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  #1  
Old 30th March 2011, 10:56 PM
Ashtonr Ashtonr is offline
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Default Word of Warning Rear Toe in

Well Just spent this evening correcting the alignment of my rear hubs, dont know what made me think of it probably a recent post but I thought I would double check the rear toe in which I assume should be 0 degrees well the OS was + or - 1mm over a meter but the NS was well out not sure how it happened but I had fully welded the brakets and forgoten about them. Resolution was to remove one of the brakets and pack it out slightly.
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Old 31st March 2011, 08:11 AM
Eternal Eternal is offline
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Ahh yes that was me who also has that problem. i have looked at the dummy shuck and thats not the problem so will strip it all down this weekend and see whats up.
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  #3  
Old 31st March 2011, 08:35 AM
snapper snapper is offline
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Do you mean that you cut off the mounting bracket, packed and rewelded?
The Lightning rod boys used to pack out the hub carrier with a washer or 2 to get the wheels square.
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Old 31st March 2011, 10:30 AM
Ashtonr Ashtonr is offline
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Yes cut off the mounting braket and packed out 2 mm. I also notice that there is a fair amount of movement on the actual carrier bushes so after this excercise I can still move the hub out of alignment in both directions. I was hoping if I align the upright proir to fully tightening all the bolts it would actually want to stay straight anyway.
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  #5  
Old 31st March 2011, 10:44 AM
fabbyglass
 
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This is why you have to work from the centre line and not just put the brackets on the tubes. You would be better to make a simple jig that sets the correct alignment of the brackets then bolt brackets to this then put the tubes on.
if you have one side toeing in or out it will cock the whole thing up and will handle like a sack of spuds on a skateboard.

tack a tube on the centre line, use a scriber to scribe centre line and always work from that
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  #6  
Old 31st March 2011, 10:51 AM
fabbyglass
 
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Quote:
Originally Posted by Eternal View Post
Ahh yes that was me who also has that problem. i have looked at the dummy shuck and thats not the problem so will strip it all down this weekend and see whats up.
If a piece of tube used as a temp shock is pushing things on the piss then a shock absorber will be worse as it has a springy thing with loads pressure behind it....must some something else a tad wonky?....work back from the centre line of the car as well as check the track front to back...you will be surprised how much things can be different from one side to the other.
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Old 31st March 2011, 11:01 AM
Ashtonr Ashtonr is offline
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I had worked from a center line maybe something moved when I fully welded everything up but anyway I hadn't checked very well after welding as it was out. The welding a tube to the centre line is a good call pity I didnt think of it at the time.
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  #8  
Old 31st March 2011, 11:08 AM
fabbyglass
 
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Quote:
Originally Posted by Ashtonr View Post
I had worked from a center line maybe something moved when I fully welded everything up but anyway I hadn't checked very well after welding as it was out. The welding a tube to the centre line is a good call pity I didnt think of it at the time.
Tack a piece inside so it sits at same level, that way you can measure without distorting tape or ideally a steel rule as tapes tell lies...mind you so can steel rules come to that

Make sure you check the track front to back on both sides of the car as any difference will mean weird handling, I have seen a locost with as much as an inch of difference in track
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  #9  
Old 31st March 2011, 11:24 AM
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Talonmotorsport Talonmotorsport is offline
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Don't forget that the face of the rear upright is determined by the bottom rail of the suspension cage, the bottom wishbone and the rear upright it's self. If all these things are even 0.5-1mm out any where the worse case you could end up being 3mm out very easily. With the best will in the world the rear suspension is made from fabricated parts welded together not CNC made and assembled production components.
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  #10  
Old 31st March 2011, 11:35 AM
trick-kit trick-kit is offline
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Quote:
Originally Posted by Talonmotorsport View Post
Don't forget that the face of the rear upright is determined by the bottom rail of the suspension cage, the bottom wishbone and the rear upright it's self. If all these things are even 0.5-1mm out any where the worse case you could end up being 3mm out very easily. With the best will in the world the rear suspension is made from fabricated parts welded together not CNC made and assembled production components.
It's called accumalative error, if you start with the basics, each item will have a tolerence on dimensions, then if it is a welded component, each weld will have a tolerence too, once you start to add fabricated items together then all these tolerances can quickly become a problem if not kept in check.

I appreciate that this is a home built car, so keep the tolerances in the real world, it would be impossible to work to 0.1mm for example.

The way round it would be to have a jig for the suspension pick up points front and rear firmly screwed to the table and make sure that these are in alignment, then build the chassis around these. After all, the purpose of the chassis is to join the important parts (suspension etc) together.
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