G-body's with 20's

[DrRansom442]

Re: no reason to compare diffrences.

Since you know so much, what is the overall diameter of the tires I'm running? and what do you recomend the overall diameter should be?
or did you forget?

smidge over 27" overall ... above the recomended +/- 3% of factory height of 25.5". Your Speedometer (unless recalibrated) is now 6 % too slow and it's their widest point on your rims your tires are about 10" ... which means if you are lowerred or at stock ride height ... you got the lucky with wider, than every other G-body on the road, front wheel wells ... 9.5" at the widest point tires rub like hell in turns. Rears should have ZERO clearance issues with the right backspace rim. BTW before someone chimes in about their Regal or 4 door, they are a tad more forgiving.

p.s. a 78 isn't a G-body and yeah my siggy is off ... neither's the 81 but it looks just like the 82-86

Ok.. Went and took a look seems I made a mistake... I'm running 245's all around.. My old 17's have 255's on them..

So it looks like my overall tire diameter is 26.8" do you really think that is terribly tall?

And like I said no rubbing issues at all in the front period.. regardless of what you say.. I'm telling you my car does not rub and it's lowered.

You keep saying "donk" and my car is not even close to a donk, to be honest I can't stand them and would never own one (But I would never bad mouth somebody's ride because that's what they like either).

I wasn't aware my 78 monte is not a g-body could you tell me what it is?
Oh and how much do my rims/tires weigh too? lol..

245 on a 20 or a 17? and was the profile right? again within 26.5" overall is IDEAL, so you really are getting closer to that. I would honestly have to do some math ... I am doing this on paper and frankly ... it's been awhile. weights there are too many variables ... have them weighed ... typical factory sized tires on a steel 14" should be like 35 lbs (guestimate) ... an alloy 20" probably 60 lbs and up (again guestimate)

 

[78monte]

Re: no reason to compare diffrences.

Since you know so much, what is the overall diameter of the tires I'm running? and what do you recomend the overall diameter should be?
or did you forget?

smidge over 27" overall ... above the recomended +/- 3% of factory height of 25.5". Your Speedometer (unless recalibrated) is now 6 % too slow and it's their widest point on your rims your tires are about 10" ... which means if you are lowerred or at stock ride height ... you got the lucky with wider, than every other G-body on the road, front wheel wells ... 9.5" at the widest point tires rub like hell in turns. Rears should have ZERO clearance issues with the right backspace rim. BTW before someone chimes in about their Regal or 4 door, they are a tad more forgiving.

p.s. a 78 isn't a G-body and yeah my siggy is off ... neither's the 81 but it looks just like the 82-86

Ok.. Went and took a look seems I made a mistake... I'm running 245's all around.. My old 17's have 255's on them..

So it looks like my overall tire diameter is 26.8" do you really think that is terribly tall?

And like I said no rubbing issues at all in the front period.. regardless of what you say.. I'm telling you my car does not rub and it's lowered.

You keep saying "donk" and my car is not even close to a donk, to be honest I can't stand them and would never own one (But I would never bad mouth somebody's ride because that's what they like either).

I wasn't aware my 78 monte is not a g-body could you tell me what it is?
Oh and how much do my rims/tires weigh too? lol..

245 on a 20 or a 17? and was the profile right? again within 26.5" overall is IDEAL, so you really are getting closer to that. I would honestly have to do some math ... I am doing this on paper and frankly ... it's been awhile. weights there are too many variables ... have them weighed ... typical factory sized tires on a steel 14" should be like 35 lbs (guestimate) ... an alloy 20" probably 60 lbs and up (again guestimate)

245/35/20 is what I'm running right now.. These come out to 26.8" overall according to my math..

So you say a 78 monte carlo is not a g-body?

 

[dan2286]

A '78 is technically an A body.

 

[DrRansom442]

A '78 is technically an A body.

yes wasn't until 82 that the "G" came into existance .... the "A" designation was given to front drivers ... and ofcourse to confuse things even more 81 was the body change ... as such my car resembles the G in exterior but still used many of the 78-80 A components. Being a transitional year makes parts shopping fun at times. So if you really wanna bust my nuts ... my siggy should say 2 G s and 1 A

 

[DrRansom442]

OK working a tad smarter I just googled a tire diameter calculator ... instead of relying on paper and calculator ... life is easier.

to compare 3 sizes

195/75/14
25.51" overall height/7.67" section width
245/35/20
26.75" overall height/9.64" section width
255/35/20
27.02" overall height/10.03" section width

you can see just the height and width differences between the 245 and the 255 are pretty large 1/4" height and 1/3" width.

now the OP has a Cutlass. Cutlasses have very flat front fenders without the lip one sees on a Regal (and presumably simular to the lip on your A-body Monte) .... I posted 9.5" as a section width .... your tire size is splitting hairs being .14" over ... if your tires had rubbed once ... you'd probably have lost more material than that. Take a look at a Cutlass sometime rubbing the inside of the fender is what I'd be concerned with. Normally this can be compensated with a 1/4" deeper offset, but with that wide a tire ... now you're into the plastic inner fender.

 

[GP403]

A '78 is technically an A body.

yes wasn't until 82 that the "G" came into existance .... the "A" designation was given to front drivers ... and ofcourse to confuse things even more 81 was the body change ... as such my car resembles the G in exterior but still used many of the 78-80 A components. Being a transitional year makes parts shopping fun at times. So if you really wanna bust my nuts ... my siggy should say 2 G s and 1 A

Well, not to muddy the waters even more 8) but that's not exactly true either 😀 At least for pontiacs, the A designator was given to the Grand Am/LeMans for '78-'81, and the Grand Prix was a G from '78-'80. In '81 the GP was changed to "Asp" (A-special) or "AJ" as the parts book ('76-'81) has it listed.

I'm sure there is a similar difference for the Monte/Malibu and Century/Regal for '78-'81 as well. For the '78-'80 Pontiacs, the wagons and 4drs were A, and the GP which was 2dr only was a G, probably is the same.

 

[DrRansom442]

so the 4th digit in a 81 GP VIN is a G? That is honestly the first time I had heard that.

Pontiac VIN would start 1G3GK47 ?

 

[GP403]

so the 4th digit in a 81 GP VIN is a G? That is honestly the first time I had heard that.

Pontiac VIN would start 1G3GK47 ?

?

For '81 the 5th digit is the series code, and the GP's were coded as: J,P, and K, or base, LJ, and Brougham respectively, the Lemans were coded D and F, base and "Grand LeMans" (not Grand Am!)

Remember the A/G designator doesn't have anything to do with the VIN, its the body style code that GM used. I will copy that page from '78/'79 and '81 and post it up to a different thread 😀

 

[DrRansom442]

then it's a weird coincidence:

86 was GK47 (2 door Salon)
87 was GR47 (2 door Supreme)
81 has AK47 (2 door Calais)
I swore those were the same digits in the VIN, but the breakdown labels number 4 as restraint type

I'm really not up on my 13 digit VINs ... I only had one pre-80 car

 

[Robert]

My GP running on 265/35ZR20-rear+235/40ZR20-front Irocs without any problems, braking and handlich are nearly the same but in my garage still waiting Bilstein B6, Eibach ProKit, Energy Suspension Master Kit and a new front suspension kit so after that modifications i hope it will be even better...😀