Double Darkside

I've seen some chat on other forums about using a motorcycle rear tire mounted on the front wheel of the Silverwing. The tire is the same size -or pretty close- as the original OEM tire.

So I'm curious as to what the advantage of doing this might be.

Evidently it is not using an automobile tire (ie. Sumitomo) to replace the front --it's using a m/c tire that was originally designed for rear wheel use on a m/c to replace the front tire on the Silverwing.

Maybe it's my naivete', but other than tire size I didn't know there was a difference between front & rear tire designs.

A rear tire on the front?...can anyone shed some light on this for me? What's the advantage / disadvantage?

I've had great success with the Sumitomo tire on my scoot, and it's now time for me to be keeping a close eye on the front tire.

Tim
'03 Silverwing, Cosmic Jumper
Philadelphia

You can go to any of the motorcycle tire makers and read about the way they are made.
Both the front and rear tires are directonal and should be mounted so the arrow is in the directon of rotation. The front tire is designed so it can take more force under braking. The rear tire is designed so it can take more force acceleration. I personally dont believe in using a tire designed for a car on a motorcycle. that has very different riding style.
Paul

I know my diablo front tire has a groove going through the center of the tire to cut through water that the back tire doesnt have. Im not sure if all tire sets are like this but for the ones that are it seems like youd lose traction in wet conditions even with the added contact surface. I would imagine it would be smoother and grippier in dry conditions but more risky in the rain.

Cosmic_Jumper wrote:

I've seen some chat on other forums about using a motorcycle rear tire mounted on the front wheel of the Silverwing. The tire is the same size -or pretty close- as the original OEM tire.

I was the second person to switch to the Sumitomo a little after W1ngman.

I found the Michelin Gold Standard tire that fit the front and documented it on the silverwing.org site which knightrider later installed. I have my Michelin Gold Standard in my garage waiting for the front tire to wear down.

So I am an early "adopter/pioneer" in this area. I also did a lot research and reading on the "double darkside" information.

Here is the Michelin Gold Standard information sizing information

Michelin Gold Standard does not have a 120/80-14 but they do have a
140/70-14 rear tire ... here is the tire
math ( http://www.discounttire.com/dtcs/infoTireMath.dos
)

120/80-14
Sidewall Height: 3.78
Section Width:
4.72
Overall Diameter: 21.56
Circumference: 67.73
Revs per
mile: 935.48

140/70-14 rear tire
Sidewall Height: 3.86
Section
Width: 5.51
Overall Diameter: 21.72
Circumference: 68.22
Revs
per mile: 928.7

Difference
Sidewall Height: 0.08
Section
Width: 0.79
Overall Diameter: 0.16
Circumference: 0.49
Revs
per mile: -6.78

Cosmic_Jumper wrote:

So I'm curious as to what the advantage of doing this might be.

Evidently
it is not using an automobile tire (ie. Sumitomo) to
replace the front --it's using a m/c tire that was originally designed
for rear wheel use on a m/c to replace the front tire on the Silverwing.

Maybe
it's my naivete', but other than tire size I didn't know there was a
difference between front & rear tire designs.

A rear tire on
the front?...can anyone shed some light on this for me? What's the
advantage / disadvantage?

So let break it down

1) Tread depth.

If you measure the tread depth on a new tire of front and the tread depth of a new rear tire ... as I recall the rear had around 2.5 to 3 times the amount of tread depth.

2) Tread pattern

A lot of the rear tires have more and better water displacement ability. From what I have read if you mount a rear tire on the front then you should reverse the direction to allow water evacuation to the front. If you ever drove your car with a car tire on a tire not-designed for the rain and then switched to a tire designed to quickly/efficiently redirect the rain/water ... it was a huge difference.

3) Tread wear

Both of my OEM Bridgestone Hoops have "scalloped" with the same exact scallop pattern. A raised "diamond shape" appears in inner then outer repeating pattern on both sides of the center line around the circumference of the tire.

I would not be surprised to find that the rear tire on the front would not have this problem. I am not saying all tires scallop just a lot of them seem to suffer some sort of thread wear problem ... it will be interesting to see what a rear tire does.

honda_silver is correct I was first and there are still more that can be learned in this area of Darksiding. I now have around 17,000 miles on my SWing with the Sumitomo 165/70 r13 car tire, HS has total of 24,000 miles, 21,000 on the current tire, first tire he had was irreparably slashed by some road debrie.

I have also had the pleasure of owning a darksided Burgman 650 and got 20,000 miles on a Potenza 165/65 r14 car tire which I have now replaced with a Semperit 155/65 r14 so far it's a good tire, only 140 miles on it so far.

Estimations on the Sumitomo by me is that it should come out with 31,000 to 35,000 miles of road wear before needing to be replaced. The idea of using a rear MT is that the much deeper tread would allow it to give us twice or more the regular miles before needing replacement, plus the added safety factor of a thicker rubber on the road to resist a puncture.

Cheif Rider has also proven that a tire of the 175/70 r13 type could also be used safely on a SWing, so like I said, much left for us pioneer types to explore.

The MGS was the preferred tyre for the X9 but it appears it's no longer available in Europe.

I read with interest all the first-hand information about using car tyres on maxiscooters but have niggling doubts about doing it myself.
Since I've given up doing any mechanical work on my vehicles and leave it all to my dealers I tend to let them get on with it, thus having recourse to hold them responsible if things go wrong - not that I believe in suing everyone right, left and centre for human error - and trust that they will do what's best.

So in going to the 'Double Darkside' front tire is the idea that you are changing to a Radial tire, as the the Sumitomo is for the rear. Or is it that you keep the Bias ply tire on the front, but 'reverse" the rotation mounting for better water dispersal?

Tim

Cosmic_Jumper wrote:

So in going to the 'Double Darkside' front tire is the idea that you are changing to a Radial tire, as the the Sumitomo is for the rear. Or is it that you keep the Bias ply tire on the front, but 'reverse" the rotation mounting for better water dispersal?

Just to clarify the terms as I understand them:

1) Darkside

Running a "car tire" on the rear ... today most car tires are radial tires. Not all "car tire" are suitable for 'Darkside tire' usage ... for example run-flat tires did not do very well.

Different "car tires" can have different characteristics, so if you do not want to experiment with unknown "car tires" then check if someone else has tried the specific tire you are interested in. If the specific "car tire" experience does not exist, then let us know so we can track your experience.

2) Double Darkside

There are some non-SWing people who are using radial "car tire" on the front tire. From what I have read as strange as it sounds, when they switched to Darkside and then added radial "car tire" front ... the handling improved. Some day I may temporarily try an experiment with "car tire" on the front, if it does not work I can switch back myself ... so I would not suggest unless you like to experiment yourself.

Though I believe most people running "Double Darkside" with "car tire" rear and "motorcycle tire" on the front. The front "motorcycle tire" ... I do not believe the tire has to be "bias-ply". Once again different "motorcycle tires" may have different characteristics, so if you do not want to experiment with unknown "motorcycle tires" on the front then check if someone else has tried the specific tire you are interested in. If the specific "motorcycle tire" on the front experience does not exist, then let us know so we can track your experience.

honda_silver wrote:

I found the Michelin Gold Standard tire that fit the front and documented it on the silverwing.org site which knightrider later installed. I have my Michelin Gold Standard in my garage waiting for the front tire to wear down.

I just installed the rear Michelin Gold Standard on the front ( for more information https://www.silverwing600.com/silver-wing-topics-f3/double-darkside-t1391.htm#11445 ).

I am now officially double darkside

I would like to bring this thread back for the purpose of learning more from Honda_silver, about his experiences in "double darksiding".

I too would love to know your experience with the double darkside, Bill! You put a lot of miles on your Silver Wing so I'm interesting in hearing what you have to say about the differences in handling.

Bill (Honda Silver),

Last October you posted that you had put a Michelin Gold tire on the front of your SW. And IIRC that tire was originally intended as a rear tire for some other type of motorcycle --and you had intentionally mounted the tire backwards.

Can you please give us an update on the performance, handling, and tread wear of your SW with that tire. Also, is that tire a radial or bias ply tire?

I'll be in the market for a new front tire soon and would sure like to go with the highest aspect ratio tire available --not only to increase the life of the tire, but to put more rubber between the pot holes & the wheel rim, and to raise the height of the front of the scoot too. A /90-14 would be ideal.

Tim

I'd be interested in that info for our UltraWing trike riders as well.

Bob Witte
http:/www.TheTrinityTrike.com

honda_silver wrote:

Here is the Michelin Gold Standard information sizing information

Michelin Gold Standard does not have a 120/80-14 but they do have a
140/70-14 rear tire ... here is the tire
math ( http://www.discounttire.com/dtcs/infoTireMath.dos
)

120/80-14
Sidewall Height: 3.78
Section Width:
4.72
Overall Diameter: 21.56
Circumference: 67.73
Revs per
mile: 935.48

140/70-14 rear tire
Sidewall Height: 3.86
Section
Width: 5.51
Overall Diameter: 21.72
Circumference: 68.22
Revs
per mile: 928.7

Difference
Sidewall Height: 0.08
Section
Width: 0.79
Overall Diameter: 0.16
Circumference: 0.49
Revs
per mile: -6.78

I have been very hesitant to document this change because the change is more drastic of a change then the rear Darkside tire.

With the rear Darkside tire, if you teach yourself to counter-steer for turns and through turns then you find the rear Darkside tire natural.

When I was researching Darkside tires, some people documented that different tires were better than others ... the same may be true here for the Michelin Gold Standard.

With this front Darkside tire, you have to continually keep the tire handling in the forefront of your mind. I would not recommend this for everyone and it may help if there is any other individuals willing to very carefully test to confirm my observations.

The front Darkside tire does have a different profile than a normal front tire, so if you get close to the edges I did not like the handling ... which is not very often with the wider profile and shape. If your current front tire edges are worn, I would not recommend this tire.

Positives grades

A+ - Huge improvement on steering over/through grooved pavement
A+ - Tire life is looking real good

A - Highway/normal driving

A - Provided additional "shock absorbing"

B - Handling characteristics when not going straight (due to constant thought process)

Negative grades
C- - Running over tar snakes the front tire feels like it tends to slip more
D - Riding near edges

I may have left out some grades ... so I may periodically add them as I recall them.

Things that I would want to study more:
I was on a divided two lane highway curving to the right and I was following the curve and slowing switching to the left lane for traffic. The left lane was slightly lower than the right lane with tar snakes around the area as I recall. The handling seemed completely "different" maybe something on the road, I ended up straightening up and applying the rear brake and moving toward the left edge.

Did not grade yet:

-) Rain
-) Constant curves (like the Ozarks)

I would not recommend any new/inexperienced person test the front Darkside tire without more reviews/analysis.

Merged topics as they were duplicates and referrenced each other, this will make it easier to find the info.

Tim,

Conjecture: I wonder if a 160/60-14 might do a little better more width to work with ... ... here is the tire
math ( http://www.discounttire.com/dtcs/infoTireMath.dos
)

120/80-14
Sidewall Height: 3.78
Section Width: 4.72
Overall Diameter: 21.56
Circumference: 67.73
Revs per mile: 935.48

160/60-14 rear tire
Sidewall Height: 3.78
Section Width: 6.3
Overall Diameter: 21.56
Circumference: 67.73
Revs per mile: 935.48

Difference
Sidewall Height: 0.00
Section Width: 1.58
Overall Diameter: 0.00
Circumference: 0.00
Revs per mile: 0.00

Will have to check the different brands.

Car tire on front or rear really stupid idea

Car rims and bike rims beads are different.

Handling----SilverWing with car tire is not going to handle better....in daily or emergency situations.

There is more to scooter/motorcyle tires than how long they can last.


From my professional point of view----unsafe.


John Grinsel BSc Safety

From my understanding of motorcycle tires versus automotive tires, the difference is compound. The softer compounds allow for better traction although they don't last as long.
This comes in to play with braking. The reason a motorcycle stops faster than a car is the adhesion factor of the tire compound. (not weight as is usually suspected. Galileo proved it.)
Going "dark side" for longevity has a trade off. There is no such thing as a free lunch. The trade is adhesion. That usually means emergency stops are affected.

There is an article by James R Davis about tire longevity on the motorcycle safety site. http://www.msgroup.org/Tip.aspx?Num=085&Set=&SearchTerms=car%20tires

I'm not trying to judge anyone or say their choice is right or wrong, just that it is a choice and best to make an informed choice.

Buickguy wrote:

From my understanding of motorcycle tires versus automotive tires, the difference is compound. The softer compounds allow for better traction although they don't last as long.

There is a device called a durometer which measures the softness of tire.

The Darkside tires are softer than motorcycle tires ... right around the softness of a motorcycle racing tire.

There are differences in the design of motorcycle and car tires. Originally all motorcycles used basically the same tires as autos. My 49 Cushman scooter used 4.80 by 8.00 boat trailer tires. There's no doubt that a motorcycle/scooter can run on car tires. I've ridden a GW with a CT on the rear and wasn't particularly impressed, I know I could outrun that bike with my GW on bike tires in the twisties it just didn't handle as well to me. Hands off tracking with that CT wasn't as good as it is on my bike with motorcycle tires. I don't think motorcycle tires were designed just to sell a shorter life tire to make more money for the manufacturer. The only benefit I can see to a CT is longer tire life. To me that's not worth losing the edge in handling. I like to carve the curves and want the best tire for that which is a motorcycle tire. I'm willing buy a new tire more often for the best all 'round performance. BTW - hydroplaning is rare with a two wheel vehicle because of the tire's rounded cross section, auto tires rely on tread design to push away water but I'd bet it's easier to hydroplane a CT on a lightweight scooter than with a bike tire.

There are many opinions on the subject. Since 1966 I have run car tires on the rear of most of my bikes. If you have not tried it (so called dark side) you have no basis for a opinion.

Anyone can express an opinion since an opinion can be based on both emotion and interpretation of facts.
To make a judgement based on emotion is not generally very sensible, though.

It is my opinion that using car tyres on a motorcycle is not sensible but I cannot make a judgement since I haven't ever fitted car tyres to my scooters.

Because of a front end wobble on my wife's recently converted Yelvington trike,I have been doing some research and I have ordered a Michelin Gold Standard rear tire in size 140/70-14. I will have it mounted and balanced in the "reverse" mode similar to the Michelin Pilot Activ that I have on my Goldwing trike. It should arrive in a few days and I will keep everyone abreast of the situation. Apparently, the Gold Standard has been replaced by the City Grip model, but I liked the look of the Gold Standard tread pattern better and found some on Ebay for a good price, $50.00 including shipping. Now the wait begins. Thanks to all for your advice. So I guess we will be "double dark" also!

Rob


__________________

MikeO wrote:

Anyone can express an opinion since an opinion can be based on both emotion and interpretation of facts.
To make a judgement based on emotion is not generally very sensible, though.

It is my opinion that using car tyres on a motorcycle is not sensible but I cannot make a judgement since I haven't ever fitted car tyres to my scooters.

Not very sensible, yes,based on fact,no. WELL SAID.

IrishRob wrote:

Because of a front end wobble on my wife's recently converted Yelvington trike

What tire did you have on the front before??

IrishRob wrote:

I have been doing some research and I have ordered a Michelin Gold Standard rear tire in size 140/70-14. I will have it mounted and balanced in the "reverse"

On a trike, it might be an great match.

IrishRob wrote:

the Gold Standard has been replaced by the City Grip model

I would be curious of the Michelin City Grip characteristics compared to the Gold Standard.

Be waiting for your results with great interest. Thanks IrishRob! Also, what rear tires did you put on your Yelvington Kit?

If I understand this right---Trike, right? Wobble probably related to trail, side car outfits do it too------first trail problem needs to be addressed---different triple trees should do it----trike maker should supply....but trikes are built to no safety standard or performance standard in US. Then car tire on front ok...........BUT car tire beads and motorcycle rims don't mix well-----so car wheel /rim needs to be adapted-----European sidecars outfits do use car tire----but special wheels for job! See EML. On trail, HD trikes have different trail than solo bikes.

Scary thing about current trikes----usually appeal to the unskilled and in this case much more dangerous than solo scooter. Think tip over. Sidecar outfit in skilled hands probably safer (I rode them for 40 years) in unskilled hands, accident waiting to happen---trikes, had 2 Messerschitt cars, 3 wheel pushers that could get you in real trouble as inside wheel rose and you didn't know what you were doing.

Notice----magazines never run performance tests on trikes? Truth gets out they would have loss of ads.

Then......steering damper needs to be addressed. Then once bike front set up for trike and car tire....won't work safely was solo.

john grinsel wrote:

BUT car tire beads and motorcycle rims don't mix well

The Yelvington trike provides two rear car tire rims for the two car tires.

He will be mounting the Michelin Gold Standard scooter tire on the front Silverwing rim.

As Honds Silver has said, the rear trike portion has 175/65-14 Falken 60,000 mile radials, obviously on car wheels. The Michelin Gold Standard is a rear scooter tire replacing the original front hoop... as for trikes being inherently unsafe, I don't know about the UK, but here in the US there are several manufacturers that make conversion kits from scooter size units all the way up to Honda Goldwings and big Harleys, actually H-D makes there own trike now also. Many trikes kits have been reviewed and tested and the results have been published in any number of motorcycle periodicals. In fact the monthly Goldwing magazine has recently added a special section devoted to trikes and triking.

After riding motorcycles of various sizes since 1966, I went with a Goldwing trike about 5 years ago. Having bad knees and a shoulder replacement took me off two wheels and I haven't looked back. My wife loves my trike but she has difficulty with shifting so I went with a trike kit for the automatic Silverwing so she could enjoy driving herself when we don't go out two-up.

I will try to keep the information coming once I get the semi-darkside rear scooter tire installed.

Rob

x

IrishRob wrote:

I will try to keep the information coming once I get the semi-darkside rear scooter tire installed.

I had two Bridgestone Hoops front tires, both failed the same way alternating diamond pattern on both sides of the center of the tire.

I have not had any problem with the Michelin Gold Standard.

Is there a DS front tire out there that someone fitted on there swing? A rear MC tire .

I found the size of rear tire that Honda-Silver said on DDS forum. Looking forward to the first review.

tinman wrote:

Is there a DS front tire out there that someone fitted on there swing?

Moved to Double Darkside thread

Pic up a 140 70 14 Avon striker rear tire that am going to install some time this spring . I will give a review once i have put some riding time on It.Looking forward to see if it is a positive or negative choice .

I am now a double dark side rider .I installed a Avon viper striker 140 70 14 .The first thing I notice is the 6" wide tire becomes a 5 " wide tire when installed on the front swing rim,and that makes it 1/2 " wider then the 120 stock tire 1/4 " on ether side and is almost identical in appearance. I installed it with the arrow facing forward because the Avon scooter rear tire can also fit on the front say's Avon .After a 90 kl run at 100 kl ph I fond that it responded very well under these condition. Tire pressure is at 32psi and I will try a lower setting to find the sweat spot. The deeper thread should serve me well when I install the new trigg trike kit when My pillion comes for a ride.

So does the Avon 140/70 14 make the scooter any taller?

Tim

No the swing is the same hight as before because the tire hight is 70 mil.and20 mil wider ,they cancel each other out .When you go to the tire calculation chart They are almost the same diameter.The advantage is the debt of thread compared to the 120 80 14 IRC tire ,2 1/2 times deeper . It should give 20k kl more to the life of the tire.

What is a Dark Side tire? And are they safe? I sure hope I'm not going to start a "big argument" !!!

They are black,and not visible at night . Most tire are dark at night.

I have 15k kl on my rear DS and I see no sign of ware,and 5k kl on my 140 70 14 Avon Stryker rear tire that I installed on the front . All but a few 100kl on 2 wheels and the rest with my trike kit ,it handled very well on 2 wheel riding and with the trike. I was expecting some ware on the tire on account of the extra force needed in the curves but saw no sign of it .So fare I am very please with the way things are going.

My brother in law has a Goldwing with a Dark Side "run flat" rear and rear MC tire on the front. He says he scrapes his footpegs (boards) all the time, the handling is great even in rain, and he would not go back.

I looked at his goldwing tire next to a goldwing with a regular tire while on the side stand - got down real low on my knees - and his contact patch was longer and wider than the standard MC tire contact patch. More surface to grip...

I now have 13k kl double dark side on the 140 70 14 Avon striker tire and it is totally destroyed .Halve the tire has dept cupping.The tire balancing beads has turn to a grey powder .I had to re install my old 120 80 14 IRC tire with 31 K kl so I could ride this weekend. I ordered a 120 80 14 Pure sport from Canada s motorcycle

I originated the use of a car tire on the Honda Reflex scooter and the use of a 150/70-13 scooter rear tire up on front of the Reflex for the "Double Darkside" treatment. My comments on the subject of darkside can be found on the Yahoo hondareflexowners group (as bandito_two) and on the advrider.com/forum (as bandito2) mostly in the "battle scooter" sub-forum. There are other forums where I post, but these 2 are where most of my comments on the darkside subject can be found. I consider them to be informative, logical and reasonable. I'm just a regular guy.......with scooters....... and (different) ideas.

So, FWIW............
Being the pioneer type, I also run a Silverwing rear tire up front on my Honda Reflex scooter. (rear tire up front along with car tire on the rear is known as DOUBLE DARKSIDE) My bike had an episode of head shake once but that problem got resolved. It sticks like glue to the road, barely shows any wear after several thousand miles of use and, well... it just looks better too along with the taller car tire on the rear. Some big bikes do this too.

There are differing opinions as to which rotation direction to mount the rear tire up front. I had mine mounted in the normal direction as the tread is designed to evacuate water best in forward rotation. Remember even when mounted on the rear of a bike, that there are also forces acting on that rear tire in braking which is in the opposite direction from acceleration forces. Even more so on a larger heavier bike, especially if it is heavily laden with a passenger and extra gear.

The bike I have it mounted on is much smaller and lighter and I don't carry a passenger. Still I don't think even that matters that much. On the rear, the forces work the tire in both directions, on the front it is freewheeling and only gets force put to it when braking; and that is mostly after the engine and rear wheel have already slowed the bike down. The point is that the front tire does not get stressed as much as the rear tire. This becomes evident if you stop and think about it; front tire even if slightly taller is narrower, probably with tread not as deep as the rear yet typically lasts twice as long as the rear tire which is much wider and usually has a deeper tread.

So, on the much larger, heavier bikes, mounting a rear tire up front in reverse rotation makes sense to some of those guys. Then there are others who mount it in normal rotation for many of the same reasons I did.

It did however, present an issue with the front fender. I rode for a while without the fender which was fine until encountering wet pavement. Then dirty water spray would be flung up onto the windscreen, face shield, helmet, etc. making a mess of things and obscuring vision. The fender was modified as a remedy.

This is all well and good for the Reflex, but I don't know how a larger tire (scooter rear tire) would fit under the Silverwing front fender. In any event, the only rear tire that I know of that >might< fit on the front of a Silverwing is a Pirelli Diablo 160/60-14. It should have the same diameter as the standard 120/80-14 front tire so that exchange would seem to pose no conflict as far as ABS operation goes when using a standard scooter rear tire on the rear.

For the rear, a *(155/70R13 ) 165/65R13 seems to be about as close to the standard 150/70-13 scooter rear tire as one can get with a car tire. The total difference in diameter being only about  *(7mm ) 4.5mm taller with the car tire. It would be interesting to find out if using this size car tire causes problems with the ABS functionality on the S-Wing.

On my Reflex which has the speedometer operated from the front wheel, the once, usually optimistic reading became a bit more accurate but at the expense of a slight error in the odometer; it now reads less than actual. The Silverwing speedometer/odometer gets its info from the rear wheel. The same thing would likely happen here as well, but only by a small amount. I just wonder if it would still be enough change from standard to affect the ABS system. I'm pretty sure, though not absolutely so, that when the ABS detects error, it defaults to standard
mode. That is to say that the brakes would still work, but only just like standard brakes would work.  If any technical types here know for sure, it would be greatly appreciated if it were clarified for us.

I just recently got my Silverwing up and running after just over 3 1/2 years of it being a dirty, dusty and damaged garage queen. I put an Avon stryker rear tire on it because I thought about selling it after repairs were done. Now I'm not so sure about doing that. But, when it comes time to change the rear tire, or possibly even sooner, it will get a *(155/70R13 ) 165/65R13 car tire on the rear.

I have plenty more I can say about the Darkside, but just a taste with the double darkside seems a good enough start.

NOTE: *(these items were edited because I have since found that the 165/65R13 is closer to stock diameter than the 155/70/R13 tire)

Mike B.

(Rochester Hills Michigan Dark Side Rider)
(4 Honda Reflex scooters and a FSC600A Silverwing too)

Buickguy wrote:

From my understanding of motorcycle tires versus automotive tires, the difference is compound. The softer compounds allow for better traction although they don't last as long.

At first this seems reasonable, but it is an often stated misconception by the misinformed/uninformed and is not correct.

honda_silver wrote:

There is a device called a durometer which measures the softness of tire.

The Darkside tires are softer than motorcycle tires ... right around the softness of a motorcycle racing tire.

And this is true and correct. The durability of the softer compound car tires over MC tires comes likely from the fact that the full width of the car tire tread is available and is used during most of its life. That life being spent mostly upright and perpendicular to the road. For the most part, load and wear is distributed evenly across the full width of the tread of a car tire and they would tend to run cooler.  Indeed, if softer compound = better adhesion, then car tires are "stickier" and have better grip. If better grip = safer for braking and maneuvering, then you have an obvious conclusion in that regard.

The MC tire on the other hand, with its rounded profile can only use something between 1/4 to 1/3 of its available tread width at any one given time. Since a bike spends most of its time upright, most of the load and wear is confined to that narrower section in the middle of the tire. Localized pressure and friction induced heat on the center section tread is conducive to quicker wear. Surely most have noticed when they need to change their rear MC/scooter tire that the center section is well worn but lots of unused tread remains just off the center line on up to the sidewall. MC/scooter tire longevity is limited by the durability of the center section tread of the tire. IMO, a lot of good rubber is wasted from non-use. (even by those that frequently ride the twisties)

I am of the opinion that a better, more durable, specialized MC/scooter rear tire with urban/touring use in mind could be done with a little bit wider center section that has deeper tread than a standard MC/scooter tire. They probably never will because it would have to fit in an even narrower niche market than what scooter tires are in already. (in North America anyway )

So we Darksiders just use car tires on the rear. And for those who dare, MC/scooter rear tires up front.
Tire aesthetics (how it looks) is not the only reason darksiders use a car tire.
Tire longevity is not the only reason darksiders use a car tire.
Tire strength/durabiliy is not the only reason darksiders use a car tire.
Tire cost is not the only reason darksiders use a car tire.
Tire change frequency is not the only reason darksiders use a car tire.
Tire performance in braking is not the only reason darksiders use a car tire.
Tire performance on wet roads is not the only reason darksiders use a car tire.
Tire speed rating and load capability is not the only reason darksiders use a car tire.
Tire performance on rough pavement/gravel/dirt roads in general is not the only reason darksiders use a car tire.
Most of these combined, if not all and more are the reasons why darksiders use a car tire on the rear.

BTW, a simple test you can perform yourself is to take a ball point ink pen (bic pen or similar fixed nib type pen) and push the point into a bike tire tread and note how far it goes in. Then do the same thing with the same amount of pressure into a car tire tread and note the difference of how far it goes in compared to the bike tire. (using a 2# or so weight atop the pen for both tests would give a more consistent pressure and a magnifying glass may help give a better view.) The nib going further in would indicate a softer compound. While this is not a completely accurate test, it is very similar to what a durometer does when testing material hardness and should demonstrate a difference in the rubber compound hardness/softness of car tires compared to MC/scooter tires.

Mike B.

(Rochester Hills Michigan Dark Side Rider)
(4 Honda Reflex scooters and a FSC600A Silverwing too)