Steering Rack Stiffness

[BigCol]

I met up with Garth of this parish yesterday and had a go in his car.

Like mine, it’s a Sigma-engined SV but his steering is much easier - almost as light as a power-assisted tip-top whereas mine gives me an upper body workout when driving at low speeds/manoeuvring.

When I built the car, I did query that the rack might’ve been stiff here and the conclusion was it was fine and the likes of Caterham at the PBC and James Whiting when servicing it haven’t commented that there’s an issue.

Should I (or Garth!) be worried and/or is there anything I can adjust to reduce the required effort?

[SM25T]

Lift front of car and wind steering from left to right. Is it tight. Remove gaiters from rack ends and grease teeth of rack. There is a preload screw on top of rack with a huge locknut. You can adjust this but always check after adjusting before you lower the car. Track rod ends can get tight .... or go very sloppy. Best thing I did was get rack raised 9mm to dial out bump steer. It made the steering so much nicer .... and easier even at parking speeds.

[ChrisC]

Also there are other factors like geometry and tyres in include your comparison.     I agree get the front end off the ground and check from lock to lock to see how it feels.   If it's binding while off the ground my diagnostic method would be to start disconnecting bit by bit until is free again.

[pugwash]

Size of steering wheel too.  I think you have the tiny suede Momo supersport one like I have.  Can’t recall what Garth has on his  but a bigger steering wheel will mean less effort to turn.

[K7 VCT]

Raising the rack, what's that all about ?

[ChrisC]

Don't put that in your google search 

The steering rack is lower on older cars, which if raised reduces bump steer.   CC sells spacers to help with this.   Later cars have steering rack clams which are thicker at the bottom to raise the steering rack.   Its one of the setup tweaks owners do.   Suspension and setup is a real dark art, and well worth investigating little quick wins if you have the time.

[Paul Deslandes]

Bump steer article

Bottom line is, if the rack top and bottom clamps are the same thickness, raise the rack by adding 9mm spacers under each clamp to minimise/eliminate bump steer.  If the lower clamp is 9 - 10mm thicker than to top, you probably have the factory modified clamps.

Paul

[SM25T]

Astonishing difference on my SV.

[SLR No.77]

I had previously fitted 9mm of spacers beneath my steering rack, however having recently fitted Nitrons and having had the car professionally set up by someone gifted in the dark art, I now have no spacers fitted. I suspect it has much to do with ride height though.

From personal experience tyres and geometry play a massive part in stationary steering weight, particularly camber angle.

Stu.

[BigCol]

You’re right, I’ve a suede wheel - well remembered!  

Garth’s wheel is leather but same size.  Both SV, both Sigma (so no difference in weight on wheels) same size steering wheel, same front tyre size - so couldn’t understand such a significant difference.

Unaware of any bump steer and my track rods are horizontal.  Will investigate as suggested by Ian (SM25T).

[K7 VCT]

Ah, thanks for the info.

2014 car so mine is modified already

 

 

[SM25T]

Nothing is certain with Caterham. Have you looked ?

[paul richards]

Castor affects steering weight. More castor equals heavier steering. Look at washer spacers on bottom wish one. You should also look at spherical bearing on bottom wishbones. They can become stiff. A little oil does no harm but make sure it is only a little and doesn’t get on brake discs. 

[blueyedbiker]

Don't know if you've tried it or not but take the steering column out of the rack UJ to check the friction of the column bushes, if that's ok put the column end back and disconnect the track rod ends from the steering arms - you'll need a splitter and work out if it's the rack or uprights where the friction is.  I found that the friction on mine was in the track rod ends - new but totally solid.

[Bricol]

I've had a seized UJ onto the rack before - meant you could turn the wheel and let go - it would stay where you left it rather than self-centre as you drove along.

 

[john milner]

When my steering rack stiffened I removed the 36mm nut from the top and pored a load of gloopy thick oil in there and worked it in by steering left & right with the wheels off the ground. I then topped it up with grease. Works well but the ends of the gaiters are now a bit greasy. I top up with grease as required when I think the steering is starting to tramline. There is a thread somewhere that specifies the gloopy oil.