Discussion
I've held off posting this for a while.
Having searched previous threads about this I've not managed to find anything much related to the S.
Discussions with other PHers lead me to believe what I'm experiencing is bump steer, uneven surfaces cause the car to want to follow a line other than straight ahead at speeds around the national limit.
On the flat it's rock solid at any speed.
I'm running an S2 on Oz wheels with Bridgestone 205/60/15s without any modified stuff in the suspension.
Was the same when I bought it in May but the shocks were tired so replaced with Gaz Golds.
Ride height 170mm all round. Shocks set quite firm but can't remember how many clicks.
Hasn't been corner weighed. Track rods are horizontal when car is sat.
Fire away chaps, I can't sus this one out at the moment..
Having searched previous threads about this I've not managed to find anything much related to the S.
Discussions with other PHers lead me to believe what I'm experiencing is bump steer, uneven surfaces cause the car to want to follow a line other than straight ahead at speeds around the national limit.
On the flat it's rock solid at any speed.
I'm running an S2 on Oz wheels with Bridgestone 205/60/15s without any modified stuff in the suspension.
Was the same when I bought it in May but the shocks were tired so replaced with Gaz Golds.
Ride height 170mm all round. Shocks set quite firm but can't remember how many clicks.
Hasn't been corner weighed. Track rods are horizontal when car is sat.
Fire away chaps, I can't sus this one out at the moment..
Firstly I'd , check all the ball joints, track rod ends etc for wear/play. Is everything in good order?
Are steering uj's ok? well known for siezing up, this will cause the steering to be heavy and almost stay in any position rather than self centre when the steering wheel is released. Is there excessive play in the steering rack, does the rack move as soon as the steering column turns?
Next get the tracking checked/adjusted if necessary.
If still "not right" look at getting a bit more involved with a "full Geo set up", King Pin inclination and Camber are adjustable on the S front suspension.
Find a reputable garage who know what they're doing (and know the correct settings) to do this otherwise it will be a total waste of money , imho
Might be worth getting rear tracking checked also, in case anything is wildly out there (corrosion, crash damage, bad repair etc.)?
Are steering uj's ok? well known for siezing up, this will cause the steering to be heavy and almost stay in any position rather than self centre when the steering wheel is released. Is there excessive play in the steering rack, does the rack move as soon as the steering column turns?
Next get the tracking checked/adjusted if necessary.
If still "not right" look at getting a bit more involved with a "full Geo set up", King Pin inclination and Camber are adjustable on the S front suspension.
Find a reputable garage who know what they're doing (and know the correct settings) to do this otherwise it will be a total waste of money , imho
Might be worth getting rear tracking checked also, in case anything is wildly out there (corrosion, crash damage, bad repair etc.)?
Edited by phillpot on Sunday 5th January 21:31
The feeling of "bump steer" can arise form sticky ballpoints etc, as said.
However, true Bump steer, that is, the car positively steering as the suspension load and unloads, is more likely to be caused by the steering rods (track rods) being slightly different lengths - the tracking might be right, but might have been adjusted on one side only by some lazy mechanic, and then the steering wheel moved by a spline or two so that it looks straight.
First turn the steering fully one way, without the wheels fouling the body etc, and mark where the top of the steering wheel is. Now turn it fully the other way and count the exact number of turns, then set it to exactly half-way: that should be your "straight ahead" position. If it's not then your rack is probably off-centre.
Alternatively, stop the car with the wheels at "straight-ahead" and without turning the steering wheel, measure the length of each track rod from the outer ballpoint, to where you estimate the inner ballpoint to be on each end of the rack. Both should be the same.
If either of these tests suggest a problem, then you need to have the tracking checked with the rack (not necessarily the steering wheel) properly centralised.
However, true Bump steer, that is, the car positively steering as the suspension load and unloads, is more likely to be caused by the steering rods (track rods) being slightly different lengths - the tracking might be right, but might have been adjusted on one side only by some lazy mechanic, and then the steering wheel moved by a spline or two so that it looks straight.
First turn the steering fully one way, without the wheels fouling the body etc, and mark where the top of the steering wheel is. Now turn it fully the other way and count the exact number of turns, then set it to exactly half-way: that should be your "straight ahead" position. If it's not then your rack is probably off-centre.
Alternatively, stop the car with the wheels at "straight-ahead" and without turning the steering wheel, measure the length of each track rod from the outer ballpoint, to where you estimate the inner ballpoint to be on each end of the rack. Both should be the same.
If either of these tests suggest a problem, then you need to have the tracking checked with the rack (not necessarily the steering wheel) properly centralised.
tvrgit said:
However, true Bump steer, that is, the car positively steering as the suspension load and unloads, is more likely to be caused by the steering rods (track rods) being slightly different lengths - the tracking might be right, but might have been adjusted on one side only by some lazy mechanic, and then the steering wheel moved by a spline or two so that it looks straight.
I had bump steer on mine and was advised by tvrgit, IIRC,to check this. Mine was a long way out (and the tracking was within tolerance). After adjustment and a full 'Hunter' four wheel alignment the car became much nicer to drive. Still get nice feedback through the wheel though which is one of the pleasures of the S.tvrgit said:
the tracking might be right, but might have been adjusted on one side only by some lazy mechanic, and then the steering wheel moved by a spline or two so that it looks straight.
A quick check (but not guaranteed) might be to measure the amount of exposed thread on each track rod ? Should be near enough equal.Might also be worth checking that the steering column uj's are aligned, this alone may not cause a big problem but often these "issues" can be a cumulative thing (imho).
phillpot said:
A quick check (but not guaranteed) might be to measure the amount of exposed thread on each track rod ? Should be near enough equal.
Might also be worth checking that the steering column uj's are aligned, this alone may not cause a big problem but often these "issues" can be a cumulative thing (imho).
Both good points.Might also be worth checking that the steering column uj's are aligned, this alone may not cause a big problem but often these "issues" can be a cumulative thing (imho).
The alignment of the steering column uJs is very important - I went into some length about this on my own web site last year, when I took the rack out to repaint the front of the chassis. As you say, if the UJs are misaligned, you get a "knock" though the steering as you turn it, that can also affect its self-centring, and can feel like "bump steer".
Agreed:
1. Different lengths of steering rods can have a dramatic effect. Garages do 'cheat' and adjust one side more than the other. Although the amount of thread showing is a good guide it isn't necessary exact enough as after market steering joins are not necessarily identical.
2. Probably unlikely on an S but just check neither steering track rod is bent while you are at it.
3. The measured ride height at the chassis is a good guide but what really matters in this context would be the measured ride height at the front suspension mountings wishbone mountings, and more particularly if they are the same under static load. That really means a check when you are in the car!
4. Ideally the track rods should go through an equal arc above and below the horizontal. Getting the ride height and track rod inclinations right at the same time might prove a bit of a tall order even if every joint is in perfect condition!
5. Poor lateral location of the rack (perished supports, worn or loose bolts etc) can create some interesting effects on some older cars (eg Spridgets)but I have never been aware of that as an issue on my S.
6.That steering column 'knock' can be amazingly pronounced, got me quite worried, and puts a lot of strain on the bulkhead mounting. There was quite a lot of stress cracking round the bulkhead on mine and it is now reinforced. If you think that might be a problem, jack it up just enough to enable the steering to turn easily and just feel round the bulkhead bearing while someone turns the steering for you. You may well feel the flex as it tries to compensate.
1. Different lengths of steering rods can have a dramatic effect. Garages do 'cheat' and adjust one side more than the other. Although the amount of thread showing is a good guide it isn't necessary exact enough as after market steering joins are not necessarily identical.
2. Probably unlikely on an S but just check neither steering track rod is bent while you are at it.
3. The measured ride height at the chassis is a good guide but what really matters in this context would be the measured ride height at the front suspension mountings wishbone mountings, and more particularly if they are the same under static load. That really means a check when you are in the car!
4. Ideally the track rods should go through an equal arc above and below the horizontal. Getting the ride height and track rod inclinations right at the same time might prove a bit of a tall order even if every joint is in perfect condition!
5. Poor lateral location of the rack (perished supports, worn or loose bolts etc) can create some interesting effects on some older cars (eg Spridgets)but I have never been aware of that as an issue on my S.
6.That steering column 'knock' can be amazingly pronounced, got me quite worried, and puts a lot of strain on the bulkhead mounting. There was quite a lot of stress cracking round the bulkhead on mine and it is now reinforced. If you think that might be a problem, jack it up just enough to enable the steering to turn easily and just feel round the bulkhead bearing while someone turns the steering for you. You may well feel the flex as it tries to compensate.
Just for interest/amuzement: on the old 750MC Austin 7 racers a big issue was bump steer. With the standard chassis the issue was pretty dramatic understeer, so much that hitting a bump on the limit was likely to spin the car or even turn it over! A lot of time and thought went into chassis mods to dramatically change these characteristics and a good A7 racer will go into a controlled slide understeer, little effected by moderate bumps. Still a pretty hairy experience though!! It is still sitting in the garage waiting for my grandson to 'race' it...I can't even get in now!
I see from your profile your in Leicester which is very close to http://www.guglielmimotorsport.co.uk/
They know all about S's and setting them up
They know all about S's and setting them up
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