edmandsd Posted July 15, 2002 Share Posted July 15, 2002 When I converted my car to wide track recently and rose jointed the top and bottom wishbones aswell as the shocks, I calculated the change in wheel rate as a result of increasing the angle of the shock and changing the comparative mounting point relative to the raod wheel. I therefore increased the spring rate from the existing 250lb to 350lb which resulted in the same wheel rate. However the front of the car ended up being ridiculously soft even with the same shocks, harder springs and same wheel rate (Correctly calculate I might add). What we found was that the shocks were designed for rubber bushed vehicles and replacing them all with rose joints meant the shock absorber was effectively doing all the work whereas before the bushes were effectively helping to damp the wheel movement. Once I changed the shocks to a much harder variety the problem was solved and the suspension movement is how it should be i.e. The shock's doing all the work. This must mean there is far better wheel movement relative to the road with a fully rose jointed set up. Link to comment Share on other sites More sharing options...
wg_mulholland Posted July 15, 2002 Share Posted July 15, 2002 Absolutely. You want as much shock movement per mm of wheel travel as possible (look at the Nik link on a radical!) and replacing rubber with rose joints will do this. I just struggle to understand why the origional shocks were wrong. As far as I understand, rubber bushes have little damping effect and so replacing with rosejoints should have stiffened the front damping. Perhaps it is something to do with the nose over force of the dampers? With the rose joints every little ripple would have the shocks in motion and so already have overcome the initial resistance force- whereas the rubber bushes may have been absorbing these before and so the shock stays stationary- and hence when the bump/corner comes it still has to overcome the nose over force. Or is it something to do with resistance to movement- The rosejoints move freely and unrestricted whereas the bushes must be compressed and deflected and so have a higher amount of stiction- so by removeing them you effectively reduce the effective level of damping? So replacing the stiction with nicely extra damped dampers should overwhelmingly improve things? Does it? Has anyone got any better theories- I'm struggling! Link to comment Share on other sites More sharing options...
wg_mulholland Posted July 15, 2002 Share Posted July 15, 2002 Ignore all that last lot- I think I've got it! When you went widetrack you hasd to replace the springs with stiffer ones to keep the same effective wheel rate. So one inch wheel travel meant X ponds resistance in both cases. But when you went widetrack, you reduced the effect the dampers had on the wheel too as one inch wheel travel/second now means less resistance as the shock will have travelled less far in the same time (ther reason for the stiffer springs- remember). So the car will be less damped! This means that all cars changed to widetrack that kept their origional shocks will be less damnped. Has anyone else noticed this effect? Sort of ruins caterhams claim to having bespoke bilstein shocks- they'd be bespoke for narrowtrack but not for wide surely? Bill Link to comment Share on other sites More sharing options...
edmandsd Posted July 16, 2002 Author Share Posted July 16, 2002 Bill - I'm more inclined to agree with your first post. My car originally had basic live axle single link suspension. When you jacked the car up and removed the road wheel the suspension movement was appalling with the rubber bushes all binding etc. This obviously made the suspension feel a lot stiffer than it should of. I was originally using the post 91' vauxhall race 2.25 bilsteins which most people consider as very stiff when in reality they're actually very soft. Link to comment Share on other sites More sharing options...
Mike Bees Posted July 16, 2002 Share Posted July 16, 2002 Bill's 2nd post is *correct* in that the damping at the wheel will be affected by the damper angle in exactly the same way as the wheel (spring) rate. So if the change to wide track required your springs to be 1.5 times stiffer to get the same wheel rate then your dampers will need to be 'stiffened' by a similar ratio. Mike Link to comment Share on other sites More sharing options...
edmandsd Posted July 16, 2002 Author Share Posted July 16, 2002 Yes I see now. The combination of both factors would, as Bill suggests, question why Caterham recommend using fixed rate Bilstein dampers for all applications, unless of course they recommend they're re-valved for wide track conversions. Link to comment Share on other sites More sharing options...
ECR Posted July 16, 2002 Share Posted July 16, 2002 A bit of both I think When I rosejointed my front suspension and before I fitted the dampers/springs it was a real pleasure to move the suspension through its full deflection by hand. (so much so that Barbara had to keep an eye on me in case I got carried away !). By comparison the rubber bushed set up was horrid. The rubber bushes must surely make the suspension "stiffer" by comparison. I moved the top mounting for the damper outboard to compensate for the increased track. Link to comment Share on other sites More sharing options...
ashaughnessy Posted July 16, 2002 Share Posted July 16, 2002 Maybe the rubber bushes make things stiffer but does it matter as long as you choose dampers and springs to match the rubber bushes? Link to comment Share on other sites More sharing options...
edmandsd Posted July 16, 2002 Author Share Posted July 16, 2002 Think we've come full circle here - My findings would indicate that the Caterham bilstein shocks are designed for rubber bushed suspension, which would in all reality satisfy the majority of us. In fact I presume Caterham have invested a lot of time and money determining the damper settings for the suspension set up on their cars. Link to comment Share on other sites More sharing options...
Morls Posted July 16, 2002 Share Posted July 16, 2002 Just to complicate matters, what about the ARB. Is this thicker, (as it should be to maintain the same rate assuming it's longer) on widetrackquestion.gif Apparently rose joints make live axles appear softer too, particularly in roll. Anyone tried itquestion.gif Mark Link to comment Share on other sites More sharing options...
elie boone Posted July 16, 2002 Share Posted July 16, 2002 Dave, The angle the shocks are operating on a wide track are IMHO at there limit because the mouvement is marginal but this has been discussed before. The more mouvement you get the easy'er it is to control the mouvement. But the suspension set up will always be a compromise between front & rear grip. Link to comment Share on other sites More sharing options...
Tonycaterham Posted July 16, 2002 Share Posted July 16, 2002 Dave, Sighly retrograde step on this thread, but I understand (from the postings) you have a live axle car converted to wide track suspension. I have live axle car which I would like to convert to wide track...is it feasible??? Mail me offline is you wish. Regards Tony Link to comment Share on other sites More sharing options...
edmandsd Posted July 16, 2002 Author Share Posted July 16, 2002 You have mail Tony. Cheers Dave Link to comment Share on other sites More sharing options...
EFA Posted July 17, 2002 Share Posted July 17, 2002 When you change the springs for a harder type you need to increase the damping pro-rata. This is why decent dampers are adjustable for bump/rebound. No other reason. Fat Arn Visit the K2 RUM siteid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
edmandsd Posted July 17, 2002 Author Share Posted July 17, 2002 I agree Arnie but Bilstein is still a very good make - Much better than something like Spax which are often adjustable but nevertheless cheap and nasty - Mike Barnby showed me the inside of a trakspax recently and it really wasn't very impressive ! Link to comment Share on other sites More sharing options...
EFA Posted July 17, 2002 Share Posted July 17, 2002 I'd say the reverse, but then I binned Bilsteins for Trakspax around 3 years ago. If I was concerned I could dyno them, but then I'm not. Fat Arn Visit the K2 RUM siteid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
edmandsd Posted July 17, 2002 Author Share Posted July 17, 2002 Honestly didn't realise you were running Spax set up Arnie - I suppose they can't be that bad if Thrust SSC used them teeth.gif Link to comment Share on other sites More sharing options...
captain chaos Posted July 17, 2002 Share Posted July 17, 2002 I'm on Trakspax aswell and I didn't find them cheap. However, I cannot vouch for the internal build quality because i haven't seen inside one. What was so bad compared to Bilstein? Link to comment Share on other sites More sharing options...
DaveK Posted July 17, 2002 Share Posted July 17, 2002 As with all products things are built to a price. Bilstein do make some extremely nice triple adjustable alloy bodied dampers with remote reservoirs ,but at 1500 quid each they are beyond the means of all but the most dedicated race teams. All the ranges of 250 pound dampers are of an equal quality in regards to build quality materials used etc its only when you pay min 500 pounds per damper that the quality is unquestionable. Bill is right that damping rate will have to be increased with shock angle,the roll bar rate will also be dependant on the length of the lever arms Dave Link to comment Share on other sites More sharing options...
captain chaos Posted July 17, 2002 Share Posted July 17, 2002 Atleast in this price range they are rebuildable which is something I will have done this winter to change the damping range. Link to comment Share on other sites More sharing options...
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