Ride height

A confession. I don’t have the best garage exit for a Caterham. The garage floor sits 40cm above the level of the driveway, partly owing to the geography of the land about the house, and partly due to a previous petrol-head living in this location deciding that his/her garage should have a pit. The floor of the garage is raised slightly to make sufficient depth in the concrete foundation for a 1.5m deep inspection pit. The problem: neither the sump or the rear floor of the car clear the garage exit ramp to the driveway.

First time out of the garage.

First time out of the garage.

This challenge in getting the car out of the garage has led me to invest in some steel ramps, but also to pay some attention to the ride height of the car. My spec is a 360 with the S pack, so standard non-adjustable dampers. I also changed the S-pack wheels from 14″ rims to 13″ with an eye on unsprung weight. And looks, of course. I also added lowered floors. What I didn’t realise is that the consequence of these choices is that the unladen height of the sump above the ground, what I’m referring to as the car’s ride height, is under 66mm – the diameter of a drink can. With a full tank of fuel and me in the car this drops to 59mm.

After doing some research on Blatchat, comparing sumps with CTG Jason’s Sigma, contact with the Caterham Warranty team, and some excellent photos of CTG Simon’s 360R with adjustable dampers, it seems nothing is wrong, it’s just a consequence of my selections. The recommendation is to either buy some 14″ wheels (no chance) or fit the adjustable platform kit to the existing dampers, giving me full control over the ride height.

I’ve decided to buy the platform kit and in the meantime try it on the road when my registration comes through. My worries are all a bit academic if it turns out the clearance is fine. Speed bumps will be a concern but I’ll know after the first couple whether or not I need to avoid them until I get the kit. Wish me luck, and think carefully when ordering your kit and options as to whether it has any ride-height implications.

2 thoughts on “Ride height

  1. Hi Rob.

    I doubt the ride height is massively affected by your choice of wheel/tyre. I believe the 14″ rims have a lower profile tyre and a similar rolling radius.
    If they don’t then you’d have issues getting them under the front wings and the gearing would be affected.
    Moreso, its generally accepted that the 13″ set up is better in terms of grip, ride and general feel.
    As for ride height, it doesn’t look too much different to my ’15 R400 but it looks a little lower. I have 6″/8″ 13″ wheels and when sat on the ground empty the front lower w/bones are about horizontal. Yours seem to be sloping down to the chassis (?) in the above pic, which would imply a slightly lower ride height than I have, though you’re in the car. I’d tell you my sump clearance but my son has the car at his place at the moment.
    The adjustable dampers are a good idea. You’ll need them when you finally have it corner weighted and flat floored…………which you inevitably will at some point!!

    • Hi Peter.

      Thanks for the info and reassurance. It’s good to hear I’m not hugely out from other cars on the road.

      I did a bit of checking on the difference to the 14″ wheel/tyre combo Caterham supply and they tell me that the 14″ alloys are supplied with 185/60 R14 rubber, which (having googled it) have a diameter of 577.6mm. On my 13″ rims at the front (note that like you I went for 8″ rears) they fitted Avon ZZS 185/55 R13 with a diameter of 530mm. I lose half of the difference in ride height meaning I’m ~23mm lower than if I had chosen the 14″ rims.

      All of this depends on assumptions around tyre sidewall thicknesses and inflation pressures and so on, so I doubt it’s quite as simple as my maths above implies, and you make a very good point about the tyre still needing to fit under the wingstay, but I am pretty sure I’ve lost some height as a result of flipping to 13″ rims.

      The adjustable platform kit is on it’s way from Caterham now, so as you say, the full suspension set-up is only a matter of time!

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