Dr.Jeff
True Classic
True. This might be good for the Rat X? In my case (for the outlaw) I won't even bother mounting a speedo, just this.
Speedometer Calibration
- Thread starter dllubin
- Start date
Mxgrds
True Classic
The calibration of the stock speedo is very easy. Just a few screws to get the glass off, pull the dial, use your phone gps to drive specific speed, put the dial back on that speed exactly refit the glass front. 30 minutes max.
Dr.Jeff
True Classic
Until I add two weeks to get the replacement unit, after I accidently destroyed the original one trying to correct it. Just speaking for my typical experiences; seems pretty much everything on these cars breaks when you touch it. Purely being sarcastic.
myronx19
True Classic
I'm actually trying to calibrate my OE speedometer using a gear reduction calibration device. My speedometer is off by quite a bit. I run 185/60/13s, and when my speedo says I'm doing 115 km/h, I'm actually doing 100 (making it a 15% error!!) (see the adapter below - that's what I want to install, you order it with the ratios you need to correct the speedometer error).
In order to correct the speedo error, I want to buy and install one of these:
Dr.Jeff
True Classic
A couple of people have mentioned relocating the needle onto the speedo to recalibrate it. I'm not sure but it seems there may be some shortcomings to this approach? Please correct me.
First, on some (non Fiat) speedos I've played with, the needle actually acts as the "rest stop" for the unit. So moving the position of the needle won't actually change its function. But I have not looked at the Fiat speedo to see if this is true. Second, if that is not the case with the Fiat speedo, then won't the needle no longer be at "zero" when not moving? Third, it may give you a compromised correction; it may be more accurate at the speed you were going when you repositioned the needle, but all other speeds will be proportionally off from that point (faster or slower than that speed).
I'm not saying the method of repositioning the needle won't be better than it was, but it still won't necessarily be accurate. However as I said, I'm not sure - only speculating so please inform me.
Also, how does this interplay with the way the needles get bent/curved? Actually it might be a good time to replace the needle if you can come up with one (there have been threads about that).
First, on some (non Fiat) speedos I've played with, the needle actually acts as the "rest stop" for the unit. So moving the position of the needle won't actually change its function. But I have not looked at the Fiat speedo to see if this is true. Second, if that is not the case with the Fiat speedo, then won't the needle no longer be at "zero" when not moving? Third, it may give you a compromised correction; it may be more accurate at the speed you were going when you repositioned the needle, but all other speeds will be proportionally off from that point (faster or slower than that speed).
I'm not saying the method of repositioning the needle won't be better than it was, but it still won't necessarily be accurate. However as I said, I'm not sure - only speculating so please inform me.
Also, how does this interplay with the way the needles get bent/curved?
Actually it might be a good time to replace the needle if you can come up with one (there have been threads about that).
Mxgrds
True Classic
If the dial is set at 80 km/h exactly with gps speed, the deviation below and above that speed is neglactable.The photos are just to illustrate how easy it is to set the dial to match the speed given by gps. But this needs to be done in a driving car with the speedo installed. So find a strait silent road to do it.
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dllubin
Don
I've seen these used on American cars back in the 60s and 70s. Good to see they are still made. Do they make a unit that will interface to an X speedo cable?
Since my unit is 10% off and yours is 15% off, I wonder if something inside the unit is degrading with age. When these cars were new, the errors were not that bad. Has anyone taken the speedo mechanism apart? I can think of reasons why they would read low but I am still trying to come up with one that would make it start reading high.
Way back, there used to be a speedometer test section on US 101 around Redwood City. I recall checking the car after putting on some 185-70/13 Pirelli CN36 tires (no 185-60/13 back then) and that actually made it read slightly low. That was expected since they were 3.7% taller than stock, but that also means the speedo could not have been nearly as far off as it is now.
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dllubin
Don
I'd get an rpm reading on the road for the reference speed and then dial in the speedo calibration in the shop with the wheels spinning. That way, I'm not screwing around with the reference device (tach) while I'm trying to calibrate the speedo.
dllubin
Don
I came across some information on how a mechanical speedometer works:
Mechanical Speedometer (https://www.hotrodhotline.com/calibrating-speedometer#.XWcxgChKhhE)
For over a century the mechanical (eddy current) speedometer has been used and is still in widespread use. A rotating flexible cable usually driven by gearing linked to the output of the vehicle’s transmission inputs its signal. It was the only type commonly used until the 1980s and the appearance of electronic speedometers.
When the vehicle is in motion, a speedometer gear assembly at the rear of the transmission will turn a speedometer cable that then turns the speedometer mechanism itself. A small permanent magnet driven by the speedometer cable interacts with a small aluminum cup attached to the shaft of the pointer on the analogue speedometer. As the magnet rotates near the cup, the changing magnetic field produces “eddy” currents in the cup, which then produces another magnetic field. The effect is that the magnet exerts a torque on the cup, "dragging" it, and thus the speedometer pointer, in the direction of its rotation with no mechanical connection between them.
The torque on the cup increases with the speed of rotation of the magnet. Resistance to movement is created by the spring trying to hold the pointer at zero. At a given speed the pointer will remain motionless and pointing to the appropriate number on the speedometer's dial. This is fixed at a preset number of revolutions per mile (usually 1,000 rpm per mile). You will need to determine what is the correct number for your application. At this point the corrections need to be made by allowing for the variations in the vehicle from stock.
I am wondering if the problem with X speedometers reading too high with age has anything to do with the return spring getting too weak? Has anyone taken an X speedo apart to see what is inside? I wonder if the return spring can be adjusted or replaced?
Mechanical Speedometer (https://www.hotrodhotline.com/calibrating-speedometer#.XWcxgChKhhE)
For over a century the mechanical (eddy current) speedometer has been used and is still in widespread use. A rotating flexible cable usually driven by gearing linked to the output of the vehicle’s transmission inputs its signal. It was the only type commonly used until the 1980s and the appearance of electronic speedometers.
When the vehicle is in motion, a speedometer gear assembly at the rear of the transmission will turn a speedometer cable that then turns the speedometer mechanism itself. A small permanent magnet driven by the speedometer cable interacts with a small aluminum cup attached to the shaft of the pointer on the analogue speedometer. As the magnet rotates near the cup, the changing magnetic field produces “eddy” currents in the cup, which then produces another magnetic field. The effect is that the magnet exerts a torque on the cup, "dragging" it, and thus the speedometer pointer, in the direction of its rotation with no mechanical connection between them.
The torque on the cup increases with the speed of rotation of the magnet. Resistance to movement is created by the spring trying to hold the pointer at zero. At a given speed the pointer will remain motionless and pointing to the appropriate number on the speedometer's dial. This is fixed at a preset number of revolutions per mile (usually 1,000 rpm per mile). You will need to determine what is the correct number for your application. At this point the corrections need to be made by allowing for the variations in the vehicle from stock.
I am wondering if the problem with X speedometers reading too high with age has anything to do with the return spring getting too weak? Has anyone taken an X speedo apart to see what is inside? I wonder if the return spring can be adjusted or replaced?
ng_randolph
Bjorn H
The X1/9 speedometer is a very conventional eddy-current type. On the one I have taken apart, the clock spring is soldered at the stationary end, and it would be easy to move it to change calibration. After altering the spring, you would also have to remove the needle and re-install it in the correct 0 position.
BTW, if your speedometer is reading too low, the spring is too stiff, not too weak.
BTW, if your speedometer is reading too low, the spring is too stiff, not too weak.
Dr.Jeff
True Classic
Point it toward north and hit it with a hammer?
Cratecruncher
True Classic
Years ago I sent off a box full of Smiths gauges to an expert to be recalibrated. He took them apart and found rust and dirt in the mechanism of each and every one causing them to read low. A specialist has bench apparatus that is used to calibrate them to near perfect after rebuilding but it comes at a price. What unsettled me most was sending a box full of irreplaceable gauges off in the mail to a stranger. When X1/9's are salvaged the first thing saved from the car is the head unit so our gauges aren't that dear.
If you dyno your engine at the wheels you can also get a feel for how accurate your speedo and tach are and if the error is linear. A linear error is likely return spring related but non-linear is probably dirt, dried lubricant, etc.
If you dyno your engine at the wheels you can also get a feel for how accurate your speedo and tach are and if the error is linear. A linear error is likely return spring related but non-linear is probably dirt, dried lubricant, etc.
dllubin
Don
My guess is that the return spring gets weak with age as the reports in this and other posts seem to indicate the X speedos read higher with age.
myronx19
True Classic
BTW: I think I was a little off on how out my speedometer is.
Mine has always been off, so it's not getting worse over time (since 30 years ago! - I drove on the highway, followed the mile markers and after 10km, my trip meter was off). Perhaps I'm around 8-10% max off, partly due to my smaller tire OD and the fact that these were probably not very accurate to begin with.
I could live with it I guess?!?! but it's not too difficult of a fix. I have a NOS instrument cluster that I bought from Midwest that I'll eventually install.
Mine has always been off, so it's not getting worse over time (since 30 years ago! - I drove on the highway, followed the mile markers and after 10km, my trip meter was off). Perhaps I'm around 8-10% max off, partly due to my smaller tire OD and the fact that these were probably not very accurate to begin with.
I could live with it I guess?!?! but it's not too difficult of a fix. I have a NOS instrument cluster that I bought from Midwest that I'll eventually install.
Dr.Jeff
True Classic
Dr.Jeff
True Classic
Along the lines of the inexpensive digital GPS speedometer we discussed, I also came across a pretty good deal on a complete digital dash display. Has a bunch of functions and capabilities. Different models to choose from. Great prices compared to what these normally sell for from US companies (I'm quite sure the ones in this listing is where they all come from):
https://www.aliexpress.com/item/32912806395.html?spm=a2g0s.8937460.0.0.72d92e0emEcHy0
https://www.aliexpress.com/item/32912806395.html?spm=a2g0s.8937460.0.0.72d92e0emEcHy0
kmead
Old enough to know better
Well thanks that led me down a car parts bunny trail for 45 minutes.