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Discussion Starter · #1 ·
So here is the deal. I live in Colorado, there are some amazing twisty roads, the more remote the better. All good...right? Well almost. The issue is sand and gravel. It is random, always seems to be in a corner, is unpredictable, and worse in spring. It can make your heart skip a beat.

So I want to go with 235/40 17 tires on 17x8 6UL wheels. Lots of great advise on that tire size for good pavement.

Though there are better options for clean dry pavement like the Dunlops or Brian's GWR favorite the R1R, I have been thinking about the Yokohama S.Drive. The idea being the move aggressive grooves would deal better with sand and gravel washout than a higher contact tire that can behave like it is on ball bearings

Endless reviews of wet and dry, but not my real world issues


Thoughts???
 
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Interesting, I get the idea of wider grooves for channeling the sand/gravel may work.
 

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Interested as well, I remember on my ducati getting in serious trouble with the sand and gravel common here in Colorado.
 

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Wider tires will help keep a larger contact patch on the road, allowing you more chance to hit pavement instead of just gravel.

This all depends on how much gravel though. If you hit solid gravel from dirt that slid off the mountain, no tire, no matter how deep those treads, is going to save you.

If you can go wider, do so, and drop tire pressure another 1-2 psi so you can conform to the road's anomalies better. The wider tread sipes will only help you if you're driving over scattered gravel, and even then, it's not like the gravel is going to shift its position to be in the most convenient location every time.

Softer tread will help the gravel dig into the rubber and keep your tires closer to the pavement.
 

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Discussion Starter · #5 · (Edited)
Wider tires will help keep a larger contact patch on the road, allowing you more chance to hit pavement instead of just gravel.

This all depends on how much gravel though. If you hit solid gravel from dirt that slid off the mountain, no tire, no matter how deep those treads, is going to save you.

If you can go wider, do so, and drop tire pressure another 1-2 psi so you can conform to the road's anomalies better. The wider tread sipes will only help you if you're driving over scattered gravel, and even then, it's not like the gravel is going to shift its position to be in the most convenient location every time.

Softer tread will help the gravel dig into the rubber and keep your tires closer to the pavement.

Points noted on wider and softer. Agreed.


I guess what raises the flag for me is my two wheel experiences. Having raced mountain bikes, road, and cross tread patterns for those applications and in particular tires for winter training makes me question a huge block slick type design. Same goes for my motorcycles, dirt and road. I have had some VERY close calls on my VFR.

So the logic I was applying the same, a tread pattern that bites into loose situations but is still fairly soft as you mentioned. Realizing I am giving up a little perfect pavement grip for the occasional safety net. And, knowing the Yokohama would be a big step up from stock though not an auto cross tire really.
 

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A thought that can be worked into the scenerio- loose gravel, or any loose material, on a dirt road surface can be pushed into that dirt road surface and forced down and into the relatively soft surface, providing more bite. Hit loose material on a hard paved surface and that loose material will be prone to slide instead.

Dropping the air pressure a small bit, as XR stated, allows the tire to deform over the top of the irregularity (gravel, frost heave, etc.) to maintain tire contact to the surrounding surface, instead of being forced upward over the irregularity, decreasing tire contact, and causing the vehicle to go fractionally vertical instead of continuing to move horizontal. That wastes energy, scrubs speed, and decreases traction.

Since you mentioned the world of the bicycle, search for tire pressures, rolling resistance, tread patterns, supple vs. stiff carcasses, etc. at this website, where they have performed years of rigorous testing on such matters. In a nutshell, wider, more supple tires (supple sidewall carcass construction, not just a soft tread layer) with less-than-maximum air pressures perform just as well on smooth surfaces, and better on rough surfaces, than the traditional logic of narrow, stiff, high pressure tires. I'm sure some of these conclusions could cross over into the world of automotive tires, in a way.
https://janheine.wordpress.com

(Yes, I went to their Compass brand bicycle tires, too, and there is no doubt of the increases in performance and comfort.)

Steve.
 

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Are the Euro rally cars on street legal tires? If so, those would be a good choice.
Best regards
Pete
 

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my opinion is if you are driving on mountain roads and are pushing the handling limits of one of these spiders, perhaps you need to be on a track. if you are on the twistys of mountain roads, and you are pushing that hard, do you think you may be jeopardizing other motorists which are travelling in what may be a "lesser" car. if you are looking to build a dedicated car for the Pikes Peak Hillclimb. I apologize, but if you are pushing past the limits of one of these cars, on treacherous tracks of roads, I feel you are taking unnecessary risks for yourself, other motorists and first responders...... just my $ 0.02
 

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Discussion Starter · #9 ·
my opinion is if you are driving on mountain roads and are pushing the handling limits of one of these spiders, perhaps you need to be on a track. if you are on the twistys of mountain roads, and you are pushing that hard, do you think you may be jeopardizing other motorists which are travelling in what may be a "lesser" car. if you are looking to build a dedicated car for the Pikes Peak Hillclimb. I apologize, but if you are pushing past the limits of one of these cars, on treacherous tracks of roads, I feel you are taking unnecessary risks for yourself, other motorists and first responders...... just my $ 0.02
Well, thanks for the tongue lashing, but NO I am not driving that aggressive. I am looking for as much insurance as possible for just in case grip, not how fast I can go. I drive well within the limits of the car and never that much north of the speed limits on public roads. I am 50 and those testosterone days are in the distance past.

I have been caught out in this car going the speed limit on gravel patches twice. Easy to deal with at lower speeds, but feel the stock tires are just "okay"

That is one reason I bought this car, because it is still fun at safe speeds. And, the reason I didn't buy a C7 after testing them.
 
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Well, thanks for the tongue lashing, but NO I am not driving that aggressive. I am looking for as much insurance as possible for just in case grip, not how fast I can go. I drive well within the limits of the car and never that much north of the speed limits on public roads. I am 50 and those testosterone days are in the distance past.

I have been caught out in this car going the speed limit on gravel patches twice. Easy to deal with at lower speeds, but feel the stock tires are just "okay"

That is one reason I bought this car, because it is still fun at safe speeds. And, the reason I didn't buy a C7 after testing them.



with the 140 treadwear compound on the factory potenzas on the abarth, you will be hard pressed to find a stickier tire. the compound is considered too sticky for the scca stock class in autocross, and is considered to be race compound. gravel is going to be treacherous with any tire, the abs system on most cars is rendered useless when skidding on gravel, because the wheels will not lock and dig into the gravel contacting solid ground. the only prudent action is to slow down below the speed limit, much like driving on iced roads. there is no wheel tire combination which will give you control in that situation. knowledge of gravel on a roadway should induce fear and caution. my commentary was not meant to be a tongue lashing, it was meant to caution....
 

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Discussion Starter · #11 ·
with the 140 treadwear compound on the factory potenzas on the abarth, you will be hard pressed to find a stickier tire. the compound is considered too sticky for the scca stock class in autocross, and is considered to be race compound. gravel is going to be treacherous with any tire, the abs system on most cars is rendered useless when skidding on gravel, because the wheels will not lock and dig into the gravel contacting solid ground. the only prudent action is to slow down below the speed limit, much like driving on iced roads. there is no wheel tire combination which will give you control in that situation. knowledge of gravel on a roadway should induce fear and caution. my commentary was not meant to be a tongue lashing, it was meant to caution....

I was looking for some advise and wisdom from the forum, not this. And yes, I have common sense!


Over you!
 

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My experience with inopportune gravel on the bends of fun twisty roads normally has it scattered pretty evenly across the road surface making it unavoidable. And when finding this on a motorcycle it can lead to quite a "messy pants" experience.

Thinking more about it since my last reply I can't help but wonder if you will succeed in finding a tire compound, width, tread pattern, and air pressure combination that will put the odds of significant traction changes back on your side of the court. The wider a tire becomes, and the lower the air pressure, more tire surface contacts the pavement resulting in less vehicle weight per square inch of tire contact, further reducing traction. Yeah, maybe wider tread grooves (meant to channel water) can assist, and maybe put more weight on the rubber that does touch the ground... hmmm. But sand and gravel don't behave like water when a tire rolls across it. Water is easily moved by the contact tread into the grooves, sand and gravel do not, they tend to roll under the weight of the vehicle and lift the tread off the road surface, unlike water which gets pushed out from the tread into the groove

It seems the only way to know for sure is to try. You may notice an improvement, but I don't know if it would be a measurable improvement worth the cost and effort. It could also lead to a false sense of security- worked great in one bend but bit you (and maybe the oncoming vehicle) in another. It's easy to say "just slow down" when approaching a messy surface but in the twisties you don't often get the benefit of an extended view to prepare for the conditions out of site around the bend, meaning the prudent thing to do is just run the route at lower speeds.

Keep us updated if a tire is found that fills the need.

Steve.
 
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