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MG Midget and Sprite Technical - MK 1 Sprite ride height

What height should I expect from wheel centre to the edge of the rear wheel arch lip on my Frog? I have just replaced the oversized 14" wheels (155/80/R14 tyres) with my nice original 13" MK 1 wheels fitted with nice new Firestone 145/70/R13 tyres. Naturally the car now sits a litle lower to the ground because of the reduced radius. But for the same reason there is now an increase in the empty space between tyre and the top of the wheel arch. I presume that the wheel centre to wheel arch top hasn't actually changed, it just looks more!

It is fairly likely that I have asked this before, but I don't remember and/or have lost the answer.
GuyW

Guy, this is a good question. Probably depends a bit on the type & condition of your rear springs and whether you have any spacers installed. All I can say is that pretty much every frog that I see looks to me as though it either sits too low at the rear when on original 15 leaf springs or too high when it sits on "heavy duty" 10 leafers unless it's had spacers fitted between the spring box and spring.

For what it's worth, and bear in mind that my car has been extensively restored around the rear suspension mounts, has 155/80/13 tyres, 10 leaf springs and spacers, I see 15" between the wheel centre and wheel arch top. I still think that mine looks a little high at the back.
Simon Wood

Here's how mine looks....


Simon Wood

Thanks Simon. Nice looking car. I think having the under wheel arches in black certainly helps the look of it. Mine are currently in body colour, blue.

My tyres are 145/80/13, not 145/70/13 as I had put.

The height on mine is 15" one side and 1 5.5" on the other. I am not concerned about that difference as it's not been on the road yet, nothing has settled down and the heavy bits (engine, gearbox,fuel and me!) aren't in it yet. Just wanting to get a feel for what range it should be in.

Any other offerings?
GuyW

My wheel arches are body colour too but probably a bit dirty. I'm not a fan of plastering underseal-type substances on the unserside of my cars. When simply painted you can see any corrosion issues before they get a hold and do something about them. But that's a whole different topic....
Simon Wood

Must just be a shadow effect then, they look distinctly black in that photo!
I said "nice car". It's actually an extremely NICE car!

I agree with you about black underseal. I don't like the stuff at all, at least not the thick gloopy stuff. This car is done in stone chip and body colour on the whole of the underside and I am hoping to keep it that way.
GuyW

I doubt whether you'll get a factory spec. for that, Guy. I think they're right when they look right: that is, the wheel and tyre fill the arch with an even gap all round.
I agree with Simon, but it's only a TINY bit high. And probably perfect when he's driving it.

After the refurbished springs and rear axle went back in, my gap between Firestone and arch has gone from 5" to 3" in the last few months, and I haven't really driven her yet. So not qualified to offer a dimension.
Nick and Cherry Scoop

If mine is much the same as Simon's that's good enough for now as it will almost certainly change as time goes by. But a range of responses for cars in regular use would be interesting.
GuyW

Looking at my factory workshop manual it simply states that the minimum ground clearance should be 5". Vague to say the least. Should the lower edges of the sills be horizontal when the car is standing on level ground? Mine seem to be and the lower edge of the sill flange measures 7" above ground level.

This is further complicated by the fact that I have 1/2" spacers between the wishbones and front spring pans. I replaced the front springs too but couldn't get the correct length at the time (they were shorter on early cars than 1275's and the like)
Simon Wood

5" ground clearance is also quoted for later cars and still without clarification. Car unloaded at kerbside with half a tank of petrol(?).

I would have thought it meant 5" from the lowest part of the car but where is that, bottom of rear axle plug, exhaust clamp, hanging handbrake cable, sump? I've never measured but none of these appear to be 5" on my 1973 midget.

A road test report for a USA 1500 shows 3.2" ground clearance which sounds more realistic so earlier cars could well be less, certainly feels less over the traffic humps.

Nigel Atkins

Did you have existing springs that you dismantled and refurbished, Guy? If like mine, they will take time to settle.
I bought NOS (so called) for my MkII, and he always sat too low, I thought.
Nick and Cherry Scoop

Yes Nick, these are 'refurbished' original 15 leaf springs, in that I dismantled them, degreased, repainted and reassembled. One was still attached to the car and from the look of things I don't think it had been removed before. The car has been off the road since 1984. The other had been dismantled, degreased and partly reassembled but had fresh surface rusting that I cleaned off before repainting.

For now I have assembled without wedges but may add some later if necessary. I want to see how it settles down first.
GuyW

In the absence of any factual data, your only recourse is to look at period photos - with road tests being a better indicator than BMC publicity photos, and try to mimic the ride height as it appeared back in 1958.

It will always be subjective, but your starting point will be having the rear running higher than the front, to give a slightly nose down attitude.


f pollock

Fergus,
It's not for me a question of originality. In the absence of any other frogeye to compare it with, I was just needing a ball-park idea of roughly what would look right on a finished car. As much as anything as a check that my bodywork fabrication is OK and that I have assembled things right so far. Proper adjustment, if needed, will be done later after the engine and gearbox are in. 15" or thereabouts is good enough for now.
GuyW

This thread was discussed between 06/08/2018 and 07/08/2018

MG Midget and Sprite Technical index

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