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This is not to start a thread on if a car tire is safe ect. But I have been lurking on the darkside forum and there is a thread about putting a 175/60/16 car tire on a 1500. This tire is approx. 1.6 inches smaller in heigth than the oem 160/80/16. This in effect would make the tire turn approx 15% more per mile than the stock tire. Approx 800 revolutions for each mile traveled verses 770 per mile on the oem tire.



My question is this, what would the long term effect be on my GW ifI was to start riding it with this smaller tire on it. The engine will work 15% more than usual along with all the other drive line componets ect.



Randy:?
 

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According to my calculator (it just woke up so it could be wrong) that's only a 4% difference so it's not that much. For instance if you are running 3000 RPM at 70 mph (don't know if that is right on a 1500) with the shorter tire it would be 3120 rpm at 70 mph. It might affect you fuel economy a little but the savings on tires would offset at least some of that cost.
 

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Monkey with a Football
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Plus the 4% would be a reduction in torque loading from the back end.
 

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I am wanting to do this but I just don'w want to do something to screw up my bike. Also another factor that was mentioned was that the rear shock has to be aired up to 60 lbs to get the rear end up high enought so the plastic don't rub. Not sure where it rubs but it was stated as an issue.
Randy
 

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gas mileage will drop and you'll have to run the engine harder for the same mph.
 

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Monkey with a Football
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Hidepounder wrote:
Also another factor that was mentioned was that the rear shock has to be aired up to 60 lbs to get the rear end up high enought so the plastic don't rub. Not sure where it rubs but it was stated as an issue.
Randy
I think it is a case of a square peg (cross sectionally) in a round hole. The corners of the peg will touch the arc of the round fender well sooner than it would if the tread were arced to match.

I'm going to look at heat forming the plastic fender cross section to have some space for those 'square peg' corners after I see if the rim can take the tire safely. Probably going to have to relocate some things under the seat to do it though.

I'll have to find some practice parts off of a part out job, someplace.
 

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Piled Higher and Deeper
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I think that the math will show that there is about 7% difference in diameter (26.1 stock compared to 24.3 CT) so 3000 rpm will be 3210... not that any of the above arguments are any different.. just don't get locked into that 4%.. it is more than that..

and those number are comparing new tires, not new to old which would get closer..
 

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On the shorter tire -- and the over-spec inflated shock ...

The geometry of the bike will change some as well-- sharper swing-arm angle = higher angle of operation for the u-joint and a little more length change as you bump (sp the slip-splines will travel more). I'm not certain if the shock pressures will compensate for 100% of the ride-height, the castor (rake) on the forks/front tire may also be impacted...

Interesting experiments to be certain. I too will watch closely.
 

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I really doubt you could compensate with increased shock pressure. With a light load on the bike the shocks are pretty well fully extended anyway.
 

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Monkey with a Football
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Hidepounder wrote:
ThFireman wrote:
Im not very smart so I have to ask... "Why?"
As I stated I want to go to the darkside and run a car tire. Lots of reasons why. I think this has been hashed and re hashed on different threads.

Randy
I like doing first hand research on things motorcycle. :coollep: This is one of them.
 

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ThFireman wrote:
Im not very smart so I have to ask... "Why?"
There are lots of good reasons.

In the case of the GL1800, there is a size of high performance car tire that almost perfectly matches the stock motorcycle tire. And as in many things, someone discovered it and tried it, probably to save money on the cost of tires.

As it turns out, the GL1800 is probably the perfect test case. Since the tire is so close to matching in dimensional size, and it's a high performance tire, it turns out it worked very well and there are lots of people doing it and well satisfied.

As time moves on, even more benefits have surfaced. So not only do most people find thatthe tire lasts longer, and grips just as well, some people are upgrading to the "run flat" versions of that tire size and getting added peace of mind.

As I said, the GL1800 is probably the best test case. As such, there are so many people out there that have done it, and reported back that they are pleased with it, and are getting such good results, that us other guys on non-GL1800's want to do it too. So everyone is trying to figure out what car tires might fit on what bikes.

In the case of the GL1500's only one tire size has been found that will reasonably fit. But since the tire size isn't as close as was the case on the GL1800, the results aren't expected to be a sure thing. So what you are seeing now is before actually trying it, people trying to logically work out what it might do, and what the potential/probable results might be.
 

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Sounds like Rudy is playing around with it. If I had a 1500 and were thinking about going darkside, I'd be watching right over his shoulder. He's a pretty smart guy.

I don't have a 1500. I bought an 1800 and my car tire bolted right on.

I have to warn you Randy, "they" say that if you mount a car tire to your bike, you'll crash and burn. And you'll void the warranty. And your insurance company won't cover you. And your Mom won't invite you over for Thanksgiving anymore.

Good luck with your project. Please post how it works out (and include pics).
 

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I seriously considered a car tire on my bike. But I also carry a load on a trip. So clearance would be minimal when loaded. I'd hate having to watch for RR tracks etc.
 
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