Conference terri::cars_uk

You boy racer!!!

Steve

Here's a chart I've had for a number of years.  It should give you the info
you need.  It only covers 12" - 16" wheels so no data for Isettas or the
new cars with 17+ wheels, sorry.


 (12)  
             80      75      70      65      60      55      50

    145 21.1339 20.5630 19.9921 19.4213 18.8504 18.2795 17.7087
    155 21.7638 21.1535 20.5433 19.9331 19.3228 18.7126 18.1024
    165 22.3937 21.7441 21.0945 20.4449 19.7953 19.1457 18.4961
    175 23.0236 22.3346 21.6457 20.9567 20.2677 19.5787 18.8898
    185 23.6535 22.9252 22.1969 21.4685 20.7402 20.0118 19.2835
    195 24.2835 23.5157 22.7480 21.9803 21.2126 20.4449 19.6772
    205 24.9134 24.1063 23.2992 22.4921 21.6850 20.8780 20.0709
    215 25.5433 24.6969 23.8504 23.0039 22.1575 21.3110 20.4646
    225 26.1732 25.2874 24.4016 23.5157 22.6299 21.7441 20.8583
    235 26.8031 25.8780 24.9528 24.0276 23.1024 22.1772 21.2520
    245 27.4331 26.4685 25.5039 24.5394 23.5748 22.6102 21.6457
    255 28.0630 27.0591 26.0551 25.0512 24.0472 23.0433 22.0394
    265 28.6929 27.6496 26.6063 25.5630 24.5197 23.4764 22.4331


(13)
             80      75      70      65      60      55      50
    145 22.1339 21.5630 20.9921 20.4213 19.8504 19.2795 18.7087
    155 22.7638 22.1535 21.5433 20.9331 20.3228 19.7126 19.1024
    165 23.3937 22.7441 22.0945 21.4449 20.7953 20.1457 19.4961
    175 24.0236 23.3346 22.6457 21.9567 21.2677 20.5787 19.8898
    185 24.6535 23.9252 23.1969 22.4685 21.7402 21.0118 20.2835
    195 25.2835 24.5157 23.7480 22.9803 22.2126 21.4449 20.6772
    205 25.9134 25.1063 24.2992 23.4921 22.6850 21.8780 21.0709
    215 26.5433 25.6969 24.8504 24.0039 23.1575 22.3110 21.4646
    225 27.1732 26.2874 25.4016 24.5157 23.6299 22.7441 21.8583
    235 27.8031 26.8780 25.9528 25.0276 24.1024 23.1772 22.2520
    245 28.4331 27.4685 26.5039 25.5394 24.5748 23.6102 22.6457
    255 29.0630 28.0591 27.0551 26.0512 25.0472 24.0433 23.0394
    265 29.6929 28.6496 27.6063 26.5630 25.5197 24.4764 23.4331


(14)
             80      75      70      65      60      55      50
    145 23.1339 22.5630 21.9921 21.4213 20.8504 20.2795 19.7087
    155 23.7638 23.1535 22.5433 21.9331 21.3228 20.7126 20.1024
    165 24.3937 23.7441 23.0945 22.4449 21.7953 21.1457 20.4961
    175 25.0236 24.3346 23.6457 22.9567 22.2677 21.5787 20.8898
    185 25.6535 24.9252 24.1969 23.4685 22.7402 22.0118 21.2835
    195 26.2835 25.5157 24.7480 23.9803 23.2126 22.4449 21.6772
    205 26.9134 26.1063 25.2992 24.4921 23.6850 22.8780 22.0709
    215 27.5433 26.6969 25.8504 25.0039 24.1575 23.3110 22.4646
    225 28.1732 27.2874 26.4016 25.5157 24.6299 23.7441 22.8583
    235 28.8031 27.8780 26.9528 26.0276 25.1024 24.1772 23.2520
    245 29.4331 28.4685 27.5039 26.5394 25.5748 24.6102 23.6457
    255 30.0630 29.0591 28.0551 27.0512 26.0472 25.0433 24.0394
    265 30.6929 29.6496 28.6063 27.5630 26.5197 25.4764 24.4331


(15)
             80      75      70      65      60      55      50
    145 24.1339 23.5630 22.9921 22.4213 21.8504 21.2795 20.7087
    155 24.7638 24.1535 23.5433 22.9331 22.3228 21.7126 21.1024
    165 25.3937 24.7441 24.0945 23.4449 22.7953 22.1457 21.4961
    175 26.0236 25.3346 24.6457 23.9567 23.2677 22.5787 21.8898
    185 26.6535 25.9252 25.1969 24.4685 23.7402 23.0118 22.2835
    195 27.2835 26.5157 25.7480 24.9803 24.2126 23.4449 22.6772
    205 27.9134 27.1063 26.2992 25.4921 24.6850 23.8780 23.0709
    215 28.5433 27.6969 26.8504 26.0039 25.1575 24.3110 23.4646
    225 29.1732 28.2874 27.4016 26.5157 25.6299 24.7441 23.8583
    235 29.8031 28.8780 27.9528 27.0276 26.1024 25.1772 24.2520
    245 30.4331 29.4685 28.5039 27.5394 26.5748 25.6102 24.6457
    255 31.0630 30.0591 29.0551 28.0512 27.0472 26.0433 25.0394
    265 31.6929 30.6496 29.6063 28.5630 27.5197 26.4764 25.4331


(16)
             80      75      70      65      60      55      50
    145 25.1339 24.5630 23.9921 23.4213 22.8504 22.2795 21.7087
    155 25.7638 25.1535 24.5433 23.9331 23.3228 22.7126 22.1024
    165 26.3937 25.7441 25.0945 24.4449 23.7953 23.1457 22.4961
    175 27.0236 26.3346 25.6457 24.9567 24.2677 23.5787 22.8898
    185 27.6535 26.9252 26.1969 25.4685 24.7402 24.0118 23.2835
    195 28.2835 27.5157 26.7480 25.9803 25.2126 24.4449 23.6772
    205 28.9134 28.1063 27.2992 26.4921 25.6850 24.8780 24.0709
    215 29.5433 28.6969 27.8504 27.0039 26.1575 25.3110 24.4646
    225 30.1732 29.2874 28.4016 27.5157 26.6299 25.7441 24.8583
    235 30.8031 29.8780 28.9528 28.0276 27.1024 26.1772 25.2520
    245 31.4331 30.4685 29.5039 28.5394 27.5748 26.6102 25.6457
    255 32.0630 31.0591 30.0551 29.0512 28.0472 27.0433 26.0394
    265 32.6929 31.6496 30.6063 29.5630 28.5197 27.4764 26.4331

    So the numbers in the preceeding table are........?????
    
    Brian Pituley
    

    
    Recommended tyre pressures.
    
    JBG
    
    8-)

    Thanks a lot, that's just what I'm after, but as mentioned -1/-2, an
    indication of what the figures mean might be handy ;-)
    
    Thanks again,
    
    Daniel

The (number) is the wheel diameter - there are charts for 12, 13, 14, 15 and 16
inch wheels.

The numbers down the left side are the tread widths.
The numbers across the top are the aspect ratios.
Find your wheel diameter, then find the number in the chart that your tread
width and aspect ratio meet up with and that is the circumference of that tire
in inches.

Find another combination with a similar circumference in the next higher wheel
diameter chart to get your +1 tire size, etc.

Dan (.0) asked about comparing his stock 185/55x13 to a 185/50x14 and 195/50x14.

From the chart we see:

185/55x13 = 21.0118
185/50x14 = 21.2835
195/50x14 = 21.6772

Not a whole lot of change which means it will also not 'fill the wheel well' any
better than the stock tire size.

Dave

    I dont think the figures can be circumference. They must be diameter.
    
    Andrew

    Circumference sounds like what it *should* be but they do look like
    diameters to me.......the numbers are just too small to be
    circumferences.
    
    Brian
    

    
    Looks like diameter to me too :-
    
    185 x 0.55 = 101.75mm * 2 = 203.5 
    
    203.5/25.5 = 7.98" (roughly)
    
    13 + 7.98 = 20.98" which is pretty close to 21.0118 which the table
    gives for 185/55s on 13" wheels.
    
    Mark

    Re 2340.10:
    
    Almost perfect.
    
    Put in the real value for the number of mm in an inch and you get:
    
        203.5/25.4 = 8.011811023622
    
    John O'C

So the formula in its full glory is:-

    Full wheel diameter in inches = wheel rim diameter in inches  
                                  + ((2 * (tyre aspect ratio * tread width ))/2540)

Phil.

(to check)  13 + ((2*(55*185))/2540) = 21.01181
( and )     14 + ((2*(50*185))/2540) = 21.28346

2540 combines the millimetre to inches conversion (25.4 mm = 1 inch) and the 
fact the the aspect ratio is really aspect ratio/100

Looks like they are diameters, but either way, you can compare different tire
sizes to see which are compatible with your car.

Dave

	Having decided that the figures in the table cannot possibly be the
circumference, that then begs the question - is it the radius to the ground when
stationary, the radius to the top of the tyre when stationary, or is it the
Rolling Radius?

	Surely, the only things that matters if you want to know the numer of
turns per mile etc. is the Rolling Radius.

	So what do the figures represent please?

				Malcolm.

    re .14
    
    The figures can't be radius either. They must be diameter.
    
    how it's measured is a good question.
    
    Andrew

    
    if all the table is bbeing used for is to find 'nearest equivilents' in
    different wheel/type sizes, then it doesn't really matter does it ? as
    long as calculations were consistent, then just pick the closest for
    the whhel size you want....
    
    Graham

    Yes the table has served its purpose.
    
    So, the question stands (albeit now in the wrong topic ;-) )
    
    Are there any 185/50 14 or 195/50 14 tyres available?

    > Are there any 185/50 14 or 195/50 14 tyres available?
    
    Yes. Definitely the latter, as that's the size of tyre on my Rover 420
    GSi Tourer
    
    Clive

    I presume 195 section tyres will pop onto 6" wide rims? I know 185's
    will.
    
    I would prefer 185 tyres to 195's, but if they're not available then
    it'll just be a case of some small, subtle spacers going onto the hubs
    (in fact the standard metro alloys run pretty close to the handbrake
    mechanism anyway, so this would probablt be a good idea.... I know of
    someone who had part of his handbrake machanism ripped off by the
    wheel, but this was probably due to a shoddy build ... ;-) )
    
    Dan
    
    P.S. Oh we're on about a kit car, here, the GTM K3...... just so no law
    suits are brought against me by Rover ;-) !!

    ...If the goal is to fill the arches, then the table is fine.
       If the goal is to change/maintain the turns/mile, then the table is
       also fine.
    
       I found the guide particularly useful as it gives alternative tyre
       sizes for ones which are now obsolete.
    
    	Tony.
    
    

    Well, being a bit of a nutter, I fancy 15" rims now.
    
    Comparing table figures :
    
    185/55 13"	= 21.0118 (this is standard)
    185/50 14"	= 21.2835 (my former option)
    195/50 15"	= 22.6772 (new option, and I reckon a bit too big to get
    			  in the arches)
    195/45 15"	= 21.9095 (new option, better. I think this will go in)
    
    Does anyone make 195/45 15" tyres?!
    
    Cheers,
    Dan

    re .21
    
    Yup, I used to have such beasts on my 2.0i MG Maestro.
    
    Clive

    What make?
    
    Oh those 2.0i MG Maestro's.... quick little things!
    
    Cheers,
    Dan$phoned_GTM_and_reckon_195/45 15"'s_will_fit

    re .23
    
    Goodyears if I remember rightly. It was 3 years ago though. I can't
    interest you in a set of 7 spoke Rover alloys can I. Complete with
    tyres (185 55 15" I'm afraid). Only I fancy putting some wider tyres on
    the Rover, and I reckon 205 45 16" will do quite nicely.
    
    Clive

    
    Dan,
    
    Sounds like time to call Micheldever Tyre Services :^)
    
    Mark
    
    PS Clive, have you considered what wheels to get? BTW Rover went to the
    spindly 185s to improve handling on the 200/400s, so 205s _may_ not be
    a step in the right direction...
                                    

    Clive,
    
    sorry, different stud pattern between the 200/400's and the Rover Metro
    :-(.
    
    I'll phone up Micheldever now, I think... :-)

    re .25
    
    Mark, I was hoping that by adding wider rubber, I might be able to add
    a bit more weight to the steering. I had a 414Si as a courtesy car
    recently and the non-assisted steering felt miles better than mine at
    speed.
    
    Clive

    As well as Micheldever, I found Total Tyre and Exhaust in Binfield
    (near Bracknell) to be quite cheap. You can haggle a bit as well.
    
    Another one to try is Hurst Tyres (near Winnersh).
    
    Barry.

    Just talking to the guy at Thames Valley Tyres, he's never head of that
    size Clive.... are you sure you had 195/45 xR 15"'s???
    					    ^^
    
    He's phoning back...
    
    Cheers,
    Dan

    
    Clive,
    
    I've had the same ideas myself (or maybe just disconnect the PAS pump
    :^)).
    
    The good thing about Micheldever (in my experience) is they're cheap,
    knowledgable and helpful, a rare combination which gets my business.
    
    Mark
        

    Got the number for Micheldever handy, or a pointer to it? I forget
    whether I saw it in here or the Reading conference.
    
    Cheers,
    Dan

    Dan, they were definitely 45xR 15"'s and I'm pretty sure about the 195
    bit as well. They came with the car, and I never had a chance to
    replace them (car was written of by an articulated lorry in fog, 6
    weeks after I got it).
    
    Clive

    Ok, cheers. I'll keep looking.
    
    Micheldever might help - still waiting on TVT..

	Whilst Micheldever are a jolly good outfit, I have found their
	quality of balancing a bit off, and on more than one occasion 
	too.

	-John

    I've always found them rather polite and handy myself. I took me car to
    have it's tracking adjusted/checked. They looked over it, got all the
    equipment out and checked it - it didn't need adjusting.
    
    They just left it at that. When I asked how much, the reply was "Don't
    worry about it.".
    
    Cheers,
    Dan

    Any suggestions regarding where to look for new alloys. I'm possibly
    after a new set for my Rover 420 to take 205 VR45 tyres on 16" rims.
    
    Clive

    ELITE (advertise is most mags, Fast Car, Max Sadness, CCC etc).
    
    Cheers,
    Dan

    Does anyone know the widest wheel and tyre combination that i can put on
    a standard mk1 Ford Fiesta without cutting the wheel arches also does
    anyone know where i can get a cosworth type rear spoiler for this
    model.......
          ........Thanks Chris.....

    >>Does anyone know the widest wheel and tyre combination that i can put
    >>on a standard mk1 Ford Fiesta without cutting the wheel arches 
    
    185/60 HR13 tyres on 6x13 rims will go fine (easily).
    
    I imagine if *width* is your concern, with the proper offsets on the
    wheels, you might be able to squeez 205's in there, but you might have
    to restrict the steering so you don't rub the arches on full lock.
    205/50 and 205/60 13" tyres are available.
    
    Personally I'd stick with 185 width (or thereabouts) and go for wheel
    diameter - that's the way things are going these days.... forget width,
    go for wheel size!
    
    >>also does anyone know where i can get a cosworth type rear spoiler for
    >>this model.......
    
    Ahem. Yes, someone does these. Check out your average hot hatch mag
    (Cars & Car Conversions, Max Sa.. Power) but I think Ripspeed might be
    able to help you out here.
    
    Cheers,
    Dan

    Over the weekend I got the old tape measure out on a K3 with the
    standard alloys and 185/55HR13 tyres. The table mentioned earlier is
    really quite accurate!
    
    Anyway, came to the conclusion, 195/45VR15" on 7x15 will go in.
    
    Cheers,
    Dan

My landrover currently has 650 (6.50) x 16 wheels/tyres
If I change them to 750 (7.5) x 16 I have been told
my road speed will increase (for the same engine speed).
Is this true? and why?


Simon

    re .42
    
    The bigger tyres will be wider and will have a greater circumference,
    in order to keep the same profile (I.e. height/width ratio, where
    'height' is roughly the distance from the rim of the metal wheel to the
    tread). So each revolution of the wheel will take you further. This
    will also mean that your speedo and odometer will no longer be
    accurate.
    
    Andrew

How much would the difference be?

I assume then the millage will be more than the speedo reads.

Assuming that it wasn't setup for the bigger tyres in the
first place. Is it possible to correct or would I have to
replace the speedo.

Simon

    on vehicles where diffs, tyre sizes & gear ratios vary from model to
    model, the speedo/odometer cable is driven by a removable cog which is
    matched to the final drive ratio - so it should be possible to get the
    correct cog for the final drive ratio you finish up with. It's been
    discussed somewhere else in here in the past, I think someone even posted
    an address of a garage which could do this for you.
    
    Graham

>My landrover currently has 650 (6.50) x 16 wheels/tyres
>If I change them to 750 (7.5) x 16 I have been told
>my road speed will increase (for the same engine speed).
>Is this true? and why?

You will notice a change in road speed vs engine speed only if the 750x16
tires are taller (or shorter) than the 650x16.  Unfortunately that size 
labelling doesn't tell us the over height or aspect ratios of the two tires.  
You'd have to compare them side to side.

It is conceivable that they managed to increase the width by 1 inch and not 
increase the overall height, in which case you would have no change in speed 
vs rpm.

Dave

As far as I understand, the 16 is the rim size and the 6.50 , 7.50
is the distance from rim to outside of tyre, I think. I do know that
the 7.50 is taller the 6.50.

Simon

    re .47
    
    I understood that the 6.5 etc was the nominal width of the tyre, not
    the height. I think that both the height and width are changed by an
    increase, to preserve the same profile.
    
    Andrew

Now  I am confused.

Simon

IMHO, 6.5 refers to rim width, 16 refers to rim diameter. 
Tyres are made to fit standard rim sizes. However it is 
possible to put a tyre on a wider or narrower rim - 
generally not advisable.

Rupert

    I think the confusion here is caused by the different systems used for
    Radial and Crossply tyres - I believe what we're talking about here are
    Crossply tyres.
    
    With a radial, there is an aspect ratio which relates to the tread
    width (in milimetres). Therefore increasing the width of the tread from
    say a 185 to a 205 (2mm increase) also increases the depth of the sidewall
    (ie. the distance between the rim and the tarmac) and so increases the
    circumference.
    
    with a Crossply, the size - I think - relates to the tread width (in
    inches). However, I don't know if this alters the the aspect ratio at
    all, and if so by how much...
    
    Graham 

The 650x16 refers to a 16 in wheel and a 6.5" wide tire, not the wheel width.  
So the 750x16 is one inch wider, but may or may not be any taller.  I would 
generally expect it will be taller by some amount.

The Isetta has a stock size of 480x10 - 4.8" tread width and 10 inch wheel. 
(but I have 145x10 radials on it)
The 1926 Stude has 650x20, 6.5" wide tire and 20" wheel.
The 1924 Stude has 32x4, 32" overall height and 4" wide tire, no mention of 
wheel size, although it's around 23 or 24".  The next size up for the '24 is a 
33x4.5 tire, so when they increased the width, they also increased the height.

Dave