A17KAR Posted June 14, 2004 Share Posted June 14, 2004 Hi All, I seem to suffer from severe understeer when pressing on and want to sort it. I am running 185/60/13 021's and have just ordered replacements in 185/70/13 as this seems to be the recommended fitment ( I want handling, not LOOKS!!) The Front nearside 021 is really scrubbed at the moment, far worse than the offside. Going hard into roundabouts the vehicle will runwide and has to be really provoked into oversteer. I am unsure of the camber set up and any Ideas will be gratefully recieved. The car is fitted with adjustable suspension ( Damping and Height) but I am unsure of age or brand. Could these be rebuilt? Also I do not know if it has been flat floored so I will be looking into this soon. Engine is 150bhp Crossflow, Quaife LSD. Thanks in advance, Craig. Link to comment Share on other sites More sharing options...
Steve Kirk Posted June 14, 2004 Share Posted June 14, 2004 Check tracking and camber. I put off doing this on my car for ages, but uneven tyre wear forced me to look at it. I kicked myself when I finally checked it, because it had been miles out for so long and cost me a few tyres in the process. The tracking was 1.75 in rather than 0.5 out. Once adjusted correctly, which took 15 mins, it drove like a different car. Understeer has vanished. Horrible vagueness near the limit has been replaced by eager and positive turn-in, and better straight line stability (previously, bumps on the road would make the car skip sideways). Camber was more or less correct on my car at -1.8 each side, although now I've run it for a while I find that the inside of the driver's side tyre is wearing, but the pips are still present on the outside, so I think I'll take some camber off back to the standard 1.5. The correct settings are in the manual, note that the settings vary depending on model and I think also on age, because the suspension setup has been changed at certain points. With adjustable platforms you can adjust rake. Higher rear means less understeer. You can also shift weight between wheels - if this is out your front end grip at the limit could be reduced. On a de dion you can choose two positions for the trailing arms. One gives less understeer than the other but I can't remember which. Manual will tell you. Link to comment Share on other sites More sharing options...
A17KAR Posted June 14, 2004 Author Share Posted June 14, 2004 Steve, Thank you, I dont have a manual, My car is 1985 Dedion axle Supersprint. Have you any Idea of wether the settings you mention will suit, I will get this checked and adjusted when I fit the new Tyres I orderded today (George Polley, How CHEAP!!!) Link to comment Share on other sites More sharing options...
Pelico Posted June 14, 2004 Share Posted June 14, 2004 Lots of things in the set-up will move the grip from the rear to the front: Stiffer rear ARB Softer front ARB More front toe out Softer front dampers/springs Harder rear dampers/springs Within limits - softer front tyre pressures Higher rear ride height. Do you know any of the settings for the above. Might be worth setting them all to the build manual and working on one at at time. I had huge amounts of understeer that I have cured with a softer front end and more front to rear rake. Best of luck, most of all enjoy the fiddling. That's what owning a Seven is all about. My Caterham owner's site Link to comment Share on other sites More sharing options...
MikeW Posted June 14, 2004 Share Posted June 14, 2004 I'd check to make sure you have around 15mm of rake first. What ARB are you running on the front? MikeW 1600 VX Black/Ali Race No 110 Link to comment Share on other sites More sharing options...
david nelson Posted June 14, 2004 Share Posted June 14, 2004 This is how I got it sorted. Payed Vertial 7and problem resolved. Things to look that anyone can do : rack front to back correct tyre pressure front ARB If you have the know how. Camber toe corner weight/flat floor Pelico has covered everything, I would start with the simple thing and see what it is like hope this help David Link to comment Share on other sites More sharing options...
RESOLVIWOLF Posted June 14, 2004 Share Posted June 14, 2004 as others have said, begin by checking front toe then rake likely common causes Link to comment Share on other sites More sharing options...
Steve Kirk Posted June 16, 2004 Share Posted June 16, 2004 Craig, Data for live axle from my assembly guide are below. However I'd recommend that you double check with Caterham, as it's possible that your earlier car might require settings different than those current at the time of my assembly guide (approx 1995). ride height front = 140mm ride height rear = 155mm (for live axle) Tolerance +/- 10mm These are measured at points on the chassis behind the front wheel /in front of the rear wheel. Measure from bottom of chassis rail to ground. It also says "ensure that the rear ride height is always approx 15mm higher than the front". Under "classic" (the alternative being "de dion") it says toe in front 0deg20" +/- 10" toe in rear 0 negative camber 0deg45" +/- 15" camber rear 0 Edited by - Steve Kirk on 17 Jun 2004 21:10:32 Link to comment Share on other sites More sharing options...
Irrelevant Posted June 16, 2004 Share Posted June 16, 2004 Errrr . .. isn't it toe in rather than out Had same problem with mine and toeing it in a tadge with less rebound damping helped a lot. After a hi-vis (pocketted side) driver's door if anyone's got one? Link to comment Share on other sites More sharing options...
Steve Kirk Posted June 17, 2004 Share Posted June 17, 2004 Adam, not sure what you mean by "isn't it toe in rather than out". Also you toeing it in might have felt better to you, if it was toed out too far to start with. If you change anything at all on your front suspension - (e.g. change damping, change ride height, new balljoints), this can throw the track out - I expect that this is how mine came to be 1.75 toed in in the first place. These fine adjustment are a matter of personal taste, and how much you notice the difference (if at all) can vary depending on other aspects of your overall setup (which includes setup of the rear suspension, overall weight of the car, etc). It's complicated, but one thing for sure, people seem to notice a change when it's made, even if they don't agree on what the change is or what the best setup is. For example, some people find a setup like mine unsatisfactory on the road because they complain of tramlining, but I don't find this to be a problem. The key thing is, try a few changes within sensible limits, and you'll find what you like best. Link to comment Share on other sites More sharing options...
Irrelevant Posted June 17, 2004 Share Posted June 17, 2004 Steve - what I meant was making the wheels more toe-in, i.e. shortening the rack width. I was just questioning what Pelico had said, i.e. "More front toe out". As you say, small changes can make a big difference - I'm sure my previous understeer problems stem from flat flooring. I never bothered rechecking the toe as the ride was only slightly changed and I'd just had the toe checked . . . Another lesson learnt the hard way 😳 After a hi-vis (pocketted side) driver's door if anyone's got one? Link to comment Share on other sites More sharing options...
Pelico Posted June 18, 2004 Share Posted June 18, 2004 Hi Adam, My tought on more 'toe out' was based on the received wisdom that a changing the front tracking from the build manual - a degree or so of toe in, to parallel or a touch of toe out will make the turn in sharper. Simon Lambert makes a strong recommendation for this on the Book-a-track Caterham FAQs that he appears to author ! Do you not agree ? Have I got the wrong end of the stick ? Is seems to have the effect on my car. Cheers, Peter My Caterham owner's site Link to comment Share on other sites More sharing options...
Moderate Clam Posted June 18, 2004 Share Posted June 18, 2004 Alternatively, you could just sort your driving out. It sounds like you are simply entering the corner too fast. remeber the old adage... slow in, fast out... 😳 Link to comment Share on other sites More sharing options...
Irrelevant Posted June 18, 2004 Share Posted June 18, 2004 Howdy Pelico: I think I got my info from one of Alan Stanforth's (? spelling) books on chassis design and setup. As with anything technical, I may be wrong 😳, but it seems to make sence when I consider what's going on. Moderate Clam: Slow in fast out ....The problem with understeer is that you can't go fast out as the bl00dy car pushes out. In my instance, I was getting understeer once the car had settled in a longer bend, that's all - no probs with hairpains when the weight was on the front under braking or in fast bends. Curborough was a nightmare, see this; see what I mean 😳, although this was confounded by knackered damper (and a sh1te steering wheel/seat linkage). As I said, toeing in the fronts and reducing the front rebound damping seems to have helped a lot - MIRA will tell for sure though - hope it's dry.... After a hi-vis (pocketted side) driver's door if anyone's got one? Link to comment Share on other sites More sharing options...
Moderate Clam Posted June 18, 2004 Share Posted June 18, 2004 The original post (which I was replying - obviously unclearly - to) was regarding entering round abouts. Link to comment Share on other sites More sharing options...
BigYin Posted June 18, 2004 Share Posted June 18, 2004 Pelico Sorry to come in so late. Everything you say makes sense to me and matches received wisdom except the bit about tyre pressures. Mike Costin & David Phipps' "Racing and Sports Car Chassis Design" p66 says: "Although a car's basic handling characteristics are decided in the drawing office, the degree of understeer or oversteer can be varied, within reasonable limits, by alteration of tyre pressure. It is not yet universally realised that - whatever the conditions - increased tyre pressure results in increased cornering power ...................... More air in the front tyres will either reduce understeer or increase oversteer" Can anyone tell me who's right? After all Mike Costin was, at the time, Development Engineer at Lotus Cars Ltd. Silver SV SSR Link to comment Share on other sites More sharing options...
Irrelevant Posted June 18, 2004 Share Posted June 18, 2004 Pelico: You were right, I was talking out of my 🙆🏻 wrt toe...... After a hi-vis (pocketted side) driver's door if anyone's got one? Link to comment Share on other sites More sharing options...
Pelico Posted June 18, 2004 Share Posted June 18, 2004 Adam, no worries, I was only repeating what others have said on BC. One point has always intrigued me, that is the "slow in fast out" maxim for Caterhams. Having a relatively slow Caterham (1.4 SS) it seems to me that on the track, to keep up with Scoobys and Portches, I can not out drag them on the exit from corners. I can certainly bleed in the power at little earlier than them, but I really need to carry mutch more speed into and throughout the corner. Hence a fast in, faster out policy. Any thoughts ??? Cheers. Peter My Caterham owner's site Link to comment Share on other sites More sharing options...
A17KAR Posted June 18, 2004 Author Share Posted June 18, 2004 Hi Guys, Thanks for all the info. In response to the slow in fast out the problem is when applying power after the car has settled. Not by me barrelling into the corner too fast. I now need some ball park figures for a 1985 Dedion chassis so I can make shure the castor, camber and tracking are as god intended before I start fiddling. Cheers Craig. *cool* Link to comment Share on other sites More sharing options...
Pelico Posted June 18, 2004 Share Posted June 18, 2004 Craig, The build manual is available on the web on http://www.caterham.uk.com/ It has all the info you need on basic set-up but is about 15mb. If you do not have a fast connection let me know and I can post the suspension set up details or just search for 'toe' they have been posted before on BC. Cheers Peter My Caterham owner's site Link to comment Share on other sites More sharing options...
A17KAR Posted June 18, 2004 Author Share Posted June 18, 2004 Pelico, Thank you, your a star *biggrin* Link to comment Share on other sites More sharing options...
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