Moliver Posted May 15, 2020 Report Share Posted May 15, 2020 When I have bought my car, it had 185 (80) 15 tyres installed. They look "impressive" on a TR2 but I decided to go back to the original size . Actually almost original, as I have decided to go for 185 -70- 15 Dunlops. Still all right for me, as 185-17 do have the same diameter and rolling circumference as the original 165x80. So, wider but original rolling circumference (185x0,7 = 130 <-> 165x80=132). Now I realized, that the speedo is not inidicating correctly. I therfore conclude, that someone has adjusted it to be in line with the 185 (x80 = 148) Diameter fitted earlier So now finally my question: How can the speedo be adusted to the tire size ? Are there different speddo drive configurations availabe ? Input welcome Cheers Oliver Quote Link to post Share on other sites
ijonsson Posted May 15, 2020 Report Share Posted May 15, 2020 You maybe already done this, but before worrying about speedo not reading correct, why not check the reading of your speedometer with an GPS speedo? Quote Link to post Share on other sites
Lebro Posted May 15, 2020 Report Share Posted May 15, 2020 Can you read the "Turns per mile" number printed in small characters under the odomebter readout ? that will tell you if it is an original "standard" speedo. It would normally read close to 1180 (in miles) or 740 ( in Km) assuming your axle ratio is 3.7:1 Bob. Quote Link to post Share on other sites
brian-nz Posted May 16, 2020 Report Share Posted May 16, 2020 Hi All On my TR3 the speedo recording is close to GPS reading but the distance recorder is not reading right (reads low). standard speedo 1180. I think my diff is 4.1. Tyres 165s. Would the diff make a difference to the distance recorder or would it be something else. (sorry to hijack this thread) Brian Quote Link to post Share on other sites
iain Posted May 16, 2020 Report Share Posted May 16, 2020 The speedo for a 4.1 axle is 1300. Iain Quote Link to post Share on other sites
Lebro Posted May 16, 2020 Report Share Posted May 16, 2020 4 hours ago, brian-nz said: Hi All On my TR3 the speedo recording is close to GPS reading but the distance recorder is not reading right (reads low). standard speedo 1180. I think my diff is 4.1. Tyres 165s. Would the diff make a difference to the distance recorder or would it be something else. (sorry to hijack this thread) Brian Yes it certainly would make a difference. the fact that your speedo reads close to GPS is either good fortune, or someone has tweaked it. Bob. Quote Link to post Share on other sites
Hamish Posted May 16, 2020 Report Share Posted May 16, 2020 On another thread running at the moment a company jdo offer 2 prices to recalibrate a Speedo one for just speed correction and another to do the odometer as well. suggesting your Speedo May have just had speed correction carried out. H Quote Link to post Share on other sites
Charlie D Posted May 16, 2020 Report Share Posted May 16, 2020 11 hours ago, Lebro said: Can you read the "Turns per mile" number printed in small characters under the odomebter readout I wonder if the TPM number on the speedo face is altered if it has been sent away for recalibration at any time in the past. It would take a very skilled hand and fine paintbrush to produce anything like an acceptable result. There must be people reading this who have had a recalibration done. Did they alter the number? Charlie. Quote Link to post Share on other sites
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