Wheel Sizing, Gearing, and Speedometer Spreadsheet

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Wheel Sizing, Gearing, and Speedometer Spreadsheet

#1 Post by KYPREO » Fri Jan 16, 2004 2:20 pm

Hey guys,

here's a little something I whipped up on excel this morning.

Preview:



Download:
tyresizegearingv2.xls
(88 KiB) Downloaded 475 times


(this is the fixed version, including the Saru update with better layout, gearing charts, common gearing list, etc)

People frequently ask for info on rolling diameter, gearing, and spedometer etc. Well, no you can play around with this stuff yourself.

This allows you to enter standard tyre sizing (eg 205/40/17), and gearing details, then you can check either speed in each gear at a particular rpm, or rpm in each gear at a particular speed.

I'm gonna update it with gearing graphs and something to calculate spedometer error (very simple really), or someone else wants to improve the spreadsheet, feel free.

Also let me know if there are any errors, and I'll fix them up.

EDITED KYPREO 2016 TO DIRECTLY ATTACH SPREADSHEET - IT'S NOT GETTING LOST AGAIN NOW!!
Last edited by KYPREO on Thu Feb 12, 2004 6:12 pm, edited 3 times in total.
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#2 Post by KYPREO » Fri Jan 16, 2004 2:42 pm

I think the values in there are from an RX4 box, but with 4.4 and rx7 5th gear :lol:

yep, that was a mistake with 6th gear...replace cell C21 with this..

=B15*6/B11/B12*E3*PI()/100000

Here are some gear ratios for common boxes

series 1/2
3.674
2.217
1.432
1.000
0.825
(3.542)

series 3
3.622
2.186
1.419
1.000
0.807
(3.493)

s4 13BT + Jap spec series 5s.
3.483
2.015
1.391
1.000
0.762
(3.288)

s6> 13BREWs, also US model and perhaps aussie delivered series 5s.
same, but with 0.719 fifth

EDIT: I've updated the file.
here's the new URL..

http://server4.uploadit.org/files2/1601 ... dsheet.xls

The stock values are basically my car's current specs.
Last edited by KYPREO on Sat Jan 07, 2006 12:55 pm, edited 1 time in total.


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#3 Post by KYPREO » Mon Jan 19, 2004 2:37 pm

barnsey wrote:Cant access the file :(

Can a Series 2 rx7 speedo be recalibrated? Im thinking its going to be a long way out with a series 4 box and 4.4 diff centre :P
UploadIt changed their server (again!). I'll reupload.

The gearbox you use doesn't affect spedometer accuracy - only the diff ratio and wheel size does. With a 4.44 it will read around 14% over your actual speed, but chances are your tyres are probably taller than the stock ones, plus I've heard 1st gen speedos read under, so overall you might only be 5-10% out.

The speedo can't be recalibrated, but you can get a ratio box made up which fits in between the gearbox and the speedo cable. I got a quote for this and its a bit over $100.


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#4 Post by KYPREO » Tue Feb 03, 2004 2:26 pm

Thanks to Saru and REACT the spreadsheet is now available again. :lol:

The spreadsheet can be found here:

http://www.react.org.au/downloads/tyresizegearing.xls


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Now with more crunchy goodness!

#5 Post by Saru » Fri Feb 06, 2004 12:45 pm

(A long time ago I used to get paid to make Excel to things it wasn't supposed to do. This was comparatively easy)

I've created a modified version of the spreadsheet with gearing charts that is available from:
http://www.react.org.au/downloads/tyresizegearingv2.xls (85k)

(please ignore the colours in these pics, they're GIFs not JPGs and GIF does weird things to colours)
This is the new front page:
Image

You can enter anything you want into the white cells. Everything else is protected (but not with a password) so you can't break anything accidentally. If you want to break it on purpose, that's up to you.

Compared to Greg's first version, this one has space for two sets of ratios for reasons which will soon become apparent. I've also added the "blue" section at the bottom to achieve some more crunchy goodness.

The most interesting part of this new version is the graphs. The idea of these is that you're able to see what speeds you can do in each gear. This is interesting purely from a nerdy perspective but is also interesting if you're looking at changing diff ratios, or to a different gear box altogether.

In this graph:
Image

you can see I've set it to wind out to about 11,000rpm in 1st, 2nd and 3rd, and to about 320km/h in 4th and 5th. This is purely for interests sake. I think this graph covers too great a range to use useful for anything other than figuring out that you could do (for example) 100km/h in 1st gear with a Guru dog box if your engine ran to 9700rpm (that's the ratios I've used in the pic).

This next graph is more interesting, if only because it allows you to see more detail, at the expense of chopping off the extremes to speed and rpms:
Image

You can also see where the final section of the first page of the spreadsheet comes in. If you want to, you can change the extremes of the X-axis from 60-250 to whatever you want. If you keep the high speed and low speed 190km/h apart you'll get nice even spacing, otherwise you'll get funny non-rounded increments (I had to pick a number *shrug*).

Also note there is no legend on this graph and all the gears are in the same colour. There is no legend becaue you should be able to figure out which gear is which from just looking. The gears are all the same colour because I think it looks better and is less visually distracting.

This 3rd graph uses similar principles to the 2nd but brings in the 2nd set of ratios from the main page. In this pic the two sets are both Guru dog boxes but the "blue" set is with a 4.44 diff and the "green" set is with a 4.1.
Image

I this graph is more interesting when you get two sets of different gearbox ratios on it and, say, 3rd and 4th from one box ends up between 3rd and 4ht from another, basically showing that one box has wider spaced ratios than the other.

With these graphs (particularly the 2nd one), assuming you knew your max power and torque figures you could calculate your optimum shift points (I think)

With all of the graphs you are able to change the granularity of the Y-axis. When looking at the graph, double-click any of the values on the Y-axis. A dialog box will pop up. Select the "Scale" tab and enter your values in. Be aware the Excel will occaisionally do weird things like making the lower bound of the Y-axis a negative number.

For maximum compatibility this file is Excel 95 format. If you download it and Excel bugs you about formats and compatability just save it in the latest Excel format you can.


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#6 Post by Saru » Thu Feb 12, 2004 12:22 pm

It's come to my attention that not everyone has MS Excel and so they can't use the spreadsheet.

Fear not, for help is at hand. Microsoft in their infinite wisdom provide a free, freely distributable Excel Viewer which is avaliable from the MS site.

Free Excel Viewer download

It's a 3.8 megabyte download.


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#7 Post by 1 MAD PP » Mon Oct 11, 2004 6:55 am

very helpful indeed cheers guys, no one over here could help me out in this area :D

one question thou, you said the ratios in the spreadsheet are for a rx4, can you confirm these are the same ratios for a rx3 four speed, if they are not, does anyone know the ratios of a rx3 four speed, so i can plug them into this amazing spreadsheet.

I run 13 inch 205 60's with a rx3 speed and a diff ratio of 4.11, and with that combo i ran a 12.8@178kms

i now have 15 inch 205 60's with same gearbox and diff,

if these ratios on the spreadsheet are the same as my gearbox i'm going to fly! :shock:

thanks again guys
:D


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#8 Post by KYPREO » Sat Jan 07, 2006 12:59 pm

I've edited some of the gear ratios.

OOH808 let me know that with his series 5 box speeds doesn't match up with the values spat out by the spreadsheet.

The technical data I have suggests series 5 gearboxes have 0.719 fifth gear, but this may be for US models only.

I have a 1991 series 5 halfcut here and did some tests. I marked up the tailshaft yoke to align with TDC on the pulley in fiftfh gear. I turned the engine over exactly 4 times and the tailshaft turned just over 3 times, which means it's probably a 0.762 ratio not 0.719.

It's possible Jap spec gearboxes are different to cater for different driving conditions.


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#9 Post by OOH808 » Mon Jan 09, 2006 12:59 pm

:)

i was getting .78 off the spread sheet reading off my handset,

also taken from a new falcon the speedo which read 100km when there doin 96km,

so a little out, but defiantly making more sense to me now greg 8)

hehe my car was doing 325kms an hour for a while in 5th gear :shock:


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#10 Post by Rota_Dan » Thu Oct 26, 2006 4:39 pm

Yerh same as above
I just got hilux diff n wanted to figure out speeds.
i got 13b 6port, think its a n/a s4 box and 4.1 lux centre.
With 17" wheels 40 profile, 205's
Can any1 help?

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#11 Post by dawson » Thu Jul 12, 2007 1:01 pm

thanks saru
your a champ



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#12 Post by JoshN » Sat Jul 21, 2007 8:21 pm

here you go, http://rapidshare.com/files/44151781/ty ... g.xls.html

this thing is cool as, i was using it today to figure out speeds with stock driveline, tyres, diff, gearbox compared to my new driveline with fat tyres, 4.11 diff and s5t box, heaps awesome.


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Re: Wheel Sizing, Gearing, and Speedometer Spreadsheet

#13 Post by Mr-RX » Tue Sep 23, 2008 9:19 pm

Does anybody happen to know the gearbox ratios for the old school 929's, the 1.8L piston donk.

Both auto and manual?


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Re: Wheel Sizing, Gearing, and Speedometer Spreadsheet

#14 Post by RE10 » Sat Aug 08, 2009 12:34 pm

That's a cool spreadsheet:

Speed in Gear (km/h)
RPM 10000

1st 113.0
2nd 148.7
3rd 185.2
4th 226.0

\:D/


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Re: Wheel Sizing, Gearing, and Speedometer Spreadsheet

#15 Post by 929Rus » Mon Oct 26, 2009 11:32 pm

Mr-RX wrote:Does anybody happen to know the gearbox ratios for the old school 929's, the 1.8L piston donk.

Both auto and manual?
4 speed manual:
1st - 3,403
2nd - 2,005
3rd - 1,373
4th - 1
rev - 3,665



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