CageyH Posted January 15, 2004 Share Posted January 15, 2004 Having just bought my first 7 (a 1.6 SS) I have been out "exploring" the car. On a nice smooth surface, the car feels great. The problem is that on a bumpy surface, it feels a bit "twitchy", almost having a mind of it's own. The car has adjustable Bilstein dampers, but I am not sure about what rate springs it has. How do I find out the spring rate??? The car is fitted with 186/60/R13 A021R's, running at 17PSI all round. I intend to use the car mainly for road use, with an occasional track day (once I have learnt to drive the 7 properly!). My objective is to get the car set up for fast road use, or as the IAM would say - "to make efficient progress"???? I also have a 10" steering wheel, which I have to admit feels very strange. A bit too small. What's the optimum size for a 7? Link to comment Share on other sites More sharing options...
simonbell Posted January 15, 2004 Share Posted January 15, 2004 Can you adjust the damping on the Bilstein`s or are they just height adjustable? I presume it is a de dion car......... Make sure nothing is loose........when mine felt twitchy I found the live axle floating about a bit. TTHings do come loose on se7ens so bolts need to be checked and torqued regularly. Everything else looks in order, try adjusting damper settings. Have engine.......need car I`ve seen the future.....and it`s powered by duratec Link to comment Share on other sites More sharing options...
Jason Plato Posted January 15, 2004 Share Posted January 15, 2004 They all do that sir 😬 but if it does realy feel unstable , have a front wheel alignment check done . The dampers shouldnt need adjusting . Many people use a 255mm > 270 mm steering wheel . Link to comment Share on other sites More sharing options...
Tony C Posted January 15, 2004 Share Posted January 15, 2004 I found that when I first started driving my 7, but I think it's mainly due to the unconscious comparison we make with the average tintop. It's necessary to pay attention ALL the time when driving a 7. However, the advice to check tightness and set-up is good 😬 BRG Summertime Brooklands SV 😬 It is only with the heart that one can see rightly; what is essential is invisible to the eye. (Antoine de Saint-Exupery) Link to comment Share on other sites More sharing options...
Michael_E Posted January 15, 2004 Share Posted January 15, 2004 Kind of same advice, check your nuts. And... "Yes they all do that sir" Even with a car that’s been flat floored, putting your foot down on bumpy roads can be interesting. You become more adept with practice and you'll soon find yourself making smaller and smoother inputs with the steering wheel. The size of wheels are small and again you soon get used to it and if you spend some decent time in the seven you'll start to find your tin-top a large dull experience. Your reading of the road surface improves as will pothole and road kill avoidance (Helen yesterday saw a half brick in the road which because of traffic she couldn't avoid and almost screamed, until she remembered she was driving the Clio!) If you think you might have a problem with the car and are unsure what to look for then try your local meeting and let somebody else take it out for a test run to compare or take it along to one of the recommended dealers / specialist garages (i.e.: Caterham – Dartford, Rat race, 7 workshop, James Whiting...etc) C7 MLE The Furry Fast Car Currently wondering what colour fur for 2004? Link to comment Share on other sites More sharing options...
Pelico Posted January 15, 2004 Share Posted January 15, 2004 Been there ❗. Check front suspension geometry. When I collected it my 1.4SS on Bilstiens had half a degree of toe out and 3 degrees of camber on each wheel. Turn-in was great, but terrifying to hold on to it on bumpy back roads. Put it back to factory settings and it is fine. My new Caterham owner's site Link to comment Share on other sites More sharing options...
Michael_E Posted January 15, 2004 Share Posted January 15, 2004 Oh and welcome to the wonderful world of Seven's. And if you've never owned such a light fast car then take it easy in the wet until you've practiced spining on a track day / academy day 😬 C7 MLE The Furry Fast Car Currently wondering what colour fur for 2004? Link to comment Share on other sites More sharing options...
Nick Woods Posted January 15, 2004 Share Posted January 15, 2004 My guess is that the steering is toed-out, my car was originally very twitchy and we found it was toed-out. Once it was toed in a bit - 1/3rd degree in my case for standard track - it improved no end. Its now widetracked with zero toe-in (ie parallel) and its fine. Nick Red and Black 1.6K supersport Link to comment Share on other sites More sharing options...
Graham Sewell Posted January 15, 2004 Share Posted January 15, 2004 The other thing that took me ages to get used to, is because the steering is direct there is a tendancy to try to overcontrol it. Hold the wheel firmly but lightly and let your arms absorb some of the feedback from the road. If you try to hold the wheel too firmly (as you would in a tin top) then the car bounces all over the place. Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
Alias Posted January 15, 2004 Share Posted January 15, 2004 Agree with the others that toe-out is the first thing you will want to check. Some people put up to 20 minutes, but having run with this setting it does make the car twitchy (and can wear the inside section of the tyres out). The other thing you may want to check is the spring rates. If you have soft on the front and hard on the back this will also make your car very twitchy over a bumpy surface. One car - 1400 Supersport with 6 gears and clamshell wings. Link to comment Share on other sites More sharing options...
Tyrone Posted January 15, 2004 Share Posted January 15, 2004 As previously stated, it may be experience. My cousin (a non 7 owner) drove my car and thought it was 'very twitchy'. My brother (3 7's so far) thought mine was very well behaved compared to his 1.6 Roadsport. The his Roadsport seemed well behaved compared to his Superlight. No doubt the Superlight will appear more tractable compared to his inevitable next purchase. Link to comment Share on other sites More sharing options...
philwaters Posted January 15, 2004 Share Posted January 15, 2004 I had terrible bump steer for a while and when I removed the shims from the steering rack it went away - made such a huge difference I was gob-smacked 😳. A quick check is to see if when the car is on a flat bit of ground, are the steering arms level with the ground? They should be pretty close. Oh, and welcome - there is no escape now 😬 Phil Waters Link to comment Share on other sites More sharing options...
SteveP Posted January 15, 2004 Share Posted January 15, 2004 Just following on from the last comment, can someone explain what bump steer is and how to spot if you have too much of it? SteveP Link to comment Share on other sites More sharing options...
Red Line Components Posted January 15, 2004 Share Posted January 15, 2004 If you bought it from Caterham see if they will check it over - i got mine flat floored etc f.o.c. Link to comment Share on other sites More sharing options...
Sheds Moderator Posted January 15, 2004 Share Posted January 15, 2004 Bump steer is the tendency for the effective length of the track rod (between the steering rack and the road wheel) to shorten and lengthen over its travel. Obviously this is a bad thing since you don't want a wheel steering itself if it goes over a bump. To avoid this the rack has to be level with the track rod ends and the track rod horizontal. If you don't understand picture a steering rack several inches above the road wheel, with a track rod going diagonally downwards to the wheel. Then lift the road wheel, the track rod describes an arc. You will find that at the top of this arc the track rod is further away from the centre of the car. This would obviously turn the roadwheel as it has nowhere else to go. Bump steer. Ideally the steering rack would go up and down with the wheel(s) but it can't. Link to comment Share on other sites More sharing options...
Tony C Posted January 15, 2004 Share Posted January 15, 2004 Would it be reasonable to suppose that because the 7 weighs less than the average tintop the force from road bumps is going to be a greater proportion of the weight and therefore tend to throw the 7 around more - basically speaking 😬 BRG Summertime Brooklands SV 😬 It is only with the heart that one can see rightly; what is essential is invisible to the eye. (Antoine de Saint-Exupery) Link to comment Share on other sites More sharing options...
Graham Sewell Posted January 15, 2004 Share Posted January 15, 2004 BatteredOldSuperSport, Surely the requirement is for the track rod end to follow the same arc as the wheel upright. This does not require that the steering rack moves, just that the pivot point is in line with the upper and lower wishbone mounting plane on the chassis side, and that the length of the track rod end is in proportion. This would then mean that the track rod end would move as if in the same plane as the wheel upright and hence no bump steer. However, as all things are compromises this would only apply to one position of the steering wheel (straight ahead) and steering feel may well be compromised as soon as you want to turn a corner. Link to comment Share on other sites More sharing options...
andy couchman Posted January 16, 2004 Share Posted January 16, 2004 ...another possibility is that the car may be 'nose up' - the back end is too low relative to the front. That can make the car feel really nasty at speed, even on a straight piece of road as it will wander about. The solution is to run the back of the car slightly higher than the front - a flat floor set up should cure all such ills. Andy Link to comment Share on other sites More sharing options...
Gridgway Posted January 16, 2004 Share Posted January 16, 2004 I am not sure I quite get you Graham. The upright essentially goes up and down at the same angle to the road. Ie it pivots around a centre at infinite distance. The track road has a much shorter radius(!). So unless the rack moves up and down, bumpsteer cannot be eliminated that way. Graham Link to comment Share on other sites More sharing options...
Graham Sewell Posted January 19, 2004 Share Posted January 19, 2004 I thought that the Seven used unequal length wishbones, so camber will change with wheel movement. However, as you say, if the track rod is shorter than the wishbone, then there is no way that bump steer can be removed, only optimised around the straight ahead position. Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted January 19, 2004 Share Posted January 19, 2004 So many variables can cause this sensation, but a steady working through of the possible solutions will pay off. My car 'bucking-all-over-the-place' episodes turned out to be worn front dampers even though externally they seemed fine with no leaks etc! Had checked a lot of other (easier) stuff first though!!! Link to comment Share on other sites More sharing options...
millsn Posted January 19, 2004 Share Posted January 19, 2004 sO YOU NOW HAVE 1) Tracking 2) Bump steer 3) Front to rear rake angle And don't forget to add bolt position of the rear radius arm. I found that having this in the lower position improved matters. 4) Also I reckon mine's got worn balljoints which doesn't help much. 5) I've also had the camber adjusting lock nut be slightly loose so my camber changed under load (also unhelpful). 6) Also: Check that you've not got slop in your rack as this can let the car do whatever it wants (hold the wheels steady and rock the steering wheel-you'll feel it). when you do this it's worth checking that the bush that is behind your dash that supports the steering column is not worn. When it's worn it makes the car feel quite dead and you won't realise it without testing for it. Nigel Mills - 2.0 Zetec carbs Link to comment Share on other sites More sharing options...
Graham Perry Posted January 19, 2004 Share Posted January 19, 2004 If its a de-dion, also get the rear geometry checked. It should be parallel for road use. If its toed in then an 'interesting' drive can follow. Also worth having a look in the archive re Caster angles as these are adjustable on some cars and can also make a difference Link to comment Share on other sites More sharing options...
Gridgway Posted January 19, 2004 Share Posted January 19, 2004 the bottom spherical joints definitely have a limited life. Graham Link to comment Share on other sites More sharing options...
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