Autocrossing in the USA...

[KWM338R]

Went autocrossing with the Porsche club at the weekend and had a blast in the old Dolly! Did ok for a first time out in it, ended up 4 seconds behind my friend in his Boxster over a 45-50 second course, which I thought was pretty good considering.<br>
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Anyway, the car suffered from bad understeer, I'm using road tyres with 30psi front and 32psi rear. any advice on tyre pressures? also my car sits slightly higher at the rear than the front, I was unable to drop the rear at the event due to rusted spax spring adjusters. I'm assuming if I can lower it a bit at the back it will help my understeer problem, any advice will be appreciated.<br>
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cheers<br>
<br>
Mark

<p>1979 Dolomite Sprint<br>
1972 TR6 (In its component form)<br>
1993 Mazda Protege ($250 Winter Hack)<br>
2000 Mazda MPV (For Sale)</p><i></i>

[davepoth]

Somewhere or other on the main board, or maybe in the motorsport bit, there was a discussion about this. I think the idea was removing the rear anti-roll bar should cause the car to be a bit more tail happy.

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[Carsreunited]

You definitely need a slightly nose up attitude to help. Only half an inch or so lower at the rear.<br>
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Sounds like you are having some fun!<br>
<br>


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[SMIFTER]

As a non automotive expert but an engineer nonetheless I think the Dolomite has a major flaw in the weight distribution which tends to make the car understeer. <br>
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Look at where the engine is mounted and its well ahead of the front axles, therefore about 2/3 of the engine and gear box assembly (which is a bloody heavy lump of metal at about 200kg ish) generate huge forces that want to go straight on at any corner rather than help the front wheels to grip. Add Braking forces into the equation and the forces get even higher!<br>
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Lowering the back will help to tip the balance but it wont eliminate it as this is a inherent problem in the design of these cars which badly affects front end handling. <br>
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The funny thing is you can drive a Dolomite for years on the road and not notice it. Push it to the limit on a track and my god do you feel it!<br>
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I cant beleive I've written all that whilst being pissed. I;ve read it back and it seems to even make sense!

<p><!--EZCODE LINK START--><a href="http://www.smifter1971.pwp.blueyonder.c ... >Smifter's Dolomite Sprint Website</a><!--EZCODE LINK END--><br>
<br>
1974 Soon to be non Triumph powered Dolomite Sprint to scare myself senseless.<br>
2004 Smart Roadster 80BHP to laugh myself senseless<br>
1997 Audi A4 2.6 to bore myself senseless.</p><i></i>

[2F45T4U]

the weight distribution seems to range any where from 52 front 48 rear to 58 front 42 rear.<br>
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What about ballast weight? I know to go faster adding weight doesnt really help but if your handling improves surely your times will. And whats 2-8% of just under 1000kg. Chuck a body in the boot and see what happens!<br>
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<br>
Adam

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[Mark Larmour]

I agree with Scott. A nose up attitude (of the car, but sometimes it works with the driver as well) will reduce the understeer. Also for Autocross work I would increase the front tyre pressures to 34 psi and drop the rear to 30psi.<br>
Philip

<p><!--EZCODE LINK START--><a href="http://www.sprintparts.triumphowners.com">SPRINTPARTS</a><!--EZCODE LINK END--></p><i></i>

[davepoth]

Just thinking about it, the battery is in front of the axle. I guess you could relocate it to the boot, which would be about 1% weight balance shifted to the back.

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[KWM338R]

thanks gents for your input. will drop the back end some before the next event(if I can undo the spring seats) then play around with tyre pressures. I'm using street tyres so they're far from ideal for autocross, I'm trying to work out how to blag a set of stickies without 'er in doors finding out! oh well I already have two kids so i dont suppose i really need the wedding tackle anymore<!--EZCODE EMOTICON START :lol --><img src=http://www.ezboard.com/intl/aenglish/im ... /laugh.gif ALT=":lol"><!--EZCODE EMOTICON END--> <br>
<br>
Mark

<p>1979 Dolomite Sprint<br>
1972 TR6 (In its component form)<br>
1993 Mazda Protege ($250 Winter Hack)<br>
2000 Mazda MPV (For Sale)</p><i></i>