[xk] Modern tires on XK120

XK
1

Thinking about fitting modern tires on my XK120 roadster
1950 for better handling and look. Car is with disc wheels
and spats, and I want to keep it like this. Any
recommendations for size (195/80-R16?) and brand. Want to
go as wide as possible without losing the spats.
Currently run Vredestein 185/R16 classic.–
Per Lemser
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

2

Ours is also a 120 OTS with steel wheels and spats.

I like the look of the Dunlop roadspeeds (OEM) and have used nothing
else. That’s what was on the car in 1952 when it was rolled out in
Coventry. I figure Sir William’s judgement is good enough for me.

Bruce COn 9/6/2015 9:05 AM, Per Lemser wrote:

Thinking about fitting modern tires on my XK120 roadster
1950 for better handling and look. Car is with disc wheels
and spats, and I want to keep it like this. Any
recommendations for size (195/80-R16?) and brand. Want to
go as wide as possible without losing the spats.
Currently run Vredestein 185/R16 classic.

Per Lemser
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

3

In reply to a message from Bruce Cunningham sent Sun 6 Sep 2015:

Yes, but im pretty sure there have been some development
the past 50 years on the tire front. Fitted modern tires on
my e-type and handling improved dramatically.–
Per Lemser
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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4

In reply to a message from Per Lemser sent Sun 6 Sep 2015:

Hi Per,

I was in your situation some time ago concerning our XK140
FHC. I decided to buy 215 tires (the widest what is possible
with the disc wheels for the 140). I found the information
about that in this forum. Having installed them and
registered (for shure) I am very happy with this choice. But
I have removed the spats already before and did not try to
fit them afterwards, because I like the car better without.
Handling is much better than with the 185, I used before.

Best regards
Lindi–
lindi
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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5

good idea to put radials on the E (had them on my series 1 for the 5
years I drove it)) but the 120 has a very different rear suspension for
which radials are a bit unsafe - they let go rather suddenly rather than
drift and I enjoy the driftingOn 9/6/2015 10:07 AM, Per Lemser wrote:

In reply to a message from Bruce Cunningham sent Sun 6 Sep 2015:

Yes, but im pretty sure there have been some development
the past 50 years on the tire front. Fitted modern tires on
my e-type and handling improved dramatically.

Per Lemser
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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6

Hello Lindi,
I also have a 140 (DHC) with wire wheels. Do you know if the 215
tires will fit my(65 spoke?) wire wheels? Also did you use 215 on all
four wheels? What brand tire did you buy? Thank you in advance for
your answers.
Barry Simmons
S818044On Sep 6, 2015, at 10:26 AM, lindi wrote:

In reply to a message from Per Lemser sent Sun 6 Sep 2015:

Hi Per,

I was in your situation some time ago concerning our XK140
FHC. I decided to buy 215 tires (the widest what is possible
with the disc wheels for the 140). I found the information
about that in this forum. Having installed them and
registered (for shure) I am very happy with this choice. But
I have removed the spats already before and did not try to
fit them afterwards, because I like the car better without.
Handling is much better than with the 185, I used before.

Best regards
Lindi

lindi
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/
donate04.php –

7

In reply to a message from Per Lemser sent Sun 6 Sep 2015:

Per;
I have a 120 DHC fitted with Coker 600 R 16 Radial tires.
They fit within the wheel well and look just like the
original bias ply tires,
Their handling is very good, ride is good, wet weather grip
is FAR better than ANY bias ply tire. I could not be
happier with them. I have had many other brands and types
of tire on the car from Michelin 185R 16, (very good and
VERY expensive does not look original)
Continental 105 70 R16, (poor handling, poor grip, cannot be
used with inner tubes. I fount that out the hard way).
My car is regularly driven and driven vigorously so good
tires are important to me.–
Roger, '54 120 (SE) DHC, BRG, S678300
Tamarac, South Fla., United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

8

In reply to a message from Velocette sent Sun 6 Sep 2015:

Want to keep the spats so 215 is not an option. Already has
vredestein classics but want to replace them with modern
tires, not like the cokers/vredestien/Michelin. Know it
dosnt look original but prefer better handling for original
look. But thanks for the advise both…–
Per Lemser
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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9

Bruce and Lindi,
Please "read the question”, as my junior high school English teacher, Mr. Lipman, always told us, or as TV attorney Perry Mason said, “The witness is being unresponsive, your Honor” :wink:

  Cheers,
        The Jag Maven (Gary)> On Sep 6, 2015, at 8:26 AM, lindi <lindner.gmund@freenet.de> wrote:

In reply to a message from Per Lemser sent Sun 6 Sep 2015:

Hi Per,

I was in your situation some time ago concerning our XK140
FHC. I decided to buy 215 tires (the widest what is possible
with the disc wheels for the 140). I found the information
about that in this forum. Having installed them and
registered (for shure) I am very happy with this choice. But
I have removed the spats already before and did not try to
fit them afterwards, because I like the car better without.
Handling is much better than with the 185, I used before.

Best regards
Lindi

lindi
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

10

Been there, done that. What fits at tire store may foul the spats under dynamic load (turns/bumps). Strongly suggest anti-Frizbee Rx to both spats before any road testing; don’t ask me how I know! Also, test both sides for fit, as my side wall-spat clearance differs by 3/8” between rear wheels. FWIW, to save mounting hassles at tire store I have them consecutively mount a single tire under each spat in case the first side fits and the second doesn’t; you can ask me how I know, but I think you can guess.

In my experience choices are few given the requirement to fit under spats. Also, nominally identical sizes can vary in side wall width between manufacturers by up to 1/2 inches or so, IIRC. Vredsteins are promoted as “modern radial construction” with "classic style”, and may be as good as it gets.

   Cheers,
       The Jag Maven> On Sep 6, 2015, at 10:41 AM, Per Lemser <perlemser@lenovo.com> wrote:

In reply to a message from Velocette sent Sun 6 Sep 2015:

Want to keep the spats so 215 is not an option. Already has
vredestein classics but want to replace them with modern
tires, not like the cokers/vredestien/Michelin. Know it
dosnt look original but prefer better handling for original
look. But thanks for the advise both…

Per Lemser
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

11

In reply to a message from Per Lemser sent Sun 6 Sep 2015:

I’ve been using the Bridgestone Ecopia 195/80R-16 tires on
my XK120 for several years. I’m very pleased with their
performance, and there are no interference issues with the
spats. These are tubeless tires, so you can save the
expense of inner tubes if you have disc wheels. In the U.S.
these tires are available through tirerack.com for less than
$140 each plus shipping.

Regarding interference with the spats, the center of the
hubcap appears to be the closest point of contact to the
spat. When making a sharp turn, I believe it is the center
of the hubcap that first makes contact by pushing against
the folded bottom lip of the spat. This is exacerbated by
using the later Mark 2 hubcaps which look almost identical
to the original XK hubcaps, but whose center extends
outwards by an additional 1/2 inch. (Original style XK
hubcaps with the thinner profiles are no longer being
produced.) I no longer install the rear hubcaps when the
spats are installed. So far the spats are safe, and no one
has ever asked me about the missing rear hubcaps.

www.jag-lovers.org/snaps/snap_view.php3?id=1375917311--
The original message included these comments:

Thinking about fitting modern tires on my XK120 roadster
1950 for better handling and look. Car is with disc wheels
and spats, and I want to keep it like this. Any
recommendations for size (195/80-R16?) and brand. Want to
go as wide as possible without losing the spats.

–
Mike Balch
Iowa, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

12

This whole issue of TYRES (TIRES) is something you need to really assess
what you are trying to do.

Tyres and Wheels and their compatible/matching sizes is one of the first
things that attracted the interest of safety regulations in particular with
how the tyre fits and stays fitted to the wheel, and this ended up with some
very detailed rules/regulations regarding the rim profile and then the
construction of the tyre to properly match and lock into the rim profile.
It is no accident that it is so difficult to get a flat tyre off a rim, as
the bead of the tyre has deliberately locked into the rim of the wheel as it
was designed to.

Thus at speed and high cornering loads the tyre stays on the wheel, and
doesn’t peel off sideways as did the early non-safety rim tyres/wheels.

Where I am going on all of this is with grip of tyres, flexing of wheel and
rims, flexing of tyre side-walls, you really should NOT deviate unknowingly
from the design standards that applied to both DUNLOP - who made the wheels,
and to all the reputable ‘first-world’ country tyre manufacturers (don’t get
me started about Chinese made tyres!).

In the case of XKs, early wire wheels were 54 spoke, but from early XK150
they were changed to 60 spoke - not for appearance/good looks but because
once a 54 spoke painted wire-wheel was strong enough for side loading, but
as we all (most of us at least) know Chrome Wire Wheels are not as strong,
with the American interest in ordering optional Chrome Wire Wheels (rarely
ordered in other markets) Dunlop thought necessary to increase strength of
their wire wheels to having 60 spoke (regardless of whether Chrome or
painted).

Now radial tyres aggravate that problem compared to the then used Cross
(Bias) Ply tyres, which have far better grip and far more flexible
side-walls, thus a much greater propensity to dislodge from the wheel rim in
hard/extreme cornering.

Now our XK wheels were 5" rim width (16" diameter) and had a ‘JJ’
rim-profile.
The design tyre width for a 5"JJ x 16" rim is a 6.00" x 16" tyre, and up to
allowable 6.50" width.
Radial tyres (by agreement between UK and European tyre manufacturers) to
easily differentiate their radial/cross-ply construction quote radial tyre
widths in metric, so a 6.00" cross-ply width equates to a 155mm or 155R x
16" tyre, however the functional radial equivalent was agreed to be
perfectly acceptable on a 60 spoke (or disc) wheel to use a 175R x 16" tyre,
albeit apart from Michelin, not a common size, so close enough and generally
acceptable was to fit a 185R x 16" tyre.

So you see we already have had a lot of creep - 6.00" = 155mm, allow up to
175mm but then allow up to 185mm.
Cross ply tyre grip/lateral loading/firm side-walls OK with 54 painted
spokes or 60 chrome spokes, now being subjected to radial tyre grip/greater
lateral loading (better handling?)/flexible side-walls - all being held
together by the compatible size/rim profile of a 5"JJ Rim.

Now this is not “black and white”!
It’s not a case that a 185" x 16" radial is SAFE, and anything more is
UNSAFE, but mare a case of “fifty-shades-of-grey(gray)”

If you care to look at the TYRE AND RIM ASSOCIATION standards, you will find
that a 185x16" tyre is the preferred/recommended tyre for a 5"JJx16" rim.
An increment either side (175 or 195) is allowable.

A 215mm tyre is THREE increments wider - and is NOT RECOMMENDED.

Also note we are talking about ‘standard-profile’ tyres in all of the above
which is 78% aspect ratio (practically some tyres are made with 80%
profile.)
Where a tyre is of ‘standard profile’ this is not legally required to be
marked on tyre size - eg a 185R x 16" is a standard 78% profile tyre.
Where a tyre is “low-profile”, such as 70% (first low profile tyres) as
introduced by Jaguar in 1968 on the XJ6, then legally this must be shown in
the size - thus 185/70R x 16"
(My Daimler Super V8 runs 235/50R x 17" tyres - but has 8" wide alloy-wheels
designed for the resultant side-ways loads etc)

But every increment lower profile Standard > 70%, 70% > 65% etc has an
impact ‘roughly’ equivalent on tyre/wheel match as does every increment
wider.
So a 215R x 16" tyre is approximately as bad as a 185/60R x 16" tyre re
incompatability with a 5"JJ x 16" XK wheel rim.
(So a 215/70R is FOUR increments worse.)

Now all of this is safety-standards meant to apply to all cars, all tyres,
all wheels, under all conditions.
If you are going to park your car in a museum and never drive it, all you
need to worry about is having air in tyres to keep wheels off the ground.
If you are going to cruise along your freeways at 60 km/h and never go
around any corners then again just keep air in the tyre.

But if you are going on a race-track trying for FTD, hopefully you will have
severely modified suspension, wheels and tyres, to cope safely with the
loads you will need to exert to get that FTD.

So horses for courses.

But if you really think you are getting ‘better handling’ with 215 tyres in
lieu of 185 tyres - then you by definition you are pushing tyres to their
lateral adhesion limits, so heaven help you when a tyre pops of the rim or
more likely you break spokes in the wheels.

In Australia there are laws that say you cannot modify tyre
size/width/aspect-ratio beyond the wheel/rim size design - in modern cars
our regulations require a TYRE PLACARD to be affixed in a visible location,
that dictates what tyre sizes are legally allowable on that car, but clearly
these were not required in 1950s/60s.

Regardless a 215R x 16" tyre is ILLEGAL in Australia on a 5"JJ x 16" XK
wire-wheel (can’t say for sure in USA but will be same case in UK/Europe).
Chances of being caught are negligible, but if in an accident, enough for
insurance company to refuse any claims.

So my bottom line is.
What are you trying to achieve?

Stay with a 175 or 185R x 16" tyre for all normal road use, including fast
and spirited driving.
If you just want the “good looks” of a wide tyre, I have no comment.
If you want to go racing - then prepare for more mods than just tyre width.

Roger Payne
XK140MC OTS; 4.2E OTS; DaimlerSV8
Canberra, Australia

.-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
Dr. Barry Simmons
Sent: 7 September, 2015 02:03
To: xk@jag-lovers.org
Subject: Re: [xk] Modern tires on XK120

Hello Lindi,
I also have a 140 (DHC) with wire wheels. Do you know if the 215 tires will
fit my(65 spoke?) wire wheels? Also did you use 215 on all four wheels? What
brand tire did you buy? Thank you in advance for your answers.
Barry Simmons
S818044
On Sep 6, 2015, at 10:26 AM, lindi wrote:

In reply to a message from Per Lemser sent Sun 6 Sep 2015:

Hi Per,

I was in your situation some time ago concerning our XK140 FHC. I
decided to buy 215 tires (the widest what is possible with the disc
wheels for the 140). I found the information about that in this forum.
Having installed them and registered (for shure) I am very happy with
this choice. But I have removed the spats already before and did not
try to fit them afterwards, because I like the car better without.
Handling is much better than with the 185, I used before.

Best regards
Lindi

lindi
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]-- --Support
Jag-lovers - Donate at http://www.jag-lovers.org/ donate04.php –

13

Yes, interesting that COKER seem to not comply with the UK/European
convention of quoting Radial Tyre widths in mm, but still 600R 16.
Still they do include the R = Radial designation and the 600 is of course
original 6 inch width. Maybe this inch/mm convention is just voluntary in
USA and not mandatory.

Came across this ‘anomoly’ 18 months ago when Judging at a concours - our
rules say no radial tyres allowed on 1940s/60s Jaguars (its more detailed
than that), and entrant of an SS DHC had Coker Radials fitted, but claimed
the non-metric size meant they were OK. Good try, but he was still debited
not just for the ‘R’, but because they were in fact Radial tyres.

But still - I totally agree whether a Coker 600R 16 or a Michelin 185R 16 (

  • I hope the 105 70 R16 is a typo) are two excellent and legal choices. (I
    used/use 185R 16 Firestone, albeit when car is back on road will be time to
    renew on an age basis!)

Roger Payne
XK140MC OTS; 4.2E OTS; DaimlerSV8
Canberra, Australia

.-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
Velocette
Sent: 7 September, 2015 02:21
To: xk@jag-lovers.org
Subject: Re: [xk] Modern tires on XK120

In reply to a message from Per Lemser sent Sun 6 Sep 2015:

Per;
I have a 120 DHC fitted with Coker 600 R 16 Radial tires.
They fit within the wheel well and look just like the original bias ply
tires, Their handling is very good, ride is good, wet weather grip is FAR
better than ANY bias ply tire. I could not be happier with them. I have
had many other brands and types of tire on the car from Michelin 185R 16,
(very good and VERY expensive does not look original) Continental 105 70
R16, (poor handling, poor grip, cannot be used with inner tubes. I fount
that out the hard way).
My car is regularly driven and driven vigorously so good tires are important
to me.

Roger, '54 120 (SE) DHC, BRG, S678300
Tamarac, South Fla., United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]-- --Support
Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

14

In reply to a message from Roger Payne sent Sun 6 Sep 2015:

Roger, thank you for the excellent primer on tires for the XKs. I
have 215s on both my 140s and think they both look and drive
great. However, I am not involved in any dynamic high speed
driving and the cars are lucky to get a Sunday morning cruise.
Yet, the next time I change tires I’ll be heeding your advice and
down size. As my highly experienced pilot father used to say,
‘‘better safe than sorry.’’ Thanks again for sharing your
expertise. Don–
Etch, Etype S1 coupes, XK140 roadsters, Ariel Atom, 911
Spring Hill. fl, United States
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15

In reply to a message from Roger Payne sent Sun 6 Sep 2015:

Roger,
You mentioned the JJ rim, but my original Dunlop rims are 5K
x 16 which do not have the anti-roll-off bead feature.
Can you clarify, is that the difference?–
The original message included these comments:

Now our XK wheels were 5’’ rim width (16’’ diameter) and had a ‘JJ’
rim-profile.

–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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16

That’s what you get going by memory - to many years involved with these
standards/regulations - refer to the BOOK!

You are 100% correct, as made XK wire wheels were 5K (5" wide, K profile).

As far as the actual “Bead Seat” (as in the Safety part of the tyre
interface) a K rim is the same as a J rim and JK rim that later evolved into
a JJ rim, and I seem to recall 1960s E-type wheels are already marked JJ.

It’s all quite complex going into several lengths, radii and angles of the
wheel-rim profile to +/- tolerances, but the difference in a K rim to a
later JJ rim has nothing to do (I think) with the bead-seat area, and I
vaguely recall it’s in the valve-stem area - not quickly apparent in the 100
page1982 STANDARDS MANUAL I have in hand

So with this 1982 Manual open - thought I would CHECK my other memory:-

Bugger - doesn’t list 16" tyres (not common/popular in 1982 - need to look
at earlier edition), but for 15" tyres (similar, but there can be variations
from 16" - have to check to be sure).

A 185R - 15" tyre (of ‘80%’ profile) has a design Rim Width of 5.00", but is
‘Approved’ to be fitted to 5, 5-1/2, 6 or 6-1/2" rims.

A 215R - 15" tyre has a 6.00" design Rim Width, but is ‘Approved’ to be
fitted to 5-1/2, 6, 6-1/2 or 7" rims.

Thus my earlier comment - a 215R - 15" tyre is NOT LEGAL on a 5" rim, thus a
215R-16" (without checking as adverse effect increases with larger wheel
diameter) is most definitely not LEGAL on a 5" rim.

My earlier comment that a width increment either way is acceptable,
A 195R - 15" tyre has a design RIM Width of 5-1/2", but rims of 5", 5-1/2",
6", 6-1/2", 7" are acceptable.

Roger Payne
Email: @Roger_Payne2-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
Rob Reilly
Sent: 7 September, 2015 12:59
To: xk@jag-lovers.org
Subject: RE: [xk] Modern tires on XK120

In reply to a message from Roger Payne sent Sun 6 Sep 2015:

Roger,
You mentioned the JJ rim, but my original Dunlop rims are 5K x 16 which do
not have the anti-roll-off bead feature.
Can you clarify, is that the difference?

The original message included these comments:

Now our XK wheels were 5’’ rim width (16’’ diameter) and had a ‘JJ’
rim-profile.

–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0 --Posted using
Jag-lovers JagFORUM [forums.jag-lovers.org]-- --Support Jag-lovers - Donate
at http://www.jag-lovers.org/donate04.php –

17

I have been running my 150 FHC with chrome wire wheels, tubes, and 205’s. Into my second set now. Now issues other than a bad set of Chinese tubes. I always use the heavier duty “racing” tubes. Hi speed road driving with no issues.
Ron
XK 150 3.8 L FHC
Five speed
Roll bar
Headers

ron raderSent from my iPhone

On Sep 6, 2015, at 5:45 PM, Roger Payne rogerpayne@bigblue.net.au wrote:

This whole issue of TYRES (TIRES) is something you need to really assess
what you are trying to do.

Tyres and Wheels and their compatible/matching sizes is one of the first
things that attracted the interest of safety regulations in particular with
how the tyre fits and stays fitted to the wheel, and this ended up with some
very detailed rules/regulations regarding the rim profile and then the
construction of the tyre to properly match and lock into the rim profile.
It is no accident that it is so difficult to get a flat tyre off a rim, as
the bead of the tyre has deliberately locked into the rim of the wheel as it
was designed to.

Thus at speed and high cornering loads the tyre stays on the wheel, and
doesn’t peel off sideways as did the early non-safety rim tyres/wheels.

Where I am going on all of this is with grip of tyres, flexing of wheel and
rims, flexing of tyre side-walls, you really should NOT deviate unknowingly
from the design standards that applied to both DUNLOP - who made the wheels,
and to all the reputable ‘first-world’ country tyre manufacturers (don’t get
me started about Chinese made tyres!).

In the case of XKs, early wire wheels were 54 spoke, but from early XK150
they were changed to 60 spoke - not for appearance/good looks but because
once a 54 spoke painted wire-wheel was strong enough for side loading, but
as we all (most of us at least) know Chrome Wire Wheels are not as strong,
with the American interest in ordering optional Chrome Wire Wheels (rarely
ordered in other markets) Dunlop thought necessary to increase strength of
their wire wheels to having 60 spoke (regardless of whether Chrome or
painted).

Now radial tyres aggravate that problem compared to the then used Cross
(Bias) Ply tyres, which have far better grip and far more flexible
side-walls, thus a much greater propensity to dislodge from the wheel rim in
hard/extreme cornering.

Now our XK wheels were 5" rim width (16" diameter) and had a ‘JJ’
rim-profile.
The design tyre width for a 5"JJ x 16" rim is a 6.00" x 16" tyre, and up to
allowable 6.50" width.
Radial tyres (by agreement between UK and European tyre manufacturers) to
easily differentiate their radial/cross-ply construction quote radial tyre
widths in metric, so a 6.00" cross-ply width equates to a 155mm or 155R x
16" tyre, however the functional radial equivalent was agreed to be
perfectly acceptable on a 60 spoke (or disc) wheel to use a 175R x 16" tyre,
albeit apart from Michelin, not a common size, so close enough and generally
acceptable was to fit a 185R x 16" tyre.

So you see we already have had a lot of creep - 6.00" = 155mm, allow up to
175mm but then allow up to 185mm.
Cross ply tyre grip/lateral loading/firm side-walls OK with 54 painted
spokes or 60 chrome spokes, now being subjected to radial tyre grip/greater
lateral loading (better handling?)/flexible side-walls - all being held
together by the compatible size/rim profile of a 5"JJ Rim.

Now this is not “black and white”!
It’s not a case that a 185" x 16" radial is SAFE, and anything more is
UNSAFE, but mare a case of “fifty-shades-of-grey(gray)”

If you care to look at the TYRE AND RIM ASSOCIATION standards, you will find
that a 185x16" tyre is the preferred/recommended tyre for a 5"JJx16" rim.
An increment either side (175 or 195) is allowable.

A 215mm tyre is THREE increments wider - and is NOT RECOMMENDED.

Also note we are talking about ‘standard-profile’ tyres in all of the above
which is 78% aspect ratio (practically some tyres are made with 80%
profile.)
Where a tyre is of ‘standard profile’ this is not legally required to be
marked on tyre size - eg a 185R x 16" is a standard 78% profile tyre.
Where a tyre is “low-profile”, such as 70% (first low profile tyres) as
introduced by Jaguar in 1968 on the XJ6, then legally this must be shown in
the size - thus 185/70R x 16"
(My Daimler Super V8 runs 235/50R x 17" tyres - but has 8" wide alloy-wheels
designed for the resultant side-ways loads etc)

But every increment lower profile Standard > 70%, 70% > 65% etc has an
impact ‘roughly’ equivalent on tyre/wheel match as does every increment
wider.
So a 215R x 16" tyre is approximately as bad as a 185/60R x 16" tyre re
incompatability with a 5"JJ x 16" XK wheel rim.
(So a 215/70R is FOUR increments worse.)

Now all of this is safety-standards meant to apply to all cars, all tyres,
all wheels, under all conditions.
If you are going to park your car in a museum and never drive it, all you
need to worry about is having air in tyres to keep wheels off the ground.
If you are going to cruise along your freeways at 60 km/h and never go
around any corners then again just keep air in the tyre.

But if you are going on a race-track trying for FTD, hopefully you will have
severely modified suspension, wheels and tyres, to cope safely with the
loads you will need to exert to get that FTD.

So horses for courses.

But if you really think you are getting ‘better handling’ with 215 tyres in
lieu of 185 tyres - then you by definition you are pushing tyres to their
lateral adhesion limits, so heaven help you when a tyre pops of the rim or
more likely you break spokes in the wheels.

In Australia there are laws that say you cannot modify tyre
size/width/aspect-ratio beyond the wheel/rim size design - in modern cars
our regulations require a TYRE PLACARD to be affixed in a visible location,
that dictates what tyre sizes are legally allowable on that car, but clearly
these were not required in 1950s/60s.

Regardless a 215R x 16" tyre is ILLEGAL in Australia on a 5"JJ x 16" XK
wire-wheel (can’t say for sure in USA but will be same case in UK/Europe).
Chances of being caught are negligible, but if in an accident, enough for
insurance company to refuse any claims.

So my bottom line is.
What are you trying to achieve?

Stay with a 175 or 185R x 16" tyre for all normal road use, including fast
and spirited driving.
If you just want the “good looks” of a wide tyre, I have no comment.
If you want to go racing - then prepare for more mods than just tyre width.

Roger Payne
XK140MC OTS; 4.2E OTS; DaimlerSV8
Canberra, Australia

.
-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
Dr. Barry Simmons
Sent: 7 September, 2015 02:03
To: xk@jag-lovers.org
Subject: Re: [xk] Modern tires on XK120

Hello Lindi,
I also have a 140 (DHC) with wire wheels. Do you know if the 215 tires will
fit my(65 spoke?) wire wheels? Also did you use 215 on all four wheels? What
brand tire did you buy? Thank you in advance for your answers.
Barry Simmons
S818044

On Sep 6, 2015, at 10:26 AM, lindi wrote:

In reply to a message from Per Lemser sent Sun 6 Sep 2015:

Hi Per,

I was in your situation some time ago concerning our XK140 FHC. I
decided to buy 215 tires (the widest what is possible with the disc
wheels for the 140). I found the information about that in this forum.
Having installed them and registered (for shure) I am very happy with
this choice. But I have removed the spats already before and did not
try to fit them afterwards, because I like the car better without.
Handling is much better than with the 185, I used before.

Best regards
Lindi

lindi
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18

In reply to a message from F Ronald Rader sent Sun 6 Sep 2015:

Hello again,

this is a very interesting discussion. Just to mention, the
140 has 5,5 rims. Therefore the german T�V told me the max
size is 215. So done before bying and so registered.

Best regards
Lindi–
lindi
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

19

Lindi,

Presumably your XK140 has disc-wheels if they have 5-1/2" rims? 215 tyres
is indeed maximum allowable on a 5-1/2" disc-wheel, albeit not preferred
Wire-spoke wheels have 5" rims.

On introduction in 1949 XK120 (and 1950 Mark VII) were fitted with part
number C.3105 5K x 16 (5") disc-wheels, but from late 1952 (661042/ 673298
OTS and 669003/ 680477 FHC) they were increased in width to 5-1/2" (part
number C.6749 5-1/2K x 16).

Service Bulletins detailed how to differentiate them, with warnings not to
mix them, as the wider-wheels (as a pair) increased an XK120’s track by
1/2", from (front) 4’ 3" with 5" rims to 4’ 3-1/2" with 5-1/2" rims and
(rear) from 4’ 2" to 4’ 2-1/2".

Wire Wheels on introduction were 54 spoke and 5K x 16 (5") and remained that
way, even when upgraded to 60 spoke in 1958.

XK140 and XK150 always had 5-1/2" disc-wheels or 5" wire-wheels, but still
retained the same recommended tyre size of 6.00" x 16" (in a cross-ply
tyre).

Roger

Roger Payne
XK140MC OTS; 4.2E OTS; DaimlerSV8
Canberra, Australia

.-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
lindi
Sent: 8 September, 2015 04:46
To: xk@jag-lovers.org
Subject: Re: [xk] Modern tires on XK120

In reply to a message from F Ronald Rader sent Sun 6 Sep 2015:

Hello again,

this is a very interesting discussion. Just to mention, the
140 has 5,5 rims. Therefore the german TÜV told me the max size is 215. So
done before bying and so registered.

Best regards
Lindi

lindi
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]-- --Support
Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

20

this is a very interesting discussion. Just to mention, the
140 has 5,5 rims. Therefore the german TÜV told me the max
size is 215. So done before bying and so registered.

I found the 205 plenty large. ron>