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Posted

I've done a search and don't see anything recent.   I've recently acquired a 99 Caterham with a history of failing speedometers.  It appears that various drives and cables have been replaced over the last 25 years even though the car has not been driven that much.  The speedometer has recently failed again and I'm not inclined to fix the problem the same way and am looking to replace it..

 

Is anyone aware of an 80mm GPS speedo that looks similar to the Caterham unit or an 80mm non-GPS one with a sensor I could run to  one of the front wheels?

 

I have found the Speedhut GPS units but those are 85mm and I'm not wanting to modify the dash.   

 

Thanks!

 

Scott

 

 

 

 

Posted

Racetech has a 80mm unit   I got mine from Burton, surely someone over here has them

 

Mine is wired to the transmission, but I'm sure you can put a GPS sender on it

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Posted

Mech speedo failures are normally lack of fresh lubrication on the cable (tend to cause a jumpy indicator needle before failure) but can also be caused by poor cable routing. I assume you have a 90 degree drive at the trans.

 

A gps speedo may also have a separate module that should sit in the open for line of sight to the satellite(s) and may still loose indication around buildings and tunnels.

 

The difference in a standard 3-3/8 gauge and the opening in your dash may only be a radius of .059" or less and could be rolled in versus filed away.

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Posted

Thank you all, I have my research cut out for me and appreciate the insights.  

 

Scott

Posted

+1 for the Racetech.  

RTSC130 and sensors.  

The Racerech speedo has an input that can accept a GPS or a, what I call a proximity or hall effect sensor.  That one is placed near a rotating item like a drive shaft or brake rotor. It senses the rotation.

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Posted

There are very reasonably priced programmable speedos that require a sensor (usually magnetic pickup but there could be hall effect units out there). Depending on the transmission, an oem type electronic speed sensor (such as from a late-80s or newer application) can be installed to replace the cable attachment and 90 degree gear box if equipped. If the programmable speedo input required is a specific waveform or range of rpm and frequency, there are cheap signal conditioners that can be installed. The end result should be about $200 or less in parts.

 

If replacing the original mech speedo with another mech speedo, even if the existing cable fits the speedo, the calibration of the speedo itself varies for Cat depending on the year model as well as the aftermarket units. It just means that a cable drive gear swap may be required. This can be the trans output shaft gear, driven gear, or the gears in the 90 degree box. Speedos are usually between 1000 and 1100 rpm for a 60 mph indication and often have it written on the face.

 

I've lubed cables once the speedo started jumping and they are still in service years later without a relapse (used synthetic wheel bearing grease). If ignored, the cable will fail. Cable cores are available and quils can be made if a replacement cannot be found or the old one repaired.

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