Getting the best out of standard suspension components for touring driving today

I used 205/65’s on Tweety: I did notice a slightly better level of grip in the really twisty pits, but a much higher low-speed steering effort.

I propose that a good development engineer would not create this situation in a car to be sold to or used by a range of drivers in a range of styles and situations. Rather, the car should have a performance balance which would be familiar at any level. I’m being slightly provocative to wind up Mr Wiggles, but I seriously believe the car should not change its fundamental nature at high duty levels. The last thing a naive driver needs in an unplanned avoidance situation is unexpected reactions from the car.
My philosophy is to make the performance more approachable and consistent across the performance envelope, not to create a bragmobile for the elite.

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No wind up at all!

However, having put a number of cars on the 10th/10th point, I can assure you that I have never felt the car that didn’t change at that point… Again, for a street car I generally tend to agree with you, but the nature of physics is that at the ultimate level of adhesion, any given car will exhibit slightly different tendencies, than the other 9/10ths.

As you very well know, every single car platform on the planet is some series of compromises: street cars, are the widest set of compromises, whilst racing chassis are the smallest set.

That said, one has to carefully look at the performance envelope that any given car is expected to be in at the 85th percentile, and design for that envelope.

well we got up from 6 or 7/10ths to 9/10, I’m fine with that!

We should move some of these discussions to a single table with some refreshing libations arranged thereon.

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Ok so what level of driving is “ normal “ road use? …. Then add 1/10 for those a that are general e type drivers …. And let’s say that’s the safe limit for us as no. Racing drivers and then work on that as how we should set up the car

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I think that somewhat self-explanatory: it’s driving a car on street conditions, on street tires, in the occasional twisty bits, and mostly on highway and surface streets.

It is my considered opinion, based on years of having instructed high-performance driving, that the slightly-better-than-average driver is only capable of putting the car in about 5 to 6 tenhs.

Beyond that requires better instruction!

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Ok so let’s limit the discussion to that then

I just put original size tires back on my TR-4A (165R15s). In my younger, vainer days I had 185/70VR15s. While they looked meaner and filled the wheel wells, they were much duller and made the steering heavy. With the 165’s, the car once again feels like a proper English sports car: Spritely is the word that comes to mind.

I’m doing the same thing on my MKII - 205’s down to 185’s. I’ll let you know how they feel after this weekend.

We haven’t addressed ride quality. To me, that balance with handling is where the magic lies. That’s why I put such focus on damping, it’s the big switch that brings the car to life.

My search for data on the original dampers isn’t idle curiosity, I want to understand what Mr D put in them. With that knowledge, and the damper technology available today, I don’t think it’s unreasonable to suggest we can take it a step further while keeping the essential qualities of the original.

What do I mean by a step further? Using the greater adjustment and flexibility of modern dampers to match the curves more closely to the conflicting demands of the structure, the tyres and the suspension. A project to keep the mind active and fingers oily.

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I think that is a reasonable and laudable goal.

That’s gonna be a little hard to narrow down

Since were talking about cornering behavior here, I think I take almost every corner faster than any of the drivers around me. On twisty roads I’ll corner hard enough to feel some g-force or hear the tires work a bit. That’s about it. Not a madman with my hair on fire. Brisk, sporty, and with …you know…verve :slight_smile:

More than putt-putting around like the car was made of glass. Less than auto-cross or slalom.

I’m attuned to how the car is behaving and responding

Cheers
DD

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Which is something I’ve always liked about Jaguars. They’re utterly controllable and predictable. Never treacherous…unless you’ve done something to make one so.

My TR6 is nimble and responsive and you can easily “toss it around”. That’s fun. But it takes on some odd and twitchy characteristics when pushed a bit. The suspension, really, is terrible.

My Jaguar behaves much better when driving fast on curvy roads. Nothing weird ever happens, even on the bumpiest or must usually configured corners. I’m quite surprised at how fast I can take corners with confidence. At 4300 pounds curb weight, though, it doesn’t “toss” like a smaller car would.

Cheers
DD

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Thanks for the suggestion, I’ve ordered a copy of the Porter book. I’m conscious there are some questions over the front structure but my thought of revising the damping need not compromise that. It comes back to the shape of the damper force-velocity curve. I’m assuming the E-type dampers used blow-off valves, typical of that era. They gave force-velocity curves which were pretty much linear as in the sample graph (pulled off the internet at random, for illustration).


Horizontal axis is the speed at which the damper is being compressed and extended, from a gentle roll motion up to a significant impact event such as a road joint. Vertical axis is the resulting force generated by the damper.

Lack of stiffness in the structure typically requires high-velocity forces to be backed off to protect its integrity and avoid shake, but then the entire curve reduces slope so control is reduced in lower velocity events, such as ride and roll motion. (Blue dotted line below). I speculate this is, to some extent, the E-type dilemma.

With later damper technology, using a tapered stack of spring discs instead of a coil spring, we have more opportunity to shape the curve, shielding the structure from high forces while retaining more control for body motion. Below is a rather extreme example from recent testing with our Quantum monotube dampers.

My idle thought is that there may be scope to tune a traditional twin-tube damper to similar effect, within the size of the original damper. It won’t necessarily increase loading on the structure as it redistributes the force through the cycle.

All speculation, years and thousands of miles from an actual car. Worst case is I’m completely wrong, I will report back to that effect and another interesting discussion will start.

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Something I think is often overlooked is tire width versus rim width. Specifically too wide tires on too narrow rims. The sidewall pinch, if excessive, can alter the behavior of the tire and thus the behavior of the car.

Jaguar tended to be skimpy with rim widths, at least into the 90s, as tires grew wider.

And of course different tires can have different sidewall construction and/or stiffness which plays a part in how a car behaves through the corners and responds to steering input.

The PO of my TR6 had 60-series tires installed. The sidewalls were very rigid. The tires beat the poor car to death and tramlined all over the road.

Cheers
DD

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Yes it is. That and the floppy structure were the reasons I decided not to do a total rebuild of a TR5 I’d owned since student days and stored the past thirty years. After being immersed in an E-type project for the past couple of years I accepted I could pour a lot of money into the TR and still not enjoy driving it. I sold it last year, with some sadness.
Now I just need to get the 1964 Lambretta out of storage…

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Well we’re making progress on testing some original dampers, that will be interesting. Does anyone know what the inside of a Girling damper looks like? Does anyone have a junk damper they’d be willing to sacrifice to a good cause?

Flushed with that potential success, naturally I thought of springs, because I’m curious to know what the ride frequencies are. Those give a good definition of where the car sits on the comfort-sporty axis - does anyone happen to have that information? Maybe it’s in the book I just ordered, it’s certainly something the Jaguar engineers would have used in their design and development.

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Wow what a “can of worms” I’ve started with this…. I thought Clive and now Tom would just give us a quick tip or two…… this has moved to another level…… fascinating and interesting….and a lot of work being put in by you Clive , I’m sure we appreciate your efforts

Moral of this story is not to ask “simple” questions

Nothing wrong with asking simple questions, Danny: what I discovered a long long time ago, however, is when you’re dealing with suspension, you cannot just pick one single little thing out of a whole nest of possible parameters.

It took me years to kinda mostly grok how suspension dynamics work. Notice I said, ‘mostly!’

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J-L has lots of smart people who know and understand lots of interesting stuff. A lot of it is over my head for sure.

In thinking about this thread I was wondering what suspension/handling characteristics you want to change, as “getting the best out of standard suspension” might mean different things to different people.

Cheers
DD

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No worms, I see it as a good opportunity to share thoughts and knowledge. You’re the people with the cars and the knowledge of them, I have a bit of experience that might have some relevance.
Simple gains are unlikely because the Jaguar engineers were clever people and any easy fixes have long been disseminated and implemented. By current practice the chassis systems have some idiosyncrasies but they are all so interlinked that it’s hard to change one area without affecting others. Very quickly we come up against the originality question, then it tends to “all or nothing”.
To me it’s still interesting and informative to study the original in detail. When it all goes silent I’ll know we’ve finished another topic and it’s time to move along!

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