20 replies to this topic

[kober]

New asphalt layer is just being put on our street and this made me think - is there any difference between normal asphalt used on streets and asphalt used on racing circuits? I think I've heard something like 'racing asphalt' before... Is the difference in the material, technology or both? I've seen a few circuits surface, but I can't generalize in this - but it seemed a little bit different.

[RDV]

.....like anything in the world, it depends....

Some tracks have specially formulated asphalt, (Silverstone when re-done in the 80`s , MagnyCours) some tracks have the local mix.

As a sideline to the question, Michelin did a sampling of all racetracks by tacking cores from all f1 racetracks to analyze composition and grain.

Magny Cours a good example of FUp as nominally asphalt mix supposed to be medium grip, but something wrong in mixture, whole track had to be re-surfaced because came out very low grip, initial tests with F1`s in 89 in winter had cars spinning on straight if full power applied...

One observation = from a lot of races in different countries, apart from airport circuits and obviously road courses Like Monaco, Pau, Long Beach, Spa, the bumps, asphalt and grain of any race track is very similar to local roads.

[ray b]

grip can be adjusted by additions to normal mix BUT sometimes things donot go according to plan
local expressways were redone with a rubber added mix to help wet traction but it turned out to be a extra slick mess in the rain like oily ice and was quickly replaced.
it is more of a black art then a exact teck yet!!!!
but bumps should be cut out by new milling machines that we use on local streets to cut off top layer and leave smooth surface, I think even the indy oval was milled this year resulting in faster times!!!

MY latest idea is different grips from varied pavements to create multi-line corners for more passing on narrow tracks along with a tyre rule limiting marbles so multi-line passes will be possable

[AS110]

Our local track apparently had rubber in the mix (20yrs ago) I was amazed at the grip my bike had compared to an ordinary road,equaly amazing was the lack of grip when it rained!

[random]

Most of the US road courses I've seen end up putting concrete patches in the corners after a few years of use. It's a cheap and horrible way to fix a track.

The grip change is dramatic and in the rain it's quite dangerous. Even some of the best attended US tracks like Mid Ohio have concrete in nearly ever corner.

[Melbourne Park]

When one thinks about it normal roads need more traction than a race track. Racing teams can figure out the track's limits, but below average cars and drivers need all the help they can get.

Of course the reality is that there's a clear difference: a race track is a couple of miles of specialised track, is very well graded and needs to be smooth. A normal road is much longer and uses much more materials, and is part of some form of large road building contract. So the normal road is going to be much more price sensitive than the race track, and hence lower in material quality.

If I had my way though I'd like speed bumps in lots of the corners. That would force suspensions back into F1, and remove much ground effect, hence increasing overtaking. Also more relevent to normal driving.

[Yelnats]

Melbourne Park, your comment about normal roads needing traction more than race-tracks is a good point. As a pavement designer I spent some of my time selecting suitable asphalts and the over-riding consideration was cost. Obviously we could justify spending more for a high speed freeway than a local road where speeds and volumes were much lower. A race track obviously can afford the best but seldom gets what it deserves.

What is good for a public road will be good for a race-track so heres a few paramaters to consider.

Rubber is commonly added to asphalts because it was mandated by some States in the USA as a method of disposing of tires. This has some benifits in reduced cracking but is unpredictable and better achieved by the use of high quality Asphaltic Cement and Polymer additives These increase the temperature range of the asphalt to avoid softening at high temps and cracking when cold.

Rubber will have no benificial effects on traction as this is produced by the aggregates in the mix which stand proud of the surface as the softer asphalt/rubber mix wears away. An aggregate that is very hard and has a good micro-texture like Trap Rock and Dolomitic Limestone (Ontario Canada) will perform best as it will not polish with traffic.

If there is too much Asphalt Cement (The tarry stuff) the surface will 'flush' and become shiney and treacherous when wet because there is no channels for the water to escape through and the speeding tire lifts off the road surface to produce the scary phenomenom of Aqua-planeing.

Several experiments are underway (Monza) with an open textured asphalt that lacks the finer aggregates, consisting of coarser pieces of agregate glued together with ashalt to form an 'Open Friction' asphalt like that used on urban freeways in Ontario for the last 20 years. This dramatically reduces surface water and cuts spray by 80% but is tricky to design and lay and may not be avalable in all countries or locals.

The disintegration of new pavement one sees at the occasional racetrack (Mosport has wheel track patches in it's one year old pavment) is caused by the use of inferior aggregates and Asphalt Cements and which probably consisted of your local driveway mix which looks nice and black but has little else to reccommend it.

[Cory Padfield]

Yelnats -

[RDV]

.....it is more of a black art then a exact teck yet!!!!

....just like tyres!! not surprising as is the interface that does all the work...

[Yelnats]

Originally posted by ray b
grip can be adjusted by additions to normal mix BUT sometimes things donot go according to plan
local expressways were redone with a rubber added mix to help wet traction but it turned out to be a extra slick mess in the rain like oily ice and was quickly replaced.
it is more of a black art then a exact teck yet!!!!
but bumps should be cut out by new milling machines that we use on local streets to cut off top layer and leave smooth surface, I think even the indy oval was milled this year resulting in faster times!!!

MY latest idea is different grips from varied pavements to create multi-line corners for more passing on narrow tracks along with a tyre rule limiting marbles so multi-line passes will be possable

The Indy track was diamond ground (not milled), a process usually reserved for bumpy or slick concrete. Diamond grinding (in the case of Indy) consists of passing a machine with hundreds of closly spaced (12mm) high speed diamond cutting wheels under the control of a laser sensor over the track surface. The resulting finish has thousands of closley spaced grooves which is much smoother than the irregular finish produced by mulling machines with their widely spaced carbide teeth. A milled surface can only be driven on for short periods as it must be paved over for everyday use.

[12.9:1]

All well and good, but if you REALLY want traction - one word,GLUE
No really, some time ago dragstrip owners started using track treatments (glue)
so that thay might claim, speed records for their facility.
This stuff is STICKY, and in addition to producing 5g launches (Top Fuel)
It'll pull your shoes right off !


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[ray b]

12.9 that brings back memorys of 60's slotcars we used many kinds of goop on tyres

yelnats I used milling as a general term for machine smoothed pavements
but steets are repaved after milling localy
can the grooves be varied to give different grip levels in the diamond system??
does grip level affect pavement coming up[breaking up] in corners??
does older pavement breaking up or is that a new fresh pavement problem only???
how does grip change as pavement gets older??

[Melbourne Park]

Originally posted by ray b
12.9 that brings back memorys of 60's slotcars we used many kinds of goop on tyres

yelnats I used milling as a general term for machine smoothed pavements
but steets are repaved after milling localy
can the grooves be varied to give different grip levels in the diamond system??
does grip level affect pavement coming up[breaking up] in corners??
does older pavement breaking up or is that a new fresh pavement problem only???
how does grip change as pavement gets older??

Maybe GPS systems one day could be integrated with ABS information and reported to road authorities, maybe via a service outlet or in car internet connection; so the road builders could spend money on areas where the cars are braking heavily, I am presuming there would be a strong positive correlation between ABS activation and road accident spots ... Such equipped cars could also advise the driver of "hot spots" or danger driving spots by recognising from their GPS and an internal database and maybe traffic conditions and even driver behaviour such as speed, that caution was required ...

I went to the movies last night and next week there is a Sci - Fi film festival. It must have affected me in some way ...

[AdamLarnachJr]

Brilliant idea.

[12.9:1]

MY latest idea is different grips from varied pavements to create multi-line corners for more passing on narrow tracks along with a tyre rule limiting marbles so multi-line passes will be possable

Excellent ray b

I too have meditated on multiple line road racing, I was thinking mostly about varying bank angle but now I see the light !
Perhaps some angle could be used, from - to +, then to fine tune the surface, you could start with a smooth low-grip pavement, and vary the number of groves per meter, to arrive at - I think two discrete lines. Other wise the car in front might camp out in the center position.
This can work !


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[Yelnats]

Originally posted by ray b
12.9 that brings back memorys of 60's slotcars we used many kinds of goop on tyres

yelnats I used milling as a general term for machine smoothed pavements
but steets are repaved after milling localy
can the grooves be varied to give different grip levels in the diamond system??
does grip level affect pavement coming up[breaking up] in corners??
does older pavement breaking up or is that a new fresh pavement problem only???
how does grip change as pavement gets older??

a) can the grooves be varied to give different grip levels in the diamond system??..... The grooves must be placed close together so the small areas between the cutters fracture off during the cutting. This leaves little room for varying the diamond grinding pattern but I suppost the wheels could be moved closer though I am not sure what effect this would have on traction. A better solution would be to polish the pavement after grinding if reduced grip is you aim. There are surface polishers designed for floors that would do the job, though the expense would be very great and wet pavements would be treacherous!

b) does grip level affect pavement coming up[breaking up] in corners??..... It must have a big effect as we seldom see such rapid deterioration in road pavements. I think its a case of the aggregates being pulled from the surface by the sticky tires during hot weather. Any properly design asphalt should resist this but I'm afraid that race tracks have no specifications to guide their selection of asphalts so the lowest bid often wins. Thus they get rounded aggregates and low temperature range Asphalt Cement when proper specs would demand crushed rock and Polymer modified AC.

c) does older pavement breaking up or is that a new fresh pavement problem only??? ..... The problems we see in race tracks are usually in newer pavements. As pavements age the harden and the aggregates become more firmly embedded. Of course as pavements reach 15 or twenty years old they may become brittle and freeze/taw cycles can dislodge aggregates but theres very little traffic on a race track in the winter to cause this deterioration!

d) how does grip change as pavement gets older?? .... Grip falls after a time on public roads (depending on the hardness of the aggregates) due to polishing of the aggregate but these effects on race tracks are very subtle due to the soft tires (pressures and compounds). Winter traffic and sanded roads in Canada accelerates the polishing effects. Mosport's pavement (an ex-F1 track in Ontario) was almost fourty years old before it was resurfaced in some areas and the grip level was fine. Note that new pavement failed in the wheel paths in one year!

[12.9:1]

posted by Yelnats
can the grooves be varied to give different grip levels in the diamond system??..... The grooves must be placed close together so the small areas between the cutters fracture off during the cutting. This leaves little room for varying the diamond grinding pattern

Over here (Southern California) there are hundreds of miles of highway with very distinct grooves, I believe that, at intervals cuter wheels are set to cut deeper resulting in smooth and grippy pavement.
Incidentally, originally only grooves were cut (no leveling) and only at areas with high collision historys, this in the 1970s



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[lateralforce]

At Mid-Ohio a lot of the corners are patched with concrete..more grip than the asphalt during a hot dry day, but once it starts to rain, racers try to avoid them..(it's interesting to see the changing racing line when it's getting wet).

[random]

At Montreal, new pavement was put down in a number of locations and it obviously wasn't up to the standards used for the original paving.

The inside of the first corner was widened due to the new placement of the pit-lane exit. The inside of the corner was inspected by FIA representatives after every session, and obviously was peeling up.

When we arrived at the track for the Sunday warm-up, 3 concrete patches had been placed on the inside of the corner.

[Yelnats]

Concrete is often used for quick-fixes even though it has the disadvantage of a different co-efficient of friction. This is because it requires no heating or compaction and can be placed by a few persons with a trowel and leveling board after a groove has been milled in the offending pavement. High quality asphalt is difficult to acquire in small quantities and compaction in narrow trenches is difficult to do well. Quick-set cement can harden in an hour so the work can easily be done on race weekend.

[John Galt]

Originally posted by Yelnats
Concrete is often used for quick-fixes even though it has the disadvantage of a different co-efficient of friction. This is because it requires no heating or compaction and can be placed by a few persons with a trowel and leveling board after a groove has been milled in the offending pavement. High quality asphalt is difficult to acquire in small quantities and compaction in narrow trenches is difficult to do well. Quick-set cement can harden in an hour so the work can easily be done on race weekend.

Sebring couldn't be bothered with it.