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MG Midget and Sprite Technical - Wheel and Tyre size - RWA

Hi all,

I've been lurking here for a while, but I've finally plucked up the courage to speak :)

I have just recently finished (after N years, where N is a lot) my '72 RWA midget, and it finally passed its CT (equivalent of MoT test here in France) a few weeks ago. On my list of things I wanted to change, but didn't want to invest in until it was road legal, was the wheels.

I'm currently thinking of 4-spoke revolutions, but have heard conflicting advice about whether 5.5" rims would fit it without fouling. It has been lowered front and read (with lowered springs, not with blocks, if that matters) and has -ve camber trunnions on the front and a panhard rod on the rear.

I've read Daniel's book (many times now :) ) but from what I've read elsewhere, I'm uncertain whether :

- the 5.5" will foul
- the 5.5" would make the handling too heavy

and also what size tyres - the PO had it on 165/70 on the original rostyles, but I'm toying with 175/60 (though the bottom of the exhaust manifold is already close to the road, so I'm worried that even a slightly smaller overall diameter would take it even closer).

The choice of tyres is much more "performance" oriented in 175/60, but again I'm worried that too sticky would take the fun out. It's mainly a road car, but will be used for some classic trackdays this year.

Any advice, especially if there is anyone using 5.5" on a RWA car, would be greatfully appreciated.
OrangeSpyderMan

I had 175's on the back of my 72 rwa when last driven (n years ago) and i could get it to break traction -- loved those tyres!! toyo brand, when toyo were a 'cheap' foreign import tyre.

ok, ok i was running a 1600 cc ford engine in it at the time, but the tyres were fantastic (on standard rostyles)
Mick struggling with the wiring

Sorry can't fully answer your question but hopefully give you some info, perhaps you already know most or all of this

Personally I don't like too othersized wheels and tyres on a road car, for my personal style of driving on roads only and taste they spoil the lovely feel of steering

I think you will take some of the fun out of road driving and know from experience that a low hanging manifold is a misery on the road

It depends how many days or hours your car will be on roads compared to tracks, what great fun on a dry track might be a misery driving back on wet roads

Perhaps buy a diffent set of wheels and tyres for the track

If you're using one vehicle for two different things then there'll be a lot of compromise

Putting on much wider wheels and tyres and doing track days means a lot more strain on other component so everything needs to be in good condition and will wear more

These links may be tell you stuff you already know but there's lots of info on them about tyres

http://www.kouki.co.uk/utilities/visual-tyre-size-calculator

http://www.carbibles.com/tyre_bible.html

http://www.carbibles.com/tyre_bible_pg4.html
Nigel Atkins

Hi,

Thanks for this feedback - I agree, one of the reasons I'd like some feedback is exactly because I'm concerned what the steering would be like afterwards. The rest of the suspension components are in very good condition, after a pretty comprehensive strip-down and rebuild, replacing anything that looke worn.

It won't get driven much on (very) wet roads, and I'd be willing to change the tyres during the winter, but I'd really like to stick to one set of wheels.

Any other recommendations for tyre/wheel size/make/type are also welcome.

Thanks again,
OrangeSpyderMan

I use 165/70 on 5x13 'minilites' for road; and 175/60 on 5.5x13 Cobra Slots with 032Rs. The wider wheels and tyres fit fine, but with extra offset 'may' stick out slightly from the front arch. Car has a tougher look with the wider wheels... but they (with the tyres) give the car a very different feel; esp when hot the 032s give an amazing amount of grip and slide in the most controllable manner. Downside is heavier steering and less supple ride ('less supple'!! - it's all relative).

A
Anthony Cutler

I've had 155/80s and 175/70s both on 5 inch rims. I find the 175s to be much better at steering feel and grip, with no great increase in turning effort.

I've got Avon CR on the front and had no aquaplaning in the last amount of rain (seems ages ago...), very impressed with them. cheap as well.

My 175's catch on full bump on the front wing edges. only very slightly under extreme provocation. Nothing catches at the back.

I'm running telescopics on the front so I don't have a bottoming out problem, even so I wouldn't want anything that was too small in diameter...

slightly higher top speed with the 175/70s than 60s as well.
Rob Armstrong

I have a square wheel arch Midget - so what is OK for me should be fine for a RWA.

I have vintage Compomotive wheels with 5.5 rims and 165/70x13 Toyo tyres. I had the same size tyres on the original Rostyles but I felt they flexed too much and just did not feel 'planted' when cornering. The same size tyre on 5.5 rims is much better and provides great road holding. They look great too!

I did have to fit a panhard rod to stop the tyres fouling the wheelarch when cornering energetically (but you already have one of those). Personally I don't think you need a much wider tyre for grip and you do need to worry about aquaplaning in the wet if you go too wide.

Chris
Chris H (1970 Midget 1275)

just for the record I've got

5" minlite 13" cheap copies

155/70/13 Yokohama A-Drive all round, very pleased with them

next time I might get 165/70 just to give a few more mm of ground clearance for the manifold

Nigel Atkins

Ive got 175/70's on (centre locking) minilites with -ve camber trunnions. The trunnions just tuck the wheels in enough to clear the front arches (they didnt with standard camber). At the rear ive eased the square arches out a bit(you wouldnt notice). The car is lowererd, wet leaves never mind speed bumps cause me a problem. Ive got no rub though.

Im going to go for 175 / 60 Toyo road legal track day tyres soon
S G Macfarlane

I wouldn't worry about steering going heavy with larger tyres
I used to run 205/60's on 8" rims, a quickrack (1 1/2turns l-l) with a small steering wheel -- You could punt it round the sharpest of turns one handed without a problem
Willy
William Revit

This thread was discussed between 13/05/2011 and 14/05/2011

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