serious weight saving.

Definitely unsprung weight and also moment of inertia to be considered, smallest brakes that are capable of the job, smallest wheels that`ll fit over those brakes.

The thing I found with cutting weight from the track car was, it became very addictive. While a couple of bits of trim here and there might not make a difference, add things up and it doesn`t take long to shift 30 plus kgs and more just using time and common sense.

Whilst many of us may not reap, or measure the true advantage, there are also benefits to the car, brakes, tyres, suspension, if its lighter its easier to accelerate, brake and change direction.

 

OK here's one if you were to cut out the the spare wheel well and replace with sheet are you weakening the car?
under these two situations; with and with out weld in 6 point roll cage.

from what i have learnt removing it does remove structural stiffness of the rear, however this isn't the case when a cage is involved, is that fully true that there is no structural difference when removed in the presence of a cage? because i would have thought that you would still loose some level of structural integrity.

 

(on a Mk1) the only point where it cold be structural is where it joins the rear lateral box section between the wheels. Otherwise it is just a metal bucket hanging in a tin floor, flexing about and adding weight (and storage space).

 

well that settles it, extra road and exhaust noise less extra weight rivet and sealed ally plate or welded steel plate what's your preference.

 

Seal whatever plate you use with some sound deadener or it'll rattle like mad.

In keeping with the thread, technically, you should use the lightest material possible. I suspect this is a thickish piece of carbon composite

 

checked online... from what i saw ally plate.. 20 carboncomp... 120.. haha

 

I think the whole sunroof cassette in my mk2 must weigh alot, would a piece of Perspex bonded and bolted to roof be up to the job?

 

Ali for me everytime. Light cheap easily replaced. Easy to cut, made for pop rivets. Rattling? never noticed, mind I have never run one on the road. Carbon, or kevlar? horrible to work with

 

I removed the cartridge from my sunroof and bolted in the glass part of the sunroof in. I did this as I was worried about using plastic and it warping out of shape with heat from the sun. Has anyone done this and had any problems with the plastic bowing? I'd like to remove my glass roof to save weight in my car.

Another thing to think of on the weight saving is choosing the right seat. some cheaper race seats are metal framed and although lighter than the original seats you can save more weight using a shell race seat. They are more expensive though

 

problem with plastic, if clear is that you will always have the sun on you... the mk2 gti at my work has a riveted ally cut out with some sealer on the roof.

 

I was thinking ally, my sunroof is steel not glass, only problem with ally us that it doesn't weather that well. Dare I mention a carbon wrap on it, just to stop oxidisation of course!

 

Ali plate. Thats how mine is done, but have seen guys get rid of the sunroof cassette and the bolt and seal in the original panel, factory looking from the outside and the hefty sunroof windings gone.

While your thinking about lightening you could put some thought into redistributing some of the weight too, getting more stuff between the front and rear wheels, in particluar behind the front wheels.

Battery in the rear footwell - down and back 6kgs to be saved going to a small race or lawn mower/golf cart battery

Washer bottle relocated - bag type off ebay is only about 10 delivered

Front bumper butchered - saved 1kg and improved air flow to the rad and oil cooler

Some of the most obvious ones.

 

Do you know if this mod would be an issue if done to a road legal car? i'm thinking from an mot point of view?

 

nah, you'll be fine i'm sure? i've seen a few road legals, as long as it's sealed well enough.
if in doubt talk to the local station?

Lew
'

 

I cut out my roof (Mk2) including entire sunroof leaving 60mm at the sides, about 100mm at the front and rear and the rear seat support, came to 21kg using dodgy bathroom scales method
Carbon panel going on is 3kg IIRC.

Alloy sunroof panel on old car was sealed and riveted, did the job well.

Looking to do plastic screen, lightweight bonnet/bootlid and perspex etc.

 

The whole sunroof mech does have a fair bit of weight to it and is a good thing to get rid of but after chopping my wheel well out I wasnt convinced it was worth it, the underseal probably weighs more than the metal. I did leave a flared lip when I chopped it out just in-case there was flex if I chopped it flush with the floor. Biggest surprise was the underseal in the rear arches, crazy thick compared to most of the areas underneath the car but took an age to get rid of it.

 

Any part of a full structural member must be fully seam welded or its an MOT fail

 

Not if fully seam welded

Here`s my Mk1 with 2mm sheet steel which I thought it would negate bracing...............





BUT I noted flex in the 2mm sheet (anything less is frighteningly wobbly) and considered it would allow movement and discussing with a very knowledgeable MOT man he recommended a simple brace which I added as below so if its weight saving then in my view its not worth it - I see it alongside the cutting back of the rear valence as less drag

 

I disagree it could be flexing, because it is not attached to anything, as mentioned earlier:

 

If you had added structural forms into the flat piece of steel you welded into your floor to replace the spare wheel well it probably wouldn't have flexed. Although without the sheet metal working equipment needed to do this your square brace is easier and as good at stopping the floor from flexing. Although probably heavier.