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

Another new piece of learning, what a day that was :smiley:

I see the taper would help retain the original Jaguar bushing, less sure of its value with an aftermarket shouldered item.

It will be delicately rendered into a plain bore to allow use of a sleeved bushing for stiffness tests.

I thought I’d just do a quick check that the bracket could take the stress of a steel outer sleeve pressed into it - must be a while since I’ve done that stuff, looks like a pterodactyl print on the cover of my old text book

Can anyone tell me the diameter of the lower control arm fulcrum shaft, the section where the bushing sits please?


Ideally to 0.1mm or equivalent.
Thanks

Tough crowd. I’m going with 13/16", looking for a bushing to suit.

Update on modifed rear cradle mounts:

Last year Clive modifed 2 cradle mounts. You can see the detail in the thread above. The focus was to add lateral stiffnes and tweek the roll steer (IIRC)

Clive sent them to me and I have finally completed on road evaluation. My car is a pretty stock S2. It has Gaz shocks and 205 Michelin tires.

I drove on public roads at different speeds in different corners. Mostly below the limit except one roundabout. So nothing like on a track with slicks like Terry relates above. I used a technique of trying to uset the car while in a turn with abrupt inputs (steering, brakes, throttle). Also ran some hard braking and added steering inputs.

I ran three iterations. The first used the 54 year old original cradle mounts. Really a good warm up with little meaning. Secondly, Clive’s modified mounts at the rear paired with 2 new “genuine Jaguar C17198” mounts from SNG. Finally 4 of the geunine mounts.

Second and third iterations are very similar. In general the car is well balanced and well-behaved. It may be biased a little bit towards isolation, but when pushed it does what it’s supposed to do.

The only difference I found was Clive’s mounts added just a little more responsiveness just off center. The car turns a little faster right as the wheel is turned. It is a small difference, but directionally correct. And after all it was only a small change to the car.

I look forward to further developments.

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It’s good to have this little bit of anecdotal evidence, but I believe the only real test of any modification like that is going to be on a track and/or on a skid pad.

To me it’s more than anecdotal. Expert opinion from careful subjective evaluation is counted as data in the very large vehicle manufacturer where Tom and I worked. When it comes to final decisions it can count higher than actual measured data because it directly describes driver interaction. I’m grateful that he offered to do this because I wanted the result to be neutral, with no influence from me.

I didn’t look for track tests because this is about subtle nuances of feel and response that make a car imperceptibly more pleasant in a moderate road drive, but would probably be lost in the aggression of exploring the track limits and running for lap times. Lap times really aren’t an important differentiator for a road car - it’s very common to select for production a tyre that was not the fastest on the track but just “felt better” overall.

I’m happy with Tom’s finding as it confirms my feeling that we can adjust the feel and response of the car by tweaking the relative IRS cage bushing rates. That is a valuable piece of information when there is so little available to change back there. I’d have been happy if the result was negative, as long as something happened! I’m not worried that the effect was small because the change was small. This gives me confidence to take the next step and make some mounts for the rear location that are significantly stiffer than the original parts, aiming for a more notable change in behaviour.

I realise this has very low significance to the vast majority who are very happy with the performance of their cars. Thanks for humouring me.

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image

I’ve found a promising bushing for the LCA front position, diameters are good but the inner and outer tubes are 5mm shorter than the standard bushing. Can this work, with suitable spacers?

It’s significantly stiffer than the original part, could be a good match and support for the IRS cage work.

I would say yes, just get some spacers spun up on a lathe.

Now for something completely different - I recently rediscovered a box of stuff left by my father, including a large ring from his time in Austria with the British Army,1945-47. I was surprised by the similarity to the later Jaguar emblem. Maybe it’s a common image?

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Ah Mr Wiggles ……. What’s the title of this thread again?

I haven’t forgotten the title, Danny: however, the scientist in me takes over!

One can certainly, and most validly, do this work for the “feeling”, but to definitively determine the exact response, takes either lotta driving on the track or a skid pad. There’s nothing wrong with what Tom has done, and it’s a valid data point, but it’s still anecdotal.

Yes I agree Paul it is anecdotal …. And also subjective …what Tom notices ……I am unlikely to notice I expect !

I bet you might!

It was always a bit challenging, being my own mechanic, driver, and design engineer, so I was always aware that what I “thought” the effect was, of any given modification I did to my racecar, was good.

I actually was lucky enough to have a cadre of friends who were also very intelligent when it came to this kind of stuff, so sometimes at the track, when I was testing, I would have them do whatever change on the car that we thought, then I would walk away.

They would sometimes either do it or, they would sometimes not do it. I’d go out test and report. I ended up being only about 80% correct about the placebo effect on the Suspension. That’s part partly why I’m wary of anecdotal evidence.

I absolutely disagree, of course. I understand anecdotal to mean story-like, lacking in evidence.

The evidence here starts with a great deal of analysis in a sophisticated set of software, charts and tables saying “do this”. It follows with a professional evaluation from an experienced specialist. Lap times are irrelevant here - going faster is not the point of the exercise. It’s about improving the faithfulness and solidity of response under moderate cornering conditions - how we behave on the road, and a quality you don’t need a track to explore. Taking lap times means running the car at its limit, and that is not the point of this exercise. Taking lap times while driving in brisk street mode is meaningless. Yes, you would want to check handling at the limit but that doesn’t need measured laps either. A good driver might add a subjective comment of a gain in security feel and response - in which case we didn’t need the stopwatch, just his words.

With respect, it’s a considered observation from a trained professional - that counts as data to me. You don’t need to notice the specific effect in so many words - my entire aim here is to make a package that makes the car feel better in some subtle, indefinable way - could be slight gains in response, precision, stability, fun - it doesn’t matter what the word is, it just needs to add up to a gain that improves your experience in your car. That’s what sets the best cars apart from average ones - they don’t shout “I’m great” in your face, they just do what you want with less conscious thought and effort, more satisfaction.
That’s what I did for a living, and it’s why I have no interest in race tracks.

Excuse me, where were we?

I think we’re getting a little sideways here: I agree with your basic observations, but lacking a objective series of tests, in a closed and controlled environment, it still remains anecdotal.

Anecdotal does not mean automatically you reject that data point, but it doesn’t change it being an anecdotal observation. I also don’t care about lap times (in this context), but a race track gives you a closed environment that’s repeatable that makes it more specific as to what changes are effected by any given modification.

I hope that clears this up, because I’m not trying to fight you on this.

I agree with you here, it’s a risk that requires constant vigilance even among professionals. During a long test program some tyre companies will throw in a repeat tyre under a different code to see who’s paying attention.

I see it as a particular risk with private owners spending their own money and time installing new, supposedly better parts. Very hard to stand up later and say it was a poor idea.

Please note, though, the evaluation here was done by an independent professional with vast experience in this very area. I supplied the parts, told him enough to do the job, shipped the parts to him and left him to do it with no pressure on time to complete. I am very confident there was no risk to the objectivity of this result.

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I am not arguing otherwise.

No fight intended, just me getting a bit passionate about a subject I get passionate about. A good discussion to continue in a car.

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Always the best “office” in which to have these discussions… :slight_smile: