Ian Evans Posted October 8, 2016 Report Share Posted October 8, 2016 I have a conundrum re. the speedometer calibration on my TR4A. Which one would read faster and therefore be less accurate? One with 1184 along the bottom of the face or one marked 1152? The current one, (marked 1152) reads about 9% too fast, but I have unearthed a spare marked 1184 with my handwritten sticker on it saying 'ok but reads fast'. Before I fit it some clarification would help! All info. gratefully received! Ian Evans Quote Link to post Share on other sites
TR5tar Posted October 8, 2016 Report Share Posted October 8, 2016 (edited) I wouldn't have a clue how to answer your question Ian, but if you've not seen this link regarding speedo calibration, then it might be of some use to you ...http://triumph.daveola.com/NOTES/Speedo_Repair.pdfDarren Edited October 8, 2016 by TR5tar Quote Link to post Share on other sites
Lebro Posted October 8, 2016 Report Share Posted October 8, 2016 Ian. Changing from 1152TPM (turns per mile) to 1184TPM would result in a change of 2.8% , so in theory would now read only 6.2% fast. However these speedo's are crude devices, & it is quite likely that simply changing to another 1152TPM unit would give a different reading. Providing you have a standard (TR) gearbox, 3.7:1 axle ratio, & normal size wheels & tyres, then the 1184 one would be correct. Bob Quote Link to post Share on other sites
MichaelH Posted October 8, 2016 Report Share Posted October 8, 2016 If it is still wrong you can get it recalibrated Speedograph Richfield have web site and it gives details of what to do to collect the info on your car then send the speedo(Any one that you've got) to them: they will recalibrate it to the details you give them. Look at their web site and see what you think MichaelH (no links to SR apart from being a satisfied customer) Quote Link to post Share on other sites
Alec Pringle Posted October 8, 2016 Report Share Posted October 8, 2016 Hi Ian, the 1152 unit refers to OE cross-ply fitment, 590x15, whereas the 1184 refers to OE radial fitment 165x15 . . . . the latter being of slightly smaller rolling radius hence more turns per mile required. The internals of old speedos are usually encrusted with the crud of ages . . . . . my coarse technique is to soak spray several times with electrical contact cleaner to remove all the decayed/dessicated grease etc . . . . . then when that has evaporated spray lightly with 'dry' PTFE lubricant. NOT, please note, WD40 or anything which will remain sticky and attract more **** . . . . . That won't cure a mechanical problem, but it should eliminate dirt and grease and thereby improve the function. Once fitted, check the speedo against a decent GPS unit for accuracy - quicker and simpler than the old days of clocking motorway mile posts ! Mind you, if you're still running ER70 Jag tyres, . . . . . . . Cheers Alec Quote Link to post Share on other sites
Motorsport Mickey Posted October 8, 2016 Report Share Posted October 8, 2016 Always a comfort though Alec with the ER70s, if you were to put the car into a canal the bloody thing will float upon their balloon like proportions ! Mick Richards Quote Link to post Share on other sites
Alec Pringle Posted October 8, 2016 Report Share Posted October 8, 2016 Sounds like a project Mick, an ER70 shod TRamphicar . . . . . . just right for the Trent . . . . . !! Cheers Alec Quote Link to post Share on other sites
stuart Posted October 9, 2016 Report Share Posted October 9, 2016 As long as they keep the tread on!, had a few shed the entire tread on XJ`s back in the day. Stuart. Quote Link to post Share on other sites
keith1948 Posted October 15, 2016 Report Share Posted October 15, 2016 Hello Ian Not sure if this will help but I have a TR4A with TR6 wheels and 165x80 R15 (radial) tyres. The speedo has 1184 stamped on it. When in 4th gear and overdrive on with the speed at 60mph, the rev counter reads twice 1184 (i.e. 2368) because it has 2-1 ratio. So you can drive along at 60mph in overdrive and rev counter will read 2368. Some years ago, Colin Boother and I drove back from France and were having a debate over speedo and odometer calibration. His TR4A had minilites with 185-70 tyres. We both checked our odometers at Belleme just north of Le Mans. Back in the UK near Broadway in the Cotswolds we checked again. Both cars had covered exactly the same mileage - 244.1 miles. So distance measurement was ok (or both wrong), speedo and rev counter agree at 60mph, so I assume I am doing correct speed and covering exact distances. Keith Quote Link to post Share on other sites
Ian Evans Posted October 16, 2016 Author Report Share Posted October 16, 2016 Many thanks for all your help and info.(Alec's info. re. cross ply and radial ply tyre calibration was new to me). There were certainly some interesting comments and experiences shared! However in the end I've decided to use Speedograph/Richfield to check out, repair and re-calibrate my other speedo (of dubious history!), so hopefully all should end well. In any case I'll report back on their efforts in due course for the benefit of all. Ian Quote Link to post Share on other sites
qkingston Posted August 23, 2021 Report Share Posted August 23, 2021 So just to share my experience in case other members which to do the same, I followed Speedograph Richfield's helpful advice and measured the speedo cable rotation for 20 turns of the rear wheel to give a calibration figure from them to work off. The high tech gadget and highly qualified assistant gave a repeatable result of 10 7/8 cable turns with std diff and 195/65/15 T-Trac2 Rgds David Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.