MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

Go to Thread: PreviousNext
Go to: Forum ListMessage ListNew TopicLog In
Goto Page: Previous123
Current Page: 3 of 3


rficalora
Rob Ficalora
Willis, TX
(2764 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: GB replica minilite wheels?
Posted by: rficalora
Date: February 28, 2008 02:03PM

MGBV8 Wrote:
-------------------------------------------------------
> Joe Schafer has 245/50-15s out back. Not sure they
> are really under the flare, though. In any case, I
> think that is about big enough. Bigger tires are
> heavier & usually more costly.

He does, and they're close, but don't quite fit. We traded mails a few months back; I know the rear wheels are 15x8. I'll have to dig up my notes to get the backspace & rear axle width.

Note, the 245/50/15's are down to one supplier for a street tire -- Dunlop SP Sport 8000. Z rated, high performance summer tire. About $170ea @ tirerack.com. I wanted them, but couldn't justify the cost + was worried that in another few years they may be NLA.



Edited 1 time(s). Last edit at 02/28/2008 05:47PM by rficalora.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: GB replica minilite wheels?
Posted by: BlownMGB-V8
Date: February 28, 2008 04:25PM

I went out and measured the Centerlines I'm running, turns out my memory is less than perfect, what a surprise. They are 7" wide (the BFG 265/50-14's are 10" wide) with a nominal 3" backspacing that is closer to 2-7/8". With the stock axle they could probably be moved in some but I'd have to take a closer look. That would seem to suggest that a 3-1/2" backspaced wheel would fit and maybe as much as 4-1/2" depending on the tire and overall rim width, I'll know more after a closer look. However, that's with an additional 1-1/2" of tire bulge (per side). Taking that into account it would seem that we would have something close to 5"+ clearance from the hub to the inside. Can't use my car to determine clearance to the outside of course, but to the inside I can get. Hopefully I can take a closer look tomorrow.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: GB replica minilite wheels?
Posted by: MGBV8
Date: February 28, 2008 10:11PM

Jim,

It's obvious form this pic that your tires are srceeming for more rim:

http://www.britishv8.org/MG/JimBlackwood/JimBlackwoodB-15.jpg

You are losing a lot of potential footprint by using less than optimal rim width. I'd bet that those tires were supposed to be mounted on a 8-10" wide rim with 8.5-9" being the optimal width.


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: GB replica minilite wheels?
Posted by: MGBV8
Date: February 29, 2008 10:40AM

"They are 7" wide (the BFG 265/50-14's are 10" wide)"

So with your 90% rule, you should be using 9" wide rims.

Good tire/wheel info:

[www.yokohamatire.com]


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: GB replica minilite wheels?
Posted by: BlownMGB-V8
Date: February 29, 2008 11:20AM

Another Blackwoodian response here.

What you say appears to be true Carl. However the spec sheet for the tires (BFG publication no. 0-3069-GT) lists the following data: BFG Recommended Rim Width Range 8.0-10.5, Tire and Rim Association design rim width 7.0 (Dimensions are taken with the tire mounted on this rim). Tread wear when mounted on this rim is flat and even, suggesting full tread contact.

This illustrates a somewhat different philosophy on tire and rim selection, and a very valid one for street driven cars. Rubber is harder to damage than aluminum and a street driven car will encounter many obstacles. In particular we do not see curbs on the race track, but they are a constant when parallel parking. Considering that wheels are usually more expensive than tires and more easily damaged by hard objects it is not at all unreasonable to use the tire sidewall as a protective buffer and this was an established standard manufacturer's practice up until the advent of the rubber band tire.

I had the tires (and the spec sheet) prior to buying these wheels, but the first set were also mounted on 7" wheels, and happy with the results I stayed with that width. I have never damaged a rim with this configuration. (Unless you count drifting sideways into a curb and breaking the center out of a Cragar SS. But the tire didn't survive that either. )

Much has been made of late about sidewall flex in terms of handling response and overall grip and I do not doubt the validity of those arguments. On the track this is very persuasive, and I could probably pick up a few tenths with maximum width rims. But my car is rarely track driven, and on the street it is already so fast that if I'm losing traction around a blind turn there'd better not be anything in the road because there's not enough reaction time left to avoid it. To me this is a valid limiting factor and a very big sign that it's time to slow down. I don't think I need to be going any faster than that, so in short I've built the car up to the level of my own limitations and not beyond. I'm happy with it as it is. The car helps me stay out of a potentially deadly situation.

Of course, an 8" rim would have a more common backspacing of 3-1/2" (locating the tire in the same place) while a 10" rim would be 4-1/2" but the 8 would contribute nothing otherwise and the 10 is still 1/2" below the max and would not therefore put the apex side sidewall in tension early enough to help handling much. The spec on treadwidth is 8.35" (although it's closer to 9-1/2 on the well worn tires shown below) and section width is 10.37" (full depth tread mounted on the 7" rim). So a 10-1/2" rim could arguably put the lip of the rim outboard of the sidewall. Not the combo I want to be driving on the street.

Here's a photo of this wheel in the GT wheelwell:
MVC-438S.JPG

MVC-439S.JPG

MVC-440S.JPG

MVC-441S.JPG

On my car there is 1-5/8" of clearance on the inside (+1/4" passenger side). Add that up and it's 3-1/2" total. Allowing 1/2" for the shock bolts we still have 3" to play with on a stock width axle, meaning that the same wheel and tire with a 4-1/2" offset would certainly rub due to sidewall flex, while an 8" wheel might not. That with a slightly narrower tire certainly would not, but it appears from the photos that the Omni flares might cover this tire. (which is NLA)

So there are some more dimensions to play with. Hopefully someone can get us from there to an idea of what we should be looking for in wheels.

The diameter can be increased on the rear as well, up to 27" and I'd suggest we think about doing this as it should make the tire selection easier and give more traction. It does mean the tire has to go deeper into the wheelwell though to maintain the ride height, which could adversely affect our suspension travel.

Any tire choice selections?

Jim


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: GB replica minilite wheels?
Posted by: MGBV8
Date: February 29, 2008 12:11PM

Looks perfect! :)

"It does mean the tire has to go deeper into the wheelwell though to maintain the ride height, which could adversely affect our suspension travel."

That Omni flare is not going to allow a lot of suspension travel.

"The diameter can be increased on the rear as well, up to 27"

There you go adding unsprung weight. ;)

If you want the Prostars, we gotta stay with a 15" rim. A 225/60 would be taller, but a bit narrower. There are a lot of choices in the pricier 17". Feeding tires to that 455 is gonna get expensive.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: GB replica minilite wheels?
Posted by: BlownMGB-V8
Date: March 01, 2008 03:10PM

I'd rather stay as far away from expensive tires as we can, at least for now. But out of curiosity, is there a 17" tire with a section width of 10 or 11" and a diameter between 24 and 27"?

We may be stuck with more unsprung weight than we'd like. Seems lightness is expensive.

Jim



MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: GB replica minilite wheels?
Posted by: MGBV8
Date: March 01, 2008 07:01PM

275/40-17
285/40-17
315/40-17

Won't be cheap & won't be light. The tire by itself will weigh within a pound or two as my wheel/tire combo. Ouch!


Phillip G
Phillip Leonard
Kansas City
(395 posts)

Registered:
02/03/2008 04:12PM

Main British Car:
1992 MG RV8 Rover 3.5

Re: GB replica minilite wheels?
Posted by: Phillip G
Date: March 01, 2008 08:39PM

Martin Harvey,

Good evening,

I see your Ford 9 inch axle in the britishv8 web site.

I am building an SCCA GT 2 class RV8 for club racing and will ultimately want to move to a Ford 9 inch rear axle.

Is your Ford 9 inch up for sale and how much would you need for it ? Of particular value is the 3.25 limited slip differential .

We will be club racing with a RV8 3.5 and will need a better final drive than our present MGB banjo housing "locked" 3.90 final drive.

regards,

Phillip leonard
Kansas City
pleonard@kcnet.com


Mr. T
Tony Andrews
Kent Island, Maryland
(153 posts)

Registered:
10/23/2007 03:59PM

Main British Car:
'75 mgb, '74 grille, morspeed bumpers Rover 3.9

authors avatar
Re: GB replica minilite wheels?
Posted by: Mr. T
Date: March 04, 2008 08:46PM

Hey Guys,

Food for thought - Don Allen's wheels (same size tires that Carl mentioned) may compliment your project.

Chevrolet rally wheels: 15x7 with 4.25" backspacing and 205/55 tires in front, and 15x8 with 4.00" backspacing and 225/50 tires in the rear.
DonAllen-A.jpg
Goto Page: Previous123
Current Page: 3 of 3


Sorry, only registered users may post in this forum.