Tire size questions

[firstgear]

Decided to mount the disc brake back plate and all for the rear axle....ok, this was a royal pain in the butt....talk about tiny spaces to get your fingers....

of course, after getting everything on, decided that really didn't need the back plate, just needed to get the axle snugged up and put the rear disc plate over the lugs.

of course Sharon came out while I was doing this little task and she heard some words that she normally doesn't hear from my mouth....I was not having a good time...but eventually I figured out a technique to get it together.....so I mounted the tire to see how that looked...

Kumho tire....255/55R17...nice meaty tire....looked real good in the above photo...

so off came the tire, the frame went back out into the other garage and the body came up off the body dolly and back down on the frame...this time I was much more careful in measuring from side to side and got the distance from the frame rail to the side of the body (put a 4' level across the wheel opening) to within 1/16" - 1/32"...figured that was close enough. Also had the edge of the axle housing left and right with in the same 1/16" - 1/32" with the panhard bar adjusted up snug.

Didn't look bad from the side....actually looked pretty good!

of course while I was doing this, Sharon wanted to be on task too, so I had her attack the DeWitt radiator with the Mothers polishing paste....came out pretty shinny....very nice job when she was done..

when you look down the side from the REAR looking FORWARD

There is about 5/8" of rubber pearing out the backside, the next shot shows the tire moved over to the other side and same resulting amount sticking out...

looking from the FRONT to the REAR

You can see in the above photo that the front side of the wheel well does a nice job of covering the tire....it is just in the back 1/2 as the fender starts to sweep back slightly that the tire gets exposed....which is what I am trying to avoid.....

I took the tire and laid it down flat on the floor and then put my 4' leve across the top of it. Measuring from the floor to the top of the tire, the tire had a section width on the rim of just under 10.5". Checking the Kumho web site, the tire I have is supposed to have a 10.4" section width when measureed on an 8" rim, which is exactly what I had.

so far so good.....if I want to narrow up the tire slightly, but stay with my 8" rims, I am looking at the same style of tire, but rather than a 255/55R17 with the 10.4" section width, I am looking at 234/45R17 with a 9.3" section width on an 8" inch rim.

I am figuring that the difference from 10.4 - 9.3 = 1.1" , I think that half of that will come off the back of the tire and half of that will come off the front of the tire...hence I will reduce the tire width or bulge by .55"

Looking at some other section widths, but not on 8" rims (but they fit an 8" rim)..... a 215/45R17 has a section width of 8.4" on a 7" rim (fits rims 7-8")....so perhaps I can't gain all of the reduced section width with this tire, but I can come closer.....

One other option is to go with a GoodYear Run Flat tire (since I do not plan on having a spare tire in the trunk this might make the most sense)...they have a tire that is 225/45ZR17....GoodYear doesn't give section widths on mounted rims, but the Kumho tire on a 7.5" rim has a section width of 8.9"....if I figure that going from the 7.5" to an 8" rim will add 0.5", then I would be at 9.3" section width (did I figure that right?)...so I am back where I was trying to get....I think.....anyone have comments on what I am trying to figure out here? Help?????

 

[WayneC]

The only comment I can make is from an info screen on the tire calculator of this website...

"This calculation is the straight inch equivalent of the section width you selected. The section width of a tire varies depending on the width of the wheel on which it is mounted. Tire manufacturers list a "design rim width" for each tire. This rim is used to determine the official section width. Most manufacturers say that the section width changes about 2/10 inch for each 1/2 inch change from the design wheel width.

For precise information, consult the tire manufacturer's specs."

Hope that helps.

 

[firstgear]

The only comment I can make is from an info screen on the tire calculator of this website...

"This calculation is the straight inch equivalent of the section width you selected. The section width of a tire varies depending on the width of the wheel on which it is mounted. Tire manufacturers list a "design rim width" for each tire. This rim is used to determine the official section width. Most manufacturers say that the section width changes about 2/10 inch for each 1/2 inch change from the design wheel width.

For precise information, consult the tire manufacturer's specs."

Hope that helps.

that does help...thanks Wayne....Herb

 

[IH2LOSE]

How much room did you have between the tire and the body tub?

Mine was real close there, I like your wheel choice.

Comment on your better half. I am sure you have heard it before

A family that plays together stays together, Its great to see other family memebrs invoulved

 

[firstgear]

How much room did you have between the tire and the body tub?

Mine was real close there, I like your wheel choice.

Comment on your better half. I am sure you have heard it before

A family that plays together stays together, Its great to see other family memebrs invoulved

I checked that out and it looked to be at least an inch...but not much more...I took the tire and wheel back yesterday...changing size to a 225/45R17...it is 1.4" less in section width than the 255/55R17....so I am figuring about .7" per side less width...that should get the back of the tire VERY close to being tucked in under the wheel well..the front of the wheel was already tucked under....so that should open up the clearance with the body tub even more.

Also, this new tire is a little over 2 to 2.5 inches smaller in diameter, so that should provide more clearance and enable me to drop the shocks to the lowest mounting point if need be....I have 3 adjustment points on the shocks where they mount on the axle housing....stay tuned...tire should be in tonight...then a check out....and photos....

 

[firstgear]

ok...tried the new tires....yuck....they are rubber bands on a rim....about 3" smaller in diamter...doesn't sound like a lot but when you look at the wheel well, you realize that it just isn't going to work....so now I am zeroing in I think....Michelin Pilot sport A/s 235/55WR17 has a section width of 9.5" on an 8 inch rim....this is less than the 10.4" that the 255/55R17....and the height of the 235 tire is 27.3" versus 28" for the 255 tire...so back to the tire store tomorrow and try to get the 235/55 WR17 from Michelin.....the smaller tire did stay nicely under the wheel well...but the diameter just looked HORRIBLE...I do have some adjustment on the ride height....but not enough to make up the difference in tire diameter.....here are some photos...

even when I had the car down on the wheel....it didn't really look any better...yes with the motor and everything else it will sit a little lower...but not enough to overcome this look.....

the tire is not as meaty as the last one, but then none of it extends out past the wheel well either....in this case it is perfect...but I can't get past how it doesn't fill the wheel well.....

I don't want to tub this, but if I had to just slightly it would not be the end of the world as I knew it! If more room is needed, it certainly isn't so much that it owuld cause me not to be able to use the soft top...

you can see that I am in the center of the height adjustment...I could drop it some more, but that dang tire is just tooooo small....so back to the store tomorrow....perhaps by Thursday I will have the next tire to try....they always have to get from the distributor and that takes a day....stay tuned....