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MG MGF Technical - Cold weather & ride height

In the summer I had Lowering Knuckles fitted to my car. The car was lowered to 340 at the front at 20 degrees temperature. The rear of the car height was 330. At first I thought this was a problem but thanks to answers on this BB It was quite normal. The problem I have now that the car has lowered due to the cold weather. I understand that it is 0.6mm per 1 degree change in temperature ( I dispute this Rover claim. I think it is much higher).

Today I measured the car at the front it was 225 and the rear it was 113. The temparture was 2 degrees. I am worried that the car will bottom out. The question is 2 fold. Will the car bottom out at this low height? (and it will get colder hence lower). The second question is how low car can the car go till it hits the bottom? (i.e its lowest point. This means you have no suspension left, grim news).

I am also aware that you should measure the car on the front wheels. But as the back it about 10mm, 12mm lower there is a limit to how low you can go and it is the back that is my main concern.

Other points are. I have standard shocks and standard wheels (15inch) and tyres.
Steve

>Today I measured the car at the front it was 225 and the rear it was 113

Steve,
I think you measured not at the common points, or did any typing failure.
- measure between the middle of the wheel up to the metal boarder of the wheel arch.

See here:
http://www.fortunecity.de/hockenheim/senna/253/defects/ridehightbroken_a.jpg

Anyway, I measured the lowest possible point at may 05/96 MGF with 280mm.
Non temperature related, the pure mechanical lowest point. At this point the upper wishbone reaches the rubber piece.

Non temperurerelated, because all Hydrafluid had gone :)

http://www.fortunecity.de/hockenheim/senna/253/defects/blownhydra.html

All around, you need to check the ride hight once a year as standard. If you have a lowered suspension you need to be much more sensible on any hydrafluid loss and drop of the ride hight.

I suggest to add a tolerance of +5 to 10mm if you go to a hight setup. This will spend enough tolerance for the 'typical lowering over 6 or 7 month'.


Dieter
Dieter

Dieter

It is a typing error. It should read 325 and 313.

Thanks for the bookmarks and the reply.

Steve

Snap Steve - last night I too was concerned about one side of my F in particular - just able to get one finger between tyre and wheel arch. Don't know the actual temperature tho. Standard knuckles & wheels.

Like you I have my doubts about Rover's figure of .6mm per degree.

As you go lower obviously you'll have big problems with 'speed humps' and the like. I guess the suspension must rest on a stop eventually to keep the tyre off the wheel arch so that you can still steer - I must be quite close to it.

Dieter what happened when you lost all your fluid - I assume you could still drive it with great care.

jt
John Thomas

I had my winter tyres fitted on Saturday, and while the wheels were off, I noticed that the "contact" point of the rubber stopper was relativelty clean. In my opinion, the car does not sit low, but now with the temparature at zero and lower at night, I am wondering if this is ok...I had the ride height and geometry reset by Rover only 4000 miles ago....

Hmmmm

Jason
Jason

>Like you I have my doubts about Rover's figure of .6mm per degree.

<grin> I know someone who has some 'things' to approve that...
- refrigirator
- green stuff
- recently damadged unit
- a little pump :)
... LOL.. I must think about it...
I beleave I need the unit uncutted for some test should fixture with any 'cyano adhesive' work :)

According to the ride without right side spring function.
:-/ The wife nearly got seasick. The car nicked like a row boat in heavy sea. Ech bump let the rightside mudflap scratch on the road. (1.5cm between mudflap and road)

Yes ,I drove about 30 miles on motorway at about 50 mph with care (little care, not great) but will not recommend this for other owners. (because of warranty and goodwill and repair costs). I recall a report of Tony some weeks ago. He did the same but only a short distance.

I knew what was happened and that I had the nearly ready own pump at home.
I wonder why the front unit is still OK. It does not matter me at all if the front one blows soon. In that case I would stop and think on the 'health' of the just changed rear one.

Cheers
Dieter
Dieter

Steve,

My car was set to 317mm in the summer when Techspeed lowered my car. This was OK with just me in the car, but on a trip around France with a passenger, a weeks luggage and 30 odd bottles of wine I scrapped from one bump to the next.

After that the car was set to 325mm and hasn't been much of a problem - the mudflaps do scrap occasionally. It was even OK in the Lake District doing all the Passes 2 weeks ago.

Haven't measured the car recently - but will do so to see if it has dropped much.

Paul
P9 VLS
Paul

I had the ride height checked a few weeks ago and it was fine, however as others have mentioned, going over speed humps on my way home I did notice some bottoming out. As the temperature is set to go below freezing next week I might be riding around on the bump stops soon. I'll check as soon as I can on the current ride height

John
T69 ABW
John

> 0.6mm per 1 degree change in temperature ( I dispute this Rover claim. I think it is much higher).

Just another thought.
We need not know any proposal for dayly rides !
But the actual hight.
The measurement needs needs only a few seconds .. OK, and sometimes a laughter of people who see you running round the F.

Rated Value standard is 358 to 378 stated by the manufacturer.

The rated value with lowering knuckles is 338mm (IMO) with no written tolerance for my knowledge. So take 80 percent of the standard and look for a hight of 330 to 345mm under EACH temperature condition.
Wether its cold or warm a suspension in that ranges will work !

And if you find other values, then valuate for your own wether you are just for some hours at th north pole or for holydays in the sahara. ;-) or wether you do not know how to hold the meter.
And decide for your own wether its useful to pump it up or not.

Cheers
Dieter



Dieter

Please note, when measuring, ride height

1. The car must be on flat level ground
2. The hand brake must be off
3. Roll the car forward 1 yard to relieve tension (in the suspension, not you!)
4. Bounce the car a few times, front and back.

Without the above routine, measurement cannot be anything but, at best, a rough guess. All of these points can give misleading results if not followed.

Tony Smith

I will just add that you can lose a couple pf mm by measuring to slightly different places on the wheelarch. I am told that the correct point is the commencement of the radius from the main panel. That is to say you have a straight edge along the panel and where the lip starts to curl inwards is the point of measure, not the underside of the lip.

Just an additional point that I was not originally aware of.

Rog
Roger Parker

>lose a couple of mm by measuring to slightly different places on the wheelarch

Yup, but not 30mm ;-)
See this pictures and you know what I'm bothered about. The meter was clamped between lip and arch.

http://www.fortunecity.de/hockenheim/senna/253/defects/blownhydra.html
Row 14 &15
and this one
http://www.fortunecity.de/hockenheim/senna/253/defects/wrong395.jpg

http://www.fortunecity.de/hockenheim/senna/253/defects/uglyindarkness.jpg
(shot at 7.5C a few hours ago just uploaded a few minutes ago)

Tomorrow I'll get home early and then ... :)
Dieter

Checked the car this morning when it was cold:

It was checked as per Tony's instructions. Temperature was 3 degrees. Measure on front 325. Measure on back was 310. This was checked from the centre of the wheel to the radius from the main panel on the wheel arch (not the plastic trim that fits over it). I think it will be a trip to the dealers to have the suspension pumped up, However I do not want to keep pumping up the suspension in the winter and letting gas out in the summer. It seems wrong that the suspension should change so much 340 at 20 degrees on front in summer to 325 at 3 degrees in winter. By my calculations the change in height is not 0.6mm but 0.9mm.
Steve

Steve,
I read again your first message. You wrote that the car was lowered in sumer by knuckle set to 340 at 20 deg.
:)
Did you measure it your self ?
If not dont beleave in dealer stated hights, see my dealer visits result above :-/

According to the knuckle change. IMO they must 'run in' I'm sure that new knuckles wear a little at the point where the lower plate meets the cambered plate in the wishbone.
And also the upper seatr where the bolt meets the aluminum hydragas units piston.
So IMO subtract about 4 ti 5 mm because of this 'running in' or better said 'settle'.

Additional to your 0.9 calculation ... that may be IMO because I do not beleave that the temperature correction is linear.

As Tony said, too much precision is not to reach.

So let pump up.

Cheers
Dieter
Dieter

Measured my car last night - temp was 5 deg C and front height is down to 314mm!

Car looks great - will find out on this weekend at Warwick whether this will cause any problems.

When the car was set at 325mm the temp was 21 deg.

Which makes the fall 0.64mm / deg C.

Would the fact that I have stiffer dampers help supress any change due to temp?

Paul
P9 VLS
Paul

strange car we all have: looks great, esp. during winter, but destroys the bottom of the car... :-/

long live springs!!!!!!!!
Dirk Vael

Yep

Phone the dealer today. The car goes in next week to be raised and tracking checked I was told on the phone that the car may have settled and that the hydrogas fluid may need topping up about once a year as it is possible for the hydrogas mixture to evaporate slightly over the year. This does not mean it is leaking. anyways they will check for me.

Reply to Dieter.
I believe you are right the knuckles do need to settle in and I hope this is the answer. With regards to the checking I checked the car car height the next day after the work had been carried out on the lowering knuckles, as they said that if it was too low or high they would change it so I was happy. I left it at 340 beacuse the back was 330 and felt that this was a nice height overall. I only wish they front and back were the same.
Steve

After a night in my cold garage I have ~ 310 on one side and ~315 on other measured from plastic lip of wheel arch to roughly wheel centre.
I approach speed humps with care.
jt
John Thomas

To be quite honest I have noticed no great change in ride height between summer and winter.

The only people who have made any great changes have been various dealers and more recently myself (as former unable to manage).

If the car is new to you it is most likely that the car has been set wrongly by the dealer or garage. Some cars have been lowered with knuckles (second hand owners take note) which drop the car 30mm (generally available ones anyway) without changing the pressure on the Hydrogas unit. This should be established first before going mad coz your car is 338mm or lower :-).

I have to drive over lots of speed bumps near where I live. One time my car was lowered to about 330mm by a dealer. This caused my K&N cold air pipes to scrape along the ground (Not any more, thanks Tom) so I think this would be the lowest I could realistically go with my car.
Tony Smith

I come to this thrad rather late, and most of the important that I would have thought of have already been mentioned.

Steve, I am glad to hear that you are having the car raised because:

1. Yes, you'd almost certainly bottom out the suspension at a ride height of 310-325mm

2. Be very wary with standard dampers- they have an operational range that has been chosen for use with standard suspension settings- extremely low ride heights mean they have less travel internally, and their efficiency is copmpromised. Ultimately, they will wear out excessively quickly.

WRT linearity of the delta mm to delta celcius- it is almost certainly NOT going to be linear, and there are going to be other factors that'll effect the result. Recall that the hydragas unit compresses in a vertical plane, whereas wheel movement circumscribes an arc. Further, the resting gas pressure will presumably influence the ride height. I am sure that there are plenty of other variables- take the 0.6mm per degree Celcius as a guide only.

Rob
Robert Bell

This thread was discussed between 17/11/1999 and 18/11/1999

MG MGF Technical index

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