Swapping Mk1a and 1b suspension

[MartG]

Has anyone ever swapped the complete 1b suspension on to a 1a shell ( including the rear subframe/bracket thingies ) ?

I'm going to be doing this over the next couple of weeks, and am wondering if there are any hidden pitfalls - I know I'll have to drill an extra hole for the front topmount bolts.

Anything else ?

[LimeyMk1]

Rear brackets that hold the lower arms and tie rods are different, I believe the mounting holes are in different positions.

[cartledge_uk]

I will be attempted the reverse of you on Si's shell. 1a on a 1b.


The one hole you will have to drill, the car may sit higher as the 1a struts are shorter than the 1b.

The 1a rear subframe bracket things arn't interchangeable with the 1b, which is why they are so rare and sell for silly money if they are mint. you may be able to create a mount to mount the 1b thingie bracket too.

The problem could be hubs/driveshafts too, as the 1a driveshafts are differetn to the 1b, and you cant use a 1b shaft on a 1a hub, its a really subtle difference but it stops you from tightening the hub nut up as it locks against the hub and the shaft cant rotate

[Negativvv]

I will be attempted the reverse of you on Si's shell. 1a on a 1b.


The one hole you will have to drill, the car may sit higher as the 1a struts are shorter than the 1b.

The 1a rear subframe bracket things arn't interchangeable with the 1b, which is why they are so rare and sell for silly money if they are mint. you may be able to create a mount to mount the 1b thingie bracket too.

The problem could be hubs/driveshafts too, as the 1a driveshafts are differetn to the 1b, and you cant use a 1b shaft on a 1a hub, its a really subtle difference but it stops you from tightening the hub nut up as it locks against the hub and the shaft cant rotate

Oh....So in regards to what happened to me here http://www.imoc.co.uk/forums/viewtopic.php?t=81298
Im going to need a mk1a driveshaft?

[MartG]

So not a straight swap then - bu88er

Guess I've got a bit of measuring etc. do this weekend to figure out what to do - once I've washed all the mud off the underside ( I think Si must have driven it over a ploughed field at some point )

My main aim is to keep my existing Mk1b Koni adjustable dampers and springs ( and Superflex bushes ), and not to have to buy new dampers/springs etc.

[cartledge_uk]

So not a straight swap then - bu88er

Guess I've got a bit of measuring etc. do this weekend to figure out what to do - once I've washed all the mud off the underside ( I think Si must have driven it over a ploughed field at some point )

My main aim is to keep my existing Mk1b Koni adjustable dampers and springs ( and Superflex bushes ), and not to have to buy new dampers/springs etc.

That should work (unless you want to swap them for some slightly used kybs ) the car may sit a little higher, but only about an inch I think. you going to play with the geometry anyway so it shouldnt be a problem.

Use your struts, the 1b hubs and drive shafts, use the 1a subframe bracket, and it would work fine. Are the suspension arms different does anyone know as you could just swap the arm and only use the 1a rear rod thingie (im excelling in technical speak today)?

keep the 1a hubs and shafts to sell.

[MartG]

shafts to sell.

BenF has dibs on them already

[cartledge_uk]

shafts to sell.

BenF has dibs on them already

I remember having a drunken pm chat with him the other day now you say that

[MartG]

I think what I'll do is remove the complete 1a suspension, then measure everything and compare to the 1b dimensions. I'll try and document it all for Jinxy's "1a/1b differences" list for future reference

[cartledge_uk]

I think what I'll do is remove the complete 1a suspension, then measure everything and compare to the 1b dimensions. I'll try and document it all for Jinxy's "1a/1b differences" list for future reference

I did have a picture of the 2 shafts together but I have no idea where it is.#

Its a really subtle difference, on the hub end, one of them has this extra 1-2mm lip. its really hard to notice unless your looking at them side by side.

[Lauren]

It can be done.

For the front, just drill another hole in the strut top. POP.

for the rears you will notice that the bolt hole is bigger and the that the stub axle bracket is narrower. If you can do some basic welding you can easily weld a plate onto the strut holes to take up the slack.

[MartG]

Rear brackets that hold the lower arms and tie rods are different, I believe the mounting holes are in different positions.

Removed rear right suspension from the 1a this morning, including the subframe bracket, and have compared the bracket mounting holes between the 1a and the 1b shell I have.

Good news is that the 3 vertical bolt holes are in the same position, so no problems there ( especially as they locate onto captive nuts inside the chassis member ).

Bad news is that the horizontal bolt is in a different place. This isn't as much of an issue though, as it goes right through the chassis member and fixes to an external captive nut in the engine bay. All that's needed is to drill a new hole in the correct position

This means I can transfer the entire 1b suspension as a unit onto the 1a shell

[alfiembra]

Mart I think you might be wrong with the sub frame bolt holes, did you compare them bracket to bracket or did you try the 1b bracket on the car. I've tried this and the 1b bracket clashes with the rear ARB mounting bracket, at least it did on the drivers side on mine. Would like to be proved wrong as it would be a huge benefit to 1a owners to be able to use 1b brackets when theirs eventually disintegrate but I'm fairly sure I'm not.



I eventually got replacements from a breakers in the USA got a good contact there if anyone else is looking for some.

Alan

[MartG]

Alan

I measured the mounting holes on the chassis, not the brackets, but didn't check the ARB mount I'll check again with the brackets once i've finished taking the engine out.

[MartG]

Right, here we go....

The pic below shows the rear suspension bracket mounting area of my 1a. The 1a bracket attaches using bolt holes 1, 2, 3, and 7. The ARB fixes to holes 4 and 5 ( with a drain hole between them normally blocked by the ARB bush ), and 6 is one of the mounting holes for the exhaust heat shield.

It is difficult to see in this pic, but the crossmember actually curves slightly forwards toward its outer ends.



Here we have a pic of the same area of my 1b - an important difference is that the front face of the crossmember curves forwards exactly the same as the 1a one, but the rear face doesn't - it runs straight across.
The holes all have the same number as on the 1a pic above, but note that hole 3 is missing entirely, hole 4 is now used for the suspension bracket rather than the forward ARB bolt, and there is a new hole ( 8 ) for the aft ARB bolt, and as the drain hole is no longer covered by the ARB bush a blanking plug is fitted. Hole 7 is also further inboard and lower down.



Conclusions - to use the 1b rear suspension on the 1a chassis needs a new aft ARB mount bolthole to be drilled, a new transverse hole ( 7 ) to be drilled and spacing washers use to fill the gap where the 1a crossmember curves forwards ( and the 1a captive nut to be ground off and replaced )

Simple innit

[alfiembra]

Good Photo's Mart, just for anyone else following this thread if they are considering doing this mod you will also need the 1b track control arms too.

Also is it fair to assume there might be a slight difference in length between the 1a and 1b ARB since the mounting brackets are in different locations, also believe the 1b ARB is slightly larger in dia, can anyone confirm?.

Alan

[MartG]

Correct Alan

1a rear ARB is about 8mm thick, whereas the 1b one is about 13mm ( both give or take a little rust ), and the 'arm' part of the 1b bar is longer. Due to the longer arm the 1b bar may not be much stiffer than the 1a one due to the added leverage.

Pic below shows the two types together, 1b at the top