Base rear beam compatibility

[ArthurH 5]

The background to my question is we have bought a base model shell to replace that of our race 1.60GTI.  It seems less wasteful than to use a 'real' GTis for this purpose.   I am preparing the new shell while we still race the existing GTI in the 2024 season, so I don't yet have the GTI running gear available to me for checking dimensions, e.g., wheel clearances.

The car we have bought is a '95 Inca 1.8 diesel, but not turbo, so unless anyone wants to correct me, I believe it is in terms of suspension, a 'base' model.

 

I am aware the base model beams have different torsion and anti roll bars, but other than that are they dimensionally the same as a 1.6 GTI, e.g., the mounting holes in the shell?  Is the main tube interchangeable, i,e, worth me keeping as a spare?

Is the overall track of the base rear beam the same?  Specifically when measured from the outside (wheel mating) faces of the brake drums?

 

 

[Tom Fenton 1,526]

The beam tube will interchange, It is different in that the diameter in the centre part is smaller. Would you notice the difference from the drivers seat, I am not sure. The trailing arms are different geometry. Track width you would need to check. The rear drums are not the same as GTI.

Biggest issue you will need to sort is the rear wheel arches for clearance. The GTI arch is quite different.

[ArthurH 5]

Thanks (as always) for your quick reply Tom.

Although the trailing arms are a different geometry, the holes in the boot floor are all in the same place?  I was aware the drums were wider on the GTI but wasn't sure if that increased the overall track width or whether the wider drum went 'inwards, if that were at all possible.

The rear wheel arch clearances are the very thing I want to tackle next and didn't want to use the 'base' beam as a reference point if it were to give me a false datum so to speak.

 

The Inca already had 185/60x14 on the back (nominally the same sizes as the Toyo control tyres on which we race) and there is currently 10mm clearance between the tyre and the boot side of the inner wing, but perhaps that is with the wheels on droop and the issue will be when the tyre is up inside the wheel well.

To save repeating information, would you know if the necessary mods to the base rear wheel wells are already documented on this forum?

[jord294 87]

There is a difference to the rubber bushes on a base model tube compared to gti. But if you race, then acetal bushes are a great option. 

 

Holes in boot floor exactly the same

 

 

Edited April 16 by jord294

[ArthurH 5]

Thank you, that does help.  We have previously used bushes from BakerBM and found them to be pretty good.

I think my next step is to measure from drum face to drum face on both the base and the GTI and find the difference, I could then space one of the race wheels on the base beam to the same track as the GTI

 

 

 

 

[Tom Fenton 1,526]

The easiest way to do the arches is remove the rear plastic arch on the gti and make templates of the gti shell arch profile, then do the same to the base model. 

[ArthurH 5]

Sounds like a plan!

Can I infer from this that all of the additional clearance is required on the outside of the inner wing, as opposed to any being required on the boot side of the inner wing?

[welshpug 1,623]

Exactly That.

 

The only difference in the wheel tub is a slight bit where the outer arch is higher.

[Tom Fenton 1,526]

 

https://www.instagram.com/reel/C5x5OXYII72/?igsh=d2hkM2Z5cTZsOXJ3

I came across this by chance the other day. They say a picture says a thousand words etc so a video even better. Hopefully the link works.

[ArthurH 5]

It could hardly be more appropriate!  Thanks Tom