jackb_ms Posted June 13, 2003 Share Posted June 13, 2003 I have an old fashion speedo which i've just change the cable (las night). This morning travelling to work it was indicating a 120mph @ 4000 rev which is not possible as in fith the ratio is 25mph per 1000 rev. this is nearly a 16% error. Is there a way of recalibrating a speedo? Jack Link to comment Share on other sites More sharing options...
Dave H Posted June 13, 2003 Share Posted June 13, 2003 The speedo ratios are changed at the gearbox end - there is a gear which the end of the speedo cable fits, and it will need changing - but the gearbox will have to come out to do it. I don't think there is a way of recalibrating the speedo itself, although VDO may do it for you - at a price Did the speedo read correctly before you changed the cable? Dave H Link to comment Share on other sites More sharing options...
I.Mupferit Posted June 13, 2003 Share Posted June 13, 2003 I have had exactly this problem on mine and the speedo is presently being re-calibrated by Speedy Cables in Swansea (01639-732213) for £40.00 I figured it was easier to pay this than take the engine/gearbox out again to change the drive gears and at least the speedo should be accurate for the first time ever. The information they will need from you is:- 1) The distance between the centre line of the driven wheel and the ground with the tyres at normal running pressure. 2) Disconnect the speedo and put a bit of masking tape on the cable end to act as a pointer then make a chalk mark at the lowest point on one of the back tyres and push the car along counting 6 rotations of the wheel. At the same time count the number of revolutions of the cable and give this to Speedy expressed as portions of a clock face i.e. 6 hours 50 mins. Then send it off with this info and you should have an accurate speedo for a change. Brent Link to comment Share on other sites More sharing options...
ChrisC Posted June 13, 2003 Share Posted June 13, 2003 Speedy Cables, is a company in London that can recalibrate the Speedo, cost about £25 last time I had it done, but that was a few years ago. Sorry I no longer have the phone number, but try here here Link to comment Share on other sites More sharing options...
I.Mupferit Posted June 13, 2003 Share Posted June 13, 2003 The instrument division is now in Swansea and it is now £40 for a Caterham speedo. I know 'cos they are doing mine at the moment. Brent Link to comment Share on other sites More sharing options...
Nigel Riches Posted June 13, 2003 Share Posted June 13, 2003 I don't think that by just changing the speedo cable the calibration should be upset, more than likely the end of the cable that fits in the speedo is inserted deeper than the original, this could have the effect of moving the rotating magnet closer to the drag cup, therefore bringing a greater deflection to the pointer, and hence the error you describe. At the speedo end of the cable should be a brass ring, or collet of some sort, to stop the cable moving up into the instrument, if you still have the old cable make a comparison of the lengths of cable from collet to the short end, if the new one is longer carefully remove the excess, try to ensure the cable doesn't start to fray, then refit and see what happens, this would hopefully be easier and cheaper than recalibrating the speedo, and besides, what are you going to do when the speedo accuracy is found to be satisfactory? Hope this has helped, regards Nigel. 1982. 5 speed, clamshells. B.R.G / Ali. The True Colours. Link to comment Share on other sites More sharing options...
Pierre Gillet Posted June 15, 2003 Share Posted June 15, 2003 Jack, is it difficult to replace the cable? Cheers Pierre Link to comment Share on other sites More sharing options...
Gridgway Posted June 15, 2003 Share Posted June 15, 2003 easy to change the cable. You can unscrew the top by hand from the back of the speedo. I do the bottom end by taking the circlip out underneath, removing the right angle assembly (which falls on you at this point) and unscrewing the cable. It may be poss to unscrew the cable with the right angle drive still attached to the gbox. Circlip pliers are needed to take out and replace the circlip. Graham Just in case...make sure that the car is secure on axle stands before getting underneath it! Link to comment Share on other sites More sharing options...
Pierre Gillet Posted June 15, 2003 Share Posted June 15, 2003 Thanks Graham. Seems easy? No problem to "slip" the cable from the speedo to the box (if you understand what I mean. Cannot find the right words!)? Cheers, Pierre Link to comment Share on other sites More sharing options...
Gridgway Posted June 15, 2003 Share Posted June 15, 2003 Hi Pierre, the cable is just routed down past the gbox/bell housing. Certainly not a problem to take the old one out and route the new one in. Graham Link to comment Share on other sites More sharing options...
Pierre Gillet Posted June 16, 2003 Share Posted June 16, 2003 Thanks Graham again! Just ordered a new cable. I had ordered a new angle drive and found that the cable is blocked and cannot spin. This is my last attempt before moving to electronic speedo with magnetic drive! Cheers, Pierre Edited by - Pierre Gillet on 16 Jun 2003 07:21:29 Link to comment Share on other sites More sharing options...
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