Tires & rain

[larry9]

I mentioned in another thread that I change tires at 50% tread depth due to my own perception of safety riding in the rain.
My job takes me to Firestone/Bridgstone, Goodyear, General, and a few other tire manufactures and I get to query the engineers on several subjects one being the tires responsiveness in the rain as related to scooter and motorcycle operation.
What they tell me is that a motorcycle tire will displace water at a designed volume when the tire is new, but at a decreasing volume as the tire wears down and this is directly proportional to the tires tread depth - makes sence doesn't it. But they also say that when the tire has 50% or less depth left, it cannot displace enough water for even normal operational situations, such as braking hard or turning quickly.
This is why a worn tire will lock up even under light braking conditions, and slip/slide easily in the rain.
It is also dependent on the amount of water present and to some extent the weight of the scoot/motorcycle.

Thats why I change tires when the depth is 50%.

[scooterollie]

larry9;
Interesting! On a two-wheeled vehicle, you want the best available traction. Any feedback as to brands and performance in the wet?

[larry9]

I don't think there has been any studies by independent companies compairing brands of motorcycle/scooter tires. Each individual company does its own research on wet performance, but they wont give you or me the data for fear we would compaire it with other companies and giving them an unfavorable rating.
The only way to get some data is usually here at the forums. Ask the members which brand they think is best. But that is personally subjective and not very accurate.
Now if you want a recommendation on car tires, I have some data on them, but not mc/scooter tires.

[dwestmodesto]

There are several factors that will effect your tires perfomance in the rain. Tread design and depth is one. Othe factors of equal importance are hardness of the rubber compound the tire is made of, air pressure in the tire, and the tires profile. My scooter is from India. Tires were designed there with a very hard rubber compound for long life. There was little concern for traction for high speed. In India people ride to get the most mileage from the fuel, not the most performance from the scooter. The harder the rubber compound, the longer the tire will last, but the less traction in cornering and in wet riding. My stock tires feel fine in normal riding, but the first time I rode them in light rain I found they slipped quite easily, I went sideways on a traffic circle in light rain. Changing the air pressure in your tires will make a large difference in traction. You get the best fuel mileage with a high pressure in your tires....high pressure makes a smaller contact patch and less rolling resistance, but also less traction, lower pressure makes a larger contact patch, more rolling resistance and more traction. I took an bmw offroad riding clinic with Jim Hyde of Rawhyde Adventures aimed at owners of the big bmw adventure cycles. The first thing he did with all of us was to have us drop our tire pressure down from the 36-38 lbs that my bmw uses on the road to about 20lbs for gravel roads, and dirt and sand trails. Handling and control through gravel/sand/rocks immediately was much improved. With the lower pressure, you can't ride at high speeds, but the benefits of increased control are nice. On the beemer I keep a 12v air pump in my luggage and can adjust tire pressure when riding conditions change. With a scooter I wouldn't drop the pressure as drasticly as you do for offroad riding, but if I was going to be in wet conditions I might drop my pressure 4 or 5 lbs front and back.
Just moving away from stock tires to a high quality aftermarket tire will make a world of differnce for most scooters.
hasta,
Dave

larry9 said:

I don't think there has been any studies by independent companies compairing brands of motorcycle/scooter tires. Each individual company does its own research on wet performance, but they wont give you or me the data for fear we would compaire it with other companies and giving them an unfavorable rating.
The only way to get some data is usually here at the forums. Ask the members which brand they think is best. But that is personally subjective and not very accurate.
Now if you want a recommendation on car tires, I have some data on them, but not mc/scooter tires.

[larry9]

Reducing the tire pressure for riding in the rain may not be the best way to go as the increased tire patch or contact area, is increased. This will promote hydroplaning, since the contact area is larger it sees more water and hydroplanes sooner. However, with more air pressure in the tires, the contact area is smaller and hydroplaning threshold speed is increased. Thats why the tire manufacturers are making most tire profile round (for motorcycles and scooters), to further diminish the tire contact if and when the rider encounters water on the road.

[Dennis D]

If you're running with high tire pressures for maximum fuel economy, you don't have the contact patch the tire was designed for, and wet or dry, you will reach the limits of adhesion to the pavement sooner. Most chinese scoots come with recommendations higher than what is recommended for scooters of similiar weight, wheelbase, and tire size built by european or japanese companies. Recommended pressures right at, or frequently even over the maximum tire pressures on the tires are usually more than optimal for good handling wet or dry.

However, I absolutely wouldn't recommend either decreasing or increasing tire pressure for running in the rain. (But gravel is decidedly different and I would drop pressures and speed if I had to ride quite a ways on gravel.) I would however encourage everyone to find out what the best tire pressures are for the best (shortest) braking distances and fairly brisk cornering. If you say you never corner hard.... what if something happens and your best option is an evasive maneuver other than braking? You don't want to wait til then to find out that you have a poor handling scoot that slides out from underneath you sooner than what it would if your tires weren't either so hard or so soft that you've got an overly skittish or squirrely handling scoot. Whatever works best and is safest for dry handling should also be very close to optimal for rain, although depending on tire design and how your tread diverts water away, your grip generally won't be at anywhere near close wet, to what it is dry. There are a few exceptions, at least for motorcycles, but I don't know if those tire compunds and treads are even available in most scooter sizes. I certainly will be looking at that when it comes time to replace tires, but will probably have to look at motorcycle tire reviews and then see if any of the the best tires are available in scooter sizes. From the few searches I've done so far looking for tire performance info, no one in the scooter world seems to conduct performance tests anything like what the motorcycle magazines do. It's been a while for me, since I've routinely and actively perused motorcycle mags. Maybe someone here who has one foot in both worlds can tell us whether the top rated tires(and I'm not talking ad copy or advertising hype) for motorcycles are available in sizes for scooters.

[Dennis D]

Quote- Thats why the tire manufacturers are making most tire profile round (for motorcycles and scooters), to further diminish the tire contact if and when the rider encounters water on the road -Quote

No, the tires are round with the tread going around the sides instead of flat with an abrupt shoulder transiting to the sidewall like car tires, because scooters and motorcycles ride on the bottom of the tread when going straight and on the sides in curves and corners. It's not to make the contact patch smaller (if that were the case we should all inflate our tires to something just short of blowing them up), but to keep the contact patch uniform as we transition to riding on different parts of the tire going in and out of corners. If you cornered hard and leaning your bike over, your contact patch suddenly became smaller it'd be very scary(not to mention dangerous), like trying to corner hard on a tire made for a trials bike. I had an enduro bike once with a block pattern "dirt/street" tread and somewhat of a "shoulder" on each side of the tread of the back tire, VERY scary cornering at anything but slow speed on the road!

[larry9]

I guess I should have been more thorough in my statement in the above post.
You are right in your assessment of the tire design when riding on dry pavement. The tire cross section in contact becomes larger when cornering. But I was talking about the original design of tires when riding in the rain. Back in the '60's tire design engineers were designing motorcycle tires that would not hydroplane when a biker would encounter rain or wet pavement. The design they came up with was taken from the racing tires of that time which were round in profile (for good grip on dry pavement and cornering), similar to what we have now. However racing tire design did not lend itself to street use in wet conditions. What was designed was the tires we have now with a different radius and the water displacing grooves.
The radius was designed to have a smaller contact area to reduce hydroplaning compared to the tires which had the more squarish design back then.

[Dennis D]

The big improvements in rubber compounds which were taking place around that time would have certainly helped to make that all come together.

[jackthefuzz]

I'm thinking about buying this set of Michelin Sport SC's. does anyone have any experience with them??




Or this Pirelli SL26

[larry9]

I put a set of the Michelin Sport SC's on my RX150. Originally had Kenda which came with the scoot. The Michelin's are a huge improvement. They were almost perfectly round and near in balance as I only had to use a few weights to bring then in. The handling vastly improved too. I'd recommend them over Kenda any time.

[sugarbear]

I just bought a couple of those Pirelli SL26's for my Bajaj Chetak.I was on a different forum and a person said that there a great all weather tire.I hope to find out soon.I heard so menie
bad things about the Bajaj's stock tires.My tires have less then 20miles on them and I'm already changeing them,aint that a laugh..

[earlwb]

Basically, if it is wet outside, then use extreme caution and care in riding a scooter or motorcyle in the rain and on wet roads. None of the tires really work all that well out in the rain. Plus the oils and residue on the roads make them extra slippery to boot. Then in many locales they now like to use bricks embedded in the roads to make them look prettier, but the bricks make those places downright dangerous.
When it is raining or wet outside, do not go fast, do not take corners like you are in a race, it isn't going to work, you will be going down.
Better quality tires may help a lot, but they still aren't going to work in the rain well.
If you put on better tires, do not push your luck by testing them out at jigh speeds in any turns. Slow down and take the turns safely.
Also no tire will save you if you run over a manhole cover at speed in a turn.