PL Hyrax vs RC4WD Wrangler, why Hyrax is so slippery?

[Egsise]

Any explanation why the bigger 4.75" Hyrax with dual stage foams is so slippery compared to smaller 4.19" tire with quite stiff foams?
https://youtu.be/eGHU4pNh2Zk

On some places the Hyrax grips as well as the Wrangler, but on some rocks it suddenly loses traction.
And I mean it slides like in the video, Hyrax feels quite unpredictable because of that.

Hyrax contact patch is quite big, I liked how it floats on sand and mud.

[oldmancrawl]

I don't know much about much, but the bigger contact patch also translates to less contact pressure.

[Egsise]

Originally Posted by oldmancrawl

I don't know much about much, but the bigger contact patch also translates to less contact pressure.

Yes. But shouldn't bigger and softer tyre grip better, that is what everyone says.

[soze]

If you are running in places with loose sand or dirt, or with a little moisture, then the Hyrax won't do as great. This is exactly the problem I have where I run my rigs, and the reason that I mainly run the Pro-Line BFG Krawler in G8 Compound. The Hyrax don't clean out as well as the Krawler and allow sand and dirt to just stick in the grooves as well as having a smaller contact patch.

[Egsise]

Originally Posted by soze

If you are running in places with loose sand or dirt, or with a little moisture, then the Hyrax won't do as great. This is exactly the problem I have where I run my rigs, and the reason that I mainly run the Pro-Line BFG Krawler in G8 Compound. The Hyrax don't clean out as well as the Krawler and allow sand and dirt to just stick in the grooves as well as having a smaller contact patch.

The video shows the place...
Hyrax is slippery on a clean dry rock.

[oldmancrawl]

Originally Posted by Egsise

Yes. But shouldn't bigger and softer tyre grip better, that is what everyone says.

Well, it seems softer should grip better, but in the case of that slippery rock, maybe the tire still isn't quite sticky enough.

With the bigger contact patch/ less contact pressure, maybe the truck isn't heavy enough to push the tire down to stick to the rock. It's kinda "floating" on the rock. Same reason why the bigger tire works well in sand and mud.

I think bigger tires would work better in rougher, jagged rock, where more tire means more area for a better chance to find something to grab onto. I dunno, just guessing.

It'd be interesting to see how the hyrax works with some weight added to the truck.

As I say, I don't know much about how the rubber and treads compare on those tires and the difference it makes, I'm just thinking physics of how 1:1 tire sizes work.

[Egsise]

Originally Posted by oldmancrawl

Well, it seems softer should grip better, but in the case of that slippery rock, maybe the tire still isn't quite sticky enough.

With the bigger contact patch/ less contact pressure, maybe the truck isn't heavy enough to push the tire down to stick to the rock. It's kinda "floating" on the rock. Same reason why the bigger tire works well in sand and mud.

I think bigger tires would work better in rougher, jagged rock, where more tire means more area for a better chance to find something to grab onto. I dunno, just guessing.

It'd be interesting to see how the hyrax works with some weight added to the truck.

As I say, I don't know much about how the rubber and treads compare on those tires and the difference it makes, I'm just thinking physics of how 1:1 tire sizes work.

I did try 4.75" Wrangler with metal beadlocks and dual stage foams vs 4.19" Wrangler with plastic beadlocks and stock foams that are quite stiff.
Again the 4.19" was better, but the difference was not that prominent.

I'm just surprised that this thing is not mentioned or discussed anywhere.
Maybe this is the reason why so many recommed adding weight, it brings the big tyre performance to the same level what smaller tyre has?

There's a link on the video to my previous test, there's a heavier TRX-4 and same tyres in the same place, again the smaller 4.19" Wrangler is the best.

Has anyone tested 4.75" Hyrax vs 4.19" Hyrax, or any other tyre in two different sizes?

[Egsise]

https://youtu.be/FvvKf4sSHP0
Found one! But he says that bigger contact patch is better.

[oldmancrawl]

It is interesting to see how tire sizes compare.

I think on smooth slippery rock, the smaller tire works better because of contact pressure.
The bigger tire has more rubber on the smooth rock, but it doesn't seem to stick any better.
In the vid, he mentions the bigger tire has more traction, but the tires still spin more on the smooth rock.
Whereas on rough, jagged rock, the bigger tire with soft foam conforms to the edges, bumps, etc... to make it grab.

Softer foam in a bigger tire on smooth rock just spreads the weight more, putting less pressure, making it spin more.
Bigger tires seem to work better in rough or soft, loose terrain with more tread to grab. Smooth rock, there's nothing to grab onto.

I dunno... just ramblin' trying to figure it out.

[ferp420]

If you run your rig on glass it gives you a realy good idea on your tires contact patch you can see whats touching and whats not

There are so many variables afecting the tires its hard to say what is doing what
were i live i dosent realy matter what tire i run they all work about the same its like running on 60grit sand paper everything grips but when i was in the mountains on the creek i had alot of wet polished granit and mossy rocks the hyrax did alot better than any of the rest untill it got over 90° out then they started to go down hill
i switched to axial rtr r40 krawlers and they worked great they would bite when the proline tires just folded over so temperature has alot to do with how tires work also wieght makes a big difference

There is a reason why the comp guys narrow there tires not because its fun to do and it dosent make them look better so there must be performance to gain there comp rigs are vary light and there tires are tall and narrow
There is no one magic tire so you kinda have to try them and see what works best for your rig

[MOguy]

having different foams is like having different tires. Just like tires some foams need to break in. It take a while before dual stage foams works well.

Even then unless you have a heavier RC regular foam will allow your tire to conform to the surface better and give you better traction.

[smog]

Personally I have observed that there appear to be many subtle factors that will significantly effect rock performance on the terrain around here. I run on pre Cambrian shield that looks very similar to the rock in your video. I also crawl a lot on limestone.

Did you film both tires on the same day or at the same time of day? In my experience, a few degrees of temp or the affect of direct sunlight warming a rock will affect a tires performance significantly. Especially on steeper pitches and during the transitional seasons of spring and fall where daily temps fluctuate more. I have also found that rock with traces of moss or fungus growth will sometimes look dry but there may be moisture trapped in those life forms that keep it somewhat slippery for a period of time after a rainfall.

Just some thoughts and observations.

[Egsise]

Originally Posted by smog

Personally I have observed that there appear to be many subtle factors that will significantly effect rock performance on the terrain around here. I run on pre Cambrian shield that looks very similar to the rock in your video. I also crawl a lot on limestone.

Did you film both tires on the same day or at the same time of day? In my experience, a few degrees of temp or the affect of direct sunlight warming a rock will affect a tires performance significantly. Especially on steeper pitches and during the transitional seasons of spring and fall where daily temps fluctuate more. I have also found that rock with traces of moss or fungus growth will sometimes look dry but there may be moisture trapped in those life forms that keep it somewhat slippery for a period of time after a rainfall.

Just some thoughts and observations.

Same day, all that was done within 15 minutes. First the dry rock run with Hyrax, then Wrangler on dry rock, then Wrangler on wet rock and finally Hyrax on wet rock.
Subtle changes, temperature and moisture differences. It sounds that Hyrax is very unpredictable if it's not in its optimum environment.
Good point on the rocks where I drive, indeed it's the exposed precambrian rocks.
Very old rocks that are smoothed by the weather and five ice ages that have occured in the past 2.4 billion years. I've never even seen any other kind of rocks in the wild.

Rock is not dead!

The surface is alive, all sorts of moss grows there.

[Egsise]

Originally Posted by oldmancrawl

It is interesting to see how tire sizes compare.

I think on smooth slippery rock, the smaller tire works better because of contact pressure.
The bigger tire has more rubber on the smooth rock, but it doesn't seem to stick any better.
In the vid, he mentions the bigger tire has more traction, but the tires still spin more on the smooth rock.
Whereas on rough, jagged rock, the bigger tire with soft foam conforms to the edges, bumps, etc... to make it grab.

Softer foam in a bigger tire on smooth rock just spreads the weight more, putting less pressure, making it spin more.
Bigger tires seem to work better in rough or soft, loose terrain with more tread to grab. Smooth rock, there's nothing to grab onto.

I dunno... just ramblin' trying to figure it out.

I appreciate your thoughts, this is an interesting thing because it's contradicting the general opinion.

Originally Posted by ferp420

There is a reason why the comp guys narrow there tires not because its fun to do and it dosent make them look better so there must be performance to gain there comp rigs are vary light and there tires are tall and narrow

Exactly, I've been wondering why the comp crawlers prefer narrow tyres.

[MOguy]

I do comp on rock, mostly dry and some sand or dirt. My experience is that when the MTRS lost traction they spun drifting side to side and when the hyrax lost traction they spun and stayed in place.

I don't like the tires drifting side to side (swampers also do this). I can turn my wheels left to right and control the drifting side to side with the Hyrax and the MTRs kind of do their own thing.

The MTRs also don't have as good bit on the sidewall as the Hyrax which is surprising. The MTR look like they would and the Hyrax look like they wouldn't but the opposite is true. I had MTRs in my 1:1 Jeep and they were great so I got some for my RC, they are not that good on my RC.

[oldmancrawl]

I've been wondering why people shave the treads on tires... side knobs in particular that I've been reading about.
I'm guessing it's the same principle as a car tire racing slick or a rock climbing shoe?

[Bray D]

Sometimes less traction is better. I've been playing on some big limestone lately and shaving the sidewalls has made a huge improvement. You can sidewall scrub really hard without the tire biting and trying to flip you backwards. Slightly more pliable sidewalls is a plus as well.

Poor pic, but imagine dropping a tire down into a hole and the upper portion of the sidewall biting the adjacent rock. It tries to push you backward or up and over backward if you're on a steep climb.

[MOguy]

Originally Posted by Bray D

Sometimes less traction is better.

I have only been doing this about a year and I have noticed this.

I have a 5.5lb 1.9 comp build with Hyrax and a 2.2 TRX upgraded electronics and stock chassis on some old school hammers and super grippy pit bull XOR,

The Hyrax get good traction but are easier to break loose at will. The 2.2 are very high traction tires, very hard to break loose at will.

They drive very different. On the 1.9 I like some wheel spin and hitting the throttle hard for a quick second. It spins for a second, hooks and hops up. The TRX is just over 7.5lbs. It won't work that way with the TRX. Usually It has to crawl, slow and steady". For traction issues on the TRX I open and close the lockers. Like you said sometimes too much traction at the wrong tire can screw you.

[soze]

Sometimes narrower tires are good for wedging into grooves and using that groove to pull your rig up. I've noticed this at some lines at CDM where the narrower tire has an easier time of just dropping the tire into the groove and driving up, where the wider/bigger tire would just bounce on the groove since it can't fit and sit in the groove.

[Bray D]

Tire and foam selection is likely the biggest variable when it comes to performance. Skinny tire research is what led me here - I'm trying to decide which 1.9 I want to cut up to make some tall and skinnies from.