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Is my chassis right? Rear radius arm mount shims - Page 2 - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums Jump to content
GTK

Is my chassis right? Rear radius arm mount shims

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I wish you luck with that... I think you may need it.

Having just binge watched episodes 27-37 of Soup, I have complete faith in your ability to get that chassis bang on. But then every other component between the chassis and the wheel rim will need to have been fabricated, cast, machined or drilled to within minute tolerances of its opposing part to enable symmetrical shimming. Yes get the chassis flat and true, but I just don't think symmetrical shimming is viable or necessary and not worth beating yourself up over.

21 hours ago, GTK said:

I'd love to think I could get the setup symmetrical,

 

 

 

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In light of some new information, I may have said that a little prematurely :whistle:

I have many questions, some fairly fundamental, so I'm going to go do a lot of reading. But I'm curious about why the large shims are only available in three sizes? I mean if those two on the N/S of my car are 1.5mm, am I wrong in thinking it'd be better to have a single 3mm spacer. I know it's possible when I'm done with repairs I'll need a whole other shim setup, but conceptually; could I figure out the optimal setup and then reduce the number of shims by making single ones in the appropriate size? Also, lighter.

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@GTK have you been on the Guinness again, 1 x 3mm steel shim will weigh the same as 2 x 1.5mm steel shims. But if you need to increase the toe-in by a small amount, it would save you a few bob to remove one of the 1.5mm shims rather than removing a 3mm one and having to buy a 1.5mm one to replace it.

I also mentioned earlier that split halved shim plates were available for the V8, to negate the need to remove the trailing arm for Geo adjustments. Having had another look at the V8 manual, it states that the late split shims will also fit ALL 4 cylinder Esprit derivatives.

 

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44 minutes ago, giorgio67 said:

Are you sure that 3 washers between nut and arms are correct?  

Don't think so.

 

 

Yes...for the initial setup. There are other washers between arm and mounting too. They are put there so that when the car goes for its first full geo setup any adjustment just requires them putting the other side of the arm.

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Ah! Not the Guinness this time, just late night posting. The “lighter” thought was an over contracted sentence that would have read “also made from lighter material”. Alu or if that wouldn’t suffice; titanium. Even I read that and think OTT

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Since the body is off, you can get an idea if any major 'twist' is present by placing a straight edge (4x2 wood works) on top of the front box section, or spanning the front upper shock absorber chassis mountings, and a laser level (one that emits a straight line beam) on the rearmost crossmember and seeing how they line up. 

 

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I'm torn about whether to build a jig. I don't think it'd be wise bringing that much more weight onto the mezzanine level. Not that I wouldn't also be apprehensive about whether I could get a jig straight anyway. Will do strings and yep nice idea with the laser. If I can find someone localish with a proper jig I'll try get it on that too.

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9 hours ago, jonroberts said:

Since the body is off, you can get an idea if any major 'twist' is present by placing a straight edge (4x2 wood works) on top of the front box section, or spanning the front upper shock absorber chassis mountings, and a laser level (one that emits a straight line beam) on the rearmost crossmember and seeing how they line up. 

 

Don’t buy the 4x2 from Travis Perkins - it’s normally spiral 

some nice cheap box section steel - with exactly the application explained above

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Another usually handy bit representative of a straight edge is the sort of tubes fitted to fluorescent light fixtures. Long ago, when investigating suspected misalignment of my Elan's rear suspension I offered up a spare tube to the tire sidewall on each of the rear corners and damned if it didn't very effectively display the deranged toe at that end. Not terribly scientific but great for a quick evaluation of toe where the tube on sidewall can be made to reference against the body lines.  

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After a little research the cross line laser is the tricky bit, they're mad money.

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for setting front and rear toe two equal length pieces of wood or metal at either end of the car with fishing wire tied between them is cheapest way and used in a lot of motorsport so is definitely accurate enough. Rest the beams on axle stands and set the string so that the distances to wheel centers are the same at the front side to side and rear side to side then measure the toe as normal. I did this on my chassis before the body was fitted. Not ideal as without the weight of the body the ride heights are wrong but gives you an idea of twist and at least you can get the steering straight at the same time.

BTW in the photos of the turbo esprit above the bolt is definitely not sticking through the nyloc lock nut enough on the top picture and is pretty marginal on the other. Rather than fitting a longer bolt just remove 2 of the 3 washers nearest the nylock as they are doing nothing (IMO).

cheers

C43

 

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Just need to reiterate...the pics of my Turbo Esprit are of the suspension loosely assembled. They are not torqued up and the extra washers are for the full geo setup should they be needed. They will be removed on final setup.

 

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Hi George,

In 2017 I had a broken radius arm bolt, while driving the car. Trust me You don't want that.... topic:

So after I repaired it I decided to measure and set Toe in/out in the rear and in the front .....this topic

After setting Toe in the rear, I can confirm that on my car the number of washers is not the same right and left. I really had to measure and adjust both sides to get the settings right. so I don't think you have to expect that the esprit is perfectly symmetrical. Just use the washers , do a good measurement, take some time and it will be fine.

 

Geert

Edited by gvy
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@C43 have a tiny amount of experience with that method, helped someone set up their Formula Vee a few times that way. Will do my best to use any and every method, whatever it takes to get her handling properly. That's what it's all about after all.

@gvy Geert, great thread thanks for the link. Slow reply because I got sidetracked reading it! 

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