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Tightening the suspension bolts without the body on...


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I want to finally torque up all the suspension bolts whilst I still have the body off my S1. I have a load of those strong plastic boxes that somebody gave me so I was thinking of stacking them on the subframe and then filling them with water. The question is how many kilos does a body, glass and interior weigh?

 

I know that 1 litre of water is going to weigh 1kg so it should be relatively easy to get the weight about right and have it distributed over the chassis.

 

Paul.

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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I read somewhere that it was a 4 person lift, so I would presume that the shell was less than 320kgs. Add in seats, all up 350ish.

Distribution wise, I'd say the shell c of g would be around the centreline of the driver, noting the weight of the doors, driver and fuel load are factors.

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I don't see how you're supposed to get access to all the bolts in your garage without a 4 post lift and I don't fancy driving it to a garage with none of the bolts done up!!

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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Yes but I can't see how I'm going to be able to do it. I don't have a 4 post lift or access to a trailer either. Ho-hum...

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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4 axle stands and a trolley jack and tape measure?

 

Or let me thrown in 'do them up tight, take it to a garage for them to put on a lift to torque up correctly' or spend £50 to hire a trailer and tow it down there with them tight enough to push it or winch it onto the trailer. 

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It's all down to ride height....whether or not the body is on is immaterial. If you get the ride hights set correctly, adding whatever weight you need, then tighten up the suspension, it will be correct. 170mm from memory, measured from the bottom of the front chassis uprght bits by the radiators and the bottom of the chassis by the lower links at the back. Once the ride height is correct, then the suspension will be loaded to the right amount and all the angles will be right, too. Keep the nuts loose and add weight until you have the right ride height...bounce up and down a few times until you are happy with the measurement...then tighten it up.

Liable to be quite a lot of weight and a very fiddly and iterative procedure....and you still have the centre of gravity to consider...

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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I will consider also that these measures were the original Lotus at the time...but with different not original bushes, not original dampers, not original coil maybe, etc...etc... I would not be so sure that you need to keep these quotes as a reference...

Just my two cents Paul.

 

Ciao

Giorgio

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It's all down to ride height....whether or not the body is on is immaterial. If you get the ride hights set correctly, adding whatever weight you need, then tighten up the suspension, it will be correct. 170mm from memory, measured from the bottom of the front chassis uprght bits by the radiators and the bottom of the chassis by the lower links at the back. Once the ride height is correct, then the suspension will be loaded to the right amount and all the angles will be right, too. Keep the nuts loose and add weight until you have the right ride height...bounce up and down a few times until you are happy with the measurement...then tighten it up.

Liable to be quite a lot of weight and a very fiddly and iterative procedure....and you still have the centre of gravity to consider...

I've heard of people adding bags of sand to load the chassis but water seemed like an easier option to me.

 

I will consider also that these measures were the original Lotus at the time...but with different not original bushes, not original dampers, not original coil maybe, etc...etc... I would not be so sure that you need to keep these quotes as a reference...

Just my two cents Paul.

 

Ciao

Giorgio

Yes that's a fair point Giorgio although my springs are original and most of the bushes are too.

 

Cheers, Paul.

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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Hi Paul, your topic has stuck in my head! Lol. Are you going to give it a go?

As it's been said, you add weight to get the spec ride height - filling boxes of water sounds good to me. Maybe one niggling question though - will the suspension be affected by a prolonged weight-off-wheels afterwards?

Iain

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Really don't know to be honest. So far I have yet to find in the manual what the ride height is supposed to be and I don't see how you could adjust the front? My car currently has a massive gap between the top of the front wheel and the wheel arch. It doesn't have any interior in it and the windscreen isn't fitted but I can't see how it's going to drop that much????

 

Cheers, Paul.

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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The ride height specification isn't about adjustment on the earlier cars, it's a way to check that parts are as they should be. It drops enough to make a difference and those bushed would then be strained further than desired when laden, and attempting to push the car back up instead of down when the suspension is already extended.

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My limited understanding is that the suspension bolts need to be torqued up with the correct loading on the chassis. That loading is provided by the body, fuel and occupants. It seemed to me (in my ignorance) that a similar loading could be put on the chassis to create the necessary weight to achieve this and then I could do the bolts up before I put the body back on, as I don't have access to a 4 post life. Somebody above suggested that there were measurements that could be taken somewhere to determine when this optimum weight had been reached but so far I have yet to find them. I am no mechanical engineer so could be talking utter b***ocks.

 

Paul.

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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You are correct Paul, you can do it that way, but you seem to be under the incorrect impression of needing a 4 post lift if you don't do it now. With the car assembled it's still fairly easy to do the bolts up, but if you want to do it now (keep in mind it will then stress the bushes in the wrong way for as long as it takes you to finish adding the rest of the car to the subframe) the ride height is specified in the manual. I don't have it to hand but recall it as being 170mm from ground to the bottom of the front subframe cross member.

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The reason I was thinking of the 4 post lift was to make it easier for myself to get at the bolts to torque then up I'm not a young whipper snapper like the rest of you! When I try laying under cars now there are bits of me that ache that I didn't know I had 30 years ago.

 

If anybody knows where to find the ride height figures please let me know - I can't see them.

 

Am I understanding this correctly... you have to load the car to get the correct ride height bearing in mind that you cannot adjust the front at all. The rears are adjustable via the spring perch.

 

Paul.

Lotus Esprit [meaning] a 1:1 scale Airfix kit with a propensity to catch fire

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4 axle stands and a trolley jack and tape measure?

 

Or let me thrown in 'do them up tight, take it to a garage for them to put on a lift to torque up correctly' or spend £50 to hire a trailer and tow it down there with them tight enough to push it or winch it onto the trailer. 

 

I'll be stripping and replacing the front suspension when I get back from holiday, and the first part that Bibs suggests is how I intend to torque things up.

 

- Measure the wheel to wheel arch dimension (12 o'clock) before disassembly*,

- jack up the car so all wheels are off the ground,

- do the work... 

- and when the time comes to tighten the bolts use a trolley jack on each front wheel (at the same time so 2 jacks are required) lift the wheels to the before measured dimension

- get under car and torque as necessary

- once done put the car back on the ground and confirm settings such as the ride height, (need to recheck bolt torques?).

 

Does this sound okay? 

 

*Using this method Paul, you could use another datum point as you don't have the body on the car? 

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Just to put a spanner in, after running, a few hundred miles, include some cobble stones, you are going to have to reset it anyway. The chances of not having to do this are minimal, and I would do it as a matter of course anyway.

The Roger Harris approved method is as follows. Jack up car, loosen all the bolts holding suspension bushes, and put the car down again. Now you will probably need two jacks, because you need to remove one wheel and have a jack directly underneath where the shock mounts, now jack it up until a second wheel comes off the ground, now tighten the bush bolts, repeat on all 4 wheels.

After a rebuild or fitting new bushes, you should repeat the operation after some mileage. This method will bring you spot on to right ride height, that is assuming spring lengths etc are OK.

Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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