stevefoster Posted May 6, 2001 Share Posted May 6, 2001 Having had a bit of practise doing this now I though I might write up what / how we are doing DIY corner weighting. Nothing ground breaking but it seems to work is fun and very cheap to do... I can feel an article for LF coming on! I aquired 8 sets of Eks scales (Swedish make) from B&Q for £3 each. I made load sharing briges so that the weight of each wheel is spread over two scales. I don't have a level garage floor so large enough squares of wood are used at varying thicknesses for each of the 4 corners to achieve a level platform on which the car rests. The trick is to use a roller plate under one of the front wheels to take care of the suspension droop while you wind off the jack. If you don't do this the lateral force will wreck the scales.... Pop the driver in. Read off the scales. Input the data into the CW spreadsheet that is available on the 7 mailing list. This spreadsheet aims to get the fronts pretty much balanced with the driver in to make lockups more predicable. It also seems to sort out bad handling..more of that later on. The spreadsheet tells you how / what to adjust. It tells you the kg spread you are aiming for and how much to wind off or on the damper collars. Lowering the collar makes the wheel take less weight or pressure. Raising it increases the weight or pressure on the wheel. You can't shift weight about at all or even from front to rear. You can change the diagonal pressures or weights of the car effecting an as close as possible balance. Bellow are the 3 sets of data for 3 different cars we did yesterday. All cars are road going with the usual assortment of junk in them. Live axle 1600 XF 5speed Starting weights inc driver Front Right 148 Front Left 152 Rear Right 165 Rear Left 166 Driver weight 65kgs Spreadsheet ideas Kgs Change Kgs Adjustment req Actual after adj Front Right 148.94 0.94 0.24 Raise collar 149.50 Front Left 151.56 -0.94 -0.24 Lower collar 149.50 Rear Right 164.06 -0.94 -0.24 Lower collar 164.50 Rear Left 166.94 0.94 0.24 Raise collar 166.50 Total 631.50 630 Here the fronts are identical after adjustment. Ok we have 1.5 kgs inaccuracy and we were not much more than that out from the start..but fun anyway. I have yet to hear from the driver about handling or lock up tests... Bump steer from the rack being too high is his main problem... get those shims out! VXC Dedion Starting weights inc driver Front Right 170 Front Left 160 Rear Right 179 Rear Left 173 Driver weight 75kgs Spreadsheet ideas Kgs Change Kgs Adjustment req Actual after adj Front Right 168.87 -1.13 -0.28 Raise collar 169.00 Front Left 161.13 1.13 0.28 Lower collar 162.00 Rear Right 180.13 1.13 0.28 Lower collar 180.00 Rear Left 171.87 -1.13 -0.28 Raise collar 173.00 Total 682 684 So 2 Kgs out on total weight and fairly close to the ideals after the small adjust. This car had been set up 4 years ago and has only had the ride height adjusted for speed bump clearance...In other words I need not have bothered but again it was fun. Nothing to report on handling yet. As for the weight. I have a large fitted fire ext. and loads of tools and spares on board. Zetec Dedion (this car was miles off at start!) Starting weights Front Right 175 Front Left 142 Rear Right 177 Rear Left 189 (This car must have been a pig to drive and indeed put itself in the barrier at Cadwell last year!) Driver weight 100kgs Spreadsheet ideas Kgs Change Kgs Adjustment req Actual after adj Front Right 163.37 -11.63 -2.91 Lower collar 166 Front Left 153.63 11.63 2.91 Raise collar 154 Rear Right 188.63 11.63 2.91 Raise collar 185 Rear Left 177.37 -11.63 -2.91 Lower collar 180 Total 683 685 So 2 Kgs out total weight from first reading. We could not raise one of this cars rear collars enough since it was riding very low at the rear and was on max and really needed a spring compressor to reposition the circlip to allow more adjustment. The driver reports much better handling and wants to reset the damper heights and have another go... Link to comment Share on other sites More sharing options...
Swiss_Tony Posted May 6, 2001 Share Posted May 6, 2001 Steve The results look very promising! Where can I get the CW spreadsheet from? I was playing with a set of Longacre scales a few weeks ago and I want some! James Link to comment Share on other sites More sharing options...
ashaughnessy Posted May 8, 2001 Share Posted May 8, 2001 Let's say I wanted to try this on my garage floor - far from level. Do I need to create four level pads on which to place the scales, or can I place the scales on the floor and put things on top of the scales to shim up each wheel so that each wheel' contact point with the scales is at the same level? I assume the latter, because the corner weighting is all about getting rid of imbalances caused by the car rocking about one of its diagonals. How accurately do you need to get the levels? E.g. to the nearest foot [:-)], the nearest half centimetre, the nearest millimetre, etc? What about problems caused by the car not settling correctly on the springs each time you jack it up to adjust it? How do you make sure it settles back to the correct rolling ride height each time? Anthony Link to comment Share on other sites More sharing options...
stevefoster Posted May 8, 2001 Author Share Posted May 8, 2001 It should not matter if the scales are on top or at the bottom of the stack. Since most garages are rough concrete I would favour a flat square of wood first to give the scales something flat to rest on. The settling at the front is taken care of by the roller plate I have.... I give the car a couple of little bounces to normalise everything once on the platform. As for accuracies. The closer the better. I used a long straight edge and spirit level to see how much chocking each corner needed. This gets everything very level of course.... as good as levelling with a screed at any rate! After that it is pour on self levelling resins = expensive and even they have a miniscus (spelling?) effect... Good luck. Link to comment Share on other sites More sharing options...
Swiss_Tony Posted May 8, 2001 Share Posted May 8, 2001 Ideally the floor should be as level as possible. For example one complete turn of the platforms can raise or lower that corner by 5mm or so. One turn out can make a lot of difference. The most accurate way of putting a car on the scales is to roll it on and off with the driver etc in the car. After adjustments the car should be rolled and bounced and the steering moved to settle the suspension (while off the scales) and then re-checked. James Link to comment Share on other sites More sharing options...
Darryl S. Posted May 9, 2001 Share Posted May 9, 2001 I can't seem to find the CW spreadsheet on the mailing lists .ftp site - what file name is it listed under? Link to comment Share on other sites More sharing options...
Peter Carmichael Posted May 9, 2001 Share Posted May 9, 2001 Got the chance to cross-compare my "flat floor setup without a flat floor or special tools" technique with a set of corner weight scales when the Sevens list had a day out at the Emerald rolling road. I set up Roy Booths (W111FLY) car through a series of jacking and balancing exercises and then we plonked it onto the corner weight scales where the weights were as close to perfect as "sod it" is to swearing. 8 EKS (swedish) scales and a bunch of chocks seems to be a rather over-egged pudding compared to my recipe of two axle stands and a jack. (an extra jack or axle stand makes life significantly easier). Have a look at this and this. Link to comment Share on other sites More sharing options...
stevefoster Posted May 9, 2001 Author Share Posted May 9, 2001 Interesting Peter. I will have a go at this and see how it compares. Link to comment Share on other sites More sharing options...
Graham Perry Posted May 10, 2001 Share Posted May 10, 2001 I also am looking for a budget way to do the flat floor set up. I am currently investigating digital industrial weight pads as I have heard they are substantially cheaper than motorsport ones which all seem to be 4 figures to buy. If I find something sensible I will post it on here. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted May 10, 2001 Share Posted May 10, 2001 Please note my caveat: (The big assumption in this lot is that you don't have a corkscrew deformed chassis) Another way of thinking about it is that if the results are different to the EKS scales, then your chassis is bent... Link to comment Share on other sites More sharing options...
Mike Bees Posted May 10, 2001 Share Posted May 10, 2001 Graham - 3 figures is a possibility: http://www.budgetraceparts.co.uk/ Mike Link to comment Share on other sites More sharing options...
Graham Perry Posted May 10, 2001 Share Posted May 10, 2001 Mike, I am looking for something even cheaper. I am told GBP 250 should be possible. I will pass on what I find out. Link to comment Share on other sites More sharing options...
John Posted May 10, 2001 Share Posted May 10, 2001 You cant get cheaper than 4 sets of digital bathroom scales with plywood platforms. Available from all good Argos stores !! John Link to comment Share on other sites More sharing options...
_Tim_ Posted October 18, 2004 Share Posted October 18, 2004 Having just aquired 8 sets of el cheapo bathroom scales from Arrrrgoose, I'm keen to locate a copy of the CW spreadsheet mentioned in the first post of this thread. Can anyone mail me a copy? tim@academ-racer.com Cheers! - Tim - 2004 evo Caterham Academy, Group 2 Runner Up build diary here Link to comment Share on other sites More sharing options...
Jason Plato Posted October 18, 2004 Share Posted October 18, 2004 beware !!! I bought 8 scales from Argoose and there was a +/- 3Kg range across all 8 I took them back and bought 8 from IKEA . The rev limiter thought I was mad - checking all the scales in the store 😬 C7 TOPhere Link to comment Share on other sites More sharing options...
elie boone Posted October 18, 2004 Share Posted October 18, 2004 Steve, If you do so much corner weighing why not buy Longacre scales direct from Amerika they are half the UK list price. Beware that the Bat. charger is 110V unless u state that u need a 220v Link to comment Share on other sites More sharing options...
Joe 90 Posted October 19, 2004 Share Posted October 19, 2004 But beware the shipping and duty ☹️ SEP field working, not spotted in 102,700 miles. Some photos on webshots, updated 21 Sept Link to comment Share on other sites More sharing options...
philwaters Posted October 19, 2004 Share Posted October 19, 2004 Copy of the spreadsheet on my site, under Files. Phil Waters Link to comment Share on other sites More sharing options...
_Tim_ Posted October 19, 2004 Share Posted October 19, 2004 Phil - Tim - 2004 evo Caterham Academy, Group 2 Runner Up build diary here Link to comment Share on other sites More sharing options...
Mark Gregory Posted October 19, 2004 Share Posted October 19, 2004 Steve/Phil: What criteria did you use to establish your 'ideal' weights? I would have thought the weights on the front wheels would want to be equal. Also, do you take into account the 'rake' of the car. Thanks, Mark Link to comment Share on other sites More sharing options...
Joe 90 Posted October 19, 2004 Share Posted October 19, 2004 Rake doesn't affect corner weights. When I set cars up I set the left-right percentages so that they are the same for the front and rear axles. SEP field working, not spotted in 102,700 miles. Some photos on webshots, updated 21 Sept Link to comment Share on other sites More sharing options...
stevefoster Posted October 19, 2004 Author Share Posted October 19, 2004 I'm now on to a much more sophisticated roll on roll off method and bridging the load with the scales across the tyre width not inline. Much more repeatable readings and take a fraction of the time and effort to do it all. Can even accomodate SV's! As for the same weights at the front. Since the 7 is not a symetrical single seater its all a compromise. True I think that for front braking efficiency and lock up at identical points on a perfectly flat surface you could aim for equal front weights. However at the other end of the circuit you will be chucking the car in on a falling away camber and trail braking and will want the rear to behave predictably. So its a compromise. At the end of the day you have to set the car up in a way that suits you. The spreadsheet way seems to suit many people but a little circuit related tuning will always pay dividends at the extremes of handling / grip levels. For example with my cornerweights set up I would snatch a front right a little too easily at north bend at Lydden. 0.5 turn on the damper to give that corner more weight cured the problem and did not upset her in any other noticeable way. Hants (North) and Berkshire Area club site here My racing info site here Link to comment Share on other sites More sharing options...
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