paul jacobs Posted October 17, 2006 Share Posted October 17, 2006 I'm having a bit of an issue with bump steer on my CSR. It's fine on smooth roads, but as soon as I get on to a bit of bumpy road, [one of my favourite bits near by in fact] I have to restrict the speed to 60 otherwise it's all over the place ☹️ Has anyone with experience of the inboard front suspension used here, have any setup measurements I could try to save me doing it on a trial and error basis? Does more camber than recomended [ie 1 degree rather than quarter to half a degree] have any effect on bump steer? Otherwise what obvious things should I be looking at to remedy the situation, given that I have limited setup tools? Paul J. Loud pipes save lives. Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted October 17, 2006 Support Team Share Posted October 17, 2006 True bump steer is a factor of the change in camber as the suspension moves. This can be dialled out a bit on normal Caterhams by raising the steering rack a calculated amount. There are a couple of threads on how to do this if you search in Techtalk. On my car, when I switched to A048Rs, bumpy B-roads became a nightmare and it wasn't bump steer as such but more to do with tramlining. This can be reduced by adding some toe-in. If the car is set up parallel or even with toe out then tramlining will do its best to throw you through the hedge. Yellow SL #32 Link to comment Share on other sites More sharing options...
Hanns Per Posted October 17, 2006 Share Posted October 17, 2006 I am travelling on a lot of bumpy roads. With the car set up according to specs I do ot experience any problems rgds Hanns Per KOBER Hanns Per KOBER blatting the alps Link to comment Share on other sites More sharing options...
paul jacobs Posted October 17, 2006 Author Share Posted October 17, 2006 Hans Per, what specs are you using, either I've missed them, or I'm not looking in the right place. It's certainly not tramlining that I'm experiencing, I could start playing with the height of the rack, but, it would be on a trial and error basis, so wanted to make sure that other measurable things were right first. For example, I've set it up to about one and a quarter degs. of neg. camber and zere toe. I think I may still have too much neg. camber, and will reduce it to about half a deg. and see what happens, hence my query about the effect of camber on bump steer. Edited by - Paul Jacobs on 17 Oct 2006 20:06:39 Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 17, 2006 Share Posted October 17, 2006 Bump steer is mainly caused by change in toe rather than camber, usually as a result of the rack height being wrong. I'd be disappointed to hear that CC haven't got it right on the CSR. Excessive, or indeed any, toe out can make the car feel very 'darty' although it helps with turn in on hairpins etc, and I'd check that first before bump steer. I wrote an article on the subject in Low Flying a few months back which might help, or I can email it to you if you want. Alternatively, if you're near Guildford we can take look if it would help. Paul Link to comment Share on other sites More sharing options...
Jason Plato Posted October 18, 2006 Share Posted October 18, 2006 There is a chap near Warminster that does race car geometry setups for reasonable money . I'll dig out his number and post it tonite he will probably be able to measure the bumpsteer you have and offer a solution 🤔 here is C7 TOP South Wales AO Edited by - Dave Jackson on 18 Oct 2006 08:12:40 Link to comment Share on other sites More sharing options...
paul jacobs Posted October 18, 2006 Author Share Posted October 18, 2006 I don't think that this is a problem inherent in the CSR, rather than a setup problem. I'll dig out your article Paul, it my help. Maybe a touch of toe in would help? Warminster isn't oo far to go for this sort of thing Dave, I'd appreciate his details, thanks. Link to comment Share on other sites More sharing options...
fevans Posted October 18, 2006 Share Posted October 18, 2006 It would be good for all of us down 'ere in Devurn to know the details of this Warminster firm. Could you put it on this thread for us? Many thnaks in advance. Felix Yealmpton Link to comment Share on other sites More sharing options...
RWHomer Posted October 18, 2006 Share Posted October 18, 2006 Paul. Quite surprised that you have any bump steer problem. Rather like Hans Per I find that the CSR to have far superior bumpy road stability that other de deon 7's that I have had. Can only conclude something very wrong with the present set-up. Should respond well to the normal bump steer adjustments. Link to comment Share on other sites More sharing options...
paul jacobs Posted October 18, 2006 Author Share Posted October 18, 2006 When I took the car back to the factory for its post build check , although I asked for the suspension to be set up, they said that they didn't have the time to do it in the day which I had allowed, so I had to set it up myself, which by and large seems to have worked quite well, apart from the bump steer problem, which really only gets bad on quite bad roads, one of which, sadly, is on my favourite blatting route Link to comment Share on other sites More sharing options...
Bricol Posted October 18, 2006 Share Posted October 18, 2006 Just a thought - tyre pressures? Normal car type pressures will make it leap around everywhere on a bumpy road . . . although I have no idea what are recommended for CSRs, my old fashioned one runs somewhere between 15 and 18 depending on the mood, the load, the road, the phase of the moon . . . Bri Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 18, 2006 Share Posted October 18, 2006 Paul I would start by checking toe. Its easy to do and the most likely candidate. The standard de Dion road-going setting is 20mins toe IN and I would guess that the CSR is about the same. The symptoms you describe sound just like mine on anything other than a really good road after its been set up with a 1deg of toe out for hill climbs, even with the bump steer negated by correct rack height. Paul Link to comment Share on other sites More sharing options...
paul jacobs Posted October 18, 2006 Author Share Posted October 18, 2006 Bri, the tyre pressures recomended for the CSR are 24 front and 23 for the rear, which I have been using, although I am currently experimenting with 2 psi lower back and front. Thanks for the thought on that though. Paul, I am using zero toe in, parallel, in other words, so it wouldn't harm to give it a bit of toe in to see what would happen, after that, if nothing has improved, I will raise the rack a bit, then lower the rack a bit and "suck it and see" [as the actresss said to the Bishop ]. I'm sure that the perfect setup can't be far away Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 19, 2006 Share Posted October 19, 2006 Paul I wouldn't have thought zero toe would have such a pronounced adverse affect such as you describe. I'd try what CC recommend to start with (perhaps this is zero, I don't know). If you've found my article (June 2006 I seem to recall) you'll see that the change in toe with bump and droop is quite sensitive to rack height and should be adjusted in 1mm steps once you get close to the ideal (or best compromise). Mine was a whopping 16 or so mm out, 6mm of which was due to the absense of the lower rack mounting brackets. 😳 If you've got the time and patience its not hard to do right, but it does take time and you need to have a home made gauge. Best of luck Paul Link to comment Share on other sites More sharing options...
Martin S. Posted October 19, 2006 Share Posted October 19, 2006 . edited to remove my daft suggestion, doh 😬 Edited by - Martin S. on 19 Oct 2006 09:47:56 Link to comment Share on other sites More sharing options...
Jason Plato Posted October 19, 2006 Share Posted October 19, 2006 its a kit car returning to Caterham to dial in a bit of toe in is rather extreme they are built to be fiddled with and to suit the drivers taste here is C7 TOP South Wales AO Link to comment Share on other sites More sharing options...
Slipper man Posted October 19, 2006 Share Posted October 19, 2006 My suspicion is that you have some of the geometry settings wrong. Toe could be a factor, as could camber, but the interaction of all the variations can be complex. Any variations in settings on your car could well be at the back of the car as well as the front, so you would be well advised to take it to someone who can check all the settings, and get the corner weights right as well. I have an R500, and had the car 'flat floored' soon after build and it completely transformed the feel. I was surprised how much variation the car had in some of its settings if you just build it yourself and check everything with amateur tools I agree with you about the steering rack - check the basics first before assuming that Caterham got the basic design wrong. On the older cars, they actually did get it wrong, but the later cars were designed with special CAD systems (Jez Coates showed it to me) so basic flaws are unlikely. Link to comment Share on other sites More sharing options...
paul jacobs Posted October 20, 2006 Author Share Posted October 20, 2006 Thanks Keith. I know what a difference it can make having the car professionally set up, trouble is there isn't anyone near me with the experience or actually the setup to do this, Millwoods are probably the closest and they are about and hour and a half away. Thanks for the advice Paul D. Paul J. Loud pipes save lives. Link to comment Share on other sites More sharing options...
Petrolhead Posted October 20, 2006 Share Posted October 20, 2006 I would agree re the setting. Recently setup the caster on my R5 and ended up with a different number of washers left and right. I take it the current CSRs chassis were not made at caged? Anyway bach on track, are you its the front and not the back of the car? I am a little supprised as I thought with the new front suspension and independent rear that they were supposed to be much better for the road Link to comment Share on other sites More sharing options...
paul jacobs Posted October 20, 2006 Author Share Posted October 20, 2006 In all honesty, I feel that there is a measurable improvement in road manners, but, because I have not had mine set up properly yet, I have this problem, it's just a matter of knowing which way to jump, I have full confidence that it will not be difficult to sort. . I don't think I've mentioned the torque yet either, it's almost as good as sex and it last longer............. 😬 😬 😬 Paul J. Loud pipes save lives. Link to comment Share on other sites More sharing options...
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