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MG Midget and Sprite Technical - Back end is hitting the bumps

My axle hitting the bump stops over country roads at speed, have fitted a pair of Mark Boldry rear springs (supper spring and can recommend) that have helped but still doing it with two blokes in the car, if I set the damping (have the Frontline kit fitted) any higher the handling of the car is affected along with my back, can you get smaller bump stops or can the originals ones just be cut down?
Alex Sturgeon

Do you mean the rubber bump stops, or are the dampers bottoming?

I run a higher rear than front for stability and to allow for the occasional passenger...

A
Anthony Cutler

Hi Alex that is exactly the problem I am trying to cure.

I want my backend to sit higher than it has over the last 20 years. I look at it like this.

The spring determines the ride height, and also how resistant the car is to riding low.

My car does NOT resist the backend sitting down due to extra weight or riding bumps. I am almost happy that at rest the ride height is just about acceptable.

Therefore shock absorbers aside I need a spring that is a bit more arched and definately a stronger spring rate. IMO once this is right then shock absorbers can be set to do the job they are designed to do which is stop the spring oscillating (Bouncing)

I am disappointed that the springs you have described have not done that as that is what I thought the intention was.

I have considered 2 approaches to this problem, Fitting 1500 springs to my 1275. Or beefing my springs up by adding one or 2 more leaves?

At the moment I have lenghtened my Bump stop platform so that the bumpstops help resist the car drooping at the rear. However on most B roads the car is a nightmare and bounces about like no bodies business. I had assumed this was because the midget Bumpstop was very flexible.

However instead of strenghtening the bump rubber I need to put in a stronger spring to avoid contact.

At least thats what I believe :-)
Robert (Bob) Midget Turbo

Anthony

On the FL rear kit I have my lower mounting plate are looking down with the shock on the upper hole, is this correct? It did seem the only way to get full travel out of the shock

Robert

Ref to the Mark Boldry spring these did greatly improve the car and the springs working well with only me in the car and a light passenger , (with the last springs had this bumping with only me in the car over smallish bumps) can blocks be added to give the axle any more clearance? Its now only a problem with 30 stone in the car over bumpy roads at speed, the answer so far has been to slow down but as its the one area of the car that lets the package down would like to get right

Alex
Alex Sturgeon

Well that is good news Alex, seems that with a more robust spring then contact with the bumpstops can be made to happen. Just seems that the springs you have whilst better could be made even stronger, although then the ride could be too hard for some, not for me however. :-) I think if I could get a strong enough spring then I would put a solid rubber bump stop in place of the extremely flexible standard version. I think the standard version simply bounces the car.
Robert (Bob) Midget Turbo

Robert

Yes its more the bounce thats the problem, not the act of hitting, crested a hill the other day with a left after and with the axle on the bump made the car very unstable for the corner. An extra leaf would help
Alex Sturgeon

I have cut down the bump stops on my 1500 after lowering it and have never had any problems, I also have vertically mounted Mini Spax adjustables which may be helping but a new set of bump stops is a quick and economical check.

Cheers Carl


C Bintcliffe

Alex

You might be able to remove some of the bump stop... this would postpone contact but make any recurrence more sudden.

Seems you need a stronger spring or additional (aka helper) leaf as Bob says.

I use std rear springs from later 80s; they seem fine with me (13st and elder son 15st), although they now are flat with the car unloaded.

As they work fine, and as newer springs have very variable quality In any case, if I bought new springs I'd need a series of lowering blocks.

A
Anthony Cutler

there used to be leaf spring stablizers that just bolted onto the leafs springs...made for pick up trucks and worn out leafs, pretty much universial fit, anyway its just a thought. Here is a site with a good design, granted its for a truck, but no reason you cant copy and make your own, then agian, maybe they can make you a one off.

http://www.mrtruck.net/springs.htm

Curious...what do you mean by bumpy roads? a bumpy road here is a road in bad shape mostly a back country rural road (the old twisty windee roads) that needs resurfacing or Its a gravel farm road...I try to avoid these roads in the midget.


Prop
Props Black Hole

Sorry here is a the home page for the super springs rather then a dist.

Prop

http://supersprings.com/
Props Black Hole

Now here is a cool idea, that would be simple to copy...check out the photo, Oh and (hopefully here is a list of spring helpers, to look into)


http://www.jcwhitney.com/Helper-Spring/600003426.jcw?in_dim_search=1


Props Black Hole

This assister spring only works if the current leaf-spring has plenty of curve when the car has normal static load. Surely not so effective on a flat spring?

IIRC other assister springs has an additional leaf that bolted to existing... seems they would be better for our cars?

Or fit weak coilover with the tele damper? (Less unsprung weight, too?)

A
Anthony Cutler

I had this clunking problem after fitting a rear Koni shock kit in 1976. It was necessary to have the springs slightly re-arched to eliminate this. I have since replaced the springs using sets for the 1500 and still ended up adding a leaf. I also like the car to sit a bit hither in the rear but the ride height looks perfect when compared with photos in the 1971 brochure.
Glenn Mallory

what about the spring stiffener shown in Daniel's book? The one with a plate bolted either side of the spring just behind the hub. I was thinking of making some of these this week, as they will cost nowt. watch this space.
my car has some of those self lowering springs from Moss. I lowered mine by remaking the front spring mount higher. This made the body sit lower over the suspension. I made this mod more than 3 years ago, it has carried on with the good work I started, and has now lowered itself to the point of struggling to get in the drive without scraping. I have an event in 3 weeks, then it is getting raised. The motoring correspondent from our Sunday Times is borrowing my car for the safety fast run. I don't suppose it would get a favourable write up if he scrapes his a*se up the road for 500kms!
Shawn

"The one with a plate bolted either side of the spring just behind the hub."

That will make axle tramp more likely.

The spring length aft of the hub should provide the springing action. The spring length ahead of the hub should provide axle location.

That is why the spring length ahead of the hub is shorter!

Extra spring clamps ahead of the hub help provide better resistance to longitudinal axle movement. If you clamp the spring aft of the hub, sure you will get a better spring rate but you will change the fore / aft spring rate ratio and screw your handling!
Deborah Evans

>>> The spring length ahead of the hub should provide axle location. <<<

Good point, Deborah. I've always considered the front half of the springs to be similar to trailing arms. Although it must be said that perished bushes in the rear shackles can affect axle location as well. Been there - apparently the PO didn't like to get under the car, as all the rubber bushes were completely dead and raggedy when I bought the Midge in '95. Poly all around fixed that!

Cheers,

-:G:-
Gryf Ketcherside

>>>>>>>>apparently the PO didn't like to get under the car, as all the rubber bushes were completely dead and raggedy when I bought the Midge in '95<<<<<<<<


I certianly dont know your previous owner gryf, But Im embarressed and scared by my black stock rubber bushings...they all deterioted FAST (from brand new)....Ive come to the realization these black rubber bushings are good for about 3 years tops, sadly you dont have to drive the car for them to deteriorate...how does that happen


Prop
Props Black Hole

Hi folks,

I'm creeping out from the shadows and can anounce that the Mark Boldry springs are supplied by me.

Alex, I'm pleased they are better than what has gone before. It is possible for them to be re-cambered to give greater ride height.

If there is a need for springs with more camber I can have them made this way. Lower is on the books too.

I noted when we met Alex that even at 6'2", I was looking up at you! If your passenger is also larger than the average bear, there will be implications....

Back to the springs. UK manufactured, high quality material and heat treatment, bolted spring clamps and interleaved to original spec. The handful of springs so far produced have produced good feedback. One pair even came fourth on "The Marathon".

I am about to commission a new batch and would really like to have some advance orders. Please drop me a line for further details.

I started this project due to the horror stories about poor quality springs. Mine are the real deal and are reasuringly expensive.

c$dot$berry@fs$mail$dot$net. Dot the dots and delete the $signs.

Clive Berry

If you are going to shorten the bumpstops, check out the clearnace of the propshaft on the top of the tunnel - I've seen the get damaged from contact there.
Paul Walbran

Clive,
you have mail,
cheers
Brad
Brad (Sprite IV 1380)

Paul we were all talking about increasing the ride height not lowering it, I think weren't we?
Robert (Bob) Midget Turbo

Clive,
did you get my mail?
Brad (Sprite IV 1380)

I plead jet lag!
Paul Walbran

This thread was discussed between 08/09/2009 and 21/09/2009

MG Midget and Sprite Technical index

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