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Fitting a Trackday cage to an imperial chassis. anyone any pics or guides or anyone near london have one I can take a good look?


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I've fitted a cage, I've actually had three different ones on my imperial chassis car. I now have a tall Safety Devices cage.

It would take me an age to type out 'how to' but happy to talk you through how I did it. If you PM me your contact details and a time when its convenient I'll give you a call.



PS - I think its best to ease off the interior side panels by drilling out a few rivets, so you can find the threaded bosses in the chassis.


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When you say trackday are you meaning the Roadsport or one of the SLR versions, early (with Z plates), later or easy in,

The early SLR had mounts on the cage which are best changed as the were tubes and slight misalignment lead to cross threading, Arch changed the m to the later version for a small fee

You are best partially removing the inner panel to accurately drill out the mount holes 


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Not sure how, but I fitted a tall version of one of those without removing any rivets?Got it on by myself in a morning. Sounds like I was lucky. Two bolts up into it where the shocks mount, the two to the rear tub, and two through bosses in the chassis just below the screen.

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If you use a small round magnet, like one of those retrieving tools, you can find the location of the holes in the chassis. The magnet sort of self centres at the hole location. Certainly good enough to locate a pilot hole. Worth a try before drilling out rivets.

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OK, so progress so far.

I de-riveted maybe 6 rivets around where the bolt goes through. you can pry it back and see the threaded boss, drill some pilot holes and then use a step drill to get it right. all good.

not sure about the size of bolt that's needed yet, I think it's old-school but it has a 8mm holding the front legs in place now.

unfortunately there's clearly a problem. the inserts that go into the (extremely rusty and now swimming in dinitrol) chassis mounts are 1.5" long. the inserts on the old FIA bar are 1".


(pre-cleaning and rustproofing)

this means that the new bar sits' on the bottom of the insert instead of where it _should_ sit which is on the chassis.


I'm a little unsure what to do. any ideas? apart from ringing caterham and asking them. it also has Metric threaded bosses in it (which I can live with), but I'm glad I didn't apply the uggaduggas (not that I would).




wondering if I can get my mirror under the bar.

I already love how it looks.


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it's a 2006 factory built. I was under the impression as it has a chassis number stamped on the seatbelt boss behind the driver it is an imperial.... seems I may be wrong. anyone know a good solution beyond selling the cage at a loss and paying the newly inflated price for a metric?

definitely no spacers in there. just rust....

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I've just measured the length of the threaded stud on an imperial FIA bar that goes into the bucket on my 1992 imperial chassis and it is the same as your photo, 1 1/2". This does suggest that your original FIA bar is imperial and your chassis is metric. 

I don't know whether you purchased the trackday cage new or 2nd hand, but if 2nd hand I wonder if the cage which is a special order was specified to be imperial by the original purchaser?

The chassis changed from imperial to metric around 2006/07 I believe.

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If your car is factory 2006 then it would have been metric. The engine bay diagonals are possibly the easiest way to have checked. I'd think about removing the excess from the boss and making the hole deeper. The cage will have 7/16 unf threads in I expect unless they have commonised to metric on those newer style cages? At least yours is designed to take a full head bolt so you don't need to get a thin head bolt like on imperial cars 

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Fitting imperial cages and rollover bars to metric chassis cars is commonplace.  You will find that the cage 'stub' that fits into the chassis pocket is a solid piece that is threaded throughout its length. 

Simply arm yourself with a decent hacksaw and cut off the bottom 1/2 inch of the stub, check that the thread is fine (run a tap up it) and Bob's your uncle.


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thanks James (and everyone else), I can stop sobbing now. 

I'll check the thread depth and break out my hacksaw and some black paint then I guess.

Longacre is the plan, and some 3D printed brackets obvs. :D

I was pretty disgusted to see the price of the real ones.


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OK. it's been a week and a pretty long journey but I'm good.

firstly I ended up cutting a half inch off the bottom of the stubs. to do this I used a hacksaw rather than my angle grinder cos I was worried about making a real mess. to keep the hacksaw straight I printed off some 1" guides:


they worked really well to keep it all straight.

there was about 5mm of thread even though there was another 10mm of hole and I was left with the option of getting a 3/8 tap and tapping it, and just having my local motorbike engineer drill it out with a 9mm metric and tap it to 10mm. so that's what I did. it is now a metric rollcage for my metric chassis.


then it was just a case of.... re-riveting the holes. widening all the holes for the cage again as the cage is completely different left to right, swearing at it a lot, spraying loads of anti rust into the holes and.... screwing it all back together.

I don't have any copperslip so I'll go grab some tomorrow and then I can put the suspension back together.

I also added some 3D printed 1mm rubber gaskets in between the chassis and cage to stop water ingress, and a shitload of dinitrol for when it does.

I ended up buying and discarding loads of imperial bolts

anyone want a trackday rollbar? it'll be in For Sale pretty soon.


I'll even chuck in a gopro mount and some rubber gaskets...

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