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Correct Tire size for 620 trucks


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#1 chavezYchavez

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Posted 02 December 2009 - 01:26 PM

Guys,
getting ready to buy new tires and get rid of the 30 yr old Bias tires.

Here is what is currently on the truck P185/75B14

The stock tires where 6.00-14 what I have found on the net transforms the original tires to these options:
175/70R14

P175/75R14

185/65R14

185/70R14

195/65R14

205/60R14

I had my wife follow me in the truck and and when speedo read 75 she said I was only going 65 so looks like speedo is off 10 miles per hour with tires currently mounted?

I played around with this site trying to look at best soultion:
http://www.miata.net...e/tirecalc.html

Any help would to buy the correct stock tire size to try and correct the descrepancy would be greatly appreciated.
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#2 521ofdoom

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Posted 02 December 2009 - 01:47 PM

I've never used that small of a rim, but i'd look more toward 195/75/14's. Seems to be the size I take off every datsun truck I've bought.
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#3 Z-train

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Posted 02 December 2009 - 02:08 PM

I've never used that small of a rim, but i'd look more toward 195/75/14's. Seems to be the size I take off every datsun truck I've bought.


This is the size i have on my 620.
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#4 mike

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Posted 02 December 2009 - 02:56 PM

This might sound silly and I dont know if youre using the truck for actual work or whatnot but if it was me Id buy some different rims and tires all together and clean up those bias plies and original wheels and keep them for tooling around on sunny days. Ive been sort of looking for a full set of original spares for just this reason...

Ive got 195/75/14s on mine too, they fit about right but the speedo still reads off by about 10mph. I wouldnt mind a bit wider rim though so I could run something between 205 to 225 in width in a 60 or 70 series on a 14" rim or the same width in a 50 or 60 series on a 15. It rides nice with the taller sidewall, but I can sure feel the difference in the corners.

#5 Happy

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Posted 02 December 2009 - 03:00 PM

I would like to find an actual truck, or snow tire, that is the right size for the original rims.

#6 VoidDragon

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Posted 02 December 2009 - 03:23 PM

Mine came with 195/75/14 on stock rims. My speedo seems to be dead on, as I pass a 'your speed' display almost every day, and havn't noticed a difference between its readout and my speedo yet.

Since most tires don't have a true height designation, you'll have to use a tire/wheel calc to match up different tires and wheel combo sizes.

IE. 195 is width. 75 is a percentage of the width, and is the tires wall height. 14 is the inside diameter.

#7 moparvwfreak

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Posted 02 December 2009 - 04:05 PM

i have 1857014s on my 73 and the speedo is off by about 10mph. my 78 i put 1957514s and the speedo was dead on. so i would go with teh 19575s myself. as soon as i can afford to, i am swapping the rear tires onto my slots.
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#8 fastdadd

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Posted 02 December 2009 - 05:05 PM

the haynes manual states tire size is 6.00-14-6pr
and here is a conversion chart

"protractor" printhttp://www.turbinecar.com/tires.htm

looks like somewhere between 155/70 and 165/70

hope it helps

#9 datsunaholic

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Posted 02 December 2009 - 05:39 PM

The conversion chart isn't quite right. The width is right- 6 inches is 152.4mm, so a 155 width is right, but the 6.00PR14 have taller or equal sidewalls than they are wide so you'd need a 155/110 tire. No such thing exists.

In my travels the closest match on a 14-inch wheel is 195/75R14. That's actually nearly too wide for the older wheels which are extremely narrow, but it fits the wider disc-brake wheels from '78+ nicely.
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#10 nukeday

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Posted 02 December 2009 - 11:00 PM

Another member here suggested this site for 13" tires for the 510, they seem to have a good selection of 14" inch tires too.

My 521 has 195/75 R14's on it from about 1986...

Edited by nukeday, 02 December 2009 - 11:02 PM.

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#11 izzo

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Posted 02 December 2009 - 11:08 PM

did someone swap out the tranny at one time? is it 4 or 5 speed?

73 had a 4spd iirc
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#12 Braden

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Posted 03 December 2009 - 09:40 AM

I've never used that small of a rim, but i'd look more toward 195/75/14's. Seems to be the size I take off every datsun truck I've bought.


thats what i use, they are just big and small enough to be proportional, anything else would look too skinny
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#13 Suspect

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Posted 03 December 2009 - 01:56 PM

I've never had an accurate speedometer. Both my 73 and 74 are about 10 mph off, 70mph to do an actual speed of 60mph. My 77 is off 20mph, 40mph is actual speed of 60mph. It seems like I can't go tall enough tire wize to get any of them right.

#14 Braden

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Posted 05 December 2009 - 08:32 AM

for all of you titan guys, what size tires do you run on your 620? take into consideration i have a 3 inch static drop, i want to run a tire that protects the wheel from curb rash as much as possible, i hate it when the rim sticks out past the tire, i have seen several of you guys on here that had the size tire i want to run, also it needs to have almost as much profile as possible i dont want rubberbands
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#15 ggzilla

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Posted 05 December 2009 - 11:31 AM

Most Datsun speedometers are 5 to 10 mph off at 60mph. It is corrected with a little plastic speedometer gear that bolt to the side of the transmission.
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#16 bob72gts

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Posted 06 December 2009 - 12:01 PM

Ghettobraden my 77' has QX56 chromes on it, same dimensions as Titans, in the rear I am running 245/45/18 the front is 225/45/18. The tires are Bridgestone RE050 The truck is static dropped about 5", removed a leaf and 4" block in rear trimmed stops and cranked bars in front. To fit the rears I had to remove about half of the rolled under section of the wheel lip only on the left side of the truck, gotta love that Datsun fit and finish, the tires occasionally scrub the inner and outer sidewalls depending on terrain. The fronts only rub the fenders in tight tight turns, normal driving is fine. I should mention these sizes at this height will not work on a disc brake truck. I put them on my 79' KC first and didnt like the fit, so I bought and built the 77'

#17 Bob3

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Posted 06 December 2009 - 12:19 PM

I'm running 205/75/14's on my '78 kc on stock steel wheels.

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#18 Braden

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Posted 06 December 2009 - 12:23 PM

Ghettobraden my 77' has QX56 chromes on it, same dimensions as Titans, in the rear I am running 245/45/18 the front is 225/45/18. The tires are Bridgestone RE050 The truck is static dropped about 5", removed a leaf and 4" block in rear trimmed stops and cranked bars in front. To fit the rears I had to remove about half of the rolled under section of the wheel lip only on the left side of the truck, gotta love that Datsun fit and finish, the tires occasionally scrub the inner and outer sidewalls depending on terrain. The fronts only rub the fenders in tight tight turns, normal driving is fine. I should mention these sizes at this height will not work on a disc brake truck. I put them on my 79' KC first and didnt like the fit, so I bought and built the 77'


hey bob how about some pics? i would love to see how it sits, why cant you run discs? i will eventually be running the izuzu rotors and d21 calipers
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#19 bob72gts

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Posted 06 December 2009 - 01:28 PM

I will see what I can do about some pics, the only ones I have of that truck are printed.

As for discs..... Factory disc trucks have a significantly wider track width so the Titans won't tuck, and it is my understanding that the drum to disc conversions ad about a 1/4" to each side. On my truck there is no way I could sacrifice that 1/4". I guess you could roll the fender lips, but personally I dont think it looks right on a 620.

Future plans for my 79' KC include narrowing the front suspension to drum brake specs maybe a 1/2" narrower and installing the extra drum truck rearend I have, so I can use the extra set of 5 spoke Titans I have laying around.

There is a really old pic of my KC on Bleachgarage. Yellow with purple scallops it is pic #138 in 620 modified. That pic is from 1995.

#20 Braden

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Posted 06 December 2009 - 06:47 PM

I will see what I can do about some pics, the only ones I have of that truck are printed.

As for discs..... Factory disc trucks have a significantly wider track width so the Titans won't tuck, and it is my understanding that the drum to disc conversions ad about a 1/4" to each side. On my truck there is no way I could sacrifice that 1/4". I guess you could roll the fender lips, but personally I dont think it looks right on a 620.

Future plans for my 79' KC include narrowing the front suspension to drum brake specs maybe a 1/2" narrower and installing the extra drum truck rearend I have, so I can use the extra set of 5 spoke Titans I have laying around.

There is a really old pic of my KC on Bleachgarage. Yellow with purple scallops it is pic #138 in 620 modified. That pic is from 1995.


so basically as long as my wheels arent tucked any i could get away with it ?(untill i hit a bump!!!) surely some of the titan guys run discs, are your wheels bored? or spaced?
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