Author Topic: Suspension tune and handling journey  (Read 5078 times)

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Offline BDA

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Re: Suspension tune and handling journey
« Reply #15 on: Thursday,July 25, 2019, 03:50:43 PM »
I hadn't suspected that - obviously - but it makes sense... What was your clue, JB? Thanks for pointing it out!
« Last Edit: Thursday,July 25, 2019, 05:00:29 PM by BDA »

Offline jbcollier

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Re: Suspension tune and handling journey
« Reply #16 on: Thursday,July 25, 2019, 05:03:03 PM »
The fact that I had a bent one as well!

Strange there is no included angle read-out.  That's how would know for sure if it is an upright or something else bent.  Ask the alignment shop if they have the info and it just doesn't show up on the customer read-out.

Offline BDA

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Re: Suspension tune and handling journey
« Reply #17 on: Thursday,July 25, 2019, 05:05:28 PM »
Since you've been here before, where did you get your replacement and what should I expect to pay?

I'll ask them about the included angle.

Offline Certified Lotus

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Re: Suspension tune and handling journey
« Reply #18 on: Thursday,July 25, 2019, 07:48:50 PM »
I’m book marking this topic as I will need to reference shortly.

Offline jbcollier

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Re: Suspension tune and handling journey
« Reply #19 on: Thursday,July 25, 2019, 08:18:31 PM »
Most of the British car suppliers carry them.  I got my last set from Rimmer Bros.

Offline BDA

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Re: Suspension tune and handling journey
« Reply #20 on: Thursday,July 25, 2019, 08:23:44 PM »
I'm a slow learner so it took me many years, and other people talking about it, for me to actually realize that with stiffer springs, you need stiffer shocks. If your springs are a little stiffer than stock, you might only need minor changes in your shocks. If you read the article I mentioned earlier, you learn that when going into a turn especially, stiffening the front shocks acts like a stiffer front roll bar - less oversteer. I am positive I am missing a lot of the finer points of shock tuning but so far it's working pretty well for me. Keep in mind that my springs are about double the stock spring rate. I think not realizing the implications to that is what caused me a lot of grief. Having springs that are not as drastically different might make life a bit easier for you. I think that the stiffer springs will ultimately yield better handling if properly tuned and hopefully that can be achieved so that I don't shake my eyeballs out of my head. So far, I'm optimistic.

Offline BDA

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Re: Suspension tune and handling journey
« Reply #21 on: Thursday,July 25, 2019, 08:24:12 PM »
Most of the British car suppliers carry them.  I got my last set from Rimmer Bros.
Thanks, JB. I'll look them up.

Offline literarymadness

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Re: Suspension tune and handling journey
« Reply #22 on: Thursday,July 25, 2019, 08:46:24 PM »
Here  are PSI manufacturer recommendations from Toyo for their tires.  Tire pressures change based on the weight of the vehicle.  There are  suggestions how to help oversteer and understeer. Of course PSI ratios should be altered for mid-engine cars.  But the Europa is definitely in the under 800 kilos and those PSI numbers are low.
« Last Edit: Thursday,July 25, 2019, 08:57:42 PM by literarymadness »

Offline EuropaTC

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Re: Suspension tune and handling journey
« Reply #23 on: Friday,July 26, 2019, 12:33:17 AM »
Thanks for posting those details, I've not seen that detail about pressures/weights written down before.  It does explain why 30-35psi seems to be the norm these days with a lot of modern cars being over a ton and heavier.

Brian

Offline BDA

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Re: Suspension tune and handling journey
« Reply #24 on: Friday,July 26, 2019, 05:56:00 AM »
Great post, L'madness! It appears I and some of my friends had it backward on pretty much every point back in the day! I'll adjust accordingly.

Offline literarymadness

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Re: Suspension tune and handling journey
« Reply #25 on: Friday,July 26, 2019, 09:50:31 AM »
Thanks!  BDA, I would definitely A/B your TCS mechanically to Pfreen's car who generously posted his specs on this thread. I've ridden with him in his car at +80 mph speeds and his car is incredibly stable. I've also observed his car from my car on the road while driving in several local rallies and caravans.  It is solid and stable.  Pfreen won't dote praises on himself, but he is a retired automotive engineer who worked for both Chrysler Corp. and BMW (and almost worked for Lotus).  He holds several automotive patents while working for BMW. He has helped me make several improvements on my car that substantially improved my car's handling. 

Offline BDA

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Re: Suspension tune and handling journey
« Reply #26 on: Saturday,July 27, 2019, 01:14:04 PM »
My next concern was the lightness of the steering. It felt so light that when going down the highway, it took a bit of concentration not to move t he wheel which was very sensitive. A small steering input at speed gave the feeling that disastrous results were imminent. I thought this was a good time to try to tighten up the steering.

I have recently rebuilt the rack from (lightly) used Spitfire parts. The manual gives a procedure for getting the proper stack of shims under the cap nut to give the correct resistance for turning the pinion. Then they give the spec for how much turning resistance you want (2# on an 8" arm on the pinion). In my case, doing the first did not give me the resistance I was supposed to want. In the end, I think I went with the resistance regardless of the shims required.

Last night, I fooled around with shims to get more resistance. In the morning, I went to the local MG club breakfast and found that the steering was way too stiff. I reshuffled the shims to get to the next taller increment in shim height to loosen it a bit. I can't be sure, but I suspect that I'm back where I was after I rebuilt the rack but I'm not positive. While I did that, I gave the front shocks one more click (F: 5 clicks, R: 3 clicks).

The result was more improvement in all aspects. My speed and comfort in a twisty section were increased. Highway driving at 80 mph or more was a bit more stable. The surprising thing is that the steering seemed to be a little heavier also. The steering was less nervous and twitchy. I should also say that on normal roads, the stiffness in the suspension is noticeable but not bad at all. As you might bumps that are a "problem" are starting to get smaller. Also as I say, I can't be sure my changes to the shims under the rack cap nut but this effort really began when I read some posts on the yahoo group that cured their highway stability issues on their car with stiffer springs by stiffening the shocks so I don't discount it.

Future plans: There are some alignment issues I may address soon. Pfreen's earlier post saying he runs 0 camber in the front intrigued me. Clifton and I have been discussing things via email and his front has less camber than mine but more than Pfreen's. I'll probably try splitting the difference. As JB said, it's likely that I have a bent passenger side upright. I wouldn't dispute that (and I haven't gotten around to asking the shop that did my alignment if their rack measures included angle) but one of the benefits of having the car since new is that you know the history and while there was a hit on the driver's side front, there was never anything on the passenger side front so it seems unlikely. I wonder if I could possibly have the uprights switched and the original driver's side upright is now on the passenger side. In the mean time, I may see if I can get more caster on the passenger side without replacing the upright. At some point, I will go back to lower tire pressures but more immediately, I will experiment more with stiffening the shocks. I'm thinking my strategy might be to stiffen the front till I get some understeer (or it's just too stiff) and then I might experiment with the relative stiffness  between the front and rear as well as the absolute stiffness. Another thing I'll be doing is setting less toe-in for the rear.

Don't touch that dial!

Offline EuropaTC

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Re: Suspension tune and handling journey
« Reply #27 on: Saturday,July 27, 2019, 02:21:25 PM »
I think you could go more on the dampers although it's a long time since I had any Spax dampers so I'm not familiar with the total damping forces available, I'm just guessing based on the 14-click range.

If the primary job of the damper is to reduce the spring oscillation then it seems to follow that a stiffer spring will need more stopping power and hence stiffer dampers. 

I don't think there's anything wrong with starting at zero and working your way up but I'm less patient. I drove mine with nothing on the Protechs and then took them half way with the intention of the next drive being full stiffness.  After the second run I decided it wasn't bad for the roads I drive on and didn't feel I needed more so I never bothered with the final setting.

The principle of getting three points on the graph at zero, middle and top so you know the full range available and how it relates to driving doesn't seem unreasonable even if the full setting shakes your fillings out....    (at least you'll know not to go there again  ;)  )

Brian

ps I'm also intrigued by the zero front camber comment and would like to understand why it's beneficial.  I could see how it might make the steering lighter but I was hooked by the comment that it improved stability at speed.  Simple explanations please !

Offline BDA

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Re: Suspension tune and handling journey
« Reply #28 on: Saturday,July 27, 2019, 02:45:30 PM »
Yeah, the old binary search principle! One of the fastest ways of searching an ordered list is to go to the middle and test. If your target is lower, go to the middle of the lower part of the list or the higher part if higher and test and repeat till you find it. I don't really have a good reason not to do it that way but I think I want the lowest dampening that works. I think I want to sneak up on it, too. And then I don't KNOW there are 14 clicks. The Spax guy wasn't sure.

I'm familiar with the idea of what dampers are for and it should have occurred to me earlier but the car didn't bounce or otherwise give me any of the standard reasons to suspect the shocks, and then In spite of the fact I did some racing in my past I never explored monkeying around with suspension settings and then the shocks I used were not adjustable.

I think you're going to have to ask Pfreen about his 0 front camber setting. He mentions it in a previous post on this thread. Clifton said he uses 3/4 degree all around and he says his car is stable at 125.

Offline Pfreen

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Re: Suspension tune and handling journey
« Reply #29 on: Saturday,July 27, 2019, 05:06:32 PM »
I didn't invent 0 degrees of front camber..  It’s in the manual.  0 deg+-30’.

Camber is good for cornering since the goal is to maximize the tire contact patch area.  I know others set their cars up with at least 1 deg negative for autocross. I believe them.  That doesn’t necessarily make it good for expressways.  I used to have mine set up with 1 to 1.5 deg negative front camber and per spec front toe.  High speed stability was terrible.

Also, tcs Europas, at least Literary’ s and mine, required almost a 1/4 “ of washers per side to bring the rear toe into spec. 

Handling is not my expertise, in spite of what Literary man said.  I only wrote what worked for my car.

I basically set the car up as standard alignment, but lowered, with hopefully consistent , solid bearings and suspension.

The book, “How to make your car Handle” by Fred Puhn by hp books is a great reference, if you all are interested