Pendennis Posted March 2, 2017 Share Posted March 2, 2017 The rear ARB if left connected could prevent the suspension from releasing thus not allowing the chassis to settle in it's unladen or laden state. This also applies to the front ARB although the ball/socket isn't as bad as the drop links situated on the rear. However, I always loosen the front ARB bolts so its free to move. All bolts through all bushes front and rear should also be undone allowing the bushes be free in relation to pick up points on chassis, this is same scenario as the ARB being free as if left tight they will aid the spring on the damper and not allow you to achieve the best result. So, put weight of driver in seat, undo all bush bolts, as well as front and rear ARBs then do your adjustments and when finished re connect (adjust) rear ARB to suit and resecure all bush bolts, all before removing the drivers weight from the seat.There are many theories regarding set up, personally I adopt the above before setting rake and ride height. Then with aid of spirit levels I get the front chassis across crucifix completely level whilst getting the rear bulkhead completely level, thus the car is level with equal ride height across rear as well the equal height on the front. I then put car on scales and trim accordingly but note it is generally near to an equal set up just be doing this procedure, so much so that putting her on scales is nearly always a waste of time. Link to comment Share on other sites More sharing options...
elie boone Posted March 2, 2017 Share Posted March 2, 2017 Normally the ride height is set without any weight in any seat, you set the damper platform equal at the front, the same goes for the rear initially but to compensate the driver you mount the driver side platform 2 turns. In general this won't be far off when on the corner weight scales.The amount of rake depends on the type of spring that is used, 15 mm for linear springs and 35 mm for progressive springs.and to set the corner weights i just sit in the car with the display right next to me. Link to comment Share on other sites More sharing options...
Pendennis Posted March 2, 2017 Share Posted March 2, 2017 Blimey Elie, what is the point doing any static settings without any weight in the car?The whole point is to get a stable near as possible level car when laden Link to comment Share on other sites More sharing options...
elie boone Posted March 2, 2017 Share Posted March 2, 2017 The setting without weight is a good basis to start with the corner weights ( courtesy of G.May ), a person of 75 kg is totally different from 75 kg worth of bags in any seat. When i do corner weight i sit in the car with the corner weight display right next to me on a stand so i can see the weight by corner, by diagonal or by axle. Link to comment Share on other sites More sharing options...
Pendennis Posted March 2, 2017 Share Posted March 2, 2017 I totally disagree sorry, cannot see any reason why you would waste your time doing static setting with an unladen car then either put weight in or sit in it, very strange approach. Also, the way I put 75kg of ballast in drivers compartment is identical to a 75kg driver sitting in the car. Agree, just plonking 75kg bags of cement in seat isn't ideal I agree but that is NOT what I do.I also find it hard to understand how you could specify the rake must be this or that without checking it's weight across axles, or knowing C.O.G, roll axis etc.. Stipulating generic settings is not something I would do! Link to comment Share on other sites More sharing options...
elie boone Posted March 3, 2017 Share Posted March 3, 2017 The rake settings are Caterham data, i guess they got it trough development rather than a random number. Link to comment Share on other sites More sharing options...
Pendennis Posted March 3, 2017 Share Posted March 3, 2017 Doesn't mean it's right for Tom does it?Caterham would of done R&R and have found a figure that enables them to send their cars out the factory, that is all, but this generic figure which maybe okay for some will not be for others. If you think about it a Caterham could seat one or two occupants, driver or passenger could be 60kg - 100kg, could be 6'3" or 5'4 tall, car could carry a spare wheel, the engine and gearbox variant could differ let alone many variants in the chassis's that have been sent out. Obviously driver weight and height is common variant as well as chassis variants but there are quite a few significant factors that result in differing weight position within the chassis, hence my comments. In my experience which is only track based, there is no rule of thumb it's trial and error to find a happy medium, but sometimes we often drop or raise the rear due to other factors. A road car is a different subject I do appreciate that, so a generic setting maybe acceptable, I just find it difficult to accept that's all.My current car has 17mm of rake, my previous car which had an identical engine, gearbox, diff, spring rates, ARB's and ancillaries didn't require any rake whatsoever, dead flat level car. The only difference between the two cars was age of chassis, so work that out Link to comment Share on other sites More sharing options...
CheshireCat Posted March 3, 2017 Share Posted March 3, 2017 I would be interested to know how you place your ballast in the car to replicate a driver? Link to comment Share on other sites More sharing options...
Pendennis Posted March 3, 2017 Share Posted March 3, 2017 Your need two corner weight scales sitting on the floor raise one higher than the other to replicate difference in height between bum and heels of feet. Sit on higher one with feet resting on other, simulate seating position and record weight on both scales. Put weight in position of car as you recorded it, most of bum weight would obviously sit in base of seat but you can stagger it simulating your back. Won't be spot on to the nearest ounce but you won't be far away Link to comment Share on other sites More sharing options...
TomB Posted March 5, 2017 Share Posted March 5, 2017 Thanks for all your comments and thoughts. I've been trying to get this sorted for the last few evenings and have just spent another two hours on it.Current readings are FR 133mm; FL 134mm; sump 73mm; RR 151mm; RL 155mm. Right side rake is 18mm and left is 21mm. All with 75kg sand plus two wheels & tyres to take to ~80kg. My measurements have gone from 80mm on sump and 140mm across the front axle, but I'm really struggling to get the rake down to 15mm. I drop the back end down and the sump drops. I'm adjusting both sides of an axle to adjust, but doesn't seem to be working. Now the car is unloaded, there is a slight droop on the front right wishbones, but seem level when loaded. Any suggestions how I proceed? Link to comment Share on other sites More sharing options...
Mark w Posted March 5, 2017 Share Posted March 5, 2017 Are you measuring corner weights ? If not I would get yourself off to one of the better race teams and get them to set it up for you . Won't cost an arm and a leg . Link to comment Share on other sites More sharing options...
Pendennis Posted March 5, 2017 Share Posted March 5, 2017 Tom, you haven't done bad so I wouldn't change anything else without trying it on the road. But why you aiming for 15mm rake? Link to comment Share on other sites More sharing options...
TomB Posted March 5, 2017 Share Posted March 5, 2017 Not doing corner weights, just trying to get ride heights and rake sorted. I'm aiming for 15mm as that seems to be the consensus for linear springs. I've emailed Gemzoe Motorsport near Wakefield to see what they think. As it's mostly road use, I wasn't intending to go to the nth degree on set up, just corner heights, sump and rake and level across each axle. But I'm struggling/ getting impatient and am minded to leave it as it is for now. Ill load up the car again when wifey is watching Call The Midwife and remeasure. What do you think of the slight droop unloaded with the wishbones? Link to comment Share on other sites More sharing options...
TomB Posted March 5, 2017 Share Posted March 5, 2017 Been out and remeasured and rechecked my weight and put in 75kg plus one wheel rather than two. Ride height as follows now: FR 139mm; FL 139mm; RR 155mm; RL 157mm; sump 80mm. Rake RHS 16mm, LHS 18mm. So that's pretty good I reckon, although the 2mm out across the rear axle is annoying. I'm not sure I want to mess with it now. My other measurement point on the two front lower wishbone bolt heads is 198mm on each side. However, my front right lower wishbone does visually droop a touch, measured about 1cm across its width. Do I need to worry about this? It is a consequence of the 55 profile tyres and adjustment for 80mm sump clearance? If I dropped the front by say 5mm I'd probably loose the droop. The front springs compressed are ~60mm on the LH and 2-3mm less on the RH. Seems I get better measurements when the car has sat still for a couple of hours. I found the same before I started adjustments earlier this afternoon. Link to comment Share on other sites More sharing options...
Pendennis Posted March 5, 2017 Share Posted March 5, 2017 You have compressed the springs by 60mm?what is ride height from underside chassis to ground at rear of front wheel? Link to comment Share on other sites More sharing options...
TomB Posted March 5, 2017 Share Posted March 5, 2017 No, my bad description. The 60mm is from the top of the spring to the end of the threaded section. Just a reference measurement from side to side so I can see their relative adjustment to one another. The measurements are the FR & FL above - so 139mm each side. Link to comment Share on other sites More sharing options...
Pendennis Posted March 5, 2017 Share Posted March 5, 2017 Blimey engine hangs well down doesn't it.. go and try it would be my advice, you should be aware camber and toe of wheels should be correct leaning to an aggressive manner to feel any benefit by making adjustments such as the ones you've undertaken Link to comment Share on other sites More sharing options...
TomB Posted March 5, 2017 Share Posted March 5, 2017 It's dry sumped so the sump pan is shallower than a wet sump K. This allows the car to run lower and keep 80mm under the sump. I guess with a wet sump I'd only have 60mm clearance. The camber & toe where set when I fitted widetrack a couple of years ago, but now I've lowered it and fitted the new dampers I guess I should have it looked a it again. It might be easier to throw a couple of hundred at it and get it setup properly! Link to comment Share on other sites More sharing options...
Pendennis Posted March 5, 2017 Share Posted March 5, 2017 Try it first, after all your using car for Road so may not be far out, if your track based then probably well worth spending the money. Regarding your droop comment I've not noticed any difference between level or below droop so I run mine as low as possible ignoring level wishbones Link to comment Share on other sites More sharing options...
TomB Posted March 7, 2017 Share Posted March 7, 2017 Simons post in #12, The front has a Motion Ratio of approx 0.6 so yeas as above but the rear its closer to 0.8.Do I multiply or divide by the motion ratio to get variation? Does 1mm turn on the rear platforms equal 0.8mm or 1.25mm height change? Link to comment Share on other sites More sharing options...
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