NoHachi Wrote:I know some racing teams that experienced exactly the opposite.. The interesting question is WHY 17s were faster in some cases and WHY they were banned at all. Were they faster because of the bigger brakes that could fit under them? Superior traction? etc etc.

It could have been anything from better brake cooling to newer better tyre material. The brake rules didn't change so increase in brake size wasn't the issue , and going of the lap times it clearly showed more constant times lap after lap leading. Most likely it was just a stupid banning due to not being in OLD SCHOOL and fitting in with all the other dated rules.

NoHachi Wrote:Sorry but you are very wrong. With given tire pressures and vehicle weights, contact patch size is exactly equal for ALL imaginable tires. Think about it. If tire pressure is xx and vehicle weight = yy then contact patch size is always the same and equal to yy/xx. This is one of the most repeated internet fallicies you find. The only way to change contact patch size is to change tire pressures. (which is what they do for example in the desert).

Does the tyre always stay in this perfect postion ? no the tyre gets flex etc . A wider tyre will equal more area that given the tyre angle change or surface change in contact with the tyre has more chance of contacting with.

NoHachi Wrote:Again this is not correct people. pressure/cm2 is again exactly equal between tires. What does change is the shape of the contact patch. Narrow tires have longer, less wide contact patch that allows rubber particles to stay in contact with asphalt particles longer and allows for more time to squeeze the water out. That is why they are better in the wet.

I think time is unrelated to contact . The speed which the vehicle is traveling has more to do with time in that area of contact , in which more area will always equal more contact to a given rule of the vehicle weight effecting the pressure. Sure there is the fluid dynamics of water and lots of other factors like compounds etc.

NoHachi Wrote:Not correct. Wider tires actually can produce faster laptimes. For example, they reduce the friction experienced by the car due to turning. I wont go into details as I dont fully understand the elastic and dynamic behaviour of tires myself. Milliken&Milliken has a great introductory section that goes into this. I suggest you read it if you are really interested.
Less friction also means less force required at the steering wheel and less information arriving at the driver. Its all a trade-off..).

I have no idea how at low speed at the mechanical grip level more area doesn't equal more friction. I know trying to park with 225/45/16 over 205/50/15 requires alot more effort

NoHachi Wrote:Almost NO tire company does this kind of testing and releases the results. Whatever information you got with the R888s was most definately a very rough approximation, as true tire/force diagrams are not readable for 99.9% of the engineering community..nevermind the enthousiast.

I sure also Matt here has the same information on the R888 , if it was even a rough for most given vehicles is going to be a better starting with there information than nothing. Its not a race tyre its a club sprint semi slick so i guess giving information out would only produce more sales. Myself have used different setting in the alignment to which was given by them , but there settings work best so far. Sure i am not going out with data logging to later this year then there will be no approximations just real data. But going of the times there rough information is fine for most weekend track people out there , and switching from yokohamas i couldn't be more happy. Yokohama they give you jack information and there pricing.

Maybe it might be time to just keep the thread open to more feed back from people using 16" than all this random information with no real showing of results.

improvedae86 Wrote:I sure also Matt here has the same information on the R888 , if it was even a rough for most given vehicles is going to be a better starting with there information than nothing. Its not a race tyre its a club sprint semi slick so i guess giving information out would only produce more sales. Myself have used different setting in the alignment to which was given by them , but there settings work best so far. Sure i am not going out with data logging to later this year then there will be no approximations just real data. But going of the times there rough information is fine for most weekend track people out there , and switching from yokohamas i couldn't be more happy. Yokohama they give you jack information and there pricing.

Maybe it might be time to just keep the thread open to more feed back from people using 16" than all this random information with no real showing of results.

Yep i got all the info from toyo... gives u a good starting point...only reason i would go to yoko is if i wanted to compete in ipra in the future...

yep im yet to go to 16s.. so ill keep my comments out of this

Quote:The brake rules didn't change so increase in brake size wasn't the issue

Big brakes dont fit in small wheels ;-) Usually rim size rules are formulated to controll brake sizes, not to keep an OLDSCOOL feel.

Quote:Does the tyre always stay in this perfect postion ? no the tyre gets flex etc . A wider tyre will equal more area that given the tyre angle change or surface change in contact with the tyre has more chance of contacting with.

Explain to me exactlty how the rules of nature change and allow the wider tire to make contact over a bigger area..This is simply not true, the contact patch is EXACTLY the same size..sorry its just simple physics.

Wider tires require a smaller slip angles change to produce cornering forces. THAT is what makes the difference in lateral grip, longitudal grip, stability and driving feel. Contact patch size has nothing to do with it.

Quote:I think time is unrelated to contact . The speed which the vehicle is traveling has more to do with time in that area of contact , in which more area will always equal more contact to a given rule of the vehicle weight effecting the pressure. Sure there is the fluid dynamics of water and lots of other factors like compounds etc.

This is pure misinformation..sorry. See the previous point

Quote: have no idea how at low speed at the mechanical grip level more area doesn't equal more friction. I know trying to park with 225/45/16 over 205/50/15 requires alot more effort

Like I said..wider tires need smaller slipangles to generate larger cornering forces. The opposite is necessarily also true. If you need to generate large slipangles (parking) large forces are needed (effort). This is NOT a function of area but of slip angles.

Quote: Maybe it might be time to just keep the thread open to more feed back from people using 16" than all this random information with no real showing of results.

Sorry..but I will keep posting if people spread misinformation on the forums. These myths have been running around so long that most people believe them. As an engineer, that just doesn't sit well with me. Sorry if I sound harsh. I mean no offence, have no problems with anyone personally, but

I really think your reading far too much into this

The brake size on the N2 cars at that stage was locked at that stage
so going to 17" rims didn't equal people fitting bigger brakes.

If you want to go on about slip angles i suggest you read lots of Lotus's early 80's information on this. Mostly geometry and track , roll centers , camber , caster has far greater effect on slip angle than just tyre size.
Why do most manufactures bother with constant suspension changes on vehicles of the same weight ? why don't they just stick on larger tyres. Audi a4 series is a good example of this. Same rough weight , same tyre size but each model has small changes to the suspension geometry.

If people want a good basic idea on slip angle
http://en.wikipedia.org/wiki/Slip_angle

One point that is really missing , is the ae86 under-tyred to start with ?

"Wider tires require a smaller slip angles change to produce cornering forces. THAT is what makes the difference in lateral grip, longitudal grip, stability and driving feel. Contact patch size has nothing to do with it."

Where we commenting on the same width tyres not wider tyres?

Sorry if I sound harsh. I mean no offence but since you a engineer? maybe give us the maths on the standard car vs a 16' rims size car of equal width .If you want use suspension analizer , lotus or what program to get the results. Since the original question by the thread starter was on improving there braking performance it will be good to see the de-acceleration graph between the sizes.

I know its going to be worst without lots of changes , so maybe once again this thread should be related to people using 16" and the changes that they have made and there results

Quote:"Wider tires require a smaller slip angles change to produce cornering forces. THAT is what makes the difference in lateral grip, longitudal grip, stability and driving feel. Contact patch size has nothing to do with it."

Where we commenting on the same width tyres not wider tyres?

Your example mentioned tires with different widths, not mine. I just gave you the physical explanation of why you noticed heavier steering feel width with the 16inch setup. It is the force required to generate a slipangle on the 225 wide tire, not the contactpatch size.

Quote:If you want to go on about slip angles i suggest you read lots of Lotus's early 80's information on this. Mostly geometry and track , roll centers , camber , caster has far greater effect on slip angle than just tyre size.

Now you are just guessing... Maybe its better to first understand what each of these terms means before you throw them around. Everything starts at the tire and its slipangle characteristics. The rest of the car is designed so that it makes the best use of the performance envelope they allow. Honestly, you seem to have a serious interest in these matters; do yourself a favour and stop accepting dubious internet resources and start reading some proven references. You will not find these on the net but in a library. Sadly, the material doesn't lend itself well to a popular science type of approach, so a decent background in physics and mathematics is a minimum requirement.

Quote:the brake size on the N2 cars at that stage was locked at that stage

Any proof of this or just a guess? Link?

Quote:maybe give us the maths on the standard car vs a 16' rims size car of equal width

No I can't..that is the point I'm trying to make here. I've seen the calcs, have a masters degree in engineering, but am nowhere near qualified enough to do this stuff. It takes a serious specialisation in tire dynamics.

16s might be faster, they might not be faster. It needs some serious testing to determine what is the case and under which circumstances. Searching for opinions on a forum like this is a start, but adding misinformation to any of these user experiences is always a bad idea.

For a start please stop editing your posts , i logged in this morning am time melbourne read your reply and now pm melbourne time there more to it. It getting very painful to follow with the constant changing and quoting.

Sorry i am lost to what size you are talking about , but yes i run 205/50/16 for road and 225/15/16 semis for track. There is no steering effort change inbetween 205/50/15 and 205/50/16 that without installing a strain measuring equipment into the rack or steering shaft that i can physically tell.Saying that my feeling is that on the road you yes the 225 is a far bit harder to steer yes , but this only comes into its own on the track once the tyres are up to temp.

Why do i need to guess ? unlike alot of people that sit in there chair onthe interweb to come at there results, i am out there trying the size to see the difference. I don't know why you keep going back to slip angle ! when the thread is titled 16" ??

If anyone wants to really know any hard data on there slip angle they really should just plot all there cars suspension points and other information into software. there are loads of programs on the market. Be it suspension analizer to lotus's suspension program , to lapsim. There is no need for all this engineering background of full on maths and physics when many companys have gone to the trouble so there no doubt of what rims size effects.

Didn't i see that really people should be looking at the whole suspension package not just the rim size !! sorry to sound like a broken record again

I am guessing as i seem to do alot according to yourself that in whatever country you are in that you don't get the rounds of the N2 and a full rundown on DVD ? also i guess that you cannot read japanese or speak it. Since you have the time for such long reply's to my posts maybe spend some of this time to search it for yourself.

If you cannot understand it and you also haven't tryed it , and if you don't even own a ae86 by guessing about you log in name i really have no idea why you would waste you time here. Maybe go start a thread on engtips etc.

And even after that you have these experiences you still get might get flamed ! And last guess is a user ? a owner of a ae86 ?

Shame that you feel the need to get personal. Everytime I replied something to your posts it was based on the arguments you put forward in them. If you just have some user experiences to share then ok. Put forward wrong technical theories about the origins of the changes you feel and I will comment. This seems to offend you.

I keep coming back to slip-angles because they are KEY to this discussion. You cannot get hard data on slipangle from suspension analysers as they are a tire characteristic. They dictate the forces with which the tire reacts to the forces from the chassis. Consider it similar to the elasticity of materials. The deflection is caused by outside forces, but the amount of deflection is dictated by the elasticity modus. This elasticity (or the rate of slip angle change) of the tire depends on tire loading, speed, tire deflection etc etc. Again, you don't need to look at the whole suspension, its a tire thing! Change tire parameters and the slip angles change. Go to wider tires and the same force results in smaller slip angles. That's the reason of the changes you mentioned.

I'll leave it at that..the rest of your post seems to be a long rant and doesn't add anything constructive to this discussion.

I have shared the fact that i use 16" rims and what i have found so far !@
i really don't know what else you would like to comply to your idea of input ?

I keep coming back to my results are also with lots of changes to the vehicle and i wouldn't suggest just changing to 16" rims and tyres whatever width , profile etc. Why anyone would make the change and stay with the same width as standard is also beyond me.

And i still cannot get around why so many manufactures induce geometry changed to effect the slip angle? are all the engineers from lotus , porsche etc all stupid and cannot relate tyre and chassis together. Also why do any tyre testing if the information cannot be use to any use! Maybe there all stupid and need your assistance asap.

Before you add another KEY to this thread with a whole lot of more cut & pasting engineering comments please show me any data on slip angle change in a ae86 that i might be missing. It would be great to gain as many secong off adding 16" rims again with this ideal suspension set up for said tyres from someone with one

Lots of people have commented to me that this site has some very negative people that talk themselfs up all the time without really sharing or helping anyone in general. No names where mentioned but i am guessing they must have been talking about you. With views like this you might as well do us all a favor and stop acting like a hero because your far from it. I'll leave it at that....

Whatever, good luck

improvedae86 Wrote:Lots of people have commented to me that this site has some very negative people that talk themselfs up all the time without really sharing or helping anyone in general. No names where mentioned but i am guessing they must have been talking about you. With views like this you might as well do us all a favor and stop acting like a hero because your far from it. I'll leave it at that....

I think it's a shame you both are making it this personal.

From my own experience I know that NoHachi has a great knowledge about the theory of car engineering (guess what he's doing his masters for ) and I as well have made some silly arguments with him in which he (almost) always was right.
I think this is purly a matter of someone who does everything in practice versus someone who knows all theories and tries them on the circuit.

improvedAE86: even though his names says NoHachi, he sure does own a hachi:
http://www.aeu86.org/viewtopic/scuderia-...ect/t/3994

About the sharing of knowledge: did you ever take a look on the front page and see the Tech-FAQ/How-to sections? Have you ever bothered to look at the amount of topics (with replies) in the technical section? I mean, you just joined 19 days now while the community already started almost 3 1/2 years ago! I think you better start looking around on this forum, see other topics than the ones with NoHachi and get your own personal opinion.