Bent Radius Arm?
Discussion
How easy is it to bend a radius arm?
We've just bought a '93 Mini Sprite. An excellent solid car but we've just noticed the right rear wheel has far too much +ve camber i.e. it's top is much further out than the bottom.
I guess someone has side swiped a curb. Is this likely to be radius arm damage or sub-frame or shell?
Your thoughts on the subject would be most welcome.
We've just bought a '93 Mini Sprite. An excellent solid car but we've just noticed the right rear wheel has far too much +ve camber i.e. it's top is much further out than the bottom.
I guess someone has side swiped a curb. Is this likely to be radius arm damage or sub-frame or shell?
Your thoughts on the subject would be most welcome.
Its not that easy to be honest.
If I look at mine from the back there is visible +ve camber as well and its rather disconcerting.
I think they leave the factory with 1 deg +ve camber but on mine it looks a lot more than that.
There are brackets you can get that allow you to adjust the camber but I suppose the only way you will know the arm is bent is to take it off and compare...
If I look at mine from the back there is visible +ve camber as well and its rather disconcerting.
I think they leave the factory with 1 deg +ve camber but on mine it looks a lot more than that.
There are brackets you can get that allow you to adjust the camber but I suppose the only way you will know the arm is bent is to take it off and compare...
They bend surprisingly easily. I have followed several minis that have obviously had a comming together with a solid kerb in their past and one of the rear wheels has about 10 degrees positive camber.
Many years ago a friend bought a mini and wondered why someone had fitted a 5mm wheel spacer to one side only. Took the spacer out to find the tyre touches the shock absorber. Removed radius arm and compared against a new (secondhand) one and it was visibly bent.
Many years ago a friend bought a mini and wondered why someone had fitted a 5mm wheel spacer to one side only. Took the spacer out to find the tyre touches the shock absorber. Removed radius arm and compared against a new (secondhand) one and it was visibly bent.
It might just be the sub-frame. Measure the camber on each side and let me know what the figures are.
To make it easy, do it like this:
Get a piece of plywood, about 3/8" thick and approximately 18" x 24". Have it cut so that the edges are absolutely at 90 degrees to each other.
Park the car on a smooth and level piece of tarmac or concrete.
Hold the plywood board against the tyre vertically and at the wheel centre.
Now measure from the edge of the board to the wheel rim at the lowest point and at the highest point.
Subtract the figure at the bottom from the figure at the top. If the answer is a negative, you have negative camber, a positive figure is positive camber.
Ideally you must have ABSOLUTELY no negative camber. The ideal figure is a zero to about 1/8" positive figure.
The actual figure will tell you if the arm is bent, or if it's just the sub-frame tolerances, which are bloody awful anyway. As an approximation, if you have more than about 3/16" negative it could be a bent arm. If the arm is bent, however, the rear track is probably out as well. In my experience it is normally the sub frame or radius arm bracket which bends (the arm will normally snap!).
My guess is that it's just manufacturing tolerances, so don't worry too much, they are easy to modify and adjust out. Measure it and let me know the figures. Read my earlier posting about suspension settings, as suggested, it might help.
Good luck with this,
Peter
To make it easy, do it like this:
Get a piece of plywood, about 3/8" thick and approximately 18" x 24". Have it cut so that the edges are absolutely at 90 degrees to each other.
Park the car on a smooth and level piece of tarmac or concrete.
Hold the plywood board against the tyre vertically and at the wheel centre.
Now measure from the edge of the board to the wheel rim at the lowest point and at the highest point.
Subtract the figure at the bottom from the figure at the top. If the answer is a negative, you have negative camber, a positive figure is positive camber.
Ideally you must have ABSOLUTELY no negative camber. The ideal figure is a zero to about 1/8" positive figure.
The actual figure will tell you if the arm is bent, or if it's just the sub-frame tolerances, which are bloody awful anyway. As an approximation, if you have more than about 3/16" negative it could be a bent arm. If the arm is bent, however, the rear track is probably out as well. In my experience it is normally the sub frame or radius arm bracket which bends (the arm will normally snap!).
My guess is that it's just manufacturing tolerances, so don't worry too much, they are easy to modify and adjust out. Measure it and let me know the figures. Read my earlier posting about suspension settings, as suggested, it might help.
Good luck with this,
Peter
Cheers for that.
I'm just in the process of making my own camber gauge in the style of the ones Minispares sell. I figured I should quantify the problem before proceeding. My guess is it's about +5 degrees.
There is some distortion to the subframe. The upper longitudinal part has a curve in it close to the body.
If it is the subframe I guess I can fix it with some camber adjustment brackets (I can do a frame change but I'd rather not).
If it's the arm will it be obvious? should the shafts at either end be in the same plane?
I'll go away and read your previous notes. I'll report back my measurements in a couple of days.
I'm just in the process of making my own camber gauge in the style of the ones Minispares sell. I figured I should quantify the problem before proceeding. My guess is it's about +5 degrees.
There is some distortion to the subframe. The upper longitudinal part has a curve in it close to the body.
If it is the subframe I guess I can fix it with some camber adjustment brackets (I can do a frame change but I'd rather not).
If it's the arm will it be obvious? should the shafts at either end be in the same plane?
I'll go away and read your previous notes. I'll report back my measurements in a couple of days.
5 Deg is quite a lot. If it's that much i would reckon the sub frame is bent and I would advise changing it.
Adjustable camber brackets could offer a temporary solution, but I would bet the rear track is out as well and that really is critical to the handling.
I rackon my piece of plywood is as accurate as Mini spares camber gauge, and a lot cheaper.
I would not think the arm is bent as they are very solid and although I've had one snap during a forest rally, I've never had one bend.
If re-setting, aim for zero to 0.5 deg neg camber on the back.
Adjustable camber brackets could offer a temporary solution, but I would bet the rear track is out as well and that really is critical to the handling.
I rackon my piece of plywood is as accurate as Mini spares camber gauge, and a lot cheaper.
I would not think the arm is bent as they are very solid and although I've had one snap during a forest rally, I've never had one bend.
If re-setting, aim for zero to 0.5 deg neg camber on the back.
Ok, I've measured it with one wheel packed up so the car is level) and it's about +1.5 to +2.0 degrees. The left hand side is more or less dead on zero. Put another way the bottom of the wheel is about 7-10 mm further in than the top.
The haynes manual gives the spec. as 0 to +2.5 degrees so it 's within spec.
It's obviously less than ideal but I would have thought it's perfectly safe to drive.
What I think I'm going to do is order so Minispares adjustable brackets but fit them at my leisure.
As ever I'd welcome comments / suggestions / critiscm. etc.
Cheers.
The haynes manual gives the spec. as 0 to +2.5 degrees so it 's within spec.
It's obviously less than ideal but I would have thought it's perfectly safe to drive.
What I think I'm going to do is order so Minispares adjustable brackets but fit them at my leisure.
As ever I'd welcome comments / suggestions / critiscm. etc.
Cheers.
What I would do it to take off the offending bracket and file the hole where the radius arm shaft is located so that it is oval, with the filing in an upwards direction. Keep on re-fitting and re-measuring until the camber is at zero. Then get a large 'penny' washer, fit it under the shaft retaining nut, re-check the camber with it all tightened up and mig-weld the washer in place. Use a washer about 2 mm thick.
It's cheap, accurate and easy to do.
Whilst doing this check that the track on the rear has a toe-in of about 3 mm to 5 mm. If it doesn't it's easy to fit either thin shims, or to grind a bit of the face of the brackets to get the corerct toe-in. If you do both the track on the back and set the camber to zero your Mini will always handle like a dream.
This is what we do on our rally cars when we afre not allowed non-homologated modifications like camber brackets. Once it's all set correctly you never need to change it anyway.
Your figures are typical for current sub-frame tolerances.
It's cheap, accurate and easy to do.
Whilst doing this check that the track on the rear has a toe-in of about 3 mm to 5 mm. If it doesn't it's easy to fit either thin shims, or to grind a bit of the face of the brackets to get the corerct toe-in. If you do both the track on the back and set the camber to zero your Mini will always handle like a dream.
This is what we do on our rally cars when we afre not allowed non-homologated modifications like camber brackets. Once it's all set correctly you never need to change it anyway.
Your figures are typical for current sub-frame tolerances.
Cheers for that Cooperman.
Good to know that it's within current tolerances. That's put my mind at rest.
I'm afraid to admit tha tI'm going to fit the fancy bracket. I don't have a welder that works at the moment and the car is my other half's daily driver and I just want to get it back on the road and get on with other things. Like your thinking on the budget approach though.
Good to know that it's within current tolerances. That's put my mind at rest.
I'm afraid to admit tha tI'm going to fit the fancy bracket. I don't have a welder that works at the moment and the car is my other half's daily driver and I just want to get it back on the road and get on with other things. Like your thinking on the budget approach though.
The brackets are really very good, especially the ones where you can adjust both camber and track. You can get it spot-on with these if you use a 4-way alignment machine to track it fromt and back.
I was just suggesting a budget option which works as well in practice or if you are constrained by some motorsport regulations, as I am.
I was just suggesting a budget option which works as well in practice or if you are constrained by some motorsport regulations, as I am.
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