Rear toe in woes

[Eternal]

Right then! after getting all worked up about the posibilty that my rear diff frame could be all wrong. I took it upon myself to remove all the wishbones and bits to measure it all up.
Well! it turns out that its ok... as in i get the same measurements for both sides. I then installed the lower rear wishbone on the side that was giving me problems to find that its seems to be sitting ok. Now i have reinstalled the upright from the other side just to see if that was causing the problems and it looks like the issue has resolved itself. Very very strange. Im going to put the wheels back on and put the upright onto the otherside and see if that gives me rear toe out on the other side.

[Eternal]

Ok! the good and the bad news!

The good news is i installed the drivers side rear wheel using the good sides upright and........ its now fine!

Bad news =( installed the original drivers side rear upright on the opposite side and i now have toe out! lol.

Soooooooooo turns out that i have a suspect upright. This i guess is good news as it means my brackets are all ok and the chassis is sweet as a nut!

[Bonzo]

I have been following this thread with great interest.

Have refrained from comment because, to quote Austin Powers " Suspension aint my bag baby "

Having read your progress, it certainly seems like the problem may lie with an upright.

If you are up to stripping them again, might be worth puting them on a flat, level surface & having a good measure up.

You may find that simply shimming the hub carriers you will able to get the settings required.

I hate it when I come accross problems but am really pleased when I manage to solve them.

Hope you get it sorted soon

[Enoch]

I had to shim one of my uprights, it only needed about 35 thou or something like that but it was toeing in without that. I figured that for a home build that was not a bad amount of cumulative error. The drivers side was very slightly out but it was not enough to worry about, in my opinion. The way I measured mine was to use the bottom side rails as a reference, I used 1.5 metre straight edges clamped to the hubs when they were mounted to the uprights. I measured the distance between the straight edges next to the hubs, or as close as I could get and then at the other end of the straight edges, this showed the two hubs to be at exactly perpendicular to each other. I then measured from the rails to the straight edges to make sure the wheels were aligned to the chassis, otherwise I may have got "crabbing". I read somewhere that a small amount of toe in on the rears increases stability but have not been able to verify if that is true or not. Anybody got any comment?

[Wynand]

Just a note of caution; when using a spirit level, make sure it is true - there is a simple test; draw a level line on wall, turn level around (left to right) and see if it still on the line drawn. Same with vertical check.
Recently I had to check 6 levels at the hardware store before finding one that was accurate.
When measuring cambers, etc I prefer to use a master "Promac" level that's adjustable.

[MikeB]

As above I'd try and get the measure relative to the side rails as the rear chassis might not be true. I've welded my rear suspension mounts on but did check by assembling the upright, clamping the straight edge to the hub and seeing if it was roughly parallel with the side of the chassis, i had to swap the uprights over it then seemed relatively true, aim to shim it if necessary.

Very light rear toe-in on a road car will aid straight line stability and is what I would go for. Toe out at the rear will make it seems a little twitchy but should turn in really well.
I'm setting up a caterham superlight this year we have just had our first race at Oulton at the weekend, hence getting the hang of setting up these things (for the track not the road though)

We are investing in some shims to adjust rear toe in/out so will play with it at Snetterton