revilla Posted January 24, 2014 Share Posted January 24, 2014 I'm planning to put some spacers under my steering rack (2003 Imperial De Dion K) to reduce bump steer. I have read the excellent article by Paul Deslandes but as everyone seems to come to the same conclusion, i.e. that the rack needs to be raised by 9mm, I'm just going to do that and see how it goes for now. Caterham sell these and the website says "3 required per model", so I assumed that the standard requirement seems to be 9mm, they would be 3mm thick and ordered 3. When they arrived, they were only 1.5mm thick. So I ordered another 3. When the next 3 arrived they arrived they were only 1mm thick! 😔 Caterham also sell these and say "2 or 4 Spacers required per car depending on the spec" which is hardly helpful, and they seem to be permanently out of stock. 😔 I was also led to believe that the steering rack clamps on later cars were assymmetrical, with thicker bottoms than tops, and fitting a set of these does seem a neater way to solve the problem but the only rack clamps I can find on the website are these which look symmetric to me. 😔 So I'm left with a choice between an ever-increasing stack of ever-diminishing aluminium plates with a long bar in the middle that does I don't know what, some other spacers of unknown size that I can't actually buy or some mythical asymmetric clamps! Before I phone Caterham Parts and get grumpy, am I just being a bit thick and what have other people used please? Link to comment Share on other sites More sharing options...
myothercarsa2cv Posted January 24, 2014 Share Posted January 24, 2014 Washers for me... Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 24, 2014 Share Posted January 24, 2014 Glad you enjoyed the article . 9mm seems to work for nearly everyone so, unless you think there might be a good reason, going through the measurement process should be unnecessary. Can you find a local engineering firm to knock up a couple of spacers, they'll often do little jobs like this in their lunch hour for tea money? Loughborough is bound to have a firm that would do it for you. Just take in one of those you've bought and ask them to replicate a couple, only 9mm thick. Remember, you'll also need longer 1/4" UNF bolts. M6 are just a bit too small for a good fit. Paul Link to comment Share on other sites More sharing options...
revilla Posted January 24, 2014 Author Share Posted January 24, 2014 That did occur to me, but I was worried that the lack of load-spreading from the small contact area of the washers could put the rack mount bolts under heavy shear loads when the rack was subjected to high cornering forces. I'd feel happier with something that supports the whole contact area of the rack mount unless people could convince me it wasn't necessary. Link to comment Share on other sites More sharing options...
revilla Posted January 24, 2014 Author Share Posted January 24, 2014 Hi Paul, yes a most interesting article thanks! Getting some made up would probably make sense. I'll have a look on the internet for somebody local who could do it for me. Any thanks for the tip on 1/4 UNF bolts, I knew they weren't metric but I couldn't remember exactly what they were. Now I know! Link to comment Share on other sites More sharing options...
TomB Posted January 24, 2014 Share Posted January 24, 2014 Was this an article in Low Flying or a web article? Id be interested in having a look to compare with what I have. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 24, 2014 Share Posted January 24, 2014 t was in Low Flying a few years ago but you can download it from here. Link to comment Share on other sites More sharing options...
Guest Posted January 24, 2014 Share Posted January 24, 2014 30S018A is definitely the asymmetric steering rack clamp and it measures 13.5mm bottom and 4.5mm top and uses m6 x 70 cap heads. I don't think the online store pictures are always correct! Mike Link to comment Share on other sites More sharing options...
revilla Posted January 24, 2014 Author Share Posted January 24, 2014 @mikecocker - Thanks for the info. Those measurements sound about right, although going on Caterham's recent performance if I buy a pair, all four halves will be different sizes Link to comment Share on other sites More sharing options...
Wrightpayne Posted January 24, 2014 Share Posted January 24, 2014 Rev, I'll have a couple of 9mm spacers if you're getting some made up. Bulkbuy!! Ian Link to comment Share on other sites More sharing options...
Mankee Posted January 24, 2014 Share Posted January 24, 2014 I'm up for some of these as well, actually! It's one of those jobs I've been meaning to look into for ages. I can ask my local fabricator if you like? He's made me a floor, shortened passenger footwell, stepped air filter backplate and a silencer tube, amongst other things. Link to comment Share on other sites More sharing options...
revilla Posted January 24, 2014 Author Share Posted January 24, 2014 Ian, Mankee, I was edging towards buying the asymmetric mounts but as there seems to be some momentum building behind getting some spacers made up, I'm up for it. I'll send the assorted useless strips of aluminium back to Caterham and get my money back! Mankee, if you have a "tame" fabricator that would be great. I'll hopefully get to strip mine down over the weekend and I can take some measurements and do some drawings for you. If you want I can post you one of the lower mounts so your man can see what we are aiming to achieve and check fit etc. Just one thought, mine is a 2003 Imperial Arch chassis. I guess the only difference on the later metric chassis would the change from 1/4 UNF (6.35mm) to slightly smaller M6 (6mm) bolts as used on the asymmetric mounts these days. Are your cars metric or imperial? Do you know, have they been supplying the asymmetric mounts as standard since the metric chassis came out? Also mine is an SV, but I'm pretty sure the rack bodies and mounts are identical, its just the track rods that are longer, so won't impact on this. If you can get some made for a reasonable price, it might be worth running a bulk buy thread to see how many others would go for it? Andrew. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 25, 2014 Share Posted January 25, 2014 I've not had the opportunity to measure an SV but I suspect the longer track rods and a standard rack will make the bump steer measurement different on an SV to a standard S3 chassis, as end of the longer TR will move less laterally as it has a greater arc radius. I assume the SV wishbone lengths are the same as an S3 and would expect the bump steer to be less pronounced. Might be worse of course 😬 It would be good if someone could do the measurements and post them on here. Or, if they want to bring an SV to Gomshall, I'd be happy to do the measurements here. Just have to dust off the gear. Paul Link to comment Share on other sites More sharing options...
revilla Posted January 25, 2014 Author Share Posted January 25, 2014 Paul, Yes I see what you mean. I guess wide track front suspension will tend to have the same effect too. Assuming 9mm seems less and less like a good idea now and I'm glad you pointed these things out. It's funny because the handling of my car definitely suffers from what I assumed was bump steer. I've checked the tracking and it's spot on. In fact I've had a full flat floor done, so I think the geometry is otherwise OK. For example there's a particular place on the A46 where there's a bit of a pothole, it's only really a shallow smooth depression and in the tintop you would hardly notice it, but if the nearside front runs through it the car tends to dart off to the left quite aggressively. Maybe there's an element of TADTS and it's just the directness of the steering on a Seven transmitting the kick the wheel gets back up through the steering. The car is currently on SORN for the winter so I can't bring it over to you. If you wouldn't mind helping me measure it sometime in the spring or summer when it's back on the road, I'd be very grateful. At least if we did come out with the conclusion that it needs 9mm again we would know it was a pretty much universal design error. Ian, Mankee, Given Paul's comments above I'll probably hold off doing it for now. If it does turn out to need the same 9mm as everyone else, maybe we can then have a look at getting some spacers made up for a bulk buy. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 25, 2014 Share Posted January 25, 2014 Andrew, you'd be very welcome to bring the car down when its back on the road. Certainly everyone whose altered the rack height by the right amount has noted a significant improvement to stability, so its well worth doing. See you when the weather improves! Paul Link to comment Share on other sites More sharing options...
Mankee Posted January 25, 2014 Share Posted January 25, 2014 Andrew, if you get a chance, can you email me a scan or diagram of the shims with measurements and I'll ask how much 9-mm-thick versions would cost for a start. Link to comment Share on other sites More sharing options...
John Vine Posted January 25, 2014 Share Posted January 25, 2014 Paul, YHM. JV Link to comment Share on other sites More sharing options...
revilla Posted January 25, 2014 Author Share Posted January 25, 2014 Paul, Thank you very much, most kind. I will be in touch later in the year. Mankee, BM me your address and I'll post you one of the 1mm thick shims so you can show it to your contact. Link to comment Share on other sites More sharing options...
Guest Posted January 25, 2014 Share Posted January 25, 2014 I have the asymmetric ones on my Roadsport SV : here Link to comment Share on other sites More sharing options...
Mankee Posted February 4, 2014 Share Posted February 4, 2014 Back on this one again. I've not gone outside to check my car, but can anyone see a need for the centre hole on the shims? Or even the bar in between where the rack clamps go? Or are they there for ease of manufacturing and to look pretty-ish? These shims by the way: http://caterhamparts.co.uk/img/p/1439-1439-thickbox.jpg Link to comment Share on other sites More sharing options...
Paul Deslandes Posted February 4, 2014 Share Posted February 4, 2014 I made separate shims for each end, slightly larger than the underside of the clamp to minimise any tendency to rock. I used 2mm and 1mm ali but, had I known the eventual thickness, I'd have used thicker pieces that added up to 9mm or machined them from a lump of solid metal. The thicker CC bottom halves is the best way of all. Edited by - Paul Deslandes on 4 Feb 2014 10:56:25 Link to comment Share on other sites More sharing options...
TomB Posted January 13, 2015 Share Posted January 13, 2015 Interesting reading. I'm fitting widetrack this winter and my rack is currently on my bench being cleaned up. On my narrow track set up, I just had the silver clamps holding the rack, no spacers or shims to lift the rack up. My clamps are the symmetrical clamps, which do not lift the rack up any more than standard. As I'm now going to have wider track rod ends, do I need to do anything with the height of the rack and fit aeon shims under the clamps? Link to comment Share on other sites More sharing options...
revilla Posted January 14, 2015 Author Share Posted January 14, 2015 Well to be honest I never went through the full and proper measurement procedure ... as everyone seemed to be coming up with the same result of 9mm I took a gamble, had some 9mm spacers made up by Mankee's contact and subjectively I'm quite happy with the results. Before I made the change I had a few scary moments where bumps and hollows in the road caused the car to kick alarmingly to one side; since making the change it's never done it once. It does seem more sure-footed over bumpy surfaces generally. At the same time it's lost nothing in terms of feedback and most of the time you wouldn't know the difference. As I say though I haven't done the measurements so I can't back up my claims with any hard data ... but let's just say I have no intention of taking the spacers out again. Link to comment Share on other sites More sharing options...
NedK Posted January 14, 2015 Share Posted January 14, 2015 For what it's worth, the 160 manual specifies bump-steer spacers under the rack. I realise that the skinny wheels may mean that the geometry on the 160 is a bit different.Ned Link to comment Share on other sites More sharing options...
TomB Posted January 14, 2015 Share Posted January 14, 2015 Does the same apply for the wide track suspension? I was think of simply buying some ali strip from B&Q in suitable thickness to make about 9mm, cutting it to length and drilling it, and sliding it under the clamps. Should be easy enough to take out again if it doesnt work. Link to comment Share on other sites More sharing options...
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