Heavy Steering

[Paul McKenzie]

I recently changed my steering rack from the steel cased flared wing type rack to the usual alloy cased Caterham branded 8% rack. As well as the turning circle being prejudiced, the steering is now annoyingly heavy and is spoiling the driving experience.

 

There's nothing wrong with the new rack which has been completely overhauled and improved including the phosphor bronze thrust block mod., but I can't believe that this steering weight is normal. The steering also weights up significantly even more going through corners.

 

I wonder if it's anything to do with the front suspension set-up with the new rack . Although nothing has been changed I can see that the track rods are not exactly parallel with the ground and are pointing very slightly upwards towards the wheels. I could shim the rack to level these off, which I believe would reduce bump steer, but will that also reduce steering weight?

 

Has anyone had the same experience and are there any fixes , or do I just have to get down the gym for some bench press training

 

Paul

[xflow7]

Hi Paul,

 

I'd also check the angle that the bottom U-joint is being subjected to. It is possible if the rack housing is rotated too much (moving the spline downward) to bind the u-joint, which can result in very high steering effort.

 

Good luck

 

Dave

[Paul Richards]

Paul

Your new rack is probably quicker than the old one and this could be a reason for heavier steering. Yes - you are right, turning circle is not as tight (stops cycle wings catching on body).

I note you have had the phosphor bronze thrust block mod. Could this be the problem?

It could be that the thrust block is too tight.

I recently tightened mine to remove a little play in the steering. Steve G. suggested to me that a good test (to make sure steering is not too tight) is to pull on the steering wheel slightly (car at rest) and steering should return itself by the force of the tyres.

I would certainly suggest slackening the block, putting in some grease (remove boots to do so) and slowly tightening the grub screw/block and checking for play/stiffness as you go.

Top tip - lock nut for grub screw is 36mm. If you don't have a spanner, I can lend you one or you can get one from Halfords or any cycle shop for around £5. They are used on crank or headstock of pushbikes.

Camber or bump steer should not affect stiffness of steering. Castor is the thing which can make steering heavy, although you appear to have done nothing to affect this.

Hope you can understand what I'm getting at - if you need me to explain - 0161 763 5410.

Regards

Paul R.

 

Edited by - Paul Richards on 3 Aug 2004 13:36:17

[Graham Sewell]

I noticed this change in steering weight when I did the "upgrade" about 7 years ago as the original rack was not available anymore and I needed a new rack.

 

You eventually get used to the extra weight - but in an ideal world, I would prefer to go back to the original.

 

Low tech luddite - xflow and proud!

[V7 SLR]

Can I ask where you had the rack upgraded and whp supplied the new thrust block?

 

I need to do this to mine.

[Paul McKenzie]

Thanks for the replies guys

 

V7, I had it done by Dave Brookes in Crewe. Dave also did the first one for ClayHead's car and he's really chuffed with the results.

 

Dave Brookes Engines 01270-661850

 

Mention mine or Tim's name and he'll make sure our commission is added

 

Paul

[Bare]

Hard to believe there was that significant a change in steering weight.. Often a poor adjustment of the Rack Pressure Bush.. the Bronze Bit you had 'upgraded' can REALLY mess things up.

In Fairness it's a V fiddly adjustment..a 1/4 turn can make Huge difference in steering weight... takes me at least 3 or 4 tries when I decide to 'fool' with one.

Suggest backing it's adjuster off a 1/2 turn.. then deciding if the problem is still there. it may, or it may not :-).. but at least you will know if it's due to the adjustment.

[CHRIS CLARK]

I went from the old, original '93 Mini rack (0%) to the race rack (22%). Steering is heavier at 'parking' speeds, but much nicer to drive with at all other times. Think it it a turn and round it goes!

 

Suspect your playing with this block has a bit to go yet!!!

[Peter Carmichael]

Excessive weighting up of steering may also be because of an inherent handling characteristic in your chassis setup.

 

If the car is understeering, the steering weight can be very high. If the car has a rear steer characteristic that helps turn the car, the effort can be significantly less. This is sensitive to ride height changes at the back.

 

Typically bumpsteer will show up as kickback over, you guessed it, bumps. Bumpsteer can never be totally eliminated and it is not as simple as setting track rods level as the other suspension linkages are not level to provide camber compensation. A small amount of bumpsteer is necessary as it improves the feel of the car; you get an idea of the ebb and flow of grip.

 

The other thought is to check that you do have the 8% rack you think you have and not the 22% (only the pinion is different). Does it have more than 2 turns lock to lock or closer to 1.75 turns?

 

 

 

 

[Graham Perry]

I changed to a Bronze bush several years ago after I had a friend who used to repair racks look at mine and its inconsistent feel. His opinion was that the plastic block (he called it a 'slipper') and the poor bent washer style thrust 'spring' were the problem. He said that due to lack of travel in the original spring that the block would bottom out as the rack moved up and down about 4mm or so as it travelled lock to lock and hence the rack would go stiff. I had an engineering company make a new Phosphor bronze thrust block to tighter tolerances and fitted a stronger traditional style spring that was used in a rack, and it transformed the feel. More importantly the level of adjustment in terms of its tension was much more variable. We spent about 30 hours messing about with the rack trying to work out what the problem was. Since the changes I have had no problems whatsoever.

 

 

 

Edited by - Graham Perry on 4 Aug 2004 08:03:58