was autocrossing an age ago, we used white shoe polish - can you still get that?) to see if your tires are rolling over to help decide if you need more or less air in your tires.
I think what you read about adjusting all your shocks the same amount is about the balance. If you have too much or too little damping, it will make a difference.
I seem to remember that the SPAX folks told me that the adjustments are not linear - i.e. the difference between click one and click two is less than the difference between click two and three. I also seem to remember they suggested increments of two clicks.
Just some thoughts…
Have you run your autocross? Let us know how it went!
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Autocross is the 26th, unless its rains. Then I will take my BMW wagon instead. I don't think the Europa is water tight. I bought some chalk and I want to find a cheap 12 volt compressor with cables to connect at the battery because the car doesn't have a cigarette lighter.
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Bike pumps work good. I cut the end off a female cig plug and stick the wires in a 18v Makita battery for portability. Pumps fast with more volts.
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They make electric bicycle tire pumps? Sounds interesting.
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For example: https://www.harborfreight.com/12v-150-psi-portable-inflator-63152.html
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They make electric bicycle tire pumps? Sounds interesting.
Idk but I meant hand pump bicycle pumps.
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I found a very small 12 volt compressor by Slime. I bought the cheapest one for $17.99. I spliced in the necessary wires to be able to connect to a 12 volt Bosch drill battery and I left the cigarette light plug for other cars if necessary. It is supposed to inflate a tire from flat in 12 minutes. It seems a bit slow but it works and it should be fine for the autocross.
What a great idea to connect to a portable drill type battery. Thank you very much.
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Well, I got the results and I came in 68th of 70 cars. I ran with the Windy City chapter of the BMWCCA. The winning car was 2005 Subaru Sti. There were 6 Porsches and a slew of BMWs. It was fun that's for sure. The only mechanical problem I had I noticed at the end. My ignition light came on and the battery wire to the alternator came uncrimped. Overall I am happy with the result, I drove there, ran the course 11 times and drove home.
Clifton, your car looks incredible in your photo. Is there a post where you have more photos and a description of what you have done with the car?
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Congratulations on your first autocross! Having fun is the main thing! :beerchug:
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Clifton, your car looks incredible in your photo. Is there a post where you have more photos and a description of what you have done with the car?
It's great you had fun. 11 runs is a lot. We get 5. How was the handling? understeer or oversteer? Are you doing another?
This thread has most of the mods I've done on it.
http://www.lotuseuropa.org/LotusForum/index.php?topic=1035.0
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How many cones?
Any spins, stalls, or missed shifts?
Has to be a reason for #68. ;)
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The main reason is I guess I am not a very fast driver. I have only auto crossed once before in like 1990s in a Sunbeam Alpine. So it was my first auto cross in 30 years and my first time driving the Lotus off road so to speak.
There were 18 BMW M 2s, M3s and M4s. 18 BMW non M cars, 6 Porsches, a 2021 Toyota Supra, 7 Miatas, 2 Nissan 350Zs, 2 Subaru WRXs, an Audi S4, 2 Honda Civics that finished 8th and 13th, 2 mini Coopers, a Lexus IS 300, 3 Volkswagen GTIs, etc. It seemed like pretty stiff competition. I felt like a fish out of water just trying to figure out what's going on. The only car I beat was a 1987 Saab 900 turbo.
I know my car was sliding but I am not sure which end of the car was unattached. I was kind of waiting for the tires to reconnect before pressing on the gas again. I laid too much rubber at the start, but it was fun and felt like I was going fast but I really wasn't.
There were 9 seconds between the 1st and last place cars. But that is a lot of time on such a short track. The fastest car was 34.164 seconds and my best time was 43.181 seconds. my first attempt was 53 seconds so there was some improvement.
My performance upgrades are: 146 HP engine, Mikuni carbs, a header and performance muffler, lightweight alternator pulley, adjustable lower rear links (one stock one was bent), Spax adjustable shocks, 110 pound front springs (the stock springs were way too tall) and electronic ignition. All new rubber bushings, 5 1/2 wheels and stock sized Barum Brillantis tires.
There is one more auto cross but it is pretty far away and I don't want to drive that far to beat on my car and hope to bring it home in one piece. In the future I may buy a trailer to haul the car to farther out events. I would like to try Midwest Council auto crosses which are done on actual race tracks. This was my first attempt and I liked it, but I need to get a better set up to transport the car and a place to park the trailer.
I would like to buy a different set of tires over the winter. I have a set of Lotus alloy wheels but maybe it would be beneficial to buy larger rims and tires. I need to do some research. I want to keep the car pretty much stock in case I ever want to sell it and it serves as an excuse to finish at the back of the pack.
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Sounds like you had a great time, congratulations!
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Picking up almost 10 seconds is huge. You will get better and faster the more you get used to the sea of cones, everyone does. The cars that are faster than you have much better (softer) tires though. FWIW, soft tires last a lot longer on light cars. I'm 2600 miles in on some Rival-S 200tw and they have plenty left. They will be too old before too worn. A few guys on here run R888R's and there's the AR-1 too. Tires make a huge difference.
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Did my last Auto-X many years ago in a hot-rod '65 Corvair.
Not planned, just happened to drive by and decided to make a run.
Power slid the rear around almost every corner to prevent plowing the front from understeer.
Never touched a cone but was DQ for my 'slightly' loud header exhaust.
My time was actually pretty good, the course workers other comment was, "Did you used to drive British cars"? LOL!
I had about fifteen British and Italian cars at home.
Sounds like you have plenty of power, make more runs!
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Clifton your car looks absolutely incredible, and the work you have done is beyond belief. It must be so rewarding and fun to drive. I think you have a masterpiece. There are so many talented guys here building really cool cars. It's amazing.
Thanks for the votes of confidence. I will do it again next year. It's just starting to get cold here so not much season left.
So, for a tire and wheel package question. Since I have a set of 13x5.5 Lotus alloys that have been blasted and are clean I can put on a set of tires 205 60 13 rear and 185 60 13 fronts. I have seen Hoosier and Toyo available in these sizes. Is there an advantage to going with 14" or 15" wheels? Is the advantage in tire availability and/or is it better to have larger diameter wheels too.? If so, what are the recommended combinations that will fit without having flares or rubbing?
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Thanks, it's my final car and I put everything I've learned from other builds into this one.
Hoosier are A7's are the fastest, R7, second but heat cycle out usually before they are worn out. Driving them on the street will kill them quick. I wouldn't jump straight to these. 15's would give more options on brands and you could run one of the fast autocross 200 tread wear tires but I would just stick with your 13's and run R888R's (100tw). In SCCA it will put you in a non street tire class but you'll be much faster and probably be running by yourself anyway. I don't know if I would run a 205 on a 5.5" wheel. You are stiffer in the front than stock so equal sizes wouldn't be bad. I run 15's because I was building a car that needed big brakes and a wide tire in the rear. It's not just the flares though with 15's, I had to deepen the body by the footwell to clear when turned, this is for a 205 front in 15". If I kept the 4 cylinder, I would have run 13's and no flare. I wouldn't trailer either. It gets old and takes all the fun out of it. I don't even bring tools when I go now. Just check pressure, get gas and go. It's much more fun driving it there and everywhere else. Funny your season is ending due to cold when ours just starts because it finally got cold(Arizona).
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I looked up the Toyo R888Rs and 5 1/2 is the narrowest rim allowed for the 205 60 13s. I called Tire Rack to confirm and Isaac agreed, the 205 is OK to use with a 5 1/2 inch wide wheel.
My figures show the stock rear tires will have a height of 589.2 mms and the 205 60 13 Toyos will have a height of 576.2 mms. The stock front tires have a height of 575.2 mms and the 185 60 13 Toyos will be 552.2 mms. The 13 millimeter difference in the rear may mess with the speedometer by about 2%, I think? I don't believe the front will have an effect on the speedometer but I am not sure of that either.
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According to this site, less than 1%:
https://tiresize.com/tyre-size-calculator/
You will have a full 1" wider on either side though.
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I would just use my phone to verify speed at 60 and from then on, know I'm off XX at 60, half that at 30 mph. You may be off now and not know.
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That's a very nice tire calculator. Tire rack says the Proxes R888Rs aren't expected back in stock till next spring.
I have a set of OEM alloys that have been blasted and are ready for finishing. I am thinking of rubbing some SharkHide
on them because it's easy and it won't yellow or peel. When necessary just rub on another coat.
Other wise I think I will have to mask and polish parts of the wheel, not to mention painting.
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I don't know if you tried Phils tire. They only carry competition tires. Same prices as Tire rack. They carry Nangkang too
https://philstireservice.com/product-category/competition-tires/toyo-tires/
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I am currently running stock sized touring tires so that shouldn't be a contributor to speedometer error. But, regarding the speedometer, I can hear my speedo cable, because it's pretty loud. Could it be that it is not spinning to the proper speed due to too high friction and causing an error? I think JB has replaced his speedo cable with a GPS type system.
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I suppose the way a cable would cause inaccurate readout would be is if it were broken and the driven end turned the other end slowly. That seems implausible to me though. Keeping the cable lubricated is important and often overlooked when bringing a car back to life after sitting for many years. I can’t remember what the appropriate lube is but I’d think it would be a mixture of gear oil and grease.
JB (and I) have electronic speedos. They are driven by “counters” that count revolutions. There are three types of counters that I know about. One (what I think JB has) that counts revolutions of the speedo gear in the tranny, another that counts revolutions of a spinning part of the car like a hub (IIRC, Clifton has this type), and a GPS antenna that translates distance into counts for the speedo. My speedo gear was eaten by my tranny so I chose the last type. Of course, it is useless in tunnels and dense tree cover. It also takes a couple of minutes to acquire satellites.
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+1 Your speed cable is "talking" to you. Lube it now, before it's too late.
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Do you guys just use spray lube, or do you use the lube devices with the spray that I see for sale on the motorcycle websites?
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Pull the inner out and coat it with light grease.
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I can almost unscrew the cable end behind the speedometer and after a while I'll probably get it. Would it be best to undue the cable from both the speedo and the transmission and then pull the inner cable from the transmission end?
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It only goes one way, usually just from thew speedo head end.