Sue Dinnim Posted June 17, 2004 Share Posted June 17, 2004 Just a quick thought knowing that I see a lot of posts about the accuracy of Caterham speedo's. If the speedo over reads how fast you are going would that not mean it shows you are doing more miles than you actually are? If so where does that leave you on a limited mileage insurance policy because you will have done less miles than your speedo says. Link to comment Share on other sites More sharing options...
Graham Sewell Posted June 17, 2004 Share Posted June 17, 2004 On the principle of only needing a speedo in built up areas - ie not making progress - would it not be a great idea to have one that you culd switch off remotely. Plod won't twig it and it is there for MOT's etc - just don't show them the magic switch. This would then not cover areas of Golf Lima Foxtrot (be it roads or track)! In reality, the speedos are not that inaccurate unless mine is unusual. My point of reference is the 'slow down' signs that are triggered by radar. Assuming that they are correct, the lights go out when I decelerate (nasty idea) down to the displayed figure - although I havbe only tried this in 30 and 40 mph zones. Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
jackb_ms Posted June 17, 2004 Share Posted June 17, 2004 Mine overeads by 16%, with 205/45 at the back. If I change to 205 50 the speedo would be spot on, Ive been told Jack Emily, The Very Yellow 21 Link to comment Share on other sites More sharing options...
mav Posted June 17, 2004 Share Posted June 17, 2004 Hmmmm I have an electronic speedo (std caterham) with 16" 205/45's Up to 70 is is the same as the sigma bike speedo readings. After that things get a little strange. the speedo under reads. Check for a posting by me a week or so back for details of the different readings Link to comment Share on other sites More sharing options...
Myles Posted June 17, 2004 Share Posted June 17, 2004 Well I started out down the route of being miffed about losing 'real' miles on my limited mileage policy - and fitted a bike-speedo here... ...but then I found out that the increments on my policy for each extra mileage band were not horrific (£20 ish for each extra 2.5k above 5k on my MSM policy - until I broke the unlimited threshold) and stopped worrying about it. I did fiddle with the dip-switches on the back of the speedo fairly early on too - and with my 185/60R13 RE720s, the speedo is pretty much bang on (to the extent that I've 'lost' only a few hundred miles over the 13k+ I've owned the car. However, with my 175/55R13 CR500s, I couldn't get much better than a 7%ish inaccuracy (this was measured using the odometers on the speedo and bike comp - much more accurate comparison than at any particular speed - but as Mav has found out, the accuracy can vary according to speed anyway - so my figure is a weighted-average). Keep BC free and open for ALL. Membership No. 43xx Alcester Racing 7's Equipe - 🙆🏻™ Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Petrolhead Posted June 17, 2004 Share Posted June 17, 2004 Do you have any info re the dip switches? Now with SL No 148 Link to comment Share on other sites More sharing options...
Myles Posted June 18, 2004 Share Posted June 18, 2004 Lemme dig... My findings are in an e-mail somewhere (although I think I also posted them here at some point...) Back soonish. Keep BC free and open for ALL. Membership No. 43xx Alcester Racing 7's Equipe - 🙆🏻™ Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Petrolhead Posted June 18, 2004 Share Posted June 18, 2004 I'll have a search as well Now with SL No 148 Link to comment Share on other sites More sharing options...
Myles Posted June 18, 2004 Share Posted June 18, 2004 Right, I was told (by Mike Molloy): If you look at the back of the speedo under the rubber grommet, there should be a row of 4 dip switches labelled 1 - 4. Switch 1 sets the speedo cal to high or low ranges; switches 2 - 4 set the odometer cal. I would suspect that your car is still set to the configuration that would have got it through the SVA check wearing CR322s. This would be the "low" setting: Sw1 = OFF, Sw2 = ON, Sw3 = OFF, Sw4 = OFF. Try changing to the "high" setting Sw1 = ON, Sw2 = OFF, Sw3 = ON, Sw4 = ON. On 175/55R13 CR500's this appears to have resulted in: The dip settings you gave me are an improvement - but aren't perfect unfortunately. I just did 64.13 miles according to my bike computer - this came out as 66.3 miles on the odo (i.e. 3.4% overreading - I was getting about 7-8% before). The speedo was a bit harder to get an accurate crossreading - but 40mph (indicated) appeared to be about 38.5 (3.9%) and 60 was about 56.5 in reality (6.2%). I'll try and get a better reading sometime soon on one of the bypasses. These figures are an improvement over the average of 10% I had before. Hope this helps - but there are so few settings that you can't go too far wrong... Keep BC free and open for ALL. Membership No. 43xx Alcester Racing 7's Equipe - 🙆🏻™ Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Area Representative z7 Posted July 5, 2004 Area Representative Share Posted July 5, 2004 *confused*Speedo dip switches ❗ Myles, is this the only information you have for setting the dip swicthes? Do you (or anyone else) know where one get the full details? There are other combinations of the switches, so do they make any difference? Currently, my speedo is reading 40 at 33ish! And wavers generally! Adil Edited by - Adil on 5 Jul 2004 16:38:51 Link to comment Share on other sites More sharing options...
Colin Mill Posted July 7, 2004 Share Posted July 7, 2004 How about using a hand-held GPS as the reference? I think most of them have a page which displays speed over the ground. I guess they would have to be accurate given the position accuracy of GPS Link to comment Share on other sites More sharing options...
evotell Posted April 14, 2014 Share Posted April 14, 2014 My speedo is reading 80KM when in reality the cars doing 120KM according to my GPS. 😳That's outrageous, any suggestions would be most appreciated. Link to comment Share on other sites More sharing options...
Jonathan Kay Posted April 14, 2014 Share Posted April 14, 2014 Letraset, but it won't correct the odometer. Jonathan Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted April 15, 2014 Share Posted April 15, 2014 Quoting evotell: My speedo is reading 80KM when in reality the cars doing 120KM according to my GPS. 😳That's outrageous, any suggestions would be most appreciated. Terry, if you have the new type of Caterham/Caerbont electronic speedometer, then you can use this procedure to adjust the calibration here. When in calibration mode, note the value that is flashing (the number of pulses per mile or kilometre), then determine the number of pulses that the value should be by taking current_setting multiplied by displayed_speed divided by actual_speed. Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted April 15, 2014 Share Posted April 15, 2014 What sort of speedo do you have ..... older = mechanical drive, in which case it's down to the speedo drive gear in the side of the gearbox. Newer = various types of electronic speedo. One with 4 DIL switches (like my 2002 car), one with ten switches, and one with nothing internal, but the ability to programme a 4-digit code from the rubber button in the display glass. On mine and a 2003 car I worked on last month, the 4 switches were all set the wrong way. Reversing them brought the accuracy in line with a GPS speedo. plenty of threads on these settings if you do a search .... perhaps for 'speedo and setting' or 'speedo and switch' Link to comment Share on other sites More sharing options...
revilla Posted April 15, 2014 Share Posted April 15, 2014 @evotell: Letraset as suggested by Jonathan - but only to change the letters "KPH" to "MPH" - that should get you within 10% 😬 Edited by - revilla on 15 Apr 2014 07:31:27 Link to comment Share on other sites More sharing options...
john milner Posted April 15, 2014 Share Posted April 15, 2014 Based on my Sat Nav and roadside speed indicators I would say my speedo over-reads by 3mph at 30mph. I hope I'm right as I was gunned on sunday. Link to comment Share on other sites More sharing options...
AntonyH Posted April 15, 2014 Share Posted April 15, 2014 Quoting SM25T: one with nothing internal, but the ability to programme a 4-digit code from the rubber button in the display glass. Ooh!! Mine has no dip switches so I'd just assumed it was not adjustable, however it *does* have said rubber button on the front. Do you have any reference docs on how to reprogram this type? Mine reads 60mph at 50, which is good for reference, but is a 20% over-read which would be nice to be able to correct. Thanks in advance! Link to comment Share on other sites More sharing options...
Jonathan Kay Posted April 15, 2014 Share Posted April 15, 2014 Does this thread help? Jonathan Link to comment Share on other sites More sharing options...
AntonyH Posted April 15, 2014 Share Posted April 15, 2014 It does, thanks - as does this thread I also found when doing a suitable search, i.e., "from the dawn of time" rather than just the last X months/years. Cheers, I'll be giving that an investigate later. Link to comment Share on other sites More sharing options...
michaeljclark Posted April 15, 2014 Share Posted April 15, 2014 If anyone wants them, I've got the docs (I believe from Caterham) with the settings for the 10 DIP switch version of the speedo (MPH only), and the electronic newer style - sensor on rear wheel (MPH and KMH) Just BM me with which one you'd like. I used them plus a dual carriageway, to get my electronic one so that it matched it's speed reading against Tom Tom & Garmin Satnavs. Obviously, you use at your own risk etc etc 😳 Perhaps it's something that should live on BlatChat as a reference point, as this topic comes up fairly regularly 🤔 Cheers Mike Edited by - michaeljclark on 15 Apr 2014 11:32:05 Link to comment Share on other sites More sharing options...
Jonathan Kay Posted April 15, 2014 Share Posted April 15, 2014 Quoting michaeljclark: Perhaps it's something that should live on BlatChat as a reference point, as this topic comes up fairly regularlyYes, we need a technical wiki. Jonathan Link to comment Share on other sites More sharing options...
evotell Posted April 15, 2014 Share Posted April 15, 2014 Thanks guys, as has been said this appears to be a real problem for many people. cheers Link to comment Share on other sites More sharing options...
John Vine Posted April 15, 2014 Share Posted April 15, 2014 Quoting evotell: My speedo is reading 80KM when in reality the cars doing 120KM according to my GPS. 😳That's outrageous, any suggestions would be most appreciated.What year/model is your car? If you have the latest programmable speedo (no dipswitches), I can send you a list of the 6-digit program codes for a variety of tyres and wheel sizes. (I think the list came from CC originally.) JV Link to comment Share on other sites More sharing options...
evotell Posted April 15, 2014 Share Posted April 15, 2014 Quoting John Vine: Quoting evotell: My speedo is reading 80KM when in reality the cars doing 120KM according to my GPS. 😳That's outrageous, any suggestions would be most appreciated.What year/model is your car? If you have the latest programmable speedo (no dipswitches), I can send you a list of the 6-digit program codes for a variety of tyres and wheel sizes. (I think the list came from CC originally.) JV Hi John Thanks for your offer to send me the appropriate code. I spoke with Derek at Caterham and he sent me a code that I have inserted into the speedo. Once I drive it we will see. 😬 Thanks Link to comment Share on other sites More sharing options...
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