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MG Midget and Sprite Technical - Mounting coil over shocks

Started a new thread for this question, Because it is slightly different.

Planned the rear coil conversion now (all I need is some money!) and I'm wondering if the I can use the rebound check strap mounting holes for the top mount of my shock a la Frontline?

I'll be using a coil over, so all the suspension loads will feed through this mount, not just the damper loads as in the Frontline kit.

Will it be strong enough if I weld some spreader plates to the chassis across the holes?

Andy
a borris

I tried it for a few days

not strong enough when un strengthened and even if plated I have serious doubts. Started cracking very soon.

I intend using s "U" section beam in the roof of the axle "space" bracing and mounting to that

however at present, strengthened, I am using the mounting for the mini shocks alone.

Not confident it could take all of the imposed stresses with coils too, that's a hell of a battering on the shell
Bill

"I intend using s "U" section beam in the roof of the axle "space" THEN bracing, THEN mounting to that"

missed a word or two out
Bill

I did, but I didn't do the job myself so I don't know how much reinforcement the chappie put in. It wasn't a road car though.

Max T

Wonder how Frontline do it then...on measuring I think it's a no go anyway. Think it's short of space for the upper coil spring retainer to fit.

Unless I buy shocks that fit up-side down.

Andy
a borris

A mate had coil-overs on the back of his race frogeye to the check strap point and the panel was carved away to clear the upper coil mount. I don't recall much re-inforcing other than maybe some penny washer to help stiffen the area and spacers to fill the gap between the panel and rose joints, this was a race car with fibreglass back so some reduced loading.
David Billington

And race tracks tend to be pot hole free!

I think it's the impact type loading that'll bu**er the check strap mounts.

So welded on on mounts up in the wheelarch with bracing inside the boot may be the way to go.

Andy
a borris

Agreed, the check strap mounts were intended simply to take the occasional downward load, and not a big one at that. Using them to bear the entire weight of the rear of the car; an upward load; along with all the dynamic loads involved, is pretty much to ask.

-:G:-
Gryf Ketcherside

As I wrote, I tried it using coilovers as an adjunct to the useless flattened springs on Lara for one single (dangerous) trip to Silverstone in 2007.

(how should I have spelt optimist? Ah yes. I D I O T.)

The oversprungnessness was terrific and totally terrifying, the car was all over the place when cornering, which was bad enough but when I took 'em off next day the webs had started cracking due to over loading.

I later used the same mounts but had to plate with thick body washers and welded seams to allow fitting the mini shocks to them.

Bill

Bill,

As well as adding higher loads to the check strap points in adding the coilovers you would have seriously increased the rear spring rate due to having the combined rates of the coilovers and leaf springs regardless of the state of them so I would expect serious oversteer issues to have resulted, a very wayward back end.
David Billington

that is one way of seriously understating it Gryf

I had to go to the Silverstone meeting (I was due to meet Anita for one thing!) so I went without testing it although I'd only fitted them as a preliminary exercise. Concept stuff. The previous day.

I almost lost it big time on some of the roundabouts on the road from the Motorway. I never drove anything that scared me so much, never will again...

On another tack, anyone know how to work out what the spirng rate would be of unmarked coilovers with nothing on the box?

Or should I sell these?


Bill

Bill,

Have a look on the web for spring rate calculators. I haven't got any bookmarked but the last time I looked there were quite a few. You need wire diameter, mean coil diameter or OD and ID and free coils.

From a quick google for "coil spring calculator"

Try

http://www.efunda.com/DesignStandards/springs/calc_comp_designer.cfm
http://www.proshocks.com/calcs/coilsprate.htm
http://www.pontiacracing.net/js_coil_spring_rate.htm

etc

David Billington

Well, I used the rebound strap bracket to mount shocks (not coilovers) and thought it worked out pretty well. However, I think I'll be under there this weekend to check for cracks, etc.!! The problem I had was finding a shock that was the right length as well as with reasonable compression/rebound properties for our lightweight cars. Anyone have any brands/models that work for you and are available in the US? Thanks!
Jack Orkin

Bill,

I can easily access a spring rating machine to rate them for you if you need, I did the one's off my midget as a check and have done others

Whereabouts are you?

Let me know

Cheers

Spencer
S Deakin

Thanks for the info David (did I really say Gryf? I told you I was going senile!)

Spencer, I'm in Streetly, where you be then?

Jack, I am simply using shock absorbers from the front end of a Mini, BMC not Beemindubbya. They work OK with my drooping rear springs but I think that better springs will result in a need for a rethink. With the spring platform plates reversed and crossed from nearside to offside and vice-versa.

I'd expect you to be able to get shocks for Minis anywhere.
Bill

Bill,

I be in Rushall, I used to live in Aldridge 'back in the day' and went to Aldridge Comp (Tynings Lane)

Let me know

Cheers

Spencer
S Deakin

Bill, thanks for the info. It seems that a shock for the front of a mini would be designed for a whole lot more weight than one for the rear of a Midget. But, maybe since the passengers sit very close to the shock mount, its not that different. Anyway, you're right, it shouldn't be a problem getting Mini shocks.

Jack
Jack Orkin

I think shocks aren't designed for the weight of the car, but rather the weight (and spring rate) of the suspension?

It's the wheel which is meant to move when it hits a bump, not the car. Though I know that's not always the case with leaf springs!

The shock damps out excess movement of the wheel caused by the spring storing energy.

It also depends on the amount of leverage the shock linkage exerts on the shock too.

AndyB

a borris

My spax adjustables worked fine for many years fitted as the photo. The bracket is welded to the rail that runs to the bumper mounts on the 1500.Being vertical with plenty of movement I was able to set them to there softest setting with nice results.
Carl


C Bintcliffe

A neat cover finishes the job!


C Bintcliffe

This thread was discussed between 03/01/2009 and 10/01/2009

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.