Thinking about a wider rear tire

[Calamari_imp]

"I'm finding the Michelin PR3 160 rear/110 front combination a pleasure to ride on. The Michelins have now done 900kms on all road types; highway, country road, straights and twisties, wet and dry. They work well both with a solo rider and a considerable load on the rack. I realise it is subjective of me but I am certain handling is better than the Dunlop 205s or Bridgestone BT45s I have used previously".

Now I'm considering a 160 as another option. Thanks for the info. Pterodactyl

[Riko_imp]

yeah, why "must" you have a 180 as such?

now you say 160 will do

But I understand you, I've been there. I have no bike but I am planning on buying a modern classic.
I've been long searching topics on the Triumph board for the Thruxton bike and the wider tire mods there.
I've seen everything, from 160 to 180 max.

Coming from a stock 130 rear tire a 160 is a great improvent for a bulkier look...because lets be honest, that is the main reason why one would do such a modification, at least, thats my reason.
A 130 rear tire just looked weird tbh on that nice bike.

Now I've returned to Honda, and I want a CB1100. More power and you can make that cb also very gorgeous. (although there are still much more after market parts for the Triumph modern classics)
And the CB also has a thinner tire than I would wish, a 140. So also here I would change that.

For the Thruxton as for the CB I originally wanted a 180 tire....than I look at my scooter tire (Burgman 650) and I thought, damn those tires are quite big for a scooter (they are 160 wide).
And when thinking about it, a 160 is certainly a big visual improvement over a 130 or a 140.
+ its not too radical and it will bring you less headaches in choosing the right wheels for those tires withouth any offset issues, so that makes 160 also a safer choice.

But its a fact, that you just cannot change the tire alone without at least contemplating about the right wheels...
Fortunatelly I found several nice companies that make nice spoked wheels that are not only nice but also are wider THUS allowing you to safely put on a wider than stock tire!

tire size as can be seen on the pic: 160/60
Kineo rim, assumably the only one available for the CB1100, a 4.25.


It give the rear a little bit more bulk, but nothing extreme or crazy as some call it here.

lets add some other pictures of these nice rims with the wider tire

[Calamari_imp]

I'm actually set on the 180 rear. The 160 option is info which I will pass on to friends of mine if they are interested in a wider rear but don't want to do a bunch of mods for a 180. I'm a function over form guy. Meaning it has to work good before it looks good. The 180 rear is form only, I like the look of a wider rear tire than what's currently on the bike. If in my research I find that I lose too much function (handling and rideability) from the mod, I won't do it plain and simple. I know that millions of dollars and tons of research are done to design and build a bike. I'm not naive enough to think I can do it better than the engineers that created the bike but I will look at every option at my disposal to get all the geometry, physics, etc as correct as possible. I do a ton of research before I make changes to anything.

[Riko_imp]

Also, when i was doing research about modding a Triumph Thruxton I found a cuss of pictures of guys with 160 tires - 170 rear and 180 rear.

And on picture its hard to say wich is wich if you dont know it at front. Skilled eyes can always tell the difference between a 160 and a 180 tire of course.

But as I said, a 160 tire will already give you that bulky look you are looking for

As far as function goes, why would a 180 rear tire be that much more better over stock than a 160 rear tire?
Both tires are already way over the stock recommend size of 140..
If you talk about handling, you can read stories here on this board from a few ppl that have a 160 tire, but no 180 stories her.
On the Thruxton board you will find a bunch of user reviews about the change in handling by putting on a wider tire...and I think that the general conclusion is when you do it correctly (choosing the right size, front tire size, diameter size, aspect ratio, etc. etc.) there are little negatives but certainly also benefits to getting a wider tire.

A small quote from the Thruxton board:

Quote:That hit the nail right on the head. Wider tires don't handle like crap, they just handle differently. Depending on how you ride, the difference in a wider tire can be an improvement or a step down.

Taking things a step at a time:

1) Cornering: From simple geometry, for the same lean angle, a wider rear tire moves the back tire's point of contact with the road further to the inside of the turn. That means, for the same lean angle, the line between the back and front contact points is turned more towards the outside of the turn. Therefore, it takes more lean angle, and more effort, to make the same radius turn at the same speed. But that's not necessarily all bad.

If you are a racer, of course that's a bad thing. But if you are a cruiser or daily road rider type; that extra effort can actually make the bike feel more stable in the turns. It may not actually be more stable, but it feels like it.If you ride near the bike's limit, it can give a false sense of security. But if you always leave lots of margin in cornering, and it feels better, it can be a plus. Be careful, but - cornering is a tie.

2) Appearance: Wider looks bitchin'. Wider is a clear winner.

3) Wear: A wider tire has more surface on the ground so the stress on the tread is less. So wider is better.

4) Dry Traction: Wider is a clear winner. Not only is there more rubber on the ground to grip the road, but, since wider tires wear better, the tire can have a softer tread for better grip while still having a reasonable life.

5) Rolling Resistance: The same factors that improve traction also work in the opposite direction and increase rolling resistance. Increased rolling resistance lowers gas mileage, lowers acceleration, and lowers top speed. Wider is worse.

6) Straight Line Stability: It would seem like a tie, but real roads aren't flat. On a cambered road, the contact patch shifts to the "uphill" side of the road and tends to drive the bike "downhill". A wider tire amplifies this effect and makes the bike more sensitive to the road. Wider is worse.

7) Wet Traction: A wider tire has to pump water a greater distance to keep the contact patch dry and is more likely to hydroplane. Wider is worse.

8) Weight: Wider tires are heavier. More weight costs in mileage and acceleration. The additional weight is also unsprung weight, so it makes road holding worse. Wider is worse.

So there's at least some of the factors to consider when choosing a tire size. I apologize in advance to those who complain about my use of "mechanical physics".
Rest of discussion can be found here: http://www.triumphrat.net/twins-technica...yre-3.html

ps: you can always use this practical tool to compare the stock set up in size with the new tires and wheels:
http://www.tacomaworld.com/forum/tirecalc.php

[Houtman_imp]

That was informative, thank you .
I will only go up one size on the rear, from 140 to 150 .
I do know that in the same size different companies still have different measurements on the tire.

[Riko_imp]

here in Belgium we got this website where you can do a custom search, and a certain make and type of tyre has different sizes...I am sure you will also find something similar close to your home.

I must say, last time I did a search, I thought 150 is not a popular size, its mostly 140-160-180, dunno about 170.
I could be wrong of course, but you will have to do a search type by type.

[Pterodactyl_imp]

I'm actually set on the 180 rear. The 160 option is info which I will pass on to friends of mine if they are interested in a wider rear but don't want to do a bunch of mods for a 180. I'm a function over form guy. Meaning it has to work good before it looks good. The 180 rear is form only, I like the look of a wider rear tire than what's currently on the bike. If in my research I find that I lose too much function (handling and rideability) from the mod, I won't do it plain and simple. I know that millions of dollars and tons of research are done to design and build a bike. I'm not naive enough to think I can do it better than the engineers that created the bike but I will look at every option at my disposal to get all the geometry, physics, etc as correct as possible. I do a ton of research before I make changes to anything.

Good observation. Naive? I'm not sure. I would have to say that, firstly, the aim of the designers would have to be taken into consideration. For instance, would I modify tyres or other key control components on a top end supersports? If I had expertise in racing mods maybe, but in reality no. Why? Because the designers did put considerable effort and specialist knowledge into that area - probably right to the limits. The CB was designed with another aim. A modern classic for blokes like us to buy. The geometry and physics were quite clearly subordinated to fulfil the design criteria of a modestly, but adequately, performing modern classic. Every performance enhancing area on this bike has room for improvement. Suspension, wheels, tyres, engine. They are all up for grabs if you care to go down that path. I don't. But those that do, if they proceed with caution, research (as you say so well) and a modicum of experience can change the entire character of the bike.

Cheers

[ingobohn_imp]

I'm actually set on the 180 rear. The 160 option is info which I will pass on to friends of mine if they are interested in a wider rear but don't want to do a bunch of mods for a 180. I'm a function over form guy. Meaning it has to work good before it looks good. The 180 rear is form only, I like the look of a wider rear tire than what's currently on the bike. If in my research I find that I lose too much function (handling and rideability) from the mod, I won't do it plain and simple. I know that millions of dollars and tons of research are done to design and build a bike. I'm not naive enough to think I can do it better than the engineers that created the bike but I will look at every option at my disposal to get all the geometry, physics, etc as correct as possible. I do a ton of research before I make changes to anything.

I have a question, maybe a stupid one...
With such a wide 180 rear tire - is there no problem with the center stand? Does the tire not collide with it?

[Pterodactyl_imp]

I'm actually set on the 180 rear. The 160 option is info which I will pass on to friends of mine if they are interested in a wider rear but don't want to do a bunch of mods for a 180. I'm a function over form guy. Meaning it has to work good before it looks good. The 180 rear is form only, I like the look of a wider rear tire than what's currently on the bike. If in my research I find that I lose too much function (handling and rideability) from the mod, I won't do it plain and simple. I know that millions of dollars and tons of research are done to design and build a bike. I'm not naive enough to think I can do it better than the engineers that created the bike but I will look at every option at my disposal to get all the geometry, physics, etc as correct as possible. I do a ton of research before I make changes to anything.

I have a question, maybe a stupid one...
With such a wide 180 rear tire - is there no problem with the center stand? Does the tire not collide with it?

I have a question, maybe a stupid one...
With such a wide 180 rear tire - is there no problem with the center stand? Does the tire not collide with it?
With a 160 I had 7mm clearance from the right side of the centre stand. The standard clearance was 12mm. I modified the stand and clearance is now 15mm. I'm happy. The 180 tyre would have the same, and perhaps more, issues with clearance.
See: http://cb1100forum.com/forum/showthread.php?tid=3466

Cheers

By the way, no such thing as a silly question. Silly answers? Yes.

[Calamari_imp]

I found a couple manufacturers that have a 180/55-18 tire. Using an online comparison tool, I found that this size is almost the same diameter as the factory 140 tire. Finding a 5.5 inch rim and making it all fit is next. The spoke wheels may be an option. I've seen many times where a wider wheel hoop was laced onto an original hub so a wider tire could be run. I personally like the non spoke wheels that come on the CB.

The center stand may pose a problem like you mentioned. Once I get a tire I'll start working thru the details.