Prepping Urethane Tires No Grip

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Prepping Urethane Tires No Grip

Postby jscot111 » Tue Nov 01, 2016 1:36 pm

I,m trying to prep some PG Urethane tires for a proxy, usually run QS silicones. I nail polished the tires to the rims, trued on the hudy and they have absolutely no grip what so ever. I tested on a wood track that usually sees silicone's and can,t believe there's no grip at all. On this same track I have no problems with running NSR supergrips and wonder if its something I did wrong with the tires or just a mismatch between Urethane's and silicone's.
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Re: Prepping Urethane Tires No Grip

Postby HomeRacingWorld » Tue Nov 01, 2016 2:12 pm

Not sure what it could be. Never had a surface yet that a urethane did not work on. Maybe some excess heat from the truing process did some harm to the tires.
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Re: Prepping Urethane Tires No Grip

Postby docdoom » Tue Nov 01, 2016 3:55 pm

are the tires smooth or have a rough feel to them after you trued them.
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Re: Prepping Urethane Tires No Grip

Postby strangebrew » Tue Nov 01, 2016 3:59 pm

Ran silicone on my small masonite oval for a couple of years.
When I started using urethanes I had no grip after 5 or 6 laps......They glazed over......cleaned the tires & same thing.
I had to scrub my track more than twice with lacquer thinner to get them to work....no problems now.
Silicone put some kind of film on my track that killed the eurethanes.
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Re: Prepping Urethane Tires No Grip

Postby mikeinclover » Tue Nov 01, 2016 4:26 pm

Scott you are just used to Quick Slicks traction and nothing is going to compare to that. Just kidding couldn't pass it up.
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Re: Prepping Urethane Tires No Grip

Postby SuperSlab » Tue Nov 01, 2016 5:29 pm

This is one of those ongoing contentious topics. You are likely to get dissenting voices but my personal experience is that running silicones absolutely kills the traction for urethanes. You will have to be prepared to run hundreds of laps to get the urethanes up to speed. But once there things should be fine.

However: once it is good for urethanes you will find it is awful for silicones. My personal STRONG belief is to not mix silicones and urethanes.
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Re: Prepping Urethane Tires No Grip

Postby gascarnut » Tue Nov 01, 2016 5:31 pm

Show us a photo of the tire surface, that might help.

As the others have said, if the tires are not polished smooth after trueing, the grip won't be good. Use some 600 or 1200 waterpaper wet with isopropyl alcohol and polish them till they are smooth and black again.
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Re: Prepping Urethane Tires No Grip

Postby chappy » Tue Nov 01, 2016 7:12 pm

I agree with Slab 100%. It takes a ton of cleaning to get the silicone glaze off the teack surface, and then a while to get the urethanes to get grip. And of course then the silicones will be at a disadvantage as they pick up the urethane left behind.
Bottom line is Urethane and silicone do not play well together.
Perfect example is the fact that urethane tires can be made in a silicone mold and no release agent is required. They just repel each other.
Not knocking one or the other, but they wont give best performance when mixed.
Bob
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Re: Prepping Urethane Tires No Grip

Postby steeveew » Tue Nov 01, 2016 8:10 pm

I have the same problem.I can run hundreds of laps with rubber tires,then run urethanes,the times and traction just goes away.
It's crazy,the first 5-10 laps,they work pretty well.after about 10 laps I lose about 3/10's after about 30 laps, I've lost over a second.
Lap times are normally high 7's to low 8's.Urethanes are about 9.3.
I basically just set the cars up with rubber then throw urethanes on it and send them off.



Good Luck,
Steve
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Re: Prepping Urethane Tires No Grip

Postby mattb » Tue Nov 01, 2016 8:16 pm

Urethane rubber will cure in a silicone mold. Silicone will not cure in a urethane mold. Might be interesting to try it someday and see what does happen to the silicone in a urethane mold.
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Re: Prepping Urethane Tires No Grip

Postby Abarth Mike » Tue Nov 01, 2016 8:42 pm

I don't have a Hudy and don't , as a rule, use urethane/silicone tires. However from what i have gleaned Hudy trues tires in a single position and so leaves the "profile" of the sand paper grit in the tires surface.

So the tire polishing advice is valid. As the tires are already true this can be done on the car. Use 1500 or 2000 grit paper with the liquid of your choice.
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Re: Prepping Urethane Tires No Grip

Postby Ky.Slot Racer » Tue Nov 01, 2016 9:26 pm

good topic, i`ve been curious about this myself, proxy races, my cars seem disabled. and when I get them back home they run like poo poo. after a quick scuff of the tires, they convert back to awesome. Maybe most of the top runners in proxies are using silis. I may have to re think my go to "race" tire.
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Re: Prepping Urethane Tires No Grip

Postby Audi1 » Wed Nov 02, 2016 4:46 am

I have a similar, repeatable observation on my routed wood track. The best grip comes from silicone tires (we just got finished running the CanAm proxy cars from the SCI board and one of the P-Class cars set a new track record of 5.520 seconds). Next fastest on my track is rubber; particularly the NSR Supergrips and Ultragrips.

Third fastest, but a long ways back, is urethane. I've tried Paul Gage PGTs and XPGs, Luf's urethanes and D'Art Hobbies urethanes. All had similar results. The truing/profiling/preparation recommendations from other posters are good; the smoother the surface of the urethane tires, regardless of the manufacturer, the better the grip on my track.

I'm prepping a urethane-shod Carrera DTM car now for the Carrera Scramble proxy and having worked most recently with my Group 5 NA car, which is on NSR Ultragrip rubber tires and which runs laps in the mid-5 second range, I started my testing of the DTM car yesterday afternoon - with poor traction and high 6 second laps. I have a lot of work to do on that car..............!

I really like urethane tires from the standpoint of truing them. But, at least on my track, they are grip-challenged.

When I see posters say things like: nothing beats the grip of urethane tires on my track, I just shake my head and wonder what I'm doing wrong............

Allan
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Re: Prepping Urethane Tires No Grip

Postby redlynr » Wed Nov 02, 2016 5:11 am

I can't stand urethane, except on my fronts. No grip on my track. If I am going to enter a race that requires urethanes, which I have only done once or twice, I test with something like an S2 tire then switch to the prepped urethanes before shipping and pray. This is basically what I do with rubber too...
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Re: Prepping Urethane Tires No Grip

Postby RichD » Wed Nov 02, 2016 8:35 am

I have done extensive testing of both silicone and urethane tires. Silicone tires pick up dust and urethane tires do not. If you are trying to compare tires it is best to do that on a perfectly clean track, at least for a start. If there is a little dust on the track silicone tires will quickly get coated and the grip will go away. Cleaning the tires will restore grip and if you do that frequently the track will eventually get cleaned, at least where the tires roll. Urethane tires do not like a lot of dust either but you will not get the dramatic loss of grip that you get with silicone tires. Silicone tires do leave a small amount of residue on the track, when I switch over to testing urethane tires I first strip down my track, which is made of Sintra, with naphtha. Even though I have done that urethane tires will get coated with something that will not be removed by rolling on sticky tape. The tires need to be washed to remove the film. After a dozen cycles of running the car and washing the tires the track will become conditioned and frequent washing will not be necessary. With the track optimized for both types of tires the silicone tires always give slightly lower lap times. If you are looking for optimum performance with either type of tire you should stick to one or the other. If you use one type and are doing a proxy race with the other type you should use the appropriate conditioning routine and refrain from using the other tires until that race is over.
Using a Hudy will leave grooves in the tires, but that can be avoided for the most part. I switched the drive pulley around so that the wheel axle could have a little side movement. As I am truing I poke the pulley with a stick to move the wheel from side to side as the tire is being ground. By the way if you grind with too much pressure you will reduce the diameter of the tire without actually removing the high spots. With some brands of silicone tires the routine that I use gets me tires that are ready to go, other makes may need extra conditioning. My experience has been that most urethane tires will need to be polished after they are trued for the best performance. I have never had any luck using sand paper, I have a skid pad made up of Ninco track and I run the tires on that for hours in both directions until they are perfectly smooth.
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