He, Fred Puhn, and Paul Van Valkenburg: I still have all those books.
Truly must-haves!
Huh? You mean camber? Castor is set with the threaded upper spindle (although mine are eccentric and alter both parameters)
Clive,
Stock castor settings I believe are 2.5 degrees, and are readily adjustable via the threaded upper fulcrum shaft. I run mine at 4 degrees and prefer the resultant steering feel.
Hi Pete - no I mean castor. Many (most?) US cars set castor this way. The effect of differential shims back and front is to rotate the top ball joint forward or backward. Iām not suggesting anyone use this method but Clive was wondering about alternative means that would work.
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Yes, Iām just looking at ways to change areas that I or others with more XKE experience think interesting. Sadly I have no practical experience with this car although I spent my working life doing similar work on others. My comments are purely theoretical, I canāt vouch for their practicality because I donāt have a car in front of me. (The project car Iām working is more than 4,000 miles away). I donāt have enough detailed data to monitor such areas as clearances, ball joint angles etc., so implementation is the responsibility of the implementor. Itās very possible that nothing I suggest has any immediate value but I enjoy the discussion. (That pig and mud saying comes to mind). Thanks for your indulgence.
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Wrestling with a pig. Thatās the metaphor I was looking for.
Would anyone care to make tyre recommendations? Weāre not looking to go as extreme as some of the other areas of the car, initially thinking of 15 inch, 205 and / or 225 section, focussed more on high performance road use than track at this stage. Expecting to be somewhat lower than original, but not hugely so.
Any thoughts appreciated.
The best are Avon CR6ZZ - they come in 15" with various widths: They are amazing - a race tire for use on the road. Iāve driven on them and raced against them. Expensive but not compared to what you guys are spending.
Thanks Terry, what size did you use? Weāll probably start with a strong road tyre on 15 inch wheels, then move in a track direction after weāve done some sorting and fixed the inevitable problems. Looking to go slightly lower radius than original on the first tyres, such as 205/55-15. Does anyone know if 225/50-15 will have any clearance problems on the front? (Weāve done some slight easing on the rear body to give clearance for 225 or 235 back there).
Spending? Iām just a simple engineer, I know nothing of such matters although I am trying to find some justification to buy a damper dyno. Iām just not sure there are enough hot Honda Civics on the island to help fund it. The Quantum dampers should arrive next week, looking forward to splashing some oil around the bench. And the floor. Maybe the walls if I get too confident.
Iāve never owned a set, but Iāve got friends that I autocross with who have. They will give you 2.5 to 3 seconds in a 40 second autocross course. I generally advise people to pick the size that gives you the same diameter as a stock 185-15 and in a width that will fit inside the rear well. With the bump stops removed and the right wheel offset you can use a tire width of up to 9.25" . The wider tires can rub on the inside front of the front fenders. Iāve never experienced any issues with that - slightly smaller turning radius only.
Our project car, a sketch of the rear structure as itās going together. Blue is the new stuff, adding stiffness, safety and about 35kg. Thatās offset by about 38kg saved in the rear suspension and differential. Only new structure is detailed, eg the new diff mount rails tie in to original structure below the floor.
The front detail is not representative of the final design, it needs to be tidied and updated when our analyst returns from sickness or when my CAD sills progress a couple of levels. More likely the former.This view makes the tunnel look three feet wide, it isnāt really.
soooo looking at this topic, the number of comments, the expertise and experience of quite a fewā¦who would tackle the task of a āwhite paperā on setting up E Type Camberāroad, autocross-trackāwith the related topics, so it is edited, peer reviewed and in one place?
Nick
Iāll be happy to write a summary after weāve demonstrated that our project car achieves its goals. Until then, Iāve probably contributed all Iām able - I have no practical experience of E-types, just a lot of simulations, calculations and words. The work weāve undertaken for our project car is extensive because there are so many areas that need to be addressed to bring the chassis structure and systems to a level consistent with the visual promise of this wonderful car. I say that with full respect to the carās creators, and certainty that they would have been delighted to use the tools and techniques available to us today. (With none of their timing and budget constraints). Iāll spare you repetition of the detail, Iām always happy to discuss and justify my views. The proof of the car will be in the driving - Utah, towards the end of the year unless anything changes. For sure. Maybe.
Best to all.
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Utah?
As in, the car will be built there?
If only it were that simple Paulā¦
It will be largely built in Brisbane but my partner in crime (as he is not so affectionately known in some more traditional forums) will move to Utah at the end of the year. The car will be shipped in whatever condition we have achieved by then, for completion in the US.
Also in that shipment will be the basis of a TR project, another story altogether.
Well, given the fact that Utah is closer than Brissy, tell him to contact me when he gets established there and Iāll be his first American friend! 
He will certainly do that, thanks
I had a look at what can be done with the upper control arm alone, not wanting to get involved with changes to the torsion / bendy bars down below. My starting point was that the upper control arm inner pivots have been dropped in line with previous discussions, and steering joint height adjusted to recover the bump steer. Then moving the UCA back 15mm raises castor to about 5 degrees, which sounds better than the standard 2 degrees to me. If, while youāre doing this probably complex task, you drop the UCA rear mount about 15mm, you get a modest amount of anti-dive. I have some doubts whether the E-type actually needs anti-dive, with its long wheelbase and relatively low cg, others could comment better, however.ā¦tilting the UCA in that way should give a ride comfort gain as the wheel now moves back slightly as it rises. Even a small amount of this recession can make a significant difference to quality feel and comfort, giving some cushion and reducing harshness on small bumps. It also keeps the upper ball joint angle similar to the original, reducing the risk of angularity problems after tilting the upright back for more castor. (Do check the lower ball joint though). It also changes the bump steer you carefully set after lowering the UCA pickups, so you get to do that again.
Iām not a fan of large amounts of anti-dive as used on some SUVs because it can affect other properties. I donāt think the small amount Iām suggesting here will have such a concern, but frankly wonāt know until we drive it. Weāll be trying it on our project car but without that āclean sheetā opportunity I wouldnāt tear up the suspension just to put anti-dive in, Iād work with the damping instead.
I have dimensions relating to the above if anyone wants to try it. So easy to widen the scope a little further, then a bit more, and there you are doing it all new. Ask me how I know.
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We started some preliminary damper tests today. On the car? Not exactly. The car is in build, 4000 miles and some months away. Iām looking to reduce on-car tuning time by getting familiarity with the dampers in advance. We chose Quantum monotube dampers because we can adjust the internal valving, where the real power and flexibility lies. External adjusters typically only vary the ābleedā condition when the suspension is deflecting slowly, such as in gentle swells and roll motion ā the overall ride and handling character of the car is defined more by the combination of piston and valve discs acting through the whole range of motion. My plan is to test a range of configurations on a dyno to get a feeling for the forces and curve shapes available from the various discs and pistons in the Quantum range. Sadly, I donāt have a test dyno at home and my wife would surely notice one being delivered so Iāve arranged help from Mr. Tee at BDR Ground Control in Bangkok. Heās a fellow damper geek with more tools and stuff than me.
Do I live in or near Bangkok? Well noā¦but we make a brief visit there every couple of weeks and BDR are close to the airport, so Iāll build some different specs at home, go and test, take home and rebuild, go back and test again, understand a bit moreā¦what could possibly go wrong? Iāve never found simulation is effective with dampers, I need to have my hands on the parts to relate that to the feel of the car. So here I am splashing around in 5W Motul, happy as could be. Come on Peter, get that car built.
My corner of paradise at home
The answer is in here somewhere
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Hi Clive A couple of observations from 30 years of modifying E Types. Anti dive - Hereās a video of me in a relatively slow slalom performance. Note the very last portion when I go into the stop box you will see the nose drop quite a bit when I brake hard. The nose takes a hard dive to the ground.
This car is actually quite quick in autocross, for example it holds (for about 10 years) the record for the street modified class in JCNA, in 2019 it set fastest time of all in the giant slalom at the ABFM in Portland, mostly against modern (and some extensively modified) Miniās. It has dropped ucaās, a bar thatās 80% stiffness as compared to a stock 3/4" bar, stock (original) torsion bars and rear springs, but with adjustable Spaax shocks set at full hard. The suspension is mostly stock because itās driven on the street.
Iād like some anti-dive because the dive on these cars is somewhat obscene, but having said that Iām not sure it would change anything in the performance department. The car goes into heavy negative camber under heavy braking because of the uca mods, but Iām not sure it makes any difference in performance. Modern radials with soft sidewalls and very stiff treads seem to be able to handle extreme camber and keep the tread flat on the ground. If it does that, braking should be mostly the same. On my car itās difficult to lock up the fronts (stock 4.2l system), but it will try very hard to pitch you through the windscreen. The difference between it and stock tires has to be experienced.
Castor- 5% positive plus performance tires - you will need power steering in parking.
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Hi Terry, thanks for your thoughts. The level of dive in your video is more than Iād want to fix with anti-dive geometry. My recent study suggested youād need a pretty significant tilt in both control arm axes, I doubt the torsion bar would enjoy that as it affected the side-view path of the wheel center, probably introducing some fight and harshness over bumps. The level of anti dive weāre using is only intended to add a little smoothness in response to a light check brake in traffic.
Have you tried longer bounce bumpers? That could be a simple way to reduce extreme travel. Iām not a fan of very long bumpers that are always engaged, in my view thatās what the spring is for, but there are some pretty sophisticated ones around that give progressive control in deeper travel without knocking you around. Iāve been looking at Mercedes bumpers which are easy to cut in sections according to need. (As in the att). Iām building a library of curves for different sections used in combination with each other and other materials, to get the best balance of control and loads. In theory this would tend to introduce some understeer but that might be balanced by reduced roll. You could try a similar change at the rear, I imagine anything that reduces the semi-independent motion there would be good. The video suggests your inside rear wheel only has an incidental relationship with Mother Earth when the going gets serious.
Obviously also the damping - I havenāt worked with Spax for thirty years, in those days their adjusting screw affected (only) the low velocity bleed part of the force-velocity curve. That would traditionally be thought to include roll and brake dive, but your video suggests a lot of energy bring thrown at the front when youāre braking - Iām wondering if that is overwhelming the bleed section so youāre also using the main system. It might be worth having your dampers tested to see what shape the curve is. Thatās what Iām doing in our current damper tests, I plan to increase the thickness of the compression discs to get a strong transition out of the bleed area to the main valve to avoid the feeling of āfalling overā in a brisk manoeuvre. We went for Quantum dampers to get the ability to adjust the whole force/velocity chart, there must be others out there with that facility.
Your point about steering effort is well taken. I wonder if thatās why Jaguar specified such a low castor angle.
