I am abit concerned: advice please
Discussion
So, my Series one rebuild is progressing albeit slowly. I have the rear suspension all rebuilt, I have the diff in, almost. I have got past the odd drive shaft issue (I just bought new ones) and I have just ordered my new wheels and they will be with me by Thursday, but I have a little problem. I have scratched my head about it but I am stumped.
You see, when I fitted the rear uprights and the new shocks and springs, the top of the rear-most shocks didin't "quite" line up with the top bracket:
I kind of brushed past this issue, because, well, with a bit of jiggling it goes in, but I did think that I would probably have to think about why this wasn't right at some stage. Its the same on both sides.
Then, when I finally got the diff sorted and tried to fit it, the top mount ended up about 3/8" too low down. So now I am beinging to wonder what is going on with the dimensions of the rear cage.
I thought this was possibly because the curve in the chassis tube carrying the bottom diff mounts was too severe, thereby effectively lowering the mounts by about 3/8", but I think this is unlikely.
Then, whilst scratching my head about these two problems I noticed that the drive flange on the uprights are out of line with the flange on the diff. The flange on the upright is behind the diff so that the drive shaft effectively points backwards by a good few degrees.
Now I know that these are hand made cars, but this just doen't seem right.
The chassis is "new" or was in 2000. Its apparently an 1800S chassis according to the paperwork and I dont think there should make any difference in the diff cage and suspension set up.
The only thing I can think of that might explain the issue with the shocks and possibly the drive alignment, is the use of top hat poly bushes. If the original bushes were narrower, or had no lip, then this might effectively add up to the displacement of the shocks and drive shaft, but obviously not the diff. So, before I tear my hair out, I throw it open to the expert panal............WTF is going on with my car?
You see, when I fitted the rear uprights and the new shocks and springs, the top of the rear-most shocks didin't "quite" line up with the top bracket:
I kind of brushed past this issue, because, well, with a bit of jiggling it goes in, but I did think that I would probably have to think about why this wasn't right at some stage. Its the same on both sides.
Then, when I finally got the diff sorted and tried to fit it, the top mount ended up about 3/8" too low down. So now I am beinging to wonder what is going on with the dimensions of the rear cage.
I thought this was possibly because the curve in the chassis tube carrying the bottom diff mounts was too severe, thereby effectively lowering the mounts by about 3/8", but I think this is unlikely.
Then, whilst scratching my head about these two problems I noticed that the drive flange on the uprights are out of line with the flange on the diff. The flange on the upright is behind the diff so that the drive shaft effectively points backwards by a good few degrees.
Now I know that these are hand made cars, but this just doen't seem right.
The chassis is "new" or was in 2000. Its apparently an 1800S chassis according to the paperwork and I dont think there should make any difference in the diff cage and suspension set up.
The only thing I can think of that might explain the issue with the shocks and possibly the drive alignment, is the use of top hat poly bushes. If the original bushes were narrower, or had no lip, then this might effectively add up to the displacement of the shocks and drive shaft, but obviously not the diff. So, before I tear my hair out, I throw it open to the expert panal............WTF is going on with my car?
Edited by Astacus on Sunday 22 July 12:14
Chances are if you are using new bits from different sources something will be slightly out of tolerance. Driveshafts do both angle slightly rearward in bias when viewed from above. If your new chassis was purchased in a different place to your new wishbones etc then very often things need a jiggle about to get it all to fit. This can be a minor tweak to a wholesale tweaking of chassis brackets to get it to work..At the end of the day it isn't too critical because everything is adjustable to bring the cars track into alignment..
Best way to build is to hang your upright from the top brackets after checking their dimensions relative to each other then loosely assmble rear end and lower gubbins with spacer washesr accordingly. If you are confident that camber, caster and wheelbase are all equal then use a rosejointed shocker with angled cones to take out any differences in angles!!
I have seen some chassis a mile out but everything adjusts out to return the driveline to square.
N.
Are they new uprights?
have you re-used the original lower pivot rods?
N
Best way to build is to hang your upright from the top brackets after checking their dimensions relative to each other then loosely assmble rear end and lower gubbins with spacer washesr accordingly. If you are confident that camber, caster and wheelbase are all equal then use a rosejointed shocker with angled cones to take out any differences in angles!!
I have seen some chassis a mile out but everything adjusts out to return the driveline to square.
N.
Are they new uprights?
have you re-used the original lower pivot rods?
N
Edited by heightswitch on Sunday 22 July 19:39
heightswitch said:
Chances are if you are using new bits from different sources something will be slightly out of tolerance. Driveshafts do both angle slightly rearward in bias when viewed from above. If your new chassis was purchased in a different place to your new wishbones etc then very often things need a jiggle about to get it all to fit. This can be a minor tweak to a wholesale tweaking of chassis brackets to get it to work..At the end of the day it isn't too critical because everything is adjustable to bring the cars track into alignment..
Best way to build is to hang your upright from the top brackets after checking their dimensions relative to each other then loosely assmble rear end and lower gubbins with spacer washesr accordingly. If you are confident that camber, caster and wheelbase are all equal then use a rosejointed shocker with angled cones to take out any differences in angles!!
I have seen some chassis a mile out but everything adjusts out to return the driveline to square.
N.
Are they new uprights?
have you re-used the original lower pivot rods?
N
Hi Neil,Best way to build is to hang your upright from the top brackets after checking their dimensions relative to each other then loosely assmble rear end and lower gubbins with spacer washesr accordingly. If you are confident that camber, caster and wheelbase are all equal then use a rosejointed shocker with angled cones to take out any differences in angles!!
I have seen some chassis a mile out but everything adjusts out to return the driveline to square.
N.
Are they new uprights?
have you re-used the original lower pivot rods?
N
Edited by heightswitch on Sunday 22 July 19:39
Thanks for the comment. Re the uprights, Everything is new except the casting. Lower pivots are EN16 units from DGs so they should be correct.
My feeling is that there are some errors in the construction of the chassis around the cage. The upper mounts are essentially fixed by the dimensions of the top rails of the diff cage. They cannot move further apart to compensate. This means the lower dimensions have to be altered. However, there are no spacers between the casting and either the track arm or the bottom shock mount, so nothing to adjust there. The only solutions I can see are either (a) reduce or remove the lips on the bushing on the pivot arm (ie return to normal bushes and maybe cut them down a fraction). (b) move the mountings on the lower arm forward, (but this would alter the castor) or (c) maybe buy new wishbones for the rear, from the same source as the chassis, in the hope that the issues cancel out.
As for the issue of the top diff mount, I have made up some alloy spacers for this, and well have to see what happens.
You can often find that if your wishbones are from a different source to the chassis they will not fit. Top chassis rails tend to be reasonable static..Its the wishbone jigs that tend to differ. My advice to you is to build the top and upright. Use some plumb lines to check your wheelbase then tweak your inner lower chassis brackets to bring into alignment. You can do this with studding and nuts to pull and push the brackets into the alignment you require..at the end of the day a few mm on the inner bracket multioplies quite a lot at the outer end of the wishbone.
N.
N.
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