need advice on 20" tires - The 1947 - Present Chevrolet & GMC Truck Message Board Network

NicoSlam · 03-23-2010, 11:00 AM

I purchased a set of boss 315 20" (8.5") with 305/50/20 tires. I tried to fit on my truck but the tire was obviously too big for the front. The rear fit with 1.25" spacers but I need help on selecting the front tires. What is the narrowest tire I can put on an 8.5" rim? I see many threads where 255/40/20seem to be common but can I go narrower. Once I select the width I can play with the aspect ratio to match the rear. I have a 1969 with a 4/6 drop. Pics of trucks with 20"s on 1967-70 with a 4/6 drop would be great.

NicoSlam · 03-25-2010, 03:08 PM

Anyone???

72BlckButy · 03-25-2010, 03:19 PM

I saw this thread yesterday, but forgot to respond.

IMO... the best tire size to run (on an 8.5" rim) will be a 255/40 up front and a 295/40 in the rear. For an 8" rim I would change it to a 245/40. On this type of decision... I prefer to not have a lot of space between the wheel/tire setup and the fender (I like it to not look 'spacey')

Do you know the BS on the 20's?

NicoSlam · 03-25-2010, 03:34 PM

Spacing looks to be 5.5". I tried them on on they fit great even the centercap. Unfortunately, I couldn't get out of the driveway without the tire rubbing on one of the innerfender bolts. The rim looked to have good position but the 305/50/20 seemed too wde.

hemihead · 03-25-2010, 10:18 PM

Thats a huge tire for the front, I went with a 255 45 on a 8.5 inch rim and a 295 40 rear on a 10" wide.

cstm68 · 03-26-2010, 01:42 AM

im running a 275-45-20 4-6 drop before i went to bags and never had a problem

epashhans · 03-26-2010, 01:18 PM

Hey Nicoslam, here is a post with some pictures of the rims/tires I have. They are boss's as well.

http://67-72chevytrucks.com/vboard/s...d.php?t=370922

And here is another thread with the same photos but a little bit of a write up on what I did.

http://67-72chevytrucks.com/vboard/s...d.php?t=389784

Hope some of that helps! I know some people think the tires look to big, but I don't like the look or ride of rubber bands.

When you get something figured out, make sure to post some pics!

NicoSlam · 03-26-2010, 01:26 PM

Thanks for all the advice. I'm going to get new tires for my tundra so I'll use the old ones as a start point. they are 275/50/20. I'll get picks up this weekend. I'm also doing the saginaw to A833 swap also. Will be an interesting weekend.

72BlckButy · 03-26-2010, 01:39 PM

Nico... can you explain the A833 swap? Sorry... haven't seen that one before.

epashhans · 03-26-2010, 02:04 PM

You got a 440 in that thing? That WOULD be quite different...mopar driveline in a chevy. I'm liking that!

I should put the 454 out of my truck in my charger and the 440 out of the charger in my 67...kidding!

NicoSlam · 03-26-2010, 02:09 PM

The A833 or MY6 is a 4speed floor shift tranny with 4th gear being overdrive (.67) that came out on the early 80's chevy 1500. It's the same length as a saginaw so theres no need to modify driveshaft. At 70mph, you can cruise at 2100rpm. Has similar gears as a 700R4

NicoSlam · 03-26-2010, 02:27 PM

Not the best pic but this is what it looks like: The trans originally was created by mopar but seems chevy borrowed the design in the 80's

72BlckButy · 03-26-2010, 02:24 PM

Thanks for the explanation!

Keep us posted on the install...

grancuda · 03-26-2010, 03:03 PM

I have been looking for one of those 4 speed OD manuals for a while

NicoSlam · 03-26-2010, 03:18 PM

Grancuda, you and me both. I must of hit all the Junk yards in San Antonio. did find several mopar versions but no MY6. I ended up finding one through another forum. I bought it and literally the next day, I found another so I bought it too. Anyway, I have an extra one. Nogalitos gear has a rebuilt one on the shelf but they want $750. It was a little high for me. Passion performance can rebuild for about $500 if needed. I've ordered all my seals and gaskets from them.

grancuda · 03-26-2010, 05:03 PM

you looking to sell you extra one?

NicoSlam · 03-26-2010, 05:09 PM

Grancuda. look at your PM. We cant discuss on thread

NicoSlam · 03-29-2010, 09:53 AM

I had issues with the tranny hitting the cab floor so I didn't have a chance to install the wheels. Here is a better pic of the wheel I took this weekend.

72BlckButy · 03-29-2010, 02:14 PM

Nice looking wheel Nicoslam!

NicoSlam · 03-31-2010, 04:19 PM

Any tire size suggestions and pics with a 4/6 drop?

epashhans · 03-31-2010, 04:57 PM

I thought you were going with the tires off the tundra?

Did you look at this thread?

http://67-72chevytrucks.com/vboard/s...d.php?t=361157

There are lots of pics and tire sizes in there...mostly on 3/5 or lower drops.

71bb_lwb is running close to what you would be with a 4/6...275/45/20

72BlckButy · 04-01-2010, 02:20 PM

Quote:

Originally Posted by NicoSlam

Any tire size suggestions and pics with a 4/6 drop?

Still sticking with my suggestion of 245/40 or 255/40 for the front and 295/40 for the rear.

NicoSlam · 04-03-2010, 10:20 PM

Finally got the tires installed today. I decided on the 275/45/20 Falkens. The front is perfect but the back needs o be spaced out about 1.5". The rims are Boss 315 8.5" with 5.5" back space. I have the 4/6 ECE drop and am thinking of going down another 1/2" using 2" frt spring and 1/2" spacer for the rear. Anyway, thanks for everyones support and suggestions.

72swb_327stroker_? · 03-31-2010, 08:11 PM

275/45/20 x4

5/7 drop very close to 4/6 and no rubbing with my drop which is an inch lower all 4 corners.

Wheels are 20x8.5 all 4 corners.

72BlckButy · 04-03-2010, 10:43 PM

Looks good Nico... I've got an update as well...

Wheel/tire specs over on my build thread.

255/40-20 and 295/40-20

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03-23-2010, 11:00 AM	#1
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	need advice on 20" tires I purchased a set of boss 315 20" (8.5") with 305/50/20 tires. I tried to fit on my truck but the tire was obviously too big for the front. The rear fit with 1.25" spacers but I need help on selecting the front tires. What is the narrowest tire I can put on an 8.5" rim? I see many threads where 255/40/20seem to be common but can I go narrower. Once I select the width I can play with the aspect ratio to match the rear. I have a 1969 with a 4/6 drop. Pics of trucks with 20"s on 1967-70 with a 4/6 drop would be great. Attached Images

03-25-2010, 03:08 PM	#2
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires Anyone???

03-25-2010, 03:19 PM	#3
72BlckButy Tot Roddin' Join Date: Apr 2005 Location: Mid-MO Posts: 24,461	Re: need advice on 20" tires I saw this thread yesterday, but forgot to respond. IMO... the best tire size to run (on an 8.5" rim) will be a 255/40 up front and a 295/40 in the rear. For an 8" rim I would change it to a 245/40. On this type of decision... I prefer to not have a lot of space between the wheel/tire setup and the fender (I like it to not look 'spacey') Do you know the BS on the 20's? __________________ -Nate 1969 CST SWB - Project Blank Slate (4.5/6" ECE Static Drop, 6-lug disc brake upgrade (manual), Billet Specialties Vintec 20x8.5 255/40 (F) 20x10 295/40 (R), 250 I-6) 1960 AMF Skylark - Tot Roddin' (Lowered with custom frame; soon to include custom push bar and interior) 2008 Silverado CrewCab 1LT (5.3L, 3:73, 4x4, LT1, Z-71, Towing Package) Last edited by 72BlckButy; 03-25-2010 at 03:20 PM.

03-25-2010, 03:34 PM	#4
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires Spacing looks to be 5.5". I tried them on on they fit great even the centercap. Unfortunately, I couldn't get out of the driveway without the tire rubbing on one of the innerfender bolts. The rim looked to have good position but the 305/50/20 seemed too wde.

03-25-2010, 10:18 PM	#5
hemihead Registered User Join Date: Mar 2007 Location: Estevan, Sask, Canada Posts: 185	Re: need advice on 20" tires Thats a huge tire for the front, I went with a 255 45 on a 8.5 inch rim and a 295 40 rear on a 10" wide. __________________ 1967 SWB C-10, BBC 454, T400, 3.73 posi, 20" Coys 1972 K5 Blazer, SBC 400, 4 spd, 3.73, 6" lift, 35" mud grapplers 2011 Sierra Denali HD, 6.6 L Duramax, RBP 96R rims, leveled and Nitto trail grapplers, 2009 Acura MDX

03-26-2010, 01:42 AM	#6
cstm68 Registered User Join Date: Jan 2007 Location: shoreline, wa Posts: 1,565	Re: need advice on 20" tires im running a 275-45-20 4-6 drop before i went to bags and never had a problem __________________ 68 swb fleet bagged on 20's 327 with 4 speed http://67-72chevytrucks.com/vboard/s...d.php?t=223308 2014 Chevy 2500hd duramax CCLB

03-26-2010, 01:18 PM	#7
epashhans Registered User Join Date: Jul 2009 Location: MT Posts: 319	Re: need advice on 20" tires Hey Nicoslam, here is a post with some pictures of the rims/tires I have. They are boss's as well. http://67-72chevytrucks.com/vboard/s...d.php?t=370922 And here is another thread with the same photos but a little bit of a write up on what I did. http://67-72chevytrucks.com/vboard/s...d.php?t=389784 Hope some of that helps! I know some people think the tires look to big, but I don't like the look or ride of rubber bands. When you get something figured out, make sure to post some pics! __________________ '67 C-10 Shorty - 454, 5spd, and speed holes!

03-26-2010, 01:26 PM	#8
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires Thanks for all the advice. I'm going to get new tires for my tundra so I'll use the old ones as a start point. they are 275/50/20. I'll get picks up this weekend. I'm also doing the saginaw to A833 swap also. Will be an interesting weekend.

03-26-2010, 01:39 PM	#9
72BlckButy Tot Roddin' Join Date: Apr 2005 Location: Mid-MO Posts: 24,461	Re: need advice on 20" tires Nico... can you explain the A833 swap? Sorry... haven't seen that one before. __________________ -Nate 1969 CST SWB - Project Blank Slate (4.5/6" ECE Static Drop, 6-lug disc brake upgrade (manual), Billet Specialties Vintec 20x8.5 255/40 (F) 20x10 295/40 (R), 250 I-6) 1960 AMF Skylark - Tot Roddin' (Lowered with custom frame; soon to include custom push bar and interior) 2008 Silverado CrewCab 1LT (5.3L, 3:73, 4x4, LT1, Z-71, Towing Package)

03-26-2010, 02:04 PM	#10
epashhans Registered User Join Date: Jul 2009 Location: MT Posts: 319	Re: need advice on 20" tires You got a 440 in that thing? That WOULD be quite different...mopar driveline in a chevy. I'm liking that! I should put the 454 out of my truck in my charger and the 440 out of the charger in my 67...kidding! __________________ '67 C-10 Shorty - 454, 5spd, and speed holes!

03-26-2010, 02:09 PM	#11
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires The A833 or MY6 is a 4speed floor shift tranny with 4th gear being overdrive (.67) that came out on the early 80's chevy 1500. It's the same length as a saginaw so theres no need to modify driveshaft. At 70mph, you can cruise at 2100rpm. Has similar gears as a 700R4

03-26-2010, 02:27 PM	#12
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires Not the best pic but this is what it looks like: The trans originally was created by mopar but seems chevy borrowed the design in the 80's Attached Images

03-26-2010, 02:24 PM	#13
72BlckButy Tot Roddin' Join Date: Apr 2005 Location: Mid-MO Posts: 24,461	Re: need advice on 20" tires Thanks for the explanation! Keep us posted on the install... __________________ -Nate 1969 CST SWB - Project Blank Slate (4.5/6" ECE Static Drop, 6-lug disc brake upgrade (manual), Billet Specialties Vintec 20x8.5 255/40 (F) 20x10 295/40 (R), 250 I-6) 1960 AMF Skylark - Tot Roddin' (Lowered with custom frame; soon to include custom push bar and interior) 2008 Silverado CrewCab 1LT (5.3L, 3:73, 4x4, LT1, Z-71, Towing Package) Last edited by 72BlckButy; 03-26-2010 at 02:24 PM.

03-26-2010, 03:03 PM	#14
grancuda Registered User Join Date: Nov 2007 Location: Central OK Posts: 396	Re: need advice on 20" tires I have been looking for one of those 4 speed OD manuals for a while

03-26-2010, 03:18 PM	#15
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires Grancuda, you and me both. I must of hit all the Junk yards in San Antonio. did find several mopar versions but no MY6. I ended up finding one through another forum. I bought it and literally the next day, I found another so I bought it too. Anyway, I have an extra one. Nogalitos gear has a rebuilt one on the shelf but they want $750. It was a little high for me. Passion performance can rebuild for about $500 if needed. I've ordered all my seals and gaskets from them.



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03-26-2010, 05:03 PM	#16
grancuda Registered User Join Date: Nov 2007 Location: Central OK Posts: 396	Re: need advice on 20" tires you looking to sell you extra one?

03-26-2010, 05:09 PM	#17
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires Grancuda. look at your PM. We cant discuss on thread

03-29-2010, 09:53 AM	#18
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires I had issues with the tranny hitting the cab floor so I didn't have a chance to install the wheels. Here is a better pic of the wheel I took this weekend. Attached Images

03-29-2010, 02:14 PM	#19
72BlckButy Tot Roddin' Join Date: Apr 2005 Location: Mid-MO Posts: 24,461	Re: need advice on 20" tires Nice looking wheel Nicoslam! __________________ -Nate 1969 CST SWB - Project Blank Slate (4.5/6" ECE Static Drop, 6-lug disc brake upgrade (manual), Billet Specialties Vintec 20x8.5 255/40 (F) 20x10 295/40 (R), 250 I-6) 1960 AMF Skylark - Tot Roddin' (Lowered with custom frame; soon to include custom push bar and interior) 2008 Silverado CrewCab 1LT (5.3L, 3:73, 4x4, LT1, Z-71, Towing Package)

03-31-2010, 04:19 PM	#20
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires Any tire size suggestions and pics with a 4/6 drop?

03-31-2010, 04:57 PM	#21
epashhans Registered User Join Date: Jul 2009 Location: MT Posts: 319	Re: need advice on 20" tires I thought you were going with the tires off the tundra? Did you look at this thread? http://67-72chevytrucks.com/vboard/s...d.php?t=361157 There are lots of pics and tire sizes in there...mostly on 3/5 or lower drops. 71bb_lwb is running close to what you would be with a 4/6...275/45/20 __________________ '67 C-10 Shorty - 454, 5spd, and speed holes!

04-03-2010, 10:20 PM	#23
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: need advice on 20" tires Finally got the tires installed today. I decided on the 275/45/20 Falkens. The front is perfect but the back needs o be spaced out about 1.5". The rims are Boss 315 8.5" with 5.5" back space. I have the 4/6 ECE drop and am thinking of going down another 1/2" using 2" frt spring and 1/2" spacer for the rear. Anyway, thanks for everyones support and suggestions. Attached Images

03-31-2010, 08:11 PM	#24
72swb_327stroker_? knuckle buster.. Join Date: Oct 2007 Location: Frisco Posts: 613	Re: need advice on 20" tires 275/45/20 x4 5/7 drop very close to 4/6 and no rubbing with my drop which is an inch lower all 4 corners. Wheels are 20x8.5 all 4 corners. Attached Images __________________ _______________________________________________________________________________ Eric THIS SITE ROCKS!!! Check out my suburban on 20's with fresh paint! Click here to support the site Check out the Member Photo Gallery here StreetCruizin FAQ thread Site vendors list (scroll down to vendors in red) join the the smilies fight club

04-03-2010, 10:43 PM	#25
72BlckButy Tot Roddin' Join Date: Apr 2005 Location: Mid-MO Posts: 24,461	Re: need advice on 20" tires Looks good Nico... I've got an update as well... Wheel/tire specs over on my build thread. 255/40-20 and 295/40-20 __________________ -Nate 1969 CST SWB - Project Blank Slate (4.5/6" ECE Static Drop, 6-lug disc brake upgrade (manual), Billet Specialties Vintec 20x8.5 255/40 (F) 20x10 295/40 (R), 250 I-6) 1960 AMF Skylark - Tot Roddin' (Lowered with custom frame; soon to include custom push bar and interior) 2008 Silverado CrewCab 1LT (5.3L, 3:73, 4x4, LT1, Z-71, Towing Package) Last edited by 72BlckButy; 04-04-2010 at 12:25 AM.

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