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MG MGF Technical - Lower arms front. ( For the Techs )

Having great amountof fun today with the F. I would like to show you pictures of my front tyres only six months old but fear I would be arrested ! They are terrible ! And bloody expensive !


I was talking to Mike in general about my rather rapid use of track rod ends and he has kindly informed me of his cheaper versions. Now I am sitting here with the drivers side hub assembly beside me and well the upper ball joint has certainly see better days but is no way knackered. The lower ball joint on the wishbone is also okay. Wheel bearings were recently replaced so no problems here.

I am seriously starting to think that my sub frame is bent or prehaps the wishbone.
I did kerb the thing along time ago but seemed to be able to get it tracked up okay all except the camber which was always negative from lowering the car. From memory of the last check of ride height was about 329mm.

Anyway I will pursue this as far as I can and having read the workshop manual I tink it is possible to repalace the lower arm by slightly lowering the subframe. Is this the case or does the damn thing have to be totally lowered to gain access to the rear bolt securing the wishbone.

Also upon freeing the anti roll bar on the wish bone to check the state of the wish bone bushes they seem okay but my friend was concerned that the wish bone doesn't move freely up an down and is more like sprung feeling to it. Is this normal ?

Help before I trade for a Mk 2 MR2 which my mate has bloody quick. Sorry !














S Laithwaite

Update. Hub and all the rest of the gubbins are back on the cart. I need a donkey now.

No seriously. By eye and I know this is only vey very approximate but we have eyeballed both front wheels and they look to be toe out by a hell of alot. Either that or the camber is giving the visual effect.

Any ideas on this issue most welcome. I will measure the ride height in about an hour or so and let you know.
S Laithwaite

Okay nobody cares I am sorry for suggesting the MR2 Mk2. Just had a look at it's front end very briefly not alot of metal in there !

However the F is all back together again new upper ball joint driver side passenger side tomorrow.

We did some very basic checks and I mean basic. I am lucky to have a rather large vernier height guage here and I measured the ride height. 332mm. Now as I have said many times this car was lowered by techspeed so I assumed their shouldn't be to much of an issue with 332mm. Another measurment with the height guage from the bottom of the rim ie just touching it and then drawing it up to the top of the rim. This resulted in at least a 5-7mm gap at the top. Hardly laser alignement I know but this to me would be suggestive of a hell of alot of camber negative I think.

Why oh why have I got this problem. I tried jacking the car from the front cross section of the subframe and repeating this rough measurment. It did have an effect but still would leave a smaller gap.

Somebody in Rover come clean why did you not put camber adjustment on this car. Too expensive ????







S Laithwaite

I have no answers to your specific problem, but as to the lack of response - it's the MGCC international long weekend at Silverstone so everyone who knows anything will more-than-likely be there.

Hang around until late tommorrow and you'll probably get some sensible responses.
A

Hi Stephen,

yup, everyone has been at Silverstone! LOL

Regarding the lower suspension arm.

To remove, you will have to drop the front subframe. Whether you have to drop both sides (if you only want access to the one lower arm) I am not sure, but this may be possible, although this is not something that I've tried (Andy and I were planning to do precisely this on Scarlet).

If you've read the workshop manual, then you'll know that you'll have to disconnect the steering column from the steering rack (attached to the subframe). But the rest of the job looks very straight forward. The front bolt for the lower arm comes out easily though the access hole in the subframe, and once the rear of the subframe is lowered, the rear bolt will come free readily too.

Regarding potential damage to the subframe, or even mis-alignment, normal 4-wheel tracking will not pick this up. You need to check the positions of the datum points on the subframe to confirm alignment and thrust axis.

Regarding toe-out. If using Tech-speed lowered suspension, then the front toe-angle should be 0º (parallel) - so no toe-out should be visible. If the wheels are indeed toe-out, then this is likely to be the root cause of your tyre wear.

If the tracking is changing frequently, then perhaps there is a problem with the threaded ends to the steering arms???
Rob Bell

Thanks Rob. Even more food for thought there. I have emailed Mike and I hope that even a slight bend in the subframe is not the case. I base this on the fact that the wear although very bad is more or less equal on both front tyres.

S Laithwaite

Stephen, the common things happen most commonly - so I doubt that the subframe is at fault - although this is something to consider if all other avenues have been exhausted.

Did you replace the worn ball joints?

What condition are the track rod threads in? Before replacing my steering rack, I found that the tracking had to be reset frequently. Since replacement (for different reasons), the tracking hasn't really needed touching...

Tracking remains THE commonest cause of tyre wear.

The cause of the premature TRE wear I don't have any ideas on - not something I've come across before...
Rob Bell

The balls joints in my opinion were not too bad but I replaced them anyway.

What exactly do you mean by track rod threads I assume you mean the fitings on the rack to which you screw the track rod end into. If so then I can't give an answer as I will be replacing the ends later this week.

Now I have to admit the car was riding very low during the winter and I mean low. Having fabricated a pump I raised the car over the weekend to 357mm. I have to say that from where it was 330mm it seems to actually have a suspension now ie something to spring on. However I was of the opinion that with whatever techspeed did to the spheres,I believe this to be reducing the length of the kuncle joint, then this height of 330mm should be okay. What do you think ?

Another thought is that as I mentioned to Mike, is that for what the gague on the home made pump is worth it was indicating a pressure of roughly over 300psi. That was at a ride height of 357mm. If I recall the workshop manual says a pressure of 385 psi is the order of the day assuming a ride height of 368 +- 10mm. If the gague is anywhere correct then I am wondering was there any fluid worth talking about in the system.


S Laithwaite

>>What exactly do you mean by track rod threads I assume you mean the fitings on the rack to which you screw the track rod end into. If so then I can't give an answer as I will be replacing the ends later this week.<<

Yes, they're the ones.

>>However I was of the opinion that with whatever techspeed did to the spheres,I believe this to be reducing the length of the kuncle joint, then this height of 330mm should be okay. What do you think ?<<

Yes, a 330mm height is perfect given the length of the mechanical linkage between the sphere and the upper suspension arm.

It sounds as though the gauge on your pump needs re-calibrating. To get about 360mm with a Techspeed lowered suspension would need a pressure of circa 4-500 psi. So removing a little bit of fluid would be a good idea.

When setting suspension height, never go by the pressure on the pump. That's a recipe for diaster. Always go on suspension height... I find that the methods described on http://www.mgf.ultimatemg.com/howto_lower.htm#with works well :o)
Rob Bell

S,

Sorry, but A is correct, a large quotent of the BBS 'regulars' were having a jolly at Silverstone this weekend. We do care, it's just we weren't here! :-)

Removing the lower wishbone is the next job to be done on Scarlet. I need to replace the ball joints and to replace the lower one i need to drill out the rivets that secure it to the wishbone and bolt in the new one, this requires removal of the lower wishbone from the subframe (and probably a pillar drill which i haven't got - but this is another story...)

You are correct, to remove the wishbone you need to (partially) drop the subframe as the rear bolt is prevented from being removed by the front bulkhead. I was hoping to have a go at this over the weekend, not sure how long you can wait, but (assuming all goes to plan) there will be a step-by-step gallery on the SOS site shortly afterwards.

SF
Scarlet Fever

>I did kerb the thing along time ago but seemed to be able to get it tracked up okay all except the camber which was always negative from lowering the car. From memory of the last check of ride height was about 329mm.


Can I ask an obvious question... How have you lowered the car? Have you just released hydragas pressure, or have you fitted lowering knuckles?

If the former, then that could be the cause of most of the problems as the geometry is off when the suspension is compressed. With the latter method, the suspension maintains its normal position and pressure, with a shorter "spacer" to alter the ride height...

When my car was set to the "standard" height, the pressure in the suspension was ~400psi by the pumps guage...

Neil.


Neil

Scarlet. I will not be removing these for at least three weeks so no problem with time.I was rather hoping that the subframe only needed partially dropped as other wise coolant pipes have to come off.

Neil. The car was lowered by techspeed so I as I mentioned earlier the knuckles or are they roller feet as shown in the manual should be shorter. Also on another thread someone has mentioned the cups are machined. This I would like further explanation of as I have never seen one of these spheres in the flesh apart from when they sre on the car.
S Laithwaite

The original spec for the Front wheel alignment was 10min toe out, this was wrong!

I had my car reset to 10min toe IN at the front and rear to cure the tyre wear and make it more stabble at speed.

Cheers

Alastair
Alastair McLeod

I agree with Alastair regarding the tracking - although I wouldn't quite go for quite as large an angle as that (although Alan does, and finds it works very nicely on his car). My preference would be for +0º5' (Toe IN) per wheel.

It certainly cracks the tyre wear issue. :o)

Both Nicholaj and I have tried a whole range of tracking settings. The ideas behind this, and a summary of findings can be found on http://www.mgf.ultimatemg.com/tracking.htm

Stephen, I'd certainly get the tracking reset to remove that toe-OUT you've noticed. I'm sure that this is contributary to the tyre wear that you've documented - and I'd certainly do this before undertaking anything else that'll be much more expensive...
Rob Bell

>> Scarlet. I will not be removing these for at least three weeks so no problem with time.I was rather hoping that the subframe only needed partially dropped as other wise coolant pipes have to come off. <<

Good, i'll see if i can get the work done over the weekend and hopefully you will be able to see how i did it shortly afterwards.

The workshop manual says that the wishbone can be removed without draining the coolant and detatching the hoses. I haven't checked this but providing the sub-frame is only partially dropped then this should be the case.

The other issue is of course the braking system. In Scarlet's case i have already stripepd down the hub and this meant detatching the brake caliper. Because it is detached i have managed to avoid bleeding the brake fluid. You see the brake hoses link the car to the calipers and the calipers are on the hub which is carried by the wishbones and subframe. Therefore the car is linked to the subframe by the brake hoses.

It is entirely up to you how you resolve this, in my case i needed to strip down the hub anyway so it wasn't an issue as i had to unbolt the caliper. You may prefer to bleed the brakes and detatch the brake hose from the caliper - whichever is easiest.

SF
Scarlet Fever

Rob is right concerning my tracking at the front. I do use 10 mins toe in. At the rear however I run 0. This is the compromise I have found over the years to be the best for me for the type of driving I do and the rubber I run on the car. Tyres play a huge role here as well so what is right for one person and car may not be for another. You need to experiment.

What is important always is compliance washers on the rear and a thrust angle of 0. If you haven't got this at the start almost everything else is a waste of time, effort and money.

Alan
axdunsta

Alan, does running the rears parallel not make it a bit oversteery?

Alastair
Alastair McLeod

This thread was discussed between 21/06/2003 and 24/06/2003

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