Looking for Information

[mrflamewerks]

I’ve been researching going to the Darkside. I’ve read reviews, various threads on the subject, evaluated numerous tires, etc., and even went so far as starting a thread on another motorcycle forum. My research has answered a lot of questions, but still leaves some gaps in the data. Perhaps somebody can steer me to the information I’m looking for.

•Is there information on the mechanics of radial tires available somewhere that graphically explains how a radial functions dynamically? What I am trying to determine in particular, is how much of the contact patch stays on the pavement in a hard turn at speed? How about in a slow turn?
•How well does a motorcycle respond to emergency evasive action with a Darkside tire?
•If punctured and flattened, are they “mushier” than a motorcycle tire?
•What is the reasoning behind running a 205/(55/60/65)R16? Would a 195/65R16 or similar narrower tire work as well?

Thanx.

[Valker]

Look here: http://www.totallypissedoff.com/Darkside/darkside.htm
Do a youtube search for  "car tire on motorcycle" or "darkside" and you will find videos of what you wanted to know.

[PJH]

You're not going to find anyone on this board who is really an expert on this.  You're going to find a lot of opinions.  Most of them will be in favor of the 'darkside' because that's in style here.  The opinions will be based on experience of having used a car tire for N miles and I'm not dead yet.  There is some validity to these opinions based on experience but it's not conclusive.

You will not find anyone here who can speak lie any engineer about forces and stresses in play much less anyone who has actually designed a car or motorcycle tire.  So beware of much hot air.

People who understand tires from an engineering perspective and those who have designed them invariably work for tire companies.  After all that's who hires people with that expertise.  It is in style here to dismiss information from various manufacturers as shills - "Of course they're going to say that.  They just want our money."  Fine.

I don't care what kind of tire you use.  You can use extra large condoms for all I care. You're asking for data that doesn't exist here, so you're only going to get uninformed opinions.   Why don't you ask the tire companies and at least take their data into consideration.  You can dismiss the least convincing sources. 

[mrflamewerks]

You're not going to find anyone on this board who is really an expert on this. 
(edited)

I didn't expect to find experts here, although it would be nice if I did. However, I am hoping there would be someone here who knew where to find technical information that was not slanted one way or another. I have found some on my own, and now know more about the operational dynamics of tires than I'd have ever expected. Pretty intersting stuff actually.

Thanks to Valker, I did come across a good VIDEO.

[Valker]

You're not going to find anyone on this board who is really an expert on this. 
You will not find anyone here who can speak lie any engineer about forces and stresses in play much less anyone who has actually designed a car or motorcycle tire.  So beware of much hot air.

People who understand tires from an engineering perspective and those who have designed them invariably work for tire companies.  After all that's who hires people with that expertise. 

Most of what you say has validity...however, you may be surprised. My father began working for Dayton Tire and Rubber in 1959. I grew up around the design engineers. He worked in 'adjustment' for a decade or more. I worked in tire failure analysis for a few years, but not design. I was involved in the early days of auto tire radials as far as the early 23 degree, 10 degree, and zero degree carcasses, steel, Aramid, nylon, and Kevlar belts as well as some other areas mainly involving heavy truck tires. I am not sure what you would classify an 'expert' as, but again, you may be surprised by the vast array of knowledge available on any particular subject. ;)

[mikehallbackhoe]

I too am interested in this subject. rather than listening to engineers or tire designers, I would like to hear from someone who has actually ridden with  a narrower tire. how did it handle?  the advice found on this forum may not always be based on absolute facts, but it is usually based on honest opinions , and often from actual experience, which is good enough for me. I for one appreciate the information found on this forum, and know that I am free to choose for myself whether I use  this information, or disregard it.

[PJH]

Valker has more expertise than I expected to find here.  I'm still leary of taking advise on a  safety oriented issue from some unknown genius on the web.  There is absolutely nothing stopping me from proclaiming that I am a tire engineer with decades of experience in design with a specialty in motorcycle tires, but, since I am an independent consultant my judgements and opinions are unbiased and beyond questioning.  Having made that proclamation I could espouse the most outlandish concepts, and who could argue.  Why, I think you should get extra large balognas and wrap them around your rims - I saw it once in the Stooges.

I'm just saying be careful, look for opinions that disagree with each other.  Weigh the information agains each other.  Don't be led like a sheep.

[Sludge]

Valker has more expertise than I expected to find here.  I'm still leary of taking advise on a  safety oriented issue from some unknown genius on the web. 

Um, Peter, not to be an arse... not flaming ya... , but why ask a question here if you wont accept any of the responces.  I mean, your asking a question on a public forum, then you immediately discount any opinion you get.  I dont quite understand that.  All you can expect on a public forum such as this where everyone is an "unknown quantity" is simply an opinion.  Many opinions here are from experience though.  Valker, in my experience has given thoughtful, reasonable, and well thought out responces in the past.  There are surely some here like myself that dont know their arse from a hole in the ground, but there is alot of good experience to be found both here and over at the VRCC site. 

Here comes my opinion LOL 

I got my darkside tire just for one purpose.  A drag strip.  I was supercharging my valk and I wanted something to grab the pavement with as large of a foot print as I could get.  I was VERY suspicious of the car tire concept and actively argued against using one the first time I ever heard the discussion.  I thought everyone using one had to be flatlanders that never rode curves very hard, or did all interstate driving.  So, I get my car tire expecting to buy a second rim and mount a bike tire on it for my general riding.  I was curious enough to go out and experiment with the car tire though.  Very much to my surprise, I had been completely mistaken about the handling characteristics.  The loose rear end up on the corner of the tire, and all the other flaming death senarios I had envisoned didnt seem to fit what I was then feeling.  After about 500 miles on the car tire, I started getting more agressive on it in the twisties.  I live in the NC mountains and so I have access to some agressive roads.  As it turns out the tire did well in all aspects.  I have absolutely railed this thing through places like shady valley with no problems, going far beyond simple peg dragging all the way to the limit.  Dragging the hard parts that dont move.  Absolutely no chicken strip left on the front tire.  It was solid in all areas.  Stops on a freaking dime too.  It way out performs the bike tire in that reguard.  Wet handling is superb.   I have heard about them trying to follow lines in the highway, but mine hasnt done it any worse than the Dunlops that were on it previously.  I think some of that has to do with tread pattern.  My preference in a car tire for my bike is to have a nicely rounded edge like the Yokohama ADVAN A048 that I am currently running  or that of a Cooper Zeon 2XS etc.  Also, I dont want a standard car tread pattern with straight grooves in it.  I prefer the directional aqua tread patterns.  The only negative that i can think of and it really isnt a negative to tell the truth.  Just a different feeling.  Is that mine takes slightly more countersteering pressure to really throw her into a turn than it did with the bike tire.  Not even noticable unless I switch bikes or something.  I grew accustomed to it very quickly. 

Now, that is a report from an expert test pilot ... on MY bike and with MY tire.    I too would love to hear an un-biased report about the shear forces etc that you mentioned from some official outlet, but I doubt anyone will ever give one due to a fear of legal entanglements.  So, just sit back and enjoy all the opinions.  And if ya get a chance to come to INZANE or something.  Go riding with Smoking Joe or some other darkside mountain riders.. You can get a first hand view of how they handle the twisties...  if ya can keep up  ;)

[mrflamewerks]

What I find particularly interesting, is that so far the only negative I've run across regarding this mod, is a story posted on the Mythbusters thread that sounds more like a case of operator error than equipment failure.

...and I quote...

lordfrogenhall

"I was almost killed on a Gold Wing because someone had put a side hacker tire on the rear. For those of you who don't know, a motorcycle set up for a sidecar has a tire like a car tire, square-shouldered edges. The motorcycle tire has a rounded configuration, to have the same amount of tire on the road, even when turning. I got into some sand during a high-speed maneuver, and the square-shouldered tire lifted up on one side, which reduced the tire on the surface to a very small patch. the sand then acted as a lubricant on the asphalt, and the rear end tried to pass the front, and I high-sided".

For openers, wouldn't a tire meant for a side car be a bad choice for a Darkside conversion? Secondly, it sounds like he (she?) was on unfamiliar motorcycle exceeding their skill level.

At any rate, it is interesting that I have not run across one posting by a Darksider (or ex-Darksider) saying it was a bad experience and they'd never do it again.

[ossvalk]

I would be having some issues with my Toyo Proxes T1R

I do love it on the highway, It sets up on the sweepers nicely and holds with a surer footprint than the dunlop or metzlers ever did  I dont feel tar snakes at all  Hevent ridden it in the pouring rain or snow yet but one of the reasons I chose this tire was following a 2 up rider in Va with this tire on his Valk  I got to see it from behind in the rain and it was surer than my metzller on the roads from Bristol to Tazewell and back

Now the downside

We have very rutted roads in the nYC area and it is harder for me to set up low speed turns. The tire wants to sit in the ruts at lower speeds especially.

We also have some windy roads (like the goat trail in the video I posted) that have been strip paved and the car tire (or is it me) handles differently  not worse  differently  I dont feel any slippage like on the metz though and that is a good thing.

So since I have not had the cajones to scrape pegs ...yet and I am riding like a big pussy while trying to get my confidence back after my crash in October I probably am not the best person to take advise from

I will keep this tire on for the trip to the Powwow in May and if I have not become happy allaround I will put the new avons on when I go to americade or after the ride to south dakota.  If I am still not sold by Inzane this tire will not be on the Valk.

YMMV   Oh yeah I run 38lbs now in the tire  41 in the front Metz

[Valker]

Oss,
Experiment a bit with pressure in the car tire. I had a lot more trouble with rut tracking on the HydroEdge than my other car tire at the same pressure. I dropped mine to a bit under 30 and all that went away. I like it a LOT better than my Yokohama now.
If I load it heavy (I mean heavier than me and gear) I will up it to 30, but that is about it.
Ride safe.
Eric

[mrflamewerks]

If anybody has pictures that compare contact patches or knows where some are posted, would you be so kind as to post the pics or a link?

Thanx

[PJH]

Well, Sludge, you raise a good point.  I should tell you a bit about where I hang out on the web.  I have two motorcycles (well, three if you count the CB750 semi-permanently buried in my garage):  a '99 Valk IS with sidecar, and a '99 Ural.  The bikes serve two very different purposes.  The Valk is dead-nuts reliable and is for long distance travel.  The Ural takes a lot of tinkering, is just for around town use, and is more fun than a barrel of monkeys.

Anyone who has a Ural has seen every one of the bike's internal parts, or soon will.  Over the years Urals have become more and more reliable, but they don't yet have Honda-like reliability.  People buy Urals for different reasons than they buy Hondas.  I think, sludge, that you would enjoy a Ural - you seem to like to get inside your engine.  I've done a complete teardown and rebuild of the engine twice.  I've seen the inside of every component except the final drive.  I do all my own work.

There is a web chatboard for Urals http://imzwa.secureforum.com/.  It's very active and there is a big community.  There are real experts there.  There's even a University of Washinngton mechanical engineering professor.  There are several other engineers.  There is a former owner/manager of  a small auto parts company.  There are many machinists and mechanics.

Every couple of years a group of these experts get together and travel on their own dime, not a company junket, to the factory in Irbit, Siberia.  The Ammerican market is so important to the company that these guys are given the run of the plant.  They talk to the engineers and designers.  The watch the manufacturing processes and make suggestions.  And they're shown prototypes, developmental models and not yet introduced products.

When they come home they post about their trip on the chatboard.  A lot of it's just travel stories - dinners and sight seeing and so on.  But they report quite a bit about the factory visit.

There is  shop manual for Urals, but it was written in Russian and translated into English.  The drawings are hard to decipher.  The manual was written for a Russian domestic model no longer being produced, but it's the best available from the company.  Heck, it doesn't even describe the carburettors on the models imported here.

So, one of the chatboard members took it upon himself to write a repair manual complete with photos and post it on the web - http://www.myural.com/.  You might want to browse it.

When a design and engineering question comes up, it's answered by designers and engineers.

Compare that to the content here.  Many of the technical questions are "How much should I pay my Honda dealer to do this or that service?"  Sure, some people, like you Sludge, have been inside their engines, but most have only the most cursory idea of what's going on inside. 

I was surprised that Valker has some expertise about tires.  Good for him, and I'm glad that he finally gave his bona fides for advocating using car tires.  Now we have some basis on which to judge the quality of his advise.

The fact remains, though, that there have been no engineering studies done about using car tires on motorcycles, no one has consulted with the tire manufacturers to get their take, and the only information available here is anecdotal.

So, now I'll go back into lurker mode.

[Valker]

I was surprised that Valker has some expertise about tires.  Good for him, and I'm glad that he finally gave his bona fides for advocating using car tires. 
The fact remains, though, that there have been no engineering studies done about using car tires on motorcycles, no one has consulted with the tire manufacturers to get their take, and the only information available here is anecdotal.

So, now I'll go back into lurker mode.

You misunderstood me if you think I'm "advocating" using car tires......I just told you that I do. I was only answering your assertion that there is a low level of expertise on this board. As to "no one has consulted with the tire manufacturers to get their take", some have indeed contacted tire manufacturers about this issue. Some have been told that the side forces exerted by a leaning vehicle which weighs about a ton can not physically apply enough force to be of consequence on a car tire designed to withstand several tons of weight and side forces approaching 1.5 Gs of lateral force. These engineers will not speak on the record as they are employees of companies who do not wish to endorse the practice.
I am not flaming you, I just want you to know that you may not have the correct assumptions about some of your assertations. ;)

[Sludge]

PJH, dont take my comments as being harsh.  No need to go into lurker mode.  I said that stuff with tounge in cheek.  Also, like Valker, dont take my experiences with the darkside as an endorsement.   I tell my experiences not to propagandize, but to dispell some of the myths and inform what little knowledge of this that I have.  I would truely love to see some kind of measurable test performed to quantify the contact patch profiles etc. 

My feelings on the darkside are that each rider needs to access his own needs and come to a decision about what he wants to do.  Had I not supercharged my bike, I probably would have never put the car tire on.  I put it on with a specific purpose in mind and ended up getting an education in the process.  On this bike, I wont likely take it off.  On the Goldwing, im on the fence about putting one on that bike.  I get quite a bit more agressive with it than with the Valk in the twisties.  Ive had the Valk all the way down with the darkside thats on it now, but I dont tend to take it to the limit like I do the Wing.  With the Valk, my thoughts are more on raw accelleration and performance.  The Wing?  I dont have alot of myself in that bike.  No personal connection like I have with my Valk.  And, I tend to treat it a bit more harshly.  I abuse it more, drag it more, beat it up more, because I dont value it as much.  I love my Valk.  I simply like my Wing.  It serves a purpose and nothing else.

So far as the Ural goes.  Yea I do enjoy wrenching on my Valk.  Its my toy.  Its my one hotrod.  its the indulgence I allow myself.  I have considered the Ural and its sidecar previously.  Seriously considered it.  I decided against it.  Ive got ATVs for off road, and I have the Wing for touring, and the Valk for my muscle fix, my tinker toy and my prize.  Any wrenching beyond that I want to avoid.  I honestly get enough of that with my (3) pickup trucks (9) road tractors & tandum trucks, (6) farm tractors, boom truck, mixers, pumps, etc.  I hope ya understand.  The Ural certainly has its appeal.  However, if another bike were to enter the stable, it would be something like a KTM 640 Duke etc.  A stripped down dirt bike for the road.  "Super Motard"  Built with only one purpose... to carve up the twisties.  Something to get down and drag your knee on and embarass liter bikes.  However, my fat arse dont need to do that stuff.  Im trying to wean myself off of my love of the twisties because I dont heal up and hair over like I used to.  A bike like that would spell my end im afraid.  Im prone to search for the edge, whether its being a Marine, flying a plane, riding a bike or driving a car.  Its a personality flaw I think.  I try not to encourage it no more than I can help.  ;)