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MG MGF Technical - hight of the mgf

sorry forgot this one question. how high off the ground should the mgf be? i was told that you measure from the center of the wheel to the bottom of the wheel arch? what should the measurement be? my ride in the car is very hard, is this the norm? thanks.
Jim Kenny

368mm +/- 10mm

Measured from the centre of the front wheel vertically up to the underside of the front wheel arch only (don't measure the rear, but do measure BOTH front wheels).

This is done at 17 degrees C ambient temperature, on level ground.

SF
Scarlet Fever

are the TF distances the same - yes, I know it has no hydragas, just curious!
tony

Just a question out of curiosity. What would be the effect of pumping a car up to the standard ride height if it was fitted with lowering knuckles?

Ralph
Ralph

OK measured both side and they are 340mm. Is this why the ride is so hard?
Jim Kenny

Tony, a few days ago (on here, or another bbs) somebody posted the heights for TF - obviously I forgot to note it down and haven't measured mine yet.

archive search ?
JohnP

Jim,

When I first got my F, those were about the height measurements I had - it actually felt as if the ride was softer and the car was pitching back and forth - right up until it hit the bump stops (which it did regularly) when it felt hard!

It sounds as if the Hydragas suspension needs pumping up - a look through the archives on here will find you a lot of details, but lots of garages can do it (same system as the Metro).

Standard advice is to get the tracking checked once it's pumped up, as you're altering the suspension geometry.

Regards,

Mark
Mark Roper

Jim,

Have you had the car from new, or did you buy it second hand? Also, is it a Trophy 160?

340mm is about right for a Trophy 160 LE, this model has lower, stiffer suspension as standard and this would answer your question. If it is a Trophy 160 then it is SUPPOSED to be a firm ride.

If you bought the car second hand it is possible that the previous owner has had lowering knuckles fitted. Knuckles on thier own won't make the ride feel firmer (if they are twinned with uprated shock absorbers then these will affect the ride quality), but it will lower the car to around 340mm ish. The way to check if knuckles have been fitted is by getting your dealership to connect thier Hydragas pump and check the pressure in the system. If the pressure is reading normal on a low car (around 400psi) then knuckles have been fitted and you should NOT pump it up to normal ride height (this will overpressurise the system, causing internal damage over the long term and will make your ride quality firmer still).

Assuming you have a normal F, with normal knuckles then your ride height suggests the system is underpressure - this will make the ride spongy, with longer suspension travel over bumps that may result in bottoming out on the bump stops - i would think that this bottoming out coud be a potential cause for your harsh ride experiences.

HTH

SF
Scarlet Fever

Surely the lowering knuckles must affect ride quality, as the amount of wheel travel is reduced....
Karl Woodhead

To some degree you are correct, yes a lower car has a smaller amount of travel in the suspension (the bump stop is closer tot he upper wishbone), this makes the possibility of bottoming out more likely (not least because an F fitted with knuckles handles better (lower centre of gravity) and therefore tends to be driven more spiritedly ;-) ). But under normal driving conditions the ride quality of a car fitted with lowering knuckles is identical to that of a normal height F. This is because the pressure in the Hydragas spheres is identical before and after.

SF
Scarlet Fever

Jim

340mm is not that low, so no reason for a hard ride, or would hope not as even if lowering knuckles where fitted it is only 28mm lower, I have had mine running at just over 300mm in the past and that was a hard ride but the shocks where knackered.

Has it got std shocks on or uprated as this could also be the reason.

Tom
Tom Randell

>> OK measured both side and they are 340mm. Is this why the ride is so hard? <<

Actually, as you lower the car (reduced hydragas pressure) the ride actually becomes SOFTER - but because the suspension movement is reduced, and there is less resistance in the hydragas 'springs', the ride *feels* harder because the suspension is continually striking the bump stops.

This is why when lowering the suspension with lowering knuckles is so much better than lowering on reduced pressure alone: it allows you to maintain the correct spring and damper rates in the hydragas spheres - and consequently, the suspension is very much less likely to bottom out - this results in a much smoother ride.

More on the operation of hydragas here: http://www.mgf.ultimatemg.com/hydragas.htm

HTH
Rob Bell

I have not yet done the measurement however when I park my car on the driveway of the rented house I have in Coppull for work purposes it drives in without scraping the bottom, when I reverse out it does scrape. The driveway is on a slope and the roadway outside obviously is flat. I have looked underneath as best I can without utting the car on a lift. I hve not had the car very long but would like to know if there is anything that could be damaged? Obviously the chassis is getting a bit of a scraping. The car is 1999 MGF MPi
John Dickson

John

I can imagine the part being ground out is the crossmember under the car in the middle. Mine has been ground out loads of times and even contemplated getting a new one because it was deformed but the boys at Techspeed got a hammer out.

As far as I am aware this should not be a problem as long as it is only at slow speed.

I have a similar problem at home with the drive plus certain speed bumps. The other thing to make sure that is not grounding out are the sills as these are not much difference in height to the cross memeber. If they have been gound out just use some underseal to protect them from going rusty.

Tom
Tom Randell

Tom

Yes it is at low speed, I am also very careful over speed humps, but I will rest a little easier now.
John Dickson

Not sure about all the ride heights and stuff. But I had mine fitted with the 30 mm lowering knuckles, and then got adjustable dampners fitted. Ive had the car lowered so there is only 1 cm between my tyres and wheel arch. Only problem i get is going round round-a-bouts the front passanger side tyre scrubs, whoops! Have to say the ride quality is much better then when i first got the car 2 years ago, but I have a funny feeling my original dampners were totally worn out.

I got the gas pumped back up a bit a while back cos of stupid speed bumps meaning i cant park in car parks, haha.
Edd

I seem to have a problem here. Luckily I got a puncture last night or I might not have noticed it until too late. The puncture was in the left front, simple enough? Well first the spare wheel locking bolt was seized meaning I had to break off the plastic cap to get the spare off. I am under the impression it had never been of before. (My car is a V reg 1999 MGF 1.8MPi bought from Carcraft in Rochdale in January 204). OK now I have the spare off loosened the wheel nuts, jacked up the car ready to take the wheel, easy enough? It would not budge and no rubber mallet as I was in the car park at work and everyne had left. Oh well, a call to the RAC on the mobile who were reasonably efficient and said about an hour (plus or minus). Resigned to a roadside wait I inspected the tyres a little more closely. Both were seriously worn down on the inside. The punctured tyre, a Michelin would have lasted maybe another 50 miles, however the right front which was a MAXXIS (never head of them before) was showing about a half inch of canvas almost all rounf the circumference of the tyre on the inside. Like I say luckily I got the puncture because otherwise I would have been off up the M6 from Chorley to Edinburgh Friday night. Any way the RAC duly arrived and knocked off the wheel with a rubber mallet fitted the spare and I got home to Coppull missing only the first five minutes of the Portugal Hollnd game. First thing this morning it was off to National Tyres in Chorley for 2 new Avon ZR3's (£144 for the pair). I have now checked the ride height on the front with new tyres and the reading are 330mm right front and 325mm left front. These seem a bit low from what I have picked up on this BBS so it seems I eed to have the suspension pumped up and then the tracking checked. Since I have just paid £144 for the tyres (I don't want to do the same to them) and £90 for Road (theft) tax. Totally obliterating my monthly food budget does any one know of a good reasonably priced (I hesitate to say cheap) place where I can get the suspension pumped (Checked) either in the Chorley area (where I work) or in the Grangemouth/Falkirk area where I live. (I only rent the house in Coppull for work purposes)

Thanks

John
John Dickson

John, you probably don't need the suspension pumped up, but you definitely need to get the tracking settings checked. A *decent* tyre specialist should be able to help you out - 40 quid is a reasonable price to pay for this service.

There are alternative tracking settings to try if tyre wear persists - but that is a topic for another day! http://www.mgf.ultimatemg.com/tracking.htm
Rob Bell

Rob, why do you reckon the suspension doesn't need pumping up? From the measurements John gives the car appears to be about 40 mm too low (unless it's had lowering knuckles fitted)?

John, can't recommend anywhere to get the suspension pumped up, but lots of non MG garages can do it, as it's the same kit as for a Metro. For reference, I was charged £35 last year by my local garage.

Mark
Mark Roper

John,

The place that I use for tracking is at the end of the M8 at Edinburgh, but I believe that there is someone in the Bonnybridge area who is pretty good. I'll e-mail you with the phone numbers.
David Clelland

I forgot to mention on the previous post, but I don't know if the car has been fitted with lowering knuckles. How would I recognise if this has been done?

John

JDickson@nospam.fairport using airport transfers tunbridge wells.co.uk
john.dickson@nospam.blueyonder.co.uk
John Dickson

<<one know of a good reasonably priced (I hesitate to say cheap) place where I can get the suspension pumped (Checked) either in the Chorley area (where I work) or in the Grangemouth/Falkirk area where I live.>>

I believe there's a whole bunch of people meeting up tonight, that will be able to kick your tyres and hmm and ahhh about your ride height.

Birds and Bees nr Stirling at about 7:30-8pm ???

www.csmgf.co.uk for more details.

Come on DC, not like you to miss an opportunity to promote the group ;-)

paul weatherill

Mark, John, sorry, I missed the 330mm ride height measurement - which is a little too low. The problem here is that it is going to be really hard for someone to pump the suspension up with out the car ending up looking like a 2-seater LandRover... :o(

Yes, the suspension does need a little extra pressure. I'd suggest that you take your car to a back-street mechanic who is able to service Metros. Get them to aim for a 345-350mm ride height. Then, when you drive the car around for its geometry check, the car will have reached its final ride height - most likely in the 355-365mm bracket, which will be fine :o)

Cost? Shouldn't cost more than 20quid for the extra Hydragas fluid - and as I said, a 4-wheel geo check ought not cost more than 40quid.
Rob Bell

Just had to have my VVCs suspension pumped up
It was about 320mm - now 340mm (it's been lowered)
cost was 35quid, while I waited.

It's possible to adjust too high yourself, but impossible to adjust too low without the pump !

With regrd to checking for lowering devices, then, as SF wrote earlier
>>If the pressure is reading normal on a low car (around 400psi) then knuckles have been fitted<<

perhaps my wife won't need to visit the osteopath so frequently now ? :-)

Steve

Paul

Will be back in Scotland on a more permanent basis from August 16th. Will give you plenty opportunity to kick my tyres. DC has infact already promoted the group about a week ago. Not sleeping afterall. And thaks to all how hve answered my questions. I can now see the wood from the trees, just a little bit better.

John
John Dickson

Good to hear John,

<<DC has infact already promoted the group about a week ago. Not sleeping afterall.>>

Knew he wouldn't have let us down. good job DC.

look forward to meeting you at one of the meets. Or even a run if I can manage to get out of my bed on a Sunday morning. ;-)

paul weatherill

>>I don't know if the car has been fitted with lowering knuckles. How would I recognise if this has been done?<<

John,

When you've got lowering knuckes fitted You pump the car up to a certain pressure (400 psi)and not to a certain ride height. I'd get them to pump it up to 400 psi and see what your ride height is then and if it's about 340mm then I'd say it's been lowered. If however it's about 360mm I'd say that it's not been lowered and I'd set it to the correct height measurements.
David Clelland

This thread was discussed between 22/06/2004 and 01/07/2004

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.