Bigger Tyres, Speedo Correction

Brumby Kid · Post by **Brumby Kid** » Wed Sep 26, 2012 6:56 pm

So, as many I'm planning to fit bigger rims and tyres on my brumby.
The only problem with this is I will need to adjust my speedo.
I want to have my speedo correct
And my odometer / trip to be correct.
How do I do this?

Cheers Cam

Mitchhsj · Post by **Mitchhsj** » Wed Sep 26, 2012 7:23 pm

good question! when i look down and see I'm doing 90kph, WOOOO GOOO THE SUBI> IM FLYING.

MTB92 · Post by **MTB92** » Wed Sep 26, 2012 9:25 pm

I think paul posted it on one of 2HY's threads a while ago.

its up to you, but i wouldn't bother unless you really need it to pass pits or something like that. it is pretty easy to work out a % it is out by using a GPS and just go off that. give it 2 or 3 days and you wont even think about it, just naturally compensate

.

its also interesting to note, my speedo is actually more accurate with the larger tyres than the stock size.

stilson · Post by **stilson** » Thu Sep 27, 2012 2:43 am

If ur electronic Jaycar do a kit. If its mechanical hen you have to change the nylon gears that drive the speedo cable.

Brumby Kid · Post by **Brumby Kid** » Thu Sep 27, 2012 8:43 am

I'm electronicle and could easily make the kit.
How do I tell which one it is?

Speedo is easy, GPS
But really dad wants the odometer to work ( and so do I)

Cheers Cam

Silverbullet · Post by **Silverbullet** » Thu Sep 27, 2012 5:35 pm

Brumby Kid wrote:I'm electronicle and could easily make the kit.
How do I tell which one it is?

Cheers Cam

MCM to the rescue! they even use the Jaycar kit

http://www.youtube.com/watch?v=bMs7w72QTVM&feature=plcp

Brumby Kid · Post by **Brumby Kid** » Sat Sep 29, 2012 6:49 pm

Bump.
Currently the only 14" tyre I can find are the maxis bighorn or buckshot mudder, which are both 27/8.5.
I worked out that if I go from my 175/75/13 to one of these 27/8.5 I would be out by about 14%. Correct?
I'm virtually certain that the brumby is a mechanicle speedo. Correct?

Cheers Cam

stilson · Post by **stilson** » Sun Sep 30, 2012 2:55 am

Taller final drive ratio?

Brumby Kid · Post by **Brumby Kid** » Sun Sep 30, 2012 11:29 pm

Yeah final drive ratio does differ, less torque more high end speed.
But for every revolution of the gearbox, I will be traveling faster and further than what it thinks. So at 60km/h I will actually be doing 66km/h (for example). And at 100km/h I will actually be doing 112km/h.
Note it is not linear, it is a scale or percentage.

Cheers Cam

stilson · Post by **stilson** » Sun Sep 30, 2012 11:50 pm

I meant you could change it to correct speedo.

woody.t · Post by **woody.t** » Mon Oct 01, 2012 1:00 am

Brumby Kid wrote: Note it is not linear, it is a scale or percentage.

.....umm?

Post by **Alex** » Mon Oct 01, 2012 1:17 am

If it's a scale or percentage how can it be 66 when you're actually doing 60 and 112 when you're doing 100?
:what:

Sent from my HTC Velocity 4G using Tapatalk 2

Brumby Kid · Post by **Brumby Kid** » Mon Oct 01, 2012 8:40 am

An example. I didn't actually check those exact numbers.

Post by **TOONGA** » Mon Oct 01, 2012 9:21 am

The brumby speedo is mechanical, as to finding a speedo gear, 1. chicken lips are easier to find. 2. you will have to split the box to get the mythical gear in

I think it would be easier to work out where the speedo needle is when you are doing 100 (via gps) and marking that with a small sticker same with 60, 80 and any other speed you want.

Then with all this information make your own speedo dial and put that in place. way easier to adjust the read out that try to find a gear the right size.

TOONGA

Brumby Kid · Post by **Brumby Kid** » Wed Oct 03, 2012 10:41 pm

Bennie now that your back perhaps your 2c?
Thanks mate.

Cheers Cam

YouTube · Post by **El_Freddo** » Wed Oct 03, 2012 11:20 pm

Brumby Kid wrote:I'm electronicle and could easily make the kit.
How do I tell which one it is?

Speedo is easy, GPS
But really dad wants the odometer to work ( and so do I)

Cam, tell your dad that the odometre will work... just ~18% less depending on the MY setup. The L series, well, mine anyway, is 18% out. So at 84 km/h indicated on the instrument cluster I'm actually doing 100km/h.

Now that I've worked out that I'm 18% out I can/should have recorded my odometre reading when the big tyres went on, from there I could calculate how far I've actually gone - I do it from tank to tank (just for Jonno). On the sand I got 16L/100km fully loaded. A combination of sand and highway with a gusty wind 12.8L/100km. Last tank all on the black top, fully loaded with some towing 11.2L/100km. Pretty happy with that.

As for the speedo thing, the best way to go (with some trial and error) would be a foz box, the 4.11 final ratio pretty much fits the 27 inch tyre to a tee. But there's a difference in the cluster speed over the EJ series subis. In the gearbox build (that I'm desperately looking for parts for to complete the build) the final ratio is 4.11:1, the speedo gear we're going with is from the 3.9 final ratio box, the idea is to spin the speedo a little faster to compensate for the difference in the cluster - worth a try as the 4.11 speedo gear doesn't quite do it with the L series cluster.

You might be able to build an electronic system that uses a subaru sender unit and some kit that drives the mechanical cluster, if this works you should be able to pretty much dial in any change in the tyre difference. Maybe.

I hope this helps.

Cheers

Bennie

phil nelis · Post by **phil nelis** » Sat Oct 06, 2012 4:29 pm

I had a custom unit built. Supplied cable from donor car that g/box came from.Used that for through to under dash,fitted reduction box from transit van to cable then cut and fitted brumby cable to speedo. Running 14`` L sunraysia rims with 27`` corsa mud tyres,speedo now reads .2k out at 100kph on dyno. Box was from an rx turbo that had an ea82t in it. Used the clsd at 3.7 ratio and the disc brakes as well. Custom built cv`s to fit larger splines on g/box. Also split g/box and changed out l/r gears to 1.19 for awesome offroad. It was expensive to do the cable after the new gears were fitted in the reduction box but i like to know exactly how fast i`m going so i don`t have to worry about cops and camera`s.

Brumby Kid · Post by **Brumby Kid** » Sat Oct 06, 2012 7:11 pm

Please elaborate on this Phil.
If you have pictures this would be good.
I'm not after expensive but a reduction box I can probably afford.

Cheers Cam

phil nelis · Post by **phil nelis** » Sun Oct 07, 2012 12:00 pm

Got to find a server to do pics first then i`ll put some up. Working on a wiring harness for an ej22 upgrade atm. There is a car instrument mob in strathalbyn that should be able to help. All my engineering is fully compliant with qld tpt law & mod plates fitted so cops & tpt inspectors can`t touch me. Also all listed with insurance so no drama there if ever needed.