Instrument cluster tire size change Topic is solved

Post by **mkc1** » 31 Aug 2020, 10:57

I recently replaced the instrument cluster in my 97 850 GLT, which immigrated to Canada with me from the US, with the cluster from a 97 850 AWD which was sold in Canada. I'm pleased because I can now see my clock/thermometer at night and the speedo and fuel units are metric.

However the speedo reads a bit fast, presumably because the tires from the 850 AWD are larger than the tires on the GLT (205/55R16 vs 195/60R15). The 850 ODBII app from xiaotec reports the wheel circumference as "195".

I saw a post from a couple of years ago warning not to try to use the app to change the tire size programmed into the cluster. I wondered if this warning is still valid or if these values are better understood now and what might be the appropriate value to program for the 195/60R15 tires on the 850 GLT.

Thanks!

Post by **misha** » 31 Aug 2020, 12:37

Are both clusters in miles?
Fuel in gallons or liters?

Post by **mkc1** » 31 Aug 2020, 13:22

misha wrote: ↑31 Aug 2020, 12:37 Are both clusters in miles?
Fuel in gallons or liters?

The old one had miles in large numbers on the speedo and km/h in small numbers. The odo was in miles (until it broke.) The new one is all in kms.

The old one's fuel was gallons, the new one is liters.

Post by **misha** » 31 Aug 2020, 13:29

That is the problem,the new cluster is still displaying speed in miles ....is ambient temperature in C or in F on display?

It's not because of tyres:
https://tiresize.com/comparison/

Speed error is minor.

Post by **bmdubya1198** » 31 Aug 2020, 17:02

You should be able to calibrate it with the app. I have a hard time believing you can't switch between miles and KM on the speedo.

Post by **scot850** » 31 Aug 2020, 17:28

The 850's originally came with a 205-50-16 tire. Volvo eventually did an update to recommend fitting a 205-55-16 tire as too many owners were complaining of tires splitting when hitting pot holes. I don't recall them ever fixing the speedo change because of this. May be worth asking them if there is a software change. They recommended the change so maybe there is a 'free' fix from Volvo?

There are several tire size comparison web-sites. Worth checking what the actual error is.

https://www.tacomaworld.com/tirecalc?ti ... -205-55r16

Acording to this it is 2mph at 60mph or 4kph at 110kph

Neil.

Post by **mkc1** » 31 Aug 2020, 18:45

The cluster was removed from an 850 AWD with 205/55R16 tires and installed on an 850 GLT with 195/60R15 tires. Looking at the diff between those two sizes on the tire comparison site shows that it doesn't make as much difference to the displayed km/h as I'm seeing though.

The outside temperature is currently displayed in C but I don't see how that's relevant since it's easily changeable by holding the 'h' and 'm' buttons down simultaneously.

I also don't understand the idea that "the new cluster is still displaying speed in miles" since I assumed that the signal in to the cluster was RPM at CV axle and it used that plus the tire size to compute what to display on the dial. However, the spot on my old speedo where 100km/h was is about where 110km/h is on the new one, so perhaps there is some merit to that idea. Any idea how to fix it? Does the country code need changing so that it knows the input is coming from a US market car instead of a Canadian one?

Post by **scot850** » 31 Aug 2020, 21:48

I swapped a KPH to MPH (US) cluster on a 97 850 GLT. We had no issues going that way around. Can't recall the tire size it had though.

Neil.

Post by **scot850** » 31 Aug 2020, 21:49

Perhaps the AWD had a different gear set to a FWD in the trans?

Neil.

Post by **misha** » 01 Sep 2020, 02:06

Read this from the beginning:
viewtopic.php?f=1&t=92261&hilit=Speedom ... c&start=30