TJHOO

1-Is it generally true the grippier a tire is, the more rolling resistance it has?
2-Is it generally true the grippier a tire is, the less harsh a ride it yields?
3-Is it generally true the grippier a tire is, the less durable it is?

johnny99

2 and 3 are obviously false. Harshness is mostly determined by tire pressure and casing stiffness. Durability depends mostly on the thickness (and weight) of the rubber. Published rolling resistance tests have shown that some grippy tires also have low rolling resistance, so I guess 1 is also false.

Grasschopper

Go get some Mich P2Rs and be done with it. Lowest RR, very smooth and plenty grippy...great tire, sorry it took me so long to find it. Vittoria Rubino Pro slick is pretty good too but the P2R is better IMO.

TJHOO

PR2 exactly what I've been using. Also the Conti GP 4000. Now looking at the GP 4000s. Check out this thread too:
https://www.bikeforums.net/showthread.php?t=329393

TJHOO

Thanks for your input,

Perhaps I should have phrased the questions as "what is the relationship between?" (the different factors). Now rereading, the questions look biased in one direction.

I'd tend to agree w/ you on #'s 2,3. Not sure about #1. How accurate are these published reports?

Phantoj

I would say that #3 is generally correct. Soft tires that grip well will wear faster. Yeah, thicker tires will last longer, but is one tire really much thicker than another?

FidelCastrovich

It's not about the thickness of the tire - it's about the compound itself and how supple it is. The softer it is, the faster it will wear and the grippier it will be. Rolling resistance is a phantom variable and shouldn't concern you most of the time - keep the recommended pressure, and you're fine.

Of course, all else being equal - thicker means more durable.

TJHOO

You mean the recommended max pressure?

johnny99

Yes, some tires have much thicker rubber than others. Those are usually advertised as training tires vs. race tires which are thinner and lighter. Also, some tires use 2 different rubbers, softer on the sides for grip and harder in the center for durability.

FidelCastrovich

No, not necessarily. Recommended max pressure for your weight, would be more accurate. More pressure does not always mean less resistance. There's a point where too much pressure equals more resistance, due to reduced grip(the high pressure keeps the bike bouncing, slightly, reducing the amount of power transfered to the ground).

TJHOO

Any guidelines here?

johnny99

Here are Michelin's bicycle tire pressure guidelines: https://two-wheels.michelin.com/2w/fr...154733&lang=EN



The table is also printed on the boxes that most Michelin tires come in.

TJHOO

Looks like a roughly linear relationship (NB, I am not a mathematician).

If correcting PSI for body weight per the above graph, what are the different riding characteristics (harshness, stickiness, rolling resistance) of a heavier vs a lighter cyclist??

Perhaps a lighterweight person can safely use less PSI, and have a less harsh ride? Or does lees PSI translate into the same ride as more PSI for a heavier cyclist?

Any physicists out there?

Campag4life

Grippy generally doesn't mean 1 or 2. Grippy generally means soft compound and that means less durable or 3. Rolling resistance or #1 is generally a function of carcass stiffness which is mostly a function of TPI. (Threads per inch)
The more the TPI, the easier it is for a carcass to displace itself...what contributes to rolling resistance and also btw a more compliant ride or #2. The problem with high TPI, is opportunity for road ingression...more holes in the carcass due to more threads. So its a tradeoff generally between rolling resistance and puncture resistance. Out and out racing tires with high TPI count tend to be faster. Grippy has to do with the softness of the tire compound which portends greater wear.
As mentioned, the Michelin PR2 with 127 TPI is a wonderful balance between rolling resistance and puncture resistance. The downside if any is wear due to its upside with is grippiness which is due to it relatively soft tire compound. Tire selection is a balance and mostly a tradeoff. You need to pick the tire based upon what is important to you. No single tire is all things of course. HTH.

ttopaz

TJ, Already 2 threads about tires. Just buy Mich P2 or Conti GP 4000 and done with it. I like Vredestein Fortezza.
Its not like you are buying a house!

TJHOO

I'd like to trust what I'm riding downhill on at 50 mph

SSP

You can trust the PR2's...I love going downhill fast, and have had mine up to 58 mph. No tire that I've tried inspires more confidence in me when the road points down hill.