New owner

[john m]

Good to see people like the fun factor, the beauty of the Beat is you can have great fun at relatively low speeds. If you over tyre the car that will change, the car will grip and look better on big wheels but I doubt it will give the same fun at low speeds. I think the term "Midship Amusement" describes the car perfectly! I had terrible problems trying to get a matching set of 13"/14" before I got alloys, you guys in the UK have a greater variety of cars (certainly much larger numbers of unusual cars like the Beat) and hence the better availability of unusual tyre sizes.

[JEP]

Just got back from having the original wheels and tyres fitted, what a difference.
On the old bulky wheels it was an ok drive but nothing to write home about. Now it's a different car , faster on acceleration and so much fun in the corners.
I spend most of my time at work driving fast cars very fast, stressful but not fun.
Now driving a relatively slow car on it's limit wow fun fun fun.
James

[tinytim]

I may use my 4 stud 106 wheels if I can get spacers made up.

This will be fine off the road but depending on the rim width of your 106 wheels you may find they protrude from your arches.

I have a set of 6" rims and need a 20mm spacer on the rear with a 25 on the front but this will obviously depend on the offset of your 106 rims

Fitting extended studs is not as easy as it could be either, you have to strip the hub for starters cos there's not enough clearence to remove the stud. Then, unless you know somewhere who can provide the right size stud you will have to drill your hubs out to fit the ford stud (M12x1.5 I think).

If you want to go ahead you can get everything you need from http://www.trackstore.co.uk/wspacers.html
amongst many others but they did OK for me.

[Jennifer]

im not sure yet may import some rays engineering ones near the time if I can get hold of some. But the 106 wheels are there If I need them

[Bruce]

As I noted earlier, there is a tendency for more of a kick from the steering wheel with wider front wheels, and this spacer you speak of is what is causing it. Here's why:

Have a look at the right-hand diagram I have attached. The force from the tyre can be assumed to act in the centre of the tyre's contact patch width, so, with wider tyres, you will need a spacer to stop the tyres touching the chassis. Therefore the tyre's force centre is moved further away from the point where the steering axis (the dotted line) touches the ground. So the 'scrub radius' becomes positively long. So if the tyre hits a pothole, the tyre is dragged backwards, and that extra scrub radius gives the dragging force longer leverage, so additional torque is applied to the steering wheel by the bump.

You might say that you like the feedback, that it helps you tell what is going on. Maybe it might tell you a bit, but what you are really interested in is when the tyre is about to slide as you corner hard.

Now look at the left-hand diagram. From this side view of the tyre,the sideways force from the tyre's contact patch actually tends to be concentrated near the rear of the patch. However, when the tyre has almost reached its cornering limit, this concentration point actually moves forward due to the tyre fundamentally changing its behaviour just prior to sliding. This shortens the 'phenatic trail', which one adds to the permanently fixed 'mechanical trail' to find the length of leverage the tyre's sideways force uses to exert torque on the steering wheel. This torque is always trying to centre the steering wheel, but you will notice that the steering goes light when you are about to slide, and it is this shortening of the 'pneumatic trail' that causes this.

If your steering wheel is getting knocked about all the time, it will be difficult to sense this subtle lightening of the steering wheel.

Anyway, I just thought you might want to know!

If you look at a Porsche's or the occasional Mitsubishi Evo I think, you will see that they have tried to get the wheel so deeply onto the hub to reduce the scrub radius, that they have sculpted the wheel spokes so that they bulge around the brake caliper with just 1 mm clearance all along the spoke's length - very swish engineering. So it pains me to see boy racers adding inches to this gap on their cars.

Bruce

[JEP]

Very technical, I think I understand it all.
I have always thought that the car manufacturers do not choose the wheel/tyre size on a whim and that hundreds of hours have gone into designing such things.
I fail to understand the current trend of making a car look good!!! With no thought of performance.
The other day I was talking to an inexperienced driver in his saxo with tyres big enough for F1 and an exhaust you could drive your Beat into, not to mention more neon’s than Blackpool prom. He had just wrapped his car around a tree. Gone into a corner too fast and didn't know what to do. The tyres got to a point where they just let go and catapulted him through the hedge. He thought that when he got to the limit of his grip it would be just like Top Gear and he would slide sideways around the corner.
Big fat tyres do not give any feedback you just feel every bump and cat’s-eye in the road. There is nothing better to teach you how to drive than some tuition on a track where you can safely drive a car to the limit and beyond and see what happens and how to control it. It is certainly money well spent and an experience not easily forgotten.
James

[JGGIB]

you are talking sense there jep ,as I said earlier Honda must have spent millions developing the car.

[Paul w]

Nice!

Now, please go on to explain why wider tyres cause the wheels to 'tramline' on white lines? And while your at it, why do fat tyres cause you to hunt the crown of the road?



PW

[Adam]

In my opinion the standard setup is great. I'll say it again, great, in the dry!

Once the rain falls all the theory changes, roads become like ice rings when cornering at high speeds. I tried many tyres with the original setup and they were all great until it rained. I did't feel safe at all.

Now I have 185 on the back and 165 on the front. I am not saying that this is the best setup or that I took out a calculator to get this but at least when I take a corner I know I won't end up on a wall.

Because the car is so light any bump on the road sets it flying in the air so in my opinion the more rubber on the ground the better. To a limit of course.

[Adam]

As for the saxo boy racer. His car handles like a boat, its front wheel drive, and his center gravity is way up there.

Those cars are way too high and not designed to corner at high speeds. So it doesent matter how much rubber he has, the car can physicly topple over.

I've driven the beat on the track and most cars could take me over on the straight but when we hit the corner they had to say bye bye.

[Jennifer]

Sod it I will just get some Rays engineering wheels imported 15 on the rear and 14 ont he front best compromise I think

[tinytim]

All good points individually Bruce but it's not (or shouldn't be) just a case of fitting wider wheels. The scrub angle can be maintained by varying the wheel diameter and the "assumption" that the force is acting on the centre of the wheel is only valid for static calcs. On cornering the chassis dips or rises, this action moves the point of force, hence active suspension development.

However, when the tyre has almost reached its cornering limit, this concentration point actually moves forward due to the tyre fundamentally changing its behaviour just prior to sliding

I can't say as I understand the "change in behavoir", the tyre is doing exactly as it should, providing a frictional contact with the road. As sideways forces increase so weight transfers through the chassis to provide more down force on the outside wheel, the tyre will deform giving a flat spot that has the effect you describe. As friction is lost the tyre wall re-exerts itself allowing a momentary regain of friction, this is the "warning" that is lost as boy racer drops the tyre profile (lower wall = less deformation = less chance of regaining friction).

Interesting point on varing trail I must have missed a lesson or two. I had always assumed the steering went light as a result of the loss of friction but what you say make things crystal clear.

Does anyone know what the castor angle is on the Beat?

[Midship]

Just came across this thread.. Some interesting stuff here just thought id add my 2cent...

In my opinion.. The original 13"/14" combination is not for me, heres why....

The size difference coupled with the different tyre width and profile is clearly set up to induce understeer.

This set-up was... in my opinion anyhow, created by Honda to make this Midship car more predictable and controllable for your average daily driver.

Personally ive had enough of this understeer and am of the opinion that 14" wheels all round with the same tyre profile all round are the only way to go.

Look at the MR2, ok its got more power but theirs no silly bigger rim and massive tyre difference, that’s a fellow Midship car and I like the way it handles.

Thus I have purchased 14" rims and when I stop spending all my money on the cappuccino im off to buy a sandblaster to refurbish them. Initially trying 165/60/14 (maybe 175/60/14) on the rear and 165/60/14 on the front.

Different tyre/wheel combinations will give different results; everyone has their own preference, if you like predictable understeer the standard set up is for you.

However im perusing a more neutral beat i.e with less understeer... Suspension will have to be change at some stage when cash permits but until then all I can do is play around with tyre combinations.

[tinytim]

I'm with you on this Midship. I'm none too sure of the original set up and will say the book tyre pressure is wrong for starters. I think it's highly unlikely Honda made a mistake but perhaps they were aiming at a different use. I'm going on a 15" rim but a lower profile so it's only 3mm bigger than the rear original but all the same size. I figure i need to drop the front end more to keep the bloomin' thing on the ground but also to keep close to the original scrub angle. It's only a little steering wheel and I'm a lazy git .

[Bruce]

Very interesting to read your responses. They got me thinking. Here goes nothing:

Wide tyres are not too bad in themselves, if they are fitted to a car with enough room for them to turn within the arches (easy), a low Centre of Gravity (CoG) relative to vehicle width, and suspension which copes well with body roll. They also need to be related to the mass of the car, because the average pressure acting on the ground is car mass/total contact patch area, so it's not ideal to go crazily wide for that reason either, otherwise the microscopic peaks and troughs of the tyre and road surfaces will not mesh quite so tightly.

That being said, very wide tyres fundamentally tend to aquaplane at high speeds on standing water, even when going in a straight line, and due to the low surface pressure, just cannot dig into snow.

The good suspension I spoke of ensures that, when cornering, the outside tyres (which due to weight transfer are the ones doing most of the work) are at 90 degrees to the road, even if the car body is rolling. If this is the case, you *can* reasonably assume that the force centre is acting in the middle of the contact patch's width. I think so, anyway.

I will elaborate on the tyre's change in behaviour when you start to slide. Before this point, in gradual cornering, the contact patch, and its direction of travel, is 'twisted' relative to the axis of the wheel. This twist angle increases fairly proportionally to lateral force generated by the tyre, in an 'elastic' manner. When the limit is reached, I think the twist angle becomes less relevant, and the tyre purely relies on mechanical friction to provide lateral force, which it succeeds in doing a little, until the car is so sideways it just gives up. Sadly, I can't remember why this transition changes the length of the 'pneumatic trail'.
Tyre pressure has a lot of control of these characteristics. High pressure will mean the lateral force builds up to its peak for a lower angle of twist, giving more responsive handling, but a low pressure, large contact patch will increase the peak force capability. I guess wide tyres would – theoretically - do the latter, and tyres with shallow sidewalls will achieve the former. Although the standard Beat tyres sound like they have deep sidewalls, with profiles of 65 and 60, remember the profile is measured relative to the width, so in fact, the tyre walls aren’t as high as they sound, so are probably responsive enough already.

Going back to tyre pressure, in racing, it generally ought to be set so that the temperature is even across the patch's width - not too high in the middle (too high a pressure) and not too high at the edges (too low a pressure).

Unsprung Mass

Interesting what Adam said about the tyres jumping off the ground over bumps. ‘Road holding’ is the least understood term in motoring. Technically, it means the individual tyre's ability to stay attached to the road even if it is bumpy. The way to achieve this is to have good, low friction suspension, particularly the dampers (shock absorbers) for fluid, high fidelity wheel movement. Another way is to have low unsprung weight, particularly relative to your sprung weight. The Beat's body, engine etc is the sprung weight and is obviously pretty light, and the wheel, tyre, brakes, and half of the suspension is unsprung (though the tyre's air helps a bit as a highly underdamped spring). So putting big heavy wheels and tyres on the Beat will tend to increase the unsprung mass, so they leave the ground regularly, like Adam's wide 165 and 185s! Though I must admit, I find my 155s and 165s do this too, which has alarmed me once or twice. Maybe the Honda pepperpot alloys are a bit too heavy. Or perhaps the stock dampers have too much friction. Has anyone uprated their dampers and found this helps the road holding? Or has anyone found any lightweight wheels in the standard size?

Camber and Caster

I don't know what the caster angle is, but it seems reasonably high, as the tyres develop quite a bit of negative camber when parked with the steering on full lock. This is another reason not to mess with widening tyres - they really don't like too much camber, as they start riding on the tyre's edge, which has negligible contact patch area. My old Citroen 2CV’s steering had very steep caster, so built up loads of camber when steered – it could take advantage of this, as it had even narrower tyres - 135's I think, so a bit like motorbike tyres. Now there was a driver's car! I'm glad I survived, looking back...

That's another disaster for the boy racers. They also lower suspension, which raises the tyres. The suspension will be designed to gain negative camber when this happens, so that the outside tyres' contact patches stay flat under hard cornering conditions. (Best start reading this post again if you've forgotten about this bit!) So this means they have this negative camber all the time. On wide tyres. Then they hit the brakes, and the tyres move further up, so even more camber, then they hit a bump, hit the suspension's hard bump stops, and suddenly they have no suspension travel left, losing all grip at that end of the car. Oh dear...

Incidentally, the boy racers won't like to hear that the positive effect on cornering grip that the right amount (a little bit) of negative camber on the outside tyre tends to diminish as you get closer to the optimium tyre slip angle for peak lateral force (although the negative effects of positive camber get disproportionately worse).

That's enough ranting for now. Hope you enjoyed it.

As for the tramlining and hunting with wide tyres, I don't know, but would love to find out. The handling characteristics sound like too much toe-out at the front, but that's a different story...

In summary, I’d like your experiences of the effects on road holding of lightweight wheels of standard size, and uprated dampers. And why do wide tyres tramilne?

Bruce

[tinytim]

Wide tyres are not too bad in themselves, if they are fitted to a

car with enough room for them to turn within the arches (easy),

Check!

a low Centre of Gravity (CoG) relative to vehicle width,

Check!

and suspension which copes well with body roll.

Check!

They also need to be related to the mass of the car, because the average pressure acting on the ground is car mass/total contact patch area,

Now on this I have to raise the question of what area has to do with friction? The answer is nothing, friction is the product of force and the coeficient of friction of the materials. So why is the contact patch area a factor?
The meshing theory is somewhat flawed and is easily countered with probability. A larger contact area gives a higher probability of a small patch of GOOD contact. (Size of patch is unimpotrant)
Aquaplaning agreed but we are talking standing water not just wet roads.

[Bruce]

I should have qualified that 1st statement by adding that it is unlikely that there is ample space already available in a given wheel arch for significant tyre widening from standard sizes, so that is why you often need to add spacers, which leads to problem I mentioned in my previous post of extra offset giving more 'kick' in the steering. It was the mention of spacers which started me off in this thread.

I haven't seen a Beat cornering hard from the outside, so I don't know how well the McPherson struts keep the outside wheel vertical. I really must rig up my camcorder to take a close look...

The car certainly rolls a bit, due to a combination of narrow track width and perhaps a low roll centre resulting from flat lower wishbones. It is the distance between the roll centre and the car's CoGravity that produces roll.

As for the pressure and the peaks and troughs, well, I am not quite so sure about that topic than the others to be honest. Sorry about that. I think it may be true, but only if you take it to crazy extremes, like F1-sized tyres on a Beat... But I do know that coefficient of friction is a simplification - tyres in particular are more complex than that. It is *not* an absolute figure. For a start, you get an increase in the coefficient when you have a low vertical tyre load. That's why the Beat and Elise corners well, and also why the low weight transfer from a low centre of gravity allows all 4 tyres to work optimally, aiding cornering acceleration.

Bruce

[ozsamurai]

Sorry to be extremely late in the greetings, welcome to Beat Heaven, Oz here! I really don't want to get into the arguments over tyre widths at the moment, since I defied all of them with my last set..... but I did want to make a comment for you on the original question about the back window, although it has been answered to death! The manual does state that you have to unzip the window before opening the top, HOWEVER, experience and usage dictates that in most cases it is not needed, but and there is always a but, whether you unzip or not, the inner side of the screen is going to contact with the carpet on the back parcel shelf and this tends to agrind tiny little scratches into the bottom half of the plastic which over time becomes opaque. To counter this, here in Japan, all Beat owner have a 'Beat Towel' (mine was a Union Jack' just for you guys!'. The Beat towel is the multi purpose, all weather Beat driver companion, usages include;

1) placing on said parcel shelf or in the fold of the windscreen to prevent rubbing/scratching from the soft top or carpet
2) mopping up of seats/carpet after the rain has poured in form the leak in the soft top.
3) Seat bolster protector
4) Dry surface for a passenger to sit on when their side leaks too.

Essentially, to maximize the usage of the rear screen a very soft towel is the way to go. Hope this little tidbit helps.

Cheers
Oz