Larger Rear Tire for FJR

[Donald Lowrey]

The stock rear tire is 180/55/17 on a 5.5-inch rim. Gregg Rice's site mentions he is trying out a 190/55/17 after first trying out a car tire. But he has not posted his conclusion.
Has anyone here put a 190 on your FJR?
Any opinion on a better grip in the wet?
Any opinion on increased tire life?

Thanks
-DL

 

[Donald Lowrey]

PS - I won't be putting knee pucks on the pavement. Think rally.

 

[Shawn K]

But he has not posted his conclusion.

Yes he did. Click Here

Scroll down about 80% to the bottom to the part that starts with "Tires - Including My Car Tire"

EDIT: I stand corrected. You were looking about a follow-up about the 190-series. I misread and thought you meant a follow-up on the car tire. That's my mistake.

 

[Marc11]

What are you going to get from a 190 that you cannot get from a 180? A wider tire does not provide more mileage unless it's a CT or a specific tire not available in a 180...

 

[EricV]

Has anyone here put a 190 on your FJR?
Any opinion on a better grip in the wet?
Any opinion on increased tire life?
-DL

Hi Donald,

It's been done several times by riders on the FJR forums. Turn in is slower. No, it doesn't have any better grip in the wet. No, it doesn't have increased tire life. There are no up sides to the 190 width tire, only down sides. More cost, slower turn in. Often less tread life because that size is more common to sport bikes and power cruisers. One rider offset the slow turn in by raising the rear with jack up links, which naturally quickens steering.

On the FJR forum I am Darksider #1. I've played with tires some on FJRs. Greg doesn't mention what pressure he used with the CT. Too much and you get harder turn in with a CT. Most people find 28-32 to be the sweet spot. It varies from tire to tire. And remember, just like moto tires, car tires handle different from brand to brand, model to model. What works on one bike doesn't necessarily work on another, or for another rider's riding style.

I do have to ask, why are you concerned about wet traction? I grew up in Oregon and riding in the rain is just riding. You have about 80% of your dry traction in the wet. If you're riding at 80% in the dry, you're probably pushing harder than you should be on public roads.

Michelin Pilot Road 5s offer some of the best wet traction out there. There is now a PR-6, but I have no experience with that tire.

 

[Greg Rice]

The stock rear tire is 180/55/17 on a 5.5-inch rim. Gregg Rice's site mentions he is trying out a 190/55/17 after first trying out a car tire. But he has not posted his conclusion.
Has anyone here put a 190 on your FJR?
Any opinion on a better grip in the wet?
Any opinion on increased tire life?

Thanks
-DL

I can tell you the 190 tire felt better than the 180 tire and it made the odo and speedo accurate. It just felt better on the road and in the curves.

 

[danklyrides]

To expand on Greg's comment about odometer accuracy with a 190 rear (Dunlop Roadsmart 3). On a BBG there was only a .1 mile difference between the odometer and my Zumo XT.
Odometer: 1533.9
Zumo: 1534.0

Cheers!
Alex

 

[EddyC]

I don't know about legislation in your area but over here in Europe, our bikes need a certificate of conformity (COC) in order to be allowed on public roads. Amongst various other technical items, the tire sizes are included in the certificate. That means changing tire sizes is prohibited.
In case of an accident/incident there could arise an insurance problem.

I am not an engineer. I guess the engineers that built the bike know best and determine what tyre size to use.
Imho changing sizes is changing motorcycle geometry, handling, load capacity, overall "feel of the bike", etc.
That could make a difference in case of an emercency where one has to rely on one's reflexes, skill and training in a split second,
without forgetting to mention that the bike and its behaviour has changed and might not react in the way one expects.

Also, the contact area tire/road has increased by using a wider tire.
That means lesser load per square inch which results in lesser grip by equal weight and power of the bike.
Perhaps that is a good thing riding in a straight line but e.g. in the rain it's a whole other ball game.

Experimenting with different brands and models could present the solution you are looking for.
Or is slowing down *the* solution for tire life and grip in the rain?

Best of luck and Stay Safe,
Ed.

 

[Stephen!]

I don't know about legislation in your area but over here in Europe, our bikes need a certificate of conformity (COC) in order to be allowed on public roads. Amongst various other technical items, the tire sizes are included in the certificate. That means changing tire sizes is prohibited.

Interesting... 'round these parts, the Owner's Manual published for use here has only "Tire Recommendation", not mandatory requirements.

Specifically, the manuals for both my 2012 and 2018 K1600s state:

"For every size of tire, BMW Motorrad has tested and approved certain makes as roadworthy¹. BMW Motorrad cannot evaluate the suitability of other tires, and can therefore take no responsibility for their driving safety. BMWMotorrad recommends only using the tires tested and approved by BMW Motorrad. Extensive information is available at your authorized BMW Motorrad retailer or on the Internet at www.bmw-motorrad.com."

Apparently the interpretation of law between the jurisdictions comes down to a difference of understanding between "should" and "shall".

¹ Edit to add: This does not mean that makes of tires not "tested and approved" by BMW are considered to be "not roadworthy". It simply means that they cannot guarantee other size tires that they have not tested themselves would be a good fit... There are plenty of non-BMW "engineers" that have tested other-sized tires and found them to be completely suitable for their purposes.

 

[c10]

190 on my old FJR for my friend . It corrected speedo as mentioned above , and made the bike tip in better .

 

[Shawn K]

I am not an engineer. I guess the engineers that built the bike know best and determine what tyre size to use.

There is no such things as one "best" solution. What constitutes "best" is dependant on design focus, intended use environment, targeted rider, predicted road conditions, and numerous other factors.

Add to that the practical realities of manufacturing costs, supplier considerations, production deadlines, parts availability, and dozens of other considerations, and you come to the realization that every motorcycle ever produced is a series of compromises and cost cutting that is deemed optimal or acceptable for that bike, at the time it was designed, for the intended market, at the price that was projected to yield the biggest profit.

There is no such thing as a purely objective "best". Every motorcycle ever made is a compromise in some way.

 

[EddyC]

There is no such things as one "best" solution. What constitutes "best" is dependant on design focus, intended use environment, targeted rider, predicted road conditions, and numerous other factors.

Add to that the practical realities of manufacturing costs, supplier considerations, production deadlines, parts availability, and dozens of other considerations, and you come to the realization that every motorcycle ever produced is a series of compromises and cost cutting that is deemed optimal or acceptable for that bike, at the time it was designed, for the intended market, at the price that was projected to yield the biggest profit.

There is no such thing as a purely objective "best". Every motorcycle ever made is a compromise in some way.

You are correct and I understand fully!
However, should an eventuality occur in my situation, the fact remains I could never explain to "authorities" having changed the tire size.
For my part one could apply wooden wheels with metal treads, but I 'd like to stick to my "compromised" bike.
Stay Safe,
Ed.

 

[c10]

When I read the stuff brain washed into Euro riders on a inspections required in their country and the conversation is a 180/55/17 vs a 190/50/17 tire
not some DARK side car tire debate I realize Government has succeed in crushing its people . Don't worry were not far behind in the USA , but at least some of us enjoy Freedom to chose our tires

 

[thommo]

I didn't find a 190 help make the bike turn in better, what I found helped turn in was running a sport front tyre, ie, a road pilot on the rear and say a pilot power on the front, the different profile on the front made a difference.

 

[EddyC]

When I read the stuff brain washed into Euro riders on a inspections required in their country and the conversation is a 180/55/17 vs a 190/50/17 tire
not some DARK side car tire debate I realize Government has succeed in crushing its people . Don't worry were not far behind in the USA , but at least some of us enjoy Freedom to chose our tires

I guess that is also the case with some of you having the freedom of riding without a helmet?
Take Care,
Ed.

 

[MrMarcus]

We can mount car tires on motorcycles in the Netherlands.
But the do it almost only on motorcycles with side-car.
When we got the same straights as in the US we would do it also on normal motorcycles.....

 

[c10]

I guess that is also the case with some of you having the freedom of riding without a helmet?
Take Care,
Ed.

Yep my Tin foil cap has been great .

 

[EricV]

I don't know about legislation in your area but over here in Europe, our bikes need a certificate of conformity (COC) in order to be allowed on public roads. Amongst various other technical items, the tire sizes are included in the certificate. That means changing tire sizes is prohibited.
In case of an accident/incident there could arise an insurance problem.

I am not an engineer. I guess the engineers that built the bike know best and determine what tyre size to use.
Imho changing sizes is changing motorcycle geometry, handling, load capacity, overall "feel of the bike", etc.
That could make a difference in case of an emercency where one has to rely on one's reflexes, skill and training in a split second,
without forgetting to mention that the bike and its behaviour has changed and might not react in the way one expects.

Also, the contact area tire/road has increased by using a wider tire.
That means lesser load per square inch which results in lesser grip by equal weight and power of the bike.
Perhaps that is a good thing riding in a straight line but e.g. in the rain it's a whole other ball game.

Experimenting with different brands and models could present the solution you are looking for.
Or is slowing down *the* solution for tire life and grip in the rain?

Best of luck and Stay Safe,
Ed.

Holy Cow Ed, no, you are not an engineer. Much of what you have written is only partially correct. And you've not worked with many engineers, it would seem, or you'd understand they limit their focus very narrowly to the project for average conditions, at best.

If you consider it a bit more, you may realize that any change you make to the bike will mean your awareness of how it behaves will also change. You will adapt to those changes.

Tires, round and black. Tread is nice too. You don't need to slow down in the rain until it becomes biblical proportions. It helps if you ride smoothly. If you're riding 10/10ths in the dry, yes, you should slow down, rain or no rain, for street riding.

The friction between two surfaces is proportional to the force pressing them together, so more force = more friction! A larger contact patch, doesn't automatically mean less friction in real world terms of traction for a given bike, rider, load and conditions. The degree of change for street riding has minimal impact.

Please do share your personal, first hand experience. Please refrain from posting your thoughts on things you have no direct experience with.

@thommo - Thanks for adding some actual content on the subject. Part of the change you mention is tire profile and I suspect a slight diameter difference that helps turn in as well.

 

[stig of the dump]

there is a lot of trash talked about tyres / handling on bikes everything interacts with everyhting else and its a deep subject what improves one aspect tends to have a detremental effect on another. FJr's for example are sensitve to the correct torque setting on the headstock bearings otherwise you get a judder ( be it only at a certain speed in certain conditions). and i pretty confident in saying the torque wrench being used is in-accurate every one i've checked over the last 50 years has been out. so a slight over tightening with my wrench cures the problem for me.

back to tyres and grip/life. the designer picked it out of what was avaliable at time of initial manufacture that works best with the rest of the factors afffecting handling and giving reasonable life. so in theory its improvable. A wider tyre slows rate of turn does it give any more grip? there isnt that much more rubber in contact with the ground.

so the question that should be asked is what effects grip and tyre life . the big factor here is heat some one will say softer rubber on the tyre or tyre construction etc but lets just say heat for now. a soft tyres generates more heat hence softer tyres for wet weather racing. more heat equals more wear.

tire choice and tyre pressue are critical factors tyre design moves forward so what was said by the designer origanally no longer holds water. different tyre manufacturers tyres may work better than others giving better feel and feedback adding that confidence in the wet but grip may not be radically changed.. tyre pressures are not going to necessarily be what was originally recommended so a bit of experimentation may be required to find the optimum, for that type of tyre. Oh and tyre pressure gauges are as in-accurate as the previously mentioned torque gauges, so use the same one all the time then at least your working to a constant error.

in conclussion dont bother more effort than its worth just experiment with different tyres standard size and pressure till you find one that gives reasonable grip and wear.