I need a couple of body measurement.

I'm planning a future build and are currently trying to deside what parts to use for the front and rear suspension (this will be a scratchbuild)

But I need to know the "maximum" width of the outside of the tires front and rear.

In other words: What is the "maximum" measurement of the outside-to-outside rubber that will fit under the body of a Mk1 body? Both front, to allow for some steering, and rear, it could be interesting to know bith with and without Gulf arches.

I need this to determine if I can use std Audi driveshafts and to start looking at the front wishbone design and to begin thinking about proper offset for the wheels :)

Or. Trackwidth and wheel width including offset that works fine could also do the job :)
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Front and rear track varies depending on which GT40 you're aiming for. Outside width depends on what tyres you're planning on. Nominally however the outside body width is 70 inches, which is at the front/rear arches knock a bit off that and you have your maximum track+tyre width. Same goes for 'gulf' arches etc, the widest point will be the arches so knock an inch or so off and that is your answer.

Personally I was looking to lift the entire front and rear subframe assemblies out of an RX-8, transpose the suspension mount-points to my chassis and use pushrods to activate the suspension. Not original, slightly wider than ideal but far better design and easier than making my own.
Thanks! :) Althou, since the body should be the same, the widest point over the tyres should be somewhat the same on all models. And if you have the wheel offset, wheel width and track it's easy to calculate that specific cars measurement between the disc's face's and from there make a judgement on where I can position my setup :)

I'm already doing a custom front suspension for my -76 Opel Kadett so I'm not afraid to do a custom setup, might take a bit more time but it might be worth it too ;)

Do I remember correctly if I state that the Gulf was two inches wider in the rear on each side than the "stock" GT40?


New Member
Original track width was 56", hub face to hub face so you can calculate from there.
There are more than a few widths for the rear on the gulf bodies, and some go as wide as 80" to fit the rubber used.
I am using 15 X10 wheels in front with 5" backspace and they just fit inside the body.
Rears are 15 X 14 with a 5" backspace and they fit comfortably under the bodywork.
There was a recent thread on wide bodywork here on the forum so a quick search may get you some good examples of various widths and how they look.
I usually work from the outside in, figure my desired or available width with bodywork limitations, and build accordingly, but if you go with the original track width and get the correct wheel dimensions things should work out OK.
I've copy pasted the below from some posts over the years - might help some


Fred W B

there are 3 widths of arches
the original cars with wire wheels are 70" across
the ones in the photo are 72" across like the CAV and GTD,
then there is the Gulf arches that are 78" across.

Wheelbase 95in. 2413mm
Track Front 55in. 1397mm
Rear 55in. 1397mm
Overall Dimensions
Length 168in. 4265mm
Width 70in 1778mm
Height 40.5in 1028.7mm
Miscellaneous Heights
Base of Windscreen 28.25in 717mm
Top of Windscreen 39.2in 970.3mm
Top of Steering Wheel 31.35in 796.3mm
Minimum Ground Clearance 4in 101.6mm

original MK111 figures:
Wheelbase: 2421mm
Front track: 1402mm
Rear track: 1402mm
Front tyres: 5.50 x 15 on a 6 1/2 inch rim
Rear tyres: 7.00 x 15 on an 8 1/2 inch rim
Overall vehicle width: 1778mm
Great info Phil and Fred! Thanks!

That should give me enough to calculate with for the coming week or two ;)

Phil, those 15x10's, with 5" backspace, I guess you're running zero offset on them?


New Member
Essentially yes, and they just fit inside the bodywork.
The rears fit with a bit more room, but the inside of the arch tapers inward from the edge so that although there is quite a span across the body, I still needed clearance for bump in the suspension.
Regrettably I recently crashed this computer and it had lots of photos of the setup I used that were lost, otherwise I would have gladly shared them.
My build thread has some photos, but I don't know how to paste the link here
I will try to get some photos and see if I can post them.
I've read your build thread (along with a whole lot more over the years)

Here's the link: http://www.gt40s.com/forum/gt40-build-logs/17261-my-scratch-built-project.html

An impressive build :) Front suspension looks to have a nice geometry. Most of the pic's I've seen, and some of the blueprints, have a setup very much like the original 40 with the rear mounts of the wishbone further out than the front, unlike yours where they are more "striaght" if you understand what I mean? In my mind a setup like yours should only move the tire up and down, while a slightly twisted one would move it a little bit towards the rear of the car when the suspension travels! It might not matter with the small amounts of travel on a 40 but still :)


New Member

Thanks for the compliments. I used an early design for the front suspension that, as you said, has really good geometry. I nearly eliminated the bump steer and it toes in only when you remove the shock and let the wishbones go beyond travel limits.
I have re-designed the front end and it has the tapered upper and lower mounts as you described, and yes the suspension does rotate rearward slightly due to the angle. Also as adjustments are made such as changing the caster to positive, the camber goes to positive as I used a method of shimming the upper wishbone fore and aft to change caster. Changing the camber to negative increases the caster in the positive direction....it sounds complicated but were not talking about making large adjustments and adjustments can be made to compensate for the added or lesser amount in the other specs.
The other benefit is much more footwell room, and the chassis is easier to panel.
I am so far along on my chassis that I decided to continue with the existing setup, just too much work at this point to change the whole front end. The next chassis will have that setup.
By the way my rear deck measures 80" across the flares, but as I mentioned my previous post there is an inner panel in the wheel arch that would rub if the tires were any wider.
Not trying to hijack your thread but if you need any actual dimensions just let me know.
Thanks but I think I'll manage for now ;)

I'm still in a very early stage of this "project" if it even can be called that at this point! I'm mainly researching wich parts to use, where to buy a body, suspension design, wheel dimensions and so on :)

From what I've found so far, the footwell room is tight with both tapered arms and with straight. But If I can "live" with something in the line of 17x8 with 10 to 30mm offset up front I could prob widen the whole front an inch or two wich wouldn't hurt :)

A car as light as the GT40 shouldn't need much more rubber than 225's up front for most of the driving. I have a -71 Manta that's heavier than the GT up front with brand new 205's and if you drive that one when it rains, you'd do best to avoid the puddles :)