1969 skylark wheel and tire size

[Will]

does anyone know what the largest wheel and tire combo i can fit under my 1969 buick skylark, without any major modifications, i would also like to use a slick and need to find a tire that will fit

[lcac_man]

The rear requires careful measurement for backspacing in order to get a large tire in the wheel well, I've seen 295-50's in the rear of a 69 GS, but there was some trimming of the fender inner lip to get them in there and I think he still had some light rubbing.
A 275-50 will fit with no trimming and no rubbing if your backspacing is correct, I used and 8" wheel with 5" of backspacing on mine and they fit perfect.
A 235 or 245-60 is about as big as you want to go on the front without upgrading steering and suspension components. With a 7" wheel, 4" of backspacing works well.

[greg davis]

at a event in a Kentucky city about 3 years ago someone showed me their car with 275/50-15 on it with no trimming at all, they said they were 8.5" wide with 5.25" backspacing.

on my 68 i chickended out and used 235/60-15 BFG DR on ralleye wheels.

i would love to step up to the 275/50'a as i can still spin them from a dead stop but do they hook from a slight roll like street tires cant.

[gdbuick]

Just wondering how you made out with the replies on wheel sizes. I also have the same question fitting the most meat under a 69 skylark and found this subject doing a search. I had a guy tell me he runs 275/60/15 on 15 x8 w/ 4 1/2 back spacing on his 69. Same guy says he runs 15x8 5 1/2 back spacing 29.5 x 9.0 slick with a 1/4 spacer. Says he has a chevelle 12 bolt rearend.
I'm looking to buy something this winter.

Later
Greg

[lcac_man]

I spent alot of time measuring my 68, the absolute biggest tire you can get in there is a 295, if your using a 15x8 your backspacing will have to be 5.25", a 275 is a much nicer fit (what I went with) a 15x8 with 5" of backspacing gives you great clearance, no trimming required.

[gdbuick]

Thanks for the info. I'm no rim size expert but figured someone else has been through this before before I buy it and own it. I'll assume you are talking 275/60/15 series not 50 series. If so the only difference between what the other guy told me he runs is 4 1/2 backspacing and not 5" as you suggested. Interested what you have to say about 4 1/2 vs 5 " backspacing. I plan to buy new GS wheels from speciality wheel or CARS ordered to my backspacing needs. I'm trying not to make any body mods but may consider it if it was not seen from the outside.

Is that your grey primered 68 gs convertable with 16" torq thrust wheels pictured on this site ?

Thanks Greg

[lcac_man]

Yep, that's mine.
50 or 60 series makes no difference in tire width, only hieght.
A 275-50 is 275mm wide and the sidewall height is 50% of that (137.5mm)
A 275-60 is 275mm wide and sidewall hieght is 60% of that (164mm)
A 275-60 is probably 1.5" taller that a 275-50.
Backspacing and wheel wide are directly tied together, if the guy your talking to is running 15x7's then 4-4.5" of backspacing makes good sense, if your gonna step up to 15x8s then you'll need to go with 4.75-5.25" of backspacing, remember your trying to center the wheel in the well.
You measure backspacing from the back lip of the wheel to the hub surface, the lip is commonly counted as .5" so on a 15x7 wheel if you want to center the tire to the hub surface you would need 4" of backspacing (7/2=3.5+.5=4), typically the hub surface is about .5" farther toward the outter fender so you'd add that to the backspacing landing you at 4.5".
Same math applies to the 8" wide wheel, but the wider you go the more interference you run into (tailpipes and shockmounts).
HTH

[gdbuick]

Thanks for the technical low down. Never did understand the 50 vs 60 series tires, that helped a lot. Sounds like I'll stick with your recommended sizes of 15x8 with 5" back spacing and mount 275/60's on them. I'm running 4.11 gears so taller is better for reducing my highway rpm's.

Thanks
Greg

[lcac_man]

Make sure you've got good springs, that's a tall tire.

[gdbuick]

Well I checked out my 69 skylark when I got home last night. I have 245 mounted on 15X7 factory mags, not sure the back spacing. It looks like plenty of room to fit a tire/rim towards the back shock mount but only about 3/4 of an inch to the wheel body/trim. Is the extra metal hanging over the wheel trim protruding towards the wheel what everyone is talking about possibly trimming if needed ? If so I could live without that. Again I plan to order custom made buick rims/ backspacing for the rear and want to make sure I get the widest/tallest tire under there since I'm ordering.

After hearing the detailed replies it sounds like 15X8 with 5" backspacing with 275/60's will fit the 68/69 Buick skylark but what about a wider rim size say 15X8.5 with 5" or 5.25 backspacing. Interested in hearing from others before I order.

Thanks
Greg
69 455 buick skylark
Bellingham, Ma

[greg davis]

Actually in theory a 275 tire should be the same width in a 50 or 60 series tire with the 275 being the common, but looking at the spec sheet they are not.

the 50 series is wider. but it also varies by what size rim width the tire is mounted on, these specs do not use the same wheel width for both tires.

the info doesnt paste into this very well, it is much easier to read with the link below.

BFGoodrich Comp T/A Drag Radial

Serv. Desc. Load Rating UTQG Max
Load Max.
Inflation Press.
Tread Depth
Rim Width Range
Meas. Rim Width
Sect. Width
Tread Width
Overall Diam.
Revs Per Mile



235/60R15 SL 0 B C
1653lbs.
44psi
5/32nds
6.5-8.5"
7"
9.5"
8"
26.1"
794

275/50R15 SL 0 B C
1830lbs.
44psi
5/32nds
7.5-9.5"
8.5"
11.3"
10"
26.1"
791





http://www.tirerack.com/tires/Spec.jsp?make=BFGoodrich&model=Comp+T%2FA+Drag+Radial

[gdbuick]

Thanks for the info. Greg. Still hoping somebody chimes in with some maximum rim sizes and offsets that fit the 69 skylark with no mods or slight mods. Hopefully some of the race guys will chime in...

Later
Greg

[lcac_man]

You can go to a wider wheel, I looked at 9.5's backspacing will need to be 5.5"-5.75" and the shock mount becomes a real issue, you really need to go to a larger diameter wheel if you go past 5.625" of backspacing just to clear the lower shock mount (a 17" wheel will clear nicely) but you'll also need to consider tail pipe clearance.