Bridgestone Re92

[type26owner]

The yellow dot on Bridgestone tires produced in the US is the
low point of the tire.  When most wheels were made of steel
"match-mounting" was a very common practice.  Wheels were marked with a
high spot and tires were marked with a high and a low spot.  Since most
wheels are aluminum they are no longer stamped with a high spot and the
low spot is generally considered to be the valve stem opening.  The
yellow dot does not have to be clocked to any particular position and
is mostly there as a guide for balancing.  If the tire rides well the
location of the dot is irrelevant.

The mark is painted on so if you show the car and do not want it
there you can scrub it off or it will wear off in time with regular car
washes.

That's the reply I got from the Bridgestone folks. Since my new 4.5J steel wheels runout radially I think I'll indicate the high point and clock the tire accordingly from now on. Going to stamp the wheels with a letter punch to mark the high points permanently.

[mark030358]

Sorry,

what was that last post about?

Lost me totally.

Could you explain?.



Mark

[mark030358]

Sorry,

what was that last post about?

Lost me totally.

Could you explain?.



Mark

[type26owner]

Mark,
I posted the reply I received from the engineering folks at Bridgestone USA. Quality tires are marked with a colored dot on the sidewall which means something. Trouble is there is no uniformity between the various manufacturers on that meaning. I've seen yellow, red, green and voilet ones before. Knowing this information allows you to utilize the tire to the fullest by clocking the low spot on the tire to the high spot on the wheel in this case. This allows one to reduce the runout error. It becomes extremely important at the high rpms of the wheels. At 120mph the wheels are spining at a rate of about 1946 rpms. Since I'm taking these tires out on the race track and flogging them I'd like to have the greatest chance of not having a bad day. Just sharing that info encase anyone else might choose to try this tire.

[M100]

But is it going to make any difference at all? Best to get your rims running true in the first place - the tyres will even themselves out once they get up to temp and any flat spot goes away. Storing the car on transit wheels helps too.

All the competition tyres here in the UK I've come across aren't marked for any high spot so its probably just an American thing. Usually they were mounted, balanced, run up to temp and then check rebalanced. After that with careful attention they were usually good for the life of the rubber and they've been run on vehicles that were going in excess of 150mph on races lasting many hours.

Also I question how you get a "high spot" on a tyre that should be moulded round in the first place and how this is determined without mounting the tyre on a rim in the first place.

[types26/36]

<!--QuoteBegin-M100+May 27 2005, 09:01 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (M100 @ May 27 2005, 09:01 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->

All the competition tyres here in the UK I've come across aren't marked for any high spot so its probably just an American thing.  [/quote]

I agree about getting the the rims running true first but back in the 60's the normal road going tyres had a red dot which was supposed to mounted be next to the valve, this was in the U.K.
I'm sure tyre tecnology has moved forward since then and is probably not required for street cars now but would think it is still used for racing applications.
Brian.

[type26owner]

Please tell me how that is possibly to be done. The wheel centers are welded in a continuous bead to the rims. The drive pins holes are lug-centric and are what do the centering of the wheel to the hub. What you get brand new is whatever runout results from the warpage of the welding and the fixturing errors. These wheels are quite clearly not trued in anyway after the welding process. Dazzle me please!

As far as it being worthwhile, how would I know that until I tried it once? There is an annoying little dithering of the steering wheel which would be nice if it went away. After twenty minutes on the track it makes my hands go numb gripping the wooden steering wheel.

Tire technology is fascinating stuff. The stack tolerance errors of the many components of a radial tire are small but are still relevant. The low spot is measured in a robotic device which takes every tire in turn and inflates it onto a precision spindle and then runs it up against a rolling road. From this all sorts of information can be gathered like the highest radial spring stiffness spot or the physical low spot. Commonly there are different colored dots to mark both locations.

[type26owner]

After dial indicating the bead seating area diameters for runout to find the high spot on the welded steel wheels I purchased a few years ago I found there many high spots on each bead. They resemble an old fashion washboard in fact. The ripples are 1mm high and are about every 45 degrees. Clocking the yellow spot to the the highest point on the wheels is a joke. I'll be purchasing alloy wheels in the near furture.

[DrEntropy]

...and a tyre trueing machine too??

Could you imagine trying to "nobble" the steel wheels into compliance? Alloy is a much better idea, albiet a bit pricey. At least there'll be less excuse for claiming CTS ;-}

P.S. -- Just got a DSL connexion. No longer among the "Great Unwashed"!! Now I can mecunicate with ease.

[M100]

<!--QuoteBegin-type26owner+May 29 2005, 02:42 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (type26owner @ May 29 2005, 02:42 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> After dial indicating the bead seating area diameters for runout to find the high spot on the welded steel wheels I purchased a few years ago I found there many high spots on each bead. They resemble an old fashion washboard in fact. The ripples are 1mm high and are about every 45 degrees. Clocking the yellow spot to the the highest point on the wheels is a joke. I'll be purchasing alloy wheels in the near furture. [/quote]
Keith, If you can detect 1mm highspots on a wheel rim by the seat of your pants rather than with the use of a dial gauge then can I suggest you ought to be petitioning your government to supply a few million granite surface plates to drive on?

The vibration you would getting through the wheel by 1mm peak variations in the rim every 45 deg is infinitesimally smaller than you would get from a few road chippings stuck in the tread or a missing balance weight. If you have other vibrations or shimmy felt through the wheel then address problems in the suspension and steering linkage. Throw out the old steering rack with worn out pinion and rack teeth, buy new uprights and trunnions, replace the rubber wishbone bushes with new ones (or even better go for custom made uprights with rose jointed links) - or just lay off the bottle a bit

While I agree the Elan steel wheels are "as built" they can and do go out of shape with use (and abuse) Application of a Mk1 adjusting tool projected at a suitable velocity in the right direction can bring them back to true at least for all practical purposes.

I seem to recall someone (maybe you?) mentioned tyres moving on rim recently, a good grit blast and powder coat (except the seating area) would probably help.

[type26owner]

M100,
Best guess this is classic problem of resonance. The ripples are at the right frequency to excite the natural frequency of the tires. They are literally ringing very similiar to what a tuning fork does. Having periodic undulations of the same amplitude is usually a very bad clue.

A little less attitude would be prudent on your part. Hopefully you're just teasing me. Yes?

[type26owner]

Dr E,
Quite common to have a problem of this sort actually considering the complexity of a radial tire's construction. It's usually do to a steel cord shifting or some defect in the tire and not the wheel though. Shaving the thread true will not help here. These tires typically only have a runout of 0.5mm anyways. Bridgestone is definitely setting the bar higher with their quality controls these days.