Slicks on a tandem yes or no. the set up at the moment - wheels are mavic 719 tyres are conti contact 700x28.
all riding is on tarmac ,i ride slicks on my road bike all the time , but my stoker who ownes the tandem loves speed so anyway good idea or should we leave well alone.

thanks

anto.

AFAIK more traction with slicks. Tread reduces the amount of rubber in contact with the road.

I remember reading an article years ago where a engineer for a tire manufacturer stated that they only put tread on to make the customers happy as many believe that the tread give traction.

Many thousands of miles with slick tires on our tandems. No issues, at least not because they are slicks.

Just like on car and motorcycle tires, grooves in the tread are for channeling water away from the contact patch. So if you ride in the wet, slicks might have less grip. But I take it very slow in the wet so I don't think it matters to me.

Tread only becomes a factor in the rain at the point when a tire would begin to hydroplane. Realistically, does not happen on a bicycle due to small size of contact patch. The surface of the road has enough imperfections to take care of water disbursement for a bike.

Thanks a million lads most helpfull .so conti Gator hardshell would be a good choice .i have them on my road bike but only come in 25's as far as i can make out. i 'de like to use 28 just that bit more comfy.
thanks again folks much appreciated.
anto.

Hydroplaning is not an issue on a human powered bicycle. There is a formula for hydroplaning speed vs tire pressure; units of psi and mph:

nine times the square root of the tire pressure equals the hydroplaning speed.

Ref: Hydroplane speeds for vehicles and many other sources

For 70 psi (rather low for tires on a tandem) the hydroplaning speed is 75mph.

while I am no where near an engineer. I do have real life experience and do not think this is correct.

during a decade of motorcycle road racing as a pro I have many times gone over these speeds with slicks/road race /rain tires. This includes damp tracks to full monsoon rain. With tire pressure ranging from 22 to 36 psi.

I think there is more physics involved than a simple math problem. Such as shape of contact patch. Which on a bicycle / motorcycle is oval and on a car is square / rectangle.

The 9X equation is for slicks, as soon as you add any sort of tread pattern, the multiplier increases, often dramatically. It is all math, some of it not so simple. Bottom line, hydroplaning is not an issue on a human powered machine.

In most Engineering situation, we bound the problem, usually like in this case, bounding the problem on one side is sufficient to provide a conservative answer to the question. If we can set a lower limit on when hydroplaning will occur that is sufficiently above any achievable speed, we are done, and can move on to the next question. 9X the tire pressure provides a sufficient margin to say that hydroplaning is not an issue with bicycles.

Will additional study of the details provide more information - yes, will it change the conclusion - and there fore provide additional value for the question - No. If the question is changed, that is another whole issue, which should be taken up in a different forum such as a motorcycle , automobile or aircraft forum. There is a great deal of discussion and hard information on hydroplaning in aircraft forums.

agreed

At ages 82/80 we ride 25mm tires. Switched from 23s about 10 years ago.
When your present tandem tires wear out, get some slicks.

respect

Why are there tread grooves on some bicycle tires?

Many people think tread equals traction. So manufacturers make them.

Off road is different, many tires are used road and off road.

I run Conti Gator foldables in 700x28... so they are out there. Most bike shops do not carry this size though, you very likely will have to resort to web sales site.

i think my buddy who ownes the tandem is going to hold on for a while, maybe wait until new tyres are needed.
still good to know slicks are good to go.thanks again.