My Venture to “The Darkside” & Return

I was seduced to the "Darkside" with the promise of increased tire life, better rear wheel traction, reduced costs, and good handling. Sounds too good to be true, and for me it was too good to be true.

I bought a BF Goodrich 155/80R15 car tire for my 06 Midnight RSV. The tire cost $84.76 shipped to my door. My local motorcycle dealer politely declined my invitation to mount my new car tire. They said they were aware of people using car tires on motorcycles; however, in today’s litigious society, they didn’t think any liability waiver signed by a customer for such work would hold up in court. So, a friend and I mounted and balanced the car tire, easy job, and no problems. The maximum inflation pressure imprinted on the tire is 35 psi, but I inflated it to 40 psi because I believe that another "Darksider" is using that pressure in the identical tire.

Now for the test. A friend and I took an approximately 350-mile ride through the beautiful Black Hills of NE Wyoming & South Dakota to include Spearfish Canyon, Mt Rushmore, and the Iron Mountain Road. Great ride, gorgeous scenery, and road conditions that varied from gravel to Interstate and every possible road surface except ice, snow and mud. Fortunately, we missed the hail storm that deposited several inches of hail on Hill City.

From the beginning, the bike felt a bit squirrelly. On straight roads the bike had what can best be described as a slight wobble; like you get when going through a high speed sweeping corner with worn shocks. This "wobble" wasn’t bad, but it was always there except when under throttle. Reducing the tire pressure to 35 psi almost, but not quite, got rid of wobble. Reducing the pressure to 30 PSI increased the wobble.

Turns: Low speed turns and parking lot calisthenics, (lock-to-lock figure 8's), were as easy as with motorcycle tires. Low speed curves, (under 40mph), under throttle were precise; however, the handling was nowhere near as forgiving as with a motorcycle tire.

We hit Spearfish Canyon with approximately 110 miles on the car tire. Pushing the bike hard into several curves caused the rear tire to kick out before anything could drag. In fact I did not drag anything through the canyon. I have ridden this road many times, and the car tire did not corner as well as a motorcycle tire. The bike cornered fine if I stayed at or near the posted speed limit, except for the ever present wobble. We ran the canyon in both directions because road construction closed the road near the top of the canyon.

High speed sweeping curves accentuated the wobble and at times were more than I cared to deal with. I only came close to losing control once and that was in Spearfish at a whopping 20mph. Road construction crews were removing asphalt with a roto-mill machine and the resulting grooves combined with the wobble were enough to have the front and rear of the bike going in different directions at the same time. It wasn’t fun.

Despite, or in spite, of the ever present wobble, the car tire provided excellent rear wheel braking. It took quite a bit of pedal pressure to lock the rear wheel and brake induced skids were very controllable. I believe there would be fewer motorcycle accidents if motorcycle tires could provide this level of rear wheel braking traction. The car tire also excelled at wet traction and gravel roads.

In conclusion, my experience doesn’t match what I’ve read from others who have gone to the "Darkside." Why? I really don’t know. Maybe they’re more skillful riders than I, or maybe I ride harder and faster then they do on their car tires. I believe that other car tires will perform differently, but only a couple of companies manufacture car tires that can fit the RSV. My $84.76 experiment with the "Darkside" is over. I’ve ordered a Michelin Commander to replace my car tire. I’ll keep the car tire around to use as an emergency spare, but I doubt if it will ever be on the rear of my bike again.

I am sorry you were seduced to the darkside by us and were not happy with the performance of the tire. It's not for everybody. Have you thought of selling the tire? There might be someone here looking to try one out, and it would be nice to have a opportunity to try one without having the expense of a new tire.

Thanks for the complete report. I've never had any desire to put a car tire on, but have been curious about the performance.

RR

hi ob-1

just read your report on your c/t experiance. i have rode the 3 sisters here in the hill country of texas( fm337,336 & 335). i was happy with the way the c/t performed

while ridening them. you tride it and it didn't work for you. thats ok, as i have said its not for everyone.

thanks for the honest report on your experiance on your c/t. i now have 5,000

miles on mine. fixing to ride up to the 08 int. rally and pulling a trailer,will report how i feel on the first leg of my trip when i get to loudon,tenn.

best reguards

don c.

Just got back ourselves from the same trip. We had to have been meeting each other on the road as Spearfish Canyon was closed for 3 days and we did the same as you. Running it and turning around going back the same way!

I have replaced the car tire with Michelin Commander and the change in handling over the car tire is nothing short of amazing. No wobble or wave; the bike is once again rock steady and can corner without the rear kicking out when pushing hard into a curve.

In Conclusion; can you run a car tire on an RSV? Yes, but only if you want to give up the fine handling qualities our bikes have with any quality motorcycle tire.

You rode 350 miles on a wobbly tire??? OK.... Well sounds like you might have had a balancing issue or maybe the bead wasn't seated 100%... How did you and your friend balance the wheel? How much air pressure did it take to seat the bead? Did you take pictures of the tire on your bike? Inquiring minds want to know

You rode 350 miles on a wobbly tire??? OK.... Well sounds like you might have had a balancing issue or maybe the bead wasn't seated 100%... How did you and your friend balance the wheel? How much air pressure did it take to seat the bead? Did you take pictures of the tire on your bike? Inquiring minds want to know

We static balanced the tire and I did the same for the Michelin Commander that is now on the bike.

Yes, the bead was seated. I believe the air pressure at the time of bead seating was approximately 50-60 psi. This wasn’t the first tire I’ve changed...

I looked for things that I might have screwed up and for things that might be wrong with the bike that the car tire might have accentuated or brought to light. Nothing wrong that I can find, and the change in handling produced by going back to a motorcycle tire seems to provide additional evidence of no mechanical problems.

No, I didn’t take pictures of the tire on my bike.

I read everything I could find concerning the Darkside prior to making my decision to go to a car tire. Nowhere did I read any first hand accounts of bad handling or instability.

Let’s remember something here; I thought that going to a car tire would be a good thing. I expected different handling characteristics, but I didn’t expect the bike to be unstable and unstable it was. My definition of unstable is the constant wobble or wave. My friend, riding behind me, easily noticed my bike doing a dance, as he called it. Also, I was not able to accurately predict when the rear end would kick out when pushing the bike into a curve. This point seemed to very dependant on many different factors. I assume that with enough riding I could have learned to predict the rear kick out, but the lack of stability was enough to send me back to a motorcycle tire.

I do not normally ride my bike to it’s limits; however, I can and I am not willing to sacrifice that safety margin for a less expensive and possibly longer lasting tire.

Not trying to stir the pot....seriously...but can you run a radial on the rear and a standard non-radial m/c tire on the front? Maybe a question of ignorance on my part, but I was always under the impression that was a no-no car tire or not! Would that not in itself generate squirrelly handling?

Not trying to stir the pot....seriously...but can you run a radial on the rear and a standard non-radial m/c tire on the front? Maybe a question of ignorance on my part, but I was always under the impression that was a no-no car tire or not! Would that not in itself generate squirrelly handling?

Yamaha does it on the Raider. Custom bike builders do it.

"Also, I was not able to accurately predict when the rear end would kick out when pushing the bike into a curve"

I don't understand what you mean. Are you impling that the rear tire slides out from under you in a lowside skid?

It took me 1000 miles to break in my car tire. After that, I've noticed no difference except improved handling in adverse conditions.

I was seduced to the "Darkside" with the promise of increased tire life, better rear wheel traction, reduced costs, and good handling. Sounds too good to be true, and for me it was too good to be true.

 

 

I feel kinda' left out, I read all the posts by the guys who are riding CT's on their bikes and not one time was I seduced or promised anything. All I got was an account of their experiences on how the tire worked for them and their riding style. flb, you been seducing people?

OB-1,

What are you going to do with the tire? Like I mentioned earlier, you might want to offer it for sale as a used tire to someone interested in the darkside, but not financially in a position to experiment with a new tire.

flb, you been seducing people?

I'm damn sexy...

http://i214.photobucket.com/albums/cc18/WikkedKlownLove/fat-bastard.jpg

Hey flb_78, I put about 300 miles on my tire before it was broke in. But those are 2up miles. I'm running 35# psi in my TA Radial with both Robin and I, with full saddle bags. What do you run 1up?

"Also, I was not able to accurately predict when the rear end would kick out when pushing the bike into a curve"

 

I don't understand what you mean. Are you impling that the rear tire slides out from under you in a lowside skid?

The rear tire would slide out unpredictably when I tried to go through sharp curves at speed. This occurred before dragging the floor board or anything else. Like I said before, I assume that with enough riding I could have learned to predict the rear kick out, but the lack of stability was enough to send me back to a motorcycle tire.

Not trying to stir the pot....seriously...but can you run a radial on the rear and a standard non-radial m/c tire on the front? Maybe a question of ignorance on my part, but I was always under the impression that was a no-no car tire or not! Would that not in itself generate squirrelly handling?

I think the mismatch of bias ply front and radial rear may be part of the problem. I am certainly interested in reading anyone’s experience with a motorcycle radial front tire and car tire radial rear tire.

HOLLY COW!!! I haven't had a bike do that in years, I can't even imagine doing it with a bike as heavy as a Venture! I raced some flat track back in the 70's, but that was with modified Triumphs. Even with my newer Triumphs, in the twisties, I don't spin my tire. Of course, my Triumph today weighs more and dosen't have the horsepower or torque of my older ones. You gotta be one aggressive rider! I would bet you could give Yellow Wolf a run for it on the Dragon.

HOLLY COW!!! I haven't had a bike do that in years, I can't even imagine doing it with a bike as heavy as a Venture! I raced some flat track back in the 70's, but that was with modified Triumphs. Even with my newer Triumphs, in the twisties, I don't spin my tire. Of course, my Triumph today weighs more and dosen't have the horsepower or torque of my older ones. You gotta be one aggressive rider! I would bet you could give Yellow Wolf a run for it on the Dragon.

The rear didn’t kick out anywhere near as much a flat tracker, but it did kick or slide out several inches to maybe as much as a foot. My friend was behind me on his bike and he thought I was going to lose it a couple of times. I was really trying to see what the cornering limitations were while riding through Spearfish Canyon, a road I’m familiar with. I can make much better time through the curves with a motorcycle tire without scraping anything.

With the car tire, I found that I needed to slow down much more before entering the curve and then give the bike moderate throttle throughout the curve. Getting aggressive with the throttle or entering the curve too fast caused the rear tire to break traction and kick out. This was usually accompanied by the wobble or wave. The wobble is what really turned me off to the car tire.

Getting aggressive with the throttle or entering the curve too fast caused the rear tire to break traction and kick out.

I haven't run a CT and am not criticizing, just thinking, this makes sense. As you lean into the corner and roll up on to the edge of the CT tread you go from a big contact patch to a small one.

Back in the day before big custom MC tires were available, the ol' Boss Hoss V8 motorcycle ran a CT on the back, maybe a 215 width. I spoke with a dealer and he said they ran low pressure, like maybe 24 psi. The reason was this. Even though the BH is a big cow of a bike, it's still only 1200 lb. Let's say the rear tire with rider is carrying 800 lb. That 215 CT is probably rated to carry 1500 lb at 35 psi. One of the big things that proper tire inflation depends on is load. As you get away from the max load, you can and usually should decrease the pressure in the tire. If you have a 3/4T or 1 ton truck with load range E tires, you learn that you don't have to run around all the time with the max 80psi in them - it just gives a stiffer ride and wears out the middle of the tread. So, on the Boss Hoss, the reduced pressure, sufficient to carry the load, would allow the tire to flex and deform more in the corners, so it didn't roll up hard on the edge. Have you guys with CTs tried low pressures?

Jeremy

I've run low pressure on the bias ply, but this is the 1st radial tire I have tried on a bike. I ride 2up on the Venture, so the lowest I've had the pressure is 32 #. I'm more comfortable with 35 # as the load rating is above 1000 lbs, and we are not what you would call small. Even at 35 # Robin says the ride is much smoother than with the motorcycle tire.

I expected to drag something before I ran out of tire... The tire pressure was 40psi during the canyon run... I assume that it would have cornered better at 35psi, which I went to later in the day. This pressure also reduced the wobble or wave, but didn’t eliminate it. Dropping to 30psi made things worse so I went back to 35psi.

My wife also said the ride was smoother with the car tire... If only it were stable...

As far as running a biased ply and radial on the same bike, well I have talked several bike mechanics and they see no problem with it. They said it was just a wives tale.

On leaving the Dark Side, well all I can say is:

Welcome Back!!!

It took me 1000 miles to break in my car tire. After that, I've noticed no difference except improved handling in adverse conditions.

A 1000 miles to break in the tire/ or become accustomed to its handling. It seems a long time to break in a tire? could it be that if you were riding it hard you were simplying learning about and adjusting to the tire?