Date: Tue, 1 Jun 1993 14:51:54 -0800 (PDT)
From: rck@fangio.asd.sgi.com (Robert Keller)
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
165/80-14 5.2in 12.2in 24.4in 76.6in 827 0.0%
175/70-14 4.8in 11.8in 23.6in 74.3in 853 -3.1%
Gee, that difference is very close to what I measured while driving
down the NJ turnpike on Memorial Day. My odometer was gaining about
0.2 miles every 10 miles. Wish I had thought to do that when I got
on, because I would have had a longer distance to measure.
Incidently, the NJ turnpike is one of the few roads where the mile
posts seem to be accurate. On the interstates, they can be up to 1/10
of a mile off, although they average about right.
James
From rwg1@postoffice.mail.cornell.edu Tue Sep 11 11:39:50 2001
From: (Roger Garnett) rwg1@postoffice.mail.cornell.edu
To: (British Cars) british-cars@autox.team.net
Date: 2 Jun 93 11:54:42
Subject: Re: Tyres for MGB rims
> I think I want to get new tyres for my '64 MGB.
> The car came with the original '64 steel rims (14" x 4.5").
> I currently > have my spare set of 'B tyres (175/70-14) on the car;
> they're mounted on > the later Rostyle steel rims, 14" x 5.5"
> Specification Sidewall Radius Diameter Circumference Revs/Mile
>Difference
> 165/80-14 5.2in 12.2in 24.4in 76.6in 827
>0.0%
> 175/70-14 4.8in 11.8in 23.6in 74.3in 853
>-3.1%
> 185/70-14 5.1in 12.1in 24.2in 76.0in 834
>-0.8%
We can add to this info from the +0 +1 +2 tire size chart, (unknown, 1988)
APPROX APPROX RIM
SIZE MEASURING SECTION OVERALL RANGE
RIM WIDTH DIAMETER FROM TO
155R14 4.5 6.18 23.78 4 5
165R14 4.5 6.57 24.49 4 5.5
175R14 5 7.01 24.96 4.5 6
185R14 5.5 7.40 25.59 4.5 6
175/70R14 5 6.93 23.86 5 6
185/70R14 5 7.32 24.57 5 6.5
185/60R14 5 7.24 22.76 5 6.5
> Any words of advice on which tyres to mount on early MGB steel rims?
OK, stock MGB was 155R14, and 165R14 on GT's. (At least until '75).
The charts would seem to indicate that you don't want to go any
bigger than 185R14's on a 4 1/2" rim. But numbers can be stretched
sometimes... A friend just put a set of 185/70R14's on his '69 with wire
wheels, which also measure 4 1/2", and they seem to fit pretty well.
Phil E. knows of an autocrosser who uses 186/60's on Rostyles- this is
good for auto-x, as you get a firmer ride, better grip, and better low end
gearing, but will make for a harsher street ride, with higher RPM's.
So- 175/70's should still work reasonably, but will also giver higher
RPM's due to the smaller diameter. The 185/70R14 seems to have about the
best diameter match, as long as you don't get rubbing, and has been known
to fit.
I've got a nice set of Aluminium 14x6 rims (from a Datsun Z?) which I'm
gonna trial mount a 185/70R14 on with hopes of putting them on Tilly's '74
GT that I drove out of the barn from a 1 1/2 year sleep last weekend.
As long as the offset is correct, they ought to work quite well, except
I think the car has a wire-wheel rear end, with disk wheel half-shafts
fitted, cuz I've had slight rubbing inside one of the current 165R14's.
This may be easily fixed with wheel spacers, or by swapping with a disk
rear which was from a '79.
________
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