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MG MGF Technical - Ride Height

Point me in the direction of previous threads if I’m going over old ground but I’m fishing for advise regarding ride or trim height for my ’96 MPI.

The Rave CD informs me that trim height should be 368 +/- 10mm from front hub centre to wheel arch. I’ve been running my F at circa 345 – 350mm for over 12 months now, except for a week following a repair where the garage set heights to 375 – 380. At this time I found the ride harsher and less compliant so I reset to 345 with improved results.

Is there a problem with reducing ride height on the hydragas? Also, how do the lowering knuckles work, are they easy to fit etc?

Thanks all and happy motoring.

Russ.
Russ Mellor

Rob's site is always a good place to start looking -

http://www.mgf.ultimatemg.com/

JohnP

Thanks JohnP,

Referring to http://www.mgf.ultimatemg.com/ the example shown was lowered to a height of 330mm, from previous experience I know this to be an impractical height for our local roads and the recent proliferation of speed humps. So I conclude 345mm should give no problems.

I will investigate lowering knuckles in the New Year when the weather and daylight will be more suited to working on the car.

I’m also considering changing my shock absorbers, with trade prices I can get a full set of standard shocks for circa £100.00 and am wondering whether the extra expense of upgraded units is a worthwhile investment at this stage?

Happy Motoring,

Russ.
Russ Mellor

i had unnatural front tyre wear when the suspension on my F sank too low (loss of inner tread first)... this was corrected when the ride height was re-set tho.

the handling is also better with the ride height in the upper limits... although it may feel better when set lower.

i'm no expert mind... just a warning :)

stu

ps. cam you not post on these threads if you're not logged in...???? this reply may appear twice :O
stu forster

Stu, if ride height changes, so does the toe-in.

This means that the car was wheel aligned with the car at a certain height, at which point it was good. Then, when the car lower over time the wheel alignment deteriorates. And when the car is then brought to the original height lees tyre wear due to better alignment.

Johan
Johan Slagter

I have used Rob's site as my bible for ride height and tracking.
My original NCT tyres wore perfectly using his figures. I set ride height from wheel centre at 345 and the vehicle also runs lowering knuckles, poly bushes and AVO shocks.
Andrew Regens

I’m interested in the relationship between ride height and toe in. Following changing front tyres I re-tracked to standard settings and chewed through the inner edge of the tyres in the space of months. This was with no changes to ride height.

On investigation I reset to 0 toe in and have appeared to have solved the problem. If the toe-in is set at a certain ride height does it matter if this is lower than the standard spec?

Running above the standard height for a week (+ 12mm) was appalling, it looked rubbish and gave an intolerable ride. Handling and looks appear much sharper now I’ve re-set to a sensible level.

Russ.
Russ Mellor

Russ, to see how toe-angles change with ride height, have a look at John Englaro's figures on http://www.mgf.ultimatemg.com/group2/suspension/tracking.htm - in essence, the lower the car, the greater the toe-out figure.

Therefore, if you set toe-angle at one height height, and then change the height setting, the toe-angle will change resulting in accelerated tyre wear - exactly as Stu classically describes.

345mm is perhaps a little low on hydragas pressure - you may find that you'll bottom out the suspension, which is less than ideal, handling and ride-wise.
Regarding lowering knuckles, most are machined such that the ride height ends up at around 330mm at 400psi hydragas pressure. Therefore, you might want to consider getting the displacement cones machined to obtain the desired ride height, or perhaps use MGF Trophy knuckles (which give a 350mm-ish ride height as standard).
Rob Bell

Cheers Rob,

I’m glad you pointed out the relative heights of the lowering knuckles, as 330mm would be a killer on our local roads.

I’ve decided my course of action and will run at 345mm through the winter and have the tracking checked when I’ve achieve desired heights. As it appears to have settled on the n/s and is sitting lower than the o/s.

In the spring I’ll go for the TF lowering knuckles and set the hydragas to 345mm. At which point I’ll also replace shocks with new standard units and replace any required bushes.

Thanks for your advice,

Russ.
Russ Mellor

Russ, there is a significant gain to be had by replacing the standard shocks with some suitable after market items. I've got Bilsteins (obtained from Tech-speed), and I have to say that the ride and handling are transformed.

These aren't the only options: Spax and Avo sell adjustables that'll fit (although beware setting them too hard, as Andrew found out - http://www.mgf.ultimatemg.com/group2/common_problems/CoH/suspension_failure.htm )

If you want to retain standard parts, then another popular choice are the Trophy dampers - these will certainly avoid the damper mount problem, as they are designed to work with the existing hardware...

Good luck with the changes! :o)
Rob Bell

Just a word of warning, on very hot days be aware that the suspension will rise. Mine went up 20mm !.
Andrew Regens

I have had my mgf lowered by Mike Satur, which improved the handling, however recently i have noticed that the car "bottoms out" all the time, even on the tiniest of pot holes. I am worried that I will do some permanent damage.

Any ideas?
andreahall

Andrea

I understand your concerns.

Are you sure the car is actually "bottoming out" or is it just a noisy bump? How does the car behave when you go over speed humps? This is a better test of clearance than pot holes.

I believe the Mike lowers an F by about 25-35 mm. Putting your car an inch closer to the tarmac should not use up all the suspension movement.

Perhaps the shock absorbers are getting a bit tired? and/or the springs? Sounds like either compression or rebound problem rather than a clearance problem.
JohnP

>>Perhaps the shock absorbers are getting a bit tired? and/or the springs?<<

John,

You obviously have had a hard day and you need to get home to Lyn - Andrea has an MGF :-)
David Clelland

DC

You are quite right. Missed it even though I mentioned the F. A trip to the pub last night has refreshed the parts ...

Sorry Andrea.

JohnP

Andrea, have you measured the ride height of your car? Being hydragas, in the cold, the ride height drops - and it may be that the ride height of your car is now much lower than Mike Satur would have intended.

Probably the best thing to do here is to have a chat with Mike, and perhaps arrange to have the suspension pumped up a bit.
Rob Bell

I’ve found that much lower than 340mm gives clearance problems (speedhumps and potholes) most of the time. Whereas, 345mm seems to give just enough clearance with good ride and handling.

On consideration of the shocker debate, I do not think that a stiffer shock will benefit the bumpy local roads. I think my F benefits from not being over sprung, I appreciate that on a track or a smooth road a stiffer harder ride would reduce roll etc. But if your bouncing down a county road with all 4 wheels off the ground they might not be such a good idea!

I’d be interested in seeing comparative tests on shockers or hearing whether either TF or aftermarket units are considered a worthwhile mod.

Cheers, Russ
Russ Mellor

Russ, don't forget that there is a difference between spring rates and damper rates. A car can be softly sprung, but use firm dampers - a combination that was strongly promoted, amongst others, by the late and great Colin Chapman. Using 'firm' dampers can improve ride comfort as well as handling, by attenuating the secondary bounce effects - which is precisely what the Bilsteins on my F achieve :o)

As for a direct comparison of dampers - that would be tricky: you'd need to use the same car, but swap the dampers over: a fairly laborious task - but not impossible. However, it boils down as to who would provide sponsorship for such a test...
Rob Bell

Slightly tangential; should I be very worried about the fact that the Bilsteins that Tech-Speed fitted this autumn have started to make squeaky noises whenever I go over a speed bump or pothole? Or should I leave it until I next go there for a service (probably another six months)?

My gods, they sort out the handling, though!

Jamie
Jamie

Jamie,

Give TS a call now, for three reasons - one, because the Bilsteins shouldn't squeak; two, because TS will be as concerned to find the cause as you and three because this is their slack time of year, whereas in six months they'll be busy with race prep again.

Actaully, this last reason is a good reason to adjust your servicing to the winter period if you can.
Dave Livingstone

Jamie,
Be very wary. I dont think it's the Bilsteins I think it's the turrets comming away from the inner panels.
Go to Robs early reply on this thread and look at the refered site. My car started as a squeak !!!!!
Good luck.
Andrew Regens

Rob,

Have you had the rear turrets re-inforced for the Bilsteins? I notice from the Techspeed site that the do a lowering package including the Bilsteins and rear compliance washers but do not mention the rear turrets - are the mods not needed for their setup?
Kevins

There are lost of Techspeed cars running the Bilsteins with no problem to the rear turrets. The settings on the Bilsteins are unique to Techspeed and were designed for road use, albeit from their race experience.

Having said that, the F's rear turrets are weak points. We have to remember that the welding on Mayflower bodies was hand done - no robots! The MGF cup cars had to have triangulated strengthening sections welded in this area.

My own car (equipped with Techspeed's Bilsteins) developed a squeak on the drivers side, which was eventually tracked down to a crack in the bodywork above the rear turret (rather than the turret itself). Although welding cured this temporarily it kept returning and eventually the Cup car triangulation points were necessary. This was an engine out job. Plenty of pics available if anyone's interested.

So, Jamie - don't worry just yet, but get down to TS as the earliest convenience.
Dave Livingstone

Forgive my typing - that should be "There are lots ..."
Dave Livingstone

OK - some pics here
http://www.mgs-on-track.com/index.php?pg=165
Dave Livingstone

Kevin, no, my car doesn't have the reinforcements - and I've not had any problems since the suspension was uprated some years ago.

The problem of the shock absorber mountings is not so common as to make reinforcement regular practice. I'm not sure how many TS have had to reinforce - they've probably done more for cars fitted with other brands of shock absorber than for those with the Bilsteins.

Jamie, as Dave and Andrew have already said - get in contact with Roy and get the squeak investigated. You don't want this to happen: http://www.mgf.ultimatemg.com/group2/common_problems/CoH/suspension_failure.htm
Rob Bell

Eeek! Right, I'll call Roy then.

The squeek began the instant the Bilsteins went in; suppose that this could be commensurate with either a faulty damper, or with the increased stiffness impacting on the turrets. I'll report back.

And the VW camper is still delivering 18mpg... the nice garage said that it's running slightly lean, if anything, and that they'll need to have her in again for a closer look. Why oh why didn't I make sure that *one* of my vehicles was reliable? :-(

Jamie
Jamie

Dave,
A very neet solution, mine started that way on drivers side but shattered on pass side.
The squeak started at once but I could not find the source until to late.
Andrew Regens

Andrew,

Yes, these were official cup car reinforcement parts. Thankfully Techspeed were very involved with the production of the cup cars back in the early years and had access to them.

My problem only ever developed on the driver side and was, we believe, down to an inherent weakness in my particular bodyshell. Certainly out of all the cars that Techspeed have fitted their Bilsteins to, mine was the first and perhaps still the only one to experience this problem.
Dave Livingstone

This thread was discussed between 08/12/2004 and 16/12/2004

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