Cluster show 15 km/h more than reality

[PL420]

As the title says, my oem cluster is not running right. I tested it up, with another car, on the highway. When my cluster show 140 km/h, i'm actually at 120kmh to 125kmh. What should I check first ?!

My GTR is bone stock except for Mines computer, which was already installed when I bought the car.
Can anyone help ?!

[caliber676]

You sure his speedo was correct? The speedo is cable driven so most likely your cable is slipping or damaged which is common.

[curtisgoodman]

are your tires and rims stock sizes too?

[PL420]

I have oem mags with Potenza RE01
225/50/r16

[PL420]

The cable your talking about is right behind the speedo cluster?!

[Dragon Humper]

Stock cluster?

My Nismo cluster reads fast too, about 15% over actual. Thought it might just be the fault of an aftermarket speedo but I see lots of people have speedos that are reading over. Better over than under though.

Would be nice if there was a quick fix like putting a gear in the speedo drive in the trans with one more tooth in it, that would be about right for a 15% correction. haven't looked into it too much though for compatible gears for the Skyline (300zx should be the one but you never know untill you try it).


Jon.

[Skym]

You can get different wheels on trans side of speedo cable (off Nissan Terrano, Patrol, etc that run bigger size wheels, search the net, as it's mentioned which ones work). Usually overall wheel size (tyre thickness on both sides of wheel + rim diameter) makes the speedo vs wheel speed differ. Mine was out by only 1km/h at some speeds which was said to be very accurate for a Skyline (when I had it tested on a speedo testing dyno).

You sure his speedo was correct? The speedo is cable driven so most likely your cable is slipping or damaged which is common.

When speedo cable failed on my car the speedo needle started to jump up and down while car was at constant speed, clicking sound from behind the dash. When speedo cable fails it cracks plastic part behind dash and pushes against bearing inside speedo head behind dash on a funny angle and get a clicking sound from behind dash, takes out the bearing. I got a custom speedo cable made up and the speedo head behind dash was repaired (new bearing), speedo + cable was tested on bench.

[PL420]

Stock cluster?

Jon.

Yeah its stock!


Thanks for the info SKYM

[MattiasJacobs]

My nismo reads slow as it is meant for 18" wheels with 235's. Its probably related to your tire sizing unless they are stockers. When I put my 22" 305/45's on my truck in the summer there is a 10% difference because the wheels take that much longer to go a full rotation. It's a HUGE difference in tire size though so I couldn't be positive about why your numbers are so high.

[Skym]

It could be a GTS speedo part in a GTR dash, which could explain why it's out. Or problem with speedo cable.

Thanks for the info SKYM

You're welcome.

If pull dash out, calibration should be mentioned on the back (printed on circuit board). Speedo specialist should be able to check if pull speedo cable, dash out and send to them.

[PL420]

My nismo reads slow as it is meant for 18" wheels with 235's. Its probably related to your tire sizing unless they are stockers. When I put my 22" 305/45's on my truck in the summer there is a 10% difference because the wheels take that much longer to go a full rotation. It's a HUGE difference in tire size though so I couldn't be positive about why your numbers are so high.

The tires are not stockers : Potenza re01 225/50/r16
Mags are Stock!
Do you know the size of the stockers, because I need to change those tires since the rear ones are pretty much slick! I want to buy Potenza RE11 with same size

[PL420]

It could be a GTS speedo part in a GTR dash, which could explain why it's out. Or problem with speedo cable.



You're welcome.

If pull dash out, calibration should be mentioned on the back (printed on circuit board). Speedo specialist should be able to check if pull speedo cable, dash out and send to them.

The calibration will tell me if its a gts speedo?!

[Dragon Humper]

You've got the stock size tires on there. Mine were stock too when I measured the accuracy with GPS. Tires can vary in size from manufacturer to manufacturer (in a 225/50r16) but it shouldn't be more than 2%. Whenever I get motavated I'll look into changing out the driven speedo gear in the trans.



Jon.

[PL420]

I'll investigate and come back to you guys. Thanks for all the help!

[collector240sx]

Hi, it's odd that it would be off by 15% at highway speed, makes me wonder if your speed sensor was ever replace, and they didn't put the right plastic gear on it. It's really easy to put the wrong one once you start looking at how many different one are actually out there.

I remember seeing a site, I tried to find it for you but it was maybe 5-6 years ago and didn't have much luck, which showed which color wheel you needed to use depending on which diff gear, and wheel size you had.

if you don't believe me here 2 link that explain what I mean but just for gearing (I'm sure the calculation to account for the wheel variation could be calculated in an excel) only thing it was for Z31 and Z cars. But I'm sure if you read it you'll get my point. 2 different cars with different transmission, both making reference to the same gearing for each color.

Color = number of teeth on the plastic wheel

http://z31.com/speedo.shtml

http://www.zhome.com/ZCMnL/tech/R200.htm

The plastic gears can be purchase separately, and if you choose the right one your cluster can be pretty accurate.

If your to lazy to check the link here is a resume.

# Teeth----Color----Differential Ratio----Part number
16-----------Yellow----------3.36------------32703-78100
17-----------Black------------3.54------------32703-78101
18-----------Blue--------------3.7-------------32703-78102
19-----------White-----------3.9--------------32703-78103
20-----------Red--------------4.11--------------32703-78104
21-----------Purple----------~4.3--------Part numbers and availability unknown.
22-----------Orange---------~4.8--------Part numbers and availability unknown.
23-----------Green----------~5.1--------Part numbers and availability unknown.

Hope it's help someone.