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Tyre Sizes - Spitfire MkIV 1974


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Hi All

 

I've had 185/60/14 tyres fitted to Minilite alloys for a number of years now and experienced some scrubbing on the edges of the front tyres. I know this size is very close (about 0.2cm) to the rolling radius of the 155/80/13 tyres fitted to the original steel wheels.

 

Question is if I reduced the tyre size to 175/60/14 (to hopefully cure the scrubbing) would this have a detrimental effect on the car's handling? I know the speedometer reading would be affected by about 2% and the rolling radius looks to reduce by approx. 4cm.

 

I've noticed that the 175/70/13 wheel/tyre combination seems to be the optimal choice however I don't really want to change the wheels out as well.

 

I used this link to calculate the difference if that helps at all

 

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

 

Any thoughts appreciated

 

Many thanks

Rick

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Thanks Clive

 

The 65 profile increases the rolling radius slightly from standard by 1.5cm  - but overall the wheel/tyre diameter only goes by 0.5cm so might well be a better option. I wonder if the slight decrease in width and increase in height using the 65 profile would stop the scrubbing.

 

Cheers

Rick

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Have you checked the camber and toe settings? And if so, presumably (hopefully!) with the seats loaded up correctly. Most places ignore this.

 

Checks easy enough to do at home with 2 bricks, 2 bits of straight wood/metal and a tape measure. Extra pair of hands required. Oh, spirit level for camber...

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Agree with clive this will be toe in errors,

 

camber takes for ever to wear any tyre scrub, where as toe takes of material quickly, as you are dragging the tread sidesways if you have lost rubber on the outsides then toe has been set incorrectly and must be done static laden 150lbs on each seat + curb weight

 

pete

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  • 6 months later...

just picking this up again after a break to sort a cooling issue...

 

I will definitely be checking the camber/toe as suggested gents - but still niggling me that the wheel/tyres are just too wide for the car. 185/60/14 running on 6J (not sure on offset).

 

This might be a really daft and somewhat unrelated question - however on the existing 6j rims is it possible to run 175/65/14s on the front and leave 185/60/14 on the rear. Just changed out the track rods ends and the car is absolutely horrible to drive at the moment so needs some work to set up correctly  I want to change the tyres out before I begin as the front two are getting on a bit now and need refreshing (2 rears are newish and fine)

 

Found this site quite useful http://www.alloywheels.com/tyre_calculator

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No problem at all running different sizes front/rear. In this instance, 175/60 may indeed be a suitable solution. 

Since last posting I have got my spit on the road, fitted with MGF wheels and 185/55 15's. Also running low 480lb springs, and had a little rubbing.  10mm spring spacers fitted each side has cured the issue.

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what tyres did you go for Clive? I'm just in the process of pricing up some Continental Premium Contact 5, Goodyear Efficient Grip Contact and also Dunlop Street Response 2 - all on 175/65/14.

 

Not sure what I'm going for yet - however the Conti's on a friends supercharged M3 are highly sticky and he wholeheartedly recommends (even though at my much smaller size these will be 'passenger car' equivalents so no real direct comparison to wide sports tyres I guess).

 

I'll bear in mind the use of a spacer - hadn't really considered that.

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I have michelins on the spit. Mainly because a set with 200 miles on them fell in my lap for £50!! good tyres though.

However, I have just fitted a set of Goodyear efficientgrip tyres in 185/60 14 to or MX5, and they are brilliant. I know the other tyres you mention may be better, but the goodyears have great wet grip, I used to be able to spin the wheels in 2nd on a damp road, now struggle to do them in 1st once moving.

Mine were £140 a set delivered......bargain price methinks too.

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