jur

I must admit I'm wavering at this point in my opinion. There are plenty people who report by personal experience that certain tyres do not perform well in the wet, regardless of important write-ups like this from Sheldon Brown.

I also used to subscribe to the idea that tread is not necessary based on common sense articles such as these. It seems obvious once you think about it.

But lately I'm thinking of some of my shoes' performance on wet floors. Obviously hydroplaning is completely irrelevant, but some shoes still completely suck - I have to be very careful or I slip. Why would tyres be different in this respect? Once the rubber is coated with a thin layer of water, it is lubricated and can slide better. Big blocky tread won't change that, but how about a fine pattern like on the Primo Comets? Common sense tells me that water would be squeezed just a little bit better than with a smooth surface, improving on the lubricated rubber condition. This would only count on very very smooth surfaces, most tarred roads are roung enough to make the above idea not count on those surfaces.

So maybe this could explain why Scorchers reportedly suck in the wet, while I am confident on my Primos?

Sheldon Brown

Actually, that was written by Jobst Brandt, though I agree with it.

My take on this is in my general article on Tires: https://sheldonbrown.com/tires.html#tread

Brandt believes that the composition of the rubber has a major effect on wet traction, specifically that rubber with lots of carbon black in it is stickier than the trendy multi-colored tires that are currently infashion. I have no specific experience with this, but I incline to trust Jobst on this, as he is a tribologist by profession. (A tribologist is a mechanical engineer specializing in aspects of friction.)

They do? That's news to me. :-/

I replaced the Pr1mos on my Greenspeed with Scorchers, they seem nicer in general. However, I had to remove the fender 'cause the Scorchers are a bit fatter than the Pr1mos, so I've been avoiding wet surfaces since then! (A new, improved fender is supposed to be on the way to me from Greenspeed USA.)

Sheldon "Staying Dry" Brown

SesameCrunch

I'm hardly the expert, but the theory is that the contact points on bicycle tires are so small that water is squeezed out efficiently. Hence tread for expelling water is not necessary.

Your analogy of shoes doesn't necessarily hold because the area under your shoes are probably 20X greater than the contact point on tires.

Now, as Sheldon "the Omnipotent" Brown points out, rubber compound and other factors matter significantly more between tire performance in different road conditions.

That's my SWAG and I'm sticking with it....

pm124

Well, when God descends to comment, there's not much more to add. Thanks so much for your input on this, Sheldon!! (OK, so I'm an atheist, but you are as close as one gets in the realm of bikes.)

Actually, the poor performance of the Scorchers was noted on an upright bike, not a trike, which could explain the discrepancy. But this was just the opinion of James Swift, another forum member. I haven't received my wheels yet, and will let people know whether I also find them to be slippery.

I wonder if anyone has tried the Schwalbe Kojack yet...

brakemeister

compound is everything ..... well wait not everything maybe ... its also the flexibility of the sidewall and general flexibility of the tire .... also different tire pressure is very important ....

havent read Brands thesis but most likely at least 90 % right ..lol

thor

jur

So which view do you subscribe to, in the light of this comment you made in another thread? It would seem you think tread is important...?

pm124

Damnit, Jur, I'm a doctor, not a materials scientist.

Actually, I'm not experienced enough to make an educated comment, so I'll refrain. But your shoe test does provide one point of reference. I have gum sole shoes that are fatal in the rain. I've ended on my ass more than once, and thus had to toss them. They had the exact same tread as my Fluvogs, which grip better than any shoe I've had. So materials must make a difference.

As soon as my wheels are finished, I'll make a comment. I need them badly; I don't want to buy another tire for my 355s, and the tube is practically showing through the Stelvios I have. Incidentally, my Stelvios are completely bald and corner fine in the rain.

maunakea

IMO, compound is key.... and my basis for this is inline skating wheels. Inline skate wheels for wet street skating vs. dry street skating differ only in compound... the wheel profile, contact patch, etc., is identical within a manufacturer's product line. MPC, Hyper, Star, Matter, etc., but especially MPC, make wet outdoor wheels that stick during push on wet surfaces, and their dry outdoor wheels don't stick on wet surfaces. Of course, polyurethane skate wheels are different from bicycle tires, but my point is compound makes a major difference while holding profile and contact patch constant ... with no tread.

jur

So if James is correct about Scorchers not being great in the wet, perhaps their compound needs scrutiny.

Where did James report this, anyway?

Fat Boy

Here's something that I can comment on with a little bit of certainty.

Some sort of tread pattern is much better than none assuming that we're talking about riding through standing water. If we're just talking about damp pavement, then no tread is best. The crossover point is going to depend on many variables. The tread pattern itself isn't terribly important. You want to keep as much rubber on the ground while still allowing the water somewhere to go. A couple longitudinal groves and something across the tread face, usually at an angle is enough. It's not like you're digging into mud or snow. You just want to pump a little water.

Beyond that, compound is very important. For one reason or another, a high silicon content seems to help wet performance in tires. A certain amount of carbon black content is necessary, but 'stickier' tires generally contain more oil than a 'hard' tire. This allows for better adhesive grip qualities, but reduces the
available mechanical grip qualities of the tire. Since we aren't loading the tire heavily in a lateral or longitudinal direction, we can give up a fair bit of mechanical (think Velcro) grip from the tire.

The construction of the tire carcass is massive, but I'm not aware of any build property that is 'rain' specific. I guess if you were building a rain tire you'd build it with a flatter tread profile because the lean angles will be significantly more shallow.

On a racecar, I run higher tire pressures in the wet than the dry. This is done specifically to keep the channels of the tire more open to pump more water. They may not be the thing to do on a bike. You might want to reduce pressures to get more contact patch area. It's really hard to say without testing it.

jur

Here is the thread - and it was Fear&Trembling who reported the wet performance, James didn't do wet testing, at least according to that thread.

In this thread James commented about them being "downright dangerous" in the wet, although it is unclear if this is from his own experience.

I wonder if James will pipe up here...?

maunakea

Fat Boy makes some good points. We have inline skate wheels and car racing tires for comparison. Can't say that I ever skated through standing water.... that would mean immediately pulling the bearings and regreasing to prevent rust.

invisiblehand

Don't you find it weird calling someone "Fat Boy"?

The only thing missing from FB's blip though, is the velocity one would have to be traveling at for the little grooves to make a difference.

For what its worth, I have never used a tire without any tread. Very little tread, yes. They are just too difficult to find and purchase.

Wil Davis

Vittoria Pro Slicks, Vittoria Rubino Slicks; to name but two from the same manufacturer. I use them all the time, both on the road and on rollers; very quiet tyres, very comfortable ride.

- Wil

invisiblehand

Sweet bikes Wil.

Does Vittoria make 20" tires?

-G

brakemeister

https://www.thorusa.com/dahon/accessories/tires.htm

a little down the page the new Schwalbe tire is called Kojack ..... they seem to be a nice racy alternative to the stelvios and replace the older slicks ....

no idea how they compare at this moment..... havent had time to put some on a bike yet.. but with Schwalbe know how, they should be good ...

back to thread.... i have people swear that the "sipping"grooves ... tiny little bitty cuts make a difference .. my boat shoes have them in the sole and they are grippy in the wet.... But I realy think that they only absorb stretch in the rubber and therefore allow the rubber portion which has contact to lay flat versus curled up... ( does that make sense ? )

thor

EvilV

If you run them as long as I do, the tread disappears anyway. LOL.

dooley

i'm stick my oar in on this one. firstly motorcycle racing wets do have tread. now i don't know the reason for sure, but i'm guessing it has something to do with the fact that most road surfaces aren't actually very smooth at all, it's actually like miniture crazy paving (without the mortar). i reckon what happens is that the edges of the tread blocks sink into the gaps a bit and are forced against the edges of the stones

EvilV

I'm no sort of an engineer or anything like that, but it strikes me that we shouldn't be comparing motor vehicle tyres with bicycle tyres when talking about tread. The size of the contact patch is very different as are the speeds. Aquaplaning as I recall only takes place at far above bicycle speeds. Lots of racing road bikes use tyres with little in the way of tread - they are virtually slicks as far as I can see, and I don't think any British cycle shop would be selling tyres that were dangerous in the rain - we get a fair bit of it as far as my experience goes. The road racing chaps about these parts do thousands of miles a year in all weathers on slick tyres. Maybe they're just suicidal.

dooley

i'm not saying slicks are rubbish, just that there's a possibility treaded tyres grip may grip better. as for the motorsport comparison, aquaplaning isn't really an issue at the severe lean angles, so why have tread all the way round the tyre?

Sheldon Brown

That's because of hydroplaning.

This can be an issue with motorcycles due to higher speeds and lower tire pressures, but it is NOT an issue for bicycles.

See: https://sheldonbrown.com/gloss_ho-z.html#hydroplaning

Sheldon "Bald Is Beautiful" Brown

psykoocycle

wow interesting thread...

so compound seems to matter more...

I still think depending on your weight, amount of rain, threads will still help in the rain...

You can argue that due to the surface area, water should disperse easily, but I'm sure adding sipes would still help a bit... mind you this also depends on other factors (how much rain, width of tires, weight of rider etc...)