In message <
[email protected]>
"Pantelis Giamarellos" <
[email protected]> wrote:
> Austin Hi,
>
> I would be very much interested into seeing a few photos of the spacers you
> have made.
>
> Back to the Discovery lift now.
> Lifting a Disco will affect the ability to fit larger tyres which in its
> turn does make some difference in increasing the available space between the
> ground and the differentials and the mechanical bits of the car, increasing
> top speed but sacrificing acceleration and torque on the wheels.
>
> Wider tyres tend to create a positive effect on better braking and
> acceleration and sligthly decrease (contary to common belief) cornering
> performance. This is mainly a concern of road going cars where cornering can
> be done while driving fast without the fear of tipping over.
> On our type of vehicles (off roaders) fitting wider tyres can only have a
> positive effect on muddy tracks and snow when
LRO published a precis of a student from Weast Sussex Universitys'
Phd Thesis that concerned tyre performance off-road - this was about
5 years ago or so.
Simplifying a bit, the result was that in *most* (not all) scenarios,
that "we" are lilely to encounter (i.e. excluding deep soft sand,
very soft deep boggy ground, etc), the tyre needs to dig through
the slippery soft surface to get at the grip underneath.
Guess what the optimal width was.... yep, the same as Rangemasters,
the "ordinary" (now extinct) BF Goodridge, Goodyear G90, SAT's etc -
in short, the types fitted by the British Army.
Having spent a lot of time at the Chobbham test facility and seeing the
amount of testing he Army do, this is no big surprise!
Also interesting was the tread pattern issue. Extrememly open block
tyres fared badly after starting to slip, they just dig a hole quicker
by disloging the very grippy bits the tyre needs to grip,
whereas if the tread is to close mud and stones are not expelled
efficiently. The optimum was not just guess work, but depended
entirely on the philosophy of the designers. Hence Michelin OR's
perform well in slippry mud, despite being a pretty close block
tread, but are abysmal on wet rocky ground as the side walls are too
rigid.
Certainly, having tried various tyres laning and trialling (in
coil and leaf sprung vehicles) and marshalled many events I'd
venture that the Army, and he student, are right - all the winners
of the big inter-club and nationals run on very "average" tyres.
>lower footprint pressure can
> make the difference between grounding your diff and undercarriage and
> getting stuck and effectively continuing to travel without getting stuck.
>
> Larger diameter tyres is a different story from wider ones.
Indeed - the larger the diameter, the bigger "step" a tyre will go
over, in other words obstacles become easier to get over. Couple
this with a softer side wall, and the "average" tyre (that the
vehicle designer had in mind) the the best compromise will be
reached. This ignores road performance, as anyone who has used
Michelin XCL's will know very well!
> tyres with the same width as the smaller diameter ones give more advantages
> when you offroad provided of course that you take some action to compensate
> for the lost torque (actually the need for increased torque output from the
> engine in order to make the same progress while moving and of course the
> increased strain on the transmission's components)
>
All in all, tyres are a compromise, and there is no rule like "bigger
is better" - what you want to do with the tyre is what defines which
tyre you want.
Richard
> Staffbull I HTH
>
> Take care
> Pantelis
>
>
> "Austin Shackles" <[email protected]> wrote in message
> news:[email protected]...
> > On or around Fri, 7 Jan 2005 22:24:25 -0000, "StaffBull"
> > <[email protected]> enlightened us thusly:
> >
> > >Is a 20mm lift all round on a disco going to look OK ? does anyone have a
> > >pic of one with a similar lift?
> > >
> > > I'm not after it looking like the wheels have had a divorce from the
> body
> > >!! 
> > >
> >
> > I spose I could take some pictures of mine, but to be honest, you have to
> > know what you're looking at to spot it. it *does* look higher than the
> > standard one, but only slightly. I guess I could fit something like
> 245/70
> > or maybe 255/70 tyres instead of the 235/70 which are on it at the moment.
> > There's not much point though. I don't think there's enough space to fit
> > 235/85s, I reckon you'd want 2" lift for them really. Dunno how close the
> > tyres get to the body, as standard. 235/85 tyres (which would be the most
> > sensible for increasing axle clearance) are nominally about 1.5" bigger
> than
> > 235/70 or ordinary 205s, and thus would possibly foul the body with "only"
> > 1" lift. They will also maybe reduce your lock a fraction, as they may
> foul
> > the radius arms.
> >
> > Having been there and done that with the 110 (10.5 width "AT" tyres) I
> don't
> > think they give much advantage other than better flotation on soft ground.
> > They don't seem to grip any better on firm slippery going. They *look*
> good
> > (if you like that sort of thing) but they don't actually perform any
> better
> > than the 235 width ones for most purposes. Extra height is a different
> > story - if I wanted a "play" disco, I'd give it 2" lift and fit 235/85 MT
> > tyres...
> >
> >
> > My main objective was not only to lift but to fit stiffer springs - The
> > standard ones roll too much on the road. This probably doesn't do
> anything
> > for rock-crawling ability or ditch-crossing, but I like the way it handles
> > on-road, and since it does at least 95% of it's mileage on road...
> >
> > I actually made spacers for the rear on mine - dunno if anyone sells such.
> > Bought 2 slices of 110mm dia. steel bar, faced 'em on the lathe (no doubt
> > unnecessarily, I also made a reduced diameter to locate the middle of the
> > spring seat, which is also unnecessary - the plate on the axle doesn't
> have
> > one) and drilled 2 holes, longer bolts through the bottom spring
> > retainer/seat and robert's yer father's brother.
> >
> >
> > --
> > Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
> > "The great masses of the people ... will more easily fall victims to
> > a great lie than to a small one" Adolf Hitler (1889 - 1945)
> > from Mein Kampf, Ch 10
>
>
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