The basis of the Caterham Seven is a mild steel spaceframe chassis that is similar in design and look to the original's from 1957. It has been developed and improved over the years to its current state, which is a very rigid platform for the rest of the car.
Good news is the chassis is resilient to corrosion generally, though it can rust from the inside out, so take a good look at every section. Access to almost all of the chassis is very good if you're prepared to crawl under the car or can get it on a ramp. The chassis offers decent crash protection too and all K-Series models will benefit from honeycomb side protection and powder coating for improved durability.
De Dion rear suspension for flasher Sevens
Caterham had to alter the chassis to allow the K-Series to fit, so the engine bay diagonals had to be spread by an inch at the rear, so this is an identifying mark for a K-Series-powered car. This should also be borne in mind if you have to order a replacement section for the chassis in the event of a crash. Smaller front sections are available to replace damage to the front suspension or you can buy a complete front end. Complete chassis replacements are also easy and relatively quick to complete thanks to the Seven's bolt together construction. With any chassis that has been repaired, make sure it has been properly rust-proofed afterwards as the original powder coating protection will have been broken to make the repair.
The chassis design was improved in 1996 and then again in 2001 to make it stiffer. For 1996, the handbrake moved to the centre tunnel, while 2001 saw elements from the R500 frame incorporated into every other Seven model. All Sevens have a roll-over bar fitted, while some come with added braces or extended cages and side protection bars. How far you want to go down this route is based on your own feelings towards safety.
Simple double wishbone front suspension with coilover shock absorbers and anti-roll bar works very well. At the back of K-Series Sevens is a De Dion suspension set-up with an anti-roll bar fitted to some but not all models. Several owners report the anti-roll bar makes the car too stiff for road use and they have removed it unless they are using the car for a track day.
Early K-Series models suffered from suspension bushes that wore out quickly, needing changed after only a few thousand miles in some cases. Caterham replaced these with an improved bush design, so this shouldn't be an issue now. However, the Seven is very sensitive to worn suspension components and it will affect the handling and steering noticeable, so budget for this if any car you look at has not been fully maintained. The condition of the front suspension wishbones is usually a good indicator of how fastidious the seller has been: perfect wishbones suggest a careful owner, while rusty and pitted wishbones point to a careless custodian.
Rack and pinion steering is light and direct with no power assistance to worry about. There should be no problems with this set-up, but make sure the car tracks straight on the road and the tyres show no uneven wear to indicate crash damage to the chassis.
Disc brakes are fitted all round to the K-Series versions of the Seven and they vary in size from the original 1.4's 228mm discs front and rear to the 254mm front discs used on the most powerful models. All work well thanks to the Caterham's low weight, while some owners prefer uprated pads for sustained track use.
Wheels come in a variety of sizes, mostly 13- and 14-inch diameter, which gives a broad choice of tyres that are very affordable. A set of tyres for a Seven can cost from as little as £220, though the stickier you want, the more expensive they become.
Caterham also offered an SV version of the K-Series Seven with a wider, longer chassis to accommodate taller drivers. This chassis went on to be offered with a variety of engine options, but all have an 80mm longer and 110mm wider cockpit. Caterham had already provided more foot space for the driver with a revision to the chassis in 1994, but the SV gained a further 25mm of height and 55mm of width for the driver's feet.
The SV has a 110mm wider track front and rear thanks to its wide track suspension, which has become a popular upgrade for other Seven owners to further improve handling and high speed stability. The penalty for this with the SV was an overall increase in weight by 25kg.
PHer's view:
"Think about a brake upgrade from standard (drive both if possible). Although ultimate stopping power isn't hugely different, I found the big brake kit (four-pot calipers on the front) gave a much better pedal feel, more modulation and thus more confidence. Set your suspension set-up properly and ideally corner-weighted, with the rake properly set with you in the driver's seat. It makes a huge difference, especially on track."
Neal Hodges
Buying guide contents:
Introduction
Powertrain
Rolling Chassis
Body
Interior