Tyre pressures and damper settings

Talk about the E-Type Series 1

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Curtis Bay
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#1 Tyre pressures and damper settings

Post by Curtis Bay » Wed Sep 04, 2013 11:30 am

I have a fully restored series 1 FHC with 205 70 VR 15 tyres (Blockleys) fitted to 6" competition rims from Phil Halliwell. Because these deviate from the standard tyre size I was wondering if anyone has any recommendations on tyre pressures? The car is also fitted with adjustable Gaz shocks all round with new springs at the rear. The car has also been poly bushed with the soft blue bushes. Does any one have suggested settings for the dampers or at least an indication of where to start the settings from?

Many thanks.
1965 Series 1 4.2 FHC - Opalescent silver blue metallic with grey interior
1974 Series 3 5.3 Auto DHC - Sable with biscuit interior - something which has to change!

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gb2601
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#2

Post by gb2601 » Thu Oct 10, 2013 5:04 pm

Hello,

we have also fitted GAZ dampers to our Series 1 FHC. The adjustment range is about 30 clicks. We prefer a setting of 8-10 clicks or two thirds on the soft side both front and rear. This gives a comfortable ride, which we like. 20 clicks make our car very "jumpy". The good thing about the GAS dampers is that you can change the setting easily. Tire pressure is 2.5 bar, with 205 70 VR15 Vredestein tyres on 6.5 rims. I hope the is helpful.

Regards, George

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christopher storey
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#3

Post by christopher storey » Thu Oct 10, 2013 6:40 pm

I urge you strongly to check the extended length of the front GAZ dampers . If it exceeds 400 mm or thereabouts by any significant margin ( ie if it is between about 410 and 430mm) then there is a real danger that eventually you will suffer tie rod fatigue fracture because instead of the dampers acting as a downward stop on the suspension travel, the tie rods are doing so . I discovered this when the wrong dampers were supplied to me ( not GAZ ) and suffered a fracture , fortunately at low speed . Investigation then revealed that most GAZ dampers are too long to restrain the downward movement of the lower wishbone before the tie rod necks on the ball joint with the rack

If you search for "fatigue" on this board you will find a thread headed "steering tie rod fracture" which illustrates the problem with pics and further detailed information from a variety of contributors

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andrewh
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#4

Post by andrewh » Thu Oct 10, 2013 6:45 pm

hi Christopher, what do you mean by the tie rods? Do you mean the track rod end? or the bottom suspension bracket that carries the lower fulcrum?
1962 3.8 Series One FHC

http://etype860897.blogspot.com/

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christopher storey
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#5

Post by christopher storey » Thu Oct 10, 2013 6:47 pm

Andrew : see my addendum about the original thread which illustrates it graphically. By tie rod I mean the rod which attaches to the rack ends by a ball joint, and to which the track rod ends screw on at the outer end

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abowie
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#6

Post by abowie » Thu Oct 10, 2013 10:22 pm

I run 40psi front and rear and have my Koni's set in the middle. I have 205/65/15's on 6.5" MWS rims. I also have a 15" Nardi steering wheel. This gives me a tiny bit of bump steer but means that I can actually turn the wheel while parking.
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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Heuer
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#7 Re: Tyre pressures and damper settings

Post by Heuer » Fri Oct 11, 2013 11:03 am

Curtis Bay wrote:I have a fully restored series 1 FHC with 205 70 VR 15 tyres (Blockleys) fitted to 6" competition rims from Phil Halliwell. Because these deviate from the standard tyre size I was wondering if anyone has any recommendations on tyre pressures? The car is also fitted with adjustable Gaz shocks all round with new springs at the rear. The car has also been poly bushed with the soft blue bushes. Does any one have suggested settings for the dampers or at least an indication of where to start the settings from?

Many thanks.
I am afraid you are going to have to work out these settings yourself and repeat everything Norman Dewis did when developing the E-Type. You have multiplied the problem to the power of four because you have so many variables to play with:

1. shock stiffness
2. tyre size
3. tyre pressure
4. steering wheel size

I suggest you proceed as follows in an attempt to reduce the work load:

1. set the Gaz shocks to the same stiffness as a standard Boge. Difficult to do without the correct and expensive measuring machine but you should be able to get it near enough. Buy or borrow a new front and rear Boge and adjust the Gaz to have the same level of stiffness on the up and down stroke for each. This will be your base line to measure change against. Make a note of the settings!

2. Ideally you should have a set of 185 tyres to act as a benchmark but this may be unrealistic so all your setting will be based on your current choice of tyre

3. Set the tyre pressure to 32psi all round and leave it at that. You can fine tune later if you really want to

4. Find yourself a section of road, preferably a loop, and run the car through it. Change the Gaz setting one click at a time on all six shocks together and repeat the run. Iterate until you are happy. If you want to alter the f/r ratio Gaz settings only change the front.

5. You can now repeat the runs with different tyre pressures but be warned the E-Type responds very quickly to such changes. With my Michelin 185 VR15 tyres I have found 35psi rear and 30psi front to suit my driving style. When I tried those settings with 205 tyres the car behaved terribly.

The lesson is stick to totally standard if you want to go out and enjoy the car as Norman did all the laborious work for you. If you enjoy tinkering go ahead with 'upgrades'. I also suggest you take seriously Christopher and others comments about the Gaz shocks being the wrong dimensions for the E-Type with potentially catastrophic results. Personally I would fit standard Boge shocks, put the Gaz on eBay and go out and enjoy the car!
David Jones
S1 OTS OSB; S1 FHC ODB
1997 Porsche 911 Guards Red

Add your E-Type to our World Map: http://forum.etypeuk.com/viewtopic.php?f=1&t=1810

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fbing1
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#8 Suspension settings and tire pressures

Post by fbing1 » Tue Oct 15, 2013 10:10 pm

Every car set up differently from stock is going to be a bit different in that you really need to pick a setting and then make changes to one aspect at a time, say front tire pressure. Then test and make another change. One at a time...unless you are feeling lucky.

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Moeregaard
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#9

Post by Moeregaard » Wed Oct 16, 2013 4:35 pm

As David said, Norman did all the "heavy lifting" back in the day, so factory settings are a good start. When I ran Konis and 185-15 Avons, 32 psi on all four corners, with the dampers at their lowest settings worked well for many years. I tried these pressures with some no-name 205/75 rubber and this gave the car a "nervous" feeling at cruising speeds. My steering wheel was a 15" Moto Lita.
Mark (Moe) Shipley
Former owner '66FHC, #1E32208
Former owner '65FHC, #1E30036

Planning on getting E-Type No. 3 as soon as possible....

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Curtis Bay
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Location: Blockley, Gloucestershire
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#10

Post by Curtis Bay » Tue Oct 22, 2013 7:15 pm

Thanks to everyone. I don't plan on changing the tyres or dampers but will take on board the advice about checking the extended length.

Shame the weather has turned wet - looks like test runs could be postponed for a while.
1965 Series 1 4.2 FHC - Opalescent silver blue metallic with grey interior
1974 Series 3 5.3 Auto DHC - Sable with biscuit interior - something which has to change!

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