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MG Midget and Sprite Technical - wire wheel width query

I acquired a new set of wire wheels recently - pic pof one below. Is this a standard width, and what sort of tyre size is suitable for it - 145/85/R13 is what I've got on my current wires, can I go up to 155/85 R13s on these?


Mothy

Tim you have to measure between the inner edges of the rim, where the tyre bead sits. Standard is 4" which although a bit dark I think yours are?
David Smith

I wasn't sure where to measure from - yes, it is 4" from the inner edges.

Am I best sticking to 145's then?
Mothy

155s are AFAIK within spec for 4" rims; I have run 165s on 4" wires on a classic trials car but it was a bit wobbly - not a problem as with a 4.8 diff it wouldn't go over 60 !
David Smith

David

Have you got any spare 4.8 diffs?
Dave O'Neill 2

Are you sure that your 145's are 85 and not 80?
155/70's might be a good option, that's what I had on my standard frogeye steel wheels and I liked the feeling. Now I've got 5.5 wheels with 165/70 tyres
Gary Lazarus

You are right Gary, they are 80 not 85! I'm not fully focussed this evening. What is the effect of reducing the profile from 80 to 70?
Mothy

The profile is a percentage of the width of the tread - 80% or 70%

If you increase the width from 145 (mm) to 155 (mm) you are also increasing the rolling diameter and the gearing.

You need to work out the difference between 80% of 145mm and 70% of 155mm x2 + the diameter of the wheel rim.
Dave O'Neill 2

Mmmm, there are books with this stuff in...

I've run 175/70 on 4" wires but don't recommend it.

As the rolling diameter of the wheel/tyre reduces you go the same speed but for more revs.

I don't know why more people don't buy the 4.5" tubeless wire wheel from MWS (or the 5.5")
Daniel Thirteen-Twelve

because it does not fit square arches?
(or am i quoting your fine book incorectly)
Onno Könemann

It's as David Smith said though I'd use the world jelly rather than wobbly - it amounts to the same thing, especially when making progress through a sequence of bends.

It is also an extremely tight fit on square arches.
Daniel Thirteen-Twelve

thanks guys - will let you know what I end up with!
Mothy

There's a useful calculator here:
http://www.club80-90syncro.co.uk/Syncro_website/TechnicalPages/TRC%20calculator.htm
for comapring the rolling radius etc, etc of various profiles - does all of Dave's maths for you.

Hope it's helpful
Mark

EDIT:
Link doesn't work because of the spaces. Copy and paste it into your browser and it works fine...
MarkH1

Daniel -

I really don't think MWS do a 4.5" wire wheel for the Spridget, tubed or tubeless. Their website certainly doesn't list one and I believe it's been established that GT6 wires do not fit the Spridget spinner.

Dayton do a 4.5 wire in the US, but they are expensive ... and prohibitive over here, if you can get them.

Tim -

I have enjoyed 165/70s on a 4" wire wheel, but they were snow tyres and may have had a stiffer sidewall. 155/80s or 155s (technically 82 profile where they still exist) are a great tyre for 4" wires - 155/70s lower the gearing and look too small IMHO.

Lower profile tyres lower the CG, making the car feel more 'planted', but can make the ride more crashy. Profiles lower than 70 are not recommended by the tyre people for use with tubes (chafing?).

Tom
Tom Coulthard

Looks like you're right Tom. I thought someone else apart from Dayton did a 4.5" wire.

Certainly the exchange rate doesn't favour importing anything from the US at present.

The really rare wires are the 5" - once saw them on a racing Spridget (well known historical car.. you might know it).

Daniel Thirteen-Twelve

We have 4.5" wires on Anita's midget, we bought 9 of them on ebay some years ago, sold 4 to Shawn and we kept the other 5. Ironicaly, all 9 are now here in Australia.
Last year I found that the spokes were loose in two of the wheels and set out on a mission to find some replacements to no avail. I ended up getting them rebuilt by Tony Margell (The Spokesman) in Leeds at circa £95.00 per wheel.
There was someone offering some 5" Midget wire wheels here recently, but I failed to follow up the ad...!

Tim, 155-80/13 or 155-70/13 will be fine for Sabrina.

Mark.
M T Boldry

Ours are MG motorsport wheels - 1/2 inch wider and stronger spokes than stock. The factory had all race wheels powder coated black, after wrong wheels were inadvertedly fitted during a race. Ours were powder coated black. Anita's still are. Tyres are not as easily located here in 13 inch. I would love some road legal race tyres in 165/70.
Shawn

This thread was discussed between 11/04/2010 and 17/04/2010

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