Traction (tires)??

[EVLEE]

I have been getting some replies about tires and what speeds they can do.I was just wondering what about traction? I know there is not much loss of grip on the slicks at paved road courses I am use to.Salt at say Bonneville or even El Mirage has to be different.Does or has anyone tested different tires for better traction on salt?? I know that Tires (even being able to get them for your car)seems the BIG question right now and seems justly so!! So how about the traction ??

 M&Hs Frontrunners  look fine for the front but look like they do not have much of a gripping tread for the rear??
 Goodyears look like they have some and I just wonder if they would be better for the driving wheels ??
                           Lee

[Sumner]

I have been getting some replies about tires and what speeds they can do.I was just wondering what about traction? I know there is not much loss of grip on the slicks at paved road courses I am use to.Salt at say Bonneville or even El Mirage has to be different.Does or has anyone tested different tires for better traction on salt?? I know that Tires (even being able to get them for your car)seems the BIG question right now and seems justly so!! So how about the traction ??

 M&Hs Frontrunners  look fine for the front but look like they do not have much of a gripping tread for the rear??
 Goodyears look like they have some and I just wonder if they would be better for the driving wheels ??
                           Lee

Ok I'm just trying to figure out what you are talking about with the traction (coefficient of friction) on the salt and how to deal with it.  The end result is that you can not only spin the tires accelerating, but you can get to a point where the aero drag on the car will cause the tires to spin and you can't go any faster no matter how much you "peddle" the car.  

Below is a formula that has been used for this.  The trick is knowing how much HP is actually needed to run a certain speed (HP needed to overcome aero drag and rolling resistance [note: the car's weight doesn't really come into play here only when you are figuring the acceleration rates]). The other variable is the coefficient of the salt surface when you are running.  I see numbers of a .6 friction coefficient for really good salt and .4 for bad (slippery) salt.  I'm assuming these numbers are for a typical tire being run at b'ville with minimum tread and a narrow width.  Personally I don't think you would see much difference in the tires you mentioned.  And Personally I would like to see the Goodyear Land Speed tires used as the driven tires if you felt you might end up in the high 200's at some point.  They are designed for this environment (driven tire at continuous high speed).

Below I picked some numbers that might be close for your car or might be a mile off.  

In the first I "assumed" it would take 225 HP to run 210 mph.  To the right of those numbers you can see the weight needed on the rear (or driven tires) to avoid wheel spin at .6, .5 and .4 friction coefficients.  In the second case I "assumed" you could run 200 mph with 200 hp.  Notice the difference in weight needed for traction.  In the third case I left the speed at 200, but "assumed" a HP figure of 150 to see what the result was with the needed weight. And in the last case I went back to the 225 HP, but "assumed" we could run 250 mph with it.  The weight went down from the first example.

-----------------Thrust = HP X 375 /Speed----------------------    
---------------Weight needed on rear wheels--------------------                  
-----------------------------------------------.6 friction--- .5 Friction --.4 Friction
Thrust = HP X 375 /Speed -------------- Coefficient --Coefficient --Coefficient
402 = 225 X 375 / 210-----------------------670 lbs------804--------1004
375 = 200   X 375 / 200-----------------------625 lbs------750---------938
281 = 150   X 375 / 200-----------------------469 lbs------563---------703
338 = 225   X 375 / 250-----------------------563 lbs------675---------844

So the more aero the car is the less HP needed to go fast and the less weight that is needed on the drive wheels for traction.  Good for you (with a streamliner) and bad for someone driving a brick like a roadster or a coupe and the reason those cars have to add weight or a spoiler (if allowed) to gain downforce on the drive wheels if traction becomes a problem.

A little disclaimer "I don't know how accurate any of the above is, since I'm trying to make sense of it myself at this point, so I would like input on this topic myself".

c ya, Sum

[EVLEE]

I am going to shave my tires with a carving knife!!!like The world's fastest Indian
                                             Lee

[JackD]

I am going to shave my tires with a carving knife!!!like The world's fastest Indian
                                             Lee

If you have the time.
 You must recognize that he started when the tires and the bike were new.
By the time he was done the shoe polish that originally did just his shoes was also used on his hair.
 Only at the last did he rub it into the cracks in his tire.

[tomsmith]

I guess I am iggerunt or sumtin.  It looks like having tread or not on your tires is irrelevant so far as having traction on low coefficient of friction surfaces.  Gee, when I was riding desert I thought that having gnarly knobbies helped.  Now I know that I could have used slicks in those river beds.

Seriouser, I think that someone needs to figure out how to get more power to the ground.  Looking at old speeds, the B. Johnson Triumph liner did about 205mph on 65hp.  Rich Richards did 146mph on about 65hp unstreamlined (while taching 165mph), as did I.  Looks like we definitely got to the aero drag limit.  Look at how much horsepower you have now, and how little gets to the ground.  Try plotting horsepower versus speed (for the same class).  I just wish I understood some of this.

[JackD]

Street bikes are now going 250 +
Power helps, but they are learning to better apply less to go faster.
It not only has to last but be around long enough so they are learning to use it.
Tire science is pretty well established but not universally understood.
It is actually one of the most well kept speed secrets.

[EVLEE]

alot of those old records might have been set when they ran almost twice as far as they do now??
       Lee

[JackD]

alot of those old records might have been set when they ran almost twice as far as they do now??
       Lee

The distances for the bikes mentioned in SCTA, El Mirage, and Speedweek have remained the same and the speeds have gone way up for the faster classes.

[tomsmith]

In '52 we had 3 miles to accelerate, 3 1-mile traps (with 1/10 inside the first mile), then 3 miles to slow down.  The salt was hard - probably a lot better than now with good traction compared to the ruts at Rosamond dry lake.  We had it good.

I remember my first run - I cut off the motor and put it in neutral at about 140mph so we could look at the plugs.  Then I coasted and coasted.  There were no markers after the end of the traps so I had absolutely no idea how fast I was going.  I was afraid to turn off, since I didn't want to do any 130mph dirt tracking.  After what seemed like forever, I finally got the guts to turn.  I had probably slowed to 50 or so.

[Sumner]

I guess I am iggerunt or sumtin.  It looks like having tread or not on your tires is irrelevant so far as having traction on low coefficient of friction surfaces.  Gee, when I was riding desert I thought that having gnarly knobbies helped.  Now I know that I could have used slicks in those river beds.

Seriouser, I think that someone needs to figure out how to get more power to the ground.  Looking at old speeds, the B. Johnson Triumph liner did about 205mph on 65hp.  Rich Richards did 146mph on about 65hp unstreamlined (while taching 165mph), as did I.  Looks like we definitely got to the aero drag limit.  Look at how much horsepower you have now, and how little gets to the ground.  Try plotting horsepower versus speed (for the same class).  I just wish I understood some of this.

I think the tread has to do with: one the surface and two the effects of centrifugal force on the tires.  I don't think your knobbies would do any more good on the salt than they do on pavement (not good-especially if the pavement is wet).  A no-tread tire is best on "dry" pavement but a real mess if it is wet.  Probably some tire could be designed especially for the traction problem of the salt surface and maybe it already has, but it looks like the goodyear "land speed" tire just uses the pattern used with the drag tire that is designed for the front of a car.

Of course the other problem is the centrifugal force at high speeds and there again can you imagine trying to get those knobs to stay on a tire spinning at 300 mph and keeping the tire together.

Looks like for now we are stuck with what we have and personally I'm glad someone will make those.

Keep the observations coming and I liked the one about turning out and having a hard time knowing what speed you were going and all the other history from the past.  The more I think about it I'm really in awe at the speeds you and others made back in the 50's and 60's with the technology level those motors were at then.

c ya, Sum

[EVLEE]

I just saw the movie Worlds Fastest Indian  and In the movie they were timing (getting an average speed ??) at 8 miles and then coast down.I think they time till now till the 5th mile and then coast down?? I also think the salt was better and longer in the 50s and 60s from the people I have talk too!!
 I know The Buckeye bullet was still accelerating  as they say out the back door !! what if it had 3 more miles to accelerate??
  Just think in NASCAR they take 2 laps at Daytona to get up to speed that's 5  MILES on pavement !!
                                    Lee

[Stan Back]

Most good-running cars have a higher exit speed at the 5-mile than the 5th mile average.  The challenge is to try to reach the highest speed possible over the distance that is being used for comparison (or records).  Almost all vehicles could go faster at El Mirage if the course were longer, but the distance for acceleration has been standardized for more equal competition.

[Glen]

We ran 1- 1/2 mile at the 5 Muroc meets with little difference in speeds, El Mirage is still 1- 3/10. I was not at speedweek in 52 but the old hot rod or international course was longer over all and we had a lot more un farmed salt removal.

[tomsmith]

The Triumph I rode at Bonneville in 1952 got up to speed in about 1.5 miles, so I would idle along at 50 or 60mph for over a mile before I sped up.  I also rode a 1000cc Harley, which had problems on the first run so I don't know how long it would have taken to get up to speed.  I don't even remember what the problem was, but the frame was painted white.  At dry lakes less than 2 miles worked great for almost everyone.  Of course, we were a lot slower, with max speeds being around 170mph.  The motors probably wouldn't have lasted much longer than than anyways.

By the way, I saw some Dunlop Bonneville bike tires many years ago - I don't know if they were made before or after WW II. They had some nifty looking diamonds/pyramids for treads which were a little over 1/16 inch high.  I have no idea how well they worked.

[EVLEE]

I may be looking at Hankook tires that we use for SCCA road racing they are ZR rated racing tires and a little wider than I might like but I think they will get better traction .I will need to put all the power to the road I can get .I am looking to try and qualify (175 mph) for the long track in Sept. 2007 then reassess and hope to go for 200mph from there.I will have to see where the car is from spring testing and how the tires work then.
          Lee