hmm ..where do we insert downforce from bootlid spoiler at speed into the equation?
do i measure from the leading edge of the grease spot or a guesstimated centre?
Speedo Gear F.A.Q.
Started by
_CHOPPER_
, May 08 2006 08:30 PM
58 replies to this topic
#26
arrimar
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Posted 17 March 2007 - 02:46 PM
#27
_devilsadvocate_
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Posted 17 March 2007 - 05:30 PM
Yes it gets harder when the car is moving!(but at least get it right as it can be 1st) downforce from the spoiler? are we talking ricers here? to a degree conteracted by the carcus of the tyre moving radially outwards as the tyre is spun faster.hmm ..where do we insert downforce from bootlid spoiler at speed into the equation?
#28
arrimar
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Posted 17 March 2007 - 07:08 PM
this is fun DA.
the old DA would never have allowed counteracted or carcass to slip through.
bootlid spoilers belonged to we of the muscle prior the propagation of rice.
anyway chop chop will want his thread back soon.
permission to remove any or all of my input is granted.
the old DA would never have allowed counteracted or carcass to slip through.
bootlid spoilers belonged to we of the muscle prior the propagation of rice.
anyway chop chop will want his thread back soon.
permission to remove any or all of my input is granted.
#29
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Posted 17 March 2007 - 07:41 PM
* waves magic wand to remove BS *anyway chop chop will want his thread back soon.
permission to remove any or all of my input is granted.
Hmm... all the BS is still there.
* pulls pants back up *
Crap on all you want. If somebody wants my help and posts ALL the info I ask, they will get an answer.
#30
_tyre fryer_
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Posted 18 April 2007 - 02:55 PM
Hi chop. this is getting confusing to me.
my uc has an aussie 4-speed and 205/60/13 wheels. it had a 3.36 diff until that blew up. I changed it to a 3.08 and now its reading incorrectly (42km/h is about 50km/h).
can you please tell me what speedo gear i need to change it o.
dad is out there now checking the gearbox gear.
my uc has an aussie 4-speed and 205/60/13 wheels. it had a 3.36 diff until that blew up. I changed it to a 3.08 and now its reading incorrectly (42km/h is about 50km/h).
can you please tell me what speedo gear i need to change it o.
dad is out there now checking the gearbox gear.
#32
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Posted 18 April 2007 - 09:24 PM
you sure?
cos I used all that stuff that was posted before to calculate it and i worked out it needed LESS teeth. meaning it needed 22t dark blue. BTW the driver gear was white and the speedo gear was red.
cos I used all that stuff that was posted before to calculate it and i worked out it needed LESS teeth. meaning it needed 22t dark blue. BTW the driver gear was white and the speedo gear was red.
#33
_CHOPPER_
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Posted 19 April 2007 - 09:18 AM
Sorry, I used the 3.36 diff in the calculation. 22 tooth is correct with 3.08 gears.
#34
_jklumpp_
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Posted 19 April 2007 - 01:33 PM
So does anybody know about Supra Boxes?
I measured with the GPS the other day, and with the speedo reading 100kph, the car was doing 116kph....
Does anyone know if there are different gears for these boxes?
I measured with the GPS the other day, and with the speedo reading 100kph, the car was doing 116kph....
Does anyone know if there are different gears for these boxes?
#35
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Posted 22 April 2007 - 11:15 PM
can i just get some clarification on the formula please chop chop.Despite the fact I have posted it several times, most people can't seem to work it out. For the game few:
Driven Gear = 512.27 x diff ratio x drive gear / tyre diameter ( in millimetres )
first up here is a link to the rare spares page showing all the gears
https://rsp-secure.c...a...C LJ TORANA
ok now the driven gear is the one that you can push in the side of the gearbox right so we need to identify the colour of the drive gear which is installed on the output shaft of the gearbox,can be seen through the speedo drive hole i assume?
so the formula is
512.27 ,multiplied by
diff ratio ,multiplied by
the number of teeth on the drive gear,divided by
tyre diameter(rolling distance)
equals the number of teeth you need on the driven gear?
#36
_CHOPPER_
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Posted 23 April 2007 - 10:09 AM
You got it right apart from the tyre diameter. Diameter is the distance across the centre. Rolling distance is meaured by placing a tape measure around the outside of the tyre. As posted in the other thread I started:
205/65R15 diameter =
(205 x 0.65 x 2) + (15 x 25.4)
If you worked it out correctly, you should get 647.5 mm
205/65R15 diameter =
(205 x 0.65 x 2) + (15 x 25.4)
If you worked it out correctly, you should get 647.5 mm
#38
LHSL
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Posted 26 June 2007 - 12:20 PM
Hi there,
Could someone help me. I have a LH torana running a steel case celica 5 speed gearbox. Wheels are standard 185/70 13inches. Diff is 2.78. What gear do I need? My speedo at 60kms shows aprox 40 km/hr.
Cheers,
Phillip
Could someone help me. I have a LH torana running a steel case celica 5 speed gearbox. Wheels are standard 185/70 13inches. Diff is 2.78. What gear do I need? My speedo at 60kms shows aprox 40 km/hr.
Cheers,
Phillip
#39
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Posted 26 June 2007 - 01:42 PM
to help with the above, after some research yesterday i found that the W55/57/58 Supra gearboxes have either a 10 or 11 tooth drive gear, and driven gears are available in 30, 31, 32, 33, 34, & 35 tooth.....not sure if the Celica's were the same?
Edited by jklumpp, 26 June 2007 - 01:43 PM.
#40
_toddy_
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Posted 28 June 2007 - 09:40 PM
hi chopper could you please tell me what gear I need in my m21?
I have 2.75 gears with 225 50 15s
Thanks in advance
I have 2.75 gears with 225 50 15s
Thanks in advance
#41
_rookie_
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Posted 20 July 2008 - 04:47 PM
hi, hope somone can help, I have a th350 with 2.75-1 diff and 265/50/14's and have no idea what speedo gear I need?
Cheers
Nick
Cheers
Nick
#42
rodomo
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Posted 02 August 2008 - 01:40 AM
Example:
(Rolling circumference is NOT used in this calculation.
Tyre DIAMETER is what is used.)
Tyres: 225/50/16, DIAMETER of 631.4mm as calculated here:
http://www.miata.net...e/tirecalc.html
Speedo DRIVE gear: (found in gearbox extension housing) 8 teeth.
Diff RATIO: 3.08:1
So......
512.27 X 8 (DRIVE gear teeth) X 3.08 (RATIO) = 12,622.332
12,622.332 divided by 631.4 (mm DIAMETER) = 19.991023 or 20 teeth on your DRIVEN or speedo cable gear.
(Rolling circumference is NOT used in this calculation.
Tyre DIAMETER is what is used.)
Tyres: 225/50/16, DIAMETER of 631.4mm as calculated here:
http://www.miata.net...e/tirecalc.html
Speedo DRIVE gear: (found in gearbox extension housing) 8 teeth.
Diff RATIO: 3.08:1
So......
512.27 X 8 (DRIVE gear teeth) X 3.08 (RATIO) = 12,622.332
12,622.332 divided by 631.4 (mm DIAMETER) = 19.991023 or 20 teeth on your DRIVEN or speedo cable gear.
#43
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Posted 02 August 2008 - 04:02 PM
Rob, since the formula has been given out several times ( including in this thread ) it appears fairly obvious to me that the above three members couldn't work it out for themselves. What makes it a bit trickier is that the T350, 400 @ 700R4 have different numbers of teeth on their cogs, as well as different colours.
#44
rodomo
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Posted 02 August 2008 - 04:09 PM
Chop,
There has been another thread where a member was having trouble understanding the formula.
My above post has been copied and pasted into this thread as this thread is a sticky.
There has been another thread where a member was having trouble understanding the formula.
My above post has been copied and pasted into this thread as this thread is a sticky.
#45
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Posted 02 February 2009 - 08:11 PM
A question with all the info I need to give an answer. 24 tooth gear.
* hint to all others *
gday chopper, my car has a tri, 2.78 & 235/60/14 tyres. ant help on what speedo drive would be appreciated thanks stu.
#46
rodomo
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Posted 02 February 2009 - 08:39 PM
I think Chopper is off line at the moment after his house move? 
You need a blue drive gear in your g/box extension housing.
Rare's part no. SG1001 (9 teeth)
And
You need a white driven gear on the end of your cable.
Rare's part no. SG1007 (20 teeth)
You need a blue drive gear in your g/box extension housing.
Rare's part no. SG1001 (9 teeth)
And
You need a white driven gear on the end of your cable.
Rare's part no. SG1007 (20 teeth)
#47
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Posted 02 June 2009 - 01:39 PM
I have a trimatic, 2.78 diff, the white drive gear (8 tooth) and my tyre diameter is 651mm (225/60/15).
The formula works out to 17.5??
Do i have to change the drive gear or sumthing aswell? How hard is it to change the drive gear?
Thanks Blake
The formula works out to 17.5??
Do i have to change the drive gear or sumthing aswell? How hard is it to change the drive gear?
Thanks Blake
#48
Orange SS
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Posted 18 June 2009 - 03:12 PM
Hi,
Ive just changed to a 3.55 diff(was 2.78) and have 215/60/14 on rear and 195/60/14 on front.
Can anyone tell me which speedo gear to put in the trimatic I have.
cheers
Ive just changed to a 3.55 diff(was 2.78) and have 215/60/14 on rear and 195/60/14 on front.
Can anyone tell me which speedo gear to put in the trimatic I have.
cheers
#49
rodomo
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Posted 18 June 2009 - 11:30 PM
I have a trimatic, 2.78 diff, the white drive gear (8 tooth) and my tyre diameter is 651mm (225/60/15).
The formula works out to 17.5??
Do i have to change the drive gear or sumthing aswell? How hard is it to change the drive gear?
Thanks Blake
Your's is a bit difficult.
If you use a 17 tooth, it will make your speedo read faster than the car is going and might save you a fine here and there.
It would be closer with a blue drive gear in the trans and a 20 tooth driven gear in the cable but the speedo would be reading slower than the car is going.
I'd go the 17 with the 8 if it were me.
You would have to remove the extension housing to change the drive gear. You can do it in the car but a pain in the butt.
#50
rodomo
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Posted 18 June 2009 - 11:38 PM
Hi,
Ive just changed to a 3.55 diff(was 2.78) and have 215/60/14 on rear and 195/60/14 on front.
Can anyone tell me which speedo gear to put in the trimatic I have.
cheers
You would need a 24 tooth yellow gear in the end of the cable if you have a white gear in your trans.
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