The Darkside.

[Brock]

Winston66 posted.

   


Winston 66 wonders?  Question for today,  This darkside business.

Is there a suitable C/T that will fit the rear of the St1300 some people give good reports about the Kuhmo on other makes of motorcycles.
  Has anyone tried this route.

  Opinions please.

Cheers ,winston66,       

[Dan]

Yeah there's loads of posts about this on the st-owners forum.  There's also a couple of guys using a Bridgestone BT45 rear tyre on the front, to go 'double-dark'.

[Turtle]

That looks like a great tyre for the Nullabour runs time to look into this more for my St1100

[Dan]

That looks like a great tyre for the Nullabour runs time to look into this more for my St1100

For the 1100 I believe we need to get a Goldwing GL1500 rear wheel.  This is because there are no 17" car tyres narrow enough to fit the standard wheel.  I think the wheel would need some spacers made up as well.

The GW wheel is 16", and combined with a tyre narrow enough to fit the circumference is smaller than the standard wheel and tyre.  So the revs required for a given speed will increase.  Acceleration should improve, top speed should drop. 

Personally I would like to try a Darkside bike.  Without actually trying it, I reckon it would be great for distance rides and general commuting, but I am not so convinced about riding quickly in the twisties.  For me at the moment, I would like 2 sets of wheels - normal and Dark, depending on what I am going to do.  Although whether I could be bothered to change them all the time is another matter....

The other concern I have is with insurance and the legal side of things.  If an accident happens, would they pay out?  Anyone know?  I am not worried about damage to my bike, but I wouldn't really want to be sued for $$$s for 3rd party damages/injuries because the insurer refused to pay. 

Or maybe the mods could be declared up front?   

[saaz]

Des is right about the modifications needed for the ST11. The ST13 just takes a car tyre as is. The size of tyre needed is somewhat hard to get even in the US. A London taxi tyre fits it seems.  Insurance wise, I know that some have told their insurance company and it did not matter.  I think you would want any such modification specifically listed on your policy.  I don't even know if you would pass a roadworthy though, and if the bike was not deemed roadworthy then insurance may not cover anything.

[Dan]

I don't even know if you would pass a roadworthy though, and if the bike was not deemed roadworthy then insurance may not cover anything.

That's my concern.  I've just had a look here: http://www.motorcycleroadworthys.com.au/roadworthys.html

WHEELS AND TYRES

Objective: To ensure that road wheels and tyres are of a suitable type and condition and that they provide the necessary load carrying capacity, speed rating and control of the vehicle.

TYRES

Possible reasons for inspection rejection:
Tyres are not compatible with the rim to which they are fitted and not of a type suitable for normal road use.
All tyres are not of the same case construction. (See Note 1)
Tyre load ratings are less than the minimum ratings specified originally by the motorcycle, including motor tricycle(s), manufacturer.
The speed rating of all tyres is not of at least 120 km/h or the motorcycle's, including motor tricycle(s), top speed unless a lower rating has been specified by the manufacturer. (See Notes 2 and 3)
Tyres do not have a tread pattern at least 1.5 mm deep, other than at tread wear indicators, in a band that runs continuously across the tyre width that normally comes into contact with the road and around the whole circumference of the tyre.
Tyre tread, shoulder or side wall rubber are damaged.
Tyres have cuts, bulges, tread separation, exposed or damaged cords or other evidence of case failure.
Valve stems are cracked, damaged, perished or loose.
Regrooved or recut tyres fitted to a motorcycle are not clearly marked "suitable for regrooving".
Any tyre clearly marked "suitable for regrooving" is regrooved or recut beyond the maximum permissible groove depth or is regrooved or recut in such a way that the ply or cord is exposed or damaged.

TYRE / WHEEL WIDTH

Possible reasons for inspection rejection:
The wheels and tyres project beyond the extreme width of the mudguards.
The wheels and tyres contact any part of the vehicle under any combination of steering and/or suspension movement.

NOTES:

[1]  Steel radials, textile radials or conventional crossply must not be mixed.

[2]  A tyre fitted to a motorcycle, including motor tricycle(s), must, when first manufactured, have been rated by the tyre manufacturer as suitable for road use at the lower of:

[a ]  a speed of at least 120 km/h; and

[b ]  the vehicle's top speed.

[3]  Tyres branded "Not Suitable for Highway Use" (NHU) are not to be rejected solely for this reason.


The very first line states that one of the objectives is to ensure the tyre is of a suitable type.  I can't imagine too many inspectors would be willing to stick their neck out and sign to say a car tyre is suitable for a motorcycle, despite evidence from the many Darksiders out there. 

Going 'Double Dark' with a BT45 would be interesting, as they are not radial tyres.  The car tyre would be radial.  So, the two should not be mixed according to the rules.  If it also has 'Rear' marked on it, I guess it could also be considered to be an unsuitable type for the front....

[Brock]

As usual, the specs are a bit vague.

Why would a 400Kilo 220KPH car tyre not be suitable for a bike??

A bike set up with a sidecar, would lend itself to having car type tyres fitted (and have been in the past). It all gets a bit grey I think.

[terrydj]

I've commented on this before bu now can't see a problem. If they want to fit a car tyre to their bike, lose their third party, lose their comprehensive, lose their road worthy all for saving a few dollars, who am I to care. Just one question or maybe two.
1. Just how many rear tyres do these people go through with the same bike?????? I reckon for the majority maybe its 2. Too prove my point just have a look at the milage on most bikes for sale
2. If its so easy to fit a car tyre and its saves you dollars and is oh so safe???? why do tyre companies and Motorcycle manafacturers spend zillions of dollars on Motorcycle Tyre development when  its all been done for them by makers of car tyres
3. What would you do or  say????  if you saw a car fitted with bike tyres or not an appropriate tyre if you were involved in an accident with them and noticed it

[Brock]

First off, I am niether for or against the fitting of car tyres to a bike.

As to the question of  how mant tyres do you go through on the same bike?? I have gone through three sets in two years, just fitted new ones on the weekend. I will no doubt go through several more sets, as I dont see myself replacing the bike in a hurry. I travel 20(ish)Ks every year.

If a car tyre is able to be fitted and used safely, then at half the price of a bike tyre and 4 times the life it certainly is cost effective. Definitely not good for track use tho I think.

As to the legality of fitting Car tyres to a bike, I dont know, it would probably take a Lawyer to work that out.

Bike tyres on a car??? definitely not suitable, as the load rating would be too low for a start, and the finding of a rim to suit the width would be difficult.

[Dan]

I was getting through at least 5 rear tyres per year in the UK over the last couple of years.  I'll be doing about the same over here I reckon, once I get going.  So going Dark is interesting to me, but probably not at the cost of losing insurance cover or spoiling the handling in the fun stuff.

[rendog]

I've said it before and I'll say it again,
"This is the second dumbest thing I've ever seen". 
Legalities aside;
Increased contact patch -
1 increases likelihood of aquaplaning in the wet,
2 increases drag on the drivetrain,
3 increases fuel consumption.
Heavier tyre -
1 increases load on suspension hydraulics,
2 slows response to surface irregularities.
Flat tread pattern -
1 increases force on handlebars to turn in,
2 reduced contact patch when lent over.
etcetera, etcetera, etcetera.

I'll spend the extra $$ and keep my life thanks 
By the way, here's the dumbest thing I've ever seen.

Scooter Elevator Fail

[Poppy Dave]

WHAT A TOSS-POT

[Diesel]

Darkside info for the ST11.

This guy is fairly comprehensive in his +ives and -ives regarding the fitting of a c/t to a m/c....


http://www.st-1100.com/car-tyre-on-st1100.html

[spanner]

contact patch  https://youtu.be/QwSSXHanpv0

after my recent need to purchase a new tyre and my upcoming IBA rides I am thinking DARKSIDE might be an option for me.

[ST2UP]

Even get a second wheel for the DS tyre   

Best of both worlds 

[spanner]

that was definitely my thought process ..... now to research research research .... drink beer and ponder ..... a little more research .... then maybe give up for a bit .... drink more  then ........ 

[Biggles]

Aficionados reckon they corner better than you would expect from a square shoulder, and you'll certainly get more mileage out of them.
Less sure about grip on wet corners.     

[Greencan]

Mornin' All...

I have only ever seen 1 road registered ST1100 fitted with road going tyres here in Australia and that would have been at least 15+ years ago at Phillip Island. The bike in question had a side car fitted and though I cannot recall its builders name, he was a very well known side car road racer and was also know, here in Victoria for building and fitting sidecars.

This particular 1100 with a chair fitted was a really very well built outfit, with leading link front end. Beleive the donor bike was an x police bike and both front and rear wheels had been been modified by turning down the original rear rim and welding on a 15" car rim that had its centre milled out. Cant remember if the swing arm had been modified. The front wheel was also a similar composite fitted into the leading link. Believe the rear (tyre fitted), reduced the overal wheel diameter sufficiently to provide a better (reduced), gear ratio to suit having the chair fitted.

I may still have a few pics about (no idea where though), but I did attach a few to an email on the old yahoo list, including the composite wheels / tyres. The combination was painted all yellow. So there may be a pic or two out there.

:-)

[StinkyPete]

Aficionados reckon they corner better than you would expect from a square shoulder, and you'll certainly get more mileage out of them.
Less sure about grip on wet corners.     

A mate of mine fitted a car tyre to his Suzuki 109 Boulevard in Katherine NT when he wore his rear tyre down to canvas.   It was over $600 for a Boulevard motorcycle tyre and $120 for a Commodore Bridgestone, and he rode it the 3,400km home.    At 32 psi it was crap and simply would not corner due to the flat bottom fighting the bike's lean.   At 24psi the side wall would flex on corners, maintaining most of the normal car tyre contact patch on the road, and handling was reasonable.  A police specialist mechanic and forensic vehicle examiner says he sees no reason why it should fail the legal requirements, but a second opinion would be worth chasing.

[Williamson]

.....  A police specialist mechanic and forensic vehicle examiner says he sees no reason why it should fail the legal requirements .....

Good point!  But I'd like the opinion in writing.

..... but a second opinion would be worth chasing.

Another good point. 

And in writing too, and if it's contrary to the first opinion, shred it, and seek further opinions until you get agreement.

[Brookester]

The darkside debate has been going on for years...very popular in LD riding circles to the point its pretty much a done thing....very popular on FJR's and Goldwings...end result is different bikes and different riders same bikes all say tyre pressure is the hardest thing to work out...most seem to end up in the 26-30psi range....technically all lawful here in Aus as tyre has tread and fits within requirements and physical frame (i.e. does not protrude 2" outside like on a car) only thing some riders have found is insurance and have had to change...I also know several friends who have done it just for long trips when 2 up and towing a trailer

[Piet]

It's a strange thing when some are just so vehement in their opposition to the Darkside especially when they have never tried it and honestly are not able to offer a comment based on experience.

I do run a Darkside rear on my ST1100 and perhaps am one of the very few of Australian ST1100 users.
Is it for everyone?  No.  Obviously not.  I also don't try to shove my views or experience down someone else's gob.

I been having a great run and as of today have 13,631 kms on the CT and the photo below will give an indication of wear and tread depth.  If I read my vernier caliber correctly I have .263 inches or 6.68 mm tread depth.  I think its likely to have a long life on the bike.

[Shiney]

Has it had much of an impact on fuel economy?

Sent from my SM-N9005 using Tapatalk

[Piet]

Hi Shiney,

Not that I noticed.  It’s certainly higher geared and a bit harder to take off at the lights for instance.  But I got used to that very quickly. 

Re economy: I recently started using some E10 95 octane fuel instead of the regular 91 I had been using and that has had a noticeable improvement on economy.  I have been tracking this now for the last few tank fulls,  and will get a better picture with a bit more real data.

Thanks for the question.

[ppopeye]

How is the speedo accuracy now it is higher geared?