Mid engined Kit cars for the road

[MR2 Jon]

Just wondered if people feel that snap oversteer could be a problem when driving mid engined kit cars in unideal road conditions i.e. the wet or a road with lose stones etc.

I'm interested in buying a Riot but, for this reason, am just wondering if a 7 style car would be a safer option.

Thanks

Edited by MR2 Jon on Tuesday 20th April 01:17

[Paul Drawmer]

Do you drive an MR2?

[NeilE]

I drive a Mojo (so very similar chassis to a Riot) all year round, tend to take it a bit easier in the wet, but never had any major snap oversteer problems on the road, in over 30k miles!

I have driven on track in the wet and was pleasantly surprised at how it behaved on the limit. I found that a change to softer springing made it much more progressive at the limit too. Loads of stuff on my website if you want a read...

www.mymojo.co.uk

Cheers,

Neil

[MR2 Jon]

Cheers Neil, that sounds promising. I'll have a read through the site now.

@Paul I owned an NA then Turbo a couple of years ago. They (IMHO) were a bit to prone to snap oversteer in the wet which is what prompted me to ask this question.

[Fat Arnie]

Having owned a Seven which was undrivable at any progressive pace in the wet, I think its a bit of a subjective comment.

Sure MR2's have a dreadful reputaion for spinning in a manner which is unrecoverable, but this phenomina occurs wet or dry.

A Seven is a tricky beast in the wet, but will be much better with less power (under 200bhp) good tyre choice, a less ferrocius LSD, and soft springing. The more powerful and peaky, the harder they are to drive. A good example is
Mid engine will probably be better as there is more weight over the driving wheels. Perhaps this is why rear engined cars such as a well set up 911 are so good.

Worth noting the Elise is much better in the wet than an equivalently powered Caterham. (subject to both being if properly set up). The extra weight the Elise has helps it get the tyres warm. In the wet it is very hard to get any decent heat in a Caterhams tyres unless you are running proper wets.

[NeilE]

Good points, Arnie. The Mojo is indeed great for traction off the line, wet or dry.

[Sam_68]

Fat Arnie said:

...The extra weight the Elise has helps it get the tyres warm. In the wet it is very hard to get any decent heat in a Caterhams tyres unless you are running proper wets.

Tyre heat is quite simply not a significant factor for road use, in the wet. You will never get enough heat into the tyre to make any sort of difference to the rubber's coefficient of friction compared to flat cold.

The extra weight of the Elise helps it simply because it helps the tyre push down though the film of water into firmer contact with the tarmac.

It's a different matter for racing wets (which do heat up enough to make a worthwhile difference to the coefficient of friction, even when being continually cooled by a film of water), but if you tried running such a tyre on the road every day (or, indeed, on a dry circuit), it would overheat dramatically in no time flat.

It's fair to say that some mid engined cars (not all) have a fairly sharp transition from understeer to oversteer, either due to application of power or weight transfer if you lift off the throttle mid bend, and that will certainly be more pronounced in the wet. The Mk 1 Elise is certainly every bit as tricky in this respect as the MR2, but tended (on average) to be driven by more enthusiastic and hence more competent drivers. I haven't driven a Riot yet, but as a light car with a tranverse mid engine (low polar moment, high, rearward biased CoG), I'd be inclined to exercise due caution in the wet.

The trick is to learn to use the pedal on the right properly.

[JonRB]

MR2 Jon said:

Just wondered if people feel that snap oversteer could be a problem when driving mid engined kit cars in unideal road conditions i.e. the wet or a road with lose stones etc.

I'm interested in buying a Riot but, for this reason, am just wondering if a 7 style car would be a safer option.

Um, you do realise that a 7 is also mid engined? It's just front-mid engined rather than rear-mid engined.

[Sam_68]

JonRB said:

Um, you do realise that a 7 is also mid engined? It's just front-mid engined rather than rear-mid engined.

True enough... though as a general rule the polar moment of rear mid-engined cars is a little lower (hence they spin easier) and the concentration of the high level major masses at the back (driver torso/head and engine block/cylinder head) is greater, worsening the weight transfer characteristics.

[MR2 Jon]

A big thanks for all the replies, they made some very interesting reading. So the general consensus seems to be that mid-rear engined car tend have a little more traction but are slightly more prone to snap oversteer due to a lower polar moment of inertia but are generally fine for road use given adequate driver skill.

@Jon Yes, I suppose a 7 car is also technically mid engined although I was exclusively referring to rear mid engined for the reasons that Sam stated.

[funwithrevs]

I think as someone who drives one of the most infamous cars in terms of handling, I just feel I should say:

Don't drive like a twunt in the wet.