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MG MGB GT V8 Factory Originals Technical - understeer
been playing on a track doing a slalom competition with the Dutch MG car club this week and rubbed the corners of my front tyres of cause of enormous understeer. I'm driving a (standard) Rover engined mgb roadster with 3/4 AR bar in the front and 185-14 tyres. Tyre pressure front first 2.3 and later 2.0 bar did not make any difference. Looking for simple tricks to improve this, any idea's??
|Increase rear spring rate or shock, add rear sway bar.|
Do one at the time, or reduce front swar bar size.
It all depends how much the car leans, car should lean about 1 to 2 degrees. If tires are sticky then you will need heavier springs all the way around and adjust with sway bars and tire pressures.
|Try 7/8" front anti roll bar, lowering car, 15" wheels with 55 profile tyres.|
|Heavier bar at front will increase understeer, you would want to loosen the car in the rear to induce oversteer (controlled)|
Try some neg camber say 1.5deg, if also being used as a road car.
|Go with Bills advice to start - but try the front bar you already have with the rear bar first - |
there is a 15" SAAB wheel which fits and will allow you to use 195 X 55 tyres - they will help a little too.
At this place you will find nice explanations on what to do.
In my case, i have to reduce the front sway bar size.
|I run the stock front and rear bar (79) and the car is very well balanced. Nice 4 wheel drifts.:)|
1979/ Rover 3.5,TR7 5spd.
|thank you for all your comments, |
my b V8 is a lowered RB, creating a bit negative camber already. Wuold it help to uprate the rear (standard) shock's?? Car proved to be very well balanced on an other track with wider corners, looking for small improvements for this sharp edeged track.
|It's all a a matter of taste, but for really tight situations where you are in low gear, I would be looking at a really soft rear end, to provoke a bit of oversteer. If you have an anti roll bar at the back, try removing it.|
|check with your local club racers & see how they set up their cars. In the U.S., that would be SCCA participants. Their experience shold translate pretty directly to your car. Just because you have more HP doesn't change the handling through the corners. Best advice I have gotten is bigger front sway bar, softer rear suspension- soft rear springs, stock rear shocks.|
Negative camber wishbones from Moss make a big improvement.
As your car is a lowered rubber bumper car the first thing I would check is are the lower wishbones parallel with the road surface? If they are not and are sloping up towards the outer end this could upset the geometry of the suspension and with a bit of body roll in a corner or in tight turn situation such as a slalom course the supension may well go to positive which could cause the outer edge of the tyre to scrub.
If this is happening you will need to increase the ride height and/or add in some more negative camber. Moss and Beehive sell a negative camber lower wishbone set. I would also invest in a set of adjustable telscopic rear dampers(shock absorbers) and for slalom courses try running the rear a little stiffer/harder, this will tend to reduce understeer and increase oversteer and allow the car to turn and respond to the steering a lot quicker, this is basicly the reverse of what track racers do, they tend to run the front stiff with negative camber and the back soft which gives a reasonable balance and good traction out of the corners. It's all down to what you want the car to do.
My lower wishbones are indeed slooping up, I would say about 1 to 1.5 cm, So what you say makes sence to me. What is the best way to increase the ride height at the front, buy new springs, or are there others ways??
Did you buy the car already converted and if so can you contact the previous owner to find out what springs he used ie, length and spring rate. You could also measure the ride height between chrome strip to centre of wheel then put trolley jacks under the front crossmenber and measure again when you have got the lower wishbones level with the ground. this would give you a reasonbly accurate measurement re how much you need to raise the ride height.
My car is a GT so not sure which springs you would need to achieve the desired result, the standard GTV8 springs might be a good place to start, Also worth checking the rear ride height to see if the car is sitting level, there are others who can give you more accurate advice re suitable springs, but be wary of advice from some suppliers whose products do not always give the desired result especially with the rear leaf springs.
Hope I have been of help.
I have checked the Moss catalogue, this gives a road uprated front spring at 480 lb/inch with a ride height of 35cm. They also do a road lowered at 550lbs/inch with a ride height of 33.5cm. these i feel would be too hard for anything but racing although they do an even harder spring rated at 660lbs/inch ride height 32cm. See how these compare to what you have.
I did the conversion myself and finished some 3 years ago.
Bought the lowering kit second hand from a guy who stopped in the conversion planning phase, so don't know who supplied it and what the spec's are. My height at the moment is about 33,5 cm front and 38 cm rear but it is lower then after finishing the job as my jack fitted underneath the front crossmember at that time and now I have to lift my car to get it under there. Assume the springs got shorter. Im my opinion a front height of 35 cm would be nice and put my wishbone arms downwards again. The springs you found in the Moss catalogue are they for rubber bumper B's??
Do you still have RBs?
For road I use 550lb for roadster (CB 1in lowered) and 600lb work well with GT.
Tim Fenna at Frontline should be able to spec springs specific to your needs, also may have adjustable camber kit, or try Doug Smith at MG motorsport.
Is your car roadster or GT, are the rubber bumpers still fitted, and is the car used mainly on the road,
daily driver or weekend fun use only?
Once we we know the usage of the car we can better advise.
My car is a roadster, has no bumpers but a Sebring front and rear valance, so does not carry the wieght of the RB's. The car is a fun weekend car onley, but mainly driven on the road.
|Also try staggering your tire pressures front to rear. It's been a long time since I resorted to this so I've forgotten which way to go with it but you can easily go as high as 50 psi and as low as 10 and this is a good way to fine tune the handling if it is otherwise generally neutral. That plus braking hard entering the turns to allow heavy accelleration exiting will allow you to use throttle induced oversteer to correct, and the MGB is rather prone to braking induced oversteer as well which can be used to tremendous advantage on hairpins. I once cut the one minute autocross lap time by ten seconds using this tecnique in a stock MGB.|
The front springs for a rubber bumper roadster are Number AHT21 and are rated at 480Lb/ins and give a ride height of 35cm.and are recommended for fast road use. They also sell 5mm. spacers that go between the spring and the spring pan and or the top of the spring and the crossmember maximum of two per side,so you could raise the car another 1cm. if required or use them to get the car absolutely level.
I would do this as a starting point as it would
appear that your current springs may have sagged/drooped. If you are still running lever arms on the back I would then think about getting some decent adjustable telescopic dampers to give you some tuneability, try running them hard as suggested when you are doing a slalom or autotest, this should give you the turn in you need. Don't forget to loosen them off before you go back on the road or you have a rather tail happy car. I presume you still have the rear anti roll bar and I would leave that in place for the moment.
My GT has the Hopkinson lowering Kit, it is very well balanced with the rear anti-roll bar and can be nicely controlled on the throttle! I did my handling test in a damp and empty car park after I did the engine conversion, did not want any nasty surprises on wet roundabouts, not sure you have those in Holland. Where are you based? I have been to Holland a couple of times many years ago and was made very welcome.
This thread was discussed between 07/05/2005 and 24/05/2005
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