Another Exmo 🥱

[LewisH]

So after trying to fit the rear wings back I found that no matter how I tried, I couldn't get them to sit flush and so decided to bite the bullet and trim them back as they should be, as per the video from sparepart. Pics below of how they turned out, I bought some 1mm carbon fibre sheet and also used that to cover the old holes on the side.

[LewisH]

I also replaced the exhaust as the old RH silencer had sharp edges and was v loud.

[LewisH]

Some quickly knocked up infill brackets for the nose cone. 

[LewisH]

Ready for IVA...or so i thought!

[Sparepart]

On 5/13/2021 at 2:53 PM, LewisH said:

I also replaced the exhaust as the old RH silencer had sharp edges and was v loud.

Well done with the rear wheel arches, it was a big bullet to bite. From where did you source the silencer ? how does it sound ? it looks like it can be repacked ? Also what a cliffhanger of a statement "....or so I thought"   .... when is the next installment? ... on the edge of seat.

Edited May 15, 2021 by Sparepart
Add some words

[LewisH]

Sorry, I had intended to write up the IVA details when I got home but I was so knackered, had a beer and conked out!

The silencer is from a company called Blue Flame Exhausts. It sounds great, has a rolled end and no sharp edges. Good company to deal with, would recommend. 

[LewisH]

So the IVA was a fail unfortunately, but I knew it would as I didn't quite manage to get everything done in time. Tried to move the date on the Monday (test was booked for the Thursday) but the lady told me that I would have to pay the whole fee again. So, Thursday it was.

All in all I was quite impressed by the two guys that did the test, a good laugh and it was obvious that they actually wanted to help me rather than hinder. I even ran out of fuel at one point (didn't realise that you were supposed to have a full tank fir the test), after putting a can of fuel in, the examiner then had to suck it through as the line wasn't primed. Pretty sure he didn't have to do that. 

So the main points of fail, apart from a few sharp edges were;

- steering not self centering. 

- brake pedal box assembly flexing.

- rear brakes locking before fronts.

- nose cone indicators not extending far enough out from nose cone. 

- rear fog lamp not marked with E, B or F.

- front suspension springs fouling against chassis turret.

- wheel guards not covering full width of wheel.

[LewisH]

I know what I need to do for all the points, apart from the steering self centering. Having looked on the forum for the phrase, it seems that it is a common issue, but not clear as to how it is overcome on the Exmo. 

I don't see that I can increase the camber without fairly major chassis alterations to the top strut mounts. I already have toe in, a bit too much if anything. Not really sure what I can do here, does anyone have any other suggestions or experiences with this on the Exmo? I also have a tie bar setup rather than ARB, but I'm not confident that this has been optimised for the setup.

[richyb66]

Self centreing is more dependent on caster than camber. You should be able to adjust the caster by lengthening or shortening the tie bar.

[Sparepart]

As you have probably found in your search, I asked this question not that long ago, in the thread:-

https://www.rhocar.org/index.php?/forums/topic/49176-exmo-caster-adjustment

There is a rather american voiced, but well explained Youtube  about self centering:-

https://www.youtube.com/watch?v=wLbs8kBXgrw

On the Exmo, we can't push the bottom of the struts forward too far because the springs will foul on the leading side of the "n" shaped mounting outrigger. If the "front suspension springs fouling against chassis turret." means that they are fouling the trailing edge, then you have some hope because pushing the strut bottom forward might cure both problems. On my Exmo there is no self centering, however it passed the old SVA test without any mention. I want to fix it because it makes steering feel more like using a rudder on a boat, requiring constant attention to keep going in a straight line.

Self centering can also be affected by something called the "King Pin Inclination", however we cant adjust that becuse it is set in the casting of the stub axle at the strut bottom. A property called camber we can in theory adjust by increasing/decreasing the distance between the either the strut tops or bottoms. A certain amount of negative or positive (I am not sure which?) camber can help with self centering. I think its negative camber where the tops of the wheels are closer than the bottoms. This means that when the steering is turned from straight there is a slight lifting of the car involved. Thus when the steering wheel is let go the energy is released by the wheels returning to straight and the car dropping slightly. Problems with this is that the steering becomes "heavier" and the tyres will wear on one side......I am toying (just toying) with the idea of being able to adjust the camber by being able to slide the top mounts in a short groove rather than the current fixed hole....I'll need to take measurement to see how much that could change the camber by, and the safety aspects etc. etc.

Edited May 15, 2021 by Sparepart
Add info

[LewisH]

Thanks for the info.

I'll have a play around with tie-bar setup and see what difference it makes. Difficult for me to test this though considering it isn't road legal. Might have to be a quick run around the block and hope I don't meet the rozzers.

The front suspension is fouling on both front and back of the n shaped outrigger, so I am going to have to "manipulate" and create more room. I'll focus on bending the front out so that I have more room to push the strut bottom forward. 

[nelmo]

How have you checked the toe-in? You can't do it by eye. I thought mine was straight, had someone on here with a home laser kit check it and it was miles out - far too much toe-in. Corrected it and got loads of self-centering... 

[alanrichey]

Same here.   I started to see excessive wear on the outside of the front tyres so had it checked at the local garage.  Like you I had too much toe-in.   Now corrected, and although my self centering was OK before, now it is quite aggressive and I have to keep a lot of pressure on the steering wheel during turns.  But now extremely stable in a straight line.   Just have to keep an eye on the tyre wear to make sure it is fixed.

[Sparepart]

This is great news, here I have been messing about with all the physics and mechanics of caster and camber etc and all the time the solution is getting toe in correct. This is the most easily adjusted of all the steering geometry variables. What i don't know is what is the correcy value ?? Two above posts say "far too much toe in" well the obvious next question is  ... what was the correct amount of toe in ?.  The Haynes manual for the Sierra Saloon/Hatchback/Estate says that the optimum should be just 1 mm, with a minimum of 0.5 mm and a maximum of 4.5 tolerable. Can you remember what value was used on your vehicles ?

[alanrichey]

There is no exact answer but the general concensus on the forum has always been that you can't go far wrong with parallel with maybe a slight bias to toe-in if necessary.

I was always used to measuring toe-in in degrees, but like the manual, my garage quoted it in mms.   Mine was a 10mm out, whatever that means, now reduced to zero.