Hi, I have a de Dion Supersprint with gaz adjustable dampers. Our roads over here in France have virtually no traffic (except at lunchtime), but they are often very bumpy. I am experiencing a lot of uncomfortable kick back on the steering wheel. Tyres are 14" at 19 PSI. There seems to be very little slack in the steering, and the wheels start turning instantly the steering wheel is moved. The front wheel bearings have a very slight bit of play, and need tightening just a tad, but I can't spot anything obvious. I think that the car has always been the same, but it has previously been driven on smoother roads. Are there any things to check please, or is there a way of improving the steering, such as a steering damper of some type? Thanks for any advice. Cheers, Paul.
Lack of slack is just what many of us want in a Seven!
But are you describing bump steer? Does it feel as if you have to correct the steering when you go over a bump?
A common cause of this in Caterhams is inappropriate height of the steering rack. Roger Swift's Guide to Bump Steer, and some previous discussions.
Jonathan
I had this on my previous car (2007) and it felt like it was continually driving me off the road. I tried lots and lots of different geometry settings before I tackled it, but in the end it was bump steer. I raised the steering rack by 6mm with 3x 2mm deep aluminium shims I made underneath each side of it.
Then I adjusted the wheel alignment back to where it was. Afterwards I could literally steer with one finger and it transformed the car! The generally accepted amount is to raise it by 9mm and that's what the newer deeper Caterham steering rack mounts do. However my old car was ex academy so might have had a new front end on it at some point hence it only needed 6mm.
Newer cars don't tend to suffer from this as much, if at all.
22daz
Bump steer .... raising the rack on our car transformed it.
Check the bump steer.... I have done a couple now that needed to be lowered, theres a fair bit of variation on chassis rack mounts, uprights and steering arms too, and some cars dont run the lower wishbone spacer too, set up will also impact on it.
I added spacers under the rack because that was the general consensus of what was needed ... then when it was correctly (professionally) flat floored all my spacers were removed to dial out the bump steer!
Stu.
Caterham and Lotus Seven Club Leadership Team Member
The register for all numbered limited-edition Caterhams ....... www.thecaterhamregister.net ...... www.instagram.com/thecaterhamregister
I put 8mm under my rack, based on concensus rather than accurate measurement and it made a massive difference.
Be aware the hole for the rack in the side skin may need elongating so the gaitors dont catch. I used an emory flap wheel in the cordless drill and took out 5mm.
Ian
Paul Deslandes: "Measuring and Correcting Bump Steer on a Caterham 7 Using Cheap Home Made Gauges."
But how about adding a nose-on camera-horizontal photo showing the angle of the track rods?
Jonathan
Wow!! Thanks guys, that's really helpful. I think it is bump steer. I can make up shims, and gradually raise the steering box, but am completely out of my depth with alignment etc, and nobody seems to trust local "experts". After new suspension arms were fitted to our daily driver, I took it to Angouleme for new tyres and tracking, but afterwards, the steering wheel was not even straight, and the car veers slightly across the road when pointed straight - just what you want!! Is it just the camber that will need adjusting once the rack is raised please? I found a vehicle alignment report from 10 years ago, done in Wales. TBH I don't understand it at all, and it says Caterham K series 1991- 2011, which is the wrong model..... Although 10 years ago, the car has only done 1000 miles since, as the last owner didn't use it, and I have been restoring it. The report shows specifications, initial readings, and final readings, but some of the final readings are further outside the specification figures than the initial ones. The car is for recreational road use only, so it just needs to be safe and enjoyable to drive fairly fast.
I've got the factory specs for a large number of Sevens, please let me know if you'd like the ones that are appropriate!
Jonathan
Yes please Jonathan. The car is a 1989 de Dion Supersprint with Roger King 1800 plus package and adjustable dampers all round.