Fuel Tank for Sprints n Hills

[Kevin Jones]

As you know I am far from an expert here but in the absence of real one here is my take. If you want to continue without ARBs then all you have to play with is spring rates. The harewood pic looks to me like you have the loaded front in +ve camber or very close to, that will not help front end grip particularly on radials, adding some more -ve camber might help a bit or you have to address the roll issue.

The only way to deal with the roll will be stiffer springs but you can't just add  to the front as that will add more understeer. You have to match front & rear. This might cause you to lose compliance and hence some traction, it's a compromise without the ARBs and each change requires new springs although you can in theory calculate approximately good pairs.

Can't really help on why the handling changed so much, the problem is that static weight does not really tell you much about  dynamic conditions, so something else may be at play to create the understeer.

[John Loudon - Sponsorship Liaison]

It is difficult to comment without seeing a front on shot of your front suspension geometry and knowing what springs you are currently running

[Kevin Jones]

Not front end, but did see this.

[stephenh]

That looks like an aweful lot of roll fo somethng as low and light as a Westie with a bike engine! That said, it is what is happening to the front outside corner that matters most here, so unfortunately other than the amount of roll I suspect the photo wont help the experts comment much more than already? Because of the amount of roll, it is inevitable that the inside front wheel is changing to (or towards) positive camber.

[John Loudon - Sponsorship Liaison]

That photo looks like you need to transfer some more weight to the front inner wheel. The ideal way is via ARBs, but you could try upping the rear springs rate by 25-50 lb

Without knowing what you already have its a guessing game - do you know wht you have?

[Bones]

One of the front here.

[John Loudon - Sponsorship Liaison]

That photo not only shows roll but also looks like a fair amount of bump steer

Cant comment any further without knowing what is already fitted

[a4gom]

haven't checked them but I was told by the previous owner 300lb front, 200lb rear

there are some pics of the roll front on from harewood but the trouble is playskool have changed the settings since harewood so even though it's not really made any difference to the way it handles it may not give a true reflection, not sure if there are any pics front on from curborough but thats how its set up now.

John how remind me how to measure bump steer, I had some notes when I made the front suspension on my previous car but I can't find them now.

[Tigger]

Anyways, back on topic, I have a 2 gallon which is foam filled and does a double lapper at pembrey only only have of it!

Can't do any track days though so it depends on what you want it for as mentioned

Tiggs

[John Loudon - Sponsorship Liaison]

How much understeer are we talking here? Those springs arent far away - perhaps a touch stiff for standard track but not too much. If it was OK with the x/f in it with those springs then it reasons that the fronts are a touch stiff with a lighter engine. - perhaps 250lb would be worh a shot

[a4gom]

hey up the police are here! perhaps we should have started another thread  

Tigger I'll let you know I've already had one similar offered but i'm not sure how I'm going to proceed yet

Far too much John, I'd considered reducing the spring rates  but when i've discussed it with others in the paddock they are using 375 fronts, they have arb but how much difference does that make?

add some narrow arbs to th wanted list!

[Matt Seabrook]

I have a 15l tank and find this will do track days and sprints.

[Blatman]

but when i've discussed it with others in the paddock they are using 375 fronts, they have arb but how much difference does that make?

Impossible to answer without knowing what the rears were for those guys.

I agree with John. If the springs at either end haven't been changed since ditching the x-flow for a bike engine, then the front is likely to be too stiff. At 200lb/in, the rears seem a bit on the stiff side too.

I'm also a little dubious about the plan to move the tank from the rear of the car to the passenger footwell. Even with a relatively large capacity tank, the front weight increase is going to be negligible because the tank is still a long way away from the front end, and you'll only be adding what, 10 litres of fuel, which is less than 10Kg's in weight, plus the weight of the tank and fitting parts, so say an extra 15Kg's all up. I'd get the car on the scales again and see what difference adding 15Kg's makes to the weight distribution *before* spending a load of cash and finding out *after* that it's made sod all difference...

[Kevin Jones]

they have arb but how much difference does that make?

A lot from what I can work out, your ARB, if you have one, can be strong enough to make springs rates fairly uninteresting as far as roll resistance goes.

Another thought though, perhaps we are missing the obvious, with the R1 you have more grunt/lower weight and so likely higher g around the bends. This will naturally push more weight to the front in a corner and create understeer compared to the xflow on an identical setup. Same fix though lower front rate or increase rear.

Or in short, drive a bit slower and all will be fine, that's what I tell Paul when he complains  

[a4gom]

here's one from the front on Sunday

does anyone make arb's specifically for narrow bodied cars? (independent rear end)